27Al Multiple-Quantum MAS NMR of Mechanically Treated Bayerite (α-Al(OH)3) and Silica Mixtures

Ashbrook, Sharon E.; MacKenzie, Kenneth J.D.; Wimperis, Stephen

doi:10.1006/snmr.2001.0032

Cited by 20 publications

(23 citation statements)

References 30 publications

(69 reference statements)

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“…The appearance of three coordination environments for Al is consistent with other known amorphous aluminas [27]. Whereas the solid-state 27 Al NMR for boehmite [28], bayerite [29] and α-alumina [28] exhibit only six-coordinate Al, Gibbsite [30] and γ-alumina [28] exhibit six-and four-coordinate Al environments. An infrared absorption spectrum of the fine white amorphous material reveals a broad band at 500Ϫ1000 cm Ϫ1 , which is characteristic of amorphous nano-Al 2 O 3 .…”

Section: Characterization Of the Aluminum Oxidesupporting

confidence: 80%

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Wang¹,

Bhandari²,

Mitra³

et al. 2005

Zeitschrift anorg allge chemie

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Abstract. When toluene solutions of the tetrametallic compound, [Al{µ-OEt) 2 AlMe 2 } 3 ] (1), are stirred in air at room temperature, pure amorphous nanoparticulate Al 2 O 3 precipitates. The average particle size is 17.7 ± 7.4 nm. The tetrametallic core of 1, having the correct stoichiometry for alumina (2Al 2 O 3 ) appears to act as a template or nucleating site for the formation of alumina rather than the expected products of formula, AlOOH. The stability of the Al 4 O 6 core of 1 was tested by combining it with six equivalents

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Section: Characterization Of the Aluminum Oxidesupporting

confidence: 80%

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Wang¹,

Bhandari²,

Mitra³

et al. 2005

Zeitschrift anorg allge chemie

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“…Vega et al [92] demonstrated the presence of a stable pentacoordinated Al site on the surface of alumina in alumina multilayers doped inside a wide-pore MCM-41 silica. [88] In contrast, herein, we have provided experimental evidence for the creation of stable, unconventional Al sites with a distorted or strained configuration if water and aminosilanes were added to the alumina surface. The presence of such distorted Al altered the acid-base properties of the silica support (MCM-41) considerably and resulted in extremely high acidity, which caused the Al-doped silica to exhibit a fivetimes-higher activity in the alkylation of phenol with methanol compared to conventional alumina with just tetrahedral and octahedral sites.…”

Section: Unusual Effects Of Water and Grafted Aminosilanes On The Sormentioning

confidence: 70%

“…[88,89] Second-order line broadening can be identified and removed by 2 D Al NMR spectroscopy techniques to result in spectra that allow the unambiguous identification of Al sites. [88,89] Second-order line broadening can be identified and removed by 2 D Al NMR spectroscopy techniques to result in spectra that allow the unambiguous identification of Al sites.…”

Section: Unusual Effects Of Water and Grafted Aminosilanes On The Sormentioning

confidence: 99%

Aminosilanes Grafted to Basic Alumina as CO₂ Adsorbents—Role of Grafting Conditions on CO₂ Adsorption Properties

et al. 2014

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Solid oxide-supported amine sorbents for CO2 capture are amongst the most rapidly developing classes of sorbent materials for CO2 capture. Herein, basic γ supports are used as hosts for amine sites through the grafting of 3-aminopropyltrimethoxysilane to the alumina surface under a variety of conditions, yielding the expected surface-grafted alkylamine groups, as demonstrated by FTIR spectroscopy and (29)Si and (13)C cross-polarization magic-angle spinning (CPMAS NMR) spectroscopy. Grafting amine sites on the surface in the presence of water leads to a high density of amine sites on the surface whereas simultaneously creating a unique type of aluminum species on the surface, as demonstrated by both 1D and 2D (27)Al MAS NMR spectroscopy. The thus prepared sorbents result in higher CO2 adsorption capacities and amine efficiencies compared to sorbents prepared in the absence of water or similar amine loading sorbents prepared using silica supports. In situ FTIR spectra of the sorbents exposed to CO2 at various pressures show no distinct difference in the nature of the adsorbed CO2 species on alumina- versus silica-supported amines, whereas water adsorption isotherms show that the improved performance of the amine-grafted alumina support is not a consequence of retained water on the more hydrophobic aminoalumina materials. The findings demonstrate that amine-grafted, basic alumina materials can be tuned to be more efficient than the corresponding silica-supported materials at comparable amine loadings, further demonstrating that the properties of amine sites can be tuned by controlling or adjusting the support surface properties.

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“…The study of amorphous or disordered materials using highresolution 27 Al NMR techniques such as MQMAS or STMAS is of considerable interest (23)(24)(25)(26). Figure 8 shows a twodimensional 27 Al (I = 5/2) STMAS spectrum of γ -Al 2 O 3 , recorded with the pulse sequence in Fig.…”

Section: Stmas Of Spinmentioning

confidence: 99%

Satellite-Transition MAS NMR of Spin I=3/2, 5/2, 7/2, and 9/2 Nuclei: Sensitivity, Resolution, and Practical Implementation

Ashbrook

Wimperis

2002

Journal of Magnetic Resonance

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106

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27Al Multiple-Quantum MAS NMR of Mechanically Treated Bayerite (α-Al(OH)3) and Silica Mixtures

Cited by 20 publications

References 30 publications

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Aminosilanes Grafted to Basic Alumina as CO₂ Adsorbents—Role of Grafting Conditions on CO₂ Adsorption Properties

Satellite-Transition MAS NMR of Spin I=3/2, 5/2, 7/2, and 9/2 Nuclei: Sensitivity, Resolution, and Practical Implementation

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27Al Multiple-Quantum MAS NMR of Mechanically Treated Bayerite (α-Al(OH)3) and Silica Mixtures

Cited by 20 publications

References 30 publications

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Ambient‐Condition nano‐Alumina Formation Through Molecular Control

Aminosilanes Grafted to Basic Alumina as CO2 Adsorbents—Role of Grafting Conditions on CO2 Adsorption Properties

Satellite-Transition MAS NMR of Spin I=3/2, 5/2, 7/2, and 9/2 Nuclei: Sensitivity, Resolution, and Practical Implementation

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Aminosilanes Grafted to Basic Alumina as CO₂ Adsorbents—Role of Grafting Conditions on CO₂ Adsorption Properties