CATALYTIC PROPERTIES OF ZSM-5 ZEOLITES IN N2O DECOMPOSITION - THE ROLE OF IRON

Ferrisilicate analogues of ZSM-5 zeolite have been foundto be efficient catalysts for direct oxidation of benzene to phenol using dinitrogen monoxide as an oxidant. The reaction of N2O 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 N2O on α-sites generates a reactive form of surface oxygen which cannot be produced by O2 adsorption. The concentration ofα-sites and the rate of N2O decomposition as functions of iron content over the wide range of its concentrations(from 0.003 to 4.8 wt% Fe2O3) 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 inthe former at the same iron content, caused by the favourable influence of Al on Fe distribution throughout the zeolite matrix. © 1993 Academic Press, Inc.