Investigation of peculiarities of the composition and structure of methylalumoxanes:27Al and1H NMR spectra of trimethylaluminum and products of its incomplete hydrolysis

Korneev, N. N.; Khrapova, I. M.; Polonskii, A. V.; Иванова, Н. И.; Kisin, A. V.; Kolesov, V. S.

doi:10.1007/bf00699939

Cited by 6 publications

(5 citation statements)

References 8 publications

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“…40 TMA itself is a prototypical precursor to the industrially important MAO co-catalyst for olefin polymerization. [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] The modification of dealuminated Y 6 zeolite with TMA followed by impregnation of platinum has been shown to result in enhanced reactivity of the zeolite catalyst for decane dehydrogenation. [56][57][58] As a starting material, we employ a high-silica faujasite zeolite prepared by selective substitution of Al F with Si atoms via treatment with ammonium hexafluorosilicate (NH 4 ) 2 SiF 6 of zeolite Y.…”

Section: Introductionmentioning

confidence: 99%

“…Previously, it has been demonstrated that TMA can be effectively incorporated into mesoporous silica MCM-41 via various postsynthesis procedures . TMA itself is a prototypical precursor to the industrially important MAO cocatalyst for olefin polymerization. − The modification of dealuminated Y zeolite with TMA followed by impregnation of platinum has been shown to result in enhanced reactivity of the zeolite catalyst for decane dehydrogenation. − …”

Section: Introductionmentioning

confidence: 99%

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Chemical Vapor Deposition of Trimethylaluminum on Dealuminated Faujasite Zeolite

et al. 2013

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Chemical vapor deposition of trimethylaluminum (TMA) was explored as an approach for the preparation of model faujasite-type catalysts containing extraframework aluminum. The decomposition of the grafted organoaluminum species was investigated in hydrogen and oxygen atmosphere. The process of grafting Al-containing species and the associated changes of the zeolite hydroxyl groups were followed by in situ FTIR spectroscopy. The state of intrazeolite Al atoms, the changes in zeolite structure and acidity caused by the CVD procedure as well as by subsequent treatment were analyzed in detail by 1H, 29Si, and 27Al MAS NMR, COads IR, H/D exchange of acidic hydroxyl groups with perdeuterobenzene, and propane cracking. Reaction of an extraframework aluminum-free high-silica faujasite zeolite with TMA leads to nearly complete substitution of the bridging hydroxyl groups with Al species. The reaction, however, does not produce uniform homogeneously distributed species. Because of the high reactivity of TMA, the zeolite lattice is partially decomposed resulting in its partial dealumination and formation of stable Si-CH3 moieties. The exact conditions of post-CVD treatment influence strongly the chemical and catalytic properties of the zeolites. The strongest increase of the propane conversion rate was observed when grafted TMA species were decomposed in H2 at high temperature. Such zeolite displays much higher activity per Brønsted acid site in propane cracking than a commercial ultrastabilized Y zeolite. It is proposed that the activity enhancement is related to strong polarization of a fraction of the zeolite Brønsted acid sites by Lewis acid sites formed by the hydrogenolysis of grafted TMA complexes.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Chemical Vapor Deposition of Trimethylaluminum on Dealuminated Faujasite Zeolite

et al. 2013

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“…Trimethylaluminum, Al(CH 3 ) 3 , is useful for generating aluminum-based layers that subsequently can be converted to aluminum oxide or aluminum nitride layers. Trimethylaluminum also serves as a prototype or precursor to important cocatalysts in olefin polymerization. − …”

Section: Introductionmentioning

confidence: 99%

“…Trimethylaluminum also serves as a prototype or precursor to important cocatalysts in olefin polymerization. [13][14][15][16][17][18][19][20][21][22][23][24][25] Previous work on the reaction between trimethylaluminum and dry silica gel has focused mainly on reactions occurring using gas-phase reagents (i.e., at a gas/solid interface), [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] infrared spectroscopy being the most common spectroscopic method used. This previous research includes some solid-state NMR work in one study from this laboratory.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of the Silica Surface: Liquid−Solid Reactions of Silica Gel with Trimethylaluminum

2006

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The reaction of trimethylaluminum and dry, high-surface-area (500 m2/g) silica gel in a mixed slurry was studied using multinuclear, solid-state NMR spectroscopy. The products of the initial reaction were characterized, and their progress through subsequent washing with diethyl ether and reactions with measured amounts of water was followed. The quantitative distribution of different chemical forms of carbon deposited on the silica surface by the initial reaction was measured. The products of the initial reaction are dominated by methyl species of the types Al(CH3)n (with Si-O-Al linkages), Si-O-CH3, and (Si-O)4-nSi(CH3)n; aluminum is seen to exist predominantly as a five-coordinate species. Subsequent treatment with diethyl ether fails to remove any surface species, but instead the ether becomes strongly associated with the surface and highly resistant to removal. Stepwise additions of water hydrolyze the Al-CH3 and Si-O-CH3 moieties, leading to conversion of five-coordinate aluminum to four- and six-coordinate aluminum, and affect the partial release of the surface-associated diethyl ether; Si-CH3 moieties remain. The effect of aromatic and saturated solvents on the initial reaction was examined and found to cause a small but significant change in the distribution of products. Structures of aluminum-centered species on the silica surface consistent with the spectroscopic data are proposed.

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“…11 All these approaches to explain the structure of MAO are of great interest in relation to their application in homogeneous polymerization of olefins. It is well known that MAOs are the most effective cocatalyst with metallocene catalysts in the polymerization process.…”

Section: Introductionmentioning

confidence: 99%

Organoboron water, part I: Synthesis and multinuclear magnetic resonance studies on the structure of tetramethyldialuminoxane

Kacprzak

Serwatowski

2004

Applied Organom Chemis

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The structure of tetramethyldialuminoxane was studied. The low-temperature 1 H and 13 C NMR spectra suggest that the methyl groups bridge the aluminum atoms in the dialuminoxane trimer. A new method of synthesis of methylaluminoxanes and tetramethyldialuminoxanes in the reaction of tetraethyldiboroxane (organoboron water) with trimethylaluminum (1 : 1 and 1 : 2 respectively) was applied to synthesize the investigated system.

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Investigation of peculiarities of the composition and structure of methylalumoxanes:27Al and1H NMR spectra of trimethylaluminum and products of its incomplete hydrolysis

Cited by 6 publications

References 8 publications

Chemical Vapor Deposition of Trimethylaluminum on Dealuminated Faujasite Zeolite

Chemical Vapor Deposition of Trimethylaluminum on Dealuminated Faujasite Zeolite

Chemistry of the Silica Surface: Liquid−Solid Reactions of Silica Gel with Trimethylaluminum

Organoboron water, part I: Synthesis and multinuclear magnetic resonance studies on the structure of tetramethyldialuminoxane

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