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Heterogeneous Wheel‐Shaped Cu 20 ‐Polyoxotungstate [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25− Catalyst for Solvent‐Free Aerobic Oxidation of n ‐Hexadecane
Author(s) -
Chen Lifang,
Hu Juncheng,
Mal Sib Sankar,
Kortz Ulrich,
Jaensch Helge,
Mathys Georges,
Richards Ryan M.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200900031
Subject(s) - catalysis , hydrogen peroxide , heterogeneous catalysis , adsorption , chemistry , alkyl , infrared spectroscopy , homogeneous catalysis , solvent , inorganic chemistry , fourier transform infrared spectroscopy , chemical engineering , organic chemistry , engineering
The selective oxidation of alkanes as a green process remains a challenging task because partial oxidation is easier to achieve with sacrificial oxidants, such as hydrogen peroxide, alkyl hydroperoxides or iodosylbenzene, than with molecular oxygen or air. Here, we report on a heterogeneous catalyst for n ‐hexadecane oxidation comprised of the wheel shaped Cu 20 ‐polyoxotungstate [Cu 20 Cl(OH) 24 (H 2 O) 12 (P 8 W 48 O 184 )] 25− anchored on 3‐aminopropyltriethoxysilane (apts)‐modified SBA‐15. The catalysts were characterized by powder X‐ray diffraction (XRD), N 2 ‐adsorption measurements and Fourier transform infrared reflectance (FT‐IR) spectroscopy. The heterogeneous Cu 20 ‐polyanion system catalyzed the solvent‐free aerobic oxidation of n ‐hexadecane to alcohols and ketones by using air as the oxidant under ambient conditions. The catalyst exhibits an exceptionally high turn over frequency (TOF) of 20 000 h −1 at 150 °C and is resistant to poisoning by CS 2 . Moreover, it can be easily recovered and reused by filtration without loss of its catalytic activity. Possible homogeneous contributions also have been examined and eliminated. Thus, this system can use air as oxidant, which, in combination with its good overall performance and poison tolerance, raises the prospect of this type of heterogeneous catalyst for practical applications.