Two-Stage Catalytic Conversion of Carbon Dioxide Into Aromatics Via Methane.

In the refinery of the future, the input shifts from crude oil to biomass, plastic, and CO2. Therefore, we need to find alternative routes to produce chemical building blocks, such as aromatics, which are used in products like, for example, fuels. In this study, we investigated a two-stage route to produce benzene from CO2. In two sequential reactions, CO2 is first converted into methane over a Ni/TiO2 catalyst, and methane is further reacted to yield benzene using a Mo/ZSM-5 catalyst via the methane dehydroaromatization (MDA) reaction. Through a combination of thermodynamic calculations and experiments, we found the goldilocks conditions for performing this two-stage process. The unreacted CO2 and H2 from the first reaction extended the benzene production in the second reaction. Using a reaction mixture of CO2, H2, and CH4 resulted in benzene production of at least 72 h, by suppressing carbon growth on the catalyst surface. However, the concentration range in which CO2 and H2 can be added to the feed without losing benzene production is narrow, as we show with H2 fluctuation experiments. We demonstrate that the combination of CO2 methanation and MDA allows us to catalytically convert CO2 into benzene with an overall yield of 5%.