STUDY OF REDUCTION BEHAVIOURS OF MOLYBDENA ON MoO3/Al2O3, MoO3/TiO2 AND NiO-MoO3/TiO2 SYSTEMS BY XPS

The H-2 reduction behaviours of MoO3/Al2O3, MoO3/TiO2 and NiO-MoO3/TiO2 samples prepared by impregnation method were studied at various temperatures for different times by XPS technique. The record XPS spectra of Mo3d from those samples were treated by computer curve fitting program to measure the distribution of various molybdenum oxide species with different valence states. The results of computer fitting shows that there areMo(VI), Mo(V) and Mo(IV) on the all of reduced samples. However, after H-2 reductonin same way, the percentage of low valence species Mo(V) and Mo(IV) on the MoO3/TiO2 is much higher than on the MoO3/Al2O3 (Fig. 2). For example, after H-2 treatement at 500 degrees C for 2 hrs., Mo(IV) species on the surface of MoO3/TiO2 samples is about 60% and it is three times higher than what is found on the MoO3/Al2O3 sample. In addition, the reduction of molybdena on TiO2 support is much easier and faster than on Al2O3 support (Fig. 2). A detail discussion about the interaction between molybdena and carries was presented. It was suggested that TiO2 is certainly involved in the reduction and oxidation process of molybdenum oxide species on the surface of it.