Method for separating and purifying adipic acid

A process for treating the reaction mixture resulting from the direct oxidation of cyclohexane to adipic acid with molecular oxygen in an organic solvent in the presence of a catalyst, said process comprising:

• (a) separating the reaction mixture into two liquid phases by settling to form an upper phase comprising cyclohexane, and a lower phase comprising an organic solvent, diacids formed during the oxidation reaction, a catalyst and a portion of other reaction products and unconvcrted cyclohexane:
• (b) distilling said lower phase to provide (i) a distillate comprising at least a portion of the most volatile compounds and (ii) a distillation bottoms comprising the diacids formed and the catalyst;
• (c) separating the catalyst from the distillation bottoms;
• (d) purifying the adipic acid in an aqueous solution, said purifying step consisting essentially of a reducing and/or an oxidizing purification treatment;
• (e) crystallizing the adipic acid from water, preceding or following purification step (d), if crystallization has not been carried out in order to separate the catalyst from the distillation bottoms;
• and
• (f) recrystallizing the adipic acid from water.