Peculiarities of Catalytic Oxidation of Ethane by Nitrous Oxide on ZSM-5 Type Zeolites Containing Iron Ions in Different Localization Sites

The temperature dependence of the Fe-HZSM-5 activity and selectivity in the process of catalytic oxidation of ethane by the excess of N2O at 250–350°C exhibits a pronounced hysteresis. The oxidized catalysts free from condensation products are active only in the complete oxidation of ethane. At low temperatures of the reaction of the C2H6 + N2O mixture with the catalyst, coke formation takes place and the coordination state of iron ions differs from the initial sample. Under these conditions, the process of complete oxidation of ethane is essentially suppressed and the process of oxidative dehydrogenation dominates. The catalytic properties of iron-containing zeolites prepared either by direct synthesis or by introduction of iron ions into the cationic positions of H[Al]ZSM-5 are quite similar, because irreversible formation of new iron species considerably different from the initial species takes place during the catalytic reaction on both series of samples. The activity of HZSM-5 containing trace amounts of iron is much lower than that of iron-containing samples.