Silver initiated hydrogen spillover on anatase TiO2 creates active sites for selective hydrodeoxygenation of guaiacol

Selective hydrocleavage of aromatic C O bond while preserving the aromatic ring is a desired catalytic process in hydrodeoxygenation (HDO) of biomass derived aromatic oxygenates to high value biochemicals. Guaiacol with typical methoxy and phenolic hydroxyl groups is a representative aromatic di-oxygenates of lignin fragments. Sub-nanometer sized silver, a poor hydrogenation metal catalyst, was found to initiate H 2 dissociation and H spillover onto anatase TiO 2 (TiO 2 -A) surface. The spillover hydrogen enhanced the partial reduction of TiO 2 -A surface at a substantially lowered temperature as compared to the reduction of TiO 2 -A by molecular H 2 . The reduction of TiO 2 -A surface by spillover hydrogen was enhanced at Ag loading as low as 0.01 wt% on TiO 2 -A. The ratio of spillover H to Ag was as high as 675 at Ag loading of 0.01 wt% and the ratio decreased with increasing Ag loading. We found that the yield of phenolic products was linearly correlated with the amount of spillover hydrogen that created oxygen vacancy (Ov) through partial reduction of TiO 2 -A surface. Methanol was formed as the main side-product, indicating that the direct hydrocleavage of aromatic C-OCH 3 in guaiacol is favored over that of aromatic C-OH on the created site.