Niobium-Based Nickel-Tungsten Hydrotreatment Catalysts with Enhanced Isomerization Properties

Alumina-supported NiW catalysts doped with Nb were prepared with different W contents and different Ni/W ratios. Studies of the sulfide state by TEM and X-ray photoelectron spectroscopy (XPS) demonstrated the influence of Nb on the sulfidation of W and Ni. The catalytic performance of the solids was evaluated in toluene hydrogenation and cyclohexane isomerization and was compared to that of Nb-free catalysts. The presence of Nb resulted in a decrease of the hydrogenation activity at low W content and low Ni/W ratio, in agree-ment with XPS and TEM characterizations. However, increasing the W content and the Ni/W ratio increased the hydrogenation activity. Regardless of the W and Ni content, cyclohexane conversion was significantly improved by the presence of Nb. The most efficient catalyst of the series, with a W content of 15 wt% WO3 and a Ni/W ratio of 0.9, showed slightly higher activity for hydrogenation than that of a Nb-free NiW catalyst. Also, the isomerization activity was greatly enhanced, demonstrating the potential of these Nb-based catalyst formulations.