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

Abstract

Electrochemical CO2 reduction has promise as a technology that could help society reach carbon neutrality while producing valuable fuels and chemicals. Herein, the electrochemical synthesis of methyl formate, a product not observed in aqueous CO2 electrolysis, has been analyzed by a rigorous technoeconomic model to evaluate its commercial viability. Methyl formate synthesis has been demonstrated with high faradaic efficiency through the electroreduction of CO2 in methanol. Four competing approaches were analyzed: (1) electroreduction of captured CO2 in a dual CH3OH/H2O electrolyzer, (2) direct electroreduction of flue gas CO2 in a dual CH3OH/H2O electrolyzer, (3) electroreduction of captured CO2 in a CH3OH/CH3OH electrolyzer, and (4) electroreduction of captured CO2 in a H2O/H2O electrolyzer with a downstream CH3OH reactor. Sensitivity analyses, cost contour plots, and comparison plots were generated. The dual methanol/water electrolysis approach was the most cost competitive, with a levelized cost of methyl formate below the present market price. The all-methanol electrolysis route was more expensive due to increased methanol consumption and greater distillation costs. Methyl formate production through aqueous CO2 electrolysis to formic acid with a secondary esterification reaction was by far the most expensive approach, primarily due to the energy-intensive nature of distilling formic acid from water.

Prolonged Stability of Pb-Catalyzed CO2 Electroreduction to Methyl Formate in Acidic Methanol

“…A dual-electrolyte approach with a methanol catholyte and an aqueous anolyte separated by a Nafion membrane was implemented to improve the practicality of the system by promoting the sustainable water oxidation half-reaction rather than the sacrificial anodic oxidation of methanol solvent. , Sulfuric acid was employed as the supporting electrolyte in the anolyte to ensure migration of protons across the membrane during electrolysis to enable a stable bulk catholyte pH <2 (Figure ). With 5 mM H 2 SO 4 anolyte, the catholyte pH remained stable over prolonged electrolysis at 0.95–2, corresponding to ∼3 mM H + after accounting for variability in the catholyte water content (Tables S1–S2).…”

“…Methyl formate is a highly volatile (boiling point, BP = 32 °C) liquid product, so it is more easily separated from the postelectrolysis solvent than more common formyl products like formate and formic acid (BP = 101 °C). A recent technoeconomic analysis using distillation for liquid product separation found that methyl formate electro-synthesized from CO 2 in methanol could be significantly cheaper to produce than a competing route via CO 2 R to formic acid in water and subsequent nonelectrochemical conversion with methanol, largely due to the energy-intensive nature of purifying the formic acid intermediate …”

Improvement in Ammonia, Hydrogen, and Methyl Formate Synthesis Process by Employing Multiobjective Optimization of a Novel Multifunctional Membrane Reactor

“…16 To produce MF, various methods have been proposed, including dehydrogenation of methanol, 17 dimerization of formaldehyde, 18 carbonylation of methanol, 19 and electroreduction of CO 2 in methanol. 20 Methanol dehydrogenation produces hydrogen as a byproduct, which is an energy source, and is also more environmentally and economically efficient than the other methods. 17 Several studies have indicated that copper-based catalysts are the most effective agents for dehydrogenating methanol.…”

“…Solvents, antiseptics, and gasoline additives are also valuable applications of this material . To produce MF, various methods have been proposed, including dehydrogenation of methanol, dimerization of formaldehyde, carbonylation of methanol, and electroreduction of CO 2 in methanol . Methanol dehydrogenation produces hydrogen as a byproduct, which is an energy source, and is also more environmentally and economically efficient than the other methods .…”

Practical Assessment for At-Scale Electrochemical Conversion of Methane to Methanol

“…Though numerous techno-economic studies have been reported for other processes, such as electrocatalytic ammonia synthesis − and CO 2 reduction, − only one has been considered for methane oxidation to fuels . Though there are elements of the ammonia and CO 2 studies that could be extrapolated to methane oxidation, looking at it through the lens of their specific technology limits their effectiveness and presents a need for a specific analysis.…”