Bulletin No. 2025–41

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HIGHLIGHTS

OF THIS ISSUE

Bulletin No. 2025–41

October 6, 2025

These synopses are intended only as aids to the reader in

identifying the subject matter covered. They may not be

relied upon as authoritative interpretations.

ADMINISTRATIVE, INCOME TAX

INCOME TAX

Notice 2025-54, page 479.

Notice 2025-52, page 474.

Optional special per diem rates. This notice provides the

2025-2026 special per diem rates for taxpayers to use in

substantiating the amount of ordinary and necessary business

expenses incurred while traveling away from home. The notice

includes (1) the special transportation industry rate, (2) the

rate for the incidental expenses only deduction, and (3) the

rates and list of high-cost localities for the high-low substantiation method.

EXCISE TAX

Notice 2025-51, page 448.

This Notice of Determinations adds 39 chemical substances

to the list of taxable substances under § 4672 subject to the

tax imposed by § 4671.

Finding Lists begin on page ii.

This notice explains the circumstances under which the fouryear replacement period under section 1033(e)(2) is extended

for livestock sold on account of drought. The Appendix to this

notice contains a list of counties that experienced exceptional,

extreme, or severe drought conditions during the 12-month

period ending August 31, 2025. Taxpayers may use this list to

determine if any extension is available.

Rev. Rul. 2025-19, page 445.

Federal rates; adjusted federal rates; adjusted federal longterm rate, and the long-term tax exempt rate. For purposes of

sections 382, 1274, 1288, 7872 and other sections of the

Code, tables set forth the rates for October 2025.

Rev. Rul. 2025-20, page 447.

Fringe benefits aircraft valuation formula. For purposes of section 1.61-21(g) of the Income Tax Regulations, relating to the

rule for valuing non-commercial flights on employer-provided

aircraft, the Standard Industry Fare Level (SIFL) cents-per-mile

rates and terminal charge in effect for the second half of 2025

are set forth.

The IRS Mission

Provide America’s taxpayers top-quality service by helping

them understand and meet their tax responsibilities and

enforce the law with integrity and fairness to all.

Introduction

The Internal Revenue Bulletin is the authoritative instrument

of the Commissioner of Internal Revenue for announcing official rulings and procedures of the Internal Revenue Service

and for publishing Treasury Decisions, Executive Orders, Tax

Conventions, legislation, court decisions, and other items of

general interest. It is published weekly.

It is the policy of the Service to publish in the Bulletin all substantive rulings necessary to promote a uniform application

of the tax laws, including all rulings that supersede, revoke,

modify, or amend any of those previously published in the

Bulletin. All published rulings apply retroactively unless otherwise indicated. Procedures relating solely to matters of internal management are not published; however, statements of

internal practices and procedures that affect the rights and

duties of taxpayers are published.

Revenue rulings represent the conclusions of the Service

on the application of the law to the pivotal facts stated in

the revenue ruling. In those based on positions taken in rulings to taxpayers or technical advice to Service field offices,

identifying details and information of a confidential nature are

deleted to prevent unwarranted invasions of privacy and to

comply with statutory requirements.

Rulings and procedures reported in the Bulletin do not have the

force and effect of Treasury Department Regulations, but they

may be used as precedents. Unpublished rulings will not be

relied on, used, or cited as precedents by Service personnel in

the disposition of other cases. In applying published rulings and

procedures, the effect of subsequent legislation, regulations,

court decisions, rulings, and procedures must be considered,

and Service personnel and others concerned are cautioned

against reaching the same conclusions in other cases unless

the facts and circumstances are substantially the same.

The Bulletin is divided into four parts as follows:

Part I.—1986 Code.

This part includes rulings and decisions based on provisions

of the Internal Revenue Code of 1986.

Part II.—Treaties and Tax Legislation.

This part is divided into two subparts as follows: Subpart A,

Tax Conventions and Other Related Items, and Subpart B,

Legislation and Related Committee Reports.

Part III.—Administrative, Procedural, and Miscellaneous.

To the extent practicable, pertinent cross references to these

subjects are contained in the other Parts and Subparts. Also

included in this part are Bank Secrecy Act Administrative

Rulings. Bank Secrecy Act Administrative Rulings are issued

by the Department of the Treasury’s Office of the Assistant

Secretary (Enforcement).

Part IV.—Items of General Interest.

This part includes notices of proposed rulemakings, disbarment and suspension lists, and announcements.

The last Bulletin for each month includes a cumulative index

for the matters published during the preceding months. These

monthly indexes are cumulated on a semiannual basis, and are

published in the last Bulletin of each semiannual period.

The contents of this publication are not copyrighted and may be reprinted freely. A citation of the Internal Revenue Bulletin as the source would be appropriate.

October 6, 2025

Bulletin No. 2025–41

Part I

Section 1274.—

Determination of Issue

Price in the Case of Certain

Debt Instruments Issued for

Property

(Also Sections 42, 280G, 382, 467, 468, 482, 483,

1288, 7520, 7872.)

Rev. Rul. 2025-19

This revenue ruling provides various prescribed rates for federal income

Annual

AFR

110% AFR

120% AFR

130% AFR

3.81%

4.19%

4.57%

4.96%

AFR

110% AFR

120% AFR

130% AFR

150% AFR

175% AFR

3.87%

4.25%

4.65%

5.04%

5.83%

6.81%

AFR

110% AFR

120% AFR

130% AFR

4.73%

5.22%

5.70%

6.17%

Short-term adjusted AFR

Mid-term adjusted AFR

Long-term adjusted AFR

Bulletin No. 2025–41

tax purposes for October 2025 (the

current month). Table 1 contains the

short-term, mid-term, and long-term

applicable federal rates (AFR) for the

current month for purposes of section

1274(d) of the Internal Revenue Code.

Table 2 contains the short-term, midterm, and long-term adjusted applicable federal rates (adjusted AFR) for the

current month for purposes of section

1288(b). Table 3 sets forth the adjusted

federal long-term rate and the longterm tax-exempt rate described in section 382(f). Table 4 contains the appro-

priate percentages for determining the

low-income housing credit described in

section 42(b)(1) for buildings placed in

service during the current month. However, under section 42(b)(2), the applicable percentage for non-federally subsidized new buildings placed in service

after July 30, 2008, shall not be less

than 9%. Finally, Table 5 contains the

federal rate for determining the present

value of an annuity, an interest for life

or for a term of years, or a remainder or

a reversionary interest for purposes of

section 7520.

REV. RUL. 2025-19 TABLE 1

Applicable Federal Rates (AFR) for October 2025

Period for Compounding

Semiannual

Quarterly

Short-term

3.77%

3.75%

4.15%

4.13%

4.52%

4.49%

4.90%

4.87%

Mid-term

3.83%

3.81%

4.21%

4.19%

4.60%

4.57%

4.98%

4.95%

5.75%

5.71%

6.70%

6.64%

Long-term

4.68%

4.65%

5.15%

5.12%

5.62%

5.58%

6.08%

6.03%

Annual

2.88%

2.93%

3.58%

REV. RUL. 2025-19 TABLE 2

Adjusted AFR for October 2025

Period for Compounding

Semiannual

2.86%

2.91%

3.55%

445

Quarterly

2.85%

2.90%

3.53%

Monthly

3.74%

4.11%

4.48%

4.85%

3.80%

4.17%

4.56%

4.93%

5.68%

6.61%

4.64%

5.10%

5.56%

6.00%

Monthly

2.84%

2.89%

3.52%

October 6, 2025

REV. RUL. 2025-19 TABLE 3

Rates Under Section 382 for October 2025

Adjusted federal long-term rate for the current month

Long-term tax-exempt rate for ownership changes during the current month (the highest of the adjusted federal

long-term rates for the current month and the prior two months.)

3.58%

3.65%

REV. RUL. 2025-19 TABLE 4

Appropriate Percentages Under Section 42(b)(1) for October 2025

Note: Under section 42(b)(2), the applicable percentage for non-federally subsidized new buildings placed in service after

July 30, 2008, shall not be less than 9%.

Appropriate percentage for the 70% present value low-income housing credit

8.00%

Appropriate percentage for the 30% present value low-income housing credit

3.43%

REV. RUL. 2025-19 TABLE 5

Rate Under Section 7520 for October 2025

Applicable federal rate for determining the present value of an annuity, an interest for life or a term of years,

or a remainder or reversionary interest

Section 42.—Low-Income

Housing Credit

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19, page 445.

Section 280G.—Golden

Parachute Payments

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19 page 445.

Section 382.—Limitation

on Net Operating Loss

Carryforwards and

Certain Built-In Losses

Following Ownership

Change

The adjusted applicable federal long-term rate

is set forth for the month of October 2025. See Rev.

Rul. 2025-19, page 445.

Section 467.—Certain

Payments for the Use of

Property or Services

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19, page 445.

Section 468.—Special

Rules for Mining and Solid

Waste Reclamation and

Closing Costs

The applicable federal short-term rates are set

forth for the month of October 2025. See Rev. Rul.

2025-19, page 445.

Section 482.—Allocation

of Income and Deductions

Among Taxpayers

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19, page 445.

4.6%

Section 483.—Interest on

Certain Deferred Payments

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19, page 445.

Section 1288.—Treatment

of Original Issue Discount

on Tax-Exempt Obligations

The adjusted applicable federal short-term, midterm, and long-term rates are set forth for the month

of October 2025. See Rev. Rul. 2025-19, page 445.

Section 7520.—Valuation

Tables

The applicable federal mid-term rates are set

forth for the month of October 2025. See Rev. Rul.

2025-19, page 445.

Section 7872.—Treatment

of Loans With BelowMarket Interest Rates

The applicable federal short-term, mid-term,

and long-term rates are set forth for the month of

October 2025. See Rev. Rul. 2025-19, page 445.

October 6, 2025

446

Bulletin No. 2025–41

Section 61. Gross Income

Defined

26 CFR 1.61-21: Taxation of Fringe Benefits

Rev. Rul. 2025-20

For purposes of the taxation of fringe

benefits under section 61 of the Internal

Revenue Code, section 1.61-21(g) of

the Income Tax Regulations provides a

rule for valuing noncommercial flights

on employer-provided aircraft. Section

1.61-21(g)(5) provides an aircraft valuation formula to determine the value

of such flights. The value of a flight is

determined under the base aircraft valuation formula (also known as the Standard

Industry Fare Level formula or SIFL)

by multiplying the SIFL cents-per-mile

Period During Which the Flight Is Taken

Terminal Charge

rates applicable for the period during

which the flight was taken by the appropriate aircraft multiple provided in section 1.61-21(g)(7) and then adding the

applicable terminal charge. The SIFL

cents-per-mile rates in the formula and

the terminal charge are calculated by the

Department of Transportation (DOT) and

are reviewed semi-annually.

The following chart sets forth the terminal charge and SIFL mileage rates:

SIFL Mileage Rates

7/1/25 - 12/31/25

$53.62

Up to 500 miles

= $.2933 per mile

501-1500 miles

= $.2237 per mile

Over 1500 miles

= $.2150 per mile

DRAFTING INFORMATION

The principal author of this revenue ruling is Kathleen Edmondson of the Office

Bulletin No. 2025–41

of Associate Chief Counsel (Employee

Benefits, Exempt Organizations and

Employment Taxes). For further information regarding this revenue ruling, contact

447

Ms. Edmondson at (202) 317-6798 (not a

toll-free number).

October 6, 2025

Part III

Superfund Tax on Chemical

Substances; Notice of

Determinations to Add

Substances to List of

Taxable Substances

Notice 2025-51

SUMMARY: This notice of determinations modifies the list of taxable substances to include the following 39 substances: acrylonitrile-butadiene rubber

((C4H6)n-(C3H3N)m; n=13.44, m=25.54),

bromo-isobutene-isoprene rubber ((C4H8)

-(C5H7.5Br0.5)m;

n=98.20,

m=1.80),

chloroprene rubber, ethylene-propylene-ethylidene norbornene rubber ((C2H4)

-(C3H6)n(C9H12)o; m=56.82, n=40.46,

o=2.71), ethylene vinyl acetate (VA < 50%)

((C2H4)n-(C4H6O2)m; n=78.95, m=21.05),

ethylene vinyl acetate (VA ≥ 50%) ((C2H4)

-(C4H6O2)m; n=75.42, m=24.58), hydron

genated acrylonitrile-butadiene rubber

((C4H8)n-(C3H3N)m; n=22.28, m= 38.86),

isobutene-isoprene rubber ((C4H8)n-(C5H8)

; n=99.10, m=0.90), poly(ethylene-prom

pylene) rubber ((C2H4)m-(C3H6)n; m=59.04,

n=40.96), emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83, n=2.53),

solution styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=67.16, n=32.85), emulsion

styrene butadiene rubber ((C4H6)m-(C8H8)

; m=14.14, n=2.26), solution styrene-bun

tadiene rubber ((C4H6)m-(C8H8)n; m=13.31,

n=2.50), hydrogenated acrylonitrile-butadiene rubber ((C4H8)x-(C3H3N)y-(C15H24O)

; x=2,783.05, y=1,907.27, a=5.74), broa

mobutyl isobutylene isoprene rubber

((C4H8)x(C5H8)y(Br2)z; x=7071, y=59,

z=50), chlorobutyl isobutylene isoprene

rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036,

y=88, z=70), DIPE–di-isopropyl ether,

di-isodecyl phthalate, di-isononyl adipate,

di-isononyl phthalate, di-tridecyl phthalate,

ethylene propylene diene (EPDM) rubber

((C2H4)x(C3H6)y(C9H12)z; x=5134, y=2250,

z=98), isodecyl alcohol, isodecyl benzoate,

isooctyl alcohol, linear nonyl phthalate, linear nonyl undecyl phthalate, linear undecyl

phthalate, linear nonyl tri-mellitate, neo

decanoic acid, neo pentanoic acid, nonene, regular butyl rubber ((C4H8)x(C5H8)

October 6, 2025

; x=7036, y=88), tridecyl alcohol, triisononyl tri-mellitate, di-isobutylene, polyisobutylene, styrene-acrylonitrile ((C3H3N)

-(C8H8)s; a=0.26, s=0.74), and acrylonia

trile butadiene styrene ((C3H3N)a-(C4H6)

-(C8H8)s; a=0.16, b=0.10, s=0.74),

EFFECTIVE DATES: The effective date

for purposes of the tax under section 4671

of the Internal Revenue Code (Code) for

the taxable substances added to the list is

January 1, 2026. For the effective date for

purposes of refund claims under section

4662(e) of the Code for the taxable substances added to the list, see the determination for each substance.

