Uniform mesoporous ZSM-5 single crystals catalyst with high resistance to coke formation for methanol deoxygenation

Abstract

In this study, an efficient procedure for controllable synthesis of uniform mesoporous ZSM-5 single crystals with various crystal architectures and high mesoporosity was developed. Compared with conventional ZSM-5 catalyst, mesoporous ZSM-5 single crystals synthesized by this method exhibited significantly higher external surface area and larger mesopore volume than conventional one. The catalytic performance of mesoporous zeolites were evaluated in the conversion of methanol to hydrocarbons using a fixed-bed reactor operating at 370 °C, atmospheric pressure and weight hourly space velocities (WHSV) of 0.16–6.58 h −1. By controlling the ZSM-5 synthesis procedure, the activity and stability of the ZSM-5 catalyst in the conversion of methanol to gasoline-range hydrocarbons can be favorably tuned. We also found that mesoporosity plays a crucial role in catalyst stability. Good correlation was observed between catalyst lifetime and mesoporosity. While the catalyst activity is related to the acid site density, the catalyst stability (deactivation rate) correlates with the measured surface ratio of BET and external surface area ( S BET/ S meso). The novel ZSM-5 catalyst exhibited improved stability due to the faster removal of products with shorter diffusion path-length and lower coke formation. The obtained results indicated that the novel mesoporous ZSM-5 catalyst containing relatively large pores (mostly mesopores) enhances reaction yield towards gasoline-range hydrocarbons. It is therefore concluded that the relatively slow deactivation rate (coke formation) of novel mesoporous ZSM-5 single crystals catalyst makes this zeolite the preferred catalyst for the conversion of methanol to gasoline-range hydrocarbons at mild conditions.