Process for the oxidative purification of terephthalic acid

• US 20060128987A1
• Filed: 02/02/2006
• Published: 06/15/2006
• Est. Priority Date: 12/09/2002
• Status: Active Grant

• Current Assignee: Alpek Polyester SA de CV
• Original Assignee: Eastman Chemical Company
• Inventors: O'Meadhra, Ruairi Seosamh, Woodruff, Thomas Earl, Lin, Robert, Sheppard, Ronald Buford, Tennant, Brent Alan
• Granted Patent: US 7,358,392 B2
• Time in Patent Office: Days
• US Class Current: 562/410
• CPC Class Codes: C07C 51/43 by change of the physical state, e.g. crystallisation
• CPC Class Codes: C07C 51/487 by treatment giving rise to chemical modification by chemisorption C07C51/47
• CPC Class Codes: C07C 63/26 1,4 - Benzenedicarboxylic acid

Abstract

Disclosed is a process to produce a purified carboxylic acid slurry. The process comprises removing impurities from a crystallized product in a solid liquid displacement zone to form the purified carboxylic acid slurry. The process produces purified carboxylic acid slurry having good color and low impurity levels without the use of purification steps like hydrogenation or an impurity removal process.

Claims

1. A process to produce a purified carboxylic acid slurry said process comprising:

(a) oxidizing an aromatic feedstock in a primary oxidation zone to form a crude carboxylic acid slurry;

(b) oxidizing said crude carboxylic acid slurry in a staged oxidation zone to form a staged oxidation product;

wherein said staged oxidation zone comprises at least one staged oxidation reactor operated at a temperature of about 150°

C. to about 280°

C.

(c) crystallizing in a crystallization zone said purified staged oxidation product to form a crystallized product;

(d) removing in a solid liquid displacement zone impurities from said crystallized product to form said purified carboxylic acid slurry.

2. The process according to claim 1 wherein said solid liquid displacement zone comprises a solid liquid separator that is operated at a temperature between about 110°

C. to about 200°

C.

3. The process according to claim 1 wherein said crude carboxylic acid slurry comprising terephthalic acid, catalyst, and acetic acid.

4. The process according to claim 1 wherein said solid liquid displacement zone comprises a solid liquid separator selected from the group consisting of a belt filter, a rotary vacuum filter and a rotary disk pack centrifuge.

5. The process according to claim 1 wherein said purified slurry is formed without a process for separating impurities from oxidation solvent or hydrogenation step.

6. The process according to claim 1 wherein said purified slurry has a b* of less than about 3.5.

7. The process according to claim 1 further comprising the step of flash cooling said purified terephthalic acid slurry to form a cooled purified slurry.

8. The process according to claim 1 wherein said staged oxidation reactor is operated at a temperature of about 190°

C. to about 280°

C.

19. The process according to claim 1, 9 or 17 further comprising decolorizing in a reactor zone said purified carboxylic acid slurry or a carboxylic acid that has been esterified.

21. The process according to claim 1, 9, or 17 wherein said solid liquid displacement zone comprises a solid liquid separator that is operated at a temperature between about 50°

C. to about 200°

C.

9. A process to produce a purified carboxylic acid slurry said process comprising:

(a) oxidizing an aromatic feedstock in a primary oxidation zone to form a crude carboxylic acid slurry;

(b) oxidizing said crude carboxylic acid slurry in a staged oxidation zone to form a staged oxidation product;

wherein said staged oxidation zone comprises at least one staged oxidation reactor operated at a temperature of about 150°

C. to about 280°

C.

(c) removing in a solid liquid displacement zone impurities from said crystallized product to form said purified carboxylic acid slurry.

(d) crystallizing in a crystallization zone said purified staged oxidation product to form a crystallized product;

10. The process according to claim 9 wherein said solid liquid displacement zone comprises a solid liquid separator that is operated at a temperature between about 110°

C. to about 200°

C.

11. The process according to claim 9 wherein said crude carboxylic acid slurry comprising terephthalic acid, catalyst, and acetic acid.

12. The process according to claim 9 wherein said solid liquid displacement zone comprises a solid liquid separator selected from the group consisting of a belt filter, a rotary vacuum filter and a rotary disk pack centrifuge.

13. The process according to claim 9 wherein said purified slurry is formed without a process for separating impurities from oxidation solvent or hydrogenation step.

14. The process according to claim 9 wherein said purified slurry has a b* of less than about 3.5.

15. The process according to claim 9 further comprising the step of flash cooling said purified terephthalic acid slurry to form a cooled purified slurry.

16. The process according to claim 9 wherein said oxidation reactor is operated at a temperature of about 190°

C. to about 280°

C.

18. The process according to claim 9 further comprising the step of flash cooling said purified carboxylic acid slurry to form a cooled purified slurry.

17. A process to produce a purified carboxylic acid slurry comprising:

(a) oxidizing an aromatic feedstock in a primary oxidation zone to form a crude carboxylic acid slurry;

wherein said oxidizing is conducted at a temperature between about 110°

C. to about 200°

C.;

(b) oxidizing said crude carboxylic acid slurry in a staged oxidation zone to form a staged oxidation product;

wherein said oxidizing is conducted at a temperature between about 150°

C. to about 280°

C.; and

wherein said oxidizing is at a higher temperature in said staged oxidation zone than in said primary oxidation zone;

(c) crystallizing said staged oxidation product in a crystallization zone to form a crystallized product; and

(d) removing in a solid liquid displacement zone impurities from said crystallized product to form said purified carboxylic acid slurry;

wherein said solid liquid displacement zone comprises a solid liquid separator that is operated at a temperature between about 110°

C. to about 200°

C.

20. The process according to claim 17 wherein said decolorizing is accomplished by reacting said crude carboxylic acid solution with hydrogen in the presence of a catalyst in a reactor zone to produce a decolorized carboxylic acid solution.

22. The process according to claim 17 wherein said staged oxidation zone comprises at least one staged oxidation reactor operated at a temperature of about 190°

C. to about 280°

C.