FOR FURTHER INFORMATION

CONTACT: Andrew Clark or Jacob

Peeples at (202) 317-6855 (not a toll-free

number).

SUPPLEMENTARY INFORMATION:

Background

Section 4671(a) of the Code imposes

an excise tax on the sale or use of a taxable

substance by the importer thereof (section

4671 tax). Section 4672(a)(1) of the Code

defines the term taxable substance as any

substance which, at the time of sale or use

by the importer, is listed as a taxable substance by the Secretary of the Treasury or

the Secretary’s delegate (Secretary) on the

list of taxable substances under section

4672(a) (List).

Under section 4672(a)(2), an importer

or exporter of any substance may request

that the Secretary determine whether such

substance should be added to the List as

a taxable substance or should be removed

from the List. Under section 4672(a)(2)

(B) and (a)(4) and (b)(2), the Secretary

is required to add a substance to the List

if the Secretary determines that any taxable chemicals that are listed in section

4661(b) of the Code constitute more than

20 percent of the weight, or more than

20 percent of the value, of the materials

used to produce such substance, which

determination is required under section

4672(a)(2)(B) and (a)(4) to be made based

on the predominant method of production

448

(weight or value test). Section 4672(a)(4)

authorizes the Secretary to remove a substance from the List only if such substance

meets neither the weight nor the value test

of section 4672(a)(2)(B).

Section 4672(a)(3) includes an initial

list of taxable substances. Section 4 of

Notice 2021-66 (2021-52 I.R.B. 901) provides the list of 101 substances that the

Secretary added to the List before November 15, 2021. On May 31, 2024, the Secretary published a Notice of Determination

in the Federal Register (89 FR 47238)

adding polyoxymethylene to the List;

this Notice of Determination was also

published in the Internal Revenue Bulletin as Notice 2024-50 (2024-26 I.R.B.

1789). On August 4, 2025, the Secretary

published a Notice of Determinations in

the Federal Register (90 FR 36520) adding 21 substances to the List; this Notice

of Determinations was also published in

the Internal Revenue Bulletin as Notice

2025-41 (2025-34 I.R.B. 325). Rev. Proc.

2022-26 (2022-29 I.R.B. 90), as modified

by Rev. Proc. 2023-20 (2023-15 I.R.B.

636), provides the exclusive procedures

by which an importer, exporter, or interested person may request a determination

that a particular substance be added to or

removed from the List.

Section 4671(b)(3) authorizes the Secretary to prescribe a tax rate for taxable substances in lieu of the tax rate specified in

section 4671(b)(2). The tax rate prescribed

by the Secretary for a substance added to

the List is calculated by multiplying the

conversion factor for each taxable chemical used in the production of the substance

by the corresponding tax rate for that taxable chemical under section 4661(b), and

adding those results together. Conversion

factors are determined based on the predominant method of production of the substance. See sections 8 and 10.04(8) of Rev.

Proc. 2022-26. Importers are not required

to use the prescribed tax rate for a taxable

substance and may calculate their own rate

under section 4671(b)(1).

Pursuant to Section 4672(a)(4), this

notice of determinations modifies the List

to include the 39 additional taxable substances listed in the Summary of Determinations section of this notice, as explained

Bulletin No. 2025–41

in the Requests to Add Substances to the

List and General Explanation of Determinations sections of this notice. The determination for each specific substance added

to the List is explained in parts 1 through

39 of the Modifications to the List of Taxable Substances section of this notice.

The updated List and prescribed

tax rates for taxable substances will be

included in the instructions to Form 6627,

Environmental Taxes.

Summary of Determinations

On September 15, 2025, the Secretary

determined to add the following substances to the List:

1. Acrylonitrile-butadiene rubber ((C4H6)

-(C3H3N)m; n=13.44, m=25.54)

2. Bromo-isobutene-isoprene

rubber

((C4H8)n-(C5H7.5Br0.5)m;

n=98.20,

m=1.80)

3. Chloroprene rubber

4. Ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)

(C9H12)o; m=56.82, n=40.46, o=2.71)

5. Ethylene vinyl acetate (VA < 50%)

((C2H4)n-(C4H6O2)m;

n=78.95,

m=21.05)

6. Ethylene vinyl acetate (VA ≥ 50%)

((C2H4)n-(C4H6O2)m;

n=75.42,

m=24.58)

7. Hydrogenated acrylonitrile-butadiene

rubber ((C4H8)n-(C3H3N)m; n=22.28,

m= 38.86)

8. Isobutene-isoprene rubber ((C4H8)

-(C5H8)m; n=99.10, m=0.90)

9. Poly(ethylene-propylene)

rubber

((C2H4)m-(C3H6)n; m=59.04, n=40.96)

10. Emulsion styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=15.83, n=2.53)

11. Solution styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=67.16, n=32.85)

12. Emulsion styrene butadiene rubber

((C4H6)m-(C8H8)n; m=14.14, n=2.26)

13. Solution styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=13.31, n=2.50)

14. Hydrogenated acrylonitrile-butadiene

rubber ((C4H8)x-(C3H3N)y-(C15H24O)a;

x=2,783.05, y=1,907.27, a=5.74)

15. Bromobutyl isobutylene isoprene

rubber ((C4H8)x(C5H8)y(Br2)z; x=7071,

y=59, z=50)

16. Chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036,

y=88, z=70)

17. DIPE–di-isopropyl ether

Bulletin No. 2025–41

18. Di-isodecyl phthalate

19. Di-isononyl adipate

20. Di-isononyl phthalate

21. Di-tridecyl phthalate

22. Ethylene propylene diene (EPDM)

rubber

((C2H4)x(C3H6)y(C9H12)z;

x=5134, y=2250, z=98)

23. Isodecyl alcohol

24. Isodecyl benzoate

25. Isooctyl alcohol

26. Linear nonyl phthalate

27. Linear nonyl undecyl phthalate

28. Linear undecyl phthalate

29. Linear nonyl tri-mellitate

30. Neo decanoic acid

31. Neo pentanoic acid

32. Nonene

33. Regular butyl rubber ((C4H8)x(C5H8)y;

x=7036, y=88)

34. Tridecyl alcohol

35. Tri-isononyl tri-mellitate

36. Di-isobutylene

37. Polyisobutylene

38. Styrene-acrylonitrile

((C3H3N)

-(C

)

;

a=0.26,

s=0.74)

8 8 s

39. Acrylonitrile

butadiene

styrene

((C3H3N)a-(C4H6)b-(C8H8)s; a=0.16,

b=0.10, s=0.74)

Requests to Add Substances to the List

For each of the substances listed in

the Summary of Determinations section

of this notice, an importer or an exporter

submitted a petition to the IRS in accordance with Rev. Proc. 2022-26 requesting

a determination under section 4672(a)(2)

to add the substance to the List. For each

substance, the petition represented that

taxable chemicals constitute more than 20

percent of the weight of materials used to

produce the substance, based on the predominant method of production.

General Explanation of Determinations

After reviewing the petitions for each

of the substances listed in the Summary of

Determinations section of this notice, the

Secretary determined that taxable chemicals constitute more than 20 percent by

weight of the materials used to produce

the substance, based on the predominant

method of production. Therefore, each

of the substances is added to the List as

required under section 4672(a)(2) and (4).

The Secretary made the determinations to

449

add these substances to the List in accordance with the requirements of section

4672(a)(2) and (4), and pursuant to the

procedures set forth in Rev. Proc. 202226, as modified by Rev. Proc. 2023-20.

The relevant information for each taxable substance is provided in the specific

determinations included in parts 1 through

39 of the Modifications to the List of Taxable Substances section of this notice.

The tax rate for each taxable substance, as

prescribed by the Secretary, is provided in

paragraph (a)(6) of each specific determination. All scientific information provided

in the specific determinations reflects

the information provided by petitioners

as published in each taxable substance’s

respective Notice of Filing.

Classification numbers proposed by

each petitioner are included in paragraph

(b) of each part, after each specific determination. The classification numbers

provided with respect to a taxable substance are not part of the determination

of whether it is added to the List and do

not impact whether such substance is a

taxable substance. Taxpayers may not rely

on classification numbers for any purpose

under sections 4661, 4662, 4671, and

4672, including (but not limited to) identification of a substance as a taxable substance on the List. Classification numbers

may change over time. The Department of

the Treasury (Treasury Department) and

the IRS do not anticipate updating this

document to reflect any such changes.

For purposes of the section 4671 tax,

all the modifications in parts 1 through 39

of the Modifications to the List of Taxable Substances section of this notice are

effective on and after January 1, 2026. For

purposes of refund claims under section

4662(e), see the effective date for each

specific determination in paragraph (a)(5)

(ii) of each of parts 1 through 39 of the

Modifications to the List of Taxable Substances section of this notice.

Modifications to the List of Taxable

Substances

1. Determination to Add Acrylonitrilebutadiene Rubber ((C4H6)n-(C3H3N)m;

n=13.44, m=25.54) to the List

Arlanxeo USA LLC and Arlanxeo Canada Inc., importers and exporters of acrylo-

October 6, 2025

nitrile-butadiene rubber ((C4H6)n-(C3H3N)m;

n=13.44, m=25.54), submitted a petition in

accordance with Rev. Proc. 2022-26 requesting to add acrylonitrile-butadiene rubber

((C4H6)n-(C3H3N)m; n=13.44, m=25.54) to

the List. According to the petition, the taxable chemicals butadiene, propylene, and

ammonia constitute 64.59 percent by weight

of the materials used to produce acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m;

n=13.44, m=25.54), based on the predominant method of production.

(a) Determination. Acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m; n=13.44,

m=25.54) is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

acrylonitrile-butadiene rubber is through

a radical polymerization of acrylonitrile

and butadiene in an emulsion process.

Acrylonitrile monomer is produced by the

SOHIO process (i.e., catalytic ammoxidation of propylene).

(2) Stoichiometric material consumption equation:

n C4H6 (butadiene) + m [C3H6 (propylene) + NH3 (ammonia) + 3/2 O2] →

(C4H6)n-(C3H3N)m (acrylonitrile-butadiene rubber) + 3m H2O

(3) Reasons for the determination: The

acrylonitrile-butadiene rubber ((C4H6)

-(C3H3N)m; n=13.44, m=25.54) petition

was filed on February 7, 2025. The notice

of filing summarizing the petition and

requesting comments was published in the

Federal Register (90 FR 14684) on April

3, 2025. The Treasury Department and

the IRS received no written comments in

response to the notice of filing. A public

hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals butadiene, propylene, and ammonia constitute more than

20 percent by weight of the materials used

in the production of acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)m; n=13.44,

m=25.54), based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

October 6, 2025

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of acrylonitrile-butadiene rubber ((C4H6)n-(C3H3N)

; n=13.44, m=25.54) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.58 per ton. The conversion factors

for the taxable chemicals used in the production of acrylonitrile-butadiene rubber

((C4H6)n-(C3H3N)m; n=13.44, m=25.54)

are 0.35 for butadiene, 0.52 for propylene,

and 0.21 for ammonia. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical

by the tax rate for that taxable chemical:

((0.35 x $9.74) + (0.52 x $9.74) + (0.21 x

$5.28) = $9.58).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.59.0000

(ii) Schedule B number: 4002.59.0000

(iii) CAS number: 9003-18-3

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

2. Determination to Add Bromoisobutene-isoprene Rubber ((C4H8)

-(C5H7.5Br0.5)m; n=98.20, m=1.80) to the

List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters of

bromo-isobutene-isoprene rubber ((C4H8)

-(C5H7.5Br0.5)m; n=98.20, m=1.80), subn

mitted a petition in accordance with Rev.

Proc. 2022-26 requesting to add bromo-isobutene-isoprene rubber ((C4H8)

-(C5H7.5Br0.5)m; n=98.20, m=1.80) to

the List. According to the petition, the

taxable chemicals butylene, bromine,

and sodium hydroxide constitute 97.89

percent by weight of the materials used

to produce bromo-isobutene-isoprene

rubber ((C4H8)n-(C5H7.5Br0.5)m; n=98.20,

m=1.80), based on the predominant

method of production.

450

(a) Determination. Bromo-isobutene-isoprene rubber ((C4H8)n-(C5H7.5Br0.5)

; n=98.20, m=1.80) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

bromo-isobutene-isoprene rubber involves

reacting a hexane solution of butyl rubber

with elemental bromine. Butyl rubber is

produced via the cationic copolymerization of butylene with isoprene in the presence of a Friedel-Crafts catalyst at low

temperature, around -100°C.

(2) Stoichiometric material consumption equation:

n C4H8 (butylene) + m C5H8 (isoprene) + m/2 Br2 (bromine) + m/2

NaOH (sodium hydroxide) → (C4H8)

(C5H7.5Br0.5)m (bromo-isobutene-ison

prene rubber) + m/2 NaBr + m/2 H2O

(3) Reasons for the determination: The

bromo-isobutene-isoprene rubber ((C4H8)

-(C5H7.5Br0.5)m; n=98.20, m=1.80) petin

tion was filed on February 7, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 14694) on

April 3, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process in

section 4672(a)(2)(B) in making this determination. A review of the stoichiometric

material consumption equation and other

information in the petition shows that the

taxable chemicals butylene, bromine, and

sodium hydroxide constitute more than

20 percent by weight of the materials

used in the production of bromo-isobutene-isoprene rubber ((C4H8)n-(C5H7.5Br0.5)

; n=98.20, m=1.80), based on the predomm

inant method of production. Therefore, the

test in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of bromo-isobutene-isoprene rubber ((C4H8)

-(C5H7.5Br0.5)m; n=98.20, m=1.80) to

the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

Bulletin No. 2025–41

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): April 1, 2023

(6) Tax rate prescribed by the Secretary: $9.72 per ton. The conversion factors for the taxable chemicals used in the

production of bromo-isobutene-isoprene

rubber ((C4H8)n-(C5H7.5Br0.5)m; n=98.20,

m=1.80) are 0.97 for butylene, 0.03 for

bromine, and 0.01 for sodium hydroxide.

The tax rate is calculated by adding the

products of the conversion factor for each

taxable chemical by the tax rate for that

taxable chemical: ((0.97 x $9.74) + (0.03

x $8.90) + (0.01 x $0.56) = $9.72).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.39.0000

(ii) Schedule B number: 4002.39.0000

(iii) CAS number: 68441-14-5

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

3. Determination to Add Chloroprene

Rubber to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters of

chloroprene rubber, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add chloroprene rubber to

the List. According to the petition, the taxable chemicals butadiene, chlorine, and

sodium hydroxide constitute 100 percent

by weight of the materials used to produce

chloroprene rubber, based on the predominant method of production.

