PROCESS FOR PREPARING ACRYLIC ACID PURIFIED BY CRYSTALLIZATION FROM HYDROXYPROPIONIC ACID AND APPARATUS THEREFORE

• US 20110105791A1
• Filed: 08/22/2007
• Published: 05/05/2011
• Est. Priority Date: 08/22/2006
• Status: Active Grant

• Current Assignee: Evonik Superabsorber GmbH
• Original Assignee: Evonik Degussa GmbH
• Inventors: Bub, Günther, Sabbagh, Andreas, Mosler, Jürgen, Hengstermann, Axel, Stochniol, Guido, Kuppinger, Franz-Felix
• Granted Patent: US 8,198,481 B2
• Time in Patent Office: Days
• US Class Current: 562/599
• CPC Class Codes: C07C 51/377 by splitting-off hydrogen or functional groups; by hydrogenolysis of functional groups C07C51/36 - C07C51/373 take precedence
• CPC Class Codes: C07C 51/43 by change of the physical state, e.g. crystallisation
• CPC Class Codes: C07C 57/04 Acrylic acid; Methacrylic acid
• CPC Class Codes: C08F 120/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: Y02P 20/10 Process efficiency

Abstract

The invention relates to a process for the preparation of acrylic acid and a process for the preparation of polyacrylic acid comprising the process steps: (a1) preparation of 3-hydroxypropionic acid from a biological material to give a fluid, in particular aqueous, phase containing 3-hydroxypropionic acid; (a2) dehydration of the 3-hydroxypropionic acid to give a fluid, in particular aqueous, solution containing acrylic acid; (a3) purification of the solution containing acrylic acid by a suspension crystallization or a layer crystallization to give a purified phase; and corresponding devices for carrying out these processes, and acrylic acid and polyacrylates. The invention is distinguished in that acrylic acid and polyacrylates can thereby be prepared efficiently, inexpensively, and sustainably with simple means and with a high purity on the basis of regenerable raw materials.

Claims

1. A process for the preparation of acrylic acid, comprising the process steps:

(a1) provision of a fluid F1 containing a hydroxypropionic acid, aqueous phase P1,

(a2) dehydration of said hydroxypropionic acid to give a fluid F2 containing acrylic acid, aqueous phase P2,

(a3) purification of said fluid F2 containing acrylic acid, said aqueous phase P2, by crystallization to give a purified phase.

2. The process according to claim 1, wherein said fluid F1 is obtained by a process comprising the process steps:

i) preparation of 3-hydroxypropionic acid from a biological material to give an aqueous phase containing hydroxypropionic acid and microorganisms,

ii) optionally killing of said microorganisms,

iii) separating off of solids from said aqueous phase.

3. The process according to claim 1, wherein said fluid F1 is aqueous, and has a composition comprising

(C1-1) from about 1 to about 40 wt. % of hydroxypropionic acid, salts thereof, or mixtures thereof,

(C1-2) from about 0.1 to about 5 wt. % of inorganic salts,

(C1-3) from about 0.1 to about 30 wt. % of organic compounds which differ from hydroxypropionic acid,

(C1-4) from 0 to about 50 wt. % of solids, and

(C1-5) from about 20 to about 90 wt. % of water,

wherein the sum of components (C1-1) to (C1-5) is 100 wt. %.

4. The process according to claim 1, wherein said dehydration comprises a reactive distillation.

5. The process according to claim 1, wherein said dehydration is carried out in at least two reactors, comprising the following process steps:

i) heating of said aqueous phase P1 in at least one first reactor R1 in the presence of a homogeneous or heterogeneous catalyst to give a first aqueous fluid F1-1 containing acrylic acid under a pressure Π

1;

ii) introduction of said fluid F1-1 into a further reactor R2; and

iii) heating of said fluid F1-1 introduced into said reactor R2 in the presence of a catalyst under a pressure Π

2 to give a fluid F1-2,

wherein said pressure Π

2 and said pressure Π

1 are not equal.

6. The process according to claim 5, wherein said pressure Π

2 is lower than said pressure Π

1.

7. The process according to claim 1, wherein said dehydration is carried out in a CO₂ atmosphere, or an inorganic acid, or both.

8. The process according to claim 1, wherein said crystallization is selected from the group consisting of a suspension crystallization or a layer crystallization.

9. The process according to claim 1, wherein said aqueous phase P2 is cooled to a maximum to the temperature of the triple eutectic point of a composition of acrylic acid, water and hydroxypropionic acid.

10. The process according to claim 7, wherein a first crystal phase containing:

i) at least about 5 wt. % of acrylic acid,

ii) at least about 40 wt. % of water, and

iii) at most about 10 wt. % of hydroxypropionic acid is obtained.

11. The process according to claim 8, wherein the purification is carried out by an at least two-stage crystallization.

12. The process according to claim 1, wherein process step (a3) comprises the following process steps:

(a3-1) crystallization of said fluid F2 in a first crystallization stage to give a crystal phase K1 and a mother liquor M1, wherein said crystal phase K1 comprises;

i) from about 5 to about 60 wt. % of acrylic acid,

ii) from 39.9 to about 95 wt. % of water, and

iii) from about 0.1 to about 10 wt. % of by-products which differ from water and acrylic acid,

and wherein the sum of the amounts by weight of acrylic acid, water and by-products is 100 wt. %,

(a3-2) separating off of said crystal phase K1 from said mother liquor M1,

(a3-3) melting of said crystal phase K1 from said first crystallization stage,

(a3-4) renewed crystallization of said melted crystal phase K1 in a second crystallization stage to give a crystal phase K2 and a mother liquor M2, wherein said crystal phase K2 comprises;

i) from about 8 to about 35 wt. % of acrylic acid,

ii) from about 60 to about 90 wt. % of water, and

iii) from about 2 to about 5 wt. % of by-products which differ from water and acrylic acid,

wherein the sum of the amounts by weight of acrylic acid, water and by-products is 100 wt. %,

(a3-5) separating off of said crystal phase K2 from said mother liquor M2,

(a3-6) crystallization of said mother liquor M2 in a third crystallization stage to give a crystal phase K3 and a mother liquor M3, wherein said crystal phase K3 comprises;

i) from about 25 to about 55 wt. % of acrylic acid,

ii) from 44.5 to about 70 wt. % of water, and

iii) from about 0.5 to about 5 wt. % of by-products which differ from water and acrylic acid,

wherein the sum of the amounts by weight of acrylic acid, water and by-products is 100 wt. %, and

(a3-7) separating off of said crystal phase K3 from said liquor M3, a purified phase containing acrylic acid crystals being obtained.

13. The process according to claim 12, wherein the mother liquor obtained in process step (a3-2) is fed back into step (a1).

14. The process according to claim 1, wherein said purified phase has a purity of at least about 40% with respect to said acrylic acid.

15. The process according to claim 1, wherein said hydroxypropionic acid in said fluid F1 or the acrylic acid in said fluid F2 is converted into its protonated form by the addition of acids before carrying out at least one of process steps (a2) or (a3).

16. The process according to claim 1, wherein said hydroxypropionic acid is 2-hydroxypropionic acid.

17. (canceled)

18. A device for the preparation of acrylic acid, comprising the following units and stages, wherein said units and stages are connected to one another by fluid-carrying lines:

i) a synthesis unit for the preparation of hydroxypropionic acid,

ii) a dehydration stage for conversion of the hydroxypropionic acid into acrylic acid, followed by

iii) a crystallizing unit.

19-31. -31. (canceled)