Process for methylating aromatic hydrocarbons

Patent metadata

Field	Value
Publication number	US-10696608-B2
Application number	US-201716336034-A
Country	US
Kind code	B2
Filing date	Sep 12, 2017
Priority date	Oct 6, 2016
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

In a process for producing paraxylene, a hydrocarbon feedstock comprising benzene and/or toluene is contacted with an alkylating reagent comprising methanol and/or dimethyl ether in an alkylation reaction zone under alkylation conditions in the presence of an alkylation catalyst to produce an alkylated product comprising xylenes. The alkylation catalyst comprises a molecular sieve having a Constraint Index ≤5, and the alkylation conditions comprise a temperature less than 500° C. At least part of the alkylated product is supplied to a paraxylene recovery unit to recover paraxylene and produce a paraxylene-depleted stream, which is then contacted with a xylene isomerization catalyst under conditions effective to isomerize xylenes in the paraxylene-depleted stream and produce an isomerized stream having a higher concentration of paraxylene than the paraxylene-depleted stream. At least part of the isomerized stream is then recycled to the paraxylene recovery unit to recover the paraxylene therein.

First claim

The invention claimed is:

1. A process for producing paraxylene, the process comprising:
(a1) contacting a hydrocarbon feedstock comprising benzene and/or toluene with an alkylating reagent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone under alkylation conditions in the presence of alkylation catalyst to produce an alkylated product comprising xylenes, wherein the alkylation catalyst comprises a molecular sieve having a Constraint Index less than or equal to 5, and wherein the alkylation conditions comprise a temperature less than 500° C. and a pressure from 700 kPa-a to 7000 kPa-a;
(b1) supplying at least part of the alkylated product to a paraxylene recovery unit to recover paraxylene from the alkylated product and produce a paraxylene-depleted stream;
(c1) contacting the paraxylene-depleted stream with a xylene isomerization catalyst under conditions effective to isomerize xylenes in the paraxylene-depleted stream and produce an isomerized stream having a higher concentration of paraxylene than the paraxylene-depleted stream; and
(d1) recycling at least part of the isomerized stream to the paraxylene recovery unit to recover paraxylene from the isomerization stream.

2. The process of claim 1 , wherein the alkylation conditions comprise a temperature of at least 250° C.

3. The process of claim 2 , wherein the alkylation conditions comprise a temperature from 300° C. to 450° C.

4. The process of claim 1 , wherein the alkylation catalyst comprises at least one molecular sieve selected from the MWW, MTW, and BEA framework types.

5. The process of claim 4 , wherein the alkylation catalyst comprises at least one molecular sieve selected from the group consisting of MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, MIT-1, and mixtures thereof.

6. The process of claim 5 , wherein the at least one alkylation reaction zone comprises a fixed bed of the alkylation catalyst.

7. The process of claim 6 , wherein the hydrocarbon feedstock comprises a refinery fraction from which aliphatic hydrocarbons have been extracted.

8. The process of claim 7 , wherein the alkylated product also comprises benzene and/or toluene and the process further comprises:
(e1) separating at least part of the benzene and/or toluene from the alkylated product prior to the supplying step (b1).

9. The process of claim 8 , wherein at least part of the benzene and/or toluene separated from the alkylated product in step (e1) is recycled to the contacting step (a1).

10. The process of claim 8 , wherein at least part of the benzene and/or toluene separated from the alkylated product in step (e1) is supplied to a transalkylation reaction zone which also receives a feed comprising C 9+ aromatic hydrocarbons.

11. The process of claim 10 , wherein the alkylated product also comprises C 9+ aromatic hydrocarbons and the process further comprises:
(f1) separating at least part of the C 9+ aromatic hydrocarbons from the alkylated product prior to the supplying step (b1); and
(g1) supplying at least part of the C 9+ aromatic hydrocarbons separated from the alkylated product in step (f1) to the transalkylation reaction zone.

12. A process for producing xylenes, the process comprising:
(a2) providing a hydrocarbon feedstock comprising C 6+ aliphatic and aromatic hydrocarbons including benzene and/or toluene; and
(b2) contacting at least part of the hydrocarbon feedstock with an alkylating reagent comprising methanol and/or dimethyl ether in at least one alkylation reaction zone under alkylation conditions in the presence of alkylation catalyst to produce an alkylated product comprising xylenes, wherein the alkylation catalyst comprises a molecular sieve having a Constraint Index less than or equal to 5, and wherein the alkylation conditions comprise a temperature less than 500° C. and a pressure from 700 kPa-a to 7000 kPa-a.

13. The process of claim 12 , wherein the alkylation conditions comprise a temperature of at least 250° C.

14. The process of claim 13 , wherein the alkylation conditions comprise a temperature from 300 to 450° C.

15. The process of claim 12 , wherein the alkylation catalyst comprises at least one molecular sieve selected from the MWW, MTW, and BEA framework types.

16. The process of claim 15 , wherein the alkylation catalyst comprises at least one molecular sieve selected from the group consisting of MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, EMM-10, EMM-12, EMM-13, UZM-8, UZM-8HS, UZM-37, MIT-1, and mixtures thereof.

17. The process of claim 16 , wherein the at least one alkylation reaction zone comprises a fixed bed of the alkylation catalyst.

18. The process of claim 17 , wherein the hydrocarbon feedstock comprises a reformate and/or a steam cracked naphtha fraction.

19. The process of claim 18 and further comprising:
(c2) fractionating at least part of the alkylated product to separate a first fraction comprising C 6+ aliphatic hydrocarbons.

20. The process of claim 19 , wherein the C 6+ aliphatic hydrocarbons comprise benzene and/or toluene co-boilers.

21. The process of claim 20 and further comprising:
(d2) fractionating at least part of the alkylated product to separate a second fraction comprising xylenes;
(e2) supplying at least part of the second fraction to a paraxylene recovery unit to recover paraxylene from the second fraction and produce a paraxylene-depleted stream;
(f2) contacting at least part of the paraxylene-depleted stream with a xylene isomerization catalyst in a xylene isomerization zone under conditions effective to isomerize xylenes in the paraxylene-depleted stream and produce an isomerized stream having a higher concentration of paraxylene than the paraxylene-depleted stream; and
(g2) recycling at least part of the isomerized stream to the paraxylene recovery unit to recover paraxylene from the isomerization stream.

22. The process of claim 21 , wherein the alkylated product comprises C 9+ aromatic hydrocarbons and the process further comprises:
(h2) fractionating at least part of the alkylated product to separate a third fraction comprising C9+ aromatic hydrocarbons; and
(i2) contacting at least part of the third fraction with benzene and/or toluene under transalkylation conditions such that at least part of the C9+ aromatic hydrocarbons are converted to xylenes.

23. The process of claim 22 , wherein at least part of the benzene and/or toluene employed in the contacting (i2) is separated from the alkylated product.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Detjen Todd E
• Chen Tan-Jen
• Loveless Brett T
• Tinger Robert G

Classifications

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• C07C15/08

  Xylenes · CPC title

• C07C5/22

  by isomerisation (with simultaneous hydrogenation C07C5/13; with simultaneous dehydrogenation C07C5/373) · CPC title

• C07C2/865

  the non-hydrocarbon is an ether · CPC title

• C07C2/864 Primary

  the non-hydrocarbon is an alcohol · CPC title