Passivated Surface of High Aluminum Containing ZSM-5 by Silicalite-1: Synthesis and Application in Dehydration Reaction

Methanol dehydration reaction is an essential process to bridge the biomass conversion and chemicals. However, the undesired distribution of zeolite acidity hinders its excellent catalytic performance. In this work, the technique of passivating surface acidity of a high aluminum containing ZSM-5 zeolite by the growth of the silicalite-1 layer under hydrothermal conditions is presented. The samples passivated with a single-step or double-step silicalite-1 deposition were tested for the dehydration of methanol to dimethyl ether and compared to the parent ZSM-5 zeolite using a bench-scale packed bed reactor operated at 160-240 °C under atmospheric pressure. The formation of an amorphous silica layer determines the decrease of the accessible micropore surface determining the drop in conversion and selectivity of the catalyst with the passivating single-step silicalite-1 deposition with respect to the parent zeolite. In contrast, the catalyst with a double-step silicalite-1 deposition showed a conversion close to the parent ZSM-5 zeolite one but with an improved selectivity at high temperature, due to the low coke formation and retention in the highly porous structure. © 2022 American Chemical Society.