Design and performance evaluation of low-volatility and low-viscosity absorbents for CO2 capture†

Deficiencies such as high viscosity, volatility, and rich phase precipitation limited the engineering application of non-aqueous absorbents. A series of high boiling point solvent screening experiments were conducted to develop an absorption saturated solution with a homogeneous phase at low viscosity (14.71 mPa s) in this study. Further addition of polyamines increased the absorption capacity by 42% (3.55 mol CO₂ per kg). The ¹³C NMR results indicated that in the DETA/MEA/NMF blended amine system, MEA was involved in the deprotonation process of DETA zwitterions as proton acceptors. Quantum chemical calculations were utilized to compare the energies of each possible single-step reaction, providing insights into the reaction pathways of the blended amine system. The rate constant of the MEA/CO₂ reaction was found to be 1.98 times that of the DETA/CO₂ reaction, indicating lower reaction activity, consistent with NMR results. In addition, the results of the analysis of weak interactions revealed that the hydrogen bonds were key factors affecting the viscosity change and precipitation in non-aqueous absorbents, providing a new method for designing novel low-viscosity non-aqueous absorbents. The combination of theoretical analysis and experimental results underscores the potential of the blended amine non-aqueous absorbent as a feasible alternative for the industrial applications of CO₂ capture.