Synthesis, Characterization, and Catalytic Properties of Vanadium Oxide Catalysts Supported on AlPO4
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- 作者：Komandur V. R. Chary ; Gurram Kishan ; Kanaparthi Ramesh ; Chinthala Praveen Kumar ; and Guggilla Vidyasagar
- 刊名：Langmuir
- 出版年：2003
- 出版时间：May 27, 2003
- 年：2003
- 卷：19
- 期：11
- 页码：4548 - 4554
- 全文大小：159K
- 年卷期：v.19,no.11(May 27, 2003)
- ISSN：1520-5827
文摘
A series of V2O5/AlPO4 catalysts with vanadia loadings ranging from 2.5 to 20 wt % was prepared andcharacterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, electron spin resonancespectroscopy, temperature-programmed reduction (TPR), temperature-programmed desorption (TPD) ofNH3, BET surface area, and oxygen chemisorption methods. The catalytic properties were evaluated forthe vapor phase ammoxidation of 3-picoline to nicotinonitrile. TPR results indicated that the appearanceof a single reduction peak corresponds to V5+ to V3+. The XRD results suggest that, at low vanadia loadingsAlPO4 is found to be amorphous. However, at V2O5 loading of 7.38 wt % and above, AlPO4 exist as 
-cristobaliteform in addition to V2O5. TPD results show that the acidity increases with vanadia loading and decreasesat 7.38% and above loadings. The ESR spectra obtained under ambient conditions for the samples reducedat 640 K show the presence of V4+ in axial symmetry. Dispersion of vanadia was determined by oxygenchemisorption at 640 K and by the static method on the samples prereduced at the same temperature.The oxygen uptake measured at 640 K increases with increase in vanadia loading, whereas dispersion ofvanadia was decreased. The decrease in dispersion of vanadia was discussed in terms of formation ofcrystalline forms of V2O5 and AlPO4. The ammoxidation activity and selectivity of nicotinonitrile formationincrease with vanadia loading up to 9.5 wt % and did not change appreciably at higher loadings. Thecatalytic properties during ammoxidation are related to the oxygen chemisorption sites.
-cristobaliteform in addition to V2O5. TPD results show that the acidity increases with vanadia loading and decreasesat 7.38% and above loadings. The ESR spectra obtained under ambient conditions for the samples reducedat 640 K show the presence of V4+ in axial symmetry. Dispersion of vanadia was determined by oxygenchemisorption at 640 K and by the static method on the samples prereduced at the same temperature.The oxygen uptake measured at 640 K increases with increase in vanadia loading, whereas dispersion ofvanadia was decreased. The decrease in dispersion of vanadia was discussed in terms of formation ofcrystalline forms of V2O5 and AlPO4. The ammoxidation activity and selectivity of nicotinonitrile formationincrease with vanadia loading up to 9.5 wt % and did not change appreciably at higher loadings. Thecatalytic properties during ammoxidation are related to the oxygen chemisorption sites.