# US 2014/0155667 A1 · Process for the Production of Purified Xylene Isomers

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- Number: US 2014/0155667 A1
- Document ID: US20140155667A1
- Status: Published application
- Kind: A1
- Application number: 14/080,963
- Filed: 2013-11-15
- Published: 2014-06-05
- Earliest claimed: 2012-11-30
- Assignees: ExxonMobil Chemical Patents Inc.
- Applicants: ExxonMobil Chemical Patents Inc.
- Inventors: John Di-Yi Ou; Ronald L. DeMartino; Jeevan S. Abichandani
- Web page: https://patentgrep.com/patent/US20140155667A1

## CPC

- C07C 4/18: Catalytic processes
- C07C 5/2702: {Catalytic processes not covered by C07C5/2732 - C07C5/31; Catalytic processes covered by both C07C5/2732 and C07C5/277 simultaneously}
- C07C 5/2737: {with crystalline alumino-silicates, e.g. molecular sieves}
- C07C 7/04: by distillation
- C07C 7/12: by adsorption, i.e. purification or separation of hydrocarbons with the aid of solids, e.g. with ion-exchangers
- C07C 7/14: by crystallisation; Purification or separation of the crystals
- C07C 2529/70: of types characterised by their specific structure not provided for in groups C07C2529/08 - C07C2529/65
- Y02P 20/10: Process efficiency
- C07C: ACYCLIC OR CARBOCYCLIC COMPOUNDS
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The invention is directed to a process to produce para-xylene and optionally, ortho-xylene, including coupling a C9+-aromatics-removal system with an isomerization system or with a parallel configuration of two isomerization systems to reduce xylenes recycle for energy savings and/or productivity increases.

## Claims

### Claim 1

A process for producing para-xylene, PX, the process comprising:
(a) supplying at least one hydrocarbon feed comprising C8+ aromatics to a PX production system comprising a C9+-aromatics-removal system, a PX-recovery system, a first isomerization system, a second isomerization system, and a C7− hydrocarbons-removal system;
(b) separating C9+-aromatics from said feed in said C9+-aromatics-removal system to recover at least one C8-aromatics stream, at least one PX-lean stream having a lower PX concentration than said C8-aromatics stream, and at least one C9+ -aromatics-rich stream;
(c) separating said C8-aromatics stream in said PX-recovery system to recover a PX-rich stream and a PX-depleted stream;
(d) isomerizing at least partially in the vapor phase said PX-depleted stream in said first isomerization system to produce a first isomerized stream having a higher PX concentration than said PX-depleted stream;
(e) separating C7− hydrocarbons from said first isomerized stream in said C7− hydrocarbons-removal system to produce a C7− hydrocarbons-rich stream and a C7− hydrocarbons-depleted isomerized stream having a lower C7− hydrocarbons concentration than said first isomerized stream;
(f) recycling said C7− hydrocarbons-depleted isomerized stream to said C9+-aromatics-removal system;
(g) isomerizing, at least partially, in the liquid phase said PX-lean stream in said second isomerization system to produce a second isomerized stream having a higher PX concentration than said PX-lean stream; and
(h) recycling said second isomerized stream to said C9+-aromatics-removal system.

### Claim 2 (depends on 1)

The process of claim 1 further comprising isomerizing at least partially in the liquid phase at least a portion of said PX-depleted stream in said second isomerization system to produce at least a portion of said second isomerized stream having a higher PX concentration than said PX-depleted stream.

### Claim 3 (depends on 1)

The process of claim 1 further comprising reacting at least partially in the vapor phase at least a portion of said PX-lean stream in said first isomerization system to produce at least a portion of said first isomerized stream having a higher PX concentration than said PX-lean stream.

### Claim 4 (depends on 1)

The process of claim 1 further comprising separating C7− hydrocarbons from at least a portion of said second isomerized stream in said C7− hydrocarbons-removal system to generate at least a portion of said C7− hydrocarbons-depleted isomerized stream having a lower C7− hydrocarbons concentration than said second isomerized stream.

### Claim 5 (depends on 1)

The process of claim 1 further comprising sending at least a portion of said second isomerized stream to said PX-recovery system.

### Claim 6 (depends on 1)

The process of claim 1 further comprising separating benzene from at least a portion of said second isomerized stream in a benzene removal system to produce a benzene-rich stream and a benzene-depleted stream.

### Claim 7 (depends on 6)

The process of claim 6 and further comprising sending at least a portion of said benzene-depleted stream to said PX-recovery system.

### Claim 8 (depends on 6)

The process of claims 6 and further comprising sending at least a portion of said benzene-depleted stream to said C9+-aromatics-removal system.

### Claim 9 (depends on 1)

The process of claim 1, wherein said C9+-aromatics-removal system comprises at least one distillation unit.

### Claim 10 (depends on 9)

The process of claim 9, wherein the C9+-aromatics-removal system produces an overhead stream comprising a C8-aromatics stream and a bottoms stream comprising a C9+-aromatics-rich stream.

### Claim 11 (depends on 9)

The process of claim 9, wherein said PX-lean stream comprises, at least partially, the liquid drawn from a drawing tray of which the tray number is in between 30% to 80% of the total tray number of said distillation unit(s).

### Claim 12 (depends on 11)

The process of claim 11, wherein at least a portion of said second isomerized stream and/or benzene-depleted stream is recycled to said C9+-aromatics-removal system at the same location as the drawing tray.

