PRODUCTION OF PYRIDINECARBOXYLIC ACID

摘要

PROBLEM TO BE SOLVED: To obtain a pyridine carboxylic acid useful as a starting substance for feed additives and medicines by reducing the bromine impurities in the crude pyridinecarboxylic acid prepared by liquid-phase oxidation of alkylpyridine. SOLUTION: An alkylpyridine such as 3-methylpyridine is liquid-phase oxidized with an oxygen-containing gas at 150-250 deg.C under a pressure of 10-30kg/ cm<2> G. The reaction mixture without isolation of crude pyridinecarboxylic acid is catalytically hydrogenated in the presence of a metal of group VIII (for example, Pd on activated carbon) at 100-250 deg.C under a hydrogen partial pressure of 1-80kg/cm<2> G, then the pyridinecarboxylic acid is separated from the reaction mixture. The impurities containing bromine is largely reduced the operation of separation of crude pyridinecarboxylic acid becomes unnecessary and the twice crystallization operation can be reduced to once. Thus, the loss of pyridinecarboxylic acid dissolved in the solvent used in purification is reduced to increase the yield.