Catalytic Properties of ZSM-5 Zeolites in N 2O Decomposition: The Role of Iron

• Published in: Journal of catalysis 1993, Vol.139 (2), p.435-443
• Main Authors: Sobolev, V.I., Panov, G.I., Kharitonov, A.S., Romannikov, V.N., Volodin, A.M., Ione, K.G.
• Format: Article
• Language: English
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1006/jcat.1993.1038

Ferrisilicate analogues of ZSM-5 zeolite have been found to be efficient catalysts for direct oxidation of benzene to phenol using dinitrogen monoxide as an oxidant. The reaction of N 2O decomposition over these catalysts has now been studied. Specific active sites (referred to as α-sites) consisting of Fe atoms have been shown to be responsible for catalytic properties of ferrisilicates. Decomposition of N 2O on α-sites generates a reactive form of surface oxygen which cannot be produced by O 2 adsorption. The concentration of α-sites and the rate of N 2O decomposition as functions of iron content over the wide range of its concentrations (from 0.003 to 4.8 wt% Fe 2O 3) have been studied. When comparing these data with the previous results for ZSM-5 zeolites of ferrialuminosilicate composition, the properties of α-sites have been shown to be identical in both systems. The superior activity of Fe-Al-Si samples to that of Fe-Si samples is accounted for by a higher concentration of α-sites in the former at the same iron content, caused by the favourable influence of Al on Fe distribution throughout the zeolite matrix.