Structural and textural study of Ni and/or Co in a common molybdate lattice as catalysts

This work deals with the search for new molybdate catalyst formulations, which are known to be active in light alkane oxidative dehydrogenation, a process which could be replace in the near future the common steam cracking and pure dehydrogenation processes currently used for the production of alkenes. Co, Ni and mixed Ni-Co molybdates of various compositions are prepared by a modified coprecipitation procedure from metal nitrates and ammonium heptamolybdate. Their structural and textural properties were studied by XRD, Raman, B.E.T and XPS. Textural and structural properties of the materials are correlated to the composition

Deep Characterizations and Rietveld Refinement of Natural Phosphate Mining from Kef Esnoun, Algeria

International audienceThe main physico-chemical properties and the underlying influence of thermal treatment on the phase composition and structural characteristics of the natural phosphate Kef Esnoun region in Djebel Onk, Algeria, are discussed in this work. The primary goal is to increase the natural phosphate value as an alternative material in heterogeneous catalysis. The phase evolution during the heat treatment of the natural phosphate was carried out at different temperatures ranging from 600 to 1000 °C. Several complementary analytical methods were used for their characterization before and after thermal treatments. The obtained results by X-Ray Diffraction supplemented by the Rietveld method and confirmed by molecular spectroscopy have shown that the raw natural phosphate consists primarily of a fluorapatite-type structure (Ca5(PO4)3F). Furthermore, high-temperature X-ray diffraction and thermal analyses have shown that dolomite which is one of the natural phosphate constituents is fully decomposed into CaO and MgO phases after heating at 700 °C. At 900 °C, the phase composition is (Ca5 (PO4)3F; 98.23 %), (MgO; 1.1 %) and (CaO; 0.67 %) with a crystallite size value of approximately 300 nm. Cell parameters increase with calcination temperatures due to the substitution of carbonate with PO4−3 groups

Structure, reactivity and catalytic properties of nanoparticles of nickel ferrite in the dry reforming of methane

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Cobalt and cobalt-iron spinel oxides as bulk and silica supported catalysts in the ethanol combustion reaction

SSCI-VIDE+ATARI+AAUInternational audienceCobalt and mixed iron-cobalt spinel oxides CoxFe(3-x)O4 supported on SiO2 'IMP-Co-x-500' and their bulk analogues 'CP-Co-x-500' were prepared via impregnation and co-precipitation methods respectively and calcined at 500 degrees C. Thermogravimetric analysis 'ATG/DTG', X-ray Diffraction method 'XRD', Texture measurements 'BET/BJH' and Temperature Programmed Reduction technique 'TPR' were used for their characterization. Their catalytic behavior in ethanol combustion was investigated. Results showed that nanostructured oxide materials with spinel structure were obtained with a good dispersion of the active phase at the surface of silica in the case of IMP-Co-x-500 compounds. The reduction behavior of the prepared samples is highly dependent on the oxide composition and interaction with the support; which is directly related to the catalytic behavior. The use of supported catalysts improves the catalytic performance and leads the reaction towards a total oxidation by decreasing greatly the formation of partial oxidation products. The obtained values of activation energies are relatively low in comparison with the literature data. A compensation effect was found by carrying out ethanol combustion through the spinel systems considered in this work. (C) 2016 Elsevier B.V. All rights reserved