Hydrogen spillover and hydrocracking, hydroisomerization

Fujimoto, Kaoru

doi:10.1016/s0167-2991(99)80392-9

Cited by 13 publications

(4 citation statements)

References 28 publications

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“…For the hydroconversion of normal paraffins over metal/solid acid catalyst, it is generally accepted that acidic sites are responsible for cracking or isomerization reactions although the action mechanism of metal is still controversial . Therefore, the difference in activity for hydroconversion reactions over Pd/β catalyst with varied Si/Al ratios must be from the acidic properties of zeolites β because the same amount of Pd was introduced into zeolite β under equivalent conditions.…”

Section: Resultsmentioning

confidence: 99%

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Liu

Asami

et al. 2005

Energy Fuels

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The direct synthesis of isoparaffins from synthesis gas (H 2 /CO ) 2) was carried out in a consecutive dual reactor system under the conditions of P ) 1.0 MPa and W/F ) 4.97 g‚h‚mol -1 . In the upper reactor, Co/SiO 2 was used for Fischer-Tropsch (FT) reaction. To primarily decompose the heavy FT hydrocarbons, zeolite β (4:1 weight ratio) was physically mixed with Co/SiO 2 . The Pd/β catalyst with a Pd loading of 0.5 wt % and different Si/Al ratios in zeolites β was loaded in the lower reactor for hydroconverting the products from the upper reactor. Irrespective of the Si/Al ratio of zeolite β, the results indicate that the final products showed a sharp carbon number distribution in the range of C 4 -C 6 and very high selectivity to branched isomers of C 4 -C 6 alkanes. An apparent change of selectivity to isoparaffins was observed with the variation of the Si/Al ratio in Pd/β catalyst. Moreover, the stability of the catalyst was also influenced by the Si/Al ratios. The effect of the Si/Al ratio on the selectivity of isomers at different times on stream was correlated with the acidity and crystallization of the β zeolite, which were characterized by ammonia TPD and XRD methods.

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Section: Resultsmentioning

confidence: 99%

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Liu

Asami

et al. 2005

Energy Fuels

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“…Concretely, hydrogen molecules are adsorbed to the active surface of metal Ni nanoclusters and are dissociated into hydrogen atoms. The latter spill over , and migrate onto the surface of acidic HMOR and subsequently are converted into active hydrogen species (H + and H – ) through their interaction with acid sites (especially Lewis acid sites) there. − Then carbocation reaction and the recovery of surface protonic acid sites may be effectively accelerated due to the involvement of the above these formed active hydrogen species. − This means a greatly enhanced proton-transfer efficiency in the surface catalytic system over Ni–HMOR, and this significantly improved the reactivity of transalkylation catalyzed primarily by Brønsted acid sites. ,, It is also proved by the results of transalkylation over HMOR or 3.0%Ni–HMOR under different reaction atmospheres (N 2 or H 2 ). As shown in Figure , compared with the 2,6-DMN yield (at the initial reaction stage) for the two catalysts under a N 2 atmosphere or that for the HMOR under a H 2 atmosphere, a much higher yield was obtained over 3.0%Ni–HMOR under a H 2 atmosphere.…”

Section: Resultsmentioning

confidence: 99%

Transalkylation of C₁₀ Aromatics with 2-Methylnaphthalene for 2,6-Dimethylnaphthalene Synthesis over a Shape-Selective SiO₂–Ni–H-Mordenite with Nanosheet Crystal

Xie

Liang

Zhou

et al. 2021

Ind. Eng. Chem. Res.

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A reasonable control of the reaction pathways in the reaction system of the transalkylation of C 10 aromatics with 2methylnaphthalene was achieved over a shape-selective SiO 2 (II)− 3.0%Ni−H-mordenite (HMOR) with nanosheet crystals in a H 2 atmosphere. First, significantly improved reactivity was obtained depending on the synergistic catalysis from acid sites and metal Ni sites only on the internal surface, maybe due to a process where spillover hydrogen was converted into active hydrogen species and the latter greatly enhanced the proton-transfer efficiency in this surface catalysis. Second, based on the external surface passivation with little influence on the intrinsic excellent pore diffusibility of lamellar crystals, the side reactions of naphthalene nucleus ring opening and methylnaphthalene polyalkylation involved in largemolecule intermediates were significantly suppressed by the shape-selectivity restriction inside channels, meanwhile with remarkably enhanced dimethylnaphthalene selectivity. Both porous shape selectivity and a reasonably decreased acid strength also weakened the secondary conversion of β,β-dimethylnaphthalenes into other isomers. Therefore, an obviously improved selectivity of 2,6dimethylnaphthalene was gained. Also, a reasonable hydrogenation catalyzed by metal Ni sites strongly resisted coke deposition, and this created a good catalytic stability of this catalyst with an impressive capability of accommodating coke. As a result, a 2methylnaphthalene conversion of above 67.1% and a 2,6-dimethylnaphthalene yield of above 10.7% were obtained during a 100 h on stream reaction.

