The effect of treatment with triethylaluminium on the hydrogenation and hydrodesulfurization activity of molybdenum, cobalt, and nickel sulfide catalysts

Abstract

The activities for hydrogenation of hex-1-ene (1 atm, 573 K) and hydrodesulfurization (hds) of thiophene (1 atm, 673 K) of alumina-supported molybdenum, cobalt, and nickel sulfide catalysts, and a sulfided Co-Mo γ- Al 2O 3 catalyst have been measured before and after treatment of the catalyst with triethylaluminium (AlEt 3). The triethylaluminium treatment (a) increased the hex-1-ene hydrogenation activity of the individual sulfides; (b) decreased the hex-1-ene hydrogenation activity of the sulfided Co-Mo γ- Al 2O 3 ; (c) increased the thiophene hds activity of sulfided Mo γ- Al 2O 3 ; (d) decreased the thiophene hds activity of the other catalysts and loss of promoting effect of Co on sulfided Mo in the sulfided Co-Mo γ- Al 2O 3 catalyst. The hydrogenation activities of the catalysts decreased after they had been used for hds. The AlEt 3 treatment of the catalysts also caused changes in their electron spin resonance spectra which are attributed to reduction of oxidic Mo(V) to oxidic Mo(III) and sulfided Co(II) to sulfided Co(I). The work provides additional evidence that the active species is a Mo(IV) sulfide promoted by Co(II).