(a) Determination. Chloroprene rubber

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of producing

chloroprene rubber is through polymerization of chloroprene initiated by a radical

initiator in an emulsion process. Chloroprene monomer is made from butadiene

by first reacting it with chlorine in the gas

phase at ca 500 K to form 3,4-dichlorobut-1-ene and 1,4-dichlorobut-2-ene. The

former, on reaction with sodium hydroxide, yields chloroprene monomer.

Bulletin No. 2025–41

(2) Stoichiometric material consumption equation:

n [C4H6 (butadiene) + Cl2 (chlorine)

+ NaOH (sodium hydroxide)] →

(C4H5Cl)n (chloroprene rubber) + n

NaCl + n H2O

(3) Reasons for the determination:

The chloroprene rubber petition was filed

on February 7, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals butadiene, chlorine, and sodium hydroxide constitute more than 20 percent by weight of

the materials used in the production of

chloroprene rubber, based on the predominant method of production. Therefore, the test in section 4672(a)(2)(B) is

satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of chloroprene rubber to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary:

$10.51 per ton. The conversion factors for

the taxable chemicals used in the production

of chloroprene rubber are 0.61 for butadiene, 0.80 for chlorine, and 0.45 for sodium

hydroxide. The tax rate is calculated by

adding the products of the conversion factor for each taxable chemical by the tax rate

for that taxable chemical: ((0.61 x $9.74) +

(0.80 x $5.40) + (0.45 x $0.56) = $10.51).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

451

(i) HTSUS number: 4002.49.0000

(ii) Schedule B number: 4002.49.0000

(iii) CAS number: 9010-98-4

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 4002.99.0000

(ii) Schedule B number: 4002.99.0000

4. Determination to Add Ethylenepropylene-ethylidene Norbornene

Rubber ((C2H4)m-(C3H6)n(C9H12)o;

m=56.82, n=40.46, o=2.71) to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters

of ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)

; m=56.82, n=40.46, o=2.71), submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add ethylene-propylene-ethylidene norbornene rubber ((C2H4)

-(C3H6)n(C9H12)o; m=56.82, n=40.46,

o=2.71) to the List. According to the petition, the taxable chemicals ethylene, propylene, and butadiene constitute 95.05

percent by weight of the materials used

to produce ethylene-propylene-ethylidene

norbornene rubber ((C2H4)m-(C3H6)n(C9H12)

; m=56.82, n=40.46, o=2.71), based on the

predominant method of production.

(a) Determination. Ethylene-propylene-ethylidene norbornene rubber ((C2H4)

-(C3H6)n(C9H12)o; m=56.82, n=40.46,

o=2.71) is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing ethylene-propylene-ethylidene norbornene

rubber is through the catalytic polymerization of ethylene, propylene, and nonconjugated diene monomers in a solution

using various catalysts. Non-conjugated

diene monomers include ethylidene norbornene and dicyclopentadiene. The nonconjugated diene monomers are produced

from cyclopentadiene and butadiene, and

cyclopentadiene, respectively.

(2) Stoichiometric material consumption equation:

m C2H4 (ethylene) + n C3H6 (propylene) + o [C5H6 (cyclopentadiene) + C4H6 (butadiene)] → (C2H4)

-(C3H6)n(C9H12)o (ethylene-propylm

ene-ethylidene norbornene rubber)

October 6, 2025

(3) Reasons for the determination:

The ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)

; m=56.82, n=40.46, o=2.71) petition

was filed on February 7, 2025. The notice

of filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 14695) on

April 3, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals ethylene, propylene, and butadiene constitute more

than 20 percent by weight of the materials

used in the production of ethylene-propylene-ethylidene norbornene rubber ((C2H4)

-(C3H6)n(C9H12)o; m=56.82, n=40.46,

o=2.71), based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

ethylene-propylene-ethylidene

norbornene rubber ((C2H4)m-(C3H6)n(C9H12)

; m=56.82, n=40.46, o=2.71) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): April 1, 2023

(6) Tax rate prescribed by the Secretary:

$9.25 per ton. The conversion factors for

the taxable chemicals used in the production of ethylene-propylene-ethylidene norbornene rubber ((C2H4)m-(C3H6)n(C9H12)

; m=56.82, n=40.46, o=2.71) are 0.44 for

ethylene, 0.47 for propylene, and 0.04 for

butadiene. The tax rate is calculated by

adding the products of the conversion factor for each taxable chemical by the tax rate

for that taxable chemical: ((0.44 x $9.74) +

(0.47 x $9.74) + (0.04 x $9.74) = $9.25).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

October 6, 2025

(i) HTSUS number: 4002.70.0000

(ii) Schedule B number: 4002.70.0000

(iii) CAS number: 25038-36-2

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

5. Determination to Add Ethylene

Vinyl Acetate (VA < 50%) ((C2H4)

-(C4H6O2)m; n=78.95, m=21.05) to the

List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters

of ethylene vinyl acetate (VA < 50%)

((C2H4)n-(C4H6O2)m; n=78.95, m=21.05),

submitted a petition in accordance with

Rev. Proc. 2022-26 requesting to add ethylene vinyl acetate (VA < 50%) ((C2H4)

-(C4H6O2)m; n=78.95, m=21.05) to the

List. According to the petition, the taxable chemicals ethylene and methane

constitute 66.23 percent by weight of the

materials used to produce ethylene vinyl

acetate (VA < 50%) ((C2H4)n-(C4H6O2)m;

n=78.95, m=21.05), based on the predominant method of production.

(a) Determination. Ethylene vinyl

acetate (VA < 50%) ((C2H4)n-(C4H6O2)m;

n=78.95, m=21.05) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing ethylene vinyl acetate (VA < 50%)

((C2H4)n-(C4H6O2)m; n=78.95, m=21.05)

is through a solution polymerization

employing the monomers of ethylene and

vinyl acetate in tert-butanol as a solvent

and a radical polymerization initiator.

(2) Stoichiometric material consumption equation:

n C2H4 (ethylene) + m [C2H4 (ethylene) + 1/2 CH4 (methane) + 2 CO +

1/2 O2] → (C2H4)n(C4H6O2)m (ethylene

vinyl acetate (VA < 50%)) + 1/2m CO2

(3) Reasons for the determination: The

ethylene vinyl acetate (VA < 50%) ((C2H4)

-(C4H6O2)m; n=78.95, m=21.05) petin

tion was filed on February 7, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 14688) on

April 3, 2025. The Treasury Department

and the IRS received no written comments

452

in response to the notice of filing. A public

hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals ethylene and methane constitute more than

20 percent by weight of the materials

used in the production of, based on the

predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of ethylene vinyl acetate (VA < 50%) ((C2H4)

-(C4H6O2)m; n=78.95, m=21.05) to the

List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.09 per ton. The conversion factors for the taxable chemicals used in the

production of ethylene vinyl acetate ((VA

< 50%) ((C2H4)n-(C4H6O2)m; n=78.95,

m=21.05) are 0.70 for ethylene and 0.04

for methane. The tax rate is calculated by

adding the products of the conversion factor for each taxable chemical by the tax

rate for that taxable chemical: ((0.70 x

$9.74) + (0.04 x $6.88) = $7.09).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 3901.30.6000

(ii) Schedule B number: 3901.30.6000

(iii) CAS number: 24937-78-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

6. Determination to Add Ethylene

Vinyl Acetate (VA ≥ 50%) ((C2H4)

-(C4H6O2)m; n=75.42, m=24.58) to the

List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters

Bulletin No. 2025–41

of ethylene vinyl acetate (VA ≥ 50%)

((C2H4)n-(C4H6O2)m; n=75.42, m=24.58),

submitted a petition in accordance with

Rev. Proc. 2022-26 requesting to add ethylene vinyl acetate (VA ≥ 50%) ((C2H4)

-(C4H6O2)m; n=75.42, m=24.58) to the

List. According to the petition, the taxable chemicals ethylene and methane

constitute 62.91 percent by weight of the

materials used to produce ethylene vinyl

acetate (VA ≥ 50%) ((C2H4)n-(C4H6O2)m;

n=75.42, m=24.58), based on the predominant method of production.

(a) Determination. Ethylene vinyl

acetate (VA ≥ 50%) ((C2H4)n-(C4H6O2)m;

n=75.42, m=24.58) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing ethylene vinyl acetate (VA ≥ 50%)

((C2H4)n-(C4H6O2)m; n=75.42, m=24.58)

is through a solution polymerization

employing the monomers of ethylene and

vinyl acetate in tert-butanol as a solvent

and a radical polymerization initiator.

(2) Stoichiometric material consumption equation:

n C2H4 (ethylene) + m [C2H4 (ethylene) + 1/2 CH4 (methane) + 2 CO +

1/2 O2] → (C2H4)n(C4H6O2)m (ethylene

vinyl acetate (VA ≥ 50%)) + 1/2m CO2

(3) Reasons for the determination:

The ethylene vinyl acetate (VA ≥ 50%)

((C2H4)n-(C4H6O2)m; n=75.42, m=24.58)

petition was filed on February 7, 2025.

The notice of filing summarizing the

petition and requesting comments was

published in the Federal Register (90

FR 14683) on April 3, 2025. The Treasury Department and the IRS received

no written comments in response to the

notice of filing. A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals ethylene and

methane constitute more than 20 percent

by weight of the materials used in the

production of, based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

Bulletin No. 2025–41

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of ethylene vinyl acetate (VA ≥ 50%) ((C2H4)

-(C4H6O2)m; n=75.42, m=24.58) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $6.77 per ton. The conversion factors for the taxable chemicals used in the

production of ethylene vinyl acetate (VA

≥ 50%) ((C2H4)n-(C4H6O2)m; n=75.42,

m=24.58) are 0.66 for ethylene and 0.05

for methane. The tax rate is calculated by

adding the products of the conversion factor for each taxable chemical by the tax

rate for that taxable chemical: ((0.66 x

$9.74) + (0.05 x $6.88) = $6.77).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 3905.29.0000

(ii) Schedule B number: 3905.29.0000

(iii) CAS number: 24937-78-8

(2) The Secretary is unable to confirm

the following classification numbers: Not

applicable.

7. Determination to Add Hydrogenated

Acrylonitrile-Butadiene Rubber

((C4H8)n-(C3H3N)m; n=22.28, m=38.86)

to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters

of hydrogenated acrylonitrile-butadiene rubber ((C4H8)n-(C3H3N)m; n=22.28,

m=38.86), submitted a petition in

accordance with Rev. Proc. 2022-26

requesting to add hydrogenated acrylonitrile-butadiene

rubber

((C4H8)

-(C

;

n=22.28,

m=38.86)

to the

3 3

List. According to the petition, the

taxable chemicals butadiene, propylene, ammonia, and methane constitute

63.48 percent by weight of the materials

used to produce hydrogenated acrylonitrile-butadiene rubber ((C4H8)n-(C3H3N)

; n=22.28, m=38.86), based on the prem

dominant method of production.

453

(a) Determination. Hydrogenated

acrylonitrile-butadiene rubber ((C4H8)

-(C3H3N)m; n=22.28, m=38.86) is added

to the list of taxable substances under section 4672(a). Other pertinent information

is as follows:

(1) Predominant method of production: The predominant method of producing hydrogenated acrylonitrile-butadiene

rubber is via catalytic hydrogenation of

acrylonitrile-butadiene rubber which is

derived from the emulsion polymerization

of butadiene and acrylonitrile.

(2) Stoichiometric material consumption equation:

n C4H6 (butadiene) + m [C3H6 (propylene) + NH3 (ammonia) + 3/2 O2]

+ n [1/4 CH4 (methane) + 1/2 H2O]

→ (C4H8)n-(C3H3N)m (hydrogenated

acrylonitrile-butadiene rubber) + 3m

H2O + 1/4n CO2

(3) Reasons for the determination:

The hydrogenated acrylonitrile-butadiene rubber (C4H8)n-(C3H3N)m; n=22.28,

m=38.86) petition was filed on February

7, 2025. The notice of filing summarizing the petition and requesting comments

was published in the Federal Register (90

FR 14686) on April 3, 2025. The Treasury Department and the IRS received

two non-substantive written comments in

response to the notice of filing. One comment received by the IRS recommended

prohibiting the manufacture of this substance. The other comment received by

the IRS was unrelated to the determination for this substance. The comments

did not address whether hydrogenated

acrylonitrile-butadiene rubber ((C4H8)

-(C3H3N)m; n=22.28, m=38.86) meets

the weight or value test under section

4672(a)(2)(B). A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals butadiene, propylene, ammonia, and methane constitute

more than 20 percent by weight of the

materials used in the production of, based

on the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

October 6, 2025

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

hydrogenated

acrylonitrile-butadiene

rubber

(C4H8)n-(C3H3N)m;

n=22.28,

m=38.86) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.54 per ton. The conversion

factors for the taxable chemicals used

in the production of hydrogenated

acrylonitrile-butadiene rubber (C4H8)

-(C3H3N)m; n=22.28, m=38.86) are 0.36

for butadiene, 0.49 for propylene, 0.20

for ammonia, and 0.03 for methane.

The tax rate is calculated by adding the

products of the conversion factor for

each taxable chemical by the tax rate for

that taxable chemical: ((0.36 x $9.74) +

(0.49 x $9.74) + (0.20 x $5.28) + (0.03 x

$6.88) = $9.54).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.59.0000

(ii) Schedule B number: 4002.59.0000

(iii) CAS number: 308068-83-9

(2) The Secretary is unable to confirm

the following classification numbers: Not

applicable.

8. Determination To Add Isobuteneisoprene Rubber ((C4H8)n-(C5H8)m;

n=99.10, m=0.90) to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters of

isobutene-isoprene rubber ((C4H8)n-(C5H8)

; n=99.10, m=0.90) submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10, m=0.90)

to the List. According to the petition, the

taxable chemical butylene constitutes

98.91 percent by weight of the materials

used to produce isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10, m=0.90),

based on the predominant method of production.

October 6, 2025

(a) Determination. Isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10,

m=0.90) is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing isobutene-isoprene rubber is via

the cationic copolymerization of butylene

with isoprene in the presence of a Friedel-Crafts catalyst at low temperature,

around -100°C. The final product contains

0.7 wt% of additives.

