Indium-promoted znZrOx/nano-ZSM-5 for efficient conversion of CO2 to aromatics with high selectivity

Abstract

The hydrogenation of CO2 to produce liquid hydrocarbons is an effective method for its resource utilization. However, due to the chemical inertness and multipath conversion of CO2, it is still a great challenge to efficiently convert CO2 to high value-added aromatic hydrocarbons. In this work, InZnZrOx and In-ZnZrOx samples with the same In2O3 content (10 wt%) were prepared by the co-precipitation and the incipient wet impregnation method, respectively. Nano-ZSM-5 zeolite was synthesized by a seed-induced template-free method. The bifunctional catalysts prepared by physically mixing InZnZrOx and nano-ZSM-5 zeolite can achieve aromatics selectivity of 90.6% (the proportion of tetramethylbenzene is 69.5%) among all hydrocarbons at a CO2 single-pass conversion of 13.8% under optimized reaction conditions of 3.0 MPa, 4000 mL·gcat.−1·h−1, H2/CO2 volume ratio of 3 and 320 °C. The selectivities to CO and CH4 are only 19.8% and 0.19%, respectively. Experimental results indicated that the formation of abundant oxygen vacancies and basic sites, achieving electron transfer from In and Zn ions to Zr ion, and improving mass transfer of nano-ZSM-5 zeolite results in the highest activity and aromatic selectivity over the InZnZrOx/nano-ZSM-5 bifunctional catalyst. This work provided a highly efficient way for direct CO2 hydrogenation to tetramethylbenzene.