Ammoxidation active carbon

Jurewicz K, Babel K., Ziolkowski A., Wachowska H. Ammoxidation of active carbons for improvement of supercapacitor characteristics. Electrochim Acta 2003 48 1491-8. 

Jurewicz K, Babel K., Ziolkowski A., Wachowska H. Ammoxidation of active carbons for improvement of supercapacitor characteristics. Electrochim Acta 2003 48 1491-8. Kierzek K., Frackowiak E., Lota G., Giyglewicz G., Machiukowski J. Electrochemical capacitors based on highly porous carbons prepared by KOH activation Electrochim Acta 2004 49 515-23. 

In addition to toluene higher condensed methyl aromatic compounds and biphenyl derivatives, e. g. 1-methylnaphthaIene (on Cu-Na-mordenite [36]) or p-methylbiphenyl (to / -cyanobiphenyl and terephthalodinitrile [60]) can also be ammoxidized. The ammoxidation route can also be used to insert nitrogen into very highly condensed products, e. g. lignins [61,62], or active carbon [63]. 

A first group of methods starts from already made active carbons subjected to a chemical posttreatment NHj or HCN [29], amination or ammoxidation [30]. A second group starts from raw materials with a high content of nitrogen, such as vinyl pyridine-divinyl benzene copolymer [28,31]. 

More recent studies were carried out with coals (lignite and subbituminous), enriched with nitrogen, before carbonization and activation, by treatment with ammonia and its derivatives, mainly urea [36,37]. The ammoxidation reaction (reaction with an ammonia-air mixture) is another route to obtaining nitrogen-enriched precursors of active carbons from various carbonaceous materials, such as pine wood, peat, lignite, subbituminous coal [38], and cellulose [39]. 

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

In the direct ammoxidation of propane over Fe-zeolite catalysts the product mixture consisted of propene, acrylonitrile (AN), acetonitrile (AcN), and carbon oxides. Traces of methane, ethane, ethene and HCN were also detected with selectivity not exceeding 3%. The catalytic performances of the investigated catalysts are summarized in the Table 1. It must be noted that catalytic activity of MTW and silicalite matrix without iron (Fe concentration is lower than 50 ppm) was negligible. The propane conversion was below 1.5 % and no nitriles were detected. It is clearly seen from the Table 1 that the activity and selectivity of catalysts are influenced not only by the content of iron, but also by the zeolite framework structure. Typically, the Fe-MTW zeolites exhibit higher selectivity to propene (even at higher propane conversion than in the case of Fe-silicalite) and substantially lower selectivity to nitriles (both acrylonitrile and acetonitrile). The Fe-silicalite catalyst exhibits acrylonitrile selectivity 31.5 %, whereas the Fe-MTW catalysts with Fe concentration 1400 and 18900 ppm exhibit, at similar propane conversion, the AN selectivity 19.2 and 15.2 %, respectively. On the other hand, Fe-MTW zeolites exhibit higher AN/AcN ratio in comparison with Fe-silicalite catalyst (see Table 1). Fe-MTW-11500 catalyst reveals rather rare behavior. The concentration of Fe ions in the sample is comparable to Fe-sil-12900 catalyst, as well as... 

The purpose of the present paper is to offer a contribute to the understanding of the mechanisms of these reactions by using an IR spectroscopic method and well-characterized "monolayer" type vanadia-titania (anatase) as the catalyst. We will focus our paper in particular on the following subjects i) the nature of the activation step of the methyl-aromatic hydrocarbon ii) the mechanism of formation of maleic anhydride as a by-product of o-xylene synthesis iii) the main routes of formation of carbon oxides upon methyl-aromatic oxidation and ammoxidation iv) the nature of the first N-containing intermediates in the ammoxidation routes. 

Potential applications of superconducting cuprates in electronics and other technologies are commonly known. These cuprates also exhibit significant catalytic activity. Thus, YBa2Cu307 3 and related cuprates act as catalysts in oxidation or dehydrogenation reactions (Hansen et al. 1988 Halasz 1989 Mizuno et al. 1988). Carbon monoxide and alcohol are readily oxidized over the cuprates. NH3 is oxidized to N2 and H20 on these surfaces. Ammoxidation of toluene to benzonitrile has been found to occur on YBa2Cu307 (Hansen et al. 1990). 

It has been described in patents that ammoxidation catalysts can be activated by treatment with ammonia and/or hydrogen (12) or with carbon monoxide (13). Therefore, both precursors and H reduced catalysts will be considered in this presentation. It will be shown that the performance of the catalysts are related to their characteristics. The adsorbed state of reactants will also be discussed. 

There was a clear upper limit in terms of selectivity-conversion beyond which experimental studies have not advanced for many selective oxidation reactions. These limits have been achieved through detailed catalyst design and reactor optimization. This work shows that active sites on oxidation and ammoxidation catalysts are capable of selectively activating, typically, a C-H bond in a reactant, rather than a similar C-H or C-C bond in the product provided that the bond dissociation enthalpy of the weakest bond in the product is no more than 30-40 kJ mole weaker than the bond dissociation enthalpy of the weakest bond in the reactant. When these limits are exceeded selectivity falls drastically. This work also indicates that primary activation of alkanes is through C-H bonds although the corresponding C-C bonds are much weaker. Cleavage of a C-C bond in the primary activation step leads directly to carbon oxide formation, but this step is less favoured because steric Victors make it difficult for the C-C bonds to be accommodated at the active site. 

Jurewicz, K., K. Babel, R. Pietrzak, S. Delpeux, and H. Wachowska. 2006. Capacitance properties of multi-walled carbon nanotubes modified by activation and ammoxidation. 

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