GB1008314A - Production of cycloalkanones - Google Patents

Abstract

Cycloalkanones are made from their corresponding cycloalkanes by liquid phase oxidation with gaseous molecular oxygen in the presence of an oxygen-containing boron compound, which is capable of reacting with the cyclo-alkanols formed under the prevailing reaction conditions to form esters, followed by the dehydrogenation of the cycloalkanols formed. Preferably, the oxidation reaction is carried out at 75-300 DEG C. using air and a catalyst, such as cobalt naphthenate or manganese naphthenate, water formed during the reaction being removed by distillation as a cycloalkane-water azeotrope. Preferably, at the completion of the oxidation reaction, excess cycloalkane is removed, e.g. by distillation either before or after the cycloalkanol is liberated by hydrolysis, which is preferred, alcoholysis or transesterification. The cycloalkanol thus obtained, and from which boron compound has been removed, is dehydrogenated preferably at a temperature in the range of 325-425 DEG C. and at a pressure between 2-45 p.s.i.a. in the presence of a catalyst of zinc oxide, to form the corresponding cycloalkanone. Desirably the cyclo-alkanol fraction is treated with a dilute aqueous alkaline solution, e.g. of caustic soda, before dehydrogenation is effected. Boron compounds specified are boric acid, metaboric acid, tetraboric acid, boron oxide, methyl borate, ethyl borate, ethyl metaborate, ethyl triborate and ethyl boric acid. The quantity of boron compound used is desirably at least sufficient to provide the equivalent of 1 mol. of boric acid (as H3BO3) per mol. of cycloalkanol formed in the oxidation reaction. Five examples are given, illustrating the increased yield of cyclohexanone and methylcyclohexanone obtained when using different quantities of boric acid and boron oxide as compared with a comparative example in which no boron compound is present. Specifications 996,791 and 996,792 are referred to.