Tuning the interface of Ru/TiO2 with P for enhancing the hydrodeoxygenation of m-cresol

Abstract

The hydrodeoxygenation (HDO) of biomass by a vapor-phase catalyst plays a crucial role in the development of renewable energy resources. While the catalysts for HDO are not satisfactory in terms of both selectivity and stability. The poor stability is due to the need for acid centers that can cause carbon deposition. TiO₂ modified with P was used as a support to improve the selectivity and stability. It was found that the content of surface acid on the catalysts exhibited a volcano-shaped curve in relation to increasing P content. The conversion of m-cresol over 5%Ru/TiO₂–3.5%P is up to 60%, while the conversion of m-cresol over 5%Ru/TiO₂ is only 0.3% under the same conditions. In addition, the activity over 5%Ru/TiO₂–3.5%P remains stable over 100 hours due to the presence of a suitable acid center, which is not observed over other supports, such as Nb₂O₅, Al₂O₃, TiO₂, CeO₂, and so on. As revealed by CO-TPD, TEM and XPS, the encapsulation of Ru by TiO₂ was eliminated after the TiO₂ was modified with P. It was demonstrated by changing the order of catalyst modification and the way of catalyst reduction that the introduction of Brønsted acid on the catalysts improves the selectivity for toluene, and the increase of catalytic activity is caused by more exposed Ru sites and the introduction of Brønsted acid. The findings of this study may provide a new approach to the appropriate control of the metal and support interface.