Energy-saving CO2 capture using sulfolane-regulated biphasic solvent

Because of phase separation characteristics, biphasic solvents are recognized as promising absorbents for CO2 capture with low regeneration heat consumption. However, limited CO2 loading in CO2-rich phase, associated with excessive CO2-rich phase volume, challenges the energy-saving regeneration potential of mixed-amine biphasic solvents. In this study, sulfolane was employed as a phase splitter to improve the phase separation properties of N,N-diethylenetriamine (DETA)-N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) biphasic absorbent. By introducing the hydrophobic sulfolane, large CO2 capacity (increased from 3.56 to 6.48 mol/L) and low CO2-rich phase volume (decreased from 100% to 27.1%) were simultaneously achieved. Moreover, sulfolane acted as an absorption accelerator to increase the CO2 absorption rate in DETA-PMDETA-sulfolane solvent to 1.3 times the corresponding DETA-PMDETA solvent. Benefiting from the large CO2 capacity associated with favorable phase separation behavior, DETA-PMDETA-sulfolane has a minimized regeneration heat estimated at 1.86 GJ/t-CO2 at a lean CO2-loading of 0.55 mol/mol. This is 53.4% lower than the regeneration heat (3.99 GJ/t-CO2) using 5 M monoethanolamine solvent.