Investigation of the effects of phosphorus on the selective hydrodeoxygenation of anisole over an Fe/SiO2 catalyst

Abstract

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 FeO_x 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.