Properties and Reactivity of Fe–P–O Catalysts Prepared by Different Methods for Benzylation of Benzene

Fe–P–O catalysts were prepared by four different methods, and their catalytic performances were tested in the benzylation of benzene with benzyl chloride. In addition, the properties of these catalysts were characterized by powder X-ray diffraction (XRD), N2 isothermal adsorption–desorption, scanning electronic microscopy (SEM), pyridine adsorbed infrared spectroscopy (Py-IR), and X-ray photoelectron spectroscopy (XPS) techniques. The preparation methods and component significantly modified the acidity, structure, and morphology of Fe–P–O catalysts, which in turn affected the catalytic reactivity of these catalysts in the benzylation reaction. Sol–gel synthesized Fe–P–O catalyst with P/Fe = 0.25 (atomic ratio) (FeP-0.25-SG) not did only exhibit the highest activity among these as-prepared catalysts, but also its reactivity was almost constant even after six reactions cycled. The interaction of Fe and P occurred in sol–gel prepared Fe–P–O catalysts. Such interaction modified the Lewis acidity of these catalysts, due to the redistribution of the charges and the formation of the Fe3+/Fe2+ couple. The density of weak and medium Lewis acid sites on these catalysts was close relative to the reactivity of these Fe–P–O catalysts. FeP-0.25-SG showed the highest catalytic performance among these catalysts, owing to a large density of weak and medium Lewis acid sites on the large-surface-area small-size catalyst.