The Effect of MoOx Reducibility on its Activity for Anisole Hydrodeoxygenation
Abstract
Catalytic hydrodeoxygenation (HDO) is a process for upgrading crude bio-oil as it has a high oxygen content which causes several undesirable properties. Current methods for HDO use sulfided NiMo and CoMo or supported noble metal catalysts which hydrogenate aromatic rings, leading to less valuable products and increasing the hydrogen consumption. Using 10 wt. % MoO3 supported on ZrO2, TiO2, γ-Al2O3, SiO2 and CeO2, we investigated the atmospheric HDO of anisole, a model compound, at 350 °C. All catalysts achieved C – O bond cleavage, preserving the aromatic ring. In situ UV-Vis spectroscopy showed a peak corresponding to intervalence charge transfer (IVCT) transitions where Mo5+ – O – Mo6+ → Mo6+ – O – Mo5+. The IVCT positions were used to classify the catalysts according to their degree of reduction. In general, a direct correlation is established between the supported catalyst’s activity and its ability to preserve Mo5+ sites, preventing over-reduction to less active Mo4+ sites.