A theoretical DFT study of the mechanism of CC bond hydrogenolysis in alkanes on silica-supported zirconium hydrides

Besedin, D. V.; Ustynyuk, L. Yu.; Ustynyuk, Yuri A.; Лунин, В. В.

doi:10.1070/mc2002v012n05abeh001645

Cited by 20 publications

(21 citation statements)

References 11 publications

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“…In our studies [19][20][21] we have examined some important issues concerning the kinetics and mechanisms of the catalytic processes involving the formation (ethylene polymerization) and cleavage (hydrogenolysis of alkanes) of the CAC bonds on the silica-supported zirconium hydrides. The unique ability of these systems to catalyze both processes depending on the presence of hydrogen in the system was rationalized.…”

Section: Discussionmentioning

confidence: 99%

“…In essence, the mechanism of the reaction of the model compound 1 with butane molecule [19,21] is similar to the sequence of transformations, which is the reverse of ethylene polymerization on these species (scheme 1). The energy profile of the reaction is shown in figure 1…”

Section: Hydrogenolysis Of Butanementioning

confidence: 99%

“…Scheme 3 presents the mechanism of the interaction between the model compound 2 and butane molecule (the energy profile of the reaction is shown in figure 2(b)) [19,21]. The presence of the second hydride Scheme 2. ligand in compound 2 makes the mechanism of hydrogenolysis of butane on these species qualitatively different from the mechanism of the reaction of monohydrides 1 with butane molecule (see above).…”

Section: Hydrogenolysis Of Butanementioning

confidence: 99%

“…Earlier, we have studied the reactions of isotope exchange in methane [18] and hydrogenolysis of butane [19] on the surface hydrides of tetravalent zirconium. It was found that the calculated activation parameters of the reactions involving zirconium dihydrides are in better agreement with those reported in the experimental study by Hall et al [9].…”

Section: Introductionmentioning

confidence: 99%

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Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

Besedin

Ustynyuk

et al. 2005

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The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes (propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (BSiAO) 3 Zr IV H, (BSiAO) 2 Zr IV H 2 , and (BSiAO) 2 Zr III H were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (BSiAO) 3 ZrH, and dihydrides, (BSiAO) 2 ZrH 2 . Cleavage of linear alkanes on the monohydrides (BSiAO) 3 ZrH is thermodynamically unfavorable; however, the dihydrides (BSiAO) 2 ZrH 2 can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (BSiAO) 2 Zr III H, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes.

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Section: Discussionmentioning

confidence: 99%

Section: Hydrogenolysis Of Butanementioning

confidence: 99%

Section: Hydrogenolysis Of Butanementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

Besedin

Ustynyuk

et al. 2005

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“…From the Zr-butyl intermediate, the next step is the C-C activation, the key step of the mechanism (C-C bond cleavage). b-alkyl transfer has already been proposed for this step in the alkane hydrogenolysis on silica supported Zr hydrides [29][30][31][32]. We have also evaluated this elementary step by calculation on the alumina supported Zr hydride system, and compared it with alternative solutions.…”

Section: Mechanism For the Hydrogenolysis Of Butane With Alumina Suppmentioning

confidence: 98%

Gamma-alumina: An Active Support to Obtain Immobilized Electron Poor Zr Complexes

et al. 2008

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By grafting well-defined metallic complexes on a solid support, surface organometallic chemistry provides a bridge between homogeneous and heterogeneous catalysis. This innovative approach has already proven its efficiency for several reactions: polymerization, olefin and alkane metathesis… However several fundamental questions remain open on the chemical role of the oxide surface, on the grafting mechanism and on the reactivity of the grafted complex. Is a single well-defined surface/metal/ligand complex formed? Is the solid surface just an inert support, or does it play an active chemical role? We combine on the one hand reactivity and spectroscopic experiments with on the other hand total energy calculations and spectra simulations (NMR, IR) in order to propose insights for these open questions, using the example of [Zr(CH 2 tBu) 4 ] complex grafted on partially dehydroxylated gamma-alumina. A molecular level approach to the grafting mechanism is proposed. Alumina plays a dual role, both as support and Lewis acid co-catalyst. The hydroxyl groups permit the covalent grafting through Al-O-Zr linkages, while the neighboring Al Lewis sites allow the formation of an ion pair, by transfer of an alkyl ligand from the Zr toward the Al. The formed cationic Zr center shows an enhanced electrophilic character. The mechanism of the formation of the Zr hydride supported on alumina, upon treatment under H 2 gas is described, with the formation of a mixture of mono-hydride (Zr + -H; Al --CH 2 tBu) and bis-hydride (Zr + -H; Al --H). This Zr hydride supported on alumina is active for butane hydrogenolysis. A mechanism with reasonable energy barriers is proposed, the rate limiting step being the C-C scission.

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Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

et al. 2018

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Many industrial catalysts contain isolated metal sites on the surface of oxide supports. Although such catalysts have been used in a broad range of processes for more than 40 years, there is often a very limited understanding about the structure of the catalytically active sites. This Review discusses how surface organometallic chemistry (SOMC) engineers surface sites with well-defined structures and provides insight into the nature of the active sites of industrial catalysts; the Review focuses in particular on olefin production and conversion processes.

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A theoretical DFT study of the mechanism of CC bond hydrogenolysis in alkanes on silica-supported zirconium hydrides

Cited by 20 publications

References 11 publications

Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

Gamma-alumina: An Active Support to Obtain Immobilized Electron Poor Zr Complexes

Bridging the Gap between Industrial and Well‐Defined Supported Catalysts

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