Process for producing diol

Abstract

A process for producing a diol by reacting an acetic ester of butanediol or butenediol with methanol, which comprises (a) continuously feeding to a first reaction-distilling column from its upper part a liquid acetic ester of butanediol or butenediol, while continuously feeding methanol to said column from its lower part, to bring both feeds into counter current gas-liquid contact in the presence of an acidic or a basic catalyst, to allow both feeds to react, and withdrawing from the bottom a bottom stream comprising a diol as major constituent, (b) continuously feeding to a hydrolyzer the distillate obtained from said first reaction-distilling column containing methyl acetate as major constituent, thus bringing said distillate into contact with water or steam in the presence of an acidic catalyst to hydrolyze the methyl acetate, (c) then continuously feeding the hydrolysis product thus obtained from the hydrolyzer to a second distilling column, withdrawing a methyl acetate-containing methanol stream from the top of said second distilling column, and recycling said stream to the lower part of the first reaction-distilling column. According to this process, it is possible to leave out the conventional complicated procedure necessary for the separation of methanol and, hence, to save the labor required therefor.