Presulfidation and activation mechanism of Mo/Al2O3 catalyst sulfided by ammonium thiosulfate

Mo/Al 2 O 3 catalyst was presulfided with (NH 4 ) 2 S 2 O 3 to elucidate presulfidation and activation mechanism. It is illustrated that the Mo oxide is firstly partially sulfided during presulfidation and then in situ reduced into MoS 2− x in activation, and finally sulfided to active state during hydrodesulfurization (HDS). A synergistic effect between the S 2− and S 6+ ions in (NH 4 ) 2 S 2 O 3 produces a positive influence on the HDS performance. The S 2− ions contribute to the sulfidation of Mo ions, while the S 6+ species interact with Al 2 O 3 support, weakening the interaction of active species with support.