Process for preparing acrylic acid from methanol and acetic acid

Patent metadata

Field	Value
Publication number	US-9593065-B2
Application number	US-201514794955-A
Country	US
Kind code	B2
Filing date	Jul 9, 2015
Priority date	Jul 31, 2014
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

A process for preparing acrylic acid from methanol and acetic acid, comprising (i) contacting a gaseous stream S 0 comprising methanol, oxygen and inert gas with an oxidation catalyst to obtain a gaseous stream S 1 comprising formaldehyde and inert gas; (ii) removing at least a portion of the inert gas present in S 1 from at least a portion of the formaldehyde present in S 1 by absorbing this formaldehyde in an absorbent to obtain a gaseous stream S 2 comprising the portion of the inert gas removed, and to obtain a stream S 3 comprising absorbent and absorbate comprising formaldehyde; (iii) optionally removing a portion or the entirety of the absorbent present in stream S 3 , such that a stream S 3 a remains from stream S 3 , and producing a stream S 4 from at least stream S 3 or stream S 3 a and a stream S 5 comprising acetic acid; and (iv) contacting stream S 4 in gaseous form with an aldol condensation catalyst to obtain a gaseous stream S 6 comprising acrylic acid.

First claim

The invention claimed is:

1. A process for preparing acrylic acid from methanol and acetic acid, the process comprising
(i) contacting a gaseous stream S 0 comprising methanol, oxygen and inert gas with an oxidation catalyst to obtain a gaseous stream S 1 comprising formaldehyde and inert gas;
(ii) removing at least a portion of the inert gas present in S 1 from at least a portion of the formaldehyde present in S 1 by absorbing this formaldehyde in an absorbent comprising water and formaldehyde to obtain a gaseous stream S 2 comprising the portion of the inert gas removed, and to obtain a stream S 3 comprising the absorbent and an absorbate comprising the formaldehyde obtained in (i);
(iii) optionally removing a portion or an entirety of the absorbent present in the stream S 3 , such that a stream S 3 a remains from the stream S 3 , and producing a stream S 4 from at least the stream S 3 or the stream S 3 a and a stream S 5 comprising acetic acid; and
(iv) contacting the stream S 4 in gaseous form with an aldol condensation catalyst to obtain a gaseous stream S 6 comprising acrylic acid;
wherein the water of the absorbent comprises water obtained in the aldol condensation (iv) which is recycled to (ii), and
the formaldehyde of the absorbent comprises unconverted formaldehyde from the aldol condensation (iv) which is recycled to (ii).

2. The process according to claim 1 , wherein the oxidation catalyst in (i) comprises silver.

3. The process according to claim 1 , further comprising
(a) contacting a stream S 0 a comprising oxygen and inert gas with a stream S 0 b comprising methanol to obtain a stream S 0 c depleted of inert gas and a stream S 0 enriched in inert gas.

4. The process according to claim 3 , wherein the contacting of S 0 a and S 0 b in (a) is effected in countercurrent of S 0 a relative to S 0 b.

5. The process according to claim 1 , wherein the removing (ii) is effected by at least one column, equipped with separating internals.

6. The process according to claim 5 , wherein the stream S 3 is withdrawn from a bottom of the column in (ii).

7. The process according to claim 6 , wherein a portion of the stream S 3 , optionally after cooling to a temperature in a range from 60 to 70° C., is recycled into a lower part of the column in (ii) as absorbent.

8. The process according to claim 5 , comprising
(a) contacting a stream S 0 a comprising oxygen and inert gas with a stream S 0 b comprising methanol to obtain a stream S 0 c depleted of inert gas and a stream S 0 enriched in inert gas, the contacting in (a) being effected in countercurrent, using one column;
wherein a stream is withdrawn from at least one upper part of the column in (ii) and at least partly recycled into (a).

9. The process according to claim 1 , wherein at least 95% by weight of the stream S 4 consists of water, formaldehyde, acetic acid and inert gas.

10. The process according to claim 1 , wherein the stream S 4 is produced in (iii) from the stream S 3 , the stream S 5 comprising acetic acid and additionally at least one stream S 4 a comprising inert gas, carbon dioxide and carbon monoxide, at least a portion of the stream S 4 a being a stream recycled from the process beyond (iv).

