In Situ Magnetic Resonance Investigation of Styrene Oxidation over TS‐1 Zeolites

Zhuang, Jing; Yang, Gang; Ma, Ding; Lan, Xijie; Liu, Xiumei; Han, Xiuwen; Bao, Xinhe; Muêller, U.

doi:10.1002/anie.200461113

Cited by 56 publications

(37 citation statements)

References 31 publications

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“…However, there are still many issues under debate, such as what's the exact nature of the active site [36,37,68,69] and the reaction pathways [70][71][72][73]. Recently, we have conducted a thorough investigation of the active titanium species in TS-1 zeolite [74].…”

Section: In Situ (Uv) Raman Spectroscopic Characterization Of Catalytmentioning

confidence: 99%

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

et al. 2014

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UV Raman spectroscopy has been demonstrated to be a powerful technique in catalysis because it can avoid the fluorescence interference occurring in visible Raman spectroscopy and concurrently enhance the Raman scattering intensity owing to the short wavelength of the excitation laser and resonance Raman effect. This article briefly reviews the recent advances in the study on heterogeneous catalysis by UV Raman spectroscopy, including the identification of isolated transition metal ions in molecular sieves, in situ study of zeolite assembly mechanisms and catalytic reaction mechanisms, and the monitoring of the surface phase transformation of metal oxide photocatalysts. UV (resonance) Raman spectroscopy, with the power of resonance enhancement for Raman signal and the advantage of high sensitivity for surface structure, coupling with in situ methodology, can provide the information about the active sites/phase and their assembling mechanisms, which are helpful for the understanding of heterogeneous catalysis and the rational design of highly active and selective catalysts.

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Section: In Situ (Uv) Raman Spectroscopic Characterization Of Catalytmentioning

confidence: 99%

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

et al. 2014

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“…This assumption was confirmed by calculation of the chemical shift at 64.7 ppm for the corresponding glycol structure. 148 When the sample was heated at 313 K after adsorption, more and more hemiacetal species appeared with the decrease in styrene (Fig. 14c-d).…”

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In situsolid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach

et al. 2012

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In situ solid-state NMR is a well-established tool for investigations of the structures of the adsorbed reactants, intermediates and products on the surface of solid catalysts. The techniques allow identifications of both the active sites such as acidic sites and reaction processes after introduction of adsorbates and reactants inside an NMR rotor under magic angle spinning (MAS). The in situ solid-state NMR studies of the reactions can be achieved in two ways, i.e. under batch-like or continuous-flow conditions. The former technique is low cost and accessible to the commercial instrument while the latter one is close to the real catalytic reactions on the solids. This critical review describes the research progress on the in situ solid-state NMR techniques and the applications in heterogeneous catalysis under batch-like and continuous-flow conditions in recent years. Some typical probe molecules are summarized here to detect the Brønsted and Lewis acidic sites by MAS NMR. The catalytic reactions discussed in this review include methane aromatization, olefin selective oxidation and olefin metathesis on the metal oxide-containing zeolites. With combining the in situ MAS NMR spectroscopy and the density functional theoretical (DFT) calculations, the intermediates on the catalyst can be identified, and the reaction mechanism is revealed. Reaction kinetic analysis in the nanospace instead of in the bulk state can also be performed by employing laser-enhanced MAS NMR techniques in the in situ flow mode (163 references).

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“…Recently, Corma et al [3][4] found that TS-1 zeolite itself can catalyze chemical reactions because the Ti IV sites have vacant d orbitals and show Lewis acidity toward adsorbates. [5][6][7][8][9][10] Previously, we studied the various Ti IV species in TS-1 zeolite [11][12][13] and identified two types of Lewis acidic site: TiA C H T U N G T R E N N U N G (OSiO 3 ) 4 and (OSiO 3 ) 3 Ti(OH). In addition, the former was found to be more reactive in the oxidation of trimethylphosphine (TMP).…”

Section: Introductionmentioning

confidence: 99%

Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti^IV and Ti^III Ions in MCM‐22 Zeolite

Yang

Zhou

Liu

et al. 2011

Chemistry A European J

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Isolated Ti species in zeolites show unique catalytic activities for a variety of chemical reactions. In this work, density functional calculations were used to explore three current concerns: 1) the distributions of TiIV and TiIII ions in the MCM‐22 zeolite; 2) the Lewis acidity of the TiIV and TiIII sites; and 3) activation of alkane CH bonds by photocatalysis with Ti‐doped zeolites. Neither the TiIV nor TiIII ions are randomly distributed in the MCM‐22 zeolite. The orders of relative stability are very close for the eight TiIV and TiIII sites, and the T3 site is the most probable in both cases. The wavelengths for TiIV–TiIII excitations were calculated to lie in the range λ=246.9–290.2 nm. The Ti3IV site shows Lewis acidity toward NH3 in two different modes, and these two modes can coexist with each other. The calculated TiIV coordination numbers, TiIVO bond elongations, and charge transfers caused by NH3 adsorption are in good agreement with previous results. Similarly, two different NH3 adsorption modes exist for the Ti3III site; the site that exhibits radical transfer from the lattice O to N atoms is preferred due to the higher adsorption energy. This indicates that the Ti3III site does not show Lewis acidity, in contrast to the Ti3IV site. At the Ti3III site, the energy barrier for activating the methane CH bond was calculated to be 33.3 kJ mol−1 and is greatly reduced by replacing the hydrogen atoms with methyl groups. In addition, the reactivity is improved when switching from MCM‐22 to TS‐1 zeolite. The studies on the various Ti species reveal that lattice O atoms rather than TiIII radicals are crucial to the activation of alkane CH bonds. This work provides new insights into and aids understanding of the catalysis by isolated Ti species in zeolites.

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In Situ Magnetic Resonance Investigation of Styrene Oxidation over TS‐1 Zeolites

Cited by 56 publications

References 31 publications

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

In situsolid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach

Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti^IV and Ti^III Ions in MCM‐22 Zeolite

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In Situ Magnetic Resonance Investigation of Styrene Oxidation over TS‐1 Zeolites

Cited by 56 publications

References 31 publications

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

UV Raman Spectroscopic Characterization of Catalysts and Catalytic Active Sites

In situsolid-state NMR for heterogeneous catalysis: a joint experimental and theoretical approach

Density Functional Calculations on the Distribution, Acidity, and Catalysis of TiIV and TiIII Ions in MCM‐22 Zeolite

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Density Functional Calculations on the Distribution, Acidity, and Catalysis of Ti^IV and Ti^III Ions in MCM‐22 Zeolite