Nanostructured Ru(2 wt%)/PrxCe1_ xO2-d (x=0, 0.12 and 0.25) materials for hydrodeoxygenation of guaiacol: Influence of oxygen vacancies on reactivity

To assess the influence of catalyst morphology and dopant on catalytic activity for the hydrodeoxygenation (HDO) of guaiacol, four Ru catalysts-Ru(2 wt%)/CeO2 irregular nanoparticles (Ru-1), Ru(2 wt%)/CeO2 nanocubes (Ru-2), Ru(2 wt%)/Ce0.88Pr0.12O2-& delta; nanocubes (Ru-3) and Ru(2 wt%)/Ce0.75Pr0.25O2-& delta; nanocubes (Ru-4) were prepared and characterized using transmission electron microscopy, X-ray diffraction analysis, Raman spectroscopy, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy, and volumetric oxygen titration. The shape-dependent catalytic activities for the HDO of guaiacol over Ru-1 and Ru2 were initially determined, presenting that Ru-2 exhibited higher activity than Ru-1. In addition, the effect of Pr doping into CeO2 on the desired activity was examined using Ru-2, Ru-3 and Ru-4, demonstrating that there is an optimal Pr content that maximizes the activity. The results obtained by the analytical methods with additional oxygen vacancy titration indicate that the activities of the catalysts are strongly correlated with the normalized oxygen vacancy densities.