Zirconium incorporated micro/mesoporous silica solid acid catalysts for alkylation of o-xylene with styrene

The design of micro/mesoporous silica materials with solid acid catalysts for the catalytic reactions can inject new vitality into the development of nanostructures. In this paper, zirconium was successfully incorporated into micro/mesoporous silica by the direct hydrothermal synthesis, employing P123 and protic ionic liquid as the structure-directing agent. The physico-chemical properties of the micro/mesoporous silica-zirconia were characterized by means of X-ray scattering, N-2 gas sorption, scanning electron microscopy, transmission electron microscopy and NH3 desorbed TPD methods. The influence of Si/Zr ratio and different calcination temperature on the acidity and catalytic properties were discussed. Also, the catalytic activities of solid acid catalysts were evaluated by the alkylation of o-xylene with styrene. The results indicate that the heteroatom of zirconium has been successfully incorporated into the structure framework and the solid acid catalysts still possess hierarchically porous structure. The prepared catalytic materials contain moderate to strong acid sites, meanwhile, the amount of strong acid sites increases with a decrease of Si/Zr ratio. The SZ-10-SO4 (2-) (molar ratio of Si/Zr = 10) catalyst was found to be the most promising and gave the highest selectivity among all catalysts, which was due to the strong interaction between H2SO4 and micro/mesoporous materials in the presence of Zr, thus prevent H2SO4 leaching from the materials. It is worth noting that SZ-10-937 (calcined at 937 K) also has the higher yield of PXE, which maybe the enhancement of crystallization of tetragonal ZrO2 made the strong acid sites for SZ-973 sample be more than that of the other samples with the increase of calcination temperature.