PROCESS FOR PREPARING 1,6 HEXANEDIOL AND CAPROLACTONE

The invention relates to a process for preparing 1,6 hexane diol and .epsilo n.- caprolacton from a carboxylic acid mixture containing adipic acid, 6-hydroxy caproic acid and, in small quantities, 1,4 cyclohexane diols . Said mixture is obtained as a by-product of the oxidation of cyclohexane into cyclohexanone/ cyclohexanol with oxygen or gases containing oxygen, by water extraction of the reaction mixture. Said process involves esterification and hydrogenation of a partial stream into hexane diol and cyclization of 6-hydroxy caproic acid esters into caprolacton. According to this process: (a) the monocarboxylic acids and the dicarboxylic acids contained in the aqueous reaction mixture are reacted with a low-molecular alcohol to form the corresponding carboxyli c acid esters; (b) the excess alcohol, water and low-boiling agents of the resultant esterification mixture are released in a first distillation stage; (c) separating into a ester fraction substantially free of 1,4 cyclohexane diols, and a fraction containing at least the greater par t of the 1,4 cyclohexane diols is carried out from the bottom product in a second distillation stage; (d) at least part of a stream substantially containing 6-hydroxy caproic acid ester is separated from the ester fraction in a third distillation stage; (e) the ester fraction fro m (d), from which 6-hydroxy caproic acid ester was at least partially removed, is hydrogenated catalytically and 1,6 hexane diol is extracted by distilling the hydrogenated product in a known manner, and (f) the stream substantially containing 6-hydroxy caproic acid ester is heat ed to temperatures above 200 .degree.C at reduced pressure, thereby causing cyclization of 6-hydroxy caproic acid ester to form caprolacton, and pure e-caprolacton is recovered from the cyclization product by distillation.