Development of new NiMo/γ-alumina catalysts doped with noble metals for deep HDS

In the present work, with the aim of searching for new, highly effective catalysts for deep HDS, conventional NiMo/gamma-Al(2)O(3) catalysts were modified by the incorporation of small amounts (1 wt.%) of noble metals (NM = Pt, Pd, Ru) in order to increase their hydrogenation ability. Prepared catalysts were characterized in oxide state by N(2) physisorption, XRD, UV-vis DRS, temperature-programmed reduction and SEM-EDX, and in sulfided state by HRTEM. The catalysts were tested in the 4,6-dimethyldibenzothiophene (4,6-DMDBT) hydrodesulfurization. Results from the catalytic activity tests showed that the nature of the noble metal influences the catalytic performance of trimetallic NMNiMo catalysts supported on alumina. In general, doping of the conventional NiMo/gamma-Al(2)O(3) catalyst by all noble metals used resulted in an enhancement of the HYD route of 4,6-DMDBT hydrodesulfurization, especially in the case of the Ru-modified sample. However, if Pt and Pd-containing ternary catalysts showed activity 10-20% higher than the reference conventional NiMo/gamma-Al(2)O(3) sample, Ru addition had a negative effect on the overall catalytic activity. The activity of PdNiMo and PtNiMo/gamma-Al(2)O(3) catalytic formulations seems to be close to the sum of the activities obtained over NM/gamma-Al(2)O(3) and NiMo/gamma-Al(2)O(3) counterparts. This means that there is no synergetic effect between noble metals and conventional NiMo/alumina catalysts. (C) 2009 Elsevier B.V. All rights reserved.