Effect of P content in the conversion of guaiacol over Mo/γ-Al ₂O₃ catalysts

The effect of phosphorus content on Mo/γ-Al₂O₃ sulfide catalysts for the conversion of 2-methoxyphenol (guaiacol) was studied. The catalysts were prepared by successive impregnation of P (0.5, 1.0, 2.0. 3.0 and 5.0 wt.%) and then Mo (15 wt.%) precursors in excess solvent. The activities of the catalysts were evaluated in the hydrodeoxygenation (HDO) of guaiacol, carried out at 573 K and 5 MPa. The catalysts were characterized by BET surface area, UV-vis-DRS, electrophoretic migration (EM), X-ray Photoelectron Spectroscopy (XPS) and surface acidity techniques. The conversion of guaiacol increased with increase in P content up to 1.0 wt%, and then subsequently decreased at higher loadings. The increase in activity was attributed to the formation of two-dimensional MoS₂, while the subsequent decrease was ascribed to loss of active sites resulting from the formation of three-dimensional MoS₂. The differences in surface Mo species present on the catalyst were related to the amount of P contents. On the other hand, differences in selectivity, expressed in terms of the phenol/catechol ratio, were mainly influenced by the acid strength of the catalysts.