Investigation of CO₂ Rapid Phase Change Absorbent System Based on Amino Acid Salts and Ether Solvents

The chemical absorption method using MEA has been one of the most effective CO2 capture technologies, but the problems of low process efficiency and poor economics limit its application. In this work, the rapid phase change absorbent composed of alcohol ether solvent and potassium amino acid salt (AaK) solution was investigated, and the effects of different AaKs and ethers on the phase change behavior, phase separation mechanism, and CO2 absorption performance of the absorbent were analyzed. The results showed that when the carbon chain of the linear AaK was longer, the solubility in water was larger, and the lower liquid phase (LP) volume, phase separation time, AaK enrichment in the LP, and CO2 molar loading were larger. When the alkyl group of the branched-chain AaK was larger, the solubility in water was smaller, and the gas–liquid mass transfer, enrichment effect, and absorption rate were smaller. When the ether bonds of ether solvent were greater, the solubility of organic salts and competition for water were stronger; thus, the LP volume was smaller. Moreover, the absorption rate and CO2 loading of AaK systems were affected by the spatial structure effect of amino and carboxyl groups and the viscosity effect of solvent before absorption.