Process and device for purifying benzoic acid

摘要

Process for purifying benzoic acid obtained by oxidation of toluene with a gas containing molecular oxygen, which purification is carried out at a pressure of at least 3 MPa by means of a supercritical extraction using a gas or gas mixture the critical temperature of which is lower than 435 K. The process being characterized in that the benzoic acid to be purified is supplied in a liquid state to a crystallizer in which the prevailing temperatures is below the solidification temperature of the benzoic acid and in which the benzoic acid is treated during and possibly after the crystallization process with the said gas or gas mixture.