Process for production of a carboxylic acid/diol mixture suitable for use in polyester production
View Patent ↗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.
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.
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.
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.
6. A process according to claim 4 wherein said catalyst in said reactor zone comprises a group VIII metal or combination thereof.
7. A process according to claim 1 wherein said carboxylic acid is terephthalic acid.
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.