Process for the production of xylenes

Patent metadata

Field	Value
Publication number	US-9302953-B2
Application number	US-201514735753-A
Country	US
Kind code	B2
Filing date	Jun 10, 2015
Priority date	Jun 30, 2014
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

In a process for producing para-xylene, a feed stream comprising C 6+ aromatic hydrocarbons is separated into a toluene-containing stream, a C 8 aromatic hydrocarbon-containing stream and a C 9+ aromatic hydrocarbon-containing stream. The toluene-containing stream is contacted with a methylating agent to convert toluene to xylenes and produce a methylated effluent stream. Para-xylene is recovered from the C 8 aromatic hydrocarbon-containing stream and the methylated effluent stream in a para-xylene recovery section to produce a para-xylene depleted stream, which is then contacted with a xylene isomerization catalyst under liquid phase conditions effective to isomerize xylenes in the para-xylene depleted stream and produce an isomerized stream. The C 9+ -containing stream with a transalkylation catalyst under conditions effective to convert C 9+ -aromatics to C 8− -aromatics and produce a transalkylated stream, which is recycled together with the isomerized stream to the para-xylene recovery section.

First claim

The invention claimed is:

1. A process for producing para-xylene, the process comprising:
(a1) separating a feed stream comprising C 6+ aromatic hydrocarbons into at least a toluene-containing stream, a C 8 aromatic hydrocarbon-containing stream and a C 9+ aromatic hydrocarbon-containing stream;
(b1) contacting at least part of the toluene-containing stream with a methylating agent under conditions effective to convert toluene to xylenes and produce a methylated effluent stream;
(c1) recovering para-xylene from the C 8 aromatic hydrocarbon-containing stream and the methylated effluent stream to produce at least one para-xylene depleted stream;
(d1) contacting at least part of the at least one para-xylene depleted stream with a xylene isomerization catalyst under liquid phase conditions effective to isomerize xylenes in the para-xylene depleted stream and produce an isomerized stream;
(e1) recycling at least part of the isomerized stream to (c1);
(f1) contacting at least part of the C 9+ -containing stream with a transalkylation catalyst under conditions effective to convert C 9+ -aromatics to C 8− -aromatics and produce a transalkylated stream; and
(g1) recycling at least part of the transalkylated stream to (b1) and (c1).

2. The process of claim 1 , wherein the feed stream in (a1) comprises a mixture of C 6+ aromatic and aliphatic hydrocarbons produced by removing C 5 -hydrocarbons from a reformate stream.

3. The process of claim 1 , wherein the toluene-containing stream is subjected to extraction to remove non-aromatics and produce a toluene-containing aromatic stream, wherein the toluene-containing aromatic stream is separated into a benzene stream and a toluene stream, and further wherein the toluene stream is supplied to the contacting (b1).

4. The process of claim 1 , wherein the separating (a1) also produces a benzene-containing stream.

5. The process of claim 4 , wherein all of the toluene-containing stream is supplied to the contacting (b1).

6. The process of claim 3 , wherein a portion of the benzene stream or benzene-containing stream is supplied to the contacting (f1) to optimize the methyl to ring ratio.

7. The process of claim 1 , wherein the separating (a1) is conducted by a dividing wall distillation column.

8. The process of claim 4 , wherein at least part of the benzene-containing stream is supplied to the contacting (b1).

9. The process of claim 1 , wherein the methylating agent comprises methanol.

10. The process of claim 1 , wherein contacting (b1) is conducted in the presence of a catalyst comprising a porous crystalline material having a Diffusion Parameter for 2,2 dimethylbutane of about 0.1-15 sec −1 when measured at a temperature of 120° C. and a 2,2 dimethylbutane pressure of 60 torr (8 kPa).

11. The process of claim 10 , wherein said porous crystalline material comprises ZSM-5 which has undergone prior treatment with steam at a temperature of at least 950° C.

12. The process of claim 1 and further comprising:
(h1) contacting at least part of the at least one para-xylene depleted stream with a xylene isomerization catalyst under vapor phase conditions effective to isomerize xylenes and dealkylate or isomerize ethylbenzene in the para-xylene depleted stream and produce an isomerized and ethylbenzene-depleted stream; and
(i1) recycling at least part of the isomerized and ethylbenzene-depleted stream to (c1).

13. The process of claim 12 , wherein the vapor phase conditions are effective to dealkylate ethylbenzene in the para-xylene depleted stream and produce a by-product toluene stream, and further comprising supplying said by-product toluene stream to the contacting (b1).

14. The process of claim 1 , wherein at least a portion of the C 7− -aromatics in the transalkylated stream are recycled to the contacting (b1).

15. The process of claim 1 , wherein part of the C 7− -aromatics in the transalkylated stream are recycled to the contacting (f1).

16. The process of claim 1 and further comprising:
(j1) recovering ortho-xylene from at least one of the C 8 aromatic hydrocarbon-containing stream, the methylated effluent stream and the transalkylated stream.

17. The process of claim 1 and further comprising:
(k1) recovering unconverted toluene from the methylated effluent stream; and
(l1) supplying the unconverted toluene to the contacting (b1).

Assignees

• Exxonmobil Chem Patents Inc
• Exxonmobil Chemicals Patents Inc

Inventors

• Molinier Michel
• Abichandani Jeevan S
• Andrews Jeffrey L
• Bender Timothy P
• Tinger Robert G
• Stanley Dennis J
• Wagner George J

Classifications

• C07C2/864 Primary

  the non-hydrocarbon is an alcohol · CPC title

• Y02P20/582

  Recycling of unreacted starting or intermediate materials · CPC title

• C07C7/005

  Processes comprising at least two steps in series · CPC title

• C07C7/14

  by crystallisation; Purification or separation of the crystals · CPC title

• C07C6/123

  of only one hydrocarbon · CPC title