Metal Sulfides

Torres, Brenda; Berhault, Gilles; Chianelli, Russell R.

doi:10.1002/0471227617.eoc140.pub2

Cited by 3 publications

(3 citation statements)

References 139 publications

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“…Therefore, we conclude that the active sites created with the addition of Ni are intrinsically much more active than those in the nonpromoted catalysts. This suggests that the addition of Ni leads to the formation of the Ni–Mo–S phase, which is much more active than phase-pure MoS 2 . , In this Ni-promoted phase, Ni substitutes Mo cations at the perimeter of the MoS 2 slabs and, therefore, is also referred to as a decoration model. This improvement in the activity and concentration of active sites must be the cause of the notable decrease of poisoning of HDS by ammonia (the K NH 3 for Ni-MoS 2 catalysts are 1 order of magnitude smaller than those of MoS 2 catalysts).…”

Section: Discussionmentioning

confidence: 99%

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

et al. 2014

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MoS 2 and Ni-promoted MoS 2 catalysts supported on γ-Al 2 O 3 , siliceous SBA-15, and Zr-and Ti-modified SBA-15 were explored for the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of o-propylaniline (OPA). In all cases, OPA reacted preferentially via initial hydrogenation, and DBT was converted through direct sulfur removal. HDN and HDS activities of MoS 2 catalysts are determined by the dispersion of the sulfide phase. Ni promotion increased its dispersion and activity for DBT HDS and also increased the rate of HDN via enhancing the rate of hydrogenation. On nonpromoted MoS 2 catalysts, HDS was strongly inhibited by NH 3 , and the addition of Ni dramatically reduced this inhibiting effect. The conclusion is that HDS is proportional to the concentration of Mo and Ni on the edges of sulfide particles. In contrast, the direct hydrodenitrogenation of OPA occurs only on accessible Mo cations and, hence, decreases with increasing Ni substitution. The nature of the support influences the dispersion of the nonpromoted catalysts as well as the decoration degree of Ni on the edges of the Ni−Mo−S phase. Furthermore, the acidity of the support influences the acidity of the supported sulfide phase, which may play an important role in HDN.

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Section: Discussionmentioning

confidence: 99%

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

et al. 2014

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“…In general, sulfur exists as alkyl derivatives of thiophene, benzothiophene, and dibenzothiophene (DBT), where DBT and its derivatives are known to be the most potent sulfur-containing species to HDS. − Therefore, tuning the catalyst properties based on the HDS studies of the DBT and its derivatives is the common practice in catalyst development. − Cobalt- and nickel-doped MoS 2 -based catalysts are the most efficient and commonly used catalysts in industry . Despite the several decade long studies of the catalytic activities of MoS 2 -based catalysts, the nature and mechanistic details are still the subject of vigorous debate . However, it is generally accepted in the literature that both HDS performances of the Co- and Ni-impregnated MoS 2 -based catalysts, on thiophene derivatives, proceed through two competing pathways, direct desulfurization (DDS) and stepwise hydrogenation of the aromatic core followed by the subsequent sulfur removal (HYD). ,, Various synthetic strategies have been developed to enhance the performances of the MoS 2 -based catalysts, which include tuning the porous catalyst support structures that exhibit higher Mo dispersions, doping of the catalyst with heteroatoms that alter the acidity, and enhancing the metal support interactions .…”

Section: Introductionmentioning

confidence: 99%

Kinetic and Mechanistic Analysis of Dibenzothiophene Hydrodesulfurization on Ti-SBA-15–NiMo Catalysts

