Facilitated transport membranes for CO2/CH4 separation - State of the art

Multi-Functional Polymer Membranes Enable Integrated CO2 Capture and Conversion in a Single, Continuous-Flow Membrane Reactor under Mild Conditions

“…In order to comprehensively evaluate the gas separation performance of P4VP-C2-HCO 3 , the CO 2 permeance and CO 2 /N 2 selectivity of P4VP-C2-HCO 3 was measured as a function of CO 2 partial pressure from 0.1 kPa (i.e., similar to the CO 2 concentration in air) up to 86 kPa. As shown in Figure , the CO 2 permeance and CO 2 /N 2 selectivity increase with decreasing CO 2 partial pressure, which suggests that the P4VP-C2-HCO 3 membrane behaves like a facilitated transport membrane. , Notably, at a low CO 2 partial pressure of approximately 0.1 kPa, the P4VP-C2-HCO 3 membrane exhibited a high CO 2 permeance of 1300 ± 100 GPU and a high CO 2 /N 2 selectivity of 3000 ± 1000. The high uncertainty in the CO 2 /N 2 selectivity measurement at 0.1 kPa is likely due to the small amount of CO 2 in the permeate stream at this pressure and hence the relatively low signal-to-noise ratio of the CO 2 peak in gas chromatography.…”

Progressing thin-film membrane designs for post-combustion CO2 capture: performance or practicality?

“…Asymmetric polymeric substrates with a porous skin layer made from commercial polymers, such as polyacrylonitrile (PAN), polysulfone (PSF) and polyethersulfone (PES), are the most commonly used substrate materials in TFC owing to their low cost, ease of processing and mechanical exibility. [53][54][55][56] The function of the gutter layer is to prevent the penetration of selective layer materials into the surface pores of the substrate, which will otherwise drastically increase the gas transport resistance at the skin layer because the selective material coating solution is typically made very dilute with low viscosity to obtain the desired ultra-thinness. Also, it serves as a protective interlayer that keeps the polymeric substrates from directly contacting the destructive aprotic organic solvents used by a number of selective polymer materials.…”

“…This is one of the main reasons why TFC membranes for CO 2 /N 2 separation are oen reported with quite scattered separation performances even using an almost identical combination of selective, gutter and substrate materials. 53,109,110 For example, PAN is a more predominantly used polymeric substrate material than PES and PSF in TFC membrane studies partly because PAN substrates are usually obtained with a better control over their pore size distribution than the others, which could provide more consistent overall TFC performance. 9,24 Some common strategies to modify the substrate fabrication process for generating a more favorable surface pore structure include (1) decreasing the concentration of the polymer dope solution to enhance porosity, (2) incorporating pore-forming additives like polyethylene glycol (PEG) or polyvinylpyrrolidone (PVP) in the dope to create extra porosity, and (3) using block copolymers with self-assembling properties to form segregated microphases that could be selectively dissolved to promote the formation of small and more regularly sized pores.…”

“…183,184 Also, the requirement of high humidity by FTMs could be an issue for the porous polymeric substrates as studies have shown that long-term exposure to water could lead to its condensation onto and hence the blocking of skin layer pores. 53 These issues should be paid more attention to in future FTM-based TFC designs. Lastly, emerging FTM designs using mobile carriers, like ionic liquids (ILs) and amino acid salts, are denitely worth more attention.…”

Effects of Porous Supports in Thin-Film Composite Membranes on CO2 Separation Performances

“…As most CO 2 -containing streams include water vapor, and water is involved in CO 2 transport mechanism, water vapor is critical in membranes for CO 2 separation. Water vapor could not only contribute to the reversible reaction involved in the facilitated transport mechanism and swell the selective layer membrane materials [ 27 , 28 ]. However, these also significantly affect the mass transfer in porous supports.…”