Regulating the absorption and solid regeneration performance of a novel anhydrous solid–liquid phase change absorbent for carbon capture

The solid–liquid biphasic solvent has great energy-saving potential, but its absorption rate and solid regeneration performance need to be improved. In this study, a new solid–liquid biphasic solvent was proposed using 1,3-diaminopropane (DAP) as the main absorbent, 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) as the absorption enhancer, and n-propanol (NPA) as the organic diluent and regeneration promoter. AMP and PZ could boost the CO2 absorption and thus shorten the absorption saturation time from 120 min to 80 and 60 min, and further reduce the regeneration energy to 1.30 and 1.35 GJ·t−1 CO2 as well. They were much lower than the reported biphasic absorbents and only 34.2 % and 35.6 % of the 3.80 GJ·t−1 CO2 produced by 5 M MEA. Moreover, adding a small amount of NPA to the lower phase could significantly increase the desorption efficiency to 84.5 %, whereas no CO2 was desorbed without the help of NPA. Experimental and theoretical analysis indicated that during CO2 absorption, the DAP-NPA system absorbed CO2 to produce DAPCOO- and protonated DAP. Adding AMP or PZ to the system enhanced product coupling by replacing DAPCOO- with a small amount of AMPCOO- or PZCOO-, thereby accelerating the reaction. Furthermore, during regeneration, NPA would weaken the hydrogen bonding between the products and promote the CO2 desorption and the regeneration of solid products. This work developed a promising solid–liquid biphasic solvent with good comprehensive performance.