Support influence on the basicity promotion of lithium-based mixed oxides for transesterification reaction

Solid catalysts comprising Li-based oxides were prepared by LiNO3 impregnation onto supports with different acid/base properties (SiO2, MgO, Al2O3 and Mg(Al)O mixed oxide obtained from hydrotalcite). The materials were characterized by means of XRD, N-2 physisorption, ICP-OES, FEG-SEM and TPD of CO2. The oxide reactivities were evaluated using the model transesterification reaction between methyl acetate and ethanol under mild reaction conditions (313 K, ethanol/methyl acetate molar ratio = 6/1 and 0.2 wt.% of catalyst). Lithium impregnation onto silica and gamma-alumina yielded inactive catalysts for transesterification. On the other hand, the lithium addition onto MgO produced an active catalyst and remarkably high conversions were obtained for Li/Mg(Al)O. The different supports used considerably affected the base site densities and base strengths of the Li-based catalysts. The base properties thus influenced the catalytic performance of the materials. Stability tests revealed the lithium leaching occurrence which resulted in some homogeneous contribution. (C) 2012 Elsevier Ltd. All rights reserved.