PURPOSE: To recover high-purity gamma-butyrolactone by subjecting a mixture contg. gamma-butyrolactone and a small amt. of diethyl succinate to fractional distillation in the presence of diethyl ethoxysuccinate.
CONSTITUTION: Maleate is removed from the reaction product obtd. by subjecting a 4C-dicarboxylic acid ester to hydrogenation in the presence of a heterogeneous ester hydrogenation catalyst and thereafter the product is distilled in one or more stages of distillation, by which the fraction of distillation contg. a major molar amt. (99 to 75 mol.%) of the gamma-butyrolactone and a minor molar amt. (1 to 25 mol.%) of diethyl succinate is obtd. The mixture is supplied to the intermediate part of a fractionation column and the ethoxysuccinate is supplied to a part of the distillation column in the upper part of the intermediate part to subject the ethoxysuccinate to fraction distortion. The gamma-butyrolactone is recovered as an overhead vaporous product. The diethyl succinate and diethyl ethoxysuccinate are recovered as liquid bottom products. These products are respectively circulated to a reaction stage and a fractional distillation stage.