11. The process according to claim 1 , wherein the aldol condensation catalyst in (iv) comprises a vanadium-phosphorus oxide.

12. The process according to claim 1 , wherein S 6 comprises acrylic acid and formaldehyde.

13. The process according to claim 1 , further comprising
(v) removing at least a portion of the formaldehyde present in S 6 from at least a portion of the acrylic acid present in S 6 to obtain an acrylic acid-depleted stream S 7 comprising formaldehyde and to obtain a formaldehyde-depleted stream S 8 comprising acrylic acid.

14. The process according to claim 13 , wherein the stream S 8 is sent to a removal stage comprising
(vi) removing at least a portion of the acrylic acid present in S 8 to obtain a stream S 9 depleted in acrylic acid compared to S 8 and at least one stream S 10 enriched in acrylic acid compared to S 8 .

15. The process according to claim 14 , wherein the removing (vi) is effected by at least one rectificative column, equipped with separating internals.

16. The process according to claim 15 , wherein the stream S 9 is withdrawn from a bottom of the column in (vi).

17. The process according to claim 16 , wherein a first portion of the stream S 9 , optionally after condensation and cooling to a temperature in a range from 30 to 45° C., is recycled into a top of a column in (ii) as reflux.

18. The process according to claim 14 , wherein the stream S 5 is produced from a stream S 5 a comprising acetic acid and a stream S 5 b comprising acetic acid, at least a portion of the stream S 5 b being a stream recycled from the process, and a further portion or more than one further portion of the stream S 9 being recycled into the process as the stream S 5 b.

19. The process according to claim 13 , wherein the stream S 4 is produced in (iii) from the stream S 3 , the stream S 5 comprising acetic acid and additionally at least one stream S 4 a comprising inert gas, carbon dioxide and carbon monoxide, at least a portion of the stream S 4 a being a stream recycled from the process, and a portion of the stream S 7 , a stream S 7 a , being recycled into the process in uncondensed form as the stream S 4 a.

20. The process according to claim 19 , wherein, as the stream S 7 a , from 2% to 10% by weight of the stream S 7 , based on a total amount thereof, is recycled into the process in uncondensed form as the stream S 4 a or, as the stream S 7 a , from 10% to 90% by weight of the stream S 7 , based on the total amount thereof, is recycled into the process in uncondensed form as the stream S 4 a.

21. The process according to claim 13 , wherein a condensed portion of the stream S 7 , a liquid stream S 7 b , is recycled into a top of a column in (v) as reflux.

22. The process according to claim 13 , wherein a portion or more than one portion of the stream S 7 condensed by cooling the stream S 7 is fed as a liquid stream 7 c to a removal stage comprising
(vii) separating the stream S 7 c into a formaldehyde-enriched stream S 11 and a formaldehyde-depleted stream S 12 .

23. The process according to claim 22 , wherein the separating (vii) is effected by at least one column, equipped with separating internals.

24. The process according to claim 23 , wherein a portion of the stream S 11 , optionally after cooling and condensation to a temperature in a range from 95 to 110° C., is recycled into a top of the column in (vii) as reflux.

25. The process according to claim 22 , wherein the separating (vii) is effected by rectification, comprising at least one column equipped with separating internals, and with recycling of a portion of the stream S 11 , optionally after cooling and condensation to a temperature in a range from 15 to 40° C., into a top of one of columns in (ii) as reflux.

Assignees

• Basf Se

Inventors

• Schulz Lukas
• Woerz Nicolai Tonio
• Blaschke Tim
• Hartmann Marco
• Huetten Frank

Classifications

• C07C45/38

  being a primary hydroxyl group · CPC title

• C07C51/353

  by isomerisation; by change of size of the carbon skeleton · CPC title

• C07C57/04

  Acrylic acid; Methacrylic acid · CPC title

• B01J23/50 Primary

  Silver · CPC title

• C07C45/783

  by gas-liquid treatment, e.g. by gas-liquid absorption · CPC title