Economically viable CO2 electroreduction embedded within ethylene oxide manufacturing

Abstract

Electrochemical conversion of CO₂ (CO2R) into fuels and chemicals can both reduce CO₂ emissions and allow for clean manufacturing in the scenario of significant expansion of renewable power generation. However, large-scale process deployment is currently limited by unfavourable process economics resulting from significant up- and down-stream costs for obtaining pure CO₂, separation of reaction products and increased logistical effort. We have discovered a method for economically viable recycling of waste CO₂ that addresses these challenges. Our approach is based on integration of a CO2R unit into an existing manufacturing process: ethylene oxide (EO) production, which emits CO₂ as a by-product. The standard EO process separates waste CO₂ from the gas stream, hence the substrate for electroreduction is available at an EO plant at no additional cost. CO₂ can be converted into an ethylene-rich stream and recycled on-site back to the EO reactor, which uses ethylene as a raw material, and also the anode product (oxygen) can be simultaneously valorized for the EO production reaction. If powered by a renewable electricity source, the process will significantly (ca. 80%) reduce the CO₂ emissions of an EO manufacturing plant. A sensitivity analysis shows that the recycling approach can be economically viable in the short term and that its payback time could be as low as 1–2 years in the regions with higher carbon taxes and/or with access to low-cost electricity sources.