Bulk Tungsten Carbide as Catalyst in Hydrocarbon Reactions: Association of Selectivity Differences with Surface Composition as Compared to the Selectivity of Pt Series Metals

An investigation of the performances in Fischer-Tropsch reaction of 1wt% M/WC(X) (M = Co, Ru; X = A, B), where A is a tungsten carbide protected by free carbon and B is a clean tungsten carbide, was carried out. Supported catalysts performances were compared to those of the parent tungsten carbides at 473 K and 20 bar. It was found that WC(A) produces mainly hydrocarbons but also 20-40% alcohols, whereas WC(B) activity is only towards linear alkanes. Before catalytic test, a reduction in pure hydrogen allows obtaining Co 0 and Ru 0 dispersed on layers of free carbon covering the WC core for the WC(A), and on a surface free of oxygen for WC(B). Co as Ru dispersions are improved on WC(B) compared to WC(A). A direct consequence is that Co/WC(B) has a better activity than Co/WC(A). Ru-W alloy formation could be responsible of the inobservance of a better activity for Ru/WC(B). On contrary, addition of Ru on WC(A) highly increases the activity and the production of heavy hydrocarbons. This beneficial effect, not observed with cobalt, could be attributed to a better dispersion of ruthenium on a carbon polymeric surface of WC.

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“…9a). This slight consumption is likely due to the removal of oxygen atoms from the passivation layer as water [22].…”

Section: A) H 2 -Tpr Experimentsmentioning

confidence: 99%

Characterization of new Co and Ru on α-WC catalysts for Fischer-Tropsch reaction

Griboval-Constant

Giraudon

Twagishema

et al. 2006

Journal of Molecular Catalysis A: Chemical

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Preparation, activation and catalytic properties in the reactions between 2‐methyl pentane and hydrogen of group VIB metal carbides

Leclercq¹,

Dufour²,

Gharbi³

et al. 1996

Bulletin des Soc Chimique

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Journ6e de Conlacl en Calalyse de la CommunaulB Franpaise de Belgique : "Catalyse par les metaux" le 7 d6cembre 1995, Bruxelles red with an integrator (Spectra Physics 4290). 2-methyl pentane (purissimum gradepurity better than 99.5%) was provided from Fluka. Samples of about 3 g of W precursors were used in preparation and activation experiments and 0.6 g for catalytic tests, WO3 (Fluka, high purity grade 99.9%, BET surface area about 3 m2gm1, mixture of monoclinic and orthorhombic crystallographic phases), MOO3 (Fluka, puriss. grade 99.5%) and Cr203 (Prolabo, rectapur 99%) were used as carbide precursors. ProcedureCarburizations and hydrogen treatments were performed in temperature programmed experiments from room temperature up to temperatures ranging from 600 to 1000°C with a heating rate of 50°C h-. A more precise procedure can be found in ref. 30. From the areas of CH4, H20, CO and CO2 chromatographic peaks the amount of CH4 and 0 consumed in the different steps of carburization and reduction (30) or produced during the hydrogen treatments (31) can be measured.Catalytic experiments were performed after in situ carburization and hydrogen pretreatment in isotherm experiments. The hydrogen and 2-methyl pentane partial pressures were respectively 0.9 and 0.1 atm. X-Ray photoelectron spectroscopy (XPS)X-Ray photoelectron spectra were obtained with an A El ES 200 B Kratos electron spectrometer equipped with an aluminium anode (hv = 1486.6 eV). The anode was operated at 12 kV and 25 mA. CIS arising from in situ contamination (binding energy (B.E.) = 285 20.2 eV) was used as reference for the calculation of binding energies. Before fitting and integrating, the C I S photopeaks were smoothed bya least squares method and the background was linearly --107 -

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Contact reactions of n‐butane and 2‐Methylpentane with well characterized clean metallic, carburized or oxidized tungsten surfaces

Wanner¹,

Hemming²,

Wehrer³

et al. 1996

Bulletin des Soc Chimique

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:Oxygen is known to change drastically the surface states and the catalytic properties of transition metal carbides. In order to better understand the mechanism of the reaction of hydrocarbons with the oxygen modified surfaces, surfaces have been prepared by controlled additions of oxygen on a clean WC carbide. 2-methylpentane and n-butane were reacted on these surfaces. The obtained results have been compared with those observed on metal, oxygen predosed metal, and partially reduced oxide. A on the oxygen modified surfaces. INTRODUCTIONThese last years numerous works dealt

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Bulk Tungsten Carbide as Catalyst in Hydrocarbon Reactions: Association of Selectivity Differences with Surface Composition as Compared to the Selectivity of Pt Series Metals

Cited by 11 publications

References 20 publications

Characterization of new Co and Ru on α-WC catalysts for Fischer-Tropsch reaction

Characterization of new Co and Ru on α-WC catalysts for Fischer-Tropsch reaction

Preparation, activation and catalytic properties in the reactions between 2‐methyl pentane and hydrogen of group VIB metal carbides

Contact reactions of n‐butane and 2‐Methylpentane with well characterized clean metallic, carburized or oxidized tungsten surfaces

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