Catalytic hydrodeoxygenation of anisole over Re-MoOx/TiO2 and Re-VOx/TiO2 catalysts

Abstract

The hydrodeoxygenation of anisole at 300 °C and 3 MPa H2 in a batch reactor is used as a model reaction to explore the performance of TiO2-supported Re-MoOx and Re-VOx catalysts. The binary catalysts were prepared with different Re and MoOx (or VOx) loadings and characterized by nitrogen physisorption, ICP-MS and AAS, XRD, FTIR, H2-TPR, NH3-TPD, H2-TPD, TEM and XPS techniques. A series of catalysts consisting of a base-metal (Re, Ga, Ni and Co) in combination with reducible metal oxide (Mo and V) were initially screened: due to its oxophilic nature only supported Re catalysts showed the ability to catalyze aromatic C-O bonds to produce aromatic hydrocarbons. This capability was enhanced by pairing Re with partially reduced surface MoOx (or VOx) sites, particularly in equimolar proportions. The catalytic activity, expressed as intrinsic reaction rate, was found to rely on the nature of surface Re, Mo and V species: the activity of Re-MoOx/TiO2 catalysts is dominated by exposed Mo5+ sites while that of Re-VOx/TiO2 catalysts is controlled by Re4+ sites. The results also reveal that despite the highest intrinsic activity of Mo5+ sites, they require the presence a specific type of active sites such as Re, in appropriate amount, to enable the enhanced benzene/toluene production.