GB719908A - Improvements relating to the preparation of methacrylic acid and esters thereof - Google Patents

Abstract

In the preparation of methacrylic acid or its esters with alcohols containing 3 or more carbon atoms the reaction mixture obtained in the conversion of acetone cyanohydrin to methacrylamide and the hydrolysis of the latter compound to the acid is treated with a liquid extraction agent so that the acid is extracted directly from the reaction mixture and, if desired, esterified with the appropriate alcohol. Specified extraction agents are alcohols containing 3 or more carbon atoms per molecule which may be the same as those used for esterification; aromatic or aliphatic hydrocarbons and chlorinated hydrocarbons. The extracted acid may be esterified by conventional means, e.g. by the addition of an alcohol to the extract neutralized to pH about 0.8 with subsequent removal of water by distillation or azeotropic distillation in the presence of esterification catalysts such as p-toluene sulphonic acid. In examples, acetone cyanohydrin is treated with sulphuric acid in the presence of sulphur, tannin and hydroquinone and (1) extracted with butanol, the extract neutralized to pH 0.8 and butyl methacrylate made by the above azeotropic method in the presence of p-toluene sulphonic acid and hydroquinone; (2) extracted with toluene and butyl methacrylate made as in (1); (3) extracted with toluene and methacrylic acid removed by distillation in the presence of hydroquinone and pulverized copper; and (4) extracted with toluene and lauryl methacrylate made by the method of (1).