Performance of sulfolane/DETA hybrids for CO₂ absorption: Phase splitting behavior, kinetics and thermodynamics

The phase splitting solvent as a promising alternative to MEA for CO₂ capture has received an increasing attention due to its low energy consumption. In this paper, the mixture of diethylenetriamine (DETA) and sulfolane was employed to absorb CO₂ from the simulated flue gas. Its phase splitting behavior was investigated. The species in each separated phase were identified using nuclear magnetic resonance (NMR), revealing that the upper layer was a CO₂-rich phase and mainly consisted of DETA and DETA-carbamate. Whereas, the lower layer was CO₂-lean phase with the sulfolane presented individually. The CO₂ absorption kinetics was also measured in a wetted-wall column as a function of temperatures, CO₂ loadings, and gas flow rate. Their impacts on the enhancement factor and mass transfer resistance were calculated by the Vapor-Liquid Equilibria (VLE) model, implying that the main CO₂ mass transfer resistance gradually transferred from the gas side to the liquid side with the CO₂ loading increasing from 0 to 2.21 mol L⁻¹. During the CO₂ absorption process, sulfolane acted as an inert solvent for substituting the role of water and separated from the absorption product. Consequently, the sensible heat and vaporization heat were substantially decreased by 59% and 12%, respectively. Hence the total heat duty was lowered by 19% which might noticeably advance the CO₂ capture technology.