New Insights and Assessment of Primary Alkanolamine/Sulfolane Biphasic Solutions for Post-combustion CO2 Capture: Absorption, Desorption, Phase Separation, and Technological Process

The sulfolane was, surprisingly, found to be a universal phase-splitting solvent in a serial of aqueous primary alkanolamine solution for CO2 removal; the reaction product of carbamate and hydrophilicity of amine can be the key factor for triggering phase change; also, the phase change can have a significant effect on CO2 capture performance. To comprehensively understand the effect of phase change on absorption, stripping, and phase separation performance, MEA sulfolane-based solution was chosen as a typical biphasic system for investigation. First, the experimental results revealed that the phase change can dramatically decrease the absorption rate and lead to less CO2 capacity in absorption processes. Second, the enriched MEA in separated solution can substantially decrease the energy consumption for CO2 stripping but exorbitant concentration of MEA can significantly reduce the CO2 removal efficiency in a quasicycle of absorption and desorption processes. Third, the phase separation rate of emulsion of MEA/sulfolane solution can be obviously improved by the increasing temperature, and fortunately, the increasing temperature had less effect on miscible solubility of MEA and sulfolane in two separated phases. Finally, on consideration of the absorption rate, energy consumption, and phase separation rate, a new technological process was proposed for CO2 capture using primary alkanolamine sulfolane-based solution to achieve the goal of relative high CO2 removal efficiency and energy saving.