(2) Stoichiometric material consumption equation:

n C4H8 (butylene) + m C5H8 (isoprene)

→ (C4H8)n(C5H8)m (isobutene-isoprene

rubber)

(3) Reasons for the determination:

The isobutene-isoprene rubber ((C4H8)

-(C5H8)m; n=99.10, m=0.90) petition

was filed on February 7, 2025. The notice

of filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 14689) on

April 3, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process in

section 4672(a)(2)(B) in making this determination. A review of the stoichiometric

material consumption equation and other

information in the petition shows that the

taxable chemical butylene constitutes more

than 20 percent by weight of the materials

used in the production of isobutene-isoprene rubber ((C4H8)n-(C5H8)m; n=99.10,

m=0.90), based on the predominant method

of production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of isobutene-isoprene rubber ((C4H8)n-(C5H8)m;

n=99.10, m=0.90) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

454

(6) Tax rate prescribed by the Secretary: $9.64 per ton. The conversion factor

for the butylene used in the production of

isobutene-isoprene rubber ((C4H8)n-(C5H8)

; n=99.10, m=0.90) is 0.99. The tax rate

is calculated by multiplying the conversion factor by the tax rate for butylene:

(0.99 x $9.74 = $9.64).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.31.0000

(ii) Schedule B number: 4002.31.0000

(iii) CAS number: 9010-85-9

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

9. Determination to Add Poly(ethylenepropylene) Rubber ((C2H4)m-(C3H6)n;

m=59.04, n=40.96) to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters of

poly(ethylene-propylene) rubber ((C2H4)

-(C3H6)n; m=59.04, n=40.96), submitm

ted a petition in accordance with Rev.

Proc. 2022-26 requesting to add poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n;

m=59.04, n=40.96) to the List. According

to the petition, the taxable chemicals ethylene and propylene constitute 100 percent

by weight of the materials used to produce

poly(ethylene-propylene) rubber ((C2H4)

-(C3H6)n; m=59.04, n=40.96), based on

the predominant method of production.

(a) Determination. Poly(ethylene-propylene)

rubber

((C2H4)m-(C3H6)n;

m=59.04, n=40.96) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing poly(ethylene-propylene) rubber

is through the catalytic polymerization

of ethylene and propylene monomers in a

solution using various catalysts.

(2) Stoichiometric material consumption equation:

m C2H4 (ethylene) + n C3H6 (propylene) → (C2H4)m-(C3H6)n (poly(ethylene-propylene) rubber)

(3) Reasons for the determination: The

poly(ethylene-propylene) rubber ((C2H4)

Bulletin No. 2025–41

-(C3H6)n; m=59.04, n=40.96) petition

was filed on February 7, 2025. The notice

of filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 14690) on

April 3, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals ethylene and

propylene constitute more than 20 percent

by weight of the materials used in the production of poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n; m=59.04, n=40.96),

based on the predominant method of

production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

poly(ethylene-propylene) rubber ((C2H4)

-(C3H6)n; m=59.04, n=40.96) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion

factors for the taxable chemicals used in

the production of poly(ethylene-propylene) rubber ((C2H4)m-(C3H6)n; m=59.04,

n=40.96) are 0.49 for ethylene and 0.51

for propylene. The tax rate is calculated

by adding the products of the conversion factor for each taxable chemical

and the tax rate for that taxable chemical: ((0.49 x $9.74) + (0.51 x $9.74) =

$9.74).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 9010-71-1

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 3901.40.0000

(ii) Schedule B number: 3901.40.0000

Bulletin No. 2025–41

10. Determination to Add Emulsion

Styrene-butadiene Rubber ((C4H6)

-(C8H8)n; m=15.83, n=2.53) to the List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters

of emulsion styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=15.83; n=2.53), submitted a petition in accordance with Rev.

Proc. 2022-26 requesting to add emulsion

styrene-butadiene rubber ((C4H6)m-(C8H8)

; m=15.83; n=2.53) to the List. Accordn

ing to the petition, the taxable chemicals

butadiene, benzene, and ethylene constitute 100 percent by weight of the materials

used to produce emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83;

n=2.53), based on the predominant

method of production.

(a) Determination. Emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n;

m=15.83; n=2.53) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing emulsion styrene-butadiene rubber is

through the emulsion polymerization of

butadiene and styrene initiated by free

radicals. Styrene monomer is produced by

the dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts

reaction of benzene and ethylene.

(2) Stoichiometric material consumption equation:

m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)

-(C8H8)n (emulsion styrene-butadiene

rubber) + n H2 (hydrogen)

(3) Reasons for the determination:

The emulsion styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=15.83; n=2.53) petition was filed on February 7, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 14686) on

April 3, 2025. The Treasury Department

and the IRS received no written comments

in response to the notice of filing. A public

hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

455

shows that the taxable chemicals butadiene, benzene, and ethylene constitute

more than 20 percent by weight of the

materials used in the production of emulsion styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=15.83; n=2.53), based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of emulsion styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=15.83; n=2.53) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors for the taxable chemicals used in the

production of emulsion styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=15.83;

n=2.53) are 0.76 for butadiene, 0.18 for

benzene, and 0.06 for ethylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.76 x $9.74) + (0.18 x $9.74)

+ (0.06 x $9.74) = $9.74).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS numbers: 4002.19.0015

(rubber), 4002.11.0000 (latex)

(ii) Schedule B numbers: 4002.19.9000

(rubber), 4002.11.0000 (latex)

(iii) CAS number: 9003-55-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

11. Determination to Add Solution

Styrene-butadiene Rubber ((C4H6)

-(C8H8)n; m=67.16, n=32.85) to the

List

Arlanxeo USA LLC and Arlanxeo

Canada Inc., importers and exporters of

solution styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=67.16; n=32.85), submitted

a petition in accordance with Rev. Proc.

October 6, 2025

2022-26 requesting to add solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;

m=67.16; n=32.85) to the List. According to the petition, the taxable chemicals

butadiene, benzene, and ethylene constitute 100 percent by weight of the materials used to produce solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16;

n=32.85), based on the predominant

method of production.

(a) Determination. Solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;

m=67.16; n=32.85) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production: The predominant method of

producing solution styrene-butadiene

rubber is through the anionic polymerization of butadiene and styrene initiated by alkyl lithium compounds in

hexanes as solvent. Styrene monomer

is produced by the dehydrogenation of

ethylbenzene. Ethylbenzene is produced

via a Friedel-Crafts reaction of benzene

and ethylene.

(2) Stoichiometric material consumption equation:

m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)

-(C8H8)n (solution styrene-butadiene

rubber) + n H2 (hydrogen); m=67.16;

n=32.85

(3) Reasons for the determination:

The solution styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=67.16; n=32.85)

petition was filed on February 7, 2025.

The notice of filing summarizing the

petition and requesting comments was

published in the Federal Register (90

FR 14690) on April 3, 2025. The Treasury Department and the IRS received

no written comments in response to the

notice of filing. A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals butadiene, benzene, and ethylene constitute more than 20

percent by weight of the materials used in

the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16;

October 6, 2025

n=32.85), based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of solution styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=67.16; n=32.85) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors

for the taxable chemicals used in the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=67.16; n=32.85)

are 0.51 for butadiene, 0.36 for benzene,

and 0.13 for ethylene. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical

and the tax rate for that taxable chemical:

((0.51 x $9.74) + (0.36 x $9.74) + (0.13 x

$9.74) = $9.74).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 9003-55-8

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 4002.19.0016

(ii) Schedule B number: 4002.19.1600

12. Determination to Add Emulsion

Styrene Butadiene Rubber ((C4H6)

-(C8H8)n; m=14.14, n=2.26) to the List

Michelin North America, Inc., an

importer of emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14,

n=2.26), submitted a petition in accordance with Rev. Proc. 2022-26 requesting to add emulsion styrene butadiene

rubber

((C4H6)m-(C8H8)n;

m=14.14,

n=2.26) to the List. According to the

petition, the taxable chemicals butadiene,

benzene, and ethylene constitute 100 percent by weight of the materials used to

produce emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14, n=2.26),

based on the predominant method of production.

456

(a) Determination. Emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n;

m=14.14, n=2.26) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

emulsion styrene butadiene rubber ((C4H6)

-(C8H8)n; m=14.14, n=2.26) is through a

low temperature, emulsion copolymerization of butadiene and styrene, using

fatty and rosin acid soaps as an emulsifier,

and organic hydroperoxides as an initiator. Styrene monomer is produced by the

dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts

reaction of benzene and ethylene.

(2) Stoichiometric material consumption equation:

m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)

-(C8H8)n (emulsion styrene butadiene

rubber) + n H2 (hydrogen); m=14.14;

n=2.26

(3) Reasons for the determination:

The emulsion styrene butadiene rubber

((C4H6)m-(C8H8)n; m=14.14, n=2.26) petition was filed on February 7, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 14692) on

April 3, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals butadiene, benzene, and ethylene constitute

more than 20 percent by weight of the

materials used in the production of emulsion styrene butadiene rubber ((C4H6)

-(C8H8)n; m=14.14, n=2.26), based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of emulsion styrene butadiene rubber ((C4H6)

-(C8H8)n; m=14.14, n=2.26) to the List:

Bulletin No. 2025–41

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors for the taxable chemicals used in the

production of emulsion styrene butadiene rubber ((C4H6)m-(C8H8)n; m=14.14,

n=2.26) are 0.76 for butadiene, 0.18 for

benzene, and 0.06 for ethylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.76 x $9.74) + (0.18 x $9.74)

+ (0.06 x $9.74) = $9.74).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.19.0015

(ii) Schedule B number: 4002.19.9000

(iii) CAS number: 9003-55-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

13. Determination to Add Solution

Styrene-butadiene Rubber ((C4H6)

-(C8H8)n; m=13.31, n=2.50) to the List

Michelin North America, Inc., an

importer of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31,

n=2.50), submitted a petition in accordance with Rev. Proc. 2022-26 requesting

to add solution styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=13.31, n=2.50) to

the List. According to the petition, the

taxable chemicals butadiene, benzene and

ethylene constitute 100 percent by weight

of the materials used to produce solution

styrene-butadiene rubber ((C4H6)m-(C8H8)

; m=13.31, n=2.50), based on the pren

dominant method of production.

(a) Determination. Solution styrene-butadiene rubber ((C4H6)m-(C8H8)n;

m=13.31, n=2.50) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

solution styrene-butadiene rubber ((C4H6)

Bulletin No. 2025–41

-(C8H8)n; m=13.31, n=2.50) is through

the continuous polymerization of butadiene and styrene initiated by alkyl lithium

compounds in toluene or CMHC (cyclohexane and methylhexane) as solvents.

Styrene monomer is produced by the

dehydrogenation of ethylbenzene. Ethylbenzene is produced via a Friedel-Crafts

reaction of benzene and ethylene.

(2) Stoichiometric material consumption equation:

m C4H6 (butadiene) + n [C6H6 (benzene) + C2H4 (ethylene)] → (C4H6)

-(C8H8)n (solution styrene butadiene

rubber) + n H2 (hydrogen); m=13.31;

n=2.5

(3) Reasons for the determination:

The solution styrene-butadiene rubber

((C4H6)m-(C8H8)n; m=13.31, n=2.50) petition was filed on February 7, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 14693) on

April 3, 2025. The Treasury Department

and the IRS received one non-substantive

written comment on the necessity of the

filing to understand its impact in response

to the notice of filing. The comment did

not address whether solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31,

n=2.50) meets the weight or value test

under section 4672(a)(2)(B). A public

hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals butadiene, benzene and ethylene constitute

more than 20 percent by weight of the

materials used in the production of solution styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=13.31, n=2.50), based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of solution styrene-butadiene rubber ((C4H6)

-(C8H8)n; m=13.31, n=2.50) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

457

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.74 per ton. The conversion factors

for the taxable chemicals used in the production of solution styrene-butadiene rubber ((C4H6)m-(C8H8)n; m=13.31, n=2.50)

are 0.73 for butylene, 0.20 for benzene,

and 0.07 for ethylene. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical

and the tax rate for that taxable chemical:

((0.73 x $9.74) + (0.20 x $9.74) + (0.07 x

$9.74) = $9.74).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.19.0016

(ii) Schedule B number: 4002.19.1600

(iii) CAS number: 9003-55-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

14. Determination to Add

Hydrogenated Acrylonitrile-butadiene

Rubber ((C4H8)x-(C3H3N)y-(C15H24O)a;

x=2,783.05, y=1,907.27, a=5.74) to the

List

Zeon Chemicals L.P., an importer

and exporter of hydrogenated acrylonitrile-butadiene rubber ((C4H8)x-(C3H3N)

-(C15H24O)a; x=2,783.05, y=1,907.27,

a=5.74), also known as “HNBR,” submitted a petition in accordance with Rev.

Proc. 2022-26 requesting to add HNBR

to the List. According to the petition, the

taxable chemicals butadiene, propylene,

ammonia, methane, butylene, toluene, sulfuric acid, and sodium hydroxide constitute 67.01 percent by weight of the materials used to produce HNBR, based on the

predominant method of production.

(a) Determination. Hydrogenated

acrylonitrile-butadiene rubber ((C4H8)

-(C3H3N)y-(C15H24O)a;

x=2,783.05,

y=1,907.27, a=5.74) is added to the list of

taxable substances under section 4672(a).

Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

HNBR is via catalytic hydrogenation of

October 6, 2025

acrylonitrile-butadiene rubber (“NBR”)

in a solution of acetone and in the presence of a catalyst. NBR is derived from

the emulsion polymerization of butadiene

and acrylonitrile. Acrylonitrile monomer

is produced by the SOHIO process (i.e.,

catalytic ammoxidation of propylene).

Hydrogen is made from steam-methane

reforming. Butylated hydroxytoluene is

produced from the reaction of p-cresol

with butylene. p-Cresol is prepared by a

two-step route beginning with the sulfonation of toluene, followed by basic hydrolysis.

