Physicochemical and Catalytic Properties of Vanadia/Titania Catalysts. I. Structural Properties
Titania gels T a and T b were precipitated from TiCl 4 at pH 3.0 and 9.0, respectively, using ammonia solution. Calcination products were obtained by the thermal treatment of the gels at 300, 400, 600, 750 and 1000°C, respectively. Thermal analysis, X-ray diffraction and FT-IR spectroscopy demonstra...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
SAGE Publishing
2001-03-01
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| Series: | Adsorption Science & Technology |
| Online Access: | https://doi.org/10.1260/0263617011494051 |
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| Summary: | Titania gels T a and T b were precipitated from TiCl 4 at pH 3.0 and 9.0, respectively, using ammonia solution. Calcination products were obtained by the thermal treatment of the gels at 300, 400, 600, 750 and 1000°C, respectively. Thermal analysis, X-ray diffraction and FT-IR spectroscopy demonstrated that the anatase → rutile transformation commenced when T a was calcined at 400°C, with the rutile form predominating when calcination was conducted at 600°C. Calcination at 750°C or 1000°C was associated with complete anatase → rutile conversion. The calcination product of T b at 400°C was pure anatase, transformation to rutile taking place above this temperature and predominating at 600°C. Rutile was the sole phase present when T b was calcined at 750°C. Vanadia/titania catalysts were obtained by impregnating T a and T b with an aqueous solution of NH 4 VO 4 of concentration sufficient to obtain samples containing 4.0, 6.0, 8.0 or 12.0 wt% V 2 O 5 . The calcination products at 400°C and 600°C were characterized by thermal analysis, X-ray diffraction, FT-IR spectroscopy, electronic spectral analysis and magnetic susceptibility measurements. The presence of vanadium enhanced the anatase → rutile transformation. The measured X-ray diffraction lines and FT-IR peaks indicated the existence of vanadium as a separate oxide, mainly V 2 O 5 . However, the electronic spectra and magnetic susceptibility measurements predicted the possible existence of a V 4+ species. |
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| ISSN: | 0263-6174 2048-4038 |