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Application of MII 2MV 2(acac)2(OMe)12 Derivatives in Sol-Gel Preparation of Oxide and Oxide Nanocomposite Materials for Catalysis
Authors:Pia Werndrup  Vadim G. Kessler
Abstract:
Hydrolysis of MII2MV2(acac)2(OMe)12, MII=Co or Ni and MV=Nb or Ta, in dry toluene, subsequent evaporation of the solvent, and heating to 500°C, provides access to a catalytically active oxide. The thermogravimetry (TG) analyses of the thermal behaviour of the hydrolysed alkoxides show three distinct steps. The first weight loss occurs at 120°C, the second at 390°C, and the third at 480°C. The weight is constant at 67% of original weight from 480 to 900°C. The powder X-ray patterns of the Co-Ta hydrolysed alkoxide show that powder heated to 500°C is amorphous but powder heated to 900°C revealed the presence of an equimolar mixture of CoIITa2O6 and Co4IITa2O9. Gelation and further transformation on thermal treatment were found to occur in the same way for Co2Ta2(acac)2(OMe)12, Ni2Ta2(acac)2(OMe)12, and Co2Nb2(acac)2(OMe)12.Interaction of Co2Ta2(acac)2(OMe)12 solution with NaY 12 Å zeolite was found to be an exothermic reaction providing access to a nanocomposite compound. The latter has been investigated with the aid of EXAFS spectroscopy. The interaction with NaY 12 Å zeolite was found to occur in the same way for Co2Nb2(acac)2(OMe)12.
Keywords:sol-gel  heterometallic alkoxides  cobalt alkoxides  precursor chemistry  EXAFS
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