Mo-modified Pd/Al₂O₃ catalysts for benzene catalytic combustion

Mo-modified Pd/Al₂O₃ catalysts were prepared by an impregnation method and tested for the catalytic combustion of benzene. The catalysts were characterized by N₂ isothermal adsorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of NH₃ (NH₃-TPD), H₂ temperature-programmed reduction (H₂-TPR), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The results showed that the addition of Mo effectively improved the activity and stability of the Pd/Al₂O₃ catalyst by increasing the dispersion of Pd active components, changing the partial oxidation state of palladium and increasing the oxygen species concentration on the surface of catalyst. In the case of the Pd-Mo/Al₂O₃ catalyst, benzene conversion of 90% was obtained at temperatures as low as 190°C, which was 45°C lower than that for similar performance with the Pd/Al₂O₃ catalyst. Moreover, the 1.0% Pd-5% Mo/Al₂O₃ catalyst was more active than the 2.0% Pd/Al₂O₃ catalyst. It was concluded that Pd and Mo have a synergistic effect in benzene catalytic combustion.