(2) Stoichiometric material consumption equation:

x C4H6 (butadiene) + y C3H6 (propylene) + y NH3 (ammonia) + 3/2y O2 +

1/2x CH4 (methane) + x H2O + a C7H8

(toluene) + a H2SO4 (sulfuric acid) +

2a NaOH (sodium hydroxide) + 2a

C4H8 (butylene) → (C4H8)x-(C3H3N)

-(C15H24O)a (HNBR) + 1/2x CO2 (cary

bon dioxide)+ (3y+2a) H2O (water)

+ a Na2SO3 (sodium sulfite)+ x H21

(hydrogen)

(3) Reasons for the determination: The

HNBR petition was filed on February 14,

2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

14685) on April 3, 2025, and a correction

was published in the Federal Register (90

FR 19245) on May 6, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals butadiene, propylene, ammonia, methane, butylene, toluene, sulfuric acid, and sodium

hydroxide constitute more than 20 percent by weight of the materials used in

the production of HNBR, based on the

predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

HNBR to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): April 1, 2023

(6) Tax rate prescribed by the Secretary: $10.02 per ton. The conversion factors for the taxable chemicals used in the

production of HNBR are 0.58 for butadiene, 0.31 for propylene, 0.13 for ammonia, 0.09 for methane, 0.002 for butylene,

0.002 for toluene, 0.002 for sulfuric acid,

and 0.002 for sodium hydroxide. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.58 x $9.74) + (0.31 x $9.74)

+ (0.13 x $5.28) + (0.09 x $6.88) + (0.002

x $9.74) + (0.002 x $9.74) + (0.002 x

$0.52) + (0.002 x $0.56) = $10.02).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.59.00002

(ii) Schedule B number: 4002.59.0000

(iii) CAS number: 88254-10-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

15. Determination to Add Bromobutyl

Isobutylene Isoprene Rubber (((C4H8)

(C5H8)y(Br2)z); x=7071, y=59, z=50) to

the List

Exxon Mobil Corporation, an exporter

of bromobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Br2)z; x=7071, y=59,

z=50), also known as “BIIR,” submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add BIIR to the

List. According to the petition, the tax-

able chemicals isobutylene (an isomer of

butylene) and bromine constitute 99.01

percent by weight of the materials used to

produce BIIR, based on the predominant

method of production.

(a) Determination. Bromobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)

(Br2)z; x=7071, y=59, z=50) is added to

the list of taxable substances under section

4672(a). Other pertinent information is as

follows:

(1) Predominant method of production: The predominant method of regular butyl rubber production is using a

carbocationic polymerization reaction

of isobutylene and a comonomer of isoprene. The catalyst system used is typically composed of aluminum chloride,

boron trifluoride or similar dissolved in

a methyl chloride solvent. Monomer feed

of isobutylene and isoprene dissolved

in a methyl chloride solvent are fed to a

reactor operated at approximately -100°C

to control the rapid exothermic polymerization reaction generating a high molecular weight butyl rubber polymer. To

obtain this high molecular weight polymer it is necessary for the feed monomers

to be as pure as possible ensuring that the

feed system stays as dry as possible. The

methyl chloride and unreacted monomers

are flashed overhead and recycled back to

the feed system while the polymer is precipitated out as a solid which is finished

and packaged.

The polymerization process for BIIR

starts with the exact same process for regular butyl rubber outlined above. A subsequent halogenation step is then carried out

in a well agitated vessel to ionically substitute a bromine molecule to the polymer

backbone while the polymer is dissolved

in an appropriate solvent. The solvent

is then flashed precipitating out a solid

which is then baled and packaged.

(2) Stoichiometric material consumption equation:

7071 C4H8 (isobutylene) + 59 C5H8

(isoprene) + 50 Br2 (bromine) →

[7071 C4H8 + 59 C5H8 + 50 Br2]

(BIIR)

The petition, and consequently the notice of filing, inadvertently omitted “x H2” from the products side of the stoichiometric material consumption equation. This omission has no impact on

the weight or value test. For clarity “x H2” has been included here.

The Notice of Filing erroneously stated that the HTSUS number as “4002.59.000” and the Schedule B number as “4002.59.000.” These errors are corrected here.

October 6, 2025

458

Bulletin No. 2025–41

(3) Reasons for the determination:

The BIIR petition was filed on April 8,

2025.3 The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

20346) on May 13, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals isobutylene (an

isomer of butylene) and bromine constitute more than 20 percent by weight of the

materials used in the production of BIIR,

based on the predominant method of production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of BIIR

to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.63 per ton. The conversion factors for the taxable chemicals used in the

production of BIIR are 0.97 for butylene

and 0.02 for bromine. The tax rate is

calculated by adding the products of the

conversion factor for each taxable chemical and the tax rate for that taxable chemical: ((0.97 x $9.74) + (0.02 x $8.90) =

$9.63).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.39.00

(ii) Schedule B number: 4002.39.00

(iii) CAS number: 68441-14-5

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

16. Determination to Add Chlorobutyl

Isobutylene Isoprene Rubber ((C4H8)

(C5H8)y(Cl2)z); x=7036, y=88, z=70) to

the List

Exxon Mobil Corporation, an exporter

of chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)y(Cl2)z); x=7036, y=88,

z=70), also known as “CIIR,” submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add CIIR to the

List. According to the petition, the taxable

chemicals isobutylene (an isomer of butylene) and chlorine constitute 98.50 percent

by weight of the materials used to produce

CIIR, based on the predominant method

of production.

(a) Determination. Chlorobutyl isobutylene isoprene rubber ((C4H8)x(C5H8)

(Cl2)z); x=7036, y=88, z=70) is added to

the list of taxable substances under section

4672(a). Other pertinent information is as

follows:

(1) Predominant method of production:

The predominant method of production

of regular butyl rubber is using a carbocationic polymerization reaction of isobutylene and a comonomer of isoprene. The

catalyst system used is typically composed

of aluminum chloride, boron trifluoride

or similar with an initiator dissolved in a

methyl chloride solvent. Monomer feed

of isobutylene and isoprene dissolved in a

methyl chloride solvent are fed to a reactor operated at approximately -100⁰C to

control the rapid exothermic polymerization reaction generating a high molecular

weight regular butyl rubber polymer. To

obtain this high molecular weight polymer

it is necessary for the feed monomers to be

as pure as possible as well as ensuring that

the feed system stays as dry as possible.

The methyl chloride and unreacted monomers are flashed overhead and recycled

back to the feed system while the polymer

is precipitated out as a solid which is then

baled and packaged.

The polymerization process for CIIR

starts with the exact same process for regular butyl rubber outlined above. A subsequent halogenation step is then carried out

in a well agitated vessel to ionically substitute a chlorine molecule to the polymer

backbone while the polymer is dissolved

in an appropriate solvent. The solvent

is then flashed, precipitating out a solid

which is then baled and packaged.

(2) Stoichiometric material consumption equation:

7036 C4H8 (isobutylene) + 88 C5H8

(isoprene) + 70 Cl2 (chlorine) → [7036

C4H8 + 88 C5H8 + 70 Cl2] (CIIR)

(3) Reasons for the determination:

The CIIR petition was filed on April 8,

2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

20350) on May 13, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals isobutylene (an isomer of butylene) and chlorine constitute more than 20 percent by

weight of the materials used in the production of CIIR, based on the predominant method of production. Therefore,

the test in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of CIIR

to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.50 per ton. The conversion factors for the taxable chemicals used in the

production of CIIR are 0.97 for butylene

and 0.01 for chlorine. The tax rate is calculated by adding the products of the conversion factor for each taxable chemical

and the tax rate for that taxable chemical:

((0.97 x $9.74) + (0.01 x $5.40) = $9.50).

The Notice of Filing erroneously stated the year of filing as 2023. This error is corrected here.

Bulletin No. 2025–41

459

October 6, 2025

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.39.00

(ii) Schedule B number: 4002.39.00

(iii) CAS number: 68081-82-3

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

17. Determination to Add DIPE–Diisopropyl Ether to the List

Exxon Mobil Corporation, an exporter

of DIPE–di-isopropyl ether submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add DIPE–di-isopropyl ether to the List. According to the

petition, the taxable chemical propylene

constitutes 82.40 percent by weight of the

materials used to produce DIPE–di-isopropyl ether, based on the predominant

method of production.

(a) Determination. DIPE–di-isopropyl

ether is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:

(1) Predominant method of production:

DIPE–di-isopropyl ether is produced via

isopropyl alcohol (IPA) production using

a two-step indirect hydration process.

A mixed propane/propylene stream is

reacted with aqueous sulfuric acid to form

a H2SO4/propylene extract. The formed

isopropyl hydrogen sulfate is further

reacted with additional IPA under acidic

conditions to form DIPE–di-isopropyl

ether such that two moles of isopropanol

are converted to one mole of DIPE–di-isopropyl ether and one mole of water.

(2) Stoichiometric material consumption equation:

2 C3H6 [propylene] + H2O [water] →

C6H14O [DIPE–di-isopropyl ether]

(3) Reasons for the determination:

The DIPE–di-isopropyl ether petition was

filed on May 1, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

October 6, 2025

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemical propylene constitutes more than 20 percent by weight

of the materials used in the production

of DIPE–di-isopropyl ether, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

DIPE–di-isopropyl ether to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.99 per ton. The conversion

factor for the propylene used in the production of DIPE–di-isopropyl ether is

0.82. The tax rate is calculated by multiplying the conversion factor by the

tax rate for propylene: (0.82 x $9.74 =

$7.99).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2909.19.18.00

(ii) Schedule B number: 2909.19.18.00

(iii) CAS number: 108-20-3

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

18. Determination to Add Di-isodecyl

Phthalate to the List

Exxon Mobil Corporation, an exporter

of di-isodecyl phthalate, submitted a petition in accordance with Rev. Proc. 202226 requesting to add di-isodecyl phthalate

to the List. According to the petition, the

taxable chemicals propylene and orthoxylene (an isomer of xylene) constitute

64.50 percent by weight of the materials

used to produce di-isodecyl phthalate,

based on the predominant method of production.

460

(a) Determination. Di-isodecyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

di-isodecyl phthalate is via esterification.

This process can be readily carried

out in heated kettles with agitation and

provision for water takeoff. Esterification

catalysts (e.g., sulfuric acid or p-toluenesulfonic acid) speed the reaction and are

neutralized, washed, and then removed.

The purity requirements for commercial

plasticizers are very high; phthalate esters

are usually colorless and are mostly odorless. In the case of phthalates, the esterification is carried out through the reaction

of phthalic anhydride and 2-ethylhexanol

to produce dioctyl phthalate (DOP).

This reaction usually requires an

excess of alcohol, which is readily recycled. Analogous syntheses yield aliphatic

dicarboxylic acid esters, benzoates, and

trimellitates.

(2) Stoichiometric material consumption equation:

5.45 C3H6 [propylene] + 0.35 C5H10

[amylene] + 2 CO [carbon monoxide]

+ 4 H2 [hydrogen] + C8H10 [orthoxylene] + 3 O2 [oxygen] → C28H46O4

[di-isodecyl phthalate] + 4 H2O

[water]

(3) Reasons for the determination:

The di-isodecyl phthalate petition was

filed on April 8, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals propylene and

orthoxylene (an isomer of xylene) constitute more than 20 percent by weight of the

materials used in the production of di-isodecyl phthalate, based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

Bulletin No. 2025–41

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

di-isodecyl phthalate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.31 per ton. The conversion factors

for the taxable chemicals used in the production of di-isodecyl phthalate are 0.51

for propylene and 0.24 for xylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.51 x $9.74) + (0.24 x $9.74)

= $7.31).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers: Not applicable.

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2917.33.00.10

(ii) Schedule B number: 2917.33.00.10

(iii) CAS number: 68515-49-1

19. Determination to Add Di-isononyl

Adipate to the List

Exxon Mobil Corporation, an exporter

of di-isononyl adipate, also known as

“DINA,” submitted a petition in accordance with Rev. Proc. 2022-26 requesting

to add DINA to the List. According to the

petition, the taxable chemicals propylene,

benzene, and nitric acid constitute 79.20

percent by weight of the materials used to

produce DINA, based on the predominant

method of production.

(a) Determination. Di-isononyl adipate

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

DINA is produced via esterification. The

di-isononyl adipate di-ester is made by

reacting primary isononyl (C9) alcohol

with adipic acid. The ester is produced by

esterification of two moles of isononyl C9

Bulletin No. 2025–41

alcohol and one mole of adipic acid in the

presence of a catalyst.

By using excess alcohol (up to 30%

molar excess of C9 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the di-ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C – 250°C), while removing the

water formed.

Excess alcohol is distilled from the

ester by vacuum prior to neutralization and

recycled into subsequent batches. The final

ester is purified by neutralizing with a base

such as an aqueous solution of sodium carbonate. The remaining excess water is distilled off and the ester is then filtered using

filter agents. The degree of purity of the

ester has a minimum 99.0 wt%.

(2) Stoichiometric material consumption equation:

4.82 C3H6 [propylene] + 0.30 C5H10

[amylene] + 2 CO [carbon monoxide]

+ 7 H2 [hydrogen] + C6H6 [benzene]

+ 0.50 O2 [oxygen] + 2 HNO3 [nitric

acid] → C24H46O4 [di-isononyl adipate] + 4 H2O [water] + N2O [nitrous

oxide]

(3) Reasons for the determination:

The DINA petition was filed on May 1,

2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

21131) on May 16, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals propylene,

benzene, and nitric acid constitute more

than 20 percent by weight of the materials used in the production of DINA, based

on the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

461

(5) Effective dates for addition of DINA

to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.07 per ton. The conversion factors

for the taxable chemicals used in the production of DINA are 0.51 for propylene,

0.20 for benzene, and 0.32 for nitric acid.

The tax rate is calculated by adding the

products of the conversion factor for each

taxable chemical and the tax rate for that

taxable chemical: ((0.51 x $9.74) + (0.20

x $9.74) + (0.32 x $0.48) = $7.07).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2917.12.20.00

(ii) Schedule B number: 2917.12.2000

(iii) CAS number: 33703–08–1

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

20. Determination to Add Di-isononyl

Phthalate to the List

Exxon Mobil Corporation, an exporter

of di-isononyl phthalate, submitted a petition in accordance with Rev. Proc. 2022-26

requesting to add di-isononyl phthalate to

the List. According to the petition, the taxable chemicals propylene and orthoxylene

(an isomer of xylene) constitute 62.90

percent by weight of the materials used to

produce di-isononyl phthalate, based on the

predominant method of production.

(a) Determination. Di-isononyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

di-isononyl phthalate is via esterification.

Most plasticizers are products of simple esterification reactions, which can be

readily carried out in heated kettles with

agitation and provision for water takeoff.

