Transition metal containing mesoporous silicas - redox properties, structure and catalytic activity

Mesoporous silicas of the MCM-41 type, containing iron, were prepared by sy nthesis and after framework synthesis, including deposition of iron from dr ied methanolic solution of iron(III) nitrate. Concentration of iron was up to 12 wt.%. In situ EXAFS, NO adsorption followed by IR spectroscopy and te mperature programmed reduction suggest that the resulting iron in most case s is present mainly in the form of isolated iron entities. Depending on the preparation procedures, subtle differences in bonding of iron to the frame work were observed. In the oxidation of large hydrocarbons to oxygenates wi th N2O the most active catalysts are aluminium containing materials. The ma in difference between FeZSM-5 and FeMCM-41 materials is the presence of Fe- O nanoclusters in FeZSM-5 which seem to be more active in the oxidation rea ction than isolated iron entities in mesoporous materials. (C) 2001 Elsevie r Science B.V. All rights reserved.