Post-synthetic activation of silanol covering in the mesostructured silicate materials МСМ-41 and SBA-15

Kozlova, Svetlana A.; Кирик, С. Д.

doi:10.1016/j.micromeso.2010.04.024

Cited by 67 publications

(53 citation statements)

References 37 publications

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“…For SBA-15, the maximum coverage that could be achieved in one grafting step (using a precursor concentration equal to 1.0 Ce/nm 2 ) was 0.55 Ce/nm 2 , in accordance with the observation that SBA-15 usually contains a higher surface density of hydroxyl groups. 73 51CeiPM prepared by refluxing the Ce(O i Pr) 4 solution in contact with the support had a slightly higher coverage than expected, possibly due to errors in the ICP analysis or the BET surface area measurement of the support. The complete grafting for this precursor under reflux might indicate that higher temperatures facilitate Ce(O i Pr) 4 agglomeration and, thus, the attainment of higher surface coverages.…”

Section: ' Introductionmentioning

confidence: 82%

Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties

2011

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An investigation was performed to establish the effects of precursor composition on the structure of ceria deposited onto mesoporous silicas, MCM-41 and SBA-15. The structure of the deposited ceria was characterized by XRD, TEM, Raman and UV-visible spectroscopy, XANES, and EXAFS. Using Ce(acac) 3 as the precursor resulted in formation of 3 nm diameter ceria particles located predominantly in the mouths of the support pores. Amorphous agglomerates, but with domains of comparable size to those obtained using Ce(acac) 3 , were obtained using Ce(O i Pr) 4 . Much smaller domains and a high degree of dispersion were obtained using Ce(O t Bu) 4 as the precursor. The structure of the deposited ceria affects its reduction-reoxidation properties. Reduction and reoxidation are almost fully reversible for the nanoparticles. Only surface reduction is observed up to 723 K, whereas partial bulk reduction takes place at higher reduction temperatures. In case of the well-dispersed, layerlike Ce species on the silica surface, an extent of reduction similar to that of the nanoparticles is achievable, but upon heating the samples in 10% H 2 /He to 923 K the reduction becomes partially irreversible. The latter effect might be explained by a formation of cerium silicates that prevent the complete reoxidation of the cerium species. ' INTRODUCTIONDispersion of a transition metal oxide on a high surface area support such as Al 2 O 3 or SiO 2 makes it possible to combine the catalytic properties of the transition metal oxide with the high surface area and thermal and mechanical stability of the support. 1 Good illustrations of the manner in which the transition metal oxide is introduced onto the support and the physical properties of the deposited oxide are given for the cases of TiO x , 1-9 VO x , 5,[9][10][11][12][13][14] or MoO x 10,11,15-21 dispersed on high surface area supports. A notable consequence of this approach is the formation of catalytically active sites which are not present on either the support or the bulk transition metal oxide. For example, neither TiO 2 nor SiO 2 is active for the liquid-phase epoxidation of alkenes, but TiO 2 /SiO 2 exhibits high activity and selectivity for this reaction. 6,[22][23][24] The appearance of such novel catalytically active sites has been attributed to the formation of a twodimensional oxide overlayer whose physical properties differ from those of the corresponding bulk oxide. Dispersed transition metal oxides have also been shown to stabilize the dispersion of small metal particles and to enhance the activity of supported metal oxo species. For example, Au particles have been shown to be much more stable on TiO x /SiO 2 than on SiO 2 25 and isolated vanadate species dispersed on TiO x /SiO 2 exhibit turnover frequencies that are up to 60-fold higher than when dispersed on SiO 2 . 7 CeO 2 is a highly reducible oxide exhibiting oxygen storage and release properties that are important for the operation of threeway, automotive exhaust catalysts. 26 It can also stabilize the dispersion of n...

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Section: ' Introductionmentioning

confidence: 82%

Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties

2011

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“…However, depending on the method used to remove the organic template in order to produce the mesoporous silica the surface characteristics may be altered [94,95,158]. Calcination is the most common and efficient method to remove the template.…”

Section: Silanol Density On the Silica Surfacementioning

confidence: 99%

Enzymes immobilized in mesoporous silica: A physical–chemical perspective

Carlsson

Gustafsson

Thörn

et al. 2014

Advances in Colloid and Interface Science

222

167

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“…Calcination is the most commonly used method; however, it causes the conversion of some hydrophilic silanol groups into hydrophobic siloxane groups affecting enzyme confinement inside the support pores 27,30 . This can be avoided by extracting the template with ethanol which preserves the silanol groups; but some template remains inside the pores limiting the lodgment of enzymes inside the voids 31,32 . Using an HNO 3 -H 2 O 2 mixture completely removes the pluronic P123 from SBA-15 and leaves a high density of silanol groups exposed in the support 33 .…”

Section: Influence Of the Environment Inside The Porementioning

confidence: 99%

Engineering of Supported Nanomaterials

2014

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This brief review analyzes the parameters that can be used to guide the generation of hierarchic systems that include inorganic and/or biological nanoscale objects. Importance of interface effects and geometrical factors are underlined. The mutual influence between the substrate and the deposited material is an important factor to determine the most appropriate set of parameters for the synthesis of nanomaterials with desirable properties for industrial applications

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Post-synthetic activation of silanol covering in the mesostructured silicate materials МСМ-41 and SBA-15

Cited by 67 publications

References 37 publications

Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties

Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties

Enzymes immobilized in mesoporous silica: A physical–chemical perspective

Engineering of Supported Nanomaterials

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Post-synthetic activation of silanol covering in the mesostructured silicate materials МСМ-41 and SBA-15

Cited by 67 publications

References 37 publications

Synthesis of Different CeO2 Structures on Mesoporous Silica and Characterization of Their Reduction Properties

Synthesis of Different CeO2 Structures on Mesoporous Silica and Characterization of Their Reduction Properties

Enzymes immobilized in mesoporous silica: A physical–chemical perspective

Engineering of Supported Nanomaterials

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Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties

Synthesis of Different CeO₂ Structures on Mesoporous Silica and Characterization of Their Reduction Properties