Is BN an appropriate support for metal oxide catalysts?
Résumé
Abstract Boron nitride supported metal oxide (In2O3, Ga2O3 and SnO2) catalysts were prepared using a sol–gel method. The amounts of metal oxides (15–22 wt.%) deposed on the BN support were close to the theoretical monolayer. The support and the catalysts were characterized by XRD, XPS, TG, IR, SEM, TPR and adsorption microcalorimetry measurements. A study of the interfacial bonding between the oxide phases and the support surface revealed that the bonding between BN and the guest oxide is the strongest for In2O3. The results of adsorption microcalorimetry experiments performed on the samples using NH3 and SO2 as basic and acidic probes show that acid sites are predominant on their surface, while no real basicity could be evidenced. The mean acid strengths of the surfaces were found to vary in the order: 13In/BN > 17Sn/BN > 19Ga/BN > BN when using acetylacetonate metallic precursors. The test reaction of selective reduction of NO by C2H4 in high oxygen atmosphere was chosen to compare our BN-supported oxide samples with the same oxides supported on conventional ceramic supports. The results showed that the mechanical and chemical properties of BN were altered by the deposition of the active guest oxide. Moreover, it was demonstrated that BN is a too inert support material for assisting these oxides to complete easily a NOx reduction reaction mechanism.