# US 9,517,979 B2 · Process and apparatus for the production of para-xylene

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- Number: US 9,517,979 B2
- Document ID: US9517979B2
- Status: Granted
- Kind: B2
- Application number: 14/969,298
- Filed: 2015-12-15
- Published: 2016-09-22
- Granted: 2016-12-13
- Earliest claimed: 2015-03-19
- Assignees: ExxonMobil Chemical Patents Inc.
- Applicants: ExxonMobil Chemical Patents Inc.
- Inventors: Timothy P. Bender; John R. Porter; Dana L. Pilliod
- Web page: https://patentgrep.com/patent/US9517979B2

## CPC

- C07C 5/2729: {Changing the branching point of an open chain or the point of substitution on a ring}
- B01D 15/185: {characterised by the components to be separated}
- B01J 19/2445: {placed in parallel}
- C07C 5/2737: {with crystalline alumino-silicates, e.g. molecular sieves}
- C07C 5/2767: {Changing the number of side-chains}
- C07C 5/2775: {with crystalline alumino-silicates, e.g. molecular sieves}
- B01J 2219/24: Stationary reactors without moving elements inside
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS

## Abstract

A process for producing para-xylene (PX) comprises supplying a hydrocarbon feed comprising xylenes and ethylbenzene (EB) to a PX recovery unit, where a PX-rich stream and at least one PX-depleted stream are recovered from the feed. The PX-depleted stream is then separated into an EB-rich stream and an EB-depleted stream in a divided wall column. The EB-depleted stream is then isomerized under at least partial liquid phase conditions to produce a first isomerized stream having a higher PX concentration than the PX-depleted stream, and the EB-rich stream is isomerized under at least partial vapor phase conditions to produce a second isomerized stream having a higher PX concentration than the PX-depleted stream. The first and second isomerized streams are then recycled to the PX recovery unit to recover additional PX and the process is repeated to define a so-called xylene isomerization loop.

## Claims

### Claim 1

A process for producing para-xylene, the process comprising:
(a) providing a hydrocarbon feed comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene to a para-xylene recovery unit;
(b) recovering a para-xylene-rich stream and at least one para-xylene-depleted stream from the hydrocarbon feed in the para-xylene recovery unit;
(c) separating the at least one para-xylene-depleted stream into an ethylbenzene-rich stream, which contains a majority portion of the ethylbenzene from the at least one para-xylene-depleted stream, and an ethylbenzene-depleted stream, which contains a minor portion of the ethylbenzene from the at least one para-xylene-depleted stream, in a divided wall column;
(d) 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;
(e) 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; and
(f) recycling at least a portion of the first and second isomerized streams to the para-xylene recovery unit.

### Claim 2 (depends on 1)

The process of claim 1, wherein the para-xylene recovery unit comprises a simulated moving bed adsorption unit.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

The process of claim 1, wherein two para-xylene-depleted streams are recovered from the para-xylene recovery unit in step (b), a para-xylene-depleted stream rich in ethylbenzene and a para-xylene-depleted stream low in ethylbenzene.

### Claim 6 (depends on 1)

The process of claim 1, wherein the 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 alkylation product stream, an aromatic disproportionation stream, and mixtures thereof.

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

The process of claim 1, further comprising separating a C7− isomerized stream from the second isomerized stream in a fractionation column prior to step (f).

### Claim 9 (depends on 1)

The process of claim 1, further comprising separating the first and second isomerized streams into an overhead stream comprising C8 hydrocarbons and a bottoms stream containing C9+ hydrocarbons in a xylenes fractionation column prior to step (f).

### Claim 10 (depends on 9)

The process of claim 9, wherein the first isomerized stream is provided to the xylenes fractionation column at a higher location than the second isomerized stream.

### Claim 11

A process for producing para-xylene, the process comprising:
(a) providing a hydrocarbon feed comprising para-xylene, meta-xylene, ortho-xylene, and ethylbenzene to a para-xylene recovery unit;
(b) recovering a para-xylene-rich stream, a para-xylene-depleted stream rich in ethylbenzene and a para-xylene-depleted stream low in ethylbenzene from the feed in the para-xylene recovery unit;
(c) separating the para-xylene-depleted stream rich in ethylbenzene and para-xylene-depleted stream low in ethylbenzene into an ethylbenzene-rich stream, which contains a majority portion of the ethylbenzene from the at least one para-xylene-depleted stream, and an ethylbenzene-depleted stream, which contains a minor portion of the ethylbenzene from the at least one para-xylene-depleted stream, in a divided wall column;
(d) 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;
(e) 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; and
(f) recycling at least a portion of the first and second isomerized streams to the para-xylene recovery unit.

### Claim 12 (depends on 11)

The process of claim 11, wherein the para-xylene recovery unit comprises a simulated moving bed adsorption unit.

### Claim 13 (depends on 11)

The process of claim 11, wherein step (e) is conducted under ethylbenzene dealkylation conditions.

### Claim 14 (depends on 11)

The process of claim 11, wherein step (e) is conducted under ethylbenzene isomerization conditions.

### Claim 15 (depends on 11)

The process of claim 11, wherein the 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 alkylation product stream, an aromatic disproportionation stream, an aromatic transalkylation stream, a methanol to aromatic product stream, and mixtures thereof.

### Claim 16 (depends on 11)

The process of claim 11, wherein the hydrocarbon feed comprises a benzene and/or toluene methylation product stream.

### Claim 17 (depends on 11)

The process of claim 11, further comprising separating a C7− isomerized stream from the second isomerized stream in a detoluenizing fractionation column prior to step (f).

### Claim 18 (depends on 11)

The process of claim 11, further comprising separating the first and second isomerized streams into an overhead stream comprising C8 hydrocarbons and a bottoms stream containing C9+ hydrocarbons in a xylenes fractionation column prior to step (f).

### Claim 19 (depends on 18)

The process of claim 18, wherein the first isomerized stream is provided to the xylenes fractionation column at a higher location than the second isomerized stream.