Journal of Molecular Catalysis A-Chemical, Vol.391, 55-65, 2014
Transesterification of diethyl malonate with benzyl alcohol catalyzed by modified zirconia: Kinetic study
Zirconia and its modified forms such as 10%Mo(VI)/ZrO2, 10%V(V)/ZrO2, 10%W(VI)/ZrO2 and SO42-/ZrO2 were prepared and characterized for their physico-chemical properties such as BET for surface area, NH3-TPD and n-butylamine back titration method for total surface acidity, PXRD technique for crystallinity and ICP-OES technique for elemental analysis. These materials were used as catalysts in liquid phase transesterification reaction of diethyl malonate (DEM) with benzyl alcohol (BA). Optimization of reaction conditions such as reaction time, reaction temperature, weight of the catalyst and molar ratio of reactants were carried out to obtain highest possible transester yield. Dibenzyl malonate (DBM) and benzyl ethyl malonate (BEM) were obtained as major products. Highest total transester yield of (88%) was obtained in the presence of 0.75 g of SZ catalyst at a molar ratio of DEM:BA = 1:3, reaction temperature of 393 K and reaction time 5 h. Kinetic studies were carried out to find out the rate of the reaction and energy of activation values for zirconia catalysts, in order to identify a facile catalyst system for this reaction. A possible reaction mechanism was proposed based on the kinetic data and it was observed that Eley-Rideal mechanism fits well for this reaction. Reactivation and reusability studies of the catalysts were also taken up. (C) 2014 Elsevier B.V. All rights reserved.
Keywords:Modified zirconia;Transesterification;Dibenzyl malonate;Benzyl ethyl malonate;Kinetics and mechanism