Investigation of the effects of phosphorus on the selective hydrodeoxygenation of anisole over an Fe/SiO2 catalyst†
Hydrodeoxygenation (HDO) of lignin derivatives offers an effective approach to produce aromatics. In this work, phosphorus (P) modified Fe/SiO2 catalysts were prepared by a stepwise incipient wetness impregnation method. Influences of P on the physicochemical properties of Fe/P–SiO2 catalysts and their catalytic performance for the HDO of anisole were studied. Characterization results revealed that the addition of P into SiO2 reduced the sites for stepwise impregnated Fe species and FeOx particles could be isolated and prevented from aggregating by the optimized contents of P. The reduction of catalysts and the adsorption of H2 were inhibited with increasing the contents of P. In addition, the acidity increased linearly with the P loading pointing to coordinatively unsaturated Fe cations as the Lewis acidic centers in the catalysts. Evaluation results showed that P could tune the distribution of products from aromatics to methyl containing compounds. The aromatics selectivity was promoted to 76.5% with an optimized Fe/P atomic ratio in the 0.5PFS catalyst. Furthermore, an increasing concentration of Lewis acid sites resulted in the methyl transfer reaction (transalkylation). The CH4 selectivity (∼1.55%) was reduced with high contents of P in the catalysts, indicating a significant reduction of carbon loss. These findings provide useful information for the rational design of Fe-based catalysts, which improve the biomass conversion efficiency to platform chemicals.