Modification of surface and catalytic properties of Fe_2O_3 due to doping with rare-earth oxides Sm_2O_3 and Y_2O_3

摘要

The effects of Sm_2O_3 and Y_2O_33 doping of Fe_2O_3 on its surface and catalytic properties were investigated using nitrogen adsorption at -196 deg C,oxidation of CO by O_2 at 225-275 deg C and decomposition of H2O2 at 30-50 deg C.Fe_2O_3 was prepared by thermal decomposition of ferric carbonate at 350 deg C.The treated ferric oxide solid was prepared by wet impregnation method using finely powdered Fe2(CO_3)_3 solid followed by doping with different amounts of samarium nitrate or yttrium nitrate.Pure and doped Fe_2O_3 solids were calcined at 350-650 deg C.The extent of dopant added was varied between 1.0 and 6.0mol%.The results obtained revealed that doping of Fe_2O_3 solids with different amounts of Sm_2O_3 and Y_2O_3 decreased the degree of crystallinity and particle size of Fe_2O_3 phase.This doping process led to a progressive increase in the specific surface area of the treated Fe_2O_3 solids to an extent proportional to the amount of Sm_2O_3 and Y_2O_3 added.The doping process led also to a progressive increase in the catalytic activities of the investigated solids towards CO oxidation by O_2 and H_2O_2 decomposition.Also,the doping process did not modify the mechanism of the catalytic reactions but increased the concentration of catalytically active sites involved in the catalyzed reactions.