Browsing by Author "Jacobs, Peter A"

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    Redox Behaviour of Transition Metal Ions in Zeolites Part 5.—Method of Quantitative Determination of Bidisperse Distributions of Metal Particle Sizes in Zeolites
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (11), 1977) Jacobs, Peter A; Linart, Jean Philippe; Nus, Hubert; UYTTERHOEVEN, JAN B
    Temperature programmed reduction and oxidation techniques were used as a fast and quantitative method to determine the amount transition metal inside or outside the zeolite after a reductive treatment. The method has been applied to Ag, Cu and Ni and to different zeolites—X, Y, Z and L. For Ag and Cu zeolites it was found that small metal particles located in the zeolite cages show a low temperature maximum in the rate of oxidation. The maximum in the rate of reoxidation of the metal phase outside the zeolite is found at distinctly higher temperatures. For Ni zeolites, the determination of the bidisperse metal distribution requires first a complete reoxidation of the sample. During a subsequent reduction, two metal dispersions can be distinguished on the basis of maxima observed in the rate of reduction.
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    Redox Behaviour of Transition Metal Ions in Zeolites Part 6.—Reversibility of the Reduction Reaction in Silver Zeolites
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (11), 1977) Jacobs, Peter A; Uytterhoeven, Jan B; Beyer, Hermann K
    In this paper is shown that hydrogen is formed by oxidative thermal desorption from Y-zeolite or mordenite containing highly dispersed silver metal in the cages. Upon thermal degassing above 573 K, hydrogen is desorbed from previously reduced Ag zeolites. At the same time, silver metal is reoxidized and located as Ag+ ions in lattice positions and lattice hydroxyl groups disappear. The following methods are used to characterize the system; isothermal and temperature programmed consumption or desorption of hydrogen in a volumetric system; i.r. spectroscopy of the hydroxyl region; i.r. spectroscopy of adsorbed carbon monoxide and pyridine; X-ray diffraction of Ag0 crystallites.