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

Gold on iron oxides catalysts have been characterized by temperature programmed reduction (TPR) and X-ray diffraction spectroscopy (XRD). The influence of preparation method, gold loading and pretreatment conditions on the reducibility of iron oxides have been investigated. On the impregnated Au/iron 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 range. On the coprecipitated samples, the temperature of formation of Fe3O4 is strongly dependent on the presence of gold. The reduction temperature is lowered as the gold loading is increased. The reduction of Fe3O4 to FeO occurs at about 900 K and is not dependent on the presence of gold and the preparation method, It is suggested that the effect of gold on the reducibility of the iron oxides is related to an increase of the structural defects and/or of the surface hydroxyl groups.