Nature of the Ti-Ba interactions on the BaO/TiO2/Al 2O3 NOx storage system

Andonova, S. M.
Şentürk, G. S.
Kayhan, E.
Ozensoy, E.
Source Title
Journal of Physical Chemistry C
Print ISSN
Electronic ISSN
11014 - 11026
Journal Title
Journal ISSN
Volume Title

A ternary oxide-based NO* storage material in the form of BaOZTiO2Zy-Al2O3 was synthesized and characterized. Thermally induced structural changes occurring on the surfaces of the TiO2Zy-Al2O3 and BaOZ TiO 2Zy-Al2O3 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/TiO2γ-Al 2O3 ternary oxide was synthesized by incorporating different loadings of (8-20 wt %) BaO onto the TiO2/γ Al 2O3 support material, which was originally prepared using the sol-gel method. In the TiO2Zy-Al2O3 binary oxide support material, anatase phase exhibited a relatively high thermal stability at T < 1073 K. The presence of TiO2 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/TiO2γ-Al2O3 system, TiO2 domains present a significant affinity toward BaO and/or Ba(NO3) 2 resulting in a strong Ti-Ba interaction and the formation of overlapping domains on the surface. The presence of TiO2 also leads to a decrease in the decomposition temperature of the Ba(N03) 2 phase with respect to the Ti-free Ba(N03) 2ZyAl2O3 system. Such a destabilization is likely to occur due to a weaker interaction between Ba(N03) 2 and y-Al203 domains in the ternary oxide as well as due to the change in the surface acidity in the presence of TiO 2. At relatively high temperatures (e.g., 873-1273 K) formation of complex structures in the form of BaTiO3, Ba1.23Al 2.46Ti5.54O16, BaTiO5, andor Ba x:AlyTizOn., were also observed. © 2009 American Chemical Society.

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Book Title
Alumina particles, Anatase phase, BET surface area, Binary oxides, Complex structure, Decomposition temperature, Energy dispersive x-ray, High temperature, High thermal stability, In-situ, Lewis acid site, Oxide systems, Pyridine adsorption, SEM, Sol-gel methods, Storage systems, Structural change, Support materials, Surface acidity, Ternary oxides, Thermally induced, TiO, Adsorption, Aluminum, Barium, Fourier transform infrared spectroscopy, Gelation, Raman spectroscopy, Scanning electron microscopy, Sol-gel process, Surface analysis, Surfaces, Titanium dioxide, Titanium oxides, X ray diffraction, X ray diffraction analysis, Barium compounds
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