Purification of carboxylic acids by complexation with selective solvents
First Claim
1. A method of purifying a carboxylic acid from a crude mixture comprising one or more carboxylic acids, the method comprising:
- contacting the crude mixture with a selective crystallization solvent at a temperature and time effective to form a slurry of a salt complex of the carboxylic acid and the selective crystallization solvent without completely dissolving the carboxylic acid; and
recovering the salt complex.
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Abstract
A method and apparatus for purifying carboxylic acids is disclosed. A mixture containing crude carboxylic acid is contacted with a selective crystallization solvent to form a slurry of a salt complex of the carboxylic acid and the selective crystallization solvent. The salt complex is recovered and optionally processed to recover the free carboxylic acid. The method and apparatus of the invention is particularly suitable for purifying aromatic dicarboxylic acids such as terephthalic acid. The present invention also reduces contamination by carboxybenaldehyde isomers in crude phthalic acids by oxidizing the carboxybenzaldehyde to the corresponding phthalic acid.
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Citations
23 Claims
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1. A method of purifying a carboxylic acid from a crude mixture comprising one or more carboxylic acids, the method comprising:
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contacting the crude mixture with a selective crystallization solvent at a temperature and time effective to form a slurry of a salt complex of the carboxylic acid and the selective crystallization solvent without completely dissolving the carboxylic acid; and recovering the salt complex. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 23)
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22. A method for recovering purified terephthalic acid from the effluent of a terephthalic acid production process, the method comprising:
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contacting said effluent in a first crystallization vessel with a selective crystallization solvent to produce a slurry of a salt complex of terephthalic acid and the crystallization solvent without completely dissolving the terephthalic acid in the selective crystallization solvent; filtering said slurry to provide a solid salt complex and a mother liquor; decomposing or dissolving the solid salt complex with a selective crystallization solvent in a second crystallization vessel at a temperature of about 65 to about 300°
C. to yield a second crystallization slurry or solution;reducing the temperature of the second crystallization solution to about 60 to about 185°
C. to crystallize free terephthalic acid; andrecovering the free terephthalic acid.
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Specification