Comparative kinetics of homogeneous reaction of CO₂ and unloaded/loaded amine using stopped-flow technique: A case study of MDEA solution

The stopped-flow technique was applied for the investigation of kinetics of CO₂ absorption into loaded MDEA solution over the range of MDEA concentration of 0.4 to 1.0 kmol/m³, CO₂ loading of 0.14 to 0.17 mol CO₂/mol amine and the temperature of 293 to 308 K. The kinetics of unloaded MDEA was also investigated for the comparison and a huge difference of results which should be equal theoretically was indicated between loaded and unloaded systems. Then, the effect of CO₂ loading on the kinetics was studied. As the loading increases, there is a turning point around loading of 0.10, below which the overall reaction constant decreases strongly. It was found that contribution of hydroxyl is a crucial to overall reaction rate constant and cannot be ignored and the influence of reverse reaction of MDEA and CO₂ can be ignored. The kinetics of loaded system obtained in this work was modified and interpreted well by the base-catalyzed mechanism with AARD of 6.29% and compares favorably with literature using gas-liquid apparatus. The kinetics of unloaded system in this work is approximately twice as that of literature and loaded system. This work provided literature review and interpretation of MDEA-CO₂-H₂O and is hopeful to shed light on kinetic study of CO₂ absorption in tertiary amine using stopped-flow apparatus.