Esterification of methacrylic acid with methyl tertiary butyl ether - a process for the manufacture of methyl methacrylate

Abstract

A process for the synthesis of methyl methacrylate, based on esterification of methacrylic acid with methyl tertiary butyl ether (MTBE) with simultaneous formation of isobutene, is described. With isobutene as feedstock for methacrylic acid, it is possible to integrate the MTBE production with another important industrial reaction, the manufacture of methyl methacrylate. Esterification of methacrylic acid with methyl tertiary butyl ether (MTBE) to produce the methyl ester is highly selective using heteropoly acids of Mo or W, H 2SO 4, or p-toluene-sulfonic acid (PTS) as homogeneous catalysts. The initial step is a fast decomposition of the ether to MeOH and isobutene. The conversion of the acid to the methyl ester proceeds at a similar rate and to the same equilibrium yield as that obtained with methanol as reactant. The major byproduct is isobutene dimer, thermodynamically favored in a closed system. With heteropoly acids as catalysts, the dimer selectivity depends on the nature of the heteropoly anion. Continuous removal of isobutene eliminates the dimer formation. Our results show clearly that it is feasible to use MTBE as both the source of pure isobutene, and as esterifying agent for selective methyl ester synthesis. Based on this approach, a process for the manufacture of methyl methacrylate is proposed.