The effect of flue gas contaminants on electrochemical reduction of CO2 to methyl formate in a dual methanol/water electrolysis system

Comparative Technoeconomic Analysis of Pathways for Electrochemical Reduction of CO2 with Methanol to Produce Methyl Formate

“…This low parasitic ORR faradaic efficiency assumes the device can effectively manage dilute oxygen, but it is a reasonable value considering the low solubility of oxygen in methanol and that previous flue gas electrolysis on a Pb cathode in a methanol/ water system showed improved performance with dilute O 2 present. 31 It was assumed that the pressure swing adsorption gas separation unit could still effectively separate 97% of the CO 2 in the electrolyzer gas output stream, although the presence of flue gas N 2 and O 2 does increase the size of the required PSA equipment. System 2 base case parameters are summarized in Table S7.…”

“…Considering that flue gas contains dilute CO 2 with a concentration around ∼15%, which presents mass transport issues relative to pure CO 2 , achieving sufficiently high current density to realize the direct flue gas conversion cost savings may be very challenging. 31 Some key performance metrics that differentiate the economic advantages and disadvantages between System 1 and 2 dual methanol/water electrolysis and System 3 methanol/methanol electrolysis are highlighted in Figure 9B−D. As the cathode methyl formate FE decreases, each system became increasingly more expensive due to increased capital, electricity, and distillation costs.…”

“…31 Also, for System 2 utilizing direct electroreduction of flue gas, experimental data for a Pbcatalyzed CO 2 conversion in methanol to methyl formate showed consistent or even improved electrolysis performance in the presence of 4% O 2 , which was attributed to beneficial catalytic effects of maintaining the cathode surface oxide. 31 Thus, in modeling System 2, a comparable base case electrolysis performance was assumed without the need for separation or mitigation of the oxygen component of the flue gas.…”

“…26 In System 2, the power plant flue gas is directly utilized in the dual CH 3 OH/H 2 O electrolyzer without CO 2 capture, bypassing the capital expense and energy required for CO 2 purification. 31 System 3 uses capture technology to provide purified CO 2 to an all methanol solvent-based electrolyzer. This approach produces methyl formate at the cathode through electrochemical CO 2 R (eq 1) while also synthesizing methyl formate through a different half-reaction at the anode through the oxidation of methanol.…”

“…This dual CH 3 OH/H 2 O electrolysis has been demonstrated with a methyl formate faradaic efficiency (FE) as high as 75% using a Pb cathode and low pH (<2.5) catholyte to promote the esterification of formic acid and methanol . In System 2, the power plant flue gas is directly utilized in the dual CH 3 OH/H 2 O electrolyzer without CO 2 capture, bypassing the capital expense and energy required for CO 2 purification . System 3 uses capture technology to provide purified CO 2 to an all methanol solvent-based electrolyzer.…”