(654c) Tandem Electrocatalytic and Thermocatalytic Reactors for CO2 Conversion to BTEX Aromatics
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
CO2 Upgrading III: Alternative Approaches
Monday, November 6, 2023 - 1:06pm to 1:24pm
Sustainable CO2 conversion is a promising strategy for carbon reduction and utilization as we push to reduce the atmospheric CO2 concentration and limit global warming to 1.5 ºC. Replacing fossil fuels with CO2 as a major feedstock for the chemical supply chain allows alcohols, plastics, fertilizers, and many other products that are integral to modern society to be produced with significantly reduced environmental impacts. Electrochemical CO2 reduction (CO2R) has been widely studied as method for sustainable CO2 valorization, but real-world implementation of electrochemical CO2R is limited by low selectivities for valuable multicarbon products and low production rates of complex products including oxygenates and aromatics. However, coupling electrocatalytic CO2R with a downstream thermocatalytic reaction that is compatible with a mixture of CO2R products enables the production of complex products with high selectivities, thus overcoming the limitations of direct electrochemical CO2R. In this work, we present a tandem reactor scheme wherein CO2 is electrochemically reduced in a membrane electrode assembly (MEA) to produce ethylene (C2H4), which subsequently undergoes thermocatalytic aromatization over a gallium- and phosphorus-modified ZSM-5 catalyst (Ga/ZSM-5/P) to produce a mixture of benzene, toluene, ethylbenzene, and xylene isomers (BTEX). Several copper and copper oxide catalysts are assessed for their electrocatalytic performance in a 5 cm2 MEA by measuring polarization curves and quantifying the product distributions using gas chromatography. We show that Cu is the optimal electrocatalyst, as it exhibits the highest C2H4 selectivity and lowest absolute cell voltage of all the catalysts tested. The viability of the full tandem reactor system for CO2 conversion to aromatics is then demonstrated by directly feeding the MEA output into a thermochemical flow reactor with Ga/ZSM-5/P (2 wt% Ga, 0.8 wt% P) at 650 ºC. Finally, we present a parametric study of electrocatalyst loadings, current densities, and CO2 flow rates to optimize overall BTEX yield.