Patent ID: 6717009
Filing Date: 2004-04-06
Classification: C07C

Abstract:
A method for making a high purity naphthalenedicarboxylic acid comprising:Step [I]: dissolving a raw mixture of crude terephthalic acid and crude naphthalenedicarboxylic acid into high-temperature high-pressure water to form a dibasic acid solution wherein the crude naphthalenedicarboxylic acid content is 0.1 to 10 weight percent of the crude terephthalic acid content, and bringing the dibasic acid solution into contact with hydrogen in the presence of a catalyst of at least one Group VIII noble metal; and Step [II]: crystallizing the resultant treated dibasic acid mixture from solution in multiple stages while reducing the temperature and the pressure for each stage and obtaining acid mixtures containing enriched naphthalenedicarboxylic acid and/or enriched terephthalic acid by solid-liquid separation.