Some Physical Properties and Catalytic Activities of Vanadium Oxide (III) : Catalyst

Abstract

Electric conductivities and magnetic susceptibilities of V₂O₃ catalysts containing small amount of MoO₂ or α-Al₂O₃ were measured. The temperature dependencies of these physical properties showed that these catalysts were antiferromagnetic semiconductor. In general, addition of small amount of MoO₂ caused increase of effective magnetic moment (μₑff), descent of the Néel temperature () and decrease of activation energy for electric conduction (). In the case of addition of Al₂O₃, reverse changes of these properties were observed. The rates of p-H₂ conversion with these catalysts were also measured. It was asserted that the controlling step for this conversion was the desorption process of H₂, because the temperature at which this conversion became observable correlated closely with the temperature at which adsorbed H₂ began to be desorbed. Addition of MoO₂ promoted remarkably this conversion rate at low temperature. This promotive action of MoO₂ was explained by reason that the decrease of adsorption heat of H₂ resulted from the decrease of Eσ, that is, the ascent of Fermi level by addition of MoO₂. In the case of V₂O₃-Al₂O₃ catalyst, reverse action was expected from change of its physical properties, but rather slight improvement of activity for p-H₂ conversion was observed. This result was interpreted by the fact that this catalyst was in the slightly oxidized state favorable for this conversion.