(669g) A Tandem Photovoltaic-Electrochemical Photothermal Process for CO2 Conversion to Butene

Decarbonizing the chemicals industry requires net carbon negative technologies capable of displacing current greenhouse gas emitting processes. One process of significance is the decarbonized generation of valuable monomers, such as butene. Currently, butene production utilizes feedstocks which involve significant greenhouse gas emitting processes (e.g., crude oil refining) operating at high temperatures and pressures. Integrated, tandem solar fuels devices for the conversion of CO₂ to ethylene, using solar-driven CO₂ reduction (CO₂R), combined with a photothermal reactor for ethylene oligomerization, offers a potential path to producing clean butene from CO₂, using solar energy as the only driving force. A key engineering challenge for the successful operation of a tandem solar-driven electrochemical-photothermal system is the co-design of the two processes, which are typically optimized under different operating conditions. Specifically, electrochemical CO₂R (CO₂R) reactors operate under ambient temperature and pressure conditions while thermally-driven ethylene oligomerization reactors prefer elevated temperatures (80-140 °C) and pressures (30-150 atm) to promote high activity as well as pure ethylene in the inlet stream. Operation of the tandem process under solar-driven conditions imposes additional constraints on the maximum power output of the solar-driven CO₂R reactor and the maximum temperature which can be obtained in the photothermal reactor. Herein, we present the engineering of a solar-driven electrochemical reactor for unassisted operation in tandem with a photothermal ethylene oligomerization reactor to convert CO₂ to butene in a single pass. Beginning with a gas diffusion electrode flow cell, we have scaled this device to a solar-driven membrane electrode assembly to increase our ethylene generation, and subsequent conversion, by an order of magnitude.