Elsevier

Journal of Catalysis

Volume 168, Issue 2, June 1997, Pages 315-320
Journal of Catalysis

Regular Article
The Effect of Oxygen-Anion Conductivity of Metal–Oxide Doped Lanthanum Oxide Catalysts on Hydrocarbon Selectivity in the Oxidative Coupling of Methane

https://doi.org/10.1006/jcat.1997.1662Get rights and content

Abstract

La2O3was doped with cations of valencies different to La3+(Sr2+, Zn2+, Ti4+, Nb5+) to alter the concentration of oxygen–anion vacancies in the host lattice and, hence, oxygen-anion conductivity. The conductivity and catalytic properties of these solids were determined between 700 and 850°C. An increase in oxygen-anion conductivity improved C2+selectivity. A high concentration of anion vacancies in the catalytic material favours the adsorption of gaseous oxygen and its immediate transformation into lattice oxygen; therefrom it is suggested, that the relative amount of weakly adsorbed electrophilic oxygen species (possibly O2O22−) is diminished in favour of more strongly bounded, nucleophilic species (O2−). Thereby, nonselective surface reactions of methyl radicals and/or C2+hydrocarbons with electrophilic oxygen are suppressed.

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1

Present address: Hoechst AG, Central Research, D-65926 Frankfurt, Germany.

2

Present address: Institute for Applied Chemistry Berlin-Adlershof e.V., Rudower Chaussee 5, D-12484 Berlin, Germany. Correspondence author. E-mail: [email protected].

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