Kinetics and Thermodynamics of CO 2 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 CO 2 -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 CO 2 absorption into the DETA-AMP-PMDETA biphasic solvent were studied. The kinetics process of CO 2 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 ( k ov,mix ), second-order rate constant ( k 2,mix ), and enhancement factor ( E ), were determined. Kinetics results indicated that the CO 2 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 CO 2 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 CO 2, 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 CO 2 capture.