Terminal and bridging methoxyls on zeolites detected by13C magic angle spinning NMR spectroscopy

Bosáček, V.; Klik, R.; Genoni, F.; Spanò, Guido; Rivetti, Franco; Figuéras, F.

doi:10.1002/(sici)1097-458x(199912)37:13<s135::aid-mrc562>3.0.co;2-y

Cited by 45 publications

(25 citation statements)

References 30 publications

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“…A correlation was found [92] between d 13 C isotropic chemical shift of methoxy groups of methyl iodide bound to framework oxygen atoms in alkali-exchanged zeolites and the mean Sanderson electronegativity S m of a zeolite framework as shown in Fig. 12.…”

Section: Nmr Analysismentioning

confidence: 88%

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

Védrine

2015

Res Chem Intermed

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In this overview, we focus on the different and current methods of acidbase characterization of heterogeneous catalysts and on their potential relation with catalytic properties in gas and liquid phases. Special emphasis is drawn on the main techniques currently employed such as the use of Hammett's indicators, the use of basic or acidic probes of different strength for adsorption measurements in microcalorimetry and of their thermal programmed desorption, the use of other techniques such as FTIR, ESR, NMR, photoluminescence, Raman, UV-Vis, and XPS, to identify and describe acid-base sites, the use of model catalytic reactions, and of theoretical/modeling approaches. Relationships between such a characterization and catalytic properties in different acid or base reactions are discussed, and implemented for different catalysts and different reactions. The concept of thermodynamic acidity/basicity (determined via chemical physical characterization) versus reactivity (determined via catalytic properties) of acid-base sites is presented, and explains why relationships between acid-base properties and catalytic properties are very often met but are difficult to be established unambiguously and cannot be generalized. The case of acid-base properties in liquid phase ''polar'' (water, alcohol) and ''apolar'' (cyclohexane) as ''effective'' and ''intrinsic'' properties, respectively, and their relation with catalytic properties in liquid phase are also discussed.Keywords Acid-base properties of solid catalysts Á Related catalytic properties Á Intrinsic versus effective acidity/basicity Á Acidity/basicity in liquid polar or apolar media

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Section: Nmr Analysismentioning

confidence: 88%

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

Védrine

2015

Res Chem Intermed

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“…It has been demonstrated that the chemical shifts of the 13 C MAS NMR signals of zeolite methoxy groups depend on the basicity (nucleophilicity) of the zeolitic oxygens. 58,70,71,100,175,176 A linear correlation was found between the chemical shift of methoxy groups at bridging positions and the intermediate electronegativity of the zeolite lattice oxygens. The literature data on the 13 C chemical shifts of methoxy groups observed for different zeolite and zeolitelike materials are summarized in Table 4.…”

Section: Methanol Interaction With Zeolitic Active Sites Adsorption C...mentioning

confidence: 88%

“…Another route leading to methoxy groups includes treatment of zeolites with methyl iodide. 58,70,71,100,175,176 Using these two approaches the methoxy groups of three different types have been obtained, namely, methyl group attached to bridging oxygen (Si-OCH 3 -Al) and methyl groups connected 81 (Reprinted with permission from M. Hunger and T. Horvath, J. Am.…”

Section: Methanol Interaction With Zeolitic Active Sites Adsorption C...mentioning

confidence: 99%

Impact of in situ MAS NMR techniques to the understanding of the mechanisms of zeolite catalyzed reactions

Ivanova

Kolyagin

2010

Chem. Soc. Rev.

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The in situ MAS NMR studies of the mechanisms of zeolite catalyzed reactions are reviewed. The first part of the critical review contains brief information on the different experimental approaches used for the in situ MAS NMR studies under batch and flow conditions. In the second part, a cross reference index between the reactions studied, the catalysts used, the mechanistic information obtained and the corresponding literature sources is established. Finally, in the last part the most widely studied areas are discussed in more detail. In particular, the impact of in situ MAS NMR to unravel the mechanisms of olefin, alcohol and alkanes transformations over zeolite catalysts is analyzed (232 references).

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“…However, as mentioned above, Ivanova et al [12], did associate methoxy groups on Brønsted sites to a signal at 49 ppm to, which differs significantly from the more frequently quoted values of 56-59 ppm. This assignment has been questioned by Bosacek et al [51].…”

Section: Insights From Spectroscopic Studiesmentioning

confidence: 96%

Mechanistic Aspects of the Zeolite Catalyzed Methylation of Alkenes and Aromatics with Methanol: A Review

et al. 2011

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Alkylation and methylation are important reactions in industrial zeolite catalyzed hydrocarbon transformation processes. This contribution compiles the present knowledge concerning the reaction mechanism of zeolite catalyzed methylation of alkenes and aromatics, based on insights obtained using spectroscopy, quantum chemistry, and kinetic measurements. A central issue is to discuss the potential role surface bound methoxy group intermediates.

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Terminal and bridging methoxyls on zeolites detected by13C magic angle spinning NMR spectroscopy

Cited by 45 publications

References 30 publications

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

Impact of in situ MAS NMR techniques to the understanding of the mechanisms of zeolite catalyzed reactions

Mechanistic Aspects of the Zeolite Catalyzed Methylation of Alkenes and Aromatics with Methanol: A Review

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