A Membrane Contactor Enabling Energy-Efficient CO2 Capture from Point Sources with Deep Eutectic Solvents

We demonstrate a scalable and energy-efficient hollow fiber membrane contactor (HFMC)-based process using a green solvent for CO2 capture. This process uses a deep eutectic solvent (DES) in an HFMC to provide close interfacial interactions and contact between the DES and CO2. This approach overcomes disadvantages associated with direct absorption in DES and could potentially be applied to a variety of solvent-based CO2 capture methods. Commercial low-cost polymer hollow fiber membranes (e.g., microporous polypropylene) were evaluated for CO2 capture with reline, a prototypical DES. Single-gas measurements showed that the DES-based polypropylene HFMC can capture and separate CO2 while rejecting N2. From a mixed gas containing 50 mol % N2 and 50 mol % CO2, the DES-based HFMC separated CO2 with a purity of 96.9 mol %. The effect of several process parameters including solvent flow rate, pressure, and temperature on the CO2 separation performance was studied. The flux of the recovered CO2 was 67.43 mmole/m2/h at a feed pressure of 4 bar. In situ Fourier transform infrared (FTIR) measurements combined with density functional theory (DFT)-based molecular dynamics simulations revealed that reline absorbs CO2 by physical absorption without forming a new chemical compound, and CO2 separation by reline occurs via the pressure swing mechanism. This research provides fundamental insights about physical solvent-based separation processes and a pathway toward practical deployment.