To
address the problems of the relatively high energy penalty and
corrosivity of aqueous biphasic solvents, a novel nonaqueous biphasic
solvent composed of 2-((2-aminoethyl)amino)ethanol (AEEA), dimethyl
sulfoxide (DMSO), and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) was proposed for CO2 capture. With optimization, this novel AEEA–DMSO–PMDETA
(A–D–P) biphasic solvent could achieve a high CO2 loading of 1.75 mol·mol–1, of which
96.8% of the absorbed CO2 was enriched in the lower phase
with only 49.6% of the total volume. 13C NMR analysis and
quantum calculations revealed that A–D–P could absorb
CO2 to form not only carbamate but also carbamic acid species,
which were stabilized by DMSO via hydrogen-bonding interactions. Most
products were highly polar and preferred to dissolve in polar DMSO
rather than the less polar PMDETA, thus leading to the phase change.
The thermodynamics results showed that the heat duty of A–D–P
was only 1.66 GJ·ton–1 CO2 (393.15
K), which was significantly lower than that of the benchmark MEA (3.59
GJ·ton–1 CO2) and the reported aqueous
biphasic solvents. Moreover, A–D–P presented a noncorrosive
behavior to steel after CO2 saturation, clearly showing
its superiority over MEA and the aqueous biphasic solvents. Therefore,
with superior properties of energy savings and noncorrosiveness, the
A–D–P biphasic solvent could be a promising candidate
for CO2 capture.
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