GB921993A - Process for the production of unsaturated monocarboxylic acid esters - Google Patents

Abstract

A mixed catalyst comprising an alkaline earth phosphate and one or more compounds of a transition element of Groups I to VIII of the Periodic Table are used for the preparation of alkyl esters of aliphatic unsaturated monocarboxylic acids by the dealcoholization of alkyl esters of a - or b -alkoxy aliphatic monocarboxylic acids at an elevated temperature. The catalysts are preferably supported, e.g. on silica gel, active carbon, pumice, kaolin and silica earths and a mixture with at least 70% by weight of alkaline earth metal phosphate is preferred. Oxides or salts of the elements, copper, silver, gold, cerium, zirconium, hafnium, thorium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, uranium, iron, cobalt, nickel, or a metal of the platinum group, or complex salts such as chromates, vanadates, tungstates and molybdenates are referred to and the two components may be mixed, or alternatively an aqueous solution of the alkaline earth metal salt, other than phosphate may be mixed with the other component and the salt reacted with phosphoric acid. Small amounts of aluminium or boron compounds especially phosphates may also be included in the catalyst. Examples describe the preparation of catalysts by impregnating silica gel with an aqueous solution of phosphoric acid, magnesium chloride hexahydrate, thorium nitrate tetrahydrate and boric acid or aluminium hexahydrate, followed by drying and heating at 700 DEG C. for 48 hours, and the use of mixtures of calcium phosphate and ammonium chromate; magnesium phosphate and ferric chloride, copper and nickel oxides, and ammonium vanadate and cerium sulphate. Specification 561,153 is referred to.ALSO:Alkyl esters of aliphatic unsaturated monocarboxylic acids are prepared by dealcoholising alkyl esters of an a - or b -alkoxy aliphatic monocarboxylic acid at an elevated temperature in the presence of a mixed catalyst comprising an alkaline earth phosphate and one or more compounds of a transition element of Group I to VIII of the Periodic Table. The catalysts are preferably supported e.g. on silica gel, active carbon, pumice, kaolin, and silica earths, and the alkaline earth phosphate is preferably at least 70% by weight of the mixed catalyst. Oxides or salts of the transition elements, e.g. copper, silver, gold, cerium, zirconium, hafnium, thorium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, uranium, iron, cobalt, nickel or a metal of the platinum group, or complex salts such as chromates, vanadates, tungstates, molybdenates and uranates may be used and small amounts of aluminium or boron compounds such as phosphates may also be included. Continuous or discontinuous, gas or liquid phase reaction at between 250 and 380 DEG C. may be used. Examples describe the preparation of methyl acrylate and methacrylate. Specification 361,153 is referred to.