Effect of Hydrogen Spillover on the Ru/TiO2-Catalyzed Guaiacol Hydrodeoxygenation: Rutile vs Anatase TiO2

Abstract

The crystal phase of a catalyst support, such as TiO2, significantly contributes to the activity and stability of metal-loaded catalysts by modifying the metal-support interactions. However, the effect of the crystal phase on hydrogen spillover-induced hydrodeoxygenation (HDO) is relatively less understood, although the spillover of hydrogen on the reducible oxide support could play a crucial role in HDO by providing additional active sites. The HDO of guaiacol by hydrogen spillover was investigated by confirming the synergetic effect when pristine rutile and anatase TiO2 were added to Ru-loaded TiO2, while hydrogen spillover-induced promotion of guaiacol HDO performance was more pronounced for rutile TiO2 than for anatase TiO2. Facilitated hydrogen spillover on rutile TiO2 was confirmed by combined hydrogen temperature-programed reduction, hydrogen chemisorption, and hydrogen diffuse reflectance infrared Fourier transform analysis. The distinctive adsorption behaviors of the reactants on rutile and anatase TiO2 were evaluated by using attenuated total reflectance infrared spectroscopy, which demonstrated that the adsorption behavior was also responsible for the spillover-induced promotion of the HDO performance. This study facilitates the understanding of the distinctive features of spillover hydrogen affecting HDO according to the phase of TiO2, which can provide guidelines for designing catalysts with enhanced HDO performance.