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“…However, besides other challenges such as very low equilibrium olefin content at the lower temperature of around 513 K, it is commonly believed that Pd is not a good catalyst for hydrogenation reactions although it can effectively activate hydrogen. 21 Furthermore, it was found that the distance between the Pt particles and the acidic sites was important in determining the activity and selectivity of Pt/β for hexane hydroconversion, 22 which cannot be explained based on the above bifunctional mechanism. As a matter of these facts, alternative mechanisms have been suggested.…”

Section: Examination Of the Reaction Mechanismmentioning

confidence: 99%

“…22,23 Based on the hydroconversion results of different hydrocarbons, Fujimoto's research group has proposed a hydrogen spillover mechanism. 21,[24][25][26][27][28][29] In this mechanism, the following steps were suggested: First, gaseous hydrogen dissociatively adsorbs on the surface of Pt or Pd to create Hsp; after that, Hsp migrates from the metal surface to the surface of the solid acid leading to H + sp and Hsp. The Hsp promotes desorption of the carbenium intermediate as an alkane, while the H + sp regenerates and/ or enhances the strength of the Bronsted acidic sites on the surface of solid acid.…”

Section: Examination Of the Reaction Mechanismmentioning

confidence: 99%

Insights into a Multifunctional Hybrid Catalyst Composed of Co/SiO₂ and Pd/Beta for Isoparaffin Production from Syngas

Liu

Asami

et al. 2005

Ind. Eng. Chem. Res.

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The direct production of gasoline-range isoparaffins from synthesis gas (CO + H 2 , syngas) via the Fischer-Tropsch (FT) route was investigated over a hybrid catalyst composed of Co/SiO 2 and Pd/β under the conditions of P ) 1.0 MPa, W/F ) 7.9 g‚h‚mol -1 and reaction temperatures of 503-513 K. Results indicate that the contact state between the Co/SiO 2 and the Pd/β particles in the hybrid catalyst (powdery mixture and granular mixture) had a clear effect on both the activity toward CO hydrogenation and the product distribution. Interestingly, the granular hybrid catalyst showed much higher performance in the case of isoparaffin selectivity than the powdery hybrid catalyst at the initial stage of the reaction. Furthermore, irrespective of the reaction conditions applied, the powdery hybrid catalyst gave apparently lower CO conversion and obviously higher CH 4 selectivity than the granular hybrid catalyst. Irrespective of the catalyst used, the total selectivity of isoparaffins (I/C 4 +) noticeably decreased with TOS due to the increase of selectivity of normal paraffins, the decrease of selectivity of isoparaffins, and less cracking of long-chain FT hydrocarbons. In the case of the powdery hybrid catalyst, a synergistic effect of the FT reaction over Co/SiO 2 and the hydroconversion reaction over Pd/β was suggested from the reaction results. A mechanistic model based on the migration of hydrogen species at the interfaces of the different particles was developed, and the reaction results were extensively discussed based on the proposed model.

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Hydrogen spillover and hydrocracking, hydroisomerization

Cited by 13 publications

References 28 publications

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Transalkylation of C₁₀ Aromatics with 2-Methylnaphthalene for 2,6-Dimethylnaphthalene Synthesis over a Shape-Selective SiO₂–Ni–H-Mordenite with Nanosheet Crystal

Insights into a Multifunctional Hybrid Catalyst Composed of Co/SiO₂ and Pd/Beta for Isoparaffin Production from Syngas

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Hydrogen spillover and hydrocracking, hydroisomerization

Cited by 13 publications

References 28 publications

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Formation of Isoparaffins through Pd/β Zeolite Application in Fischer−Tropsch Synthesis

Transalkylation of C10 Aromatics with 2-Methylnaphthalene for 2,6-Dimethylnaphthalene Synthesis over a Shape-Selective SiO2–Ni–H-Mordenite with Nanosheet Crystal

Insights into a Multifunctional Hybrid Catalyst Composed of Co/SiO2 and Pd/Beta for Isoparaffin Production from Syngas

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Transalkylation of C₁₀ Aromatics with 2-Methylnaphthalene for 2,6-Dimethylnaphthalene Synthesis over a Shape-Selective SiO₂–Ni–H-Mordenite with Nanosheet Crystal

Insights into a Multifunctional Hybrid Catalyst Composed of Co/SiO₂ and Pd/Beta for Isoparaffin Production from Syngas