Journal Archive Collections

Permanent URI for this communityhttp://localhost:4000/handle/123456789/16937

Browse

Subject: search.filters.subject.Magnesium Oxide

Search Results

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Influence of Sodium on the Physico-chemical and Catalytic Properties of Magnesium Oxide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1978, 74 (02), 1978) Kijenski, Jacek; Malinowski, Stanislaw
    Physico-chemical and catalytic properties of two series of catalysts comprising magnesia and sodium were determined. The first (I) series of catalysts was prepared by doping magnesia with varying amounts of NaOH. The second (II) series of catalysts was obtained by evaporating metallic sodium onto MgO preparations prccalcined at different temperatures. The concentration and strengths of basic and acid sites, as well as the amounts of one-electron donor and one-electron acceptor sites, were measured, and the specific surface areas of the catalysts determined. Catalytic activity in isomerization of pent-l-enc, trans-pcnt-2-cne and the conversion of cumene was studied. It was concluded that the (II) series of catalysts displayed remarkably strong basic and one-electron donor properties. Also, it was proved that basic sites coexist on the surfaces of catalysts with the one-electron donor sites. Catalytic activity in alkene isomerization and cumene dehydrogenation was unambiguously associated with the presence of well-defined surface active sites.
  • No Thumbnail Available
    Item
    Structure and Catalytic Activity of Iron Oxide and Magnesium Oxide Solid Solutions: Part 3- E.S.R. Characterization
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1977, 73 (1), 1977) Cordischi, Dante; Pepe, Franco; Schiavello, Mario
    Magnesium oxide + iron oxide, fired both in air and in a reducing atmosphere, and magnesium oxide + iron oxide + lithium oxide (up to 1 % atomic Fe) were investigated by e.s.r. spectroscopy. The effects of outgassing at various temperatures and of N2O decomposition on the e.s.r. spectra are discussed in terms of surface redox processes. The incipient formation of the spinel phase, MgeFe2O4, and its precipitation, at the highest outgassing temperatures adopted, were readily studied by the e.s.r. technique. The hypotheses previously proposed on the modification of the catalyst solid state, occurring during N2O decomposition and/or in the vacuum treatment, are confirmed by the present study. Further details are also given.
  • No Thumbnail Available
    Item
    Electron Donor Sites on the Surface of Magnesium Oxide Powder studied by Electron Spin Resonance Spectroscopy
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (12), 1974) Cordischi, D.; Indovina, V.; Cimino, A.
    The electron donor properties of MgO powders, activated in vacuo in the temperature range 300–1200 K have been investigated by adsorption of nitrobenzene and some of its para substituted derivatives. The results confirm that the donor properties of MgO are an intrinsic property of the surface, being practically independent of impurity. Two types of nitrobenzene radical were detected: the first one, formed on low temperature activated samples (<1200 K), is the nitrobenzene radical anion interacting with surface protons; the second one, observed on high temperature (1200 K) activated MgO, is the “free” radical anion. No correlation between electron affinity of the adsorbed molecules and radical surface concentration was found. The proton affinity of the anion radical has to be taken into account to rationalize the results. A model of the electron donor surface site consisting of a dual site (O2–cus, OH–) is presented. The effect of adding Ni2+ ions in solid solution has also been examined.
  • No Thumbnail Available
    Item
    Infra-red Study of the Reactions between Ethyl Isocyanate and the Surface of Magnesium Oxide
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1974, 70 (1-6), 1974) Eley, Daniel D.; Kiwanuka, Gerald M.; Rochester, Colin H.
    Ethyl isocyanate reacts at 306 K with isolated hydroxyl groups on the surface of magnesium oxide to form a urethane. The adsorption reaction is reversed by evacuation at high temperatures. Adjacent interacting hydroxyl groups and molecular water on magnesium oxide react with ethyl isocyanate to give 1,3-diethylurea which is adsorbed on the oxide as a perturbed “carboxylate-type complex” and carbon dioxide which with water gives a surface bicarbonate species. The 1,3-diethylurea complex decomposes to surface ethyl magnesium carbonate on evacuation at elevated temperatures. The latter species is also formed when ethyl isocyanate reacts with the surface of magnesium oxide at 673 K. Other products of the high temperature reaction include cyanide and isocyanate groups as ligands of surface magnesium ions, adsorbed carbonate ions, and products of the polymerization reactions of ethyl isocyanate, isocyanic acid, and hydrogen cyanide.