Hydrogenation of CO2 to p-xylene over ZnZrOx/hollow tubular HZSM-5 tandem catalyst

The conversion of CO2 into specific aromatics by modulating the morphology of zeolites is a promising strategy. HZSM-5 zeolite with hollow tubular morphology is reported. The morphology of zeolite was precisely controlled, and the acid sites on its outer surface were passivated by steam-assisted crystallization method, so that the zeolite exhibits higher aromatic selectivity than sheet HZSM-5 zeolite and greater p-xylene selectivity than chain HZSM-5 zeolite. The tandem catalyst was formed by combining hollow tubular HZSM-5 zeolites with ZnZrOx metal oxides. The para-selectivity of p-xylene reached 76.2% at reaction temperature of 320 degrees C, pressure of 3.0 MPa, and a flow rate of 2400 mL g(-1) h(-1) with an H-2/CO2 molar ratio of 3/1. Further research indicates that the high selectivity of p-xylene is due to the pore structure of hollow tubular HZSM-5 zeolite, which is conducive to the formation of p-xylene. Moreover, the passivation of the acid site located on the outer surface of zeolite effectively prevents the isomerization of p-xylene. The reaction mechanism of CO2 hydrogenation over the tandem catalyst was investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory. The results showed that the CO2 to p-xylene followed a methanol-mediated route over ZnZrOx/hollow tubular HZSM-5 tandem catalysts. In addition, the catalyst showed no significant deactivation in the 100 h stability test. This present study provides an effective strategy for the design of catalysts aimed at selectively preparing aromatics through CO2 hydrogenation. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.