While some plants produce plasticizers

October 6, 2025

by such batch methods, newer, highly

automated plants operate continuously,

particularly if they emphasize a single

product. Esterification catalysts (e.g.

sulfuric acid or p-toluenesulfonic acid)

speed the reaction and are neutralized,

washed, and then removed. The purity

requirements for commercial plasticizers

are very high; phthalate esters are usually

colorless and are mostly odorless. The

reaction usually requires an excess of

alcohol, which is readily recycled. Analogous syntheses yield aliphatic dicarboxylic acid esters, benzoates, and trimellitates.

The hydrogen used for these reactions

is not produced from steam-methane

reforming; the source is from a POx reactor, which feeds liquids, not methane. The

POx process is an industrial process that

converts hydrocarbons feeds into syngas

(a combination of H2 and CO gas). The

hydrocarbon feed is in the liquid state;

it does not feed gas (such as methane)

or solids. The unit feeds a variety of liquid hydrocarbons such as paraffins, olefins, and aromatics in the C9-C20 range,

obtained from the refinery pipestills and

other chemicals units.

(2) Stoichiometric material consumption equation:

5.12 x 0.94 C3H6 [propylene] + 5.12 x

0.06 C5H10 [amylene] + 2 CO [carbon

monoxide] + 4 H2 [hydrogen] + C8H10

[orthoxylene] + 3 O2 [oxygen] →

C26H42O4 [di-isononyl phthalate] + 4

H2O [water]

(3) Reasons for the determination:

The di-isononyl phthalate petition

was filed on May 1, 2025. The notice

of filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 20551) on

May 14, 2025. The Treasury Department and the IRS received no written

comments in response to the notice of

filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals propylene and

orthoxylene (an isomer of xylene) constitute more than 20 percent by weight

of the materials used in the production of

di-isononyl phthalate, based on the predominant method of production. Therefore, the test in section 4672(a)(2)(B) is

satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

di-isononyl phthalate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.11 per ton. The conversion factors

for the taxable chemicals used in the production of di-isononyl phthalate are 0.48

for propylene and 0.25 for xylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.48 x $9.74) + (0.25 x $9.74)

= $7.11).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers: Not applicable.

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2917.33.00.50

(ii) Schedule B number: 2917.33.00.50

(iii) CAS number: 68515-48-0

21. Determination to Add Di-tridecyl

Phthalate to the List

Exxon Mobil Corporation, an exporter

of di-tridecyl phthalate, submitted a petition in accordance with Rev. Proc. 202226 requesting to add di-tridecyl phthalate

to the List. According to the petition, the

taxable chemicals propylene and orthoxylene (an isomer of xylene) constitute

68.10 percent by weight of the materials used to produce di-tridecyl phthalate,

based on the predominant method of production.

(a) Determination. Di-tridecyl phthalate is added to the list of taxable substances under section 4672(a). Other pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

di-tridecyl phthalate4 is via esterification.

This process can be readily carried

out in heated kettles with agitation and

provision for water takeoff. Esterification catalysts (e.g., sulfuric acid or p-toluenesulfonic acid) speed the reaction

and are neutralized, washed, and then

removed. The purity requirements for

commercial plasticizers are very high;

phthalate esters are usually colorless

and are mostly odorless. In the case of

phthalates, the esterification is carried

out through the reaction of phthalic

anhydride and 2-ethylhexanol to produce

dioctyl phthalate (DOP).

This reaction usually requires an

excess of alcohol, which is readily recycled. Analogous syntheses yield aliphatic

dicarboxylic acid esters, benzoates, and

trimellitates.

(2) Stoichiometric material consumption equation:

7.70 x 0.94 C3H6 [propylene] + 7.70 x

0.06 C5H10 [amylene] + 2 CO [carbon

monoxide] + 4 H2 [hydrogen] + C8H10

[orthoxylene] + 3 O2 [oxygen] →

C34H58O4 [di-tridecyl phthalate] + 4

H2O [water]

(3) Reasons for the determination: The

di-tridecyl phthalate petition was filed on

April 8, 2025. The notice of filing summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals pro-

The Notice of Filing for di-tridecyl phthalate had a typographical error misstating the name of the taxable substance in the predominant method of production section. This error is corrected

here.

October 6, 2025

462

Bulletin No. 2025–41

pylene and orthoxylene (an isomer of

xylene) constitute more than 20 percent

by weight of the materials used in the production of di-tridecyl phthalate, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of di-tridecyl phthalate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.50 per ton. The conversion factors

for the taxable chemicals used in the production of di-tridecyl phthalate are 0.57

for propylene and 0.20 for xylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.57 x $9.74) + (0.20 x $9.74)

= $7.50).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers: Not applicable.

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2917.34.01.50

(ii) Schedule B number: 2917.34.0150

(iii) CAS number: 68515-47-9

22. Determination to Add Ethylene

Propylene Diene (EPDM) Rubber

((C2H4)x(C3H6)y(C9H12)z; x=5134,

y=2250, z=98) to the List

Exxon Mobil Corporation, an exporter

of ethylene propylene diene (EPDM)

rubber ((C2H4)x(C3H6)y(C9H12)z; x=5134,

y=2250, z=98), submitted a petition in

accordance with Rev. Proc. 2022-26

requesting to add EPDM rubber ((C2H4)

(C3H6)y(C9H12)z; x=5134, y=2250, z=98)

to the List. According to the petition, the

taxable chemicals ethylene, propylene,

and butadiene constitute 97.41 percent by

weight of the materials used to produce

EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;

Bulletin No. 2025–41

x=5134, y=2250, z=98), based on the predominant method of production.

(a) Determination. Ethylene propylene diene (EPDM) rubber ((C2H4)x(C3H6)

(C9H12)z; x=5134, y=2250, z=98) is added

to the list of taxable substances under section 4672(a). Other pertinent information

is as follows:

(1) Predominant method of production:

The predominant method of producing

EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;

x=5134, y=2250, z=98) is copolymerization of ethylene and propylene with or

without a small amount of a non-conjugated diene.

(2) Stoichiometric material consumption equation:

5,134 C2H4 [ethylene] + 2,250 C3H6

[propylene] + 98 C4H6 [butadiene] +

98 C5H6 [cyclopentadiene] → (5,134

C2H4 + 2,250 C3H6 + 98 C9H12)

[EPDM]

(3) Reasons for the determination:

The EPDM rubber ((C2H4)x(C3H6)

(C9H12)z; x=5134, y=2250, z=98) petiy

tion was filed on May 1, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 21825)

on May 21, 2025. The Treasury Department and the IRS received one non-substantive written comment regarding the

effect of EPDM on the environment

and wildlife in response to the notice

of filing. The comment did not address

whether EPDM rubber ((C2H4)x(C3H6)

(C9H12)z; x=5134, y=2250, z=98) meets

the weight or value test under section

4672(a)(2)(B). A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals ethylene, propylene, and butadiene constitute more

than 20 percent by weight of the materials

used in the production of EPDM rubber

((C2H4)x(C3H6)y(C9H12)z; x=5134, y=2250,

z=98), based on the predominant method

of production. Therefore, the test in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

463

(5) Effective dates for addition of

EPDM rubber ((C2H4)x(C3H6)y(C9H12)z;

x=5134, y=2250, z=98) to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.45 per ton. The conversion factors

for the taxable chemicals used in the production of EPDM rubber ((C2H4)x(C3H6)

(C9H12)z; x=5134, y=2250, z=98) are 0.57

for ethylene, 0.38 for propylene, and 0.02

for butadiene. The tax rate is calculated

by adding the products of the conversion

factor for each taxable chemical and the

tax rate for that taxable chemical: ((0.57

x $9.74) + (0.38 x $9.74) + (0.02 x $9.74)

= $9.45).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.70.00

(ii) Schedule B number: 4002.70.0000

(iii) CAS number: 25034-71-3

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

23. Determination to Add Isodecyl

Alcohol to the List

Exxon Mobil Corporation, an exporter

of isodecyl alcohol, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add isodecyl alcohol to

the List. According to the petition, the

taxable chemical propylene constitutes

72.00 percent by weight of the materials

used to produce isodecyl alcohol, based

on the predominant method of production.

(a) Determination. Isodecyl alcohol

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of producing isodecyl alcohol is in an oxonation reaction.

Plasticizer alcohols, including isodecyl

alcohol, are derived from the oxo reaction

with branched olefins. Refinery-connected

October 6, 2025

polygas units generate many of these olefins as purified cuts or fractions.

The hydrogen used for these reactions are not produced from steam-methane reforming. The source of hydrogen

is from a Pox reactor, which feeds liquids, not methane. The Pox process is an

industrial process that converts hydrocarbons feeds into syngas (a combination of

hydrogen and carbon monoxide gas). The

hydrocarbon feed is in the liquid state. The

unit feeds a variety of liquid hydrocarbons

such as paraffins, olefins, and aromatics in

the C5-C20 range, obtained from the refinery pipestills and other chemicals units.

(2) Stoichiometric material consumption equation:

2.88 x 0.94 C3H6 [propylene] + 2.88

x 0.06 C5H10 [amylene] + CO [carbon monoxide] + 2 H2 [hydrogen] →

C10H22O [isodecyl alcohol]

(3) Reasons for the determination: The

isodecyl alcohol petition was filed on May

1, 2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

21129) on May 16, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemical propylene constitutes more than 20 percent by

weight of the materials used in the production of isodecyl alcohol, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of isodecyl alcohol to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

October 6, 2025

(6) Tax rate prescribed by the Secretary: $7.01 per ton. The conversion factor

for the propylene used in the production

of isodecyl alcohol is 0.72. The tax rate is

calculated by multiplying the conversion

factor by the tax rate for propylene: (0.72

x $9.74 = $7.01).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 68526-85-2

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 3823.70.60.00

(ii) Schedule B number: 3823.70.6000

24. Determination to Add Isodecyl

Benzoate to the List

Exxon Mobil Corporation, an exporter

of isodecyl benzoate, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add isodecyl benzoate to

the List. According to the petition, the

taxable chemicals propylene and toluene

constitute 69.10 percent by weight of the

materials used to produce isodecyl benzoate, based on the predominant method of

production.

(a) Determination. Isodecyl benzoate

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of producing

isodecyl benzoate is via esterification. The

isodecyl benzoate ester is made by reacting primary isodecyl (C10) alcohol with

benzoic acid. The ester is produced by

esterification of one mole of isodecyl C10

alcohol and one mole of benzoic acid in

the presence of a catalyst.

By using excess alcohol (up to 30%

molar excess of C10 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C – 250°C), while removing the

water formed.

Excess alcohol is distilled from the

ester by vacuum prior to neutralization

and recycled into subsequent batches.

The final ester is purified by neutralizing

464

with a base such as an aqueous solution of

sodium carbonate. The remaining excess

water is distilled off and the ester is then

filtered using filter agents. The degree of

purity of the ester has a minimum 99.0

wt%.

(2) Stoichiometric material consumption equation:

2.71 C3H6 [propylene] + 0.17 C5H10

[amylene] + CO [carbon monoxide] +

2 H2 [hydrogen] + C6H5CH3 [toluene]

+ 1.5 O2 [oxygen] → C17H26O2 [isodecyl benzoate] + 2 H2O [water]

(3) Reasons for the determination:

The isodecyl benzoate petition was

filed on May 1, 2025. The notice of

filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 21130) on

May 16, 2025. The Treasury Department and the IRS received no written

comments in response to the notice of

filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals propylene and

toluene constitute more than 20 percent

by weight of the materials used in the production of isodecyl benzoate, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of isodecyl benzoate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.60 per ton. The conversion factors

for the taxable chemicals used in the production of isodecyl benzoate are 0.43 for

propylene and 0.35 for toluene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

Bulletin No. 2025–41

chemical and the tax rate for that taxable

chemical: ((0.43 x $9.74) + (0.35 x $9.74)

= $7.60).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers: Not applicable.

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2916.31.50.00

(ii) Schedule B number: 2916.31.0002

(iii) CAS number: 131298-44-7

25. Determination to Add Isooctyl

Alcohol to the List

Exxon Mobil Corporation, an exporter

of isooctyl alcohol, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add isooctyl alcohol to the

List. According to the petition, the taxable chemical propylene constitutes 68.10

percent by weight of the materials used

to produce isooctyl alcohol, based on the

predominant method of production.

(a) Determination. Isooctyl alcohol

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production: The predominant method of producing isooctyl alcohol is in an oxonation

reaction. Plasticizer alcohols, including

isooctyl alcohol, are derived from the oxo

reaction with branched olefins. Refinery-connected polygas units generate

many of these olefins as purified cuts or

fractions. For example, isooctyl alcohol

is produced from heptene, which is an

isomeric mixture of C7 olefins that are

derived from the reaction of propylene

and butylenes. The extent of branching

in heptane depends on the reaction conditions and feedstock ratio at the polygas

units. Since these conditions are variable,

the specifications of the alcohol product

may vary among producers.

The hydrogen used for these reactions

are not produced from steam-methane

reforming. The source of hydrogen is

from POx reactor, which feeds liquids, not

methane. The POx process is an industrial

process that converts hydrocarbons feeds

into syngas (a combination of hydrogen

and carbon monoxide gas). The hydrocarbon feed is in the liquid state. The unit

Bulletin No. 2025–41

feeds a variety of liquid hydrocarbons

such as paraffins, olefins, and aromatics

in the C5-C20 range, obtained from the

refinery pipestills and other chemicals

units.

(2) Stoichiometric material consumption equation:

2.24 x 0.94 C3H6 [propylene] + 2.24 x

0.06 C5H10 [amylene] + CO [carbon

monoxide] + 2 H2 [hydrogen] →

C8H18O [isooctyl alcohol]

(3) Reasons for the determination:

The isooctyl alcohol petition was filed

on May 1, 2025. The notice of filing

summarizing the petition and requesting comments was published in the Federal Register (90 FR 21126) on May 16,

2025. The Treasury Department and the

IRS received one non-substantive written comment regarding the importance

of evaluating the data in response to the

notice of filing. The comment did not

address whether isooctyl alcohol meets

the weight or value test under section

4672(a)(2)(B). A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemical propylene constitutes more than 20 percent by

weight of the materials used in the production of isooctyl alcohol, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of

isooctyl alcohol to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $6.62 per ton. The conversion factor

for the propylene used in the production

of isooctyl alcohol is 0.68. The tax rate is

calculated by multiplying the conversion

465

factor by the tax rate for propylene: (0.68

x $9.74 = $6.62).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2905.16.00.50

(ii) Schedule B number: 2905.16.0050

(iii) CAS number: 68526-83-0

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

26. Determination to Add Linear Nonyl

Phthalate to the List

Exxon Mobil Corporation, an exporter

of linear nonyl phthalate, submitted a petition in accordance with Rev. Proc. 2022-26

requesting to add linear nonyl phthalate to

the List. According to the petition, the taxable chemicals ethylene and orthoxylene

(an isomer of xylene) constitute 67.40 percent by weight of the materials used to produce linear nonyl phthalate, based on the

predominant method of production.

