Process for the production of xylenes

Patent metadata

Field	Value
Publication number	US-9469579-B2
Application number	US-201615160507-A
Country	US
Kind code	B2
Filing date	May 20, 2016
Priority date	Jun 30, 2014
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

In a process for producing para-xylene, a toluene-containing stream is contacted with a methylating agent under conditions effective to convert toluene to xylenes and produce a methylated effluent stream. Para-xylene is recovered from the methylated effluent stream to produce a para-xylene depleted stream and part of the para-xylene depleted stream is contacted with a xylene isomerization catalyst under liquid phase isomerization conditions effective to produce a first isomerized stream, while part of the para-xylene depleted stream is contacted with a xylene isomerization catalyst under vapor phase isomerization conditions effective to produce a second isomerized stream. The first and second isomerized streams are then recycled to the para-xylene recovery step.

First claim

The invention claimed is:

1. A process for producing para-xylene, the process comprising:
(a) separating a feed stream comprising C 6+ aromatic hydrocarbons into at least a toluene-containing stream and a C 8 aromatic hydrocarbon-containing stream;
(b) contacting at least part of the toluene-containing stream from step (a) with a disproportionation catalyst under conditions effective to convert toluene and produce a disproportionated effluent stream containing benzene and xylenes;
(c) separating the disproportionated effluent stream from step (b) into a benzene stream and a first xylenes stream;
(d) contacting at least part of the benzene stream from step (c) with a methylating agent under conditions effective to convert benzene and produce a methylated effluent stream containing toluene and xylenes;
(e) separating the methylated effluent stream from step (d) into a toluene stream and a second xylenes stream;
(f) recycling at least part of the toluene stream from step (e) to the disproportionation step (b);
(g) recovering para-xylene from the C 8 aromatic hydrocarbon-containing stream from step (a), the first xylene stream from step (c), and the second xylenes stream from step (e) to produce at least one para-xylene depleted stream;
(h) contacting at least part of the at least one para-xylene depleted stream from step (g) with a xylene isomerization catalyst under liquid phase conditions effective to isomerize xylenes in the para-xylene depleted stream and produce a first isomerized stream;
(i) contacting at least part of the at least one para-xylene depleted stream from step (g) 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 a second isomerized stream; and
(j) recycling at least part of the first isomerized stream from step (h) and second isomerized stream from step (i) to the para-xylene recovery step (g).

2. The process of claim 1 , wherein the feed stream in (a) 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 separating (a) also produces a benzene-containing stream.

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

5. The process of claim 3 , wherein at least part of the benzene-containing stream from step (a) is supplied to the disproportionation step (b).

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

7. The process of claim 1 , wherein methylation step (c) 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).

8. The process of claim 7 , wherein said porous crystalline material comprises ZSM-5 which has undergone prior treatment with steam at a temperature of at least 950° C.

9. The process of claim 1 , wherein the disproportionation catalyst comprises ZSM-5 which has been selectivated with a silicon compound.

10. The process of claim 1 , wherein the separating step (c) is conducted by a dividing wall distillation column which separates the disproportionated effluent stream into a benzene stream, at least part of which is supplied to the methylation step (d), and a first xylenes stream, at least part of which is supplied to the para-xylene recovery step (g).

11. The process of claim 1 and further comprising:
(k) recovering ortho-xylene from at least one of the C 8 aromatic hydrocarbon-containing stream from step (a) and the second xylenes stream from step (e).

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

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

Classifications

• C07C6/06

  at a cyclic carbon-to-carbon double bond · CPC title

• C07C2/864 Primary

  the non-hydrocarbon is an alcohol · CPC title

• C07C5/2729 Primary

  Changing the branching point of an open chain or the point of substitution on a ring · CPC title

• C07C5/2767 Primary

  Changing the number of side-chains · CPC title

• B01J19/24

  Stationary reactors without moving elements inside (B01J19/08, B01J19/26 take precedence; with stationary particles B01J8/02) · CPC title