Facile Synthesis Of Metal-Functioned Mesoporous Materials And Their Liquid-Phase Catalytic Properties

Mesoporous SiO2materials are subject to extensive research in heterogeneous catalysis because of their high surface areas, large pore volumes and tunable pore diameters. However, these mesoporous materials show poor catalytic performances owing to their amorphous framework, electrical neutrality, no defects and acid sites on the surface. The amorphous framework results in easy modification of mesoporous SiO2compared with zeolite. The catalytic performance of these mesoporous materials can be enhanced by metal modification owing to new active sites introduced. Catalysts with different supports and active species can be prepared by choosing different precursors and synthesis routes. Combining the correlation between catalytic performance and the properties of active species, supports and their interrelations, the design and preparation of a highly effective catalyst can be achieved.MSU-X is a new type of mesoporous SiO2material with three dimensional (3D)"worm-like" pore and shorter channel. Compared with SBA-15and MCM-41(2D pore structure), MSU-X shows better diffusion performance of the reaction substrate and product owing to the3D structure. Moreover, MSU-X is usually synthesized under neutral conditions. The electrostatic interaction and hydrogen bond between the template and materials surface is weak, which results in the template can be easily removed by ethanol extraction. Thus the templates can be reused and the synthetic cost can be reduced. Similarly, mesoporous material SBA-16with3D ordered structure can be used as an excellent catalytic support. Herein, Fe/Cr-MSU-X catalysts with hierarchical mesopores were successfully prepared by neutral-template route with TEOS as silica source and plouric F127as template. Fe/Cr-MSU-X catalysts showed high catalytic activity and selectivity for liquid phase oxidation of phenol with hydrogen peroxide as oxidant agent.A series of Fe/Cr-SBA-16with different Fe/Cr content were synthesized by adjusting the pH value of synthesis system, respectively. Fe/Cr species types can be affected by the pH value in the synthesis system. These Fe/Cr-SBA-16showed high surface area and uniform pore size distributions. And Fe/Cr-SBA-16showed high catalytic activity and selectivity in catalytic applications.Sn-MSU-X with high ordered structure was synthesized under neutral condition. Sn-MSU-X possessed high surface area and large volume. The pore sizes were uniform and Sn-MSU-X was rich in microporous structure. The pyridine FTIR revealed that there were both Bronsted and Lewis acidic sites on the surface, in which, Lewis acid was the dominant one.