Patent ID: 6353130
Filing Date: 2002-03-05
Classification: C07C

Abstract:
A process for the continuous preparation of alkyl esters of (meth)acrylic acid by reacting (meth)acrylic acid with alkanols of 1 to 8 carbon atoms in a solvent-free phase at elevated temperatures and in the presence of an acidic esterification catalyst, in which the (meth)acrylic acid, the alkanol and the acid catalyst are fed to a reaction zone, the resulting water as part of a mixture comprising starting alkanol is removed from the reaction mixture by rectification, during the residence time in the reaction zone, in a rectification unit I mounted on the reaction zone, the distillate obtained is separated into an organic phase containing starting alkanol and into a water-containing aqueous phase, the organic phase is recycled to the rectification unit I, the reaction mixture containing the desired ester is passed from the reaction zone into a separation zone comprising further rectification units and the resulting alkyl ester of (meth)acrylic acid is isolated in said separation zone, whereinthe (meth)acrylic acid used is an acetic acid-containing crude (meth)acrylic acid, the acidic esterification catalyst is separated from the reaction mixture containing the desired ester before said reaction mixture is passed on into the separation zone comprising further rectification units, the residual reaction mixture I is fed to a rectification unit II and is separated therein by rectification into a low-boiler product containing desired ester and components boiling at a lower temperature than the desired ester and into a residual reaction mixture II comprising the desired ester and components boiling at a higher temperature than the desired ester, at least the organic fraction of the low-boiler product not used as reflux to the rectification unit II is recycled from the rectification unit II into the reaction zone, the residual reaction mixture II is fed to a rectification unit III and the desired ester is separated therein from the components boiling at a higher temperature than the desired ester, the separation efficiency chosen in the rectification unit I is such that the distillate separated off by rectification and comprising water and starting alkanol also contains a portion of the alkyl acetate formed in the reaction zone as a byproduct and only a portion of the organic phase separated from the distillate obtained in the rectification unit I is recycled to the rectification unit I and the remaining amount is separated off as an alkyl acetate purge.