Gold catalysts supported on nanostructured Ce–Al–O mixed oxides prepared by organic sol–gel

Nanostructured ceria–alumina mixed oxides containing different concentrations of ceria (10 and 30 wt.%) were prepared by the sol–gel method using organo-metallic precursors of alumina and ceria. The size of alumina and ceria particles in the prepared Ce–Al–O mixed oxides was smaller than that of pure alumina or ceria. The gold catalysts (3 wt.% Au) supported on ceria–alumina mixed oxides by deposition–precipitation (DP) using HAuCl4 and urea were characterized by several techniques: TEM, XPS and UV–vis spectroscopy, and temperature programmed reduction/oxidation (TPR/TPO). The catalytic activity of prepared Au/CeO2–Al2O3 catalysts in CO oxidation was higher than that of Au/Al2O3 and Au/CeO2 catalysts. Nanostructured ceria incorporated into an alumina matrix has been found quite effective for gold species activation in CO oxidation. In fact, transient analysis of CO oxidation provided an estimate of the relative content of (Au–ceria vacancy) active sites in catalysts. Obtained values are in good agreement with the order of activity for tested samples and gold dispersion according to EXAFS data.

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► Ce–Al oxides prepared by sol–gel are effective in the formation of active Au species for CO oxidation.
► The content of (Au–Ce vacancy) active sites was estimated by transient analysis of CO oxidation.
► The content of (Au–Ce vacancy) sites correlates with order of activity of studied catalysts.
► Pre-oxidized Au/CeO2 and Au/Ce–Al samples are more active in CO oxidation than pre-reduced ones.