Thermodynamic Modeling and Experimental Study of CO₂ Dissolution in New Absorbents for Post-Combustion CO₂ Capture Processes

Abstract

Demixing solvents have been suggested as an alternative to aqueous solutions of alkanolamines for the decarbonation of industrial effluents. These solvents undergo a liquid–liquid phase separation when heated. A phase-separation step could be integrated in the carbon dioxide (CO2) capture process to reduce energetic cost of the solvent regeneration step. As part of a general project on the dissolution of CO2 in aqueous solutions of piperidines, 3-methylpiperidine and 4-methylpiperidine have been investigated. The enthalpies of solution of CO2 in aqueous solutions of those methylpiperidines have been measured using a flow calorimetric technique. This technique makes it possible to simultaneously determine the enthalpies of solution and CO2 solubility limits. The experimental data were used to develop a thermodynamic model representative of phase equilibrium and enthalpy of solution. The carbamate formation constants of the 3-methylpiperidine and 4-methylpiperidine are adjusted in the model. The thermodynamic model is used to discuss the mechanism of CO2 dissolution.