High-Throughput Screening and Kinetic Analysis of CO₂ Absorbents via Optical Reflection Imaging

With fossil fuels expected to remain a dominant global energy source, sustained CO₂ emissions demand efficient mitigation strategies. Chemisorption-based postcombustion capture is widely applied due to its selectivity and operational simplicity. Understanding the absorption kinetics is critical for both elucidating fundamental reaction mechanisms and optimizing solvent performance. Herein, we present a prism-based reflection optical imaging platform integrated with a multichannel gas-injection system for quantitative, in situ, and high-throughput visualization of dynamic CO₂ absorption in liquid absorbents. The approach exploited refractive index changes induced by CO₂ absorption, detected as variations in reflected light intensity. The high-throughput capability enabled a direct comparison of absorption capacities and kinetic parameters within a single experiment. Monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA) were investigated as representative primary, secondary, and tertiary alkanolamine absorbents. Kinetic analysis revealed that primary and secondary amines follow similar reaction pathways but exhibit different reaction rates, whereas tertiary amines proceed via a distinct mechanism and show a stronger dependence of the absorption rate on the absorbent concentration, characterized by distinct reaction orders and rate constants. This work established reflection-based optical imaging as a low-cost, versatile platform for high-throughput screening of gas-liquid absorption kinetics and for guiding data-driven absorbent discovery.