STUDY OF THE NOX REACTION WITH REDUCING GASES ON FE ZRO2 CATALYST/

The Fe/ZrO2 catalyst (1% Fe by weight) shows a strong adsorption capac ity toward the nitric oxide (at room temperature the ratio NO/Fe is ca . 0.5) as a consequence of the formation of a highly dispersed iron ph ase after reduction at 500-773 K. Nitric oxide is adsorbed mainly as n itrosyl species on the reduced surface where the Fe2+ sites are prevai ling, but it is easily oxidised by oxygen forming nitrito and nitrate species adsorbed an the support. However, in the presence of a reducin g gas such as hydrogen, carbon monoxide, propane and ammonia at 473-57 3 K the Fe-nitrosyl species react producing nitrogen, nitrous oxide, c arbon dioxide and water, as detected by FTIR and mass spectrometers, T he results show that nitric oxide reduction is more facile with hydrog en containing molecules than with CO, probably due the co-operation of spillover effects. Experiments carried out with the same gases in the presence of oxygen show, however, a reduced dissociative activity of the surface iron sites toward the species NOx formed by NO oxidation a nd therefore the reactivity is shifted to higher temperatures.