Synthesis of glycerol carbonate over porous La-Zr based catalysts: The role of strong and super basic sites

As important glycerol derivatives, glycerol carbonate (GC) and glycidol (GD) have attracted increasing attention in recent years. In the present work, a series of new solid base catalysts were developed to catalyze the conversion of glycerol to afford GC and GD. These catalysts were prepared by loading KF on the porous La-Zr solid base catalyst and characterized using a series of methods. A large number of various basic sites were generated upon loading KF onto the La-Zr-600 support. The weak basic sites were assigned to the surface hydroxyl groups produced during the formation of LaOF, while the strong and super basic sites were related to the Lewis base produced due to the interaction between KF and the La-Zr-600 support. A glycerol conversion of 91.77% and a GC selectivity of 99% were obtained over 0.3KF/La-Zr, which displayed the best catalytic performance under the optimal reaction conditions. The excellent activity of these catalysts was attributed to the presence of the strong and super basic sites, which favor the transesterification of glycerol with dimethyl carbonate. The production of GD from GC decarbonylation was unfeasible at low temperature using the newly developed catalysts. A plausible reaction mechanism has been proposed based on the experimental results and characterization.