Novel tertiary amine-based biphasic solvent for energy-efficient CO2 capture with low corrosivity

A tertiary amine-based biphasic solvent, N,N-dimethylethanolamine (DMEA)/piperazine (PZ)/N-butanol (n-BuOH)/H2O, was proposed for energy-efficient CO2 capture. Low energy-consuming deprotonation dominated the CO2 desorption reaction, resulting in a Qrxn as low as 1.17 GJ/t CO2. Combining with the significantly reduced Qsen and Qlatent due to phase separation, an extremely low regeneration energy consumption (1.59 GJ/t CO2) was obtained, which was only 39.8% of 30 wt% MEA, and lower than most of reported biphasic solvents. The addition of n-BuOH not only induced the phase separation, but also reduced the activation energy of the reaction between DMEA and CO2. It worked together with PZ to improve the inherent slow absorption rate of DMEA to a comparable value with 30 wt% MEA. Although a decreased CO2 loading in the total solution was detected because the addition of n-BuOH reduced the equilibrium constant from 3.82 E+2 to 8.98 E+1, this biphasic solvent still achieved high CO2-rich loading (4.23 mol/L), large desorption capacity (3.77 mol/L), and superior desorption efficiency (89.1% at 393.15 K) owing to the good phase separation and desorption properties. In addition, the corrosion rate of CO2-rich phase was only 1.35% of CO2-loaded MEA. This research provided a promising alternative absorbent for CO2 capture.