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Surface characterization of WO(3)/ZrO(2) catalysts.
Nithya Vaidyanathan1, David M Hercules, Marwan Houalla
1Department of Chemistry, Vanderbilt University, Nashville, TN 37230, USA.
Analytical and Bioanalytical Chemistry
|August 20, 2002
Summary
Tungsten oxide (WO(3)) on zirconia (ZrO(2)) catalysts were synthesized and characterized. Increasing tungsten loading influences the formation of tungsten species and surface structure on the zirconia support.
Area of Science:
- Materials Science
- Catalysis
- Surface Chemistry
Background:
- Zirconia (ZrO(2)) is a widely used catalyst support.
- Tungsten oxide (WO(3)) is known for its catalytic properties.
- Understanding the interaction between WO(3) and ZrO(2) is crucial for catalyst design.
Purpose of the Study:
- To synthesize WO(3)/ZrO(2) catalysts with varying tungsten loadings.
- To characterize the structural and surface properties of these catalysts.
- To elucidate the formation and structure of tungsten species on the zirconia support.
Main Methods:
- Incipient wetness impregnation for catalyst synthesis.
- X-ray Diffraction (XRD) and Raman Spectroscopy for structural analysis.
- X-ray Photoelectron Spectroscopy (XPS), Ion Scattering Spectroscopy (ISS), and Infrared (IR) Spectroscopy for surface and chemical state analysis.
Main Results:
- The ZrO(2) support was primarily monoclinic.
- Formation of W interaction species increased with W loading up to 8.8 wt%.
- Bulk WO(3) appeared at >= 3.0 wt% W loading, with 2D polymeric patches forming between 3.0-4.5 wt% and multilayer structures above 4.5 wt%.
Conclusions:
- The structure of WO(3)/ZrO(2) catalysts depends significantly on tungsten loading.
- Tungsten species evolve from interaction species to bulk WO(3) with increasing loading.
- A proposed schematic illustrates the proposed catalyst structure, highlighting W species formation on ZrO(2) hydroxyl groups.