Nature of the Ti-Ba interactions on the BaO/TiO/Al O NO storage system

A ternary oxide-based NO* storage material in the form of BaOZTiOZy-AlO was synthesized and characterized. Thermally induced structural changes occurring on the surfaces of the TiOZy-AlO and BaOZ TiO Zy-AlO systems were studied in a comparative manner within 300-1273 K via X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and BET surface area analysis. The surface acidity of the studied oxide systems was also investigated via pyridine adsorption monitored by in-situ Fourier transform infrared (FTIR) spectroscopy. BaO/TiOγ-Al O ternary oxide was synthesized by incorporating different loadings of (8-20 wt %) BaO onto the TiO/γ Al O support material, which was originally prepared using the sol-gel method. In the TiOZy-Al2O3 binary oxide support material, anatase phase exhibited a relatively high thermal stability at T < 1073 K. The presence of TiO domains on the surface of the alumina particles was found to alter the surface acidity of alumina by providing new medium-strength Lewis acid sites. SEMZEDX results indicate that in the BaO/TiOγ-AlO system, TiO domains present a significant affinity toward BaO and/or Ba(NO) resulting in a strong Ti-Ba interaction and the formation of overlapping domains on the surface. The presence of TiO also leads to a decrease in the decomposition temperature of the Ba(N0) phase with respect to the Ti-free Ba(N0) ZyAlO system. Such a destabilization is likely to occur due to a weaker interaction between Ba(N0) and y-Al0 domains in the ternary oxide as well as due to the change in the surface acidity in the presence of TiO . At relatively high temperatures (e.g., 873-1273 K) formation of complex structures in the form of BaTiO, BaAl TiO, BaTiO, andor Ba :AlTiO., were also observed. © 2009 American Chemical Society.