The catalytic properties of ferric ions introduced in MFI-type zeolites were investigated for redox reactions in view of their chemical environment. The catalysts used were MFI-ferrisilicate with isolated Fe3+ in tetrahedral coordination. iron oxide supported on MFI-silicalite (FeO2/sil) with Fe3+ in octahedral coordination, and Fe3+-exchanged ZSM-5 (FeZSM-5). The specific activity of Fe3+ for oxidation of CO with O2 decreased in the order: FeO2/sil>FeZSM-5>ferrisilicate. The low activity of ferrisilicate was explained by the low reactivity of its lattice oxygen for oxidizing CO. Ferrisilicate exhibited higher selectivity for the oxidative dehydrogenation of alkene into alkene than FeO2/sil and FeZSM-5. The low activity for the secondary reaction of initially produced alkene as well as for the direct oxidation of alkane into carbon oxides resulted in the high selectivity of ferrisilicate. In the case of the reduction of NO with NH3;. ferrisilicate and FeZSM-5 catalyzed the reaction with high selectivity in the presence of oxygen, while FeO2/sil catalyzed the reaction in the absence of oxygen. In the presence of oxygen, FeO2/sil catalyzed the oxidation of NH3 into NO in retard the reduction of NO. The chemical environment of Fe3+ ions may correspond to the reactivity of lattice oxygen around the ions, which can be visualized as catalytic properties in redox reactions.
|Number of pages||11|
|Journal||Sekiyu Gakkaishi (Journal of the Japan Petroleum Institute)|
|Publication status||Published - Jan 1 1996|
ASJC Scopus subject areas
- Fuel Technology
- Energy Engineering and Power Technology