Fundamentals of Membrane Gas Separation
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This chapter contains sections titled: Introduction Polymer Structure and Permeation Behavior Membranes from Glassy Polymers: Physical Aging Membranes from Rubbery Polymers: Enhanced CO2 Selectivity Summary ReferencesKeywords:
Synthetic membrane
Separation (statistics)
Polymeric membrane
On the way to membranes for the separation of industrially important gas pairs, researchers have devised the new ladder polymer PIM-EA-TB, which was found to have remarkable selectivity and permeability for several technically relevant gas pairs. A possible explanation of these observations is given.
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Synthetic membrane
Polymeric membrane
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Abstract Polyetherimide (PEI) is an extraordinary type of polyimide with excellent thermal and mechanical properties. The polymer is also gas permeable and is considered one of the best membranes for gas separation. Despite the high selectivity, PEI suffers from low permeability due to the trade‐off between phenomena in polymers. To overcome this limitation, fillers are added during the membrane preparation to create voids for better gas transport. In this paper, permeability and selectivity data of PEI membranes for the separation of oxygen, carbon dioxide, and helium are discussed. The paper also summarizes the reported studies for adding fillers to improve the membrane performance.
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Polymeric membrane
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Ketoprofen
Cationic polymerization
Synthetic membrane
Phosphatidylethanolamine
Membrane permeability
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Kansy et al first introduced the Parallel artificial membrane permeation assay (PAMPA) in 1998. In this system, the permeability through a membrane formed by a mixture of lecithin and an inert organic solvent on a filter support is assessed. PAMPA shows definite trends in the ability of molecules to permeate membranes by transcellular passive diffusion. Its simplicity, low cost, high throughput, and wide pH range make it very attractive in modern drug discovery. Based on this concept, Whohnsland et al, Sugano et al and Zhu et al modified the assay and used it to screen compound permeability. We used PAMPA for the permeation prediction of M100240, which was unable to be determined by cell-based assays due to compound instability.In this study, 92 commercially available agents provided the structural diversity used to generate a mathematical prediction model for human fraction absorbed, M100240--an acetate thioester of MDL 100,173. Permeation of M100240 and MDL 100,173 was evaluated using the parallel artificial membrane permeability assay (PAMPA). The donor and recipient solutions consisted of 0.5N HCl (pH 1.5) or phosphate-buffered saline (pH 5.5 or 7.4) with 2% dimethyl sulfoxide. The donor solution also contained 200 mM M100240 or MDL 100,173.M100240 had a medium permeation at pH 5.5 (2.99%), corresponding to a high predicted Fa in humans (92%). Permeation of MDL 100,173 was low at this pH (0.72%), corresponding to a medium-to-low predicted Fa (46). At pH 7.4, the permeation of M100240 was low (approximately 1%) and no permeation was apparent for MDL 100,173.We predicted M100240 is likely to be well absorbed via passive diffusion across the human gastrointestinal tract following oral administration.
Synthetic membrane
Membrane permeability
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Synthetic membrane
Membrane permeability
Semipermeable membrane
Lipophilicity
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Chapter 2 Two reaction routes for the preparation of aromatic polyoxadiazoles and polytriazoles Syntheses and properties summary Results and discussion Poly-1,3,4-oxadiazoles via polyhydrazides One-step synthesis of poly-1,3,4-oxadiazoles Poly-172,4-triazole via polyhydrazide Poly-1,2,4-triazoles via poly-1,3,4-oxadiazoles Conclusions Acknowledgement Literature Chapter 3 Syntheses and properties of related polyoxadiazoles and polytriazoles summary Introduction Experimental Materials Polyb-, m-pheny1ene)hydrazide synthesis Poly-1,2,4-triazole synthesis using polyhydrazide as a precursor polymer Poly-1,3,4-oxadiazole synthesis Preparation of homogeneous fïlms Characterisation Results and discussion Poly-1,2,4-t~iazoles via polyhydrazides Poly-l,3,4-oxadiazoles Conclusions Acknowledgement Literature Chapter 4 Gas separation properties of new polyoxadiazole and polytriazole membranes summary Characterisation Results and discussion Influence of the poly-1,2,4-triazole batch Influence of the casting conditions Influence of the feed composition Influence ofthe macromolecular structure Influence of the p -and m-phenylene in poly-l,2,4-triazoles Influence of p-phenyl substitution in poly-1,2,4-triazoles Relation between permeability and free volume of the polymers studied Conclusions Acknowledgement Literature summary
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Polydimethylsiloxane
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Drug permeation through skin, or a synthetic membrane, from locally acting pharmaceutical products can be influenced by the permeation behaviour of pharmaceutical excipients.Terahertz time-domain technology is investigated as a non-invasive method for a direct and accurate measurement of excipients permeation through synthetic membranes or human skin.A series of in-vitro release and skin permeation experiments of liquid excipients (e.g. propylene glycol and polyethylene glycol 400) has been conducted with vertical diffusion cells. The permeation profiles of excipients through different synthetic membranes or skin were obtained using Terahertz pulses providing a direct measurement. Corresponding permeation flux and permeability coefficient values were calculated based on temporal changes of the terahertz pulses.The influence of different experimental conditions, such as the polarity of the membrane and the viscosity of the permeant, was assessed in release experiments. Specific transmembrane flux values of those excipients were directly calculated with statistical differences between cases. Finally, an attempt to estimate the skin permeation of propylene glycol with this technique was also achieved. All these permeation results were likely comparable to those obtained by other authors with usual analytical techniques.Terahertz time-domain technology is shown to be a suitable technique for an accurate and non-destructive measurement of the permeation of liquid substances through different synthetic membranes or even human skin.
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Polymeric membranes are widely used for gas separation purposes but their performance is restricted by the upper bound trade-off discovered by Robeson in 1991. The polymeric membrane can be glassy, rubbery or a blend of these two polymers. This review paper discusses the properties of glassy polymer membranes and their performance in gas separation. The area of improvement for glassy membrane with development of mixed matrix membrane is also highlighted.
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The rapid expansion of gas separation technology since it was first introduced is promoted by the beneficial selective permeability capability of the polymeric membranes. Up to the currently available information, a large number of studies have reported polymeric membranes permeability and selectivity performances for a different type of gasses. However, trends showed that separation of gases using as per in synthesized polymers had reached a bottlenecks performance limits. Due to this reason, membranes in the form of asymmetric and composite structures is seen as an interesting option of membrane modification to improve the performance and economic value of the membranes alongside with an introduction of new processes to the field. An introduction of new polymers during membrane fabrication leads to a formation of its unique structure depending on the polymers. Thus, structured studies are needed to determine the kinetic behavior of the new addition to membrane structures. This review examines the ongoing progress made in understanding the effects of the different polymers additives to the structural modification and the gas separation performances of the carbon membranes. A reduction of defects consisted of pore holes, and cracks on carbon membranes could be minimized with the right selection of polymer precursor.
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Carbon fibers
Membrane structure
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