Laser raman spectroscopy of supported vanadium oxide catalysts
Laser raman spectroscopy of supported vanadium oxide catalysts
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DOI：
10.1021/j100373a067
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发表时间：
1990-05
期刊：
影响因子：
--
通讯作者：
G. Went;S. Oyama;A. Bell
中科院分区：
文献类型：
--
作者：
G. Went;S. Oyama;A. Bell
Supported vanadia catalysts were studied by Raman spectroscopy to establish the effects of vanadia loading and support composition on the structure of the dispersed vanadia species. Three types of vanadia species were found to be present on SiO{sub 2}, TiO{sub 2}, and Al{sub 2}O{sub 3} supports: monomeric vanadyls, one- and two-dimensional vanadate chains, and crystallites of V{sub 2}O{sub 5}. Monomeric vanadyls are characterized by a narrow Raman band in the region of 1,026-1,042 cm{sup {minus}1}, the position being sensitive to the identity of the support. The terminal V{double bond}O groups of polyvanadate chains give rise to a broad feature in the region of 800-1,000 cm{sup {minus}1} which, in the case of TiO{sub 2}-supported V{sub 2}O{sub 5}, shifts to higher frequency as the V{sub 2}O{sub 5} loading increases. Crystalline V{sub 2}O{sub 5} was detected at higher loadings on all three supports. Evidence from Raman spectroscopy and O{sub 2} chemisorption indicates that the dispersion of vanadia increases in the order SiO{sub 2} < Al{sub 2}O{sub 3} {approximately} TiO{sub 2}.
Supported vanadia catalysts were studied by Raman spectroscopy to establish the effects of vanadia loading and support composition on the structure of the dispersed vanadia species. Three types of vanadia species were found to be present on SiO{sub 2}, TiO{sub 2}, and Al{sub 2}O{sub 3} supports: monomeric vanadyls, one- and two-dimensional vanadate chains, and crystallites of V{sub 2}O{sub 5}. Monomeric vanadyls are characterized by a narrow Raman band in the region of 1,026-1,042 cm{sup {minus}1}, the position being sensitive to the identity of the support. The terminal V{double bond}O groups of polyvanadate chains give rise to a broad feature in the region of 800-1,000 cm{sup {minus}1} which, in the case of TiO{sub 2}-supported V{sub 2}O{sub 5}, shifts to higher frequency as the V{sub 2}O{sub 5} loading increases. Crystalline V{sub 2}O{sub 5} was detected at higher loadings on all three supports. Evidence from Raman spectroscopy and O{sub 2} chemisorption indicates that the dispersion of vanadia increases in the order SiO{sub 2} < Al{sub 2}O{sub 3} {approximately} TiO{sub 2}.