Experimental Investigation of the Absorption, Phase Transition, and Desorption Behavior of Biphasic Solvent Blends for Postcombustion CO2 Capture

Aqueous biphasic solvent blends consisting of diethylenetriamine (DETA) and a tertiary amine, N,N,N',N”,N”-pentamethyldiethylenetriamine (PMDETA) or bis[2-(N,N-dimethylamino)ethyl] ether (BDMAEE), were experimentally assessed. Results revealed that the composition of solvent blends greatly affected the CO2 loading capacity and dual-phase transition behavior. A speciation analysis of dual liquid phases suggested that CO2 absorption was a two-stage process, in which CO2 reacted with DETA initially, followed by the protonation of PMDETA or BDMAEE and the production of HCO3−/CO32− species lately. Rates of CO2 absorption and pressures of CO2 desorption were also measured for the selected solvent blends and compared with the benchmark monoethanolamine solvent.