Reductive support effect of titanium suboxides on oxidation state and catalytic performance of TiOx-supported CoOx for hydrodeoxygenation of anisole

In this study, several titanium suboxides containing Ti^3 + (Ti₂O₃, Ti₃O₅, Ti₄O₇, and hydrogenated TiO₂) were synthesized by reducing TiO₂ using TiH₂ or H₂ as reducing agent, and these materials were used as support for CoO_x catalysts. The structure, reduction properties, and catalytic performance of these catalysts for the hydrodeoxygenation (HDO) of anisole were compared, and the effect of the reducing properties of the titanium suboxide support on the oxidation state of CoO_x species and catalytic performance was investigated. Redox reactions occurred between these titanium suboxides and the supported CoO_x species, and as a result, CoO_x was supported in a reduced state. As the proportion of Ti³⁺ in the titanium suboxides increased, the reduction of CoO_x proceeded more progressively, and CoO_x species were reduced to a near metallic state. The progressive reduction of CoO_x increased the catalytic activity of the supported CoO_x for the HDO reaction and also improved the catalytic lifetime. This study demonstrated that titanium suboxides with low mean titanium valence played an indirect role in improving the catalytic performance of the supported CoO_x by promoting the reduction of CoO_x.