Tunable acidity and porosity for optimizing liquid-phase catalytic efficiency utilizing hierarchical zeolite ZSM-5 single crystal reactor

Abstract

Hierarchically porous zeolites, combining the intrinsic microporous catalytic properties and the enhanced meso-/macroporous access and transport, exhibit excellent performances in many highly efficient catalytic processes. The acidity and porosity are two key factors affecting the catalytic conversion, selectivity and lifetime. It is necessary to construct such hierarchically porous zeolite catalysts with adjustable acid active sites and pore properties in a wide range to meet the specific catalytic requirements. Herein, an ordered interconnected hierarchical ZSM-5 single crystal catalyst composed by zeolite sphere units stacking in face-centered cubic (FCC) arrangement has been used as the theoretical model to research the corresponding material properties on the enhancement of specific catalytic process. Specifically, the properties of acid sites and meso-/macropores can be accurately adjusted by facilely changing the SiO₂/Al₂O₃ molar ratio (100–1000) and the sphere unit size (180–580 nm), respectively. As a result, the benzyl alcohol liquid-phase catalytic ability markedly improved thanks to the optimized acidity and meso-/macropore size. The larger meso-/macropore size shows higher benzyl alcohol conversion, while the higher SiO₂/Al₂O₃ molar ratio exhibits higher alkylation product selectivity. This work illustrate that the targeted catalytic process can be effectively enhanced by adjusting the acidity and porosity within such ordered hierarchical ZSM-5 single crystal system.