Effect of the metal−support interaction in Ag/CeO2 catalysts on their activity in ethanol oxidation

Resumo

The interaction of silver with the surface of CeO₂ in the Ag/CeO₂ catalysts prepared by coprecipitation and impregnation techniques was studied by temperature-programmed reduction, X-ray diffraction, and high-resolution transmission electron microscopy. It was shown that coprecipitation technique led to formation of strong silver–support interaction and the epitaxy of silver particles (d₁₁₁ = 2.35 Å) on the surface of CeO₂ (d₁₁₁ = 3.1 Å). This provided incresed catalytic activity in the oxidative dehydrogenation of ethanol at relatively low temperatures (a 15% conversion of ethanol with 100% selectivity for the formation of acetaldehyde was reached at 85°C). Above 130°C, the deep oxidation of ethanol to CO₂ becomes the predominant direction of a catalytic reaction, and the Ag/CеО₂ catalyst obtained by impregnation technique was most active in this region as a consequence of the weaker metal–support interaction.