Alkylation of benzene using CO2 and H2 over ZnZrOx/ZSM-5: the effect of Y doping

The increase in the CO2 concentration in the atmosphere has caused a serious global climate problem. Aromatics are important intermediates in chemical production, and by utilizing CO2 in aromatic synthesis not only the effective utilization of CO2 can be realized, but also carbon emission reduction can be effectively achieved. Herein, a bifunctional catalyst prepared by physically mixing Y-doped ZnZrOx metal oxide with the zeolite ZSM-5 was applied to the synthesis of toluene and xylene by the alkylation of benzene using CO2 and H2. The bifunctional catalyst Y0.1/ZSM-5 showed the best reaction performance. 17.3% conversion of CO2, 30.8% conversion of benzene, and 71.6% selectivity of toluene and xylene were achieved. And 96.8% of the liquid-phase products were toluene and xylene. Based on the CO2-TPD, H2–D2 exchange, H2-TPR, EPR, XPS, and in situ DRIFTS results, a small amount of Y doping can effectively increase more oxygen vacancies on the surface of ZnZrOx to promote CO2 adsorption and activation. The activation of hydrogen was enhanced resulting from Y–Zn interactions. In the reaction pathway, Y doping accelerated the conversion of CO2 to HCOO* species to promote the reaction process, allowing more methanol to participate in the benzene alkylation reaction and further improving the CO2 and benzene conversion.