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%.