Low-Viscosity Nonaqueous Sulfolane-Amine-Methanol Solvent Blend for Reversible CO₂ Capture: Part II. Blend Optimization, Water Effect, and Speciation

This work is part II of the investigation of a low viscosity, low regeneration energy nonaqueous CO₂ capture solvent blend consisting of readily available chemicals diisopropylamine (DPA)–methanol–sulfolane and featuring the monomethyl carbonate anion (MMC) as a CO₂ absorption specie. The region of practical solvent composition, high CO₂ capacity, low regeneration energy, and avoidance of solvent solidification at a CO₂ capture condition is identified by the design of experiment methodology combined with solvent attenuated total reflectance–Fourier transform infrared and nuclear magnetic resonance monitoring and speciation analysis. Flue gas contains water vapor; hence, solvent water stability is important. The limit of solvent blend water content is determined to be 5 wt % because of MMC decomposition to DPA-bicarbonate and -carbamate.