Catalytic performance of a phosphorus-modified H-IM-5@meso-SiO2 composite in the alkylation of toluene with methanol

Herein, a core–shell H-IM-5@meso-SiO2 hybrid material was synthesized by reversing the charge of the external surface of IM-5 crystals to a positive charge by PDDA that could induce an oriented self-assembly formation of the meso-SiO2 shell. The as-synthesized H-IM-5@meso-SiO2 composite was thereafter modified with phosphorus species to further enhance the selectivity of the target product. The sample morphology and structure were analyzed by electron microscopy technology, XRD, XPS and N2 adsorption–desorption. The effects of the meso-SiO2 shell and phosphorus species on sample acidity were investigated by NH3-TPD, FTIR spectroscopy and solid-state NMR measurements. The catalytic properties and characterization results revealed that the meso-SiO2 shell could passivate the external surface acids of the H-IM-5 crystals. The phosphorus modification could simultaneously adjust the surface acidity as well as the size of the pores and pore-openings. The TPD analysis of xylene showed that the sample surface acidity and geometric factors played important roles in the diffusion process of the diffusing molecules.