Ordered mesoporous zirconium oxophosphate supported tungsten oxide solid acid catalysts: the improved Bronsted acidity for benzylation of anisole

A series of WO3 supported on ordered mesoporous zirconium oxophosphate (X wt% WO3/M-ZrPO) solid acid catalysts with a WO3 loading from 5 to 30 wt% were successfully synthesized, and their structure properties were characterized by X-ray diffraction (XRD), Raman spectroscopy, N-2-physisorption, transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, H-2 temperature-programmed reduction (H-2-TPR) and X-ray photoelectron spectroscopy (XPS). The catalytic performance of X wt% WO3/M-ZrPO in liquid phase benzylation of anisole was studied and the relation between activity and states of tungsten species was investigated detailedly. The maximum catalytic activity was reached at a 20 wt% WO3 loading, which possessed highly dispersed WO3 species and the strongest Bronsted acidity. Meanwhile, the well dispersed WO3 species strongly interacted with M-ZrPO, therefore, both sintering and leaching of WO3 species were effectively restrained. Moreover, compared with the traditional zirconium phosphate synthesized from the sol-gel method (ZrPsol-gel), the M-ZrPO with an abundant ordered mesostructure was propitious for improving the dispersion of WO3 species and catalytic performance. In addition, the 20 wt% WO3/M-ZrPO showed a markedly higher catalytic activity than H-ZSM5, H-Beta and 20 wt% WO3/ZrPsol-gel. Furthermore, the catalyst showed no discernible loss in activity or selectivity after five cycles.