Application of Carbon Membranes

The most important application for carbon membranes is in the production of low cost and high pirrity nitrogen from air. Membranes can produce N2 with purity of up to 99.5%. It is estimated that membranes crrrrently produce 30% of all gaseoirs N2 because many irrdustries and commercial apphcations do not reqirire irltra high purity nitrogen [6,22]. It is expected that carbon membranes will offer an effective way of prodncing N2. 

Other separation processes include purification of methane as well as the recovery of carbon dioxide in oil fields [15,23]. Besides that they are useful in the removal of acid gases from rratural gas because they can operate in severe environments [15]. 

Frrrthermore, extremely high partial-pressure of carbon dioxide can cause the plasticization in the skin layer of a membrane [6]. 

Membranes compete with cryogenic, catalytic and pressure swing adsorption processes in the hydrogen recovery process [6], Carbon membranes can be apphed to recover a valnable chemical (H2) from a waste gas, or can be used for the recovery of hydrogen from gasification gas without further compression of the feed gas, while rejecting a snbstantial portion of the hydrocarbons [24], Conventional/poly-meric membranes incur additional recompression costs because H, as a fast gas, exits the unit at the lower pressure side [5, 6], 

Carbon membranes are promising candidates for separating light alkenes/alkanes, especially propene/propane separation, because carbon molecrrlar sieve membranes possess excellent propene/propane permselectivities. 

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The application of carbon membrane reactors for the dehydrogenation of cyclohexane into benzene was investigated by Itoh and Haraya. They found a higher conversion for the carbon membrane reactor comparing to the normal reactor, which was caused by the chemical reaction shifti ng to the product side due to the preferential permeation of H2. Sznejer and Sheintuch studied the dehydrogenation of isobutane to isobutene in a membrane reactor equipped... 

Koresh JE, Soffer A (1983) Molecular sieve carbon permselectivities membrane Parti. Presentation of a new device for gas mixture separation. Sep Sci Technol 18 (8) 723-734 Bauer JM, Elyassini J, Moncorge G, Nodari T, Torino E (1991) New developments and application of carbon membranes. Key Eng Mater 61-62 207-212... 

Gas permeation tests have been carried out for many carbon membranes. However, there is very limited data for the liquid permeation tests, especially for the application of carbon membranes for ultrafiltration (UF) or microfiltration (MF). Some studies [1,2] demonstrated that carbon UF membranes could be made by adding non-carbonizing polymers such as poly(ethylene glycol) (PEG) to the precursor solution. Encouraged by the findings of [3] and [4], Shah and co-woikers successfully made nanoporous carbon UF membranes suitable for bioprocessing applications [5]. 

The most important large application of carbon membrane seems in the production of low cost and high purity nitrogen from air. Other examples are separation of hydrogen from gasification gas, purification of methane [3]. In addition, it is used to recover a valuable chemical (H ) from a waste gas stream without further compression of the feed gas while rejecting a substantial portion of the hydrocarbons [4]. 

A carbon membrane reactor constitutes one of the most promising applications of carbon membranes. The performance of a carbon membrane for gas separation and for the dehydrogenation of cyclohexane to benzene was examined by Itoh and Ha-raya [29], They concluded that the performance of their caibon membrane reactor for dehydrogenation was fairly good compared with that of a normal reactor, i.e. functioning at equilibrium [29], On the other hand, Lapkin [30] used a macro-porous phenolic resin carbon membrane as a contactor for the hydration of propene in a catalytic reactor. He found that the use of this porous contactor-type reactor for his high-pressure catalytic reaction is practical. 

Specific applications of carbon-13 n.m.r. spectroscopy to the glycophorins, an important family of glycoproteins present in the human erythrocyte membrane, are discussed by K. Dill (Clemson), who demonstrates the value of C-n.m.r. spectra for the structural mapping of glycoproteins. 

One of the most important applications of nanoporous membranes is as nanoscaffolds in template synthesis, to replicate the structural features of the nanopores, or patterns, into metals [233], carbons [234], semiconductors [235,236], conductive polymers [237,238], and other materials [239]. The important characteristics of template synthesis have been best reviewed by Martin [188,240]. In short, it is a robust, general method suitable for the... 

Another application of carbon and carbon hybrids is their use as electrode material in proton exchange membrane (PEM) electrochemical flow reactor for the production of hydrogen peroxide (H202). 

Li, Y.Y., Sakoda, A. and Suzuki, M., 2001, A review of fabrication methods of carbon membranes and applications related to their hydrophobic and electrically conductive properties. Journal of Institute of Industrial Science, University of ToIq o, 53(3), 70-74. 

Certainly the most promising application of MFI membranes is in hydrocarbon separations. Adsorption increases with the carbon number for linear compounds and steric effect allows to separate /2-butane from t-butane. Consequently at low temperature the permeance decreases when the carbon number increases and at high temperature, differences in diffusion factors... 

The application of polymer membranes is generally limited to temperatures below 475 K and to the separation of mixtures that are chemically inert. Otherwise, membranes made of inorganic materials can be used. These include mainly microp-orous ceramics, metals, and carbon, and dense metals, such as palladium, that allow the selective diffusion of very small molecules such as hydrogen and helium. 

There are several potential industrial applications for the CMS membranes some which are close to market, others which may be more future applications. This may be a function of both the volume of the gas streams, and/or challenging process conditions. Closest to market is the upgrading of biogas to vehicle fuel and separation of air by the use of carbon membranes. 

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