Reaction of thiophene with mono- and bimetallic Ni–Co particles supported on γ-Al 2O 3 and HDS activities of obtained sulfides

Abstract

Reaction between thiophene and M/γ-Al 2O 3 (20 wt.%, M = Ni, Co, 2Ni–Co and 2Co–Ni) was studied by thermal gravimetric analysis (TGA) and by sulfidation in a fixed bed microreactor. The samples were prepared by incipient wetness impregnation followed by drying and reduction in hydrogen flow at 450 °C. Formation of bimetallic particles in samples containing both Ni and Co was confirmed by HRTEM with EDX analysis. The reaction with thiophene (20 or 40 mbar) was done at 360 °C in hydrogen atmosphere. TGA of the reaction with thiophene revealed that the initial rate of sulfidation drops sharply when going from Ni/γ-Al 2O 3 to Co/γ-Al 2O 3 (by a factor of 40 under used conditions). It follows from the sulfidation in a fixed bed reactor that this difference can be attributed to a poor catalytic activity of metallic Co in thiophene hydrodesulfurization (HDS) and consequently much lower amount of produced H 2S in comparison with Ni. Upon sulfidation the HDS activity of Ni-rich particles progressively decreases, while, surprisingly, that of Co-rich particles is enhanced so that after a complete sulfidation (confirmed by XRD and sulfur analysis) the catalytic activity of the obtained sulfides in thiophene HDS increases in the order: 2Ni–Co < Ni < 2Co–Ni < Co.