Process for producing diol

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 an upper part thereof a liquid acetic ester of a butanediol or butenediol, while continuously feeding methanol to the said column from a place higher than the bottom but lower than the middle part thereof, to bring both feeds into counter current gas-liquid contact in the presence of an acidic or basic catalyst, thereby allowing both feeds to react, withdrawing from the bottom a bottom stream containing a diol as major constituent, (b) continuously feeding to a hydrolyzer the distillate which is obtained from said first reaction-distilling column and which contains methyl acetate as major constituent, thus bringing said distillate into contact with water or steam in the presence of an acidic catalyst to effect hydrolysis, (c) then continuously feeding the reaction mixture from the hydrolyzer to a second distilling column, withdrawing a methyl acetate-containing methanol stream from the top of the second distilling column, and recycling said stream to a place higher than the bottom but lower than the middle part of the first reaction-distilling column, wherein the amount of methanol fed to a place higher than the bottom but lower than the middle part of the first reaction-distilling column is 1.0 to 5 moles per mole of the ester group of the acetic ester of diol.