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

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      Author
      Andonova, S. M.
      Şentürk, G. S.
      Kayhan, E.
      Ozensoy, E.
      Date
      2009
      Source Title
      Journal of Physical Chemistry C
      Print ISSN
      1932-7447
      Volume
      113
      Issue
      25
      Pages
      11014 - 11026
      Language
      English
      Type
      Article
      Item Usage Stats
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      Abstract
      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.
      Keywords
      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
      Permalink
      http://hdl.handle.net/11693/22717
      Published Version (Please cite this version)
      http://dx.doi.org/10.1021/jp9005026
      Collections
      • Department of Chemistry 622
      • Institute of Materials Science and Nanotechnology (UNAM) 1841
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