Quantitative insight into aluminum structures in CaO–Al2O3–SiO2 system via Raman and 27Al MAS-NMR spectroscopies

As amostras de esmectita do estado do Pará, Amazônia, Brasil foram caracterizadas utilizando XRD, 27Al MAS NMR, FTIR e análise textural por curvas isotérmicas de adsorção-dessorção de nitrogênio. Na produção das argilas pilarizadas foi usado como íon intercalante, o Al13 (o íon de keggin), obtido pela reação das soluções AlC(l3)6H2O/NaOH, com razão molar OH/Al=2. Foram adotadas as proporções (Al/Argila): 5, 10, 20 e 25 meq/g de argila, com intercalação em 25 ºC, durante as 3 h e calcinada a 450 ºC (temperatura adequada da calcinação). O resultado mostrou que o processo de pilarização aumentou o espaçamento basal da argila natural de 14,02 para 18,84 Å e a área superficial de 44,30 para 198,03 m²/g (Al/Argila=25meq/g de argila, pH=4). O material preparado com relação Al/Argila=25meq/g de argila mostrou a incorporação máxima de Al. A estabilidade térmica da argila natural foi melhorada pelo procedimento de pilarização.

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THE USE OF THE COMBINATION OF FTIR, PYRIDINE ADSORPTION, 27Al AND 29Si MAS NMR TO DETERMINE THE BRÖNSTED AND LEWIS ACIDIC SITES

Jurnal Teknologi ◽

10.11113/jt.v78.8821 ◽

2016 ◽

Vol 78 (6) ◽

Cited By ~ 4

Author(s):

Djoko Hartanto ◽

Lai Sin Yuan ◽

Sestriana Mutia Sari ◽

Djarot Sugiarso ◽

Irmina Kris Murwarni ◽

...

Keyword(s):

Lewis Acid ◽

Aluminum Atom ◽

Xrd Analysis ◽

Acid Sites ◽

Mas Nmr ◽

Molar Ratio ◽

Pyridine Adsorption ◽

Lewis Acid Sites ◽

27Al Mas Nmr ◽

Pre Treatment

Lewis and Brönsted acidity were studied on ZSM-5 with combination of pyridine adsorption and FTIR vibration, ZSM-5 synthesized using kaolin Bangka Indonesia with an increase in the molar ratio of Si/Al 30-60 without pre-treatment and without organic templates and with seeds silicalite. Interestingly, the intensity of the infrared showed an increase of band vibration pyridine as absorbed Brönsted and Lewis acid sites in a molar ratio increase of Si/Al in ZSM-5, indicating an increase in the number of silanol (Brönsted acid) and deformed silica (Lewis acid) because the amount of Aluminum in ZSM-5 decrease with increase Si/Al but amount acidity increase. 29Si and 27Al MAS NMR analysis was supported by the results of infrared to indicate that all of the aluminum atom is coordinated with their neighbors are the same in ordering the ZSM-5 framework and 27Al MAS NMR showed a sharp peak of all the variations of Si/Al except the Si/Al 30 shows a low peak area. XRD analysis supported that the ZSM-5 structure formed is pure and crystal and a decrease in crystallinity proven for more than Si/Al 50, that defects silica occurs in ZSM-5, this corresponds to the growing number of Lewis acid sites caused by defects silica described the infrared results.

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27Al-MAS-NMR-Untersuchungen des thermischen Abbaus von NH4Al(SO4)2·12H2O / 27Al-MAS-NMR Studies on the Thermolysis of NH4Al(SO4)2· 12H2O

Zeitschrift für Naturforschung B ◽

10.1515/znb-1991-1110 ◽

1991 ◽

Vol 46 (11) ◽

pp. 1515-1518 ◽

Cited By ~ 2

Author(s):

Gerhard Wegner ◽

Gert Blumenthal ◽

Dirk Müller ◽

Dirk-Henning Menz ◽

Antje Schmalstieg

Keyword(s):

Nmr Spectroscopy ◽

Structural Changes ◽

Chemical Shifts ◽

Mas Nmr ◽

Nmr Studies ◽

High Stage ◽

27Al Mas Nmr ◽

High Resolution Nmr ◽

First Time

Products of the thermolysis of NH4Al-alum were prepared under dried air and characterized by X-ray powder diffraction, thermogravimetry, and for the first time by solid-state 27Al-MAS-NMR spectroscopy. It was found, that high resolution NMR spectroscopy is applicable to follow up the thermal decomposition and to indicate even minor structural changes. 27Al-MAS-NMR spectra show peaks with characteristic chemical shifts for octahedral Al-units up to a high stage of thermolysis. During the decomposition of Al2(SO4)3 to γ-Al2O3 we again observed three-peak spectra with the specific signal at ≈ 35 ppm for penta-coordinated Al ions as recently proved for the thermolysis of AlCl3 · 6 H2O.

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