KF Promoted Mesoporous γ-Al_2O_3 with Strong Basicity: Preparation, Characterization and Catalytic Activitiy for Transesterification to Biodiesel

摘要

The present paper describes the preparation of KF/M-γ-Al_2O_3, efficient mesoporous solid bases. The procedure involves loading KF into a crystalline mesoporous γ-Al_2O_3 that was synthesized by the self-assembly of poly-4-vinylpyridine (P4VP) with Al~(3+) species. The synthesis is based on the strong acid-base interaction, hydrothermal treatment at 180°C and calcination at 550°C. Characterizations using XRD analysis and low temperature N_2 adsorption indicated that different amounts of KF could be introduced into crystalline mesoporous γ-Al_2O_3 to obtain catalysts with high BET surface areas, large pore volumes and uniform pore size distribution. Based on SEM images, KF/M-γ-Al_2O_3 catalysts have rough surface character and a large nanopore volume. CO2-TPD curves registered for KF/M-γ-Al_2O_3 contain high temperature peaks, indicating strong basicity of the catalysts. Under the same reaction conditions KF/M-γ-Al_2O_3 catalysts exhibit much better activities for transesterification to biodiesel than KOH, NaOH, H2_SO_4, hydrotalcite and CaO. Enhanced activities appear to arise from strong basisity and large BET surface areas.