### Claim 13 (depends on 11)

The process of claim 11, wherein at least a portion of said second isomerized stream and/or benzene-depleted stream is recycled to said C9+-aromatics-removal system at a tray located above said drawing tray.

### Claim 14 (depends on 9)

The process of claim 9, wherein said distillation unit comprises at least one dividing-wall distillation unit.

### Claim 15 (depends on 9)

The process of claim 9, wherein at least a portion of said second isomerization system is installed inside said distillation unit in the form of catalytic distillation to effect said isomerization and said separation.

### Claim 16 (depends on 1)

The process of claim 1, wherein said C7− hydrocarbons-removal system comprises at least one distillation unit.

### Claim 17 (depends on 1)

The process of claim 1, wherein said PX recovery system comprises a fractional crystallization unit and/or a selective adsorption unit for recovering said PX-rich stream.

### Claim 18 (depends on 1)

The process of claim 1, wherein each of said isomerizations comprise at least one of xylenes isomerization, ethylbenzene dealkylation, and ethylbenzene isomerization.

### Claim 19 (depends on 1)

The process of claim 1 further including separating said C9+-aromatics-rich stream in an ortho-xylene-recovery system to produce an ortho-xylene-rich stream and an ortho-xylene-depleted C9+-aromatics stream.

### Claim 20 (depends on 1)

The process of claim 1, wherein the PX concentration among the xylenes in said C8-aromatics stream is above the PX equilibrium concentration.

### Claim 21 (depends on 1)

The process of claim 1, wherein said feed comprising C8+ aromatics includes at least one feed selected from the group consisting of a C8+ selective toluene disproportionation product, a C8+ transalkylation product, a C8+ reformate product, a C8+ toluene disproportionation product, and a C8+ toluene methylation product, and a C8+ benzene methylation product.

### Claim 22

An apparatus for the production of para-xylene, PX, and, optionally, ortho-xylene, OX, comprising a first fractionation column operating at conditions suitable for the separation of C8+ aromatics streams into: a) a C8-aromatics overhead stream; b) a PX-lean middle stream having a lower PX concentration than said C8-aromatics overhead stream; and c) a C9+-aromatics-rich bottom stream, where said C8-aromatics overhead stream is fluidly connected with a PX-recovery unit, wherein said PX-recovery unit provides a PX-rich stream and a PX-depleted stream, where said PX-depleted stream is fluidly connected with a vapor-phase isomerization unit to produce a first isomerized stream which is fluidly connected with a second fractionation column operating at conditions suitable for separating said first isomerized stream into a C7− hydrocarbons-rich overhead stream and a C7− hydrocarbons-depleted bottom stream, where said C7− hydrocarbons-depleted bottom stream is fluidly connected with said first fractionation column to effect a recycle, where said PX-lean middle stream is fluidly connected with a liquid-phase isomerization unit to produce a second isomerized stream which is connected fluidly with said first fractionation column to effect another recycle.

### Claim 23 (depends on 22)

The apparatus of claim 22 and further comprising connecting fluidly said PX-depleted stream with said liquid-phase isomerization unit so that a portion of said PX-depleted stream is passed to said liquid-phase isomerization unit and another portion of said PX-depleted stream is passed to said vapor-phase isomerization unit.

### Claim 24 (depends on 22)

The apparatus of claim 22 and further comprising connecting fluidly said PX-lean middle stream with said vapor-phase isomerization unit so that a portion of said PX-lean stream is passed to said vapor-phase isomerization unit and another portion of said PX-lean stream is passed to said liquid-phase isomerization unit.

### Claim 25 (depends on 22)

The apparatus of claim 22 and further comprising connecting fluidly said second isomerized stream to said second fractionation column so that at least a portion of said second isomerized stream is passed to said second fractionation column.

### Claim 26 (depends on 22)

The apparatus of claim 22 and further comprising connecting fluidly said second isomerized stream to said PX-recovery unit so that at least a portion of said second isomerized stream is passed to said PX-recovery unit.

### Claim 27 (depends on 22)

The apparatus of claim 22 and further comprising connecting fluidly said second isomerized stream with at least one other fractionator, wherein said at least one other fractionator operates under conditions suitable for producing a benzene-rich overhead stream and a benzene-depleted bottom stream.

### Claim 28 (depends on 27)

The apparatus of claim 27 further comprising connecting fluidly said benzene-depleted bottom stream with said first fractionation column so that at least a portion of said benzene-depleted bottom stream is passed to said first fractionation column.

### Claim 29 (depends on 27)

The apparatus of claim 27 further comprising connecting fluidly said benzene-depleted stream with said PX-recovery unit so that at least a portion of said benzene-depleted stream is passed to said PX-recovery unit.

### Claim 30 (depends on 22)

The apparatus of claim 22, wherein said PX-recovery unit is selected from at least one of a crystallizer and an adsorptive separator.

### Claim 31 (depends on 22)

The apparatus of claim 22, wherein each of said isomerization units is selected from at least one of xylenes isomerization, ethylbenzene dealkylation, and ethylbenzene isomerization.

### Claim 32 (depends on 22)

The apparatus of claim 22, further including at least one separation unit downstream of said first fractionation column fluidly connected to said C9+-aromatics-rich bottom stream, whereby OX is separated from C9+-aromatics, said at least one separation unit selected from a crystallizer, a membrane unit, or a fractionation column.