IRON SPECIES IN FEOX/ZRO2 AND FEOX/SULPHATED-ZRO2 CATALYSTS

Iron containing catalysts were prepared by (i) impregnation of ZrO2 with aqueous solutions of Fe(NO3)3, Fe/Zi, or aqueous solutions of NH4Fe(SO4)2, FeS/Z; (ii) chemical vapour deposition of FeCl3 on ZrO2, Fe/ZCVD; and (iii) impregnation of sulphated-ZrO2 with toluene solutions of Fe(acetylacetonate)3, Fe/SZ. After drying at 383 K and calcining at 823 K, samples were characterized by temperature programmed reduction with H2 and Fourier transformed IR spectroscopy. The FTIR characterization by CO adsorption evidenced the formation of various carbonyl-like species onto Fen + sites (0 ≤ n ≤ 3). The relative amount of the various iron carbonyl-like species depended not on the iron content, but on the catalyst preparation method. The H2-TPR experiments showed that iron species were much less reducible in FeOx/sulphated-ZrO2 than in FeOx/ZrO2. Their lower reducibility explains why FeOx/sulphated-ZrO2 samples achieve higher selectivity for the selective catalytic reduction of NO with hydroca