Showing papers by "Frank S. Stone published in 1979"
TL;DR: In this article, the decomposition of isopropanol is studied over well-outgassed MgO and CoxMg1 − xO as catalysts in the temperature range from 180 to 250 °C.
13 citations
TL;DR: In this article, a model involving displacement of anions in particular directions when large Ca2+ ions are substituted for small Mn2+ ion in the partially covalent MnO structure was proposed.
Abstract: CaO–MnO samples have been prepared by thermal decomposition of mixed carbonates and annealing of the resulting oxide mixtures at 1273 and 1523 K in vacuo. Cooled samples have been ground in vacuo and transferred for X-ray powder diffraction analysis and e.p.r. analysis without exposure to the atmosphere. Lattice parameter measurements confirm the presence of a single phase of rock–salt structure (CaII1–xMnIIxO) across the whole composition range.A deviation from ideality in respect of the volume change of the unit cell is observed for the solution of CaO in MnO. The deviation passes through a maximum near 35 mol % CaO. The result is interpreted in terms of a model involving the displacement of anions in particular directions when large Ca2+ ions are substituted for small Mn2+ ions in the partially covalent MnO structure. No deviation from ideality is observed for the solution of initial amounts of MnO in CaO. E.p.r. analysis of solid solutions very dilute in MnO (0.01%, 0.1% Mn) confirms substitutional replacement of Ca2+ by Mn2+.
11 citations
TL;DR: In this article, a combination of X-ray diffraction, electron diffraction and magnetic susceptibility studies for their bulk properties and by UV-visible reflectance spectroscopy and adsorption for surface properties is presented.
Abstract: NiO-MgO and CoO-MgO catalysts (1 to 10 mole % NiO or CoO) have been prepared in high surface area form (40 to 300 m 2 g ‐1 ) by impregnation of Mg(OH) 2 with Ni or Co nitrate, followed by thermal decomposition and annealing in vacuo at 1000°C. The resulting solids have been characterized by a combination of X-ray diffraction, electron diffraction and magnetic susceptibility studies for their bulk properties and by UV-visible reflectance spectroscopy and adsorption for surface properties. Lattice parameters, magnetic moments and Weiss constant values, all determined after high temperature outgassing and without exposure to the atmosphere, are fully consistent with the vacuum-annealed catalysts being true substitutional solid solutions Ni x Mg 1-x O and Co x Mg 1-x O, with Ni 2+ and Co 2+ in octahedral coordination. Reflectance studies, however, reveal the presence of Ni and Co ions in other coordinations, notably Co 2+ in tetrahedral coordination in Co x Mg 1-x O, and these ions are considered to be located in the surface regions of the crystallites. The effects of adsorbing O 2 , CO 2 and H 2 O vapour on Ni x Mg 1-x O and Co x Mg 1-x O are described and discussed. A calorimetric study of the adsorption of NO and CO and their chemical interaction on Ni x Mg 1-x O is also reported.
10 citations