Process and apparatus for the production of para-xylene

Patent metadata

Field	Value
Publication number	US-9517980-B2
Application number	US-201514969327-A
Country	US
Kind code	B2
Filing date	Dec 15, 2015
Priority date	Apr 30, 2015
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

The present invention is an improved process and apparatus for producing para-xylene, particularly with respect to a process that involves the methylation of toluene and/or benzene to selectively produce para-xylene, wherein streams having differing amounts of ethylbenzene are separately treated in the recovery of para-xylene. A first hydrocarbon feed comprising xylenes and ethylbenzene is provided to a first para-xylene adsorption section, and a second hydrocarbon feed comprising xylenes and less EB than the first hydrocarbon feed is provided to a second para-xylene adsorption section. Segregating the feeds with differing ethylbenzene contents increases the overall efficiency of the adsorption of para-xylene by the adsorption units. Efficiency and energy savings may be further improved by subjecting the lower-content ethylbenzene stream to liquid phase isomerization.

First claim

The invention claimed is:

1. A process for producing para-xylene, the process comprising:
(a) providing a first hydrocarbon feed comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene to a first para-xylene adsorption section;
(b) providing a second hydrocarbon feed comprising para-xylene, meta-xylene, ortho-xylene, and less ethylbenzene than the first hydrocarbon feed to a second para-xylene adsorption section;
(c) recovering a first para-xylene-rich stream and a first para-xylene-depleted stream from the first hydrocarbon feed from the first para-xylene adsorption section;
(d) recovering a second para-xylene-rich stream and a second para-xylene-depleted stream from the second hydrocarbon feed from the second para-xylene adsorption section;
(e) separating the first and second para-xylene-depleted streams into an ethylbenzene-rich stream, which contains a majority portion of the ethylbenzene from the first and second para-xylene-depleted streams, and an ethylbenzene-depleted stream, which contains a minor portion of the ethylbenzene from the first and second para-xylene-depleted streams, in a divided wall raffinate column, wherein the first and second para-xylene-depleted streams are provided to the divided wall raffinate column on opposite sides of the dividing wall;
(f) isomerizing meta-xylene, ortho-xylene, and ethylbenzene in at least a portion of the ethylbenzene-rich stream at least partially in the vapor phase back towards to an equilibrium concentration of xylene isomers to produce a second isomerized stream having a higher para-xylene concentration than the para-xylene-depleted stream;
(g) isomerizing at least a portion of the ethylbenzene-depleted stream at least partially in the liquid phase back towards an equilibrium concentration of the xylenes isomers to produce a first isomerized stream having a higher para-xylene concentration than the para-xylene-depleted stream;
(h) recycling at least a portion of the first isomerized stream to the first para-xylene adsorption section; and
(i) recycling at least a portion of the second isomerized stream to the second para-xylene adsorption section.

2. The process of claim 1 , wherein the first and second para-xylene adsorption sections each comprise two simulated moving bed adsorption towers.

3. The process of claim 1 , wherein the first and second para-xylene adsorption sections each comprise one simulated moving bed adsorption tower.

4. The process of claim 1 , wherein the first hydrocarbon feed comprises at least about 10.0 wt % of ethylbenzene and the second hydrocarbon feed comprises less than about 10.0 wt % ethylbenzene.

5. The process of claim 1 , wherein step (f) is conducted under ethylbenzene dealkylation conditions.

6. The process of claim 1 , wherein step (f) is conducted under ethylbenzene isomerization conditions.

7. The process of claim 1 , wherein the first hydrocarbon feed is selected from the group consisting of a reformate stream, a hydrocracking product stream, a xylene or EB reaction product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, and mixture thereof.

8. The process of claim 1 , wherein the second hydrocarbon feed is selected from the group consisting of a para-selective aromatic alkylation product stream, a non-selective aromatic alkylation product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, a methanol/dimethyl ether to aromatic product stream, a syngas to aromatic product stream, a C 2 -C 4 alkane/alkene to aromatic product stream, an import stream, and/or an off-spec PX stream from a PX recovery unit.

9. The process of claim 1 , wherein the second hydrocarbon feed comprises a selective benzene and/or toluene methylation product stream.

10. The process of claim 9 , wherein the selective benzene and/or toluene methylation product stream is produced in a fluid bed, fixed bed, moving bed, or cyclic bed reactor.

11. The process of claim 1 , further comprising separating at least one C 7− isomerized stream from the first isomerized stream in a detoluenizing fractionation column prior to step (h).

12. The process of claim 1 , wherein step (a) further comprises separating a C 9+ stream from the first hydrocarbon feed in a first xylenes fractionation column prior to providing the first hydrocarbon feed to the first para-xylene adsorption section, and wherein step (b) further comprises separating a C 9+ stream from the second hydrocarbon feed in a second xylenes fractionation column prior to providing second hydrocarbon feed to the second para-xylene adsorption section.

13. The process of claim 12 , further comprising providing the first isomerized stream to the first xylenes fractionation column prior to step (h).

14. The process of claim 12 , further comprising providing the second isomerized stream to the second xylenes fractionation column prior to step (i).

15. The process of claim 14 , wherein the second isomerized stream is provided to the second xylenes fractionation column at a higher location than the second hydrocarbon feed.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Tinger Robert G
• Pilliod Dana L
• Molinier Michel

Classifications

• B01D15/185 Primary

  characterised by the components to be separated · CPC title

• C07C5/2767 Primary

  Changing the number of side-chains · CPC title

• B01D3/14

  Fractional distillation {or use of a fractionation or rectification column} · CPC title

• C07C5/2729

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

• B01J2219/24

  Stationary reactors without moving elements inside · CPC title