Iron containing catalysts were prepared by (i) impregnation of ZrO2 with aqueous solutions of Fe(NO3)(3), Fe/Z(i), or aqueous solutions of NH4Fe(SO4)(2), FeS/Z; (ii) chemical vapour deposition (CVD) of FeCl3 on ZrO2, Fe/Z(CVD); and (iii) impregnation of sulphated-ZrO2 with toluene solutions of Fe(acetylacetonate)(3), Fe/SZ. After calcining at 823 K, samples were characterised by temperature-programmed reduction with H-2 and Fourier transformed IR spectroscopy. NO reduction with C3H6 in the presence of excess O-2 was studied in a flow apparatus fed by a reactant mixture of NO:C3H6:O-2 = 2000 ppm:2000 ppm (or 2700 ppm):20,000 ppm in He. FTIR characterisation by CO adsorption showed that various carbonyl-like species formed on Fen+ sites (0 <= n < 3). Their relative amounts depended not on the iron content, but on the catalyst preparation method. The reducibility of Fe-III to Fe-II in H-2 increased in the order FeS/Z < Fe/Z(CVD) < Fe/Z(i). In the C3H6 + O-2 reaction, the catalytic activity for C3H6 oxidation increased in parallel with the reducibility. In the NO + C3H6 + O-2 reaction, the selectivity to CO2 (rather than to CO) increased in parallel with the reducibility. By contrast, the selectivity of C3H6 towards NO rather than 02 increased in the reverse order. These results suggest that the catalytic activity and selectivity of the various samples depend on the chemical behaviour of the Fe-III/Fe-II redox couple. (c) 2005 Elsevier B.V. All rights reserved.