Mesoporous TiO 2 , ZrO 2 and ZrO 2 -TiO 2 mixed oxides were synthesized by the sol-gel method and the Au/TiO 2 , Au/ZrO 2 and Au/ZrO 2 -TiO 2 catalysts were prepared by deposition-precipitation method using urea solution as a precipitating agent. These materials were characterized by UV–vis spectroscopy, X-ray diffraction (XRD), N 2 adsorption-desorption isotherms, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and in situ FTIR-pyridine (FTIR-Py) adsorption. XRD patterns of the samples confirmed the formation of ZrTiO 4 phase in the ZrO 2 -TiO 2 mixed oxides. TEM micrographs showed that nanosized gold particles on the catalyst had an average diameter smaller than 5 nm. Metallic gold (Au 0 ) and oxidized Au species (Au n δ+ ) on the surface of the catalysts were evidenced by UV–vis and XPS characterization. In the partial oxidation of methanol (POM) reaction, among the six catalysts, the high metallic Au 0 /Au + ratio and low surface acidity in the Au/ZrO 2 catalysts are chiefly responsible for the highest hydrogen production rate in the whole temperature range between 210 and 300 °C. Methanol decomposition as secondary reaction was favored on TiO 2 -based catalysts at higher temperature, producing a large amount of CO. Formation of ZrO 2 -TiO 2 solid solution resulted in generation of both Brønsted and Lewis acid sites; as a result, dehydrogenation and oxidative dehydrogenation of methanol was allowed over Au/ZrO 2 -TiO 2 catalysts.
- Gold catalysts
- Partial oxidation of methanol
- ZrO -TiO