CO2 Capture in Flue Gas: Semiempirical Approach to Select a Potential Physical Solvent

The reported work aims at proposing a method to select potential physical solvents for CO2 absorption in flue gas. A parametric approach based on solubility data available in the open literature is engaged. It appears that CO2 capture with physical solvents is dominated by two fundamental aspects. On one hand, solvent-solvent interactions, characterized by the Hildebrand solubility parameter, have to be minimized so as to facilitate CO2 incorporation into the solvent. On the other hand, CO2-solvent interactions, which can be estimated by ab initio calculations, have to be maximized in order to allow good cohesion between CO2 and the solvent molecules. Considering these two requirements, several types of solvents are highlighted, namely, ethers, esters, ketones, tertiary amines, and alkyl phosphates. This parametric approach differs notably from similar works about another acid gas, SO2, and the forthcoming differences are discussed. Some mechanistic considerations are also given about the critical problems of CO2/N2 selectivity.