Nickel-molybdenum/gamma-alumina catalysts for simultaneous hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine

Supported and unsupported Ni-Mo catalysts with different metal loadings were systematically studied in order to optimize the catalyst composition for simultaneous hydrodesulfurization of thiophene and hydrodenitrogenation of pyridine. Activity measurements were done in a flow microreactor, which was operated at atmospheric pressure for HDS experiments, and at 100 psig for HDN or simultaneous HDS/HDN experiments. All catalyst samples were characterized using BET surface area measurements, x-ray diffraction, and laser Raman spectroscopy. The optimal composition was found to be around 3% NiO and 15% MoO{dollar}sb3{dollar} deposited on {dollar}gamma{dollar}-Al{dollar}sb2{dollar}O{dollar}sb3{dollar}. These experiments showed the non-existence of synergism in the HDN of pyridine. They also showed that either thiophene or H{dollar}sb2{dollar}S accelerates the piperidine hydrogenolysis reaction rate during simultaneous HDS/HDN experiments.; Temperature programmed desorption, and temperature programmed reduction experiments were carried out on three of the supported catalysts (10 wt. % NiO, 20 wt. % MoO{dollar}sb3{dollar}, 15 wt. % MoO{dollar}sb3{dollar} plus 3 wt. % NiO), and bare alumina. TPD of hydrogen sulfide experiments showed that each catalysts have a characteristic TPD curve, and that TPD profile for Ni-Mo catalysts does not correspond to simple combination of the Ni and Mo catalysts profiles. TPR studies showed that the sulfide catalysts have a characteristic reduction curve, and that the addition of nickel to a molybdenum catalysts increases the amount of easily reducible species. TPD and TPR experiments after HDS and HDN experiments indicated that thiophene and pyridine are adsorbed very strongly on the surface of the catalysts, and that the catalysts are more difficult to reduce after thiophene HDS experiments, and even more difficult to reduce after pyridine HDN experiments.