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

The CO2 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)/H2O was established by introducing triethylene glycol monobutyl ether (TGBE) with a high boiling point as a phase-splitting agent, and the 2MPRZ/H2O/TGBE system exhibited low volatility and low viscosity. The CO2 capture performance of the novel CPCAs with different ratios was investigated in this work. The best CO2 absorption rate was achieved by 2.5 M 2MPRZ/H2O/TGBE. The viscosity of this system before and after the CO2 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 CO2-rich phase. In addition, the CO2-rich phase captured 99 % of the total CO2, indicating that this system has superior phase-splitting behaviors. The regeneration energy consumption of this biphasic absorbent was 2.59 GJ/t CO2, 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 13C NMR analysis.