DescriptionMembrane gas separation is an important part of various industrial processes, and can be implemented for CO2 capture. Supported liquid membranes (SLMs) are considered one of the most efficient gas separation membrane processes due to potential higher permeability and ease of scalability. In SLM, the separation takes place via the solution-diffusion mechanism, in which the diffusion coefficient is about three-four times higher than that in polymer membranes. The most widely-studied organic liquids for this purpose are fluorinated ionic liquids (ILs). It has been shown that fluorination of ILs can lead to increased CO2 solubility . High cost, high viscosity, and environmental issues of ILs further curtail the commercial implementation of IL-based SLMs for gas separation. Here, we study the applicability of an organic liquid, namely, perfluoropolyether oil (Krytox oil), as the liquid medium in SLMs for CO2 capture. The CO2 absorption and solubility in the oil are measured experimentally using a magnetic suspension balance. The transport properties of the oil, i.e., the viscosity and diffusivity of CO2 in the oil for varying conditions of temperature, pressure and polymer chain length are further studied using equilibrium molecular dynamics simulations. The SLMs, are fabricated by infusing porous flat sheet PVDF membranes (pore diameter of approximately 30 nm) with 15.5 μL cm-2 of oil using a micropipette. The gas separation performance of SLMs is tested by measuring single gas permeability and ideal selectivity using pure CO2, N2, CO, CH4 and H2 gas using an in-house gas separation set-up at various pressures and temperatures. The mixed gas separation performance is also studied with some common gas pairs, e.g., CO2/CH4, CO2/N2 and CO2/H2. Higher CO2 solubility and diffusivity are observed in KrytoxTM oil compared to those in fluorinated ILs at the same temperature and pressure. The experimental Henry’s constant is 4 times lower, and the computed diffusion coefficient is 2 times higher than those in fluorinated ILs. The highest gas permeability is observed for CO2 which is almost 2 times higher than that of fluorinated ILs. Comparing the selectivity results to the upper-bound values for the selectivity vs. permeability of polymer membranes (Robeson plot), it can be concluded that these novel SLMs have better ideal-selection properties than the commonly used, industrial polymer membranes.
|Period||1 Dec 2021|
|Degree of Recognition||International|