Characterization and catalytic activity of silylated nanoscale ZSM-5

Multiple impregnations and chemical reaction deposition were used to modify the external surface of nanoscale ZSM-5 with tetraethoxysilane. Toluene disproportionation over this sitylated ZSM-5 was investigated. The acid sites of the catalysts were measured by modified Hammett indicators and FT-IR spectroscopy of adsorbed pyridine. The catalyst structure was characterized by X-ray diffraction and Si-29 MAS NMR. The results showed that silanization of the zeolite decreased the concentration of acid sites, which led to the decrease in catalytic activity. The silanization also decreased the amount of Q(4) species of SI and the relative crystallinity of the zeolite. Dealumination was observed on the surface of nanoscale ZSM-5. The decrease in the number of framework aluminum resulted in a decline in the number of acid sites and catalytic activity.