Effect of hydrophobic and hydrophilic properties of solid acid catalysts on the esterification of maleic anhydride with ethanol

Esterification of maleic anhydride with ethanol over Al-MCM-41 (Si/Al = 50,100 and 150) and Hβ zeolite was investigated in the liquid phase at 80, 100 and 120 °C. Monoesterification of maleic anhydride to monoethyl maleate (MEM) was found to be fast and independent of the presence of catalyst but subsequent esterification to diethyl maleate (DEM) was catalyst dependent. The absence of isomerisation of diethyl maleate to diethyl fumarate (DEF) over Al-MCM-41 molecular sieves is a significant advantage. Al-MCM-41 (50), Al-MCM-41 (100) and Hβ are convenient replacement for hazardous sulphuric acid used in the industrial esterification of maleic anhydride with ethanol.