Study on modification of nanocrystalline ZSM-5 zeolite and process conditions of MTG reaction

Abstract

The methanol to gasoline (MTG) process plays the key role in producing liquid fuels without reliance on petroleum in the technical route from biomass-derived syngas to gasoline via methanol. Here, the nanocrystalline ZSM-5 and Fe-, Zn- and Ga-modified nanocrystalline ZSM-5 zeolites were synthesized by hydrothermal synthesis method. The prepared zeolites were characterized by XRD, SEM, N2 physical adsorption and NH3-TPD techniques, and their properties were studied. Moreover, the influence of different metals on catalytic performance of synthesized catalysts in MTG reaction was investigated. Furthermore, the effects of temperature and weight hourly space velocity (WHSV) on MTG reaction were evaluated. The results demonstrated that new acid sites were generated in ZSM-5 zeolite due to the introduction of Fe, Zn and Ga, and acid amounts of zeolites increased. The nanocrystalline FeZSM-5 possessed the most amount of weak and strong acid sites, which exhibited the outstanding catalytic performance in MTG reaction. When FeZSM-5 catalyzed MTG reaction, as the reaction temperature and WHSV increased, the gasoline yield showed the trend of first increase and then decrease. And the isoparaffins content in gasoline decreased, while the aromatics increased. The suitable reaction temperature and WHSV for MTG reaction were 370-390°C and 2-4 h⁻¹, respectively. Under the reaction conditions of 0.1 MPa, 390°C and a WHSV of 4 h⁻¹, the methanol conversion was 100% and the gasoline yield reached as high as 32.9%, and the isoparaffins and aromatics content in gasoline were 36.8% and 39.8% respectively.