Au iron oxide catalysts: temperature programmed reduction and X-ray diffraction characterization

Gold on iron oxides catalysts have been characterized by temperature progra mmed reduction (TPR) and X-ray diffraction spectroscopy (XRD). The influenc e of preparation method, gold loading and pretreatment conditions on the re ducibility of iron oxides have been investigated. On the impregnated Au/iro n oxide catalysts as well as on the support alone the partial reduction of Fe(III) oxy(hydroxides) to Fe3O4 starts in the 550 and 700 K temperature ra nge. On the coprecipitated samples, the temperature of formation of Fe3O4 i s strongly dependent on the presence of gold. The reduction temperature is lowered as the gold loading is increased. The reduction of Fe3O4 to FeO occ urs at about 900 K and is not dependent on the presence of gold and the pre paration method, It is suggested that the effect of gold on the reducibilit y of the iron oxides is related to an increase of the structural defects an d/or of the surface hydroxyl groups. (C) 1999 Elsevier Science B.V. All rig hts reserved.