Dual-Functionalized Ionic Liquid Biphasic Solvent for Carbon Dioxide Capture: High-Efficiency and Energy Saving.

To address the problems of high viscosity and difficult regeneration of the rich phase solution, a dual-functionalized ionic liquid ([DETAH][Tz]) was dissolved into a 1-propanol-water solvent to form a novel biphasic solvent for CO2 capture. The rich phase kept 96% of the total CO2 loading (1.713 mol mol-1) but only 44% of the total volume, and its viscosity was only 2.57 mPa s. As a regeneration promoter, 1-propanol helped the rich phase to maintain 90% of its initial loading after fifth regeneration. The high number of amine functional groups into [DETAH]+ and the equimolar reaction of [Tz]- provided the high CO2 loading, while [Tz]-H and 1-propanol ensured the high regeneration efficiency of the rich solution by enhancing the hydrolysis of RNCOO- to form HCO3-/CO32- and propyl carbonate. Due to a stronger polar and an aggregation of the CO2 absorption products in water, the CO2 products were enriched into the lower water phase while most of the 1-propanol was in the upper phase. The heat duty of [DETAH][Tz]-1-propanol-water was approximately 29.93% lower than [DETAH][Tz]-water (2.84 GJ ton-1 CO2) and 47.63% lower than MEA (3.80 GJ ton-1 CO2), which would be a promising candidate for CO2 capture.