Characterizations of MAPO-36 molecular sieve by solid-state n.m.r.

Nakashiro, Katsumi; Ono, Yoshio; Nakata, Shinichi; Morimura, Yasuo

doi:10.1016/0144-2449(93)90234-t

Cited by 18 publications

(4 citation statements)

References 7 publications

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“…The fact that [6] Al existing on the outermost surface of the cell wall decreased after heating provides important information about the local structure of the cell wall: (i) oxygen atoms of water molecules coordinate to [4] Al and/or [5] Al to form [6] Al in the as-prepared samples; (ii) the formed [6] Al near the surface decreases along with elimination of physisorbed water during heating. Because oxygen atoms of water molecules are known to coordinate to [4] Al in aluminum phosphate molecular sieves to form [6] Al, a similar phenomenon might occur even in the anodic amorphous alumina samples.…”

Section: Resultsmentioning

confidence: 99%

NMR Spectroscopic Analysis of the Local Structure of Porous-Type Amorphous Alumina Prepared by Anodization

et al. 2017

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Alumina is classified as an intermediate oxide that cannot form a glass and is industrially used as a multifunctional material. Intensive studies on the atomistic structure of amorphous alumina have been conducted because a fundamental understanding of its structure can be meaningful to the design of new materials and devices. Here we focused on anodic alumina as a model material for clarifying the atomistic structure of amorphous alumina and prepared anion-free and anion-incorporated poroustype amorphous alumina by anodization using chromic acid electrolyte and typical electrolytes (e.g., sulfuric acid, oxalic acid, and phosphoric acid), respectively. The local structure around aluminum atoms in the anodic alumina was investigated by nuclear magnetic resonance spectroscopy. We found that the structure of anodic amorphous alumina comprises AlO 4 , AlO 5 , and AlO 6 units with predominant fractions of AlO 5 . We also observed that the fraction of each unit was 37.7, 54.3, and 8.0%, with an average coordination number (N Al−O ) of 4.70 in the anion-free sample. The results of 1 H− 27 Al cross-polarization with magic angle spinning measurements showed that the prevalence of AlO 6 units decreased with the elimination of physisorbed water by heat treatment. We also suggest that the average N Al−O is affected by the depth, content, and/or species of incorporated anions and that the average N Al−O increases with increasing anion content in the case of samples prepared using sulfuric acid electrolyte. The results are quite meaningful because they provide precise information about the local structure of anodic amorphous alumina; previous reports on this subject have been inconsistent and controversial. We expect that the present results will accelerate structural analysis research on the atomistic structures of amorphous alumina.

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Section: Resultsmentioning

confidence: 99%

NMR Spectroscopic Analysis of the Local Structure of Porous-Type Amorphous Alumina Prepared by Anodization

et al. 2017

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“…In the 31 P MAS NMR spectrum of the reaction gel for APO-L6 (Figure ), only one peak at −8.2 ppm is observed, suggesting the presence of phosphorus atoms in a reasonably uniform tetrahedral coordination environment. − The 31 P MAS NMR spectrum for the as-synthesized APO-L6 sample also exhibits one peak, but the maximum of the peak shifts slightly to −7.8 ppm. The difference between the spectrum of the gel and that for the as-synthesized APO-L6 indicates that the local environment of the P atoms is changed, to a certain degree, when the gel is transformed to the lamellar material.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of a Family of Amine-Intercatalated Lamellar Aluminophosphates from Alcoholic System

Gao

Chen

et al. 1997

Chem. Mater.

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A family of lamellar aluminophosphates designated APO-Ln (L stands for lamellar and n = 6, 8, 10, 12, the number of carbon atoms for the occluded template molecules) was synthesized from a mixture of phosphoric acid, aluminum triisopropoxide, ethylene glycol and an unbranched primary alcohol in the presence of an amine as the structure-directing template. The compounds were characterized by X-ray powder diffraction, scanning electron microscopy, MAS NMR spectroscopy, differential thermal, and thermogravimetric analyses. The inorganic layers of APO-Ln are composed of PO4, AlO4, and AlO6 structural units, and the ratio of the octahedral Al to the tetrahedral Al in the as-synthesized compounds is about 1:1. APO-Ln exhibit a distinct weight loss when treated at elevated temperatures, and upon dehydration they adsorb a considerable amount of water. Dehydration−rehydration for APO-Ln materials is reversible with the dehydrated samples containing almost only tetrahedrally coordinated aluminum.

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“…The distribution of Al atoms in phyllosilicates can be estimated from the structural formula which is calculated from chemical analyses data. The solid state 27 Al NMR has been used to distinguish between the tetrahedral and octahedral Al in phyllosilicates. − However, presence of impurity affects the accuracy of determination; especially in the case of Al NMR, paramagnetic elements prevent the accuracy of determination.…”

Section: Introductionmentioning

confidence: 99%

“…The solid state 27 Al NMR has been used to distinguish between the tetrahedral and octahedral Al in phyllosilicates. [7][8][9][10][11][12][13] However, presence of impurity affects the accuracy of determination; especially in the case of Al NMR, paramagnetic elements prevent the accuracy of determination.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of XPS and DFT with Reference to the Distributions of Al in Tetrahedral and Octahedral Sheets of Phyllosilicates

Ebina¹,

Iwasaki²,

Chatterjee³

et al. 1997

J. Phys. Chem. B

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Five phyllosilicate samples of dioctahedral smectite, mica, magnesium chlorite, saponite, and hectorite were studied using X-ray photoelectron spectroscopy (XPS) to determine the distribution of Al in the tetrahedral and octahedral sheets. The binding energies of the Al(2p) peaks in all the samples were obtained at 74.5 and 73.7 eV for octahedral and tetrahedral Al, respectively. The ratio of the peak areas follows the same trend as that of octahedral Al present in the phyllosilicate lattice. To confirm the experimental result, localized cluster models were generated from the pyrophyllite structure to calculate their density of states by the density functional theory (DFT). The DFT results match very well with XPS results with respect to the difference of binding energies of Al in the tetrahedral and octahedral sheet of phyllosilicates; so this method is a useful tool to measure the qualitative distribution of Al in the phyllosilicates.

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Characterizations of MAPO-36 molecular sieve by solid-state n.m.r.

Cited by 18 publications

References 7 publications

NMR Spectroscopic Analysis of the Local Structure of Porous-Type Amorphous Alumina Prepared by Anodization

NMR Spectroscopic Analysis of the Local Structure of Porous-Type Amorphous Alumina Prepared by Anodization

Synthesis and Characterization of a Family of Amine-Intercatalated Lamellar Aluminophosphates from Alcoholic System

Comparative Study of XPS and DFT with Reference to the Distributions of Al in Tetrahedral and Octahedral Sheets of Phyllosilicates

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