Comparison between Cyrene and NMP as Solvents for CO2 Removal

N-Methyl-2-Pyrrolidone (NMP) is one of the most used solvents for CO2 removal from gaseous streams by physical absorption and, recently, it has also been considered as a component of hybrid solvents performing both physical and chemical absorption for possible applications to the capture of CO2 from flue gas streams. However, NMP has some drawbacks and it has been included in the list of ‘Substances of Very High Concern’ according to the European Regulation No. 1907/2006. For this reason, alternative solvents are being considered. Cyrene is a biodegradable, non-mutagenic, non-toxic and biomass-derived solvent, having similar characteristics to NMP. The main similarity between the two species consists in the fact that they result to be dipolar aprotic solvents, as proved by the values of both Kamlet–Abboud–Taft and Hansen space parameters. Despite that, NMP and Cyrene differ in physical properties as boiling point, flash point, autoignition temperature and water solubility. However, to the authors’ knowledge, no comparison is available in the literature regarding the solubility of CO2, which is a key parameter for defining the suitability of a solvent for CO2 removal. In the context of the PRIN 2022 project “GREEN-based water-lean SOLvent for CO2 capture” (GREENSOL), funded by the European Union – NextGenerationEU, a detailed analysis of all the CO2 solubility data available in the literature is presented in this work in order to determine whether Cyrene can be used as a bio-based alternative to NMP as solvent for physical absorption.