THERMOANALYTICAL CHARACTERIZATION OF MOLYBDENUM-BASED CATALYTIC MATERIALS

Thermoanalytical techniques, especially temperature-programmed reducti on (TPR), were employed for the characterization of oxidic precursors of molybdenum-based catalysts, sulfides derived from them, and three t hiomolybdate compounds, employed as models or precursors of hydrodesul furization atalysts. Correlations were found between TPR data and the presence of single and mixed oxides of Mo and Ni, Co or Fe, as demonst rated by XRD. The same phases and the thiomolybdates were shown to be present in supported catalytic precursors. Differences between the red ucibilities of the mixed oxides of Ni-Mo, Go-Mo and Fe-Mo are easily a ppreciated from TPR, including those of the alpha- and beta- polymorph ic modifications of NiMoO4.