Size-Dependent Strong Metal–Support Interactions of Rutile TiO 2 -Supported Ni Catalysts for Hydrodeoxygenation of m-Cresol.

A series of rutile TiO₂-supported Ni catalysts with varying Ni sizes were prepared and reduced at 650 °C to explore the effect of Ni size on the strong metal–support interactions (SMSI) and its consequences on the hydrodeoxygenation (HDO) of m-cresol at 350 °C and atmospheric pressure. When the Ni size increases from 4 to 29.1 nm, the SMSI becomes stronger, e.g., the thickness of the TiO_x overlayer and the coverage extent of TiO_x on the Ni particle surface increase. Direct deoxygenation to toluene is the dominant pathway on Ni/TiO₂ catalysts with varying Ni loadings, with almost no CH₄ being formed. These results indicate that the TiO_x overlayer significantly alters the property of Ni. That is, the C-C hydrogenolysis activity on bare Ni is completely inhibited due to SMSI, while the deoxygenation activity is improved at the Ni-TiO_x interfacial perimeter sites. Meanwhile, the turnover frequency of HDO on small Ni particles of 4 nm is > 2 times higher than that on large Ni particles of 29.1 nm, indicating that the small Ni particle with moderate SMSI appears to be optimal for the direct deoxygenation of m-cresol to toluene. The results suggest HDO activity may be enhanced by tuning the metal particle size and SMSI degree. [ABSTRACT FROM AUTHOR]