Study on the 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 the 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 the catalytic performance of the synthesized catalysts in the MTG reaction was investigated. Furthermore, the effects of temperature and weight hourly space velocity (WHSV) on the MTG reaction were evaluated. The results demonstrated that new acid sites were generated in ZSM-5 zeolite upon the introduction of Fe, Zn, and Ga, and that the amount of acid in the zeolites increased. The nanocrystalline FeZSM-5 possessed the highest number of weak and strong acid sites, exhibiting outstanding catalytic performance in the MTG reaction. When FeZSM-5 catalyzed the MTG reaction, as the reaction temperature and WHSV increased, the gasoline yield initially increased, then decreased. In addition, the isoparaffin content in gasoline decreased, while the aromatic content increased. The suitable reaction temperature and WHSV for the 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%. The gasoline yield reached 32.9%, and the isoparaffin and aromatic content in gasoline were 36.8% and 39.8%, respectively.