Oxidation carbon nanofiber

Fig. 1(b) represents the selectivity to styrene as a ftmcfion of time fijr the above catal ts. It is observed that the selectivity to styrene is more than 95% over carbon nauofiber supported iron oxide catalyst compared with about 90% for the oxidized carbon nanofiber. It can be observed that there is an increase in selectivity to styrene and a decrease in selectivity to benzene with time on stream until 40 min. In particrdar, when the carbon nanofiber which has been treated in 4M HCl solution for three days is directly us as support to deposit the iron-precursor, the resulting catalyst shows a significantly lows selectivity to styrene, about 70%, in contrast to more than 95% on the similar catalyst using oxidized carbon nanofiber. The doping of the alkali or alkali metal on Fe/CNF did not improve the steady-state selectivity to styrene, but shortened the time to reach the steady-state selectivity. 

If the oxidized carbon nanofibers are calcined at 573 K, the shoulder at 1740 cm and the band at 1720 cm becomes less pronounced (Fig. 4). The phenolic and asymmetric and S5nnmetric NO2 stretching vibration peaks have disappeared completely. Thus ketone, carboxylic, phenolic and nitro groups decompose if the carbon nanofibers are calcined at 573 K. The peak that remains at 1720 cm" is most likely due to lactones because these groups decompose between 600 and 950 K [31]. If the temperature is increased further to 873 K, the shoulder and peak at 1740 cm" and 1720 cm" have disappeared completely. It follows that the majority of the surface oxygen functional groups decompose at 573 K. 

Table 2 XPS study of the heat treatment of the oxidized carbon nanofibers...

Fig. 6. Variation of Zeta potential of unoxidized and oxidized carbon nanofibers and oxidized carbon nanofibers loaded with cobalt (no heat treatment).

Fig. 8. TEM images of the oxidized carbon nanofibers supported cobalt catalysts, a. calcined at 573 K (xl30 000). b. Calcined at 873 K (x43 000).

Difference curves from the TGA data were determined by subtracting the differential curve for the oxidized carbon nanofibers from that for the carbon nanofibers supported cobalt catalysts. The TGA differenee eurve for the carbon nanofiber supported catalysts (Fig. 10) suggests the formation of CoO at 570 K [38]. The latter is stable in air at ambient temperatures and above 1173 K. As already mentioned transfer of oxygen atoms by the eobalt oxide species to the support and the consequent oxidation of the support most probably explains the peak at 880 K. ... 

Figure 8.1 Appearance of carbon nanoflber (CNF) and oxidized carbon nanofiber (ox-CNF) dispersions in methylene-iso-butyrate (MIB). MIB is a low-viscosity liquid at room temperature and the dispersions were prepared by shaking by hand.

Figure 8.4 Relationship between soft segment crystallinity and the extent of non-covalent filler-matrix interactions in shape memory polyurethane (SMPU) composites filled with organoclay, carbon nanofIber (CNF), oxidized carbon nanofiber (ox-CNF), silicon carbide (SiC), and carbon black (CB). The ratio A/Ai. determined from fluorescence emission spectroscopy experiments, is a measure of the...

Jimenez, G. and Jana, S.C. (2007) Polymer composites of oxidized carbon nanofibers prepared by chaotic mixing. Onbon, 45, 2079. 

Surface Oxidation of Carbon Nanofibers Prior to Functionalization... 

Effect of oxidative treatments on catalytic property of carbon nanofiber composite... 

Dehydrogenation of ethylbenzene with carbon nanofiber supported iron oxide... 

Sonoelectrochemistry has also been used for the efficient employment of porous electrodes, such as carbon nanofiber-ceramic composites electrodes in the reduction of colloidal hydrous iron oxide [59], In this kind of systems, the electrode reactions proceed with slow rate or require several collisions between reactant and electrode surface. Mass transport to and into the porous electrode is enhanced and extremely fast at only modest ultrasound intensity. This same approach was checked in the hydrogen peroxide sonoelectrosynthesis using RVC three-dimensional electrodes [58]. 

Bezemer, G. L., Radstake, P. B., Falke, U., Oosterbeek, H., Kuipers, H. P. C. E., van Dillen, A., and de Jong, K. P. 2006. Investigation of promoter effects of manganese oxide on carbon nanofiber-supported cobalt catalysts for Fischer-Tropsch synthesis. Journal of Catalysis 237 152-61. 

The advantage of template synthesis is that organo or hydrogelator templates can direct the shape-controlled synthesis of oxide nanotubes. Recent reports describe the use of carbon nanofibers as a template for the shape-controlled synthesis of zirconia, alumina and silica nanotubes [78]. The shape of vapor grown carbon nanofiber... 

The aim of this review paper is to give an extensive overview of the different promoters used to develop new or improved Co-based F-T catalysts. Special attention is directed towards a more fundamental understanding of the effect of the different promoter elements on the catalytically active Co particles. Due to the extensive open and patent literature, we have mainly included research publications of the last two decades in our review paper.In addition, we will limit ourselves to catalyst formulations composed of oxide supports, excluding the use of other interesting and promising support materials, such as, e.g., carbon nanofibers studied by the group of de Jong. ... 

The 0-d nanoparticles can be nano-metal oxides (such as silica,1 titania,2 alumina3), nano-metal carbide,4 and polyhedral oligomeric silsesquioxanes (POSS),5 to name just a few the 1-d nanofibers can be carbon nanofiber,6 and carbon nanotubes (CNT),7 which could be single-wall CNTs (SWCNT) or multiwall CNTs (MWCNT) etc. the 2-d nano-layers include, but are not limited to, layered silicates,8 layered double hydroxides (LDH),9 layered zirconium phosphate,10 and layered titanates,11 etc. 3-d nano-networks are rarely used and thus examples are not provided here. 

Abstract. Nanocarbon materials and method of their production, developed by TMSpetsmash Ltd. (Kyiv, Ukraine), are reviewed. Multiwall carbon nanotubes with surface area 200-500 m2/g are produced in industrial scale with use of CVD method. Ethylene is used as a source of carbon and Fe-Mo-Al- mixed oxides as catalysts. Fumed silica is used as a pseudo-liquid diluent in order to decrease aggregation of nanotubes and bulk density of the products. Porous carbon nanofibers with surface area near 300-500 m2/g are produced from acetylene with use of (Fe, Co, Sn)/C/Al203-Si02 catalysts prepared mechanochemically. High surface area microporous nanocarbon materials were prepared by activation of carbon nanofibers. Effective surface area of these nanomaterials reaches 4000-6000 m2/g (by argon desorption method). Such materials are prospective for electrochemical applications. Methods of catalysts synthesis for CVD of nanocarbon materials and mechanisms of catalytic CVD are discussed. 

Rekoske and Barteau (68) used TEOM in scaling-up to higher pressure surface-science results dealing with solid reactions related to redox cycles. These authors investigated reduction kinetics and reaction on titanium oxide (69,70). Recent applications also include the investigation of carbon nanofibers (9) and hydrogen adsorption properties of single-walled carbon nanotubes (71). 

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