Incorporation of titanium into polymorph C for catalytic epoxidation of cyclohexene

Lee, Fang Yin; Lv, Lu; Su, Fabing; Liu, Tao; Liu, Yan; Sow, Chorng Haur; Xin, Zhao

doi:10.1016/j.micromeso.2009.04.036

Cited by 8 publications

(3 citation statements)

References 22 publications

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“…Metal-substituted BEA and MFI have been the most studied zeolites for reactions that require Lewis acidity. ,,, BEA consists of a highly faulted intergrowth of two polymorphisms (polymorphism A and B), with two straight channels along the a - and b - axes, and one tortuous channel along the c -axis . Al–FAU has been widely studied in reactions involving Brønsted acidity, but only few studies have reported the substitution of Ti or Sn in FAU or BEC. − BEC is a third polymorphism of zeolite beta that can be synthesized as a pure and crystalline structure without faults . Corma and co-workers reported higher turnover frequencies for Ti–BEC than Ti–BEA in the epoxidation of cyclic-alkenes, attributing the difference to the diffusion problems presented in BEA …”

Section: Introductionmentioning

confidence: 99%

DFT Study of Closed and Open Sites of BEA, FAU, MFI, and BEC Zeolites Substituted with Tin and Titanium

2016

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DFT with long-range corrections and ONIOM along with a polarizable-continuum model were used to analyze zeolites BEA, FAU, MFI, and BEC substituted with Sn and Ti. The preferential substitution sites for Ti and Sn in the different frameworks are reported. The Lewis acidities were measured through the NH 3 binding energies and through the charge transfer of NH 3 upon adsorption. The deprotonation energies of the open sites, which are proportional to the Brønsted acidities, and the hydrolysis energies are also reported. We also present the properties of BEA with a single and a double Sn-substitution to compare the active sites obtained with two methods commonly employed for the synthesis of Sn−BEA. Among the zeolites analyzed in this study, Sn−BEA with a double Sn-substitution has the highest Lewis acidity. The formation of open sites through the hydrolysis of Sn−BEA, Sn−FAU, and Ti−FAU is energetically favorable, but it is not favorable in MFI or Ti−BEA. On the basis of the deprotonation energies, the open sites of Sn−BEA have a strong Brønsted acidity, comparable to Al−BEA or Al−MFI. We also demonstrate that the VDW forces in the binding energies of NH 3 on MFI are more significant than in the other zeolite frameworks and that these forces decrease with increasing pore size.

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Section: Introductionmentioning

confidence: 99%

DFT Study of Closed and Open Sites of BEA, FAU, MFI, and BEC Zeolites Substituted with Tin and Titanium

2016

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“…BEC, owing to its ordered and crystalline structure, could overcome the diffusion problems exhibited in BEA. However, only a few studies have been reported in the literature on the use of BEC in catalysis. ,, Recently, Corma and Moliner demonstrated that BEC functionalized with titanium (Ti-BEC) performed better in terms of activity and selectivity than BEA functionalized with titanium (Ti-BEA) when cyclic compounds as cyclo-octene were tested for epoxidation reactions . BEC was synthesized for the first time as a germanium-silicate, showing poor hydrothermal stability, but recently, BEC has been synthesized as a pure silicate with a much higher hydrothermal stalibility …”

Section: Introductionmentioning

confidence: 99%

DFT Study of the Lewis Acidities and Relative Hydrothermal Stabilities of BEC and BEA Zeolites Substituted with Ti, Sn, and Ge

Montejo-Valencia

Curet-Arana

2015

J. Phys. Chem. C

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Metal-substituted beta-zeolites have proven to be effective catalysts for various important reactions involving the transformation of biomass-derived molecules. In this study, a combination of quantum mechanical calculations and integrated quantum mechanics−molecular mechanics along with a polarizable continuum model were used to determine the preferred substitution site of Sn, Ti, and Ge metals in zeolite beta (BEA) and in the polymorphism C of zeolite beta (BEC), as well as the Lewis acidity and the hydrothermal stability of the metalsubstituted zeolites. Our results demonstrate (1) the most favorable substitution of Ti, Ge, and Sn in BEC is in the T1 site; (2) Ti-BEC has Lewis acidity similar to that of Sn-BEA; (3) the hydrolysis of Ge-BEC is energetically favorable when the Ge/Si ratio is 1/13; and (4) Ti-substituted zeolites show the highest hydrothermal stability of the zeolites studied.

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“…Incorporation of Ti into the framework of zeolites has been shown to be useful in the catalytic epoxidation of olefins and the influence of various Ti precursors and Ti loadings on polymorph C, a member of the zeolite beta family, were examined by Lee and co-workers. 413 The paper discussed the synthesis and characterisation of the materials together with an evaluation of their catalytic activity using the epoxidation of cyclohexene. XRD analysis was employed to establish the crystallinities and the framework Ti content of the catalyst preparations, and the Si/Ti molar ratios were determined by ICP-OES.…”

Section: Oxidation Reactionsmentioning

confidence: 99%

Atomic spectrometry update. Industrial analysis: metals, chemicals and advanced materials

Carter

Fisher

Goodall

et al. 2010

J. Anal. At. Spectrom.

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Incorporation of titanium into polymorph C for catalytic epoxidation of cyclohexene

Cited by 8 publications

References 22 publications

DFT Study of Closed and Open Sites of BEA, FAU, MFI, and BEC Zeolites Substituted with Tin and Titanium

DFT Study of Closed and Open Sites of BEA, FAU, MFI, and BEC Zeolites Substituted with Tin and Titanium

DFT Study of the Lewis Acidities and Relative Hydrothermal Stabilities of BEC and BEA Zeolites Substituted with Ti, Sn, and Ge

Atomic spectrometry update. Industrial analysis: metals, chemicals and advanced materials

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