Characterization of the acid sites in MCM-41-type materials by spectroscopic and catalytic techniques

Hunger, Michael; Schenk, Udo; Breuninger, Marcus; Gläser, Roger; Weitkamp, Jens

doi:10.1016/s1387-1811(98)00260-1

Cited by 103 publications

(60 citation statements)

References 35 publications

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“…3.5 ppm, attributed to bound water [33], was also observed. It is known from the previous work [23,34,35] on MCM-41 that the asymmetric shape of these signals is a hint for the presence of different types of silanol groups, such as isolated and geminal SiOH groups and internal SiOH groups.…”

Section: H Mas Nmr Spectroscopymentioning

confidence: 96%

Sulfated zirconia in SBA-15 structures with strong Brønsted acidity as observed by 1H MAS NMR spectroscopy

et al. 2007

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In order to prepare high surface area highly acidic catalysts, different weight loadings of ZrO 2 were incorporated in the SBA-15 structures which are subsequently sulfated by treating in 0.25 M H 2 SO 4 . The catalysts were characterized by means of TEM, XRD, N 2 adsorption, and 1 H MAS NMR. Brønsted type acidities of sulfated zirconia included SBA-15 materials were identified by a sharp 1 H MAS NMR line at 10.6 ppm. The highest acidity was obtained in the 25 mol% ZrO 2 included SBA-15 catalyst with a BET surface area of 246 m 2 /g.

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Section: H Mas Nmr Spectroscopymentioning

confidence: 96%

Sulfated zirconia in SBA-15 structures with strong Brønsted acidity as observed by 1H MAS NMR spectroscopy

et al. 2007

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“…The existence of these silanol groups can be easily determined by IR spectroscopy of the silica samples previously submitted to water removal. [37] The specific density of the silanol groups per gram of silica depends on many factors including surface area, procedure of silica formation, incomplete condensation of neighbouring silanols and thermal pretreatment of the silica at high temperatures. Even though silanol groups can also be in the interior of the silica particles, silanols together with silanoxy groups ( Si À O À Si bridges), are the natural terminal groups of the silicas at the solid surface.…”

Section: Silanol Groups and Covalent Bindingmentioning

confidence: 99%

Silica‐Bound Homogenous Catalysts as Recoverable and Reusable Catalysts in Organic Synthesis

2006

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Very frequently the most costly components in a chemical reaction are not the starting materials or the reaction products, but the catalyst. In addition to the advantages from the economic point of view, recovery and reuse of the catalyst is equally important in order to avoid wastes, so improving the greenness of the process. There is a current tendency to transform homogeneous into heterogeneous catalysis, that will even be accelerated in the near future. Starting from a successful homogeneous catalyst, one general methodology allowing its recovery and reuse is to immobilize a suitable derivative of the active catalyst on an insoluble solid support. When the catalyst does not deactivate and is sufficiently stable under the reaction conditions, the ultimate immobilization methodology is to attach covalently the catalytically active species to the support. In this contribution, after introducing some general principles describing the fundamentals of the covalent anchoring, the emphasis is placed more on giving an overview of the most important types of covalently anchored catalysts, including Brçnsted and Lewis acids, covalently anchored bases and hydrogenation complexes. Hot topics such as silica-bound organocatalysts and the application of periodic mesoporous organosilicas as heterogeneous catalysts is also covered.

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“…However, the MCM6 and MCM17 were kept in a closed container, which has room temperature water vapor pressure, for 1 month. This was done to reduce the formation of extra framework aluminum that was shown to be a reversible process [18].…”

Section: Materials Synthesis and Characterizationmentioning

confidence: 99%

“…Other studies have used X-ray photoelectron spectroscopy (XPS) to investigate surface modifications of ZSM5 [10][11][12][13][14][15] and mesoporous MCM-41 compounds (pore size between 2.0 and 50 nm) [16,17]. NMR and hexane cracking have been widely used to study many aluminosilicate compounds [2,[18][19][20].…”

Section: Introductionmentioning

confidence: 99%

“…Al-MCM-41, could be possible candidates for such reactants. However, Al-MCM-41 compounds suffer from their weak acidity and their weak thermal stability at high temperatures (500 8C) [2,18]. Aluminum is believed to be removed from the tetrahedral framework positions forming extra framework aluminum, which decreases the amount of bridging OH groups (Si-OH-Al) on the surface.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Surface and bulk investigation of ZSM5 and Al-MCM-41 using synchrotron XPS, XANES, and hexane cracking

Jalil¹,

Kariapper²,

Faiz³

et al. 2005

Applied Catalysis A: General

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Characterization of the acid sites in MCM-41-type materials by spectroscopic and catalytic techniques

Cited by 103 publications

References 35 publications

Sulfated zirconia in SBA-15 structures with strong Brønsted acidity as observed by 1H MAS NMR spectroscopy

Sulfated zirconia in SBA-15 structures with strong Brønsted acidity as observed by 1H MAS NMR spectroscopy

Silica‐Bound Homogenous Catalysts as Recoverable and Reusable Catalysts in Organic Synthesis

Surface and bulk investigation of ZSM5 and Al-MCM-41 using synchrotron XPS, XANES, and hexane cracking

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