Hydrodesulfurization of Refractory Sulfur Species. 2. Selective Hydrodesulfurization of 4,6-Dimethyldibenzothiophene in the Dominant Presence of Naphthalene over Ternary Sulfides Catalyst

Isoda, Takaaki; Nagao, Shinichi; Ma, Xiaoliang; Korai, Yozo; Mochida, Isao

doi:10.1021/ef9501455

Cited by 25 publications

(10 citation statements)

References 11 publications

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“…Naphthalene Inhibition. A variety of polyaromatic compounds present in the diesel oil adsorb completely with sulfur species on the same catalyst surface. − It was found in the present study that the increasing concentration of naphthalene in the feedstock increased the ratio of [HYD]/[DDS] slightly at a 50% conversion level, although naphthalene reduced both the rates. It should be remembered that the [HYD/DDS] ratio varies with the conversion level.…”

Section: Discussionmentioning

confidence: 49%

Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

et al. 1998

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Hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) in decane has been investigated over a Co−Mo/C catalyst, using a magnetically stirred autoclave reactor. The hydrodesulfurization reaction was found to be pseudo-first order with respect to 4,6- DMDBT. Direct desulfurization was detected to be Arrhenius-dependent with an activation energy of 35.7 kcal/mol, while hydrogenation pathway showed a maxima at 340 °C. The activation energy of hydrogenation in the Arrhenius-dependent region was calculated to be 17.9 kcal/mol, as hydrogenation is thermodynamically limited at high temperature. The reaction of hydrodesulfurization appears to proceed via two different partially dependent routes, hydrogenation and desulfurization, over the present catalyst. Hydrogenation of 3,3‘-dimethylbiphenyl at different temperatures was also measured to identify the rates of the step involved in the hydrodesulfurization network of 4,6-DMDBT. Attention was particularly paid to the effects of naphthalene and H2S on the two different reaction pathways to propose the mechanism of their inhibition. Two different catalytic active sites, one for hydrogenation and the other for both hydrogenation and direct desulfurization, are discussed to be present.

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Section: Discussionmentioning

confidence: 49%

Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

et al. 1998

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“…There are two possible approaches for the efficient desulfurization of 4,6-DMDBT: (1) the selective hydrogenation of 4,6-DMDBT in the dominant aromatic partners and (2) hydrodesulfurization (HDS) reaction after the migration of substituted methyl groups in 4,6-DMDBT. The present authors have reported that blends of Ru/Al 2 O 3 and CoMo/Al 2 O 3 catalysts or Ru-CoMo/Al 2 O 3 catalyst showed higher hydrogenation selectivity for 4,6-DMDBT in a high concentration of naphthalene than conventional CoMo/Al 2 O 3 and NiMo/Al 2 O 3 . However, no isomerization reaction was found over the conventional catalysts. , …”

Section: Introductionmentioning

confidence: 64%

Hydrodesulfurization Pathway of 4,6-Dimethyldibenzothiophene through Isomerization over Y-Zeolite Containing CoMo/Al₂O₃ Catalyst

et al. 1996

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Hydrodesulfurization (HDS) reactivity of a refractory sulfur species, 4,6-dimethyldibenzothiophene (4,6-DMDBT), was examined over a Y-zeolite containing CoMo/Al 2 O 3 (CoMo/Al 2 O 3zeolite), conventional CoMo/Al 2 O 3 , and NiMo/Al 2 O 3 . Isomerization and considerable transalkylation of 4,6-DMDBT into 3,6-DMDBT and into tri-or tetramethyldibenzothiophenes, respectively, were observed characteristically over CoMo/Al 2 O 3 -zeolite catalyst. Migration of methyl groups enhances the HDS reactivity of the refractory sulfur species by diminishing the steric hindrance. Among the catalysts examined, CoMo/Al 2 O 3 -zeolite exhibited the best activity for HDS of the gas oil through the effective desulfurization of refractory alkyldibenzothiophenes.

