Influence of sodium on the physico-chemical and catalytic properties of magnesium oxide

Abstract

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 (11) series of catalysts was obtained by evaporating metallic sodium onto MgO preparations precalcined 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-1-ene, tram-pent-2-ene and the conversion of cumene was studied. It was concluded that the (11) 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.

Synthesis and characterization of potassium-modified alumina superbases

“…Kijenski and Malinowski prepared NaÈMgO with a base strength of by evaporating metallic sodium H ~\ ]35 onto MgO and this catalyst exhibited a high activity for the isomerization of pent-1-ene. 3 isomerization of 5-vinvinylbicyclo-(2,2,1)-hept-2-ene (VNB) to 5-ethylidenebicyclo-(2,2,1)-hept-2-ene (ENB) with very high conversion and selectivity. 4 Loading potassium onto alumina in liquid ammonia and heating the resulting material under vacuum at 250È300 ¡C, Baba et al obtained a superbase K that is very active for isomerization of (NH 3 )/Al 2 O 3 alkenes.5,6 However, the complex and time-consuming preparation process would be inconvenient for industrial use, therefore novel preparation methods must be developed.…”

Surface Color Centers on Calcium Oxide: An Electron Paramagnetic Resonance Investigation

“…By this method the activated oxide is exposed to the vapors of low ionization energy metals; the metal atoms become ionized upon contact with the ionic surface and both the metal cations that are formed and the released electrons are subsequently stabilized by the ionic matrix. Unlike the case of radiatively colored materials, the surface F centers generated by additive coloring were only sparingly investigated in the past . Therefore systems prepared by doping an alkaline-earth oxide with alkali metal vapors has been actively pursued in our laboratories over the past few years in order to provide a better description on the spectroscopic and chemical properties of these previously poorly understood surface color centres. − …”

Modified main groups metal oxides as potential active fillers for polymers

“…The reaction pathway proposed by the authors of [30] leads to a decrease in the cation coordination of magnesium (in the vicinity of anion vacancies) which in addition leads to a decrease in the coordination number of oxygen atoms.…”