Investigation of MxH3-xPW12O40 (M=K, Cs)/ OMS-2/ MCM-41 nanocomposites on esterification reactions

Esterification reactions are used in synthetic organic chemistry. Sulphuric acid or tin octoate which are corrosive and virulent need to be neutralized after the completion of the reaction are used as typical catalysts for this reaction. But in case of metal containing Lewis acid catalysts, the metal needs to be removed carefully after the reaction which can be done, for instance, by adsorption on bleaching earth, which however leads to the formation of large of amounts wastes [1]. These problems can be overcome by using heterogeneous catalyst. Many heterogeneous catalysts reported in the literature for esterification reaction includes ion-exchange resin, H-ZSM-5, zeolite-Y, niobic acid, sulphated oxides and heteropoly acids. Supported heteropoly acid (HPA), which have been proved to be nearly comparable in their efficiency for a series acid catalyzed reactions to H2SO4 in liquid phase, their high solubility in the polar media, often made them difficult to separate from the reaction products, that problematic in industrial processes [2]. So the challenge was to replace them by solid acid catalysts such as zeolite or resins. But in case of zeolite, in spite of its high activity, its reaction always gives a variety of undesired by products due to higher reaction temperature [3]. Watertolerant catalysis will be introduced as new functions of Cs2.5H0.5PW12O40. Supporting and composite catalysts consist of silica or MCM-41 and H3PW12O40 or H4SiW12O40 show excellent catalytic performances. Well-dispersed heteropoly acids showed high catalytic activities in a liquid-phase alkylation of aromatics [4]. Calcination of the precipitates brought about the migration of H+ and Cs+ in the solid to form a nearly uniform solid as revealed by solid-state NMR and XRD.