Development of Multifunctional Choline-Like Ionic Solvents for Ammonia and Carbon Dioxide Capture and Transformation of Latter

Abstract

This study developed two ionic solvents using chlorides from the choline (ChCl) family: ammonium salts with 2-hydroxyethyl groups, dimethyl-di(2-hydroxyethyl)-ammonium chloride (1) and methyl-tri(2-hydroxyethyl)-ammonium chloride (2) as the hydrogen bond acceptor (HBA) and glycerol (Gly) as the hydrogen bond donor (HBD) in a molar ratio of 1:2. The solubility of ammonia and carbon dioxide in these solvents and also solubility of carbon dioxide in glycelin (ChCl : Gly = 1:2) and pure glycerol were measured at temperatures ranging from 303.2 to 333.2 K and pressures from 100 to 813 kPa. From this, Henry’s law constants and the changes in thermodynamic functions during the absorption process were determined. We show that solubility of ammonia and carbon dioxide in these ionic solvents made from 2-hydroxyethyl-grafted hydrogen bond acceptors (HBAs) increases with the number of 2-hydroxyethyl groups compared to the glycelin comprising HBA with one 2-hydroxyethyl substituent only. Developed fluids also demonstrated catalytic activity in the cycloaddition of CO₂ to epichlorohydrin (ECH), producing chloropropylene carbonate (PC-Cl). Under reaction conditions of 100 °C, 650 kPa, and 2 mol % catalyst concentration, a 95% conversion of ECH was achieved within 6 h. The effect of various reaction conditions on the ECH conversion and PC-Cl yield was also investigated. Additionally, the densities (ρ) and viscosities (η) of both pure and gas-saturated fluids were measured, completing the comprehensive characterization of the ionic solvents.