Synthesizing high-volume chemicals from CO2 without direct H2 input

Abstract

Decarbonizing the chemical industry will eventually entail using CO2 as a feedstock for chemical synthesis. However, many chemical syntheses involve CO2 reduction using inputs such as renewable hydrogen. In this review, we discuss chemical processes that use CO2 as an oxidant for upgrading hydrocarbon feedstocks. The captured CO2 is inherently reduced by the hydrocarbon co-reactants without consuming molecular hydrogen or renewable electricity. This CO2 utilization approach can be potentially applied to synthesize 8 emission-intensive molecules, including olefins and epoxides. We discuss catalytic systems and reactor concepts that can overcome practical challenges, e.g. thermodynamic limitations, over-oxidation, coking and heat management. Under the best-case scenario, these hydrogen-free CO2 reduction processes have a combined CO2 abatement potential of ca. 1 gigatons per year and avoid the consumption of 1.24 PWh renewable electricity, based on current market demand and supply.