Study by electrical conductivity measurements of semiconductive and redox properties of M-doped NiO (M = Li, Mg, Al, Ga, Ti, Nb) catalysts for the oxidative dehydrogenation of ethane
Abstract
Pure and M-doped nickel oxides with M = Li, Mg, Al, Ga, Ti, Nb, catalysts for the oxidative dehydrogenation of ethane into ethylene, were characterized by in situ electrical conductivity measurements. Their electrical conductivity was studied as a function of temperature and oxygen partial pressure and was followed with time during sequential exposures to air, an ethane–air mixture (reaction mixture) and pure ethane under conditions similar to those of catalysis. All the materials appeared to be p-type semiconductors under air with positive holes as the main charge carriers and their electrical conductivity decreased in the following order: Li–NiO > NiO > Mg–NiO > Nb–NiO > Ga–NiO > Al–NiO > Ti–NiO. All the catalysts remained p-type semiconductors in the reaction mixture at 400 °C. Correlations between the p-type semiconductivity and the catalytic properties have been evidenced. The reaction mechanism involves surface lattice O− species and can be assimilated to a Mars and van Krevelen mechanism.
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