Epoxidation of styrene on Si/Ti/SiO2 catalysts prepared by chemical grafting

Yang, Qihua; Wang, Suli; Lu, Jiqing; Xiong, Guang; Feng, Zhaochi; Xin, Qin; Li, Can

doi:10.1016/s0926-860x(99)00397-x

Cited by 78 publications

(47 citation statements)

References 29 publications

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“…Highly dispersed titanium species on silica (Ti/SiO 2 ) were prepared by chemical grafting using TiCl 4 and tetraethyl othosilicate as the precursors and SiO 2 as the support [49]. The catalysts were tested for the epoxidation of styrene using tert-butyl hydroperoxide (TBHP) as the oxidant.…”

Section: Titanium Species On Siomentioning

confidence: 99%

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

2003

Journal of Catalysis

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142

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Section: Titanium Species On Siomentioning

confidence: 99%

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

2003

Journal of Catalysis

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142

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“…Electronic spectroscopy in the UV-vis region is a useful technique for studying the electronic state of isolated transition metal ions and aggregated transition metal oxides [1]. UV resonance Raman spectroscopy has been proven to be a powerful technique for identifying isolated transition metal atoms substituted in the framework of molecular sieves or grafted on metal oxide [32][33][34][35][36][37][38]. In the present work, the coordination environment of Fe ions in SBA-15 were characterized by diffused reflectance UV-vis and UV resonance Raman spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Direct synthesis of highly ordered Fe-SBA-15 mesoporous materials under weak acidic conditions

Feng

Lian

et al. 2005

Microporous and Mesoporous Materials

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192

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“…14 An increase in the intensity of Raman signal and decrease in the intensity of fluorescence background help to increase the sensitivity of the Raman spectra. Moreover, the resonance Raman effect will selectively enhance the intensity of the Raman signal by several orders of magnitude when the excitation laser line is close to the electronic transition absorption of the samples.…”

mentioning

confidence: 99%

Direct spectroscopic evidence for vanadium species in V-MCM-41 molecular sieve characterized by UV resonance Raman spectroscopy

Xiong

et al. 2000

Chem. Commun.

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Vanadium species in tetrahedral and octahedral coordination in V-MCM-41 molecular sieve are characterized by UV resonance Raman bands at 1070 and 930 cm 21 respectively.Vanadium-substituted molecular sieves have been found to be excellent catalysts for many selective oxidation reactions. [1][2][3] In particular, V-MCM-41 has drawn much interest owing to its large pore diameter which is suitable for selective oxidation of large organic compounds. [4][5][6] The catalytic activity and selectivity of vanadium-substituted molecular sieves are directly related to the coordination structures of the vanadium species in the molecular sieves. In general, three forms of vanadium species, isolated tetrahedral, two-dimensional octahedral species and crystalline V 2 O 5 , are believed to be present. 4,5,7,8 The coordination structure of vanadium species in V-MCM-41 has been investigated by 51 V NMR, UV-VIS absorption spectroscopy and many other techniques, 4,5,8 but identification of vanadium species in tetrahedral or octahedral coordination environments is not straightforward. Raman spectroscopy is a potentially viable technique for the study of the structure of vanadium species in V-MCM-41, since it has been used to characterize supported vanadium oxides with both tetrahedral and octahedral coordination structures. 9,10 However, there have been relatively few Raman studies on vanadium-substituted MCM-41, 8 mainly because of fluorescence interference and the low sensitivity of conventional Raman spectroscopy. The limited amount of substituted vanadium atoms also hinders the application of Raman spectroscopy in characterization of vanadium atoms in V-MCM-41.UV Raman spectroscopy has been proved to be a powerful technique for the study of catalysts and other solids, 11,12 especially, for the identification of isolated transition metal atoms substituted in the framework of molecular sieves 13 or grafted on metal oxides. 14 An increase in the intensity of Raman signal and decrease in the intensity of fluorescence background help to increase the sensitivity of the Raman spectra. Moreover, the resonance Raman effect will selectively enhance the intensity of the Raman signal by several orders of magnitude when the excitation laser line is close to the electronic transition absorption of the samples.In this work, for the first time, we study the different vanadium species in V-MCM-41 using UV resonance Raman spectroscopy. Based on the UV resonance Raman effect the vanadium species in tetrahedral and octahedral environments in V-MCM-41 can be successfully identified by UV resonance Raman spectroscopy.MCM-41 and V-MCM-41 were synthesized according to the method reported in the literature. 4 V-MCM-41 samples which possess Si/V ratios of 250, 125 and 60 are denoted V-MCM-41 (250), V-MCM-41 (125) and V-MCM-41 (60), respectively. The as-synthesized samples show XRD patterns matching well with these reported in the literature. 4,5,15 UV Raman spectra were recorded on a homemade UV Raman spectrometer. 12 244 and 488 nm lines from a Innova 3...

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Epoxidation of styrene on Si/Ti/SiO2 catalysts prepared by chemical grafting

Cited by 78 publications

References 29 publications

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Identifying the isolated transition metal ions/oxides in molecular sieves and on oxide supports by UV resonance Raman spectroscopy

Direct synthesis of highly ordered Fe-SBA-15 mesoporous materials under weak acidic conditions

Direct spectroscopic evidence for vanadium species in V-MCM-41 molecular sieve characterized by UV resonance Raman spectroscopy

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