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Regio- and Stereoselective Terpene Epoxidation using Tungstate-exchanged Takovites: a study of phase purity, takovite composition and stable catalytic activity

(2009) PHYSICAL CHEMISTRY CHEMICAL PHYSICS. 11(16). p.2964-2975
Author
Organization
Abstract
Nanocrystalline tungstate-exchanged layered double hydroxides of the takovite type, [NixAl1-x(OH)(2)](NO3)(0.9-x)(WO4)(0.05)center dot mH(2)O, have been prepared with changing values of x. The morphology-texture parameters of the synthesized materials were characterized by using scanning electron microscopy and nitrogen adsorption techniques. X-Ray diffraction, diffuse reflectance spectroscopy, Al-27 MAS NMR and infrared spectroscopy were applied to study the structure and the phase purity of the tungstate exchanged materials. Identification of the tungsten state was attempted by infrared and Raman spectroscopy. The catalytic properties of the pure tungstate exchanged takovites were tested in the bromide-assisted epoxidation of terpenic olefins using H2O2 as environmental benign oxidant. The bromide-assisted oxidation shows very interesting chemo-selectivity for various substrates with unique regio- and stereo-selectivity often opposite to that of many traditional methods. The activity of the tungstate catalyst was observed to highly depend on the Al content in the takovite support, most likely due to efficient charge shielding at the catalyst's surface. Tungstate exchanged on Al-rich takovite has a remarkable oxidation activity in terms of turnover frequency. Moreover, the takovite catalyst was found to be stable under reaction conditions and recyclable.
Keywords
HETEROGENEOUS CATALYST, REGIOSELECTIVE EPOXIDATION, O-1(2) GENERATION, LAYERED DOUBLE HYDROXIDES, HYDROGEN-PEROXIDE, MILD OXIDATIVE BROMINATION, AQUEOUS-SOLUTIONS, SINGLET OXYGEN, 1ST EXAMPLE, ANIONIC CLAYS

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MLA
Levecque, Pieter et al. “Regio- and Stereoselective Terpene Epoxidation Using Tungstate-exchanged Takovites: a Study of Phase Purity, Takovite Composition and Stable Catalytic Activity.” PHYSICAL CHEMISTRY CHEMICAL PHYSICS 11.16 (2009): 2964–2975. Print.
APA
Levecque, P., Poelman, H., Jacobs, P., De Vos, D., & Sels, B. (2009). Regio- and Stereoselective Terpene Epoxidation using Tungstate-exchanged Takovites: a study of phase purity, takovite composition and stable catalytic activity. PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 11(16), 2964–2975.
Chicago author-date
Levecque, Pieter, Hilde Poelman, Pierre Jacobs, Dirk De Vos, and Bert Sels. 2009. “Regio- and Stereoselective Terpene Epoxidation Using Tungstate-exchanged Takovites: a Study of Phase Purity, Takovite Composition and Stable Catalytic Activity.” Physical Chemistry Chemical Physics 11 (16): 2964–2975.
Chicago author-date (all authors)
Levecque, Pieter, Hilde Poelman, Pierre Jacobs, Dirk De Vos, and Bert Sels. 2009. “Regio- and Stereoselective Terpene Epoxidation Using Tungstate-exchanged Takovites: a Study of Phase Purity, Takovite Composition and Stable Catalytic Activity.” Physical Chemistry Chemical Physics 11 (16): 2964–2975.
Vancouver
1.
Levecque P, Poelman H, Jacobs P, De Vos D, Sels B. Regio- and Stereoselective Terpene Epoxidation using Tungstate-exchanged Takovites: a study of phase purity, takovite composition and stable catalytic activity. PHYSICAL CHEMISTRY CHEMICAL PHYSICS. ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND; 2009;11(16):2964–75.
IEEE
[1]
P. Levecque, H. Poelman, P. Jacobs, D. De Vos, and B. Sels, “Regio- and Stereoselective Terpene Epoxidation using Tungstate-exchanged Takovites: a study of  phase purity, takovite composition and stable catalytic activity,” PHYSICAL CHEMISTRY CHEMICAL PHYSICS, vol. 11, no. 16, pp. 2964–2975, 2009.
@article{662489,
  abstract     = {{Nanocrystalline tungstate-exchanged layered double hydroxides of the takovite type, [NixAl1-x(OH)(2)](NO3)(0.9-x)(WO4)(0.05)center dot mH(2)O, have been prepared with changing values of x. The morphology-texture parameters of the synthesized materials were characterized by using scanning electron microscopy and nitrogen adsorption techniques. X-Ray diffraction, diffuse reflectance spectroscopy, Al-27 MAS NMR and infrared spectroscopy were applied to study the structure and the phase purity of the tungstate exchanged materials. Identification of the tungsten state was attempted by infrared and Raman spectroscopy. The catalytic properties of the pure tungstate exchanged takovites were tested in the bromide-assisted epoxidation of terpenic olefins using H2O2 as environmental benign oxidant. The bromide-assisted oxidation shows very interesting chemo-selectivity for various substrates with unique regio- and stereo-selectivity often opposite to that of many traditional methods. The activity of the tungstate catalyst was observed to highly depend on the Al content in the takovite support, most likely due to efficient charge shielding at the catalyst's surface. Tungstate exchanged on Al-rich takovite has a remarkable oxidation activity in terms of turnover frequency. Moreover, the takovite catalyst was found to be stable under reaction conditions and recyclable.}},
  author       = {{Levecque, Pieter and Poelman, Hilde and Jacobs, Pierre and De Vos, Dirk and Sels, Bert}},
  issn         = {{1463-9076}},
  journal      = {{PHYSICAL CHEMISTRY CHEMICAL PHYSICS}},
  keywords     = {{HETEROGENEOUS CATALYST,REGIOSELECTIVE EPOXIDATION,O-1(2) GENERATION,LAYERED DOUBLE HYDROXIDES,HYDROGEN-PEROXIDE,MILD OXIDATIVE BROMINATION,AQUEOUS-SOLUTIONS,SINGLET OXYGEN,1ST EXAMPLE,ANIONIC CLAYS}},
  language     = {{eng}},
  number       = {{16}},
  pages        = {{2964--2975}},
  publisher    = {{ROYAL SOC CHEMISTRY, THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}},
  title        = {{Regio- and Stereoselective Terpene Epoxidation using Tungstate-exchanged Takovites: a study of 	phase purity, takovite composition and stable catalytic activity}},
  url          = {{http://dx.doi.org/10.1039/b820336a}},
  volume       = {{11}},
  year         = {{2009}},
}

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