Process and plant for recovering acrylic acid

Patent metadata

Field	Value
Publication number	US-9701612-B2
Application number	US-201514857967-A
Country	US
Kind code	B2
Filing date	Sep 18, 2015
Priority date	Sep 30, 2014
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

A process for recovering acrylic acid, including: a) division of a heated mother acid stream in direction of an absorption a condensation column and a dissociation column; b) feeding of a heated mother acid substream as runback to the dissociation column; c) feeding-in of at least one stripping gas stream to the dissociation column; d) feeding-in of a secondary component stream comprising oligomeric acrylic acid from the absorption column to the dissociation column; e) dissociation of part of oligomeric acrylic acid in the dissociation column to give monomeric acrylic acid; f) removal of secondary components comprised in the secondary component stream in the dissociation column; g) discharge of monomeric acrylic acid as gas mixture with introduced circulating stripping gas stream from the dissociation column; and h) feeding-in of the gas mixture to the absorption column.

First claim

The invention claimed is:

1. A process for recovering acrylic acid, the process comprising:
a) dividing a heated mother acid stream at least partially depleted from acrylic acid from a crystallization apparatus into two substreams, wherein a second heated mother acid substream is fed in a direction of an absorption column ( 201 ) and a first heated mother acid stream is fed in a direction of a dissociation column ( 205 ),
b) feeding the first heated mother acid substream as runback to an uppermost tray of the dissociation column ( 205 ),
c) feeding-in at least one stripping gas stream below a lowermost tray of the dissociation column ( 205 ),
d) feeding-in a secondary component stream comprising oligomeric acrylic acid from the absorption column ( 201 ) to a middle tray of the dissociation column ( 205 ),
e) dissociating at least part of the oligomeric acrylic acid from the secondary component stream in the dissociation column ( 205 ) to give monomeric acrylic acid,
f) removing the secondary components comprised in the secondary component stream by countercurrent rectification in the dissociation column ( 205 ),
g) discharging the monomeric acrylic acid without condensation as a gas mixture with the introduced circulating stripping gas stream at the top of the dissociation column ( 205 ), and
h) feeding-in the gas mixture below the lowermost tray of the absorption column ( 201 ).

2. The process according to claim 1 , wherein the mother acid stream is heated against an acrylic acid stream from a absorption column ( 201 ).

3. The process according to claim 1 , wherein step h) is carried out indirectly by the gas mixture being introduced into a quenching apparatus ( 203 ) for quenching a product gas mixture comprising acrylic acid.

4. The process according to claim 1 , wherein the mother acid stream comprises essentially acrylic acid, water, and acetic acid.

5. The process according to claim 1 , wherein the secondary component stream comprises essentially acrylic acid, diacrylic acid, and polyacrylic acid, and also maleic acid, benzoic acid, benzaldehyde, furfurals, and water.

6. The process according to claim 1 , wherein the stripping gas stream comprises essentially nitrogen, acrylic acid, water, and oxygen, and also carbon dioxide and acetic acid.

7. The process according to claim 1 , wherein from 60% to 95% of the dissociable components of the secondary component stream are dissociated in step e).

8. The process according to claim 7 , wherein from 85% to 90% of the dissociable components of the secondary component stream are dissociated in step e).

9. The process according to claim 4 , wherein the mother acid stream comprises, based on a total weight of the mother acid stream:
from 90-95% by weight of acrylic acid;
from 3-6% by weight of water; and
from 1-2% by weight of acetic acid.

10. The process according to claim 5 , wherein the secondary component stream comprises, based on a total weight of the secondary component stream:
from 50-60% by weight of acrylic acid;
from 20-30% by weight of diacrylic acid;
from 5-10% by weight of polyacrylic acid;
from 6-9% by weight of maleic acid;
from 1-2% by weight of benzoic acid;
less than 0.5% by weight of benzaldehyde;
less than 0.5% by weight of furfurals; and
from 0.5-1% by weight of water.

11. The process according to claim 6 , wherein the stripping gas stream comprises, based on a total weight of the stripping gas stream:
from 80-85% by weight of nitrogen;
from 3-5% by weight of acrylic acid;
from 3-5% by weight of water;
from 3-4% by weight of oxygen,
from 2-3% by weight of carbon dioxide; and
from 1-2% by weight of acetic acid.

Assignees

• Basf Se

Inventors

• Hammon Ulrich
• Walter Thomas
• Ottenbacher Markus
• Huetten Frank

Classifications

• B01J2219/24

  Stationary reactors without moving elements inside · CPC title

• C07C51/48

  by liquid-liquid treatment · CPC title

• C07C51/487 Primary

  by treatment giving rise to chemical modification (by chemisorption C07C51/47) · CPC title

• B01D3/143

  by two or more of a fractionation, separation or rectification step · CPC title

• C07C51/44 Primary

  by distillation · CPC title