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)/H 2 O, was proposed for energy-efficient CO 2 capture. Low energy-consuming deprotonation dominated the CO 2 desorption reaction, resulting in a Q rxn as low as 1.17 GJ/t CO 2 . Combining with the significantly reduced Q sen and Q latent due to phase separation, an extremely low regeneration energy consumption (1.59 GJ/t CO 2 ) 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 CO 2 . 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 CO 2 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 CO 2 -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 CO 2 -rich phase was only 1.35% of CO 2 -loaded MEA. This research provided a promising alternative absorbent for CO 2 capture. • A tertiary amine-based biphasic solvent DMEA/PZ/ n -BuOH/H 2 O was proposed. • Low Q rxn (1.17 GJ/t CO 2 ) resulted in low Q reg (1.59 GJ/t CO 2 ), 39.8% of 30 wt% MEA. • The hydrogen bond was revealed to be the key factor triggering the phase separation. • Superior desorption capacity (3.77 mol/L) and efficiency (89.1%) were obtained. • The corrosion rate of CO 2 -rich phase was only 1.35% of CO 2 -loaded MEA.