Synergism Between Ni and W in the Ni-W/C Sulfide Catalyst in Hydrodenitrogenation of Pyridine and Hydrodesulfurization of Thiophene

Abstract

Parallel hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene was studied over active-carbon-supported Ni, W, and Ni-W sulfide catalysts at 2 MPa and at 280 and 320 °C. Synergism between Ni and W was observed both in HDN and HDS reactions: the activity of the Ni-W catalyst was higher than the sum of the activities of the Ni and W catalysts. However, the synergistic increase in activity was much higher in HDS than in HDN. This led to a characteristic shift in the HDN/HDS selectivity, which was strongly shifted to the HDS side over the Ni-W catalysts as compared with the Ni and W catalysts. HDS was faster than HDN over the Ni-W catalyst, the rate of both reactions being about the same over the Ni catalyst and HDN being faster than HDS over the W catalyst. The selectivity of all the catalysts was shifted to the HDN side with decreasing temperature. The data are a new example for generalisation of the rule that the synergism in activity of bimetallic sulfide Co-Mo, Ni-Mo, and Ni-W catalysts is higher in HDS than in hydrogenation and HDN.