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“…Girgis et al reported that HDS reactivity of sulfur species was hindered by sulfur-, oxygen-, and nitrogen-containing species. In an earlier study, we reported that the HDS reaction of 4,6-DMDBT was greatly decreased by hydrogen sulfide, which was added or produced from coexisting benzothiophene (BT) . However, additive dibenzothiophene (DBT) did not affect the reactivity of 4,6-DMDBT.…”

Section: Resultsmentioning

confidence: 99%

Changes in Desulfurization Reactivity of 4,6-Dimethyldibenzothiophene by Skeletal Isomerization Using a Ni-Supported Y-Type Zeolite

et al. 2000

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Skeletal isomerization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was performed at 270 °C for 1 h at a hydrogen pressure of 2.5 MPa using a Ni-supported Y-type zeolite catalyst. Alkyldibenzothiophenes (alkyl-DBTs), which were produced by methylmigration and transalkylation, were further desulfurized at 255−300 °C for 2−120 min at a hydrogen pressure of 2.5 MPa using a CoMo/Al2O3 catalyst. The produced alkyl-DBTs, which carried 1−3 methyl groups, could be classified into three groups on the basis of activation energy for desulfurization. Group I included 2,8-DMDBT and C1-DBT, which carried no methyl groups at either the 4- or 6-position. Group III included unreacted 4,6-DMDBT, and group II contained other alkyl-DBTs with 1−3 methyl groups. No alkyl-DBTs with 4 methyl groups were found in the products of 4,6-DMDBT. The steric hindrance of the methyl groups on 4,6-DMDBT was relieved by methylmigration and transalkylation, and, as a result, the desulfurization activation energy, 37.2 kcal/mol, for 4,6-DMDBT was decreased to 24−33 kcal/mol for alkyl-DBTs in group II and to 23 kcal/mol for alkyl-DBTs in group I. Desulfurization reactivity of the alkyl-DBTs was also examined on the basis of molecular orbital calculation using the WinMOPAC program. The cross sectional area of the Sσn orbital on the sulfur atom, which was in contact with the catalyst surface, was 0.12 nm2 for 4,6-DMDBT, 0.70 nm2 for 4-MDBT, and 1.27 nm2 for DBT. Thus the desulfurization reactivity increases with increasing overlapping area of the Sσn orbital with the catalyst active site. A wider cross sectional area was achieved by migration of methyl groups using the zeolite catalyst.

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Hydrodesulfurization of Refractory Sulfur Species. 2. Selective Hydrodesulfurization of 4,6-Dimethyldibenzothiophene in the Dominant Presence of Naphthalene over Ternary Sulfides Catalyst

Cited by 25 publications

References 11 publications

Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Hydrodesulfurization Pathway of 4,6-Dimethyldibenzothiophene through Isomerization over Y-Zeolite Containing CoMo/Al₂O₃ Catalyst

Changes in Desulfurization Reactivity of 4,6-Dimethyldibenzothiophene by Skeletal Isomerization Using a Ni-Supported Y-Type Zeolite

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Hydrodesulfurization of Refractory Sulfur Species. 2. Selective Hydrodesulfurization of 4,6-Dimethyldibenzothiophene in the Dominant Presence of Naphthalene over Ternary Sulfides Catalyst

Cited by 25 publications

References 11 publications

Kinetic Analyses and Inhibition by Naphthalene and H2S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Kinetic Analyses and Inhibition by Naphthalene and H2S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Hydrodesulfurization Pathway of 4,6-Dimethyldibenzothiophene through Isomerization over Y-Zeolite Containing CoMo/Al2O3 Catalyst

Changes in Desulfurization Reactivity of 4,6-Dimethyldibenzothiophene by Skeletal Isomerization Using a Ni-Supported Y-Type Zeolite

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Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Kinetic Analyses and Inhibition by Naphthalene and H₂S in Hydrodesulfurization of 4,6-Dimethyldibenzothiophene (4,6-DMDBT) over CoMo-Based Carbon Catalyst

Hydrodesulfurization Pathway of 4,6-Dimethyldibenzothiophene through Isomerization over Y-Zeolite Containing CoMo/Al₂O₃ Catalyst