(a) Determination. Linear nonyl

phthalate is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing

linear nonyl phthalate is via esterification.

The linear nonyl phthalate di-ester is

made by reacting a mix of primary C9

alcohol with phthalic anhydride. The ester

is produced by esterification of two moles

of a linear C9 alcohol with one mole of

phthalic anhydride in the presence of an

acidic catalyst.

By using excess alcohol (up to 25%

molar excess of C9 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the di-ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C – 250°C), while removing the

water formed.

The final ester is purified by neutralizing with a base such as an aqueous solution of sodium carbonate. Then excess

alcohol is distilled off using steam/nitrogen stripping after neutralization. The

remaining excess water is distilled off and

the ester is then filtered using filter agents.

October 6, 2025

The degree of purity of the ester is up

to > 99.5 wt%. The overall formula is

C26H42O4 and the molecular weight is 418

g/mole, based on an average carbon number of the alkyl groups, with 9 carbons

being the predominant number.

The linear C9 alcohol is obtained

through hydroformylation of octene.

Octene is obtained through ethylene

oligomerization. Hydroformylation is the

reaction of octene, at high pressure and

temperature in the presence of a catalyst,

with syngas (a mixture of carbon monoxide and hydrogen). An alcohol with

one carbon atom higher versus the starting olefin is obtained, hence octene gives

nonanol. The hydroformylation induces

0.3 branches per molecule predominantly

on the 2-postion carbon of the alcohol.

phthalic anhydride is obtained through air

oxidation of o.xylene.

(2) Stoichiometric material consumption equation:

8 C2H4 [ethylene] + 2 CO [carbon

monoxide] + 4 H2 [hydrogen] + C8H10

[orthoxylene] + 3 O2 [oxygen] →

C26H42O4 [linear nonyl phthalate] + 4

H2O [water]

(3) Reasons for the determination:

The linear nonyl phthalate petition was

filed on April 8, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals ethylene and orthoxylene (an isomer of

xylene) constitute more than 20 percent

by weight of the materials used in the

production of linear nonyl phthalate,

based on the predominant method of

production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of linear nonyl phthalate to the List:

October 6, 2025

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.69 per ton. The conversion factors

for the taxable chemicals used in the production of linear nonyl phthalate are 0.54

for ethylene and 0.25 for xylene. The tax

rate is calculated by adding the products

of the conversion factor for each taxable

chemical and the tax rate for that taxable

chemical: ((0.54 x $9.74) + (0.25 x $9.74)

= $7.69).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 68515-45-7

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2917.33.00.50

(ii) Schedule B number: 2917.33.0050

27. Determination to Add Linear Nonyl

Undecyl Phthalate to the List

Exxon Mobil Corporation, an exporter

of linear nonyl undecyl phthalate, submitted a petition in accordance with Rev.

Proc. 2022-26 requesting to add linear

undecyl phthalate to the List. According to the petition, the taxable chemicals

ethylene and orthoxylene (an isomer

of xylene) constitute 69.14 percent by

weight of the materials used to produce

linear nonyl undecyl phthalate, based on

the predominant method of production.

(a) Determination. Linear nonyl undecyl phthalate is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing linear nonyl undecyl phthalate is via

esterification. The linear nonyl undecyl

phthalate di-ester is made by reacting a

mix of primary C9 alcohol and primary

C11 alcohol with phthalic anhydride. The

ester is produced by esterification of one

mole of a linear C9 alcohol and one mole

of a linear C11 alcohol mix with one mole

of phthalic anhydride in the presence of

466

an acidic catalyst. By using excess alcohol (up to 25% molar excess of the alcohol

mix) and removing the water, the equilibrium is shifted towards the formation of

the di-ester. The reactants are charged into

a reactor and heated up. The reaction rate

is accelerated by using, for example, tetra-n-butyl titanate introduced at high temperature (140°C – 250°C), while removing the water formed. The final ester is

purified by neutralizing with a base such

as an aqueous solution of sodium carbonate. Then excess alcohol is distilled off

using steam/nitrogen stripping after neutralization. The remaining excess water is

distilled off and the ester is then filtered

using filter agents. The degree of purity of

the ester is up to >99.5 wt%.

The overall formula is C28H46O4 and

the molecular weight is 446 g/mole, based

on an average carbon number of the alkyl

groups, which are C9 and C11 carbons.

The linear C9/C11 alcohols are obtained

through hydroformylation of octene/

decene. octene/decene is obtained through

ethylene oligomerization. Hydroformylation is the reaction of octene/decene,

at high pressure and temperature in the

presence of a catalyst, with syngas (a mixture of carbon monoxide and hydrogen).

An alcohol with one carbon atom higher

versus the starting olefin is obtained,

hence octene/decene gives nonanol/undecanol. The hydroformylation induces 0.3

branches per molecule predominantly

on the 2-postion carbon of the alcohol.

Phthalic anhydride is obtained through air

oxidation of orthoxylene.

The hydrogen used for these reactions

is not produced from steam-methane

reforming; the source is from a POx reactor, which feeds liquids, not methane. The

POx process is an industrial process that

converts hydrocarbons feeds into syngas

(a combination of hydrogen and carbon

monoxide gas). The hydrocarbon feed

is in the liquid state; it does not feed gas

(such as methane) or solids. The unit feeds

a variety of liquid hydrocarbons such as

paraffins, olefins, and aromatics in the

C5-C20 range, obtained from the refinery

pipestills and other chemicals units.

(2) Stoichiometric material consumption equation:

9 C2H4 [ethylene] + 2 CO [carbon

monoxide] + 4 H2 [hydrogen] + C8H10

Bulletin No. 2025–41

[orthoxylene] + 3 O2 [oxygen] →

C28H46O4 [linear nonyl undecyl phthalate] + 4 H2O [water]

(3) Reasons for the determination:

The linear nonyl undecyl phthalate

petition was filed on April 8, 2025. The

notice of filing summarizing the petition

and requesting comments was published

in the Federal Register (90 FR 20553) on

May 14, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemicals ethylene and

orthoxylene (an isomer of xylene) constitute more than 20 percent by weight

of the materials used in the production of

linear nonyl undecyl phthalate, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of linear nonyl undecyl phthalate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.89 per ton. The conversion factors

for the taxable chemicals used in the production of linear nonyl undecyl phthalate

are 0.57 for ethylene and 0.24 for xylene.

The tax rate is calculated by adding the

products of the conversion factor for each

taxable chemical and the tax rate for that

taxable chemical: ((0.57 x $9.74) + (0.24

x $9.74) = $7.89)

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 3812.20.10.00

(ii) Schedule B number: 3812.20.0000

(iii) CAS number: 68515-43-5

Bulletin No. 2025–41

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

28. Determination to Add Linear

Undecyl Phthalate to the List

Exxon Mobil Corporation, an exporter

of linear undecyl phthalate, submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add linear undecyl phthalate to the List. According to the

petition, the taxable chemicals ethylene

and orthoxylene (an isomer of xylene)

constitute 70.72 percent by weight of the

materials used to produce linear undecyl phthalate, based on the predominant

method of production.

(a) Determination. Linear undecyl

phthalate is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production: The predominant method of producing linear undecyl phthalate di-ester

is by reacting a mix of primary C11 alcohol with phthalic anhydride. The ester is

produced by esterification of two moles

of a linear C11 alcohol with one mole of

phthalic anhydride in the presence of an

acidic catalyst.

By using excess alcohol (up to 25%

molar excess of C11 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the di-ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C – 250°C), while removing the

water formed.

The final ester is purified by neutralizing with a base such as an aqueous solution of sodium carbonate. Then excess

alcohol is distilled off using steam/nitrogen stripping after neutralization. The

remaining excess water is distilled off

and the ester is then filtered using filter

agents.

The degree of purity of the ester is

up to >99.5 wt%. The overall formula is

C30H50O4 and the molecular weight is 474

g/mole, based on an average carbon number of the alkyl groups, with 11 carbons

being the predominant number.

The linear C11 alcohol is obtained

through hydroformylation of decene.

467

Decene is obtained through ethylene

oligomerization. Hydroformylation is the

reaction of decene, at high pressure and

temperature in the presence of a catalyst,

with syngas (a mixture of carbon monoxide and hydrogen). An alcohol with one

carbon atom higher versus the starting

olefin is obtained, hence decene gives

undecanol. The hydroformylation induces

0.3 branches per molecule predominantly

on the 2-position carbon of the alcohol.

Phthalic anhydride is obtained through air

oxidation of o.xylene.

(2) Stoichiometric material consumption equation:

10 C2H4 [ethylene] + 2 CO [carbon

monoxide] + 4 H2 [hydrogen] + C8H10

[orthoxylene] + 3 O2 [oxygen] →

C30H50O4 [linear undecyl phthalate] +

4 H2O [water]

(3) Reasons for the determination:

The linear undecyl phthalate petition was

filed on April 8, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemicals ethylene and orthoxylene (an isomer of

xylene) constitute more than 20 percent

by weight of the materials used in the

production of linear undecyl phthalate,

based on the predominant method of

production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of linear undecyl phthalate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

October 6, 2025

(6) Tax rate prescribed by the Secretary: $7.89 per ton. The conversion factors for the taxable chemicals used in the

production of linear undecyl phthalate

are 0.59 for ethylene and 0.22 for xylene.

The tax rate is calculated by adding the

products of the conversion factor for each

taxable chemical and the tax rate for that

taxable chemical: ((0.59 x $9.74) + (0.22

x $9.74) = $7.89)

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers: Not applicable.

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2917.33.00.50

(ii) Schedule B number: 2917.33.00.50

(iii) CAS number: 3648-20-2

29. Determination to Add Linear Nonyl

Tri-mellitate to the List

Exxon Mobil Corporation, an exporter of

linear nonyl tri-mellitate, submitted a petition in accordance with Rev. Proc. 2022-26

requesting to add linear nonyl tri-mellitate

to the List. According to the petition, the

taxable chemical ethylene constitutes 53.90

percent by weight of the materials used to

produce linear nonyl tri-mellitate, based on

the predominant method of production.

(a) Determination. Linear nonyl

tri-mellitate is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production:

The predominant method of production of

linear nonyl tri-mellitate is using an esterification reaction. The linear nonyl tri-mellitate tri-ester is made by reacting primary

C9 alcohol with trimellitic anhydride. The

ester is produced by esterification of three

moles of a linear C9 alcohol and one mole

of trimellitic anhydride in the presence of

an acidic catalyst.

By using excess alcohol (up to 30%

molar excess of C9 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the tri-ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C – 250°C), while removing the

water formed.

October 6, 2025

Excess alcohol is distilled from the

ester by vacuum prior to neutralization

and recycled into subsequent batches.

The final ester is purified by neutralizing

with a base such as an aqueous solution of

sodium carbonate. The remaining excess

water is distilled off and the ester is then

filtered using filter agents.

The degree of purity of the ester has a

minimum 99.0 wt%. The overall formula

is C36H60O6 and the molecular weight is

589 g.mol-1, based on the carbon numbers

of the alkyl groups, with 9 carbons being

the predominant number and the average

(>97% C9). The alkyl groups typically

have methyl- or ethyl- branching, with on

average 0.3 branches per molecule typically found on the second carbon of the

alkyl chain closest to the aromatic ring.

The linear C9 alcohol is obtained

through hydroformylation of octene.

Octene is obtained through ethylene

oligomerization. Hydroformylation is

the reaction of ctene at high pressure and

temperature in the presence of a catalyst

with syngas (a mixture of carbon monoxide and hydrogen). An alcohol with

one carbon atom higher versus the starting olefin is obtained, hence octene gives

nonanol. The hydroformylation induces

0.3 branches per molecule predominantly

on the two-position carbon of the alcohol.

Trimellitic anhydride is obtained through

air oxidation of 1,2,4-trimethylbenzene.

(2) Stoichiometric material consumption equation:

12 C2H4 [ethylene] + 3 CO [carbon

monoxide] + 6 H2 [hydrogen] +

C9H4O5 [trimellitic anhydride] →

C36H60O6 [linear nonyl tri-mellitate] +

2 H2O [water]

(3) Reasons for the determination:

The linear nonyl tri-mellitate petition was

filed on May 1, 2025. The notice of filing

summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

468

and other information in the petition

shows that the taxable chemical ethylene constitutes more than 20 percent

by weight of the materials used in the

production of linear nonyl tri-mellitate,

based on the predominant method of

production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of linear nonyl tri-mellitate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $5.55 per ton. The conversion factor

for the ethylene used in the production of

linear nonyl tri-mellitate is 0.57. The tax

rate is calculated by multiplying the conversion factor by the tax rate for ethylene:

(0.57 x $9.74 = $5.55).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2917.39.20.00

(ii) Schedule B number: 2917.39.2000

(iii) CAS number: 220582-53-6

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

30. Determination to Add Neo

Decanoic Acid to the List

Exxon Mobil Corporation, an exporter

of neo decanoic acid, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add neo decanoic acid to the

List. According to the petition, the taxable

chemical propylene constitutes 66.20 percent by weight of the materials used to

produce neo decanoic acid, based on the

predominant method of production.

(a) Determination. Neo decanoic acid

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of production of

neo decanoic acid is Koch synthesis.

Bulletin No. 2025–41

(2) Stoichiometric material consumption equation:

2.88 x 0.94 C3H6 [propylene] + 2.88

x 0.06 C5H10 [amylene] + CO [carbon

monoxide] + H2O [water] → C10H20O2

[neo decanoic acid]

(3) Reasons for the determination:

The neo decanoic acid petition was filed

on May 1, 2025. The notice of filing

summarizing the petition and requesting comments was published in the Federal Register (90 FR 21824) on May 21,

2025. The Treasury Department and the

IRS received one non-substantive written

comment cautioning against the danger

of producing the substance in response to

the notice of filing. The comment did not

address whether neo decanoic acid meets

the weight or value test under section

4672(a)(2)(B). A public hearing was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemical propylene constitutes more than 20 percent by weight of

the materials used in the production of neo

decanoic acid, based on the predominant

method of production. Therefore, the test

in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of neo

decanoic acid to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $6.43 per ton. The conversion factor

for the propylene used in the production of

neo decanoic acid is 0.66. The tax rate is

calculated by multiplying the conversion

factor by the tax rate for propylene: (0.66

x $9.74 = $6.43).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 26896-20-8

Bulletin No. 2025–41

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2915.90.18.00

(ii) Schedule B number: 2915.90.0000

31. Determination to Add Neo

Pentanoic Acid to the List

Exxon Mobil Corporation, an exporter

of neo pentanoic acid, submitted a petition in accordance with Rev. Proc. 202226 requesting to add neo pentanoic acid

to the List. According to the petition, the

taxable chemical isobutylene (an isomer

of butylene) constitutes 54.90 percent by

weight of the materials used to produce

neo pentanoic acid, based on the predominant method of production.

