Process for the oxidative purification of terephthalic acid
First Claim
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1. A process to produce a purified carboxylic acid slurry, said process comprising removing impurities from a crystallized product in a solid liquid displacement zone to form said purified carboxylic acid slurry;
- wherein said purified carboxylic acid slurry has a b* of less than 3.5;
wherein said purified carboxylic acid slurry is formed without a hydrogenation step.
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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.
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Citations
31 Claims
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1. A process to produce a purified carboxylic acid slurry, said process comprising removing impurities from a crystallized product in a solid liquid displacement zone to form said purified carboxylic acid slurry;
- wherein said purified carboxylic acid slurry has a b* of less than 3.5;
wherein said purified carboxylic acid slurry is formed without a hydrogenation step. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- wherein said purified carboxylic acid slurry has a b* of less than 3.5;
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2. A process to purify a staged oxidation product said process comprising removing impurities from said staged oxidation product in a solid liquid displacement zone to form a purified staged oxidation product;
- wherein said purified staged oxidation product has a b* of less than 3.5;
wherein said purified staged oxidation product is formed without a hydrogenation step.
- wherein said purified staged oxidation product has a b* of less than 3.5;
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13. A process to produce a purified carboxylic acid slurry said process comprising removing in a solid liquid displacement zone impurities from a 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 140°
C. to about 160°
C.;
wherein said solid liquid separator is operated in a continuous mode;
wherein said solid liquid separator is operated at a pressure less than 70 psia;
wherein said purified carboxylic acid slurry has a b* of less than 3.5. - View Dependent Claims (14, 15, 16, 17, 29, 30)
- wherein said solid liquid displacement zone comprises a solid liquid separator that is operated at a temperature between about 140°
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18. A process to produce a purified carboxylic acid slurry said process comprising:
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(a) optionally removing impurities from a crude carboxylic acid slurry in an optional solid liquid displacement zone to form a slurry product;
(b) oxidizing said slurry product or said crude carboxylic acid slurry in a staged oxidation zone to form a staged oxidation product;
(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. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 31)
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19. A process to produce a purified carboxylic acid slurry said process comprising:
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(a) optionally, removing impurities from a crude carboxylic acid slurry in an optional solid liquid displacement zone to form a slurry product;
(b) oxidizing said slurry product or crude carboxylic acid slurry in a staged oxidation zone to form a staged oxidation product;
(c) removing in a solid liquid displacement zone impurities from said staged oxidation product to from a purified staged oxidation product; and
(d) crystallizing in a crystallization zone said purified staged oxidation product to form said purified carboxylic acid slurry.
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27. A process to produce a purified carboxylic acid slurry comprising:
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(a) removing in an optional solid liquid displacement zone impurities from a crude carboxylic acid slurry to form a slurry product;
wherein said crude carboxylic acid slurry comprises terephthalic acid, catalyst, acetic acid, and impurities that is withdrawn at a temperature between about 140°
C. and about 170°
C. from the oxidation of paraxylene in a primary oxidation zone;
(b) oxidizing said slurry product in a staged oxidation zone to form a staged oxidation product;
wherein said oxidizing is conducted at a temperature between about 190°
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. - View Dependent Claims (28)
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Specification