GB935029A - Oxidation process for the production of epsilon-hydroxycaproic acid - Google Patents

Abstract

e -Hydroxycaproic acid is produced by subjecting a liquid mixture of cyclohexane, cyclohexanol and cyclohexanone to reaction with gaseous oxygen to give a mixture containing cyclohexane, cyclohexanol, cyclohexanone and e -hydroxycaproic acid, adding water to obtain an aqueous extract containing e -hydroxycaproic acid, and returning the cyclohexane, cyclohexanol and cyclohexanone for oxidation together with additional cyclohexane. The process may be operated as a continuous process. An oxidation catalyst may be present, e.g. Co, Mn, Fe, Cr, Ni and Cu or their compounds. The preferred reaction temperature is 100-200 DEG C.; pressures of 50-1000 psig may be used. The reaction mixture may be contacted with water at elevated temperature, e.g. 30-150 DEG C., or at lower temperature and the mixture heated; the phases may then be allowed to separate, the upper phase being returned to the reactor and the lower aqueous phase heated to distil therefrom a water-cyclohexanol-cyclohexanone azeotrope leaving aqueous hydroxycaproic acid solution, or the whole of the mixture may be heated to distil off said azeotrope. Some adipic acid is also produced.