Active carbon fiber, chemical vapor

Active carbon fiber, chemical vapor deposition of organic compounds, 61-70... 

A wide variety of carbon materials has been used in this study, including multi-wall carbon nanotubes (sample MWNT) chemically activated multi-wall carbon nanotubes (sample A-MWNT)16, commercially available vapor grown carbon nanofibers (sample NF) sample NF after chemical activation with K.OH (sample A-NF) commercially pitch-based carbon fiber from Kureha Company (sample CF) commercially available activated carbons AX-21 from Anderson Carbon Co., Maxsorb from Kansai Coke and Chemicals and commercial activated carbon fibers from Osaka Gas Co. (A20) a series of activated carbons prepared from a Spanish anthracite (samples named K.UA) and Subituminous coal (Samples H) by chemical activation with KOH as described by D. Lozano-Castello et al.17 18 activated carbon monoliths (ACM) prepared from different starting powder activated carbons by using a proprietry polymeric binder from Waterlink Sutcliffe Carbons, following the experimental process described in the previous paper13. 

Kawabuchi, Y et al.. Chemical vapor deposition of heterocyclic compoimds over active carbon fiber to control its porosity and surface function. Langmuir. 1997,13(8), 2314-2317. 

Kawabuchi, Y et al. The modification of pore size in activated carbon fibers by chemical vapor deposition and its effects on molecular sieve selectivity. Carbon. 1998, 36(4), 377-382. 

Chemical Vapor Deposition of Organic Compounds over Active Carbon Fiber To Control Its Porosity and Surface Function... 

Chemical vapor deposition (CVD) of some organic compounds was examined to control the porosity and surface function of active carbon fiber (ACF). In this system, the deposition takes place only on the pore wall of the ACF, when the precursor organic compound and deposition temperature around 700 C were selected carefully. The surface of the ACF was modified by carbon derived from heterocyclic compounds (pyridine, pyrrole, furan and thiophene) through CVD. The moderately activated ACF modified by pyridine, pyrrole and thiophene showed molecular sieving activity, that modified by furan did not. Only fiiran was decomposed at this temperature. Thermal stability is a key factor to get molecular sieving performance after CVD. Pyridine produced amorphous carbon within the pore, which appears to maintain the pyridine ring structure, creates basic sites over the surface of the ACF. Thus catalytic oxidation of SOx over ACF of high surface area was accelerated. 

Pore size and surface functionality of active carbon fiber (ACF) were modified by design by selective chemical vapor deposition (CVD) where the deposition temperature was selected carefully (1). In this system, particular organic compounds, like benzene, are useful due to their thermal stability (2). The pore structure of ACF was another key factor which influences strongly its performance after CVD. The ACF of low activation, which carries micropores in majority, showed molecular... 

Using pitch-based ACFs, Mochida et al. [132] reported 87% conversion at room temperatnre in dry air. Lower conversions were obtained in the presence of water vapor. The anthors found that heat treatment at 1123 K enhanced the activity of the fibers. Such treatment removes oxygen functional groups from the surface of the ACFs the vacant sites created as a result of this treatment were thought to be the active sites for the reaction. On the other hand, the hydrophobic surface obtained after the heat treatment helps to decrease the amount of water adsorbed, which decreases NO conversion in humid air. An interesting point noted by Mochida et al. [131] is that PAN- and pitch-based ACFs exhibited the reverse order of activity for the oxidation of SO2 and NO. Thus, pitch fibers were best for NO oxidation, while PAN fibers were found to be more active for SO2 oxidation. No explanation was provided by the authors for this finding, which certainly reflects the different surface chemical properties of the two fiber types. A detailed kinetic study of this process was presented in a subsequent paper [133], while Guo et al. [134] compared the performances of different carbon fibers (PAN, pitch) and activated carbons. 

Certain pitches can be spun directly into isotropic pitch fibers with only minor devolitization. Carbonized isotropic pitch fibers cannot be graphitized and develop mechanical and thermal properties that are substantially inferior to those produced by other precursors. However, isotropic pitch fibers are very inexpensive and have found commercial applications in areas that do not require the exceptional mechanical and thermal properties of mesophase pitch-based carbon fibers. Isotropic pitch-based carbon fibers are used in filters, brake pads, activated carbons, and as substrates for chemical vapor deposition (23). Table 3 summarizes properties of isotropic pitch-based carbon fibers. 

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