et al. 2018

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MoS 2 -based catalysts are the most commonly used systems for the hydrodesulfurization (HDS) process on an industrial scale. Different methods were employed to enhance the efficiency of the catalysts, which include changes in catalyst support and doping agents as well as tuning the dispersion of the MoS 2 phase using various synthetic techniques. In this work, we report the kinetic and mechanistic analysis of HDS of dibenzothiophene (DBT) for different NiMo-supported Ti-SBA-15 catalysts prepared by (1) direct single-pot (SP) synthesis and (2) impregnations of the NiMo phase into the Ti-SBA-15 support. Both methods were also repeated with and without the citric acid (CA) loading to achieve higher dispersion of the active metal sites. Kinetic modeling was performed to two "parallel−series" reactions of DBT, direct desulfurization (DDS) and hydrogenation (HYD), both leading to the final product of cyclohexylbenzene. Kinetic analysis reveals the considerable influence of the catalyst preparation methods to both steps of HDS of DBT. We found that apparent rate constants for DDS k 1 ′ are highly dependent upon the employed synthetic method, while the effect of CA has a high contribution to the apparent rate constants for the conversion of partially hydrogenated dibenzothiophene intermediate, k 4 ′.

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“…Addition of a cobalt or nickel promoter is necessary to achieve highly active catalytic systems for hydrodesulfurization (HDS). 1 The description of the promoted phase has been extensively studied since the 1970's leading to different proposals for explaining the promotion effect from Co or Ni. The first attempt to describe the promoted phase was formulated by Farragher and Cossee who considered that Co was localized at octahedral sites at the periphery of the edge planes of the MoS 2 layered phase in a so-called ''pseudo-intercalation'' position.…”

Section: Introductionmentioning

confidence: 99%

HRTEM and molecular modeling of the MoS₂–Co₉S₈interface: understanding the promotion effect in bulk HDS catalysts

Ramos

Berhault

Ferrer

et al. 2012

Catal. Sci. Technol.

143

100

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As environmental regulations increase, more selective transition metal sulfide (TMS) catalytic materials for hydrotreating applications are needed. Highly active TMS catalysts become more and more desirable triggering new interest for unsupported Co-promoted MoS 2 -based systems that have high volumetric activity as reported here. Contrary to the common observation for alumina-supported MoS 2 -based catalysts, we found in our previous studies with dibenzothiophene (DBT) hydrodesulfurization (HDS) that the catalytic activity is directly proportional to the increase of surface area of the sulfide phases (Co 9 S 8 and MoS 2 ) present in Co-promoted MoS 2 unsupported catalysts. This suggests that activity is directly connected with an increase of the contact surface area between the two sulfide phases. Understanding of the nature of the possible interaction between MoS 2 and Co 9 S 8 in unsupported catalytic systems is therefore critical in order to get a more generalized overview of the causes for synergy. This has been achieved herein through the detailed characterization by XRD, XPS, and HRTEM of the highly active Co 9 S 8 / MoS 2 catalyst resulting in a proposed model for a Co 9 S 8 /MoS 2 interface. This model was then subjected to a DFT analysis to determine a reasonable description of the surface contact region between the two bulk phases. Modelling of the interface shows the creation of open latent vacancy sites on Mo atoms interacting with Co and formation of direct Co-Mo bonds. Strong electron donation from Co to Mo also occurs through the intermediate sulfur atom bonded to both metals while an enhanced metallic character is also found. These changes in coordination and electronic properties are expected to favor a synergetic effect between Co and Mo at the proposed localized interface region between the two bulk MoS 2 and Co 9 S 8 phases.

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Metal Sulfides

Cited by 3 publications

References 139 publications

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

Kinetic and Mechanistic Analysis of Dibenzothiophene Hydrodesulfurization on Ti-SBA-15–NiMo Catalysts

HRTEM and molecular modeling of the MoS₂–Co₉S₈interface: understanding the promotion effect in bulk HDS catalysts

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Metal Sulfides

Cited by 3 publications

References 139 publications

Effects of the Support on the Performance and Promotion of (Ni)MoS2 Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

Effects of the Support on the Performance and Promotion of (Ni)MoS2 Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

Kinetic and Mechanistic Analysis of Dibenzothiophene Hydrodesulfurization on Ti-SBA-15–NiMo Catalysts

HRTEM and molecular modeling of the MoS2–Co9S8interface: understanding the promotion effect in bulk HDS catalysts

Contact Info

Product

Resources

About

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

Effects of the Support on the Performance and Promotion of (Ni)MoS₂ Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

HRTEM and molecular modeling of the MoS₂–Co₉S₈interface: understanding the promotion effect in bulk HDS catalysts