Membrane contactor-photocatalytic hybrid system for carbon dioxide capture and conversion to formic acid

Abstract

The escalating demand for Carbon Capture and Utilization (CCU) schemes to mitigate CO2 emissions has propelled research into more efficient methods of CO2 conversion, such as the production of formic acid. While traditional approaches often require harsh operating conditions and substantial energy inputs, photocatalysis offers a promising alternative by harnessing CO2, water, and light for formic acid production. This study evaluates the performance and reaction kinetics of CO2 capture and conversion to formic acid using an integrated membrane contactor and photocatalytic process. Investigation into various CO2 absorbents and reduction catalysts reveals that TEA achieves a CO2 loading of 0.957 mol of CO2/mole of solvent, while NaOH achieves 0.75 mol of CO2/mole of solvent over a 4-h operation period. Subsequent photoreduction of CO2 results in formic acid concentration of 345.44 μmol/(L.gcat) using ZnO and 220.87 μmol/(L.gcat) using TiO2 within the same 4-h operation period at a gas flow rate of 800 ml/min. The rate of CO2 photoreduction to formic acid emerges as the limiting factor in this integrated process, indicating a need for further optimization. Key parameters identified for optimal performance include a UV source of 500 W, a medium pH of 10, and a catalyst loading of 0.5 g/L. This study contributes to the advancement of CCU technologies by demonstrating the feasibility of integrating CO2 capture and photoreduction using membrane contactors and photocatalytic systems, paving the way for sustainable formic acid production.

Keywords

• CO2 capture
• CO2 photoreduction
• Formic acid
• Membrane contactor
• Photocatalysis