Synthesis of Metal Oxide Catalysts Composed of Low Valence Titanium and Foreign Elements

Abstract

For titanium suboxides such as Ti₂O₃, Ti³⁺ on the particle surface is facilely oxidized to Ti⁴⁺ by exposure to air. When Ti³⁺ inside the particle as well as on the surface is oxidized, the entire structure of the particle transforms into TiO₂. In this study, in order to suppress the oxidation inside the particles and the resulting structural change, the effect of incorporating foreign metals that are tolerant to oxidation into Ti₂O₃ was investigated. Ti₂O₃ incorporating foreign metals was synthesized by the reduction of TiO₂ incorporating the foreign metals with TiH₂. In this way, Ti₂O₃ samples incorporating 5 mol% Al, V, and Cr were successfully obtained. The incorporation of these foreign metals significantly increased the onset temperature for oxidation of Ti₂O₃, demonstrating the effect of suppressing the oxidation by the incorporation of foreign metals. The incorporation of foreign metals was also effective in improving the catalytic activity and stability of Ti₂O₃ in the reverse water–gas shift (RWGS) reaction.