Abstract: A series of hydrodesulfurization catalysts modified by H2SO4, Ni (NO3)2, Ni (NO3)2-H2SO4, NiSO4, respectively were prepared by the incipient wet impregnation method with γ-Al2O3 as carrier. The effects of sulfate radical on the physicochemical properties and thiophene selective HDS performance were studied by XRD, BET, H2-TPR, FT-IR, XPS and UV Raman spectroscopy. The HDS performance was tested in a small fixed bed using cyclohexane solution containing thiophene and isopentene as feedstock. The results showed that the hydrodesulfurization activity and selectivity of Ni/γ-Al2O3 modified with sulfate radical was better than the one modified with Ni(NO3)2; the catalyst prepared with nickel sulfate showed the highest activity and selectivity, 19 percentage points and 78% higher than the catalyst from nickel nitrate, respectively. The differences in catalytic activity were associated with the form of Ni in the catalyst, the presence of sulfate radical, on the one hand, weakens the interaction between the Ni and carrier, on the other hand, provides the sulfide agent for sulfidation of Ni in situ to form nickel sulfide. Both nickel sulfide and NiSO4 form the reactive center of catalysts, its activity and selectivity for HDS is significantly higher than the catalyst sulfided by introduction of sulfidation agent.

Key words: sulfate radical, Nickel sulfate, nickel nitrate, hydrodesulfurization, alumina, selectivity