Characterization of basic guest compounds on solid catalysts by13C CP/MAS NMR spectroscopy of surface methoxy groups

Schenk, Udo; Hunger, Michael; Weitkamp, Jens

doi:10.1002/(sici)1097-458x(199912)37:13<s75::aid-mrc536>3.0.co;2-a

Cited by 27 publications

(11 citation statements)

References 24 publications

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“…According to this correlation, a low 13 C NMR shift of the methoxy groups ( δ =54 for CsNa‐X zeolite)145 corresponds to a low mean electronegativity or a high base strength of the zeolite framework and vice versa. Methoxy groups on highly basic guest components, for example clusters of alkali metal acetates and oxides on Y and X zeolites, give signals in the range δ =48.7 to 50.0 147–149…”

Section: Nmr Spectroscopymentioning

confidence: 99%

In situ IR, NMR, EPR, and UV/Vis Spectroscopy: Tools for New Insight into the Mechanisms of Heterogeneous Catalysis

Hunger

Weitkamp

2001

Angewandte Chemie Intl Edit

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244

108

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The development of new solid catalysts for use in industrial chemistry has hitherto been based to a large extent upon the empirical testing of a wide range of different materials. In only a few exceptional cases has success been achieved in understanding the overall, usually very complex mechanism of the chemical reaction through the elucidation of individual intermediate aspects of a heterogeneously catalyzed reaction. With the modern approach of combinatorial catalysis it is now possible to prepare and test much more rapidly a wide range of different materials within a short time and thus find suitable catalysts or optimize their chemical composition. Our understanding of the mechanisms of reactions catalyzed by these materials must be developed, however, by spectroscopic investigations on working catalysts under conditions that are as close as possible to practice (temperature, partial pressures of the reactants, space velocity). This demands the development and the application of new techniques of in situ spectroscopy. This review will show how this objective is being achieved. By the term in situ (Lat.: in the original position) is meant the investigation of the chemical reactions which are taking place as well as the changes in the working catalysts directly in the spectrometer.

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Section: Nmr Spectroscopymentioning

confidence: 99%

In situ IR, NMR, EPR, and UV/Vis Spectroscopy: Tools for New Insight into the Mechanisms of Heterogeneous Catalysis

Hunger

Weitkamp

2001

Angewandte Chemie Intl Edit

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244

108

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“…Methoxygruppen an stark basischen Gastkomponenten, z. B. Clustern aus Alkalimetallacetaten und ‐oxiden auf oder in Y‐ und X‐Zeolithen, liefern Signale im Bereich von δ =48.7 bis 50.0 147–149…”

Section: Nmr‐spektroskopieunclassified

In-situ-IR-, -NMR-, -EPR- und -UV/Vis-Spektroskopie: Wege zu neuen Erkenntnissen in der heterogenen Katalyse

Hunger

Weitkamp

2001

Angew. Chem.

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Die Entwicklung neuer Festkörperkatalysatoren für den Einsatz in der industriellen Chemie beruht bisher noch zu einem sehr großen Teil auf dem empirischen Erproben einer Vielzahl unterschiedlicher Materialien. Nur in wenigen Ausnahmefällen ist es gelungen, durch die Aufklärung der einzelnen Teilaspekte einer heterogen katalysierten Reaktion den gesamten, meist sehr komplexen Mechanismus der chemischen Umsetzung zu verstehen. Mit modernen Konzepten der kombinatorischen Katalyseforschung ist es möglich geworden, innerhalb kurzer Zeiträume eine große Zahl unterschiedlicher Materialien zu präparieren und zu testen und damit schneller als vorher geeignete Katalysatoren zu finden oder ihre chemische Zusammensetzung zu optimieren. Unser Verständnis der Mechanismen der von diesen Materialien katalysierten Reaktionen muss jedoch durch spektroskopische Untersuchungen an arbeitenden Katalysatoren unter möglichst praxisnahen Bedingungen (Temperatur, Partialdruck der Reaktanten, Katalysatorbelastung) entwickelt werden. Dies erfordert die Entwicklung und den Einsatz neuer Techniken der In‐situ‐Spektroskopie. Der vorliegende Aufsatz soll zeigen, auf welchen Wegen dieses Ziel erreicht wird. Der Begriff in situ (lat.: an Ort und Stelle) beinhaltet im eigentlichen Sinne die Untersuchung der direkt im Spektrometer ablaufenden chemischen Reaktionen und die mit ihnen verbundenen Veränderungen des Katalysators.

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“…21,22 Hunger et al conrmed the existence of strong base sites on the guest alkali oxides by 13 C CP/MAS NMR with methyl iodide as a probe, and found that the chemical bonds of the parent zeolite can be affected by the loaded cesium oxide which would lead to the enhancement of base strength of O dÀ in the host zeolite framework. 23,24 It can be found that the promoting effects for base properties of the base zeolite by further modication with alkali oxides were investigated widely. However, scarce attentions have been given to the correlation of the introduced base sites in alkali oxides modi-ed CsX with the promotion for side-chain alkylation of toluene with methanol, especially for the mechanism understanding.…”

Section: Introductionmentioning

confidence: 99%

Explaining the influence of the introduced base sites into alkali oxide modified CsX towards side-chain alkylation of toluene with methanol

Han

Zhang

et al. 2019

RSC Adv.

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Characterization of basic guest compounds on solid catalysts by13C CP/MAS NMR spectroscopy of surface methoxy groups

Cited by 27 publications

References 24 publications

In situ IR, NMR, EPR, and UV/Vis Spectroscopy: Tools for New Insight into the Mechanisms of Heterogeneous Catalysis

In situ IR, NMR, EPR, and UV/Vis Spectroscopy: Tools for New Insight into the Mechanisms of Heterogeneous Catalysis

In-situ-IR-, -NMR-, -EPR- und -UV/Vis-Spektroskopie: Wege zu neuen Erkenntnissen in der heterogenen Katalyse

Explaining the influence of the introduced base sites into alkali oxide modified CsX towards side-chain alkylation of toluene with methanol

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