Esterification of maleic anhydride with methanol over solid acid catalysts:a novel route for the production of heteroesters

摘要

Al-MCM-41 molecular sieves (Si/Al=50,100,and 150) were synthesized hydro-thermally and characterized by XRD,FTIR,BET (surface area) and Si,Al MAS-NMR techniques.The catalytic activities of these molecular sieves and of Hp-zeolite were tested for esterification of maleic anhydride in the liquid phase at 80,100 and 150degC.The reaction was observed to yield monomethylmaleate even in the absence of catalyst,as the product is strain-free,whereas the formation of dimethylmaleate required the presence of a catalyst.Among the catalysts,Hp was found to be more active than Al-MCM-41 molecular sieves.The lower activity of Al-MCM-41 catalyst was due to pore blocking by reactants as well as by products.An interesting observation in this study is that dimethylmaleate isomerisation to dimethylfumarate is not favored.At 80degC this isomerisation was completely absent over Al-MCM-41 molecular sieves,and was less than 1 % over Hp.The complete conversion of maleic anhydride with methanol to monomethylmaleate stands as a discovery that will help to design new routes to synthesize a wide variety of new heteroesters.