Thermoanalytical characterization of molybdenum-based catalytic materials

Thermoanalytical techniques, especially temperature-programmed reduction (TPR), were employed for the characterization of oxidic precursors of molybdenum-based catalysts, sulfides derived from them, and three thiomolybdate compounds, employed as models or precursors of hydrodesulfurization atalysts. Correlations were found between TPR data and the presence of single and mixed oxides of Mo and Ni, Co or Fe, as demonstrated by XRD. The same phases and the thiomolybdates were shown to be present in supported catalytic precursors. Differences between the reducibilities of the mixed oxides of Ni-Mo, Co-Mo and Fe-Mo are easily appreciated from TPR, including those of the α- and β- polymorphic modifications of NiMoO₄.