Processes and apparatuses for naphthene recycle in the production of aromatic products

Patent metadata

Field	Value
Publication number	US-10822291-B2
Application number	US-201816039139-A
Country	US
Kind code	B2
Filing date	Jul 18, 2018
Priority date	Mar 31, 2016
Publication date	Nov 3, 2020
Grant date	Nov 3, 2020

Abstract

Processes and apparatuses for producing a C 8 aromatic isomer product are provided. The processes comprise introducing a raffinate product stream comprising C 8 aromatic isomers to an isomerization unit to provide an isomerized stream. The isomerized stream is separated to provide a first stream comprising C 8 naphthenes and C 7 aromatic hydrocarbons and a second stream comprising C 8 aromatic isomers. The first stream is passed to an extractive distillation column to provide a recycle feedstream comprising the C 8 naphthenes and an extract stream comprising the C 7 aromatic hydrocarbons. The recycle feedstream is passed to the isomerization unit.

First claim

The invention claimed is:

1. A process for producing a C 8 aromatic isomer product, wherein the process comprises:
a) introducing a raffinate product stream comprising C 8 aromatic isomers to an isomerization unit to provide an isomerized stream;
b) separating the isomerized stream in a separation zone comprising a isomerate stripper column and a naphthene splitter column to provide a first stream comprising C 8 naphthenes and C 7 aromatic hydrocarbons and a second stream comprising C 8 aromatic isomers;
c) passing the first stream to an extractive distillation column to provide a recycle feedstream comprising the C 8 naphthenes and an extract stream comprising the C 7 aromatic hydrocarbons;
d) passing the recycle feedstream to the isomerization unit;
e) providing a reformate stream comprising aromatic hydrocarbons to a reformate splitter to provide a reformate bottoms stream comprising C 7+ aromatic hydrocarbons and a reformate overhead stream comprising C 7− aromatic hydrocarbons; and
f) passing a portion of the reformate bottoms stream from the reformate splitter to the naphthene splitter column.

2. The process of claim 1 , wherein the C 8 aromatic isomers are one of a paraxylene, meta-xylene and ethylbenzene.

3. The process of claim 1 further comprising passing the second stream to a xylene separation unit to provide a xylene extract stream comprising the C 8 aromatic isomer product and the raffinate product stream.

4. The process of claim 3 , wherein the xylene separation unit is a simulated moving bed adsorption unit.

5. The process of claim 4 , wherein the xylene separation unit uses a desorbent with a lower boiling point than the C 8 aromatic isomers.

6. The process of claim 5 , wherein the desorbent is toluene.

7. The process of claim 1 , wherein separating the isomerized stream comprises:
a) passing the isomerized stream to the isomerate stripper column to provide an isomerate stripper overhead stream comprising C6- hydrocarbons and an isomerate stripper bottoms stream; and
b) passing the isomerate stripper bottoms stream to the naphthene splitter column to provide the first stream comprising the C 8 naphthenes and C 7 aromatic hydrocarbons and the second stream comprising C 8 aromatic isomers.

8. The process of claim 1 , wherein the isomerized stream is produced in the presence of an ethylbenzene (EB) isomerization catalyst.

9. A process for the production of para-xylene, wherein the process comprises:
a) introducing a raffinate product stream comprising C 8 aromatic isomers to an isomerization unit to provide an isomerized stream, wherein the isomerized stream is produced in the presence of an ethylbenzene (EB) isomerization catalyst;
b) passing the isomerized stream to an isomerate stripper column to provide an isomerate stripper overhead stream comprising C 6− hydrocarbons and an isomerate stripper bottoms stream;
c) passing the isomerate stripper bottoms stream to a naphthene splitter column to provide an overhead naphthene splitter stream comprising the C 8 naphthenes and C 7 aromatic hydrocarbons and a naphthene splitter sidedraw stream comprising C 8 aromatic isomers;
d) passing the overhead naphthene splitter stream to an extractive distillation column to provide a recycle feedstream comprising the C 8 naphthenes and an extract stream comprising the C 7 aromatic hydrocarbons;
e) passing the recycle feedstream to the isomerization unit;
f) providing a reformate stream comprising aromatic hydrocarbons to a reformate splitter to provide a reformate bottoms stream comprising C 7+ aromatic hydrocarbons and a reformate overhead stream comprising C 7− aromatic hydrocarbons; and
g) passing a portion of the reformate bottoms stream from the reformate splitter to the naphthene splitter column.

10. The process of claim 9 further comprising passing the naphthene splitter sidedraw stream to a para-xylene separation unit to provide a xylene extract stream comprising paraxylene and the raffinate product stream and passing a naphthene splitter bottoms stream comprising C 8+ aromatic hydrocarbons to an aromatics rerun column.

11. The process of claim 10 wherein the para-xylene separation unit is a simulated moving bed adsorption unit.

12. The process of claim 11 , wherein the para-xylene separation unit uses a desorbent with a lower boiling point than the C 8 aromatic isomers.

13. The process of claim 12 , wherein the desorbent is toluene.

14. The process of claim 9 , wherein the isomerate stripper column and the naphthene splitter column operate at a first pressure and a second pressure respectively, wherein the second pressure is greater than the first pressure.

Assignees

• Uop Llc

Inventors

• Corradi Jason T
• Whitchurch Patrick C
• Pednekar Abhishek M
• Bresler Leonid
• Mlinar Anton N

Classifications

• C07C5/08 Primary

  of carbon-to-carbon triple bonds · CPC title

• C07C5/277

  Catalytic processes · CPC title

• C07C5/27

  Rearrangement of carbon atoms in the hydrocarbon skeleton · CPC title

• B01D2257/7027

  Aromatic hydrocarbons · CPC title

• C07C7/08 Primary

  by extractive distillation · CPC title