(a) Determination. Neo pentanoic acid

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production: The predominant method of producing neo pentanoic acid is via Koch synthesis. Isobutylene is reacted with carbon

monoxide at >1000 psig and a highly

acidic (Lewis acid) catalyst (Koch reaction) in a continuous, stirred tank reactor. The acid is sent to a distillation tower

finishing section. Light rejects (paraffins,

olefins, and light acids) are removed,

prime neopentanoic acid is recovered

at high purity (>99.7 wt%), and acidic

byproducts removed.

(2) Stoichiometric material consumption equation:

C4H8 [isobutylene] + CO [carbon monoxide] + H2O [water]→ C5H10O2 [neo

pentanoic acid]

(3) Reasons for the determination: The

neo pentanoic acid petition was filed on

May 1, 2025. The notice of filing summarizing the petition and requesting

comments was published in the Federal

The Treasury Department and the IRS

received no written comments in response

to the notice of filing. A public hearing

was neither requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

469

other information in the petition shows

that the taxable chemical isobutylene (an

isomer of butylene) constitutes more than

20 percent by weight of the materials

used in the production of neo pentanoic

acid, based on the predominant method of

production. Therefore, the test in section

4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of neo

pentanoic acid to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $5.36 per ton. The conversion factor

for the butylene used in the production of

neo pentanoic acid is 0.55. The tax rate is

calculated by multiplying the conversion

factor by the tax rate for butylene: (0.55 x

$9.74 = $5.36)

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2915.60.50.00

(ii) Schedule B number: 2915.60.0000

(iii) CAS number: 75-98-9

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

32. Determination to Add Nonene to

the List

Exxon Mobil Corporation, an exporter

of nonene, submitted a petition in accordance with Rev. Proc. 2022-26 requesting

to add nonene to the List. According to

the petition, the taxable chemical propylene constitutes 90.50 percent by weight

of the materials used to produce nonene,

based on the predominant method of production.

(a) Determination. Nonene is added to

the list of taxable substances under section

4672(a). Other pertinent information is as

follows:

(1) Predominant method of production:

The predominant method of producing

nonene is oligomerization.

October 6, 2025

Nonene (C9H18) and tetramer (C12H24)

are olefins that are obtained by oligomerization of feedstock that contains propylene. Each product actually contains

several isomeric olefins with varying

degrees of branching and different positions of the olefinic double bond. Refinery-generated propylene is of sufficient

quality to be used as the feedstock material. The most common process initiates

the reaction with a supported phosphoric

acid catalyst at temperatures ranging

from 120°C to 225°C. Reaction temperature and feed composition determine the

range of olefins in a given product stream.

If the feedstock is a propylene-rich C3

stream, C9 and C12 olefins are the dominant products. Some processes that use

a mixed C3/C4 feed generate a spectrum

of products that also includes heptene

(C7) and octene (C8). Distillation separates the mix into the desired product

fractions. Nonene and tetramer have

distillation ranges of 127°C-149°C and

182°C-215°C, respectively. Assuming

83 percent and 79 percent of theoretical yield for production of nonene and

tetramer, respectively, 1.21 and 1.27

units of propylene are consumed per unit

of nonene and tetramer produced, respectively.

(2) Stoichiometric material consumption equation:

2.88 x 0.94 C3H6 [propylene] + 2.88

x 0.06 C5H10 [amylene] → C9H18

[nonene]

(3) Reasons for the determination:

The nonene petition was filed on May 1,

2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

21826) on May 21, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemical propyl-

ene constitutes more than 20 percent by

weight of the materials used in the production of nonene, based on the predominant method of production. Therefore,

the test in section 4672(a)(2)(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of nonene to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $8.77 per ton. The conversion factor

for the propylene used in the production of

nonene is 0.90. The tax rate is calculated

by multiplying the conversion factor by

the tax rate for propylene: (0.90 x $9.74

= $8.77).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 68526-55-65

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 2901.29.50.00

(ii) Schedule B number: 2901.29.6000

33. Determination To Add Regular

Butyl Rubber ((C4H8)x(C5H8)y; x=7036,

y=88) to the List

Exxon Mobil Corporation, an exporter

of regular butyl rubber ((C4H8)x(C5H8)

; x=7036, y=88), submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add regular butyl rubber

((C4H8)x(C5H8)y; x=7036, y=88) to the

List. According to the petition, the taxable

chemical isobutylene (an isomer of butylene) constitutes 98.50 percent by weight

of the materials used to produce regular

butyl rubber, based on the predominant

method of production.

(a) Determination. Regular butyl rubber ((C4H8)x(C5H8)y; x=7036, y=88) is

added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of producing regular butyl rubber ((C4H8)x(C5H8)y; x=7036,

y=88) is via cationic copolymerization of

isobutylene with isoprene in the presence

of a catalyst. The catalyst system used is

typically composed of aluminum chloride,

boron trifluoride or similar with an initiator dissolved in a methyl chloride solvent.

Monomer feed of isobutylene and isoprene

dissolved in a methyl chloride solvent are

fed to a reactor operated at approximately

‑100⁰C to control the rapid exothermic

polymerization reaction generating a high

molecular weight regular butyl rubber

polymer. To obtain this high molecular

weight polymer, it is necessary for the feed

monomers to be as pure as possible as well

as ensuring that the feed system stays as

dry as possible. The methyl chloride and

unreacted monomers are flashed overhead

and recycled back to the feed system while

the polymer is precipitated out as a solid

which is baled and packaged.

(2) Stoichiometric material consumption equation:

7036 C4H8 [isobutylene] + 88 C5H8

[isoprene] → [7036 C4H8 + 88 C5H8]

[butyl rubber]

(3) Reasons for the determination:

The regular butyl rubber ((C4H8)x(C5H8)y;

x=7036, y=88) petition was filed on April

8, 2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

20347) on May 13, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemical isobutylene (an

isomer of butylene) constitutes more than

20 percent by weight of the materials used

in the production of regular butyl rubber

((C4H8)x(C5H8)y; x=7036, y=88), based on

The Notice of Filing for propylene erroneously stated that the CAS number is “68526-55-63.” This error is corrected here.

October 6, 2025

470

Bulletin No. 2025–41

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of regular butyl rubber ((C4H8)x(C5H8)y; x=7036,

y=88)to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $9.64 per ton. The conversion factor

for the butylene used in the production

of regular butyl rubber ((C4H8)x(C5H8)

y; x=7036, y=88) is 0.99. The tax rate is

calculated by multiplying the conversion

factor by the tax rate for butylene: (0.99 x

$9.74 = $9.64).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 4002.31.0000

(ii) Schedule B number: 4002.31.0000

(iii) CAS number: 9010-85-9

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

34. Determination to Add Tridecyl

Alcohol to the List

Exxon Mobil Corporation, an exporter

of tridecyl alcohol, submitted a petition

in accordance with Rev. Proc. 2022-26

requesting to add tridecyl alcohol to the

List. According to the petition, the taxable chemical propylene constitutes 75.90

percent by weight of the materials used to

produce tridecyl alcohol, based on the predominant method of production.

(a) Determination. Tridecyl alcohol

is added to the list of taxable substances

under section 4672(a). Other pertinent

information is as follows:

(1) Predominant method of production:

The predominant method of producing tridecyl alcohol is oxonation.

Tridecyl alcohol is derived from the

oxo reaction with branched olefins. Refinery-connected polygas units generate

Bulletin No. 2025–41

many of these olefins as purified cuts or

fractions.

Most commercial plants for hydroformylation of higher olefins use only

cobalt hydrocarbonyl or modified

cobalt-phosphine catalysts. Separation

of Rh catalysts from higher aldehydes or

alcohols is more difficult and expensive.

In most cases for the plasticizer and detergent alcohol ranges (C6-C15), producers

hydrogenate the aldehydes, which have no

commercial significance, to alcohols.

(2) Stoichiometric material consumption equation:

3.85 x 0.94 C3H6 [propylene] + 3.85

x 0.06 C5H10 [amylene] + CO [carbon monoxide] + 2 H2 [hydrogen] →

C13H28O [tridecyl alcohol]

(3) Reasons for the determination: The

tridecyl alcohol petition was filed on May

1, 2025. The notice of filing summarizing

the petition and requesting comments was

published in the Federal Register (90 FR

21824) on May 21, 2025. The Treasury

Department and the IRS received no written comments in response to the notice

of filing. A public hearing was neither

requested nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation

and other information in the petition

shows that the taxable chemical propylene constitutes more than 20 percent by

weight of the materials used in the production of tridecyl alcohol, based on

the predominant method of production.

Therefore, the test in section 4672(a)(2)

(B) is satisfied.

(4) Date of determination: September

15, 2025.

(5) Effective dates for addition of tridecyl alcohol to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $7.40 per ton. The conversion factor

for the propylene used in the production

471

of tridecyl alcohol is 0.76. The tax rate is

calculated by multiplying the conversion

factor by the tax rate for propylene: (0.76

x $9.74 = $7.40).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

number: CAS number: 68526-86-3

(2) The Secretary is unable to confirm the following proposed classification

numbers:

(i) HTSUS number: 3823.70.60.00

(ii) Schedule B number: 3823.70.6000

35. Determination to Add Tri-isononyl

Tri-mellitate to the List

Exxon Mobil Corporation, an exporter

of tri-isononyl tri-mellitate, submitted

a petition in accordance with Rev. Proc.

2022-26 requesting to add tri-isononyl

tri-mellitate to the List. According to the

petition, the taxable chemical propylene

constitutes 47.30 percent by weight of

the materials used to produce tri-isononyl

tri-mellitate, based on the predominant

method of production.

(a)

Determination.

Tri-isononyl

tri-mellitate is added to the list of taxable

substances under section 4672(a). Other

pertinent information is as follows:

(1) Predominant method of production:

The predominant method of producing triisononyl tri-mellitate is via esterification.

This process can be readily carried

out in heated kettles with agitation and

provision for water takeoff. Esterification catalysts (e.g., sulfuric acid or p-toluenesulfonic acid) speed the reaction

and are neutralized, washed, and then

removed. The purity requirements for

commercial plasticizers are very high;

phthalate esters are usually colorless

and are mostly odorless. In the case of

phthalates, the esterification is carried

out through the reaction of phthalic

anhydride and 2-ethylhexanol to produce

dioctyl phthalate (DOP).

This reaction usually requires an

excess of alcohol, which is readily recycled. Analogous syntheses yield aliphatic

dicarboxylic acid esters, benzoates, and

trimellitates.

The tri-isononyl tri-mellitate tri-ester is

made by reacting primary isononyl (C9)

alcohol with trimellitic anhydride. The

ester is produced by esterification of three

October 6, 2025

moles of isononyl C9 alcohol and one

mole of trimellitic anhydride in the presence of a catalyst.

By using excess alcohol (up to 30%

molar excess of C9 alcohol) and removing the water, the equilibrium is shifted

towards the formation of the tri-ester. The

reactants are charged into a reactor and

heated up. The reaction rate is accelerated by using, for example, tetra-n-butyl

titanate introduced at high temperature

(140°C-250°C), while removing the water

formed.

Excess alcohol is distilled from the

ester by vacuum prior to neutralization

and recycled into subsequent batches.

The final ester is purified by neutralizing

with a base such as an aqueous solution of

sodium carbonate. The remaining excess

water is distilled off and the ester is then

filtered using filter agents. The degree of

purity of the ester has a minimum 99.0

wt%.

(2) Stoichiometric material consumption equation:

7.22 C3H6 [propylene] + 0.46 C5H10

[amylene] + 3 CO [carbon monoxide]

+ 6 H2 [hydrogen] + C9H4O5 [trimellitic anhydride] → C36H60O6 [triisononyl trimellitate] + 2 H2O [water]

(3) Reasons for the determination:

The tri-isononyl tri-mellitate petition

was filed on May 1, 2025. The notice

of filing summarizing the petition and

requesting comments was published in

the Federal Register (90 FR 21827) on

May 21, 2025. The Treasury Department

and the IRS received no written comments in response to the notice of filing.

A public hearing was neither requested

nor held.

The Secretary followed the process

in section 4672(a)(2)(B) in making this

determination. A review of the stoichiometric material consumption equation and

other information in the petition shows

that the taxable chemical propylene constitutes more than 20 percent by weight

of the materials used in the production of

tri-isononyl tri-mellitate, based on the predominant method of production. Therefore, the test in section 4672(a)(2)(B) is

satisfied.

(4) Date of determination: September

15, 2025.

October 6, 2025

(5) Effective dates for addition of triisononyl tri-mellitate to the List:

(i) Effective date for purposes of the

section 4671 tax (see section 11.01 of Rev.

Proc. 2022-26): January 1, 2026

(ii) Effective date for purposes of refund

claims under section 4662(e) (see sections

11.02 and 11.03 of Rev. Proc. 2022-26, as

modified by section 3 of Rev. Proc. 202320): July 1, 2022

(6) Tax rate prescribed by the Secretary: $5.06 per ton. The conversion factor

for the propylene used in the production of

tri-isononyl tri-mellitate is 0.52. The tax

rate is calculated by multiplying the conversion factor by the tax rate for propylene: (0.52 x $9.74 = $5.06).

(b) Classification numbers.

(1) The Secretary has no basis to object

to the following proposed classification

numbers:

(i) HTSUS number: 2917.39.20.00

(ii) Schedule B number: 2917.39.2000

(iii) CAS number: 53894-23-8

(2) The Secretary is unable to confirm the following proposed classification

numbers: Not applicable.

36. Determination to Add Diisobutylene to the List

TPC Group, Inc., an exporter of

di-isobutylene, submitted a petition in

accordance with Rev. Proc. 2022-26

requesting to add di-isobutylene to the

List. According to the petition, the taxable

chemical isobutylene (an isomer of butyle

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