SiO2 Deposition to Regulate Surface Barriers and Its Impact on ZSM-5 Catalyzed Reactions with Distinct Molecular Sizes

The effects of molecular size on SiO 2 deposition regulated surface barriers and zeolite catalysis are probed, taking n -pentane isomerization and benzene alkylation with ethylene as model reactions. Chemical liquid deposition of SiO 2 on the parent ZSM-5 sample only modifies its external surface slightly and passivates a small proportion of Brønsted acid sites. The apparent diffusivities increase significantly at 363–393K after SiO 2 deposition, indicating SiO 2 on ZSM-5 crystals reduces surface barriers at low temperatures. The conversion for n -pentane isomerization increases by up to 26% after SiO 2 deposition, while the conversion for benzene alkylation decreases by up to 19%. Obviously, the positive effect of SiO 2 deposition can be balanced out by the pore confinement effect at high temperatures, which is stronger for a larger molecule. This work provides a unique understanding of molecular size effects on surface barriers, which should serve to guide the design of zeolite catalysts. Graphical Abstract