Non-dispersive CO2 separation process using vacuum desorption and ionic liquids as carbon capture and utilization innovative technology

Abstract

Slowing down climate change requires urgent measures, and consequently, one of the main challenges of the scientific community is to develop innovative technologies to reduce carbon dioxide emissions to the atmosphere. Non-dispersive CO2 absorption using ionic liquids (ILs) as solvent and membrane vacuum regeneration (MVR) as desorption step are considered as a one of the most promising technologies for solvent regeneration in post-combustion CO2 capture and utilization (CCU) since high purity carbon dioxide streams are needed for technical valorization approach. In this work, the chemical binding 1-ethyl-3-methylimidazolium acetate ([emim][Ac]) and the physical solvent 1-ethyl-3-methylimidazolium methyl sulfate ([emim][MS]) have been selected. COSMO based/Aspen Plus methodology has been successfully executed to specify the COSMOSAC property method used in the commercial process simulator (Aspen Plus). Besides, a detailed two-dimensional mathematical model of MVR technology has been validated for the first time with [emim][MS] as a representative of physical ionic liquid solvent. The effect on CO2 desorbed flux and process efficiency have been tested at different operation conditions in order to compare the behavior of chemical and physical absorption based on ionic liquids. Low vacuum pressure and high temperature show a positive influence in the solvent regeneration process, while high liquid flow-rate increases the process performance but also decrease the CO2 desorption. The IL ([emim][Ac]) presented higher MVR performance (92 %) than the IL [emim][MS] (83 %) at the best operational conditions (313 K and 0.04 bar), in which the total energy consumption has been estimated on 0.62 and 0.34 MJe·kgCO2−1, respectively. These results noted the benefit of the MVR technology based on ILs compared to the conventional amino-based high -temperature regeneration process (1.55 MJe·kgCO2−1), presenting a step forward in the substitution of amines. This work provides a valuable tool to help in the decision-making to select the most promising ionic liquids, reducing laboratory efforts and, consequently, experimental costs.