Diamine based water-lean CO₂ solvent with extra high cyclic capacity and low viscosity

The industrial application of emerging water-lean solvents to CO₂ capture from flue gas is challenged by their high viscosity. In this work, we report a novel water-lean CO₂ solvent which possesses lower viscosity and higher CO₂ cyclic capacity than other water-lean solvents reported in the literature. The new solvent consists of N, N-dimethyl-1, 2-ethanediamine (DMEDA), physical cosolvent N-methyl-2-pyrrolidone (NMP) and up to 15% water (named ENH). We evaluated the effect of the solvent composition on the viscosity, CO₂ cyclic capacity and regeneration energy of ENH and compared it with the reference monoethanolamine (MEA) based solvents. It was found that ENH containing 5% H₂O (ENH-5%H₂O) with a CO₂ loading of 0.767 mol CO₂·mol amine^–1 had a viscosity of 7.603 mPa·S at 40 ˚C, which was comparable with that of traditional blended amines. Excellent cyclic capacity performance was also observed, with ENH-5% H₂O showing a 140% improvement compared to aqueous MEA. Regeneration energy of ENH-5% H₂O was estimated to be 2.418 GJ·tCO₂^–1 which is 36% lower than the 30 wt. % aqueous MEA solvent.