Precipitating non-aqueous amine systems for absorption of carbon dioxide using 2-amino-2-methyl-1-propanol

The aim of this study was to find a solvent to replace N-methyl-2-pyrrolidone (NMP) in CO₂ absorption systems containing the amine 2-amino-2-methyl-1-propanol (AMP), in order to reduce the health risks associated with handling, as NMP is reproductively toxic. Seven organic solvents were investigated: dimethyl sulfoxide (DMSO), 3-(dimethylamino)propionitrile (3DMAPN), 1-pentanol (1 P), propylene carbonate (PC), 4-heptanone (4 H), 1-methylimidazole (1MIMI) and cyclohexanol (CH). Henry's constant, the CO₂ solubility and the differential heat of absorption were determined for the pure solvents, and in solvent mixtures containing 25 wt% AMP, at 25 °C and 40 °C. Three of the solvents were found to have promising absorption properties: DMSO, 3DMAPN and 1 P. In mixtures with AMP, precipitation was formed at both 25 and 40 °C, and the CO₂ absorption capacity was similar to that in the AMP–NMP system, in terms of the CO₂ loading for a given partial pressure of CO₂. The results also indicated that the reaction of AMP and CO₂ in these solvents can be described by the zwitterion reaction mechanism.