Enhancement of activity and hydrothermal stability of Pd/ZrO2-Al2O3 doped by Mg for methane combustion under lean conditions.

By a facile doping strategy, a new Pd catalyst supported on ZrO 2 -Al 2 O 3 composite doped by Mg was developed. The catalyst was carefully characterized by X-ray diffraction (XRD), CO chemical adsorption, transmission electron microscope (TEM), NH 3 temperature programmed desorption (NH 3 -TPD) and X-ray photoelectron spectroscopy (XPS). The results revealed that the physical and chemical properties of the catalyst can be modulated by Mg dopant. An MgAl 2 O 4 spinel was formed by Mg doping, which can stabilize Pd 2+ species and inhibit the formation of hydroxyl groups on the surface of support. Compared with its analogous catalyst without Mg dopant, the Mg-doped catalyst had higher Pd dispersion and smaller Pd nanoparticles. Moreover, a more suitable acidity for methane oxidation can be generated on the surface of the catalyst upon Mg doping. Therefore, the introduction of Mg doping strongly enhanced the low-temperature activity and hydrothermal resistance of the catalyst for the total oxidation of methane under lean conditions. Notably, the complete conversion temperature of methane can decreased significantly by 40–50 °C with the doped catalyst before and after harsh hydrothermal aging treatment. [ABSTRACT FROM AUTHOR]