| abstract |
(57) Abstract: In the purification of crude naphthalenedicarboxylic acid, formylnaphthoic acid, which is a typical impurity in it, is changed from -CHO to -COOH, thereby improving purity and yield all at once. To do. SOLUTION: Crude naphthalenedicarboxylic acid is oxidized with molecular oxygen in a high temperature aqueous reaction medium in the presence of a noble metal catalyst such as platinum to a carboxyl group from a substituent in an incomplete oxidation step in the crude product. At least 0.5 mol, preferably 1 mol or more, relative to 1 mol of oxygen molecules required for It works in the range up to 15 mol. Next, hydrogen is allowed to act on the naphthalenedicarboxylic acid that has been subjected to this oxidation treatment, also in the presence of a noble metal catalyst, in the aqueous reaction medium. After the hydrogenation treatment, naphthalenedicarboxylic acid is crystallized from the reaction product solution and collected to obtain a purified product. |