Process for production of a carboxylic acid/diol mixture suitable for use in polyester production

• US 7,276,625 B2
• Filed: 10/15/2002
• Issued: 10/02/2007
• Est. Priority Date: 10/15/2002
• Status: Expired due to Term

• Current Assignee: Alpek Polyester SA de CV
• Original Assignee: Eastman Chemical Company
• Inventors: Lin, Robert
• Primary Examiner(s): OH, TAYLOR V
• Application Number:
  US10/271,058
• Publication Number:
  US 20040073059A1
• Time in Patent Office: 1,813 Days
• Field of Search: 560/76, 560/224, 562/412, 562/487, 562/485, 562/416
• US Class Current: 562/485
• CPC Class Codes: C07C 51/43 by change of the physical state, e.g. crystallisation
• CPC Class Codes: C07C 51/47 by solid-liquid treatment; by chemisorption
• 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
• CPC Class Codes: C07C 67/08 by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
• CPC Class Codes: C07C 69/82 Terephthalic acid esters

Abstract

In this invention, a process is provided by which a carboxylic acid/diol mixture suitable as starting material for a polyester production is obtained from a decolorized carboxylic acid solution without isolation of a substantially dry carboxylic acid solid. More specifically, in this invention, a process is provided by which a terephthalic acid/ethylene glycol mixture suitable as starting material for a polyester production is obtained from a decolorized terephthalic acid solution without isolation of a substantially dry terephthalic acid solid.

Claims

1. A process for producing a carboxylic acid/diol mixture, said process comprising adding a decolorized carboxylic acid composition comprising a carboxylic acid and water in an esterification reactor zone and adding a diol to said decolorized carboxylic acid composition in said esterification zone;

wherein said diol is added to remove a portion of said water by vaporization from said decolorized carboxylic acid composition to form said carboxylic acid/diol mixture comprising a hydroxy alkyl ester.

2. A process according to claim 1 wherein said carboxylic acid is selected from a group consisting of terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, and mixtures thereof.

5. A process according to claim 1 or 3 wherein said diol is selected from the group consisting of ethylene glycol, diethylene glycol, n-butylene glycol, i-butylene glycol, n-propylene glycol, 1,4 butanediol, cyclohexanedimethanol, and mixtures thereof.

7. A process according to claim 1 wherein said carboxylic acid is terephthalic acid.

3. A process for producing a carboxylic acid/diol mixture, said process comprising:

(a) mixing a crude carboxylic acid powder with water in a mixing zone to form a crude carboxylic acid solution;

wherein said carboxylic acid is selected from a group consisting of terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, and mixtures thereof;

(b) decolorizing said crude carboxylic acid composition in a reactor zone to produce a decolorized carboxylic acid composition;

(c) optionally, flashing said decolorized carboxylic acid composition in a flashing zone to remove a portion of the water from said decolorized carboxylic acid composition; and

(d) adding said decolorized carboxylic acid composition comprising a carboxylic acid and water in an esterification reactor zone and adding a diol to said decolorized carboxylic acid composition in said esterification zone;

wherein said diol is added to remove a portion of the water by vaporization from said decolorized carboxylic acid composition to form said carboxylic acid/diol mixture comprising a hydroxy alkyl ester.

4. A process according to claim 3 wherein said decolorizing is accomplished by reacting said crude carboxylic acid composition with hydrogen in the presence of a catalyst in a reactor zone to produce said decolorized carboxylic acid composition;

wherein said catalyst comprises a group VIII metal or combination thereof.

6. A process according to claim 4 wherein said catalyst in said reactor zone comprises a group VIII metal or combination thereof.

8. A process for producing a terephthalic acid/diol mixture, said process comprising:

(a) mixing a crude terephthalic acid powder with water in a mixing zone to form a crude terephthalic acid composition;

(b) decolorizing said crude terephthalic acid composition in a reactor zone to form a decolorized terephthalic acid composition;

(c) optionally, flashing said decolorized terephthalic acid composition in a flashing zone to remove a portion of the water from said decolorized terephthalic acid composition; and

(d) adding said decolorized terephthalic acid composition comprising terephthalic acid and water in an esterification reactor zone and adding a diol to said decolorized carboxylic acid composition in said esterification zone;

wherein said diol is added to remove a portion of the water by vaporization to form said terephthalic acid/diol mixture comprising a hydroxy alkyl ester.

