Co‐extruded polymeric films for gas separation membranes

Abstract

In recent years, gas separation has become an important step in many production process streams and part of final products. Through the use of melt co-extrusion and subsequent orientation methods, gas separation membranes were produced entirely without the use of solvents, upon which current methods are highly dependent. Symmetric three layer membranes were produced using poly(ether-block-amide) (PEBA) copolymers, which serve as a selective material that exhibits a high CO 2 permeability relative to O 2 . Thin layers of PEBA are supported by a polypropylene (PP) layer that is made porous through the use of two methods: (1) inorganic fillers or (2) crystal phase transformation. Two membrane systems, PEBA/(PP 1 CaCO 3 ) and PEBA/b-PP, maintained a high CO 2 /O 2 selectivity while exhibiting reduced permeability. Incorporation of an annealing step either before or after orientation improves the membrane gas flux by 50 to 100%. The improvement in gas flux was a result of either elimination of strain induced crystallinity, which increases the selective layer permeability, or improvement of the PP crystal structure, which may increase pore size in the porous support layer.

The morphology and gas‐separation performance of membranes comprising multiwalled carbon nanotubes/polysulfone–Kapton

“…Figure 7 displays the gas permeability of Kapton-PSF blend precursors with various PSF compositions and their corresponding nanocomposite membranes for N 2 , CH 4 , O 2 , and CO 2 . In contrast, a smaller increase in CH 4 and N 2 permeability was observed. Tables III represents the gas-transport properties and separation performance of Kapton-PSF/nanocomposite membranes and also the measured gas permeation values for the precursors fabricated from blends of Kapton and PSF.…”

“…As a whole, they highly influence the phenomenon of gas transport. A comparison of the results of CH 4 and N 2 permeability leads to a conclusion that the permeability of these gases are similar ( Figure 6). It is expected that the permeability values of these gases are different from one another since this matrix has been derived from a blend of glass polymers.…”

“…In addition, Zhao et al 59 applied amino-modified multiwalled carbon nanotubes to prepare mixed-matrix membranes (MMMs). The results showed that the normalized N 2 , CH 4 , and CO 2 permeability had almost the same increase and the CO 2 /N 2 , CO 2 /H 2 , and CO 2 /CH 4 selectivity remained constant with increasing MWNT-NH 2 content. Thus, the incorporation of MWNT-NH 2 significantly enhanced the gas permeation properties of polymer/MWNT-NH 2 MMMs.…”

“…The high gas selectivity, combined with a relatively high gas permeability, allows many of these membranes to operate above the upper bound. 64 Ansaloni et al 58 put into practice different functionalities in multiwalled nanotubes with a diameter of 10-15 nm and synthesized poly(vinyl acetate) (PVA)/multiwalled nanotube (MWNT) membranes displaying high CO 2 permeability and good gas pair selectivity for CH 4 , H 2 , and N 2 . In addition, Zhao et al 59 applied amino-modified multiwalled carbon nanotubes to prepare mixed-matrix membranes (MMMs).…”

“…[3][4][5][6] Currently, commercially available purification and recovery techniques for this approach are gas sweetening, swing adsorption, amine treating, and cryogenic procedures, which have high costs and high energy use. [7][8][9][10] Within the last few years, researchers have been greatly interested in synthesizing novel membranes for gas-separation systems.…”