Patent ID: 7319168

Claim:
A process for producing aliphatic carboxylic acid, which comprises an azeotropic distillation step of supplying an aqueous aliphatic carboxylic acid solution and an azeotropic solvent to an azeotropic distillation column to perform distillation, separating an azeotrope containing the azeotropic solvent and water as a distillate, and recovering aliphatic carboxylic acid with a reduced water content as bottom liquid, characterized in that a target value 2 of an amount of the azeotropic solvent to be supplied is set depending on an amount of water in the aqueous aliphatic carboxylic acid solution supplied to the azeotropic distillation column and wherein said target value 2 is determined by setting a target value 1 of the water concentration in a column top vapor, and by calculating mass balance of the azeotropic distillation column, and controlling the amount of the azeotropic solvent to be supplied at the target value 2 .