Novel biphasic solvent based on 2MPRZ absorbent for post-combustion CO2 capture with low viscosity, superior phase-splitting behavior and low energy consumption

The CO 2 phase change absorbents(CPCAs) formed by introducing phase-splitting agents have attracted increasing attention because of their great energy-saving potential. However, the volatilization problem of the phase-splitting agents and the high viscosity of the solution affect the application of CPCAs. In this work, a novel CPCAs based on 2-Methylpiperazine (2MPRZ)/H 2 O was established by introducing triethylene glycol monobutyl ether (TGBE) with a high boiling point as a phase-splitting agent, and the 2MPRZ/H 2 O/TGBE system exhibited low volatility and low viscosity. The CO 2 capture performance of the novel CPCAs with different ratios was investigated in this work. The best CO 2 absorption rate was achieved by 2.5 M 2MPRZ/H 2 O/TGBE. The viscosity of this system before and after the CO 2 absorption process was merely 7.68 mPa·s and 11.64 mPa·s, respectively, and no volatilization of the phase-splitting agent was observed simultaneously. A convenient and rapid titration method was employed to determine the distribution of the 2MPRZ products in the two phases, which showed that 98 % of the 2MPRZ products were located in the CO 2 -rich phase. In addition, the CO 2 -rich phase captured 99 % of the total CO 2 , indicating that this system has superior phase-splitting behaviors. The regeneration energy consumption of this biphasic absorbent was 2.59 GJ/t CO 2 , which was 32.6 % lower than that of traditional MEA. Furthermore, the salting-out effect was proved to be the cause of the phase-splitting behavior by 13 C NMR analysis.