Abstract
Ce–Fe mixed oxides were prepared by urea gelation coprecipitation method and used as supports of gold catalysts. The impact of the support composition on the catalytic performance for the preferential CO oxidation (PROX) was studied by varying the Ce/(Ce+Fe) ratio. A deep characterization study by different tools such as XRD, HRTEM, TPR and FTIR spectroscopy was undertaken in order to correlate the structural characteristics of the catalysts and the gold oxidation state and dispersion with the catalytic properties. The results revealed that the variation of the support composition led to significant differences in the gold particles size (in the range 1–25nm), which affected strongly the CO oxidation activity of Au/CeO2–Fe2O3 catalysts under PROX conditions. The following activity order was observed: Au/CeO2≈Au/Ce50Fe50>Au/Ce75Fe25>Au/Ce25Fe75>Au/Fe2O3. The support with composition 50wt.% CeO2–50wt.% Fe2O3 appeared beneficial not only for nucleation and growth of highly dispersed gold particles (1–1.8nm), but also for activation of oxygen and its mobility. Moreover, the presence of Fe2O3 in the supports composition improved the resistance towards deactivation by CO2. The CeO2–Fe2O3 supports comprised different amount of two phases: cubic CeO2-like solid solution and hematite. The analysis of the characterization data suggested that the solid solution formation probably proceeded via a dopant interstitial compensation mechanism.
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