Influence of pretreatment atmospheres on the performance of bimetallic Au-Pd supported on ceria-zirconia mixed oxide catalysts for benzyl alcohol oxidation

Abstract

Monometallic Au, Pd and bimetallic Au-Pd catalysts supported on a Ce0.62Zr0.38O2mixed oxide have been synthesized by the sol-immobilization method. The catalysts have been characterized by inductively coupled plasma-atomic emission spectroscopy (ICPAES), N2 physisorption, temperature programmed oxidation (TPO), X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy-high angle annular dark field imaging (STEM-HAADF) and X-ray energy dispersive spectroscopy (XEDS) techniques. A synergistic effect between Au and Pd has been observed in the selective oxidation of benzyl alcohol on ceria-zirconia. Moreover, the catalytic activity of these bimetallic Au-Pd catalysts is higher than that on other commonly used supports, as it is the case of activated carbon or carbon nanotubes. The treatments in oxidative and inertatmospheres at 250 °C improve the catalytic activity with respect to the fresh, unpretreated, catalyst, which might be attributed to the elimination of thepolyvinylpyrrolidone polymer used as protective agent during the preparation of the bimetallic nanoparticles. Subsequent reduction of the oxidized bimetallic catalyst leads to an activity similar to that of the fresh catalyst, which is reduced at room temperature with H2 bubbles.