Selective oxidation of alcohols over Ag-containing Si₃N ₄ catalysts

Ag-containing ceramic catalysts modified or unmodified with Zr and Al were studied in selective catalytic oxidation of ethylene glycol and ethanol into the corresponding carbonyl compounds. The influence of phase and chemical composition of ceramic supports prepared by the self-propagating high-temperature synthesis (SHS) on the basis of silicon nitride was considered. The catalysts were characterized by X-ray diffraction, using scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDX) unit, and tested in selective oxidation of ethanol and ethylene glycol into acetaldehyde and glyoxal, respectively. It was shown that the presence of ZrO₂ and Si₃Al₁₂O₉N₁₀ phases in the support composition allowed increasing glyoxal selectivity up to 50% at 87% conversion of glycol. Ag-containing ceramic catalysts also demonstrated high selectivity/activity in ethanol oxidation (95% acetaldehyde selectivity and 100% ethanol conversion at 300 °C), while the support phase composition did not influence the catalytic performance.