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^-/CO₃^2- 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.