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.