Brønsted acidity of Al/SBA-15

A.J.J. Koekkoek, J.A.R. Veen, van, P.B. Gerritsen, P. Giltay, P.C.M.M. Magusin, E.J.M. Hensen

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Abstract

To increase the content of well-dispersed aluminium in Al/SBA-15 and its Brønsted acidity, a water-free synthesis method involving a Si-O-Al precursor was employed to preparea series of Al/SBA-15 of widely varying composition. The materials were characterized with ICP, BET, TEM, 27Al MAS NMR and IR spectroscopy and compared to conventionally prepared Al/SBA-15. For low Al content (Si/Al >10),the conventional approach leads to highly dispersed, predominantly isolated Al with well-ordered mesopores.Athigher Al content, the order decreasedor was even completely lost.In general, this led to the agglomeration of Al species on the surface. Although in most cases a substantial part of Al atomsexhibit tetrahedral coordination indicating their high dispersion and interaction with the silica, the overall Brønsted acidity of these Al/SBA-15-type materials is very low. The overall acidity of all Al/SBA-15 is of the same order as amorphous silica-alumina. By IR spectroscopy of H/D exchange with perdeuterobenzene, it was found that the intrinsic acidity of the acid sites in Al/SBA-15 is similar to that in zeolites and amorphous silica-alumina, thus further confirming that acid site concentration dominates differences in acidity of aluminosilicas.
Original languageEnglish
Pages (from-to)34-43
JournalMicroporous and Mesoporous Materials
Volume151
DOIs
Publication statusPublished - 2012

Fingerprint

Acidity
acidity
Silicon Dioxide
Silica
silicon dioxide
Aluminum Oxide
Infrared spectroscopy
Alumina
aluminum oxides
acids
Acids
Zeolites
agglomeration
zeolites
spectroscopy
Nuclear magnetic resonance spectroscopy
Aluminum
Agglomeration
SBA-15
Transmission electron microscopy

Cite this

Koekkoek, A.J.J. ; Veen, van, J.A.R. ; Gerritsen, P.B. ; Giltay, P. ; Magusin, P.C.M.M. ; Hensen, E.J.M. / Brønsted acidity of Al/SBA-15. In: Microporous and Mesoporous Materials. 2012 ; Vol. 151. pp. 34-43.
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abstract = "To increase the content of well-dispersed aluminium in Al/SBA-15 and its Br{\o}nsted acidity, a water-free synthesis method involving a Si-O-Al precursor was employed to preparea series of Al/SBA-15 of widely varying composition. The materials were characterized with ICP, BET, TEM, 27Al MAS NMR and IR spectroscopy and compared to conventionally prepared Al/SBA-15. For low Al content (Si/Al >10),the conventional approach leads to highly dispersed, predominantly isolated Al with well-ordered mesopores.Athigher Al content, the order decreasedor was even completely lost.In general, this led to the agglomeration of Al species on the surface. Although in most cases a substantial part of Al atomsexhibit tetrahedral coordination indicating their high dispersion and interaction with the silica, the overall Br{\o}nsted acidity of these Al/SBA-15-type materials is very low. The overall acidity of all Al/SBA-15 is of the same order as amorphous silica-alumina. By IR spectroscopy of H/D exchange with perdeuterobenzene, it was found that the intrinsic acidity of the acid sites in Al/SBA-15 is similar to that in zeolites and amorphous silica-alumina, thus further confirming that acid site concentration dominates differences in acidity of aluminosilicas.",
author = "A.J.J. Koekkoek and {Veen, van}, J.A.R. and P.B. Gerritsen and P. Giltay and P.C.M.M. Magusin and E.J.M. Hensen",
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Brønsted acidity of Al/SBA-15. / Koekkoek, A.J.J.; Veen, van, J.A.R.; Gerritsen, P.B.; Giltay, P.; Magusin, P.C.M.M.; Hensen, E.J.M.

In: Microporous and Mesoporous Materials, Vol. 151, 2012, p. 34-43.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Brønsted acidity of Al/SBA-15

AU - Koekkoek, A.J.J.

AU - Veen, van, J.A.R.

AU - Gerritsen, P.B.

AU - Giltay, P.

AU - Magusin, P.C.M.M.

AU - Hensen, E.J.M.

PY - 2012

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N2 - To increase the content of well-dispersed aluminium in Al/SBA-15 and its Brønsted acidity, a water-free synthesis method involving a Si-O-Al precursor was employed to preparea series of Al/SBA-15 of widely varying composition. The materials were characterized with ICP, BET, TEM, 27Al MAS NMR and IR spectroscopy and compared to conventionally prepared Al/SBA-15. For low Al content (Si/Al >10),the conventional approach leads to highly dispersed, predominantly isolated Al with well-ordered mesopores.Athigher Al content, the order decreasedor was even completely lost.In general, this led to the agglomeration of Al species on the surface. Although in most cases a substantial part of Al atomsexhibit tetrahedral coordination indicating their high dispersion and interaction with the silica, the overall Brønsted acidity of these Al/SBA-15-type materials is very low. The overall acidity of all Al/SBA-15 is of the same order as amorphous silica-alumina. By IR spectroscopy of H/D exchange with perdeuterobenzene, it was found that the intrinsic acidity of the acid sites in Al/SBA-15 is similar to that in zeolites and amorphous silica-alumina, thus further confirming that acid site concentration dominates differences in acidity of aluminosilicas.

AB - To increase the content of well-dispersed aluminium in Al/SBA-15 and its Brønsted acidity, a water-free synthesis method involving a Si-O-Al precursor was employed to preparea series of Al/SBA-15 of widely varying composition. The materials were characterized with ICP, BET, TEM, 27Al MAS NMR and IR spectroscopy and compared to conventionally prepared Al/SBA-15. For low Al content (Si/Al >10),the conventional approach leads to highly dispersed, predominantly isolated Al with well-ordered mesopores.Athigher Al content, the order decreasedor was even completely lost.In general, this led to the agglomeration of Al species on the surface. Although in most cases a substantial part of Al atomsexhibit tetrahedral coordination indicating their high dispersion and interaction with the silica, the overall Brønsted acidity of these Al/SBA-15-type materials is very low. The overall acidity of all Al/SBA-15 is of the same order as amorphous silica-alumina. By IR spectroscopy of H/D exchange with perdeuterobenzene, it was found that the intrinsic acidity of the acid sites in Al/SBA-15 is similar to that in zeolites and amorphous silica-alumina, thus further confirming that acid site concentration dominates differences in acidity of aluminosilicas.

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DO - 10.1016/j.micromeso.2011.11.019

M3 - Article

VL - 151

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JO - Microporous and Mesoporous Materials

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