Graphite catalytic effect

The catalytic effect of graphite A thus depends on iron impurities, e. g. Fe304, and probably also on iron sulfides or sulfates, because sulfur is also present in this graphite, and all these iron compounds are known catalysts of FC acylation [69, 73, 74], In this respect, it seems that FeCl3 could be the true catalyst generated in situ by the reaction of the different iron compounds with acid chloride and hydrogen chloride. In the... 

The retentive power of graphite towards adipic acid and the catalytic effect of the magnetite, especially present in A, are obvious. TEM examinations of a graphite A sample before and after reaction showed that crystallites of Fe304 appeared to be smaller after the reaction. However, the same graphite sample was reused for three successive reactions without significant loss in yield. When applied to the synthesis of other cyclic ketones (Scheme 7.14), less volatile than 74, it was observed that pressure had an effect on the recovery of product (Tab. 7.9, entries 3 and 4). A slightly reduced pressure (300 mm Hg) was necessary to obtain 3-methylcyclopentanone (75) or cyclohexanone (76) in convenient yield (Tab. 7.9, entries 4 and 5). For the cycliza-tion of suberic acid (73), a less favorable structure, the yield in cycloheptanone (77) remained low (Tab. 7.9, entry 6). 

Transparent samples do not absorb the radiative energy properly. For this reason, several procedures were utilized to make the sample more opaque. One such procedure consists of adding into the sample powdered graphite [21a] or a metal such as nickel [22], This addition can, however, modify the course of the pyrolysis by catalytic effects or side reactions. A different procedure consists of depositing the sample in a very thin layer on a support that absorbs the radiation generating heat. In particular, a blue cobalt-glass rod has been used [22] as a support for the sample, with temperatures attaining 900-1200° C. 

Nickel is one of the few materials possessing a close lattice match with diamond. However, its high carbon solubility and strong catalytic effect on hydrocarbon decomposition may be the reason that graphite layers develop on Ni substrates under the typical diamond CVD conditions. This effect impedes the direct nucleation of diamond on Ni substrates and excludes the eventual development of an orientational relationship between the diamond films and the Ni substrates, although diamond may eventually nucleate and grow on the graphite interlayers. 

Among Fe, Cu, Ti, Ni, Mo andNb, Fe shows the best catalytic effect on diamond nucleation. Pd has also a positive catalytic effect on diamond nucleation, while Co suppresses diamond nucleation by promoting soot formation. The strong reactivity of these metals with carbon, the formation of metal carbides, the supersaturation of carbon in/on the metals and/or the deformation of graphite sheets by metal atoms to form diamond structure have been proposed as possible mechanisms governing the catalytic effects. 

Heintz, E.A. and Parker, W.E., Catalytic effect of major impurities on graphite oxidation, Carbon 4, 473-82 (1966). 

The retentive power of graphite towards adipic acid and the catalytic effect of the magnetite, especially present in A, are obvious. TEM examination of a graphite A before and after reaction showed that crystallites of Fe304 seemed to be smaller... 

Put] found that mixed carbide (Fe,Mn)7C3 exhibit catalytic effect on transformation of graphite to diamond at 6 GPa and 1427°C. 

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