Selective Hydrodeoxygenation of Guaiacol to Phenolics by Ni/Anatase TiO 2 Catalyst Formed by Cross-Surface Migration of Ni and TiO 2

The catalytic properties of physical mixtures of Ni particles (100-200 nm) with nanoparticles of anatase TiO 2 (TiO 2 -A), ZrO 2 , Al 2 O 3 , rutile TiO 2 (TiO 2 -R), and CeO 2 were investigated for the hydrodeoxygenation (HDO) of guaiacol. High selectivities to phenolics were obtained only for Ni mixed with anatase TiO 2 (Ni and TiO 2 -A), while saturated hydrocarbons were the main products for the mixtures with other supports. By thermal treatment in hydrogen gas only at 300 °C or higher and subsequently separating the large Ni particles from the TiO 2 -A particles with a magnet, it was further discovered that there was migration of TiO 2 from TiO 2 -A onto the large Ni particles, resulting in an amorphous TiO 2 overlayer on the Ni particles as evidenced by high-resolution TEM, and vice versa, migration of Ni onto TiO 2 -A. The TiO 2 overlayer rendered the Ni particles completely inactive as a hydrogenation/hydrodeoxygenation catalyst. Conversely, the small amounts of Ni (