About: Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics

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About: Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics Goto Sponge NotDistinct Permalink

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Description	Zeolites are highly important heterogeneous catalysts. Besides Brønsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors—“perturbed AlFR atoms in hydrated zeolites—were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3AlOH groups and are characterized by a broad 27Al NMR resonance (δi=59–62 ppm, CQ=5 MHz, and η=0.3–0.4) with a shoulder at 40 ppm in the 27Al MAS NMR spectrum. Dehydroxylation of (SiO)3AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3Al Lewis sites exhibit an extremely broad 27Al NMR resonance (δi67 ppm, CQ20 MHz, and η0.1). Zeolites are highly important heterogeneous catalysts. Besides Brønsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors—“perturbed AlFR atoms in hydrated zeolites—were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3AlOH groups and are characterized by a broad 27Al NMR resonance (δi=59–62 ppm, CQ=5 MHz, and η=0.3–0.4) with a shoulder at 40 ppm in the 27Al MAS NMR spectrum. Dehydroxylation of (SiO)3AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3Al Lewis sites exhibit an extremely broad 27Al NMR resonance (δi67 ppm, CQ20 MHz, and η0.1). (en)
Title	Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics (en)
skos:prefLabel	Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics (en)
skos:notation	RIV/61389013:_____/15:00439638!RIV15-GA0-61389013
http://linked.open...avai/riv/aktivita	I P
http://linked.open...avai/riv/aktivity	I, P(GA13-24155S), P(GA14-10251S)
http://linked.open...iv/cisloPeriodika	2
http://linked.open...vai/riv/dodaniDat	2015
http://linked.open...aciTvurceVysledku	Urbanová, Martina Brus, Jiří Kobera, Libor
http://linked.open.../riv/druhVysledku	J - Článek v odborném periodiku
http://linked.open...iv/duvernostUdaju	S - Úplné a pravdivé údaje nepodléhající ochraně podle zvláštních právních předpisů
http://linked.open...titaPredkladatele	Ústav makromolekulární chemie AV ČR, v. v. i.
http://linked.open...dnocenehoVysledku	446
http://linked.open...ai/riv/idVysledku	RIV/61389013:_____/15:00439638
http://linked.open...riv/jazykVysledku	eng - angličtina
http://linked.open.../riv/klicovaSlova	aluminum; density functional calculations; Lewis acids (en)
http://linked.open.../riv/klicoveSlovo	aluminum density functional calculations Lewis acids
http://linked.open...odStatuVydavatele	DE - Spolková republika Německo
http://linked.open...ontrolniKodProRIV	[D3C19B92D9B7]
http://linked.open...i/riv/nazevZdroje	Angewandte Chemie - International Edition
http://linked.open...in/vavai/riv/obor	JN
http://linked.open...ichTvurcuVysledku	3 (xsd:int)
http://linked.open...cetTvurcuVysledku	10 (xsd:int)
http://linked.open...vavai/riv/projekt	Monitoring and optimization of zeolite phases in aluminosilicate binders Catalysts for eliminating N2O in the high temperature regime in the production technology of nitric acid
http://linked.open...UplatneniVysledku	2015
http://linked.open...v/svazekPeriodika	54
http://linked.open...iv/tvurceVysledku	Dědeček, Jiří Klein, Petr Schoefberger, W. Sazama, Petr Sklenák, Štěpán Tabor, Edyta Urbanová, Martina Brus, Jiří Kobera, Libor Fishchuk, A. V.
http://linked.open...ain/vavai/riv/wos	000347238800026
issn	1433-7851
number of pages	5 (xsd:int)
http://bibframe.org/vocab/doi	10.1002/anie.201409635

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