Various Techniques for Preparation of Thin‐Film Composite Mixed‐Matrix Membranes for CO₂ Separation

Abstract

The application of thin‐film composite mixed‐matrix membranes (TFC‐MMMs) for gas separation is widely considered as an efficient separation technology. The principal methods for the preparation of TFC‐MMMs are dip‐coating, phase inversion, and interfacial polymerization comprising different types of support layers. These methods influence the CO2 permeation over the selective and support layers. A comprehensive review is provided for capturing new details of progress achieved in developing TFC‐MMMs with detailed performance of gas separation in the previous few years. Various preparation techniques of TFC‐MMMs and their effect on the gas separation performance of the prepared membranes are described.

Poly(ether-block-amide) Copolymer Membranes in CO2 Separation Applications

“…A typical TFC is composed of (i) a porous layer that serves as a mechanical support introducing a minimum limit to the mass transfer thanks to its pores, (ii) a very thin selective layer, for the selective separation of a gas mixture, and (iii) a protective layer that is added in order to control the membrane performance by avoiding any possible cracks or defects on the selective layer surface (again without adding any transport resistance). Moreover, recently, a very common procedure is to add a gutter layer in between the porous support and the selective layer to prevent the penetration of the coating solution into the pores of the support. − Pore filling prompts an increase in the thickness of the selective layer and hence a decline in membrane permeance . Highly gas permeable polydimethylsiloxane (PDMS) and poly­(1-(trimethylsilyl)-1-propyne) (PTMSP) coatings are the most commonly used gutter layers in a TFC membrane fabrication.…”

CO2/N2 Gas Separation Using Pebax/ZIF-7—PSf Composite Membranes

“…On the selective layer used on the substrate, a protective layer (or coating layer) of polydimethylsiloxane (PDMS) or poly[1-(trimethylsilyl)-1-propyne] (PTMSP) can also be applied to prevent damage such as the aging of membranes according to the characteristics of macromolecules and improve the stability by smoothening the surface. However, in the case of PTMSP, because of the drastic decline in CO 2 permeation due to aging, PDMS is preferred as a protective layer [10,13,14]. Metal-organic frameworks (MOFs), among filling materials added into the polymer, are porous crystals produced by the bonding of the metal cluster with organic ligands, which have a wide surface area and pore volume and can be variously formed following the bonding method.…”

Recent Progress on Pebax-Based Thin Film Nanocomposite Membranes for CO2 Capture: The State of the Art and Future Outlooks

“…157 Since the substrate layer provides only pathways for the channeling species with minimal effect on molecular separation, its gas transfer resistance can be neglected. 44,223 Depending on the membrane fabrication conditions (i.e., type of solvents, additive ratio, etc. ), the substrate can have spongetype or finger-like structures.…”

“…74 To avoid damaging the membrane substrate, supports with high solvent resistance are favored. 44 Kiss-coating also known as the meniscus-coating method is another technique for large-scale membrane fabrication. This method is a modified version of the dip-coating process where a one-sided contact between the surface of the substrate and the polymer solution is promoted.…”

“…38 Porous inorganic membranes are typically composed of a porous top (thin) layer such as zeolite, silicon carbide/nitride, carbon, cordierite, mullite, mica, and metal oxides (i.e., copper, alumina, titanium, tin, zirconia), reinforced on a porous metal or ceramic support. 42,43 Compared to polymeric membranes, inorganic membranes typically present higher selectivity and permeability values, particularly at elevated temperatures and pressures, 44,45 other than these membranes also have extraordinary thermal endurance, great chemical resistance, minor plasticization, and controllable pore size distribution. 46−48 For large-scale applications, however, these membranes have encountered serious difficulties such as high material price, lack of processability, fragility, and difficulties in handling.…”