Photoactive sites in commercial HZSM-5 zeolite with iron impurities: An UV Raman study

According to our previous report [G. Yan, X. Wang, X. Fu, D. Li, Catal. Today 93–95 (2004) 851], commercially available HZSM-5s with different Si/Al ratio and 0.017–0.057 wt% of iron impurity have shown good photocatalytic activity for ethylene oxidation. Their activity increased with the increase of iron content. In this paper, photoactive sites in these commercial HZSM-5 zeolites were studied by UV Raman spectroscopy. The results showed that the photocatalytic activity of HZSM-5s was well correlated with the amount of two types of isolated iron species. The iron oxide and hydroxide clusters dispersed on the zeolite surface were not photocatalytically active. The possible mechanism of the photocatalysis on zeolites was also discussed.