Browsing by Author "Delafosse, Denise"

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    Comparative study of the hydrogen reduction of Ni2+ ions in X- and Y-zeolites
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (06), 1978) Briend-Faure, Marguerite; Jeanjean, Janine; Kermarec, Maggy; Delafosse, Denise
    The kinetics of the hydrogen reduction of Ni2+ ions in X- and Y-molecular sieves has been studied over a wide range of temperatures. The localization of Ni2+ ions before and after their reduction has been determined from X-ray analysis. Ni2+ ions can be more easily reduced in X- than in Y-frameworks. In Y-zeolites, it is shown that the reduction of Ni2+ ions depends on the initial localization of these cations and the reduction of Ni2+ ions located on sites I requires a high activation energy. In X-zeolites the sites appear to be energetically homogeneous and the reduction of Ni2+ ions on sites I, I′ and II occurs simultaneously.
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    Kinetics of the hydrogen reduction of nickel ions in silica–magnesia
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (06), 1977) Briend-Faure, Marguerite; Delafosse, Denise
    The H2 reduction of Ni2+-substituted silica–magnesia gel was studied in the ranges 613–753 K and 1.3–13 kN m–2. The reaction is slow and requires an activation energy of 174 ± 20 kJ mol–1. The rate varies with the hydrogen pressure up to 6.5 kN m–2. The reduction is not complete under the experimental conditions. The mechanism of the overall reaction appears to comprise a nucleation process together with the migration of Ni2+ ions and desorption of the water formed.