Chemical Absorption of CO₂ Enhanced by Solutions of Alkali Hydroxides and Alkoxides at Room Temperature

Abstract

This article presents the study of CO2 capture through aqueous solutions with high basicity conditions. Systematic experiments were conducted to assess the performance of alcohols mixed with aqueous alkaline hydroxides for carbon dioxide capture. Alcohols can work as a catalyst in the capture of CO2 providing greater basicity, a lower surface tension, and an amphiphilic character in the polar aqueous solvent/ (nonpolar CO2 and N2) gas mixture interface, and a lower temperature of solvent regeneration. The results showed that short‐chain alcohols, such as methanol and ethanol, and alkaline metals of greater molar mass (i. e., K compared to Na) can produce greater basicity and a higher CO2 absorption rate in the mixtures than conventional aqueous solutions such as ammonia or monoethanolamine in the same concentration. DFT calculations of electronic and thermodynamic properties for CO2 absorption reactions were carried out to analyze the nucleophilic trend of the short‐chain alkoxides studied. The volumetric proportion between water and alcohol, as well as the concentration of alkaline hydroxide, influences the rate of CO2 absorption, the temperature of regeneration and volatility of the solvent, and the formation of precipitates. CO2 absorption rates greater than 90 % v/v and solvent regeneration temperatures of approximately 78 °C were achieved using ethanol, water, and KOH.

CO2 capture and utilization by biocatalytic synthesis of carboxylic acids: a process design study

“…Moreover, the significant energy penalty affecting the costs of CO2 capture (Ember Climate Change, 2022) is driving researchers to search for less energy-intensive, more economical capture paths as one key to CCU/S feasibility. Post-combustion CO2 capture by cyclic absorption/desorption is accomplished by absorption of CO2 in alkaline solvents (Liu et al, 2020, De Carvalho et al, 2022, Borhani et al, 2015, followed by recovery of concentrated CO2 using a thermal stripping column (Knuutila et al, 2009). This process is most typically carried out with amine-based solvents, but recently also carbonate/bicarbonate solutions with enzymatic promoters have been successfully proposed.…”