Synthesis of a Mo/Nb mixed carbide

Molybdenum and niobium carbides (β−Mo2C, NbC), as well as mixed carbides of molybdenum and niobium, were synthesized by the temperature-programmed carburization method (TPC) using a 20 vol% CH4/H2 gas mixture. The starting materials were MoO3, B-Nb2O5, and physical mixtures of B-Nb2O5/MoO3 with Nb/(Nb + Mo) atomic ratios varying from 0.2 to 0.8, respectively. Results from catalytic and temperatureprogrammed oxidation (TPO) measurements indicate that during the carburization of the Nb2O5/MoO3 physical mixture with Nby(Nb + Mo) = 0.8 there is, besides β−Mo2C and NbC formation, the appearance of a carbidic phase not detectable by x-ray diffraction (XRD). This phase appears to be highly active and selective for the dibenzothiophene hydrodesulfurization (HDS) reaction.