XPS Characterization of Carbon Nanotube Supported CoMo Hydrodesulfurization Catalysts

In this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co-Mo catalysts is studied by XPS. After sulfidation with in-situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(Ⅳ) in MoS2 phase, and the rest to Mo(Ⅴ) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-. In case of CoMo/γ-Al2O3 catalyst sulfided with in-situ method, a fraction of molybdenum is transferred to formal state Mo(Ⅳ) in the form of MoS2, but there is still a mount of unreduced Mo(VI) phase which is difficult to be sulfided. In CoMo/CNT catalyric system sulfided with ex-situ method, Mo(IV) in the form of MoS2 is detected along with a portion of unreduced Mo(VI) phase, suggesting that not all the Mo phases are reduced and sulfided by ex-situ method. As for CoMo/γ-Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(V) which consists of Mo coordinated both to O and S, such as MoO2S2^2- and MoO3S^2-, in addition, there is still a fraction of unreduced Mo(Ⅵ)phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/γ-Al2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.

XPS Characterization of Carbon Nanotube Supported CoMo Hydrodesulfurization Catalysts

In this paper, the effect of catalytic support and sulfiding method on the chemical state of supported Co-Mo catalysts is studied by XPS. After sulfidation with in-situ method, the majority of molybdenum in CNT supported CoMo catalyst is transferred to a species with a formal chemical state Mo(IV) in MoS2 phase, and the rest to Mo(V) which consists of Mo coordinated both to O and S, such as MoO2S2-2 and MoO3S2-. In case of CoMo/-Al2O3 catalyst sulfided with in-situ method, a fraction of molybdenum is transferred to formal state Mo(IV) in the form of MoS2, but there is still a mount of unreduced Mo(VI) phase which is difficult to be sulfided. In CoMo/CNT cata-lytic system sulfided with ex-situ method, Mo(IV) in the form of MoS2 is detected along with a portion of unre-duced Mo(VI) phase, suggesting that not all the Mo phases are reduced and sulfided by ex-situ method. As for CoMo/-Al2O3, a portion of molybdenum is sulfided to intermediate reduced state Mo(V) which consists of Mo co-ordinated both to O and S, such as MoO2S2-2 and MoO3S2-, in addition, there is still a fraction of unreduced Mo(VI) phase. XPS analyses results suggest that CNT support facilitates the reduction and sulfidation of active species to a large extent, and that alumina support strongly interacts with active species, hereby producing a fraction of phase which resists complete sulfiding. Catalytic measurements of catalysts in the HDS of dibenzothiophene (DBT) show that CoMo/CNT catalysts are of higher HDS activity and selectivity than CoMo/-Al2O3 catalyst, which is in good relation with the sulfiding behavior of the corresponding catalyst.