Effect of TiO₂ in supported NiWS catalysts for the hydrodeoxygenation of guaiacol

A series of NiWS catalysts supported on TiO₂, ZrO₂ and TiO₂-ZrO₂ mixed oxides was tested in the hydrodeoxygenation of guaiacol. The TiO₂/ZrO₂ ratio in the mixed oxides was varied to elucidate the effect of the titania content on the catalyst activity. According to our results, high acidity values seem to favor the demethylation route with catechol as the main product, while a medium acid strength could probably be the active site for the scission of the C_aromatic-OCH₃ bond. Moreover, the production of completely deoxygenated compounds was directly related with the TiO₂ percentage on the catalysts. In this sense, guaiacol needs to be converted by the demethoxylation route, in order to avoid the catechol formation, which is a coke precursor, and phenol production route is improved. A fair correlation between medium acid strength for the catalysts and the phenol formation was also found. The catalyst supported on TiO₂ was found to be the most active per atom of metal, 62% higher than the NiW/TZ(80/20) catalysts. The content of titania on the support was relevant to obtain completely deoxygenated compounds, such as cyclohexane and benzene.