Metal carbides supports

To further increase the gravimetric catalytic activity of a catalyst with metal carbides support, Esposito and Chen investigated a new approach where Pt can be deposited in atomic monolayer fashion [62]. 

Hence, based on our studies and those reported in literature, it is clear that metal carbides play a dual role on one hand, they act as a sink for oxides species generated on the surface of Pt leading to less peroxide formation and subsequently enhanced ORR activity. On the other hand, they can slow down the movement of Pt particles leading to less agglomeration as metal carbides have the tendency to form oxide layer that enhances interaction between support and Pt. Also, due to oxocarbide and/or oxide layers, metal carbides supports can protect carbon from severe corrosion, especially during high potential excursion of cathode in the startup and anode starvation in PEMFCs. 

Fixed-Bed Vapor-Phase Oxidation of Naphthalene. A sihca gel or sihcon carbide support is used for catalyst involved in the oxidation of naphthalene. The typical naphthalene oxidation catalyst is a mixture of vanadium oxide and alkali metal sulfate on the siUca support. Some changes, such as the introduction of feed vaporizers, are needed to handle a naphthalene feed (14), but otherwise the equipment is the same. 

The application of ly transition metal carbides as effective substitutes for the more expensive noble metals in a variety of reactions has hem demonstrated in several studies [ 1 -2]. Conventional pr aration route via high temperature (>1200K) oxide carburization using methane is, however, poorly understood. This study deals with the synthesis of supported tungsten carbide nanoparticles via the relatively low-tempoatine propane carburization of the precursor metal sulphide, hi order to optimize the carbide catalyst propertira at the molecular level, we have undertaken a detailed examination of hotii solid-state carburization conditions and gas phase kinetics so as to understand the connectivity between plmse kinetic parametera and catalytically-important intrinsic attributes of the nanoparticle catalyst system. 

Most forms of carbon, except diamond, which are renowned as supports for precious metal catalysts in certain applications [3], interact strongly with MW [4]. Amorphous carbon and graphite, in their powdered form, irradiated at 2.45 GHz, rapidly (within 1 min) reach very high temperatures (>1300 K). This property has been used to explain MW-assisted syntheses of inorganic solids [5], In these syntheses carbon is either a secondary susceptor which assists the initial heating but does not react with other reactants, or is one of the reactants, e. g. in the synthesis of metal carbides. MW-carbon coupling has also been widely developed ... 

Leclercq, L., Almazouari, A., Dufour, M., and Leclercq, G. 1996. Carbide-oxide interactions in bulk and supported tungsten carbide catalysts for alcohol synthesis. In Chemistry of transition metal carbides and nitrides, ed. S. T. Oyama, 345-61. Glasgow Blackie. 

The possibility of hydrogen activation on the surface of transition metal carbides has been supported by experiments in which WC was used as a promoter for the hydrogen oxidation reaction over the oxide catalyst V205.1 WC additions to V2O5 were shown to critically accelerate the reaction of H2 + 02 (so that under the same conditions the activities of V205 and WC were separately much lower). Moreover, WC additions to V205 boosted the reduction of vanadium oxide by hydrogen. Qualitatively,... 

Interest in the use of metal carbides and nitrides in hydrotreating was aroused by a publication by Schlatter et al. (182) in 1988. They reported that M02C and M02N (unsupported as well as supported on AI2O3) were highly active for HDN of quinoline in autoclaves under industrially realistic... 

In heterogeneous catalysis, the first tests on UPD were performed on bulk catalysts which allows, for the preparation of the bimetallic catalyst, easy control of the electrochemical potential by an external device (potentiostat). In the same way all electrochemical techniques, particularly the control of catalyst potential required for submonolayer deposition, can be extrapolated to metallic catalysts supported on conductive materials such as carbon or carbides [8]. 

The [TPPFeCl] -NaBITi system in diglyme has been shown to perform remarkably efficiently as a catalyst for the reduction of nitrobenzenes to anilines. Although both TPPCo and TPPMnCl also catalyze the reduction of p-chloronitrobenzene to jo-chloroaniline, their catalytic activities are much lower thanthatofTPPFeCl. Anothertype of reduction catalyst, in this case of dioxygen to water, begins with carbon-supported chloroiron(ni) tetramethoxyphenylporphyrin, which is then heat-treated at 900 °C for one h." This causes decomposition of the porphyrin to produce metallic, carbidic and oxidic iron, as detected by Mossbauer spectroscopy. The active... 

Several studies (7,8) have indicated that the propensity of transition metals for catalysing coke formation increases with decreasing stability of the metal carbide - ie increasing propensity along the series Ti < Cr < Fe < Ni. However, the examination of the ESC radiant coil revealed only low levels of nickel in the surface oxide and more particularly virtually no nickel in the coke samples. Therefore, iron and possibly chromium, which are both present at the cracker coil surface and within the coke, are more likely to be responsible for catalysed coke formation. This is supported by research of Albright and coworkers (5) on the pyrolysis of hydrocarbons over Incoloy 800 surfaces, which found iron to be the predominant metal in the coke. 

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