GB1006945A - Production of adipic acid - Google Patents

Abstract

Adipic acid is produced by contacting a cyclohexanone-containing substrate in an oxidation zone with a gaseous molecular oxygen stream in the presence of a manganese compound as catalyst at a temperature of from 60 DEG to 105 DEG C. and an oxygen partial pressure of from 1 to 30 p.s.i.a. and recovering adipic acid from the reaction mixture, the peak oxygen reaction rate being controlled such that it is at least 0.002 gm. mols./100 gms.substrate/min. when the reaction temperature prior to achieving the peak rate is 60 DEG C. or higher, at least 0.004 gm. mols./100 gms. substrate/min. when the reaction temperature prior to achieving the peak rate is 70 DEG C. or higher and at least 0.008 gm. mols./100 gms. substrate/min. when the reaction temperature prior to achieving the peak rate is 80 DEG C. or higher. The peak oxygen reaction rate may be controlled by altering the rate of flow of the molecular oxygen into the oxidation zone, or by adjusting the amount of mechanical agitation provided or by a combination of both methods. The substrate may be obtained by reacting cyclohexane with molecular oxygen at a temperature of from 125 DEG to 175 DEG C. at a pressure of 55 to 500 p.s.i.g., and removing unreacted cyclohexane; cyclohexanol and adipic acid are obtained in addition to cyclohexanone. The process of the invention is preferably carried out in the presence of a liquid reaction medium and the catalyst, which is normally a manganese salt and may include a copper salt as well, should be in a form soluble in the liquid reaction medium. Examples are given, together with comparative examples having peak oxygen reaction rates below the values specified above. Reference has been directed by the Comptroller to Specifications 941,662, 946,382 and 956,779.