Hydrogen separation polysulfone membranes

Hydrogen Hydrogen recovery was the first large commercial membrane gas separation. Polysulfone fiber membranes became available in 1980 at a time when H9 needs were rising, and these novel membranes qiiickly came to dominate the market. Applications include recovery of H9 from ammonia purge gas, and extraction of H9 from petroleum crackiug streams. Hydrogen once diverted to low-quahty fuel use is now recovered to become ammonia, or is used to desulfurize fuel, etc. H9 is the fast gas. 

The polyimide membrane is reported to be capable of operating at temperatures up to 150°C compared to upper limits of 100°C for PR ISM separators and 60°C for cellulose acetate.46 Permeabilities increase with temperature while selectivities normally drop. The second way to overcome the lower permeabilities is to operate the Ube system at higher temperatures than possible with polysulfone or cellulose acetate. Even at the high temperatures, the polyimide selectivity will remain high enough for the abovementioned hydrogen separations. Thus, one expects the Ube system to be competitive with PRISM separators for many hydrogen applications. 

The first company to produce a successful membrane-based gas-separation process was Permea, now a division of Air Products, which introduced hollow-fme-fiber polysulfone membranes for the separation of hydrogen from ammonia reactor purge gas in 1980. This application was an immediate success the feed gas was clean and free of condensable components that might damage the membranes, and the value of the recovered hydrogen provided short payback times. Within a few years, many ammonia plants worldwide had installed these units. Several hundred hydrogen-separating systems have now been installed by Permea and its competitors. 

Hydrogen separation was the first commercial usage for membrane-based gas separations, and it is of great importance in many petrochemical processes. Polysulfone... 

Khan, AL, Cano-Odena, A, Gutierrez, Minguilldn, C and Vankelecom, IFJ (2010), Hydrogen separation and purification using polysulfone acrylate-zeolite mixed matrix membranes, J Membr Sci, 350,340-346. 

Monsanto and Ube (Japan) developed membrane processes for purification of hydrogen gas mixtures. This process is based on the selective diffusion of hydrogen through semi-permeable membranes in the form of hollow fibers. The Monsanto PRISM separator process (owned by Air Products as of 2004) uses a polysulfone fiber whereas Ube uses an aromatic polyimide fiber.46... 

Commercial membranes for CO2 removal are polymer based, and the materials of choice are cellulose acetate, polyimides, polyamides, polysulfone, polycarbonates, and polyeth-erimide [12]. The most tested and used material is cellulose acetate, although polyimide has also some potential in certain CO2 removal applications. The properties of polyimides and other polymers can be modified to enhance the performance of the membrane. For instance, polyimide membranes were initially used for hydrogen recovery, but they were then modified for CO2 removal [13]. Cellulose acetate membranes were initially developed for reverse osmosis [14], and now they are the most popular CO2 removal membrane. To overcome state-of-the-art membranes for CO2 separation, new polymers, copolymers, block copolymers, blends and nanocomposites (mixed matrix membranes) have been developed [15-22]. However, many of them have failed during application because of different reasons (expensive materials, weak mechanical and chemical stability, etc.). 

Gas permeation systems typically use hollow-fiber or spiral-wound membranes, although hollow-fiber systems are more common tBaker. 2004k Cellulose acetate membranes are used for carbon dioxide recovery, polysulfone coated with silicone rubber is used for hydrogen purification, and conposite membranes are used for air separation. The feed gas is forced into the membrane module under pressure. Retentate, which does not go through the membrane, will become concentrated in the less permeable gas. Retentate exits at a pressure that will be close to the input pressure. The more permeable species will be concentrated in permeate. Permeate, which has passed through the membrane, exits at low pressure. The operating cost for a gas permeator is the cost of conpression of the feed gas and the irreversible pressure difference that occurs for the gas that permeates the membrane. A typical hollow-fiber unit will contain 5000 m membrane area per m at a cost of approximately 200/m. ... 

Since the early 1980s, membrane technology has advanced rapidly and continues to advance. In addition to cellulose acetate and polysulfone, the polymers used in making gas separation membranes include polyimides, polyamides, polyaramid, polydimethylsiloxane, silicon polycarbonate, neoprene, silicone rubber, and others. Today membranes can be designed to withstand a 2,000 psi pressure differential. Membranes used in hydrogen or carbon dioxide applications operate at temperatures up to 200°F, while those used in solvent applications can operate at temperatures up to about 400°F (Baker, 1985). 

Currently, the two most-commonly used polymers for gas separation membranes are polysulfone and cellulose acetate. Polysulfone, for instance, has a separation coefficient a (where a is the ratio of the permeability coefficient of the two gases) of 35 for the hydrogen/methane system and has a hydrogen permeability of 4.3 molrn s Pa Much research is currently being undertaken to develop other polymers which will exhibit higher selectivities and fluxes. 

The gas separation membrane was first commercialized in 1980 in order to recover hydrogen gas produced in the oil refining process. This membrane was a hollow-fiber membrane comprised of polysulfone. The shell of the hollow fiber exhibited an asymmetric cross-sectional structure, which showed the porous structure with pore size varying from one surface to the other surface of the membrane. The asymmetric structure is most preferred for the gas separation membranes due to several reasons described later. A certain number of the hollow-fiber membranes were integrated into a bundle, and the bundle of the hollow-fiber membrane was installed into the piping unit (module) and shipped to the user. 

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