Energy-Efficient Biphasic Solvents for Industrial Carbon Capture: Role of Physical Solvents on CO2 Absorption and Phase Splitting

Physical solvent is a promising alternative for the phase splitting of solvent to drastically reduce the regeneration energy during CO₂ capture. Here, an aqueous biphasic solvent, optimally composed of 30 wt % polyamine (N, N-dimethylpropylamine, DMPA) and 50 wt % physical solvent (polyethyleneglycol dimethyl ether, NHD), is prepared, which presents high cyclic loading, low regeneration energy, and good stability. L₁₆(4⁵) orthogonal tests are performed to comprehensively evaluate the mass-transfer kinetics and the effect of crucial conditions, verifying the weak effect of NHD solvent on mass transfer. The solvent effect of NHD could decrease the energy barrier of carbamate generation from zwitterions (DMPA⁺COO^–) to enhance chemical absorption. The low polarity of the NHD solvent provides source motivation and accelerates phase splitting. Time–space resolution distribution of CO₂ capacity is established based on a scale-up separator with 5 L solvent, which supports multiscale force analysis for the various stages during phase splitting. The drag force of the homogeneous cluster was first introduced into separation dynamics, referred to as an important reason for the various splitting behaviors of a scale-up separator.