The electrochemical reduction of carbon dioxide (CO 2 RR) to chemical feedstocks, such as ethylene (C 2 H 4 ), is an attractive means to mitigate emissions and store intermittent renewable electricity. Much research has focused on improving CO 2 electrolysis cell efficiency; less attention has been paid to the downstream purification of outlet product streams. In this work, we model the use of mature downstream separation technologies as part of the overall production of polymer-grade C 2 H 4 from CO 2 . We find that CO 2 removal is the most energy-intensive downstream separation step. We identify opportunities to reduce separation energies to ∼22 GJ/tonne C 2 H 4 through necessary improvements in C 2 H 4 selectivity (>57%), cathodic CO 2 conversion (>80%), and CO 2 crossover (0 mol CO 2 /mol e − ). This work highlights the influence of cell performance parameters on downstream separation costs and motivates the development of new, efficient separation processes better suited to the distinctive outlet streams of CO 2 electrolyzers.

Carbon dioxide (CO 2 ) electrolysis powered with renewable electricity can help close the carbon cycle by converting emissions into chemicals and fuels. Two key advancements are required to bridge the technological gaps for industrial implementation: pilot plant demonstrations with detailed performance data; and chemical engineering process models built and tested with lab-and pilot-scale data. Here, we develop a semi-empirical electrolyzer model in Aspen Custom Modeler which is trained on a 5 cm 2 lab-scale CO 2 electrolyzer. We then scale to a pilot-scale 800 cm 2 single cell and 10 × 800 cm 2 stack and use the results to validate the model; at 100 mA cm −2 , the model can predict six of seven cell performance metrics within 16% absolute error and three of five stack metrics within 11% absolute error. With the combination of the electrolyzer model and the pilot-scale data, this work provides the prerequisites for further scaling of CO 2 electrolysis.

The electrochemical reduction of carbon dioxide (CO2RR) to chemical feedstocks, such as ethylene (C2H4), is an attractive means to mitigate emissions and store intermittent renewable electricity. Much research has focused on improving CO2 electrolysis cell efficiency; less attention has been paid to the downstream purification of outlet product streams. In this presentation, we model the use of mature downstream separation technologies as part of the overall production of polymer-grade C2H4 from CO2. We find that CO2 removal is the most energy-intensive downstream separation step. We identify opportunities to reduce separation energies ten-fold to ∼22 GJ/tonne C2H4 through necessary improvements in C2H4 selectivity (>57%), cathodic CO2 conversion (>80%), and CO2 crossover (0 mol CO2/mol e−). This work highlights the influence of cell performance parameters on downstream separation costs and motivates the development of new, efficient separation processes better suited to the distinctive outlet streams of CO2 electrolyzers.