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Temperature-programmed reduction of Al2O3-, SiO2-, and carbon-supported Re2O7 catalysts

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PII: 0021-9517(85)90171-X JOURNAL OF CATALYSIS 93, 231-245 (1985) Temperature-Programmed Reduction of A1203-, Si02-, and Carbon-Supported Re207 Catalysts P. ARNOLDY,’ E. M. VAN OERS,* 0. S. L. BRUINSMA, V. H. J. DE BEER,* AND J. A. MOULIJN Institute for Chemical Technology, University of Amsterdam, Plantage Muidergracht 30, 1018 TV Amsterdam, The Netherlands, and *Laboratory for Inorganic Chemistry and Catalysis, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands Received March 9, 1984; revised June 11, 1984 Temperature-Programmed Reduction (TPR) has been applied to characterize the reducibility of A1203-, Sol-, and carbon-supported RezOT catalysts, over a wide range of transition metal content. Dried catalysts are found to contain a so-called monolayer-type Re” surface phase as well as crystalline NH,,Re04. Calcination at 575 or 825 K resulted in decomposition of NH4Re0,, forma- tion of the Re’+ surface phase and Re20, clusters, and Re loss via sublimation of ReZ07. Differences in reducibility of the various catalyst samples are ascribed to variations in the strength and the heterogeneity of the Re7+-support interaction. The strength of the interaction was found to depend on the support material applied and decreased in the order: A1203 > SiOZ > carbon. The heteroge- neity was essentially the same for all three supports. The largely varying literature data on the reducibility of ReZ07/A1203 catalysts is supposedly related with the presence of additives, such as chlorides, which may increase the Re’+-support interaction. o 1985 Academic PWSS, hc INTRODUCTION Rhenium catalysts have several interest- ing properties. They show high activity for metathesis (1, 2), hydrodesulfurization (HDS) (3-6), and hydrodenitrogenation (7), in comparison with MO and W cata- lysts. Re also increases the stability of Pt reforming catalysts (8-11) and, for a large range of organic syntheses, Re appears to be a selective hydrogenation cat

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