9. A process according to claim 8 wherein said decolorizing is accomplished by reacting said crude terephthalic acid composition with hydrogen in the presence of a catalyst in said reactor zone to produce a said decolorized terephthalic acid composition;

wherein said catalyst comprises a group VIII metal or combination thereof.

10. A process according to claim 8 wherein said crude terephthalic acid powder contains a concentration of p-toluic acid and 4-carboxybenzaldehyde less than about 900 ppm by weight.

11. A process according to claim 8 wherein said diol is selected from the group consisting of ethylene glycol, diethylene glycol, n-butylene glycol, i-butylene glycol, n-propylene glycol, 1,4 butanediol, cyclohexanedimethanol, and mixtures thereof.

12. A process according to claim 8 wherein said diol is ethylene glycol.

13. A process according to claim 8 wherein said crude terephthalic powder has a b* color less than about 7.

14. A process according to claim 8 wherein said mixing occurs at a pressure between about 900 psia to about 1400 psia.

15. A process according to claim 8 wherein the concentration of crude terephthalic acid in said crude terephthalic acid composition is in a range between about 15% to about 35% by weight.

16. A process according to claim 9 wherein said reacting occurs at a temperature greater than about 230°

C.

17. A process according to claim 9 wherein said reacting occurs at a pressure between about 900 psia to about 1400 psia.

18. A process according to claim 9 wherein said reacting occurs at a hydrogen flow rate of about 1.5 times the molar ratio necessary to convert 4-carboxybenzaldehyde to p-toluic acid in said crude terephthalic acid composition.

19. A process according to claim 9 wherein said catalyst in said reactor zone comprises a group VIII metal or combination thereof.

20. A process according to claim 8 wherein said flashing occurs at a temperature greater than about 150°

C.

21. A process according to claim 8 wherein said flashing occurs at a pressure between about 75 psia to about 1400 psia.

22. A process according to claim 8 wherein said adding occurs at a temperature greater than about 240°

C.

23. A process according to claim 8 wherein said diol is introduced into said esterification reactor zone at a temperature between about 150°

C. to about 300°

C.

24. A process according to claim 8 wherein said adding occurs at a pressure between about 40 psia to about 100 psia.

25. A process for producing a terephthalic acid/ethylene glycol mixture, said process comprising:

(a) mixing a crude terephthalic acid powder with water in a mixing zone to form a crude terephthalic acid composition wherein said mixing zone is operated at a temperature greater than about 230°

C., wherein the pressure in said mixing zone is in a range of about 900 psia to about 1400 psia;

wherein the concentration of said crude terephthalic acid in said crude terephthalic acid composition is in a range of about 15% to about 35% by weight;

wherein the color of said crude terephthalic acid powder is less than about 7 measured by b*;

wherein the total concentration of p-toluic and 4-carboxybenzaldehyde in said crude terephthalic acid powder is less than about 900 ppm by weight;

(b) decolorizing said crude terephthalic acid composition with hydrogen in a reactor zone in the presence of a catalyst to form a decolorized terephthalic acid composition;

wherein said catalyst comprises a group VIII metal or combination thereof;

wherein said hydrogen is introduced into said reactor zone at a flow rate of about 1.5 times the molar ratio necessary to convert 4-carboxybenzaldehyde to p-toluic acid in said crude terephthalic acid composition;

wherein said reacting occurs at a temperature greater than about 230°

C., wherein said reacting occurs at a pressure between about 900 psia to about 1400 psia;

(c) optionally, flashing said decolorized terephthalic acid composition in a flashing zone to remove a portion of water from said decolorized terephthalic acid composition wherein said flashing zone comprises at least one flash vessel operated at a pressure in the range of about 75 psia to about 1400 psia; and

wherein said vessel is operated at a temperature in a range greater than about 150°

C.; and

(d) adding said decolorized terephthalic acid composition in an esterification reactor zone and adding a diol to said decolorized carboxylic acid composition in said esterification zone to remove a portion of water by vaporization to form said terephthalic acid/ethylene glycol mixture comprising a hydroxy alkyl ester;

wherein said diol is ethylene glycol at a temperature in a range of about 150°

C. to about 300°

C.