Niobium sulfide as a dopant for hydrotreating NiMo catalysts

Niobium sulfide has been recently found to be an interesting new active pha se for hydrodesulfurization. In this work, niobium was used as a dopant for a conventional hydrotreating catalyst. A NiMo hydrotreating catalyst in th e oxide form was doped with various contents of Nb precursor salt (0<Nb wt, %<7). After drying, the activation of the catalyst was performed with CS2 sulfiding agent in a high pressure vessel. The use of this new dopant incre ased the catalytic activity in both HDS and HYD model reactions. Highest ac tivities were obtained with an optimum Nb content of 5 wt,%, The selectivit y of the products was also modified since more isomerized compounds where p roduced. Various techniques were used to determine structural and morpholog ical characteristics of the materials. TEM pictures only showed the presenc e of lamellar particles similar to MoS2, EDX analysis demonstrated the homo geneous distribution of the transition metal elements (Ni, Mo, Nb) even wit h small electron probes at high magnification. EXAFS was used to determine the local environment of Nb atoms and showed that Nh was present in the for m of "NbS2" entities similar to the bulk phase. (C)2000 Elsevier Science B. V. All rights reserved.