Kinetics and Thermodynamics of CO2 Absorption into a Novel DETA-AMP-PMDETA Biphasic Solvent

A novel biphasic solvent consisting of diethylenetriamine (DETA), 2-amino-2-methyl-1-propanol (AMP), and pentamethyldiethylenetriamine (PMDETA) is considered as a promising CO2-capturing candidate because of its high absorption capacity, favorable phase separation behavior, fast desorption rate, and high cyclic capacity. In the present work, reaction kinetics and thermodynamics of CO2 absorption into the DETA-AMP-PMDETA biphasic solvent were studied. The kinetics process of CO2 absorption was described using the zwitterion mechanism and invoking the two-film theory. Under the fast pseudo-first-order regime, kinetics parameters, e.g., overall reaction rate constant (kov,mix), second-order rate constant (k2,mix), and enhancement factor (E), were determined. Kinetics results indicated that the CO2 reaction rate was mainly determined by DETA and AMP in the biphasic system, while PMDETA molecules would aggregate to form PMDETA clusters, which limited the absorption of CO2 to a certain extent. On the other hand, thermodynamics results showed that the regeneration heat of DETA-AMP-PMDETA biphasic solvents could be significantly reduced compared with that of MEA. In particular, the regeneration heat of the solvent 0.5 mol·L–1 (M) DETA + 1.5 M AMP + 3 M PMDETA (0.5D1.5A3P) was only 1.83 GJ·ton–1 CO2, which was approximately 52% lower than that of 30 wt % MEA. This finding suggested that the DETA-AMP-PMDETA biphasic solvent may be a good alternative to MEA to advance energy-efficient and economical CO2 capture.