Recrystallisation of mesoporous SBA-15 into microporous ZSM-5
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| Title: | Recrystallisation of mesoporous SBA-15 into microporous ZSM-5 |
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| Authors: | Campos, A.A.1, Dimitrov, L., da Silva, C.R.1, Wallau, M. martin_wallau@ufpel.edu.br, Urquieta-González, E.A.1 urquieta@power.ufscar.br |
| Source: | Microporous & Mesoporous Materials. Oct2006, Vol. 95 Issue 1-3, p92-103. 12p. |
| Subjects: | Crystallization, Isomerization, Glycerin, X-ray diffraction |
| Abstract: | Abstract: SBA-15 was impregnated with tetrapropylammonium hydroxide and sodium aluminate and subsequently recrystallised under autogenous pressure in glycerol containing different amounts of water. Under the studied conditions, the formation of ZSM-5 was observed only in the presence of glycerol containing 30 or more wt.% of water. In the particular case of glycerol containing 30wt.% of water, ZSM-5 structural units were observed by FTIR spectroscopy in a still X-ray amorphous solid after 12h. However, when ZSM-5 could be detected by X-ray diffraction, scanning electron microscopy showed that the SBA-15 particles and the ZSM-5 crystals are segregated. 27Al MAS NMR of the X-ray amorphous sample containing ZSM-5 structural units demonstrates that aluminium is mainly in tetrahedral co-ordination. Nevertheless, the observed chemical shift was lower than that observed for crystalline ZSM-5, thus indicating that the aluminium sites in this amorphous recrystallised sample are different from the aluminium sites in ZSM-5. The activity of the predominantly amorphous recrystallised samples in the isomerisation of m-xylene was lower than that of samples containing predominantly crystalline ZSM-5. For the latter, an enhanced selectivity towards p-xylene was observed, indicating that the reaction occurs on Brønsted sites in the shape-selective micropores of the ZSM-5 structure. For the predominantly amorphous recrystallised samples an o/p-xylene ratio higher than one indicates that in this case the isomerisation occurs by a bimolecular transalkylation on non-selective sites. However, the activity of the SBA-15 samples recrystallised in the presence of aluminium is lower than that over SBA-15 recrystallised under comparable conditions, but in the absence of aluminium. This indicates that the enhanced activity of the latter might be due to an enhanced hydrophobicity caused by dehydroxylation of the pore surface during the recrystallisation process which could be observed by FTIR spectroscopy. A higher hydrophobicity could enhance the adsorption of the organic substrate and this concentration effect would be responsible for the enhanced activity observed on the recrystallised samples without or low ZSM-5 content. Taking into account that dehydroxylation of the pore surface might be achieved by much simpler thermal treatment and that the ZSM-5 crystallised as segregated phase, the studied recrystallisation method seems not able to yield improved catalysts for the transformation of bulky molecules as it was expected. [Copyright &y& Elsevier] |
| Copyright of Microporous & Mesoporous Materials is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 22580032 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Recrystallisation of mesoporous SBA-15 into microporous ZSM-5 – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Campos%2C+A%2EA%2E%22">Campos, A.A.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Dimitrov%2C+L%2E%22">Dimitrov, L.</searchLink><br /><searchLink fieldCode="AR" term="%22da+Silva%2C+C%2ER%2E%22">da Silva, C.R.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Wallau%2C+M%2E%22">Wallau, M.</searchLink><i> martin_wallau@ufpel.edu.br</i><br /><searchLink fieldCode="AR" term="%22Urquieta-González%2C+E%2EA%2E%22">Urquieta-González, E.A.</searchLink><relatesTo>1</relatesTo><i> urquieta@power.ufscar.br</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Microporous+%26+Mesoporous+Materials%22">Microporous & Mesoporous Materials</searchLink>. Oct2006, Vol. 95 Issue 1-3, p92-103. 12p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Crystallization%22">Crystallization</searchLink><br /><searchLink fieldCode="DE" term="%22Isomerization%22">Isomerization</searchLink><br /><searchLink fieldCode="DE" term="%22Glycerin%22">Glycerin</searchLink><br /><searchLink fieldCode="DE" term="%22X-ray+diffraction%22">X-ray diffraction</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: SBA-15 was impregnated with tetrapropylammonium hydroxide and sodium aluminate and subsequently recrystallised under autogenous pressure in glycerol containing different amounts of water. Under the studied conditions, the formation of ZSM-5 was observed only in the presence of glycerol containing 30 or more wt.% of water. In the particular case of glycerol containing 30wt.% of water, ZSM-5 structural units were observed by FTIR spectroscopy in a still X-ray amorphous solid after 12h. However, when ZSM-5 could be detected by X-ray diffraction, scanning electron microscopy showed that the SBA-15 particles and the ZSM-5 crystals are segregated. 27Al MAS NMR of the X-ray amorphous sample containing ZSM-5 structural units demonstrates that aluminium is mainly in tetrahedral co-ordination. Nevertheless, the observed chemical shift was lower than that observed for crystalline ZSM-5, thus indicating that the aluminium sites in this amorphous recrystallised sample are different from the aluminium sites in ZSM-5. The activity of the predominantly amorphous recrystallised samples in the isomerisation of m-xylene was lower than that of samples containing predominantly crystalline ZSM-5. For the latter, an enhanced selectivity towards p-xylene was observed, indicating that the reaction occurs on Brønsted sites in the shape-selective micropores of the ZSM-5 structure. For the predominantly amorphous recrystallised samples an o/p-xylene ratio higher than one indicates that in this case the isomerisation occurs by a bimolecular transalkylation on non-selective sites. However, the activity of the SBA-15 samples recrystallised in the presence of aluminium is lower than that over SBA-15 recrystallised under comparable conditions, but in the absence of aluminium. This indicates that the enhanced activity of the latter might be due to an enhanced hydrophobicity caused by dehydroxylation of the pore surface during the recrystallisation process which could be observed by FTIR spectroscopy. A higher hydrophobicity could enhance the adsorption of the organic substrate and this concentration effect would be responsible for the enhanced activity observed on the recrystallised samples without or low ZSM-5 content. Taking into account that dehydroxylation of the pore surface might be achieved by much simpler thermal treatment and that the ZSM-5 crystallised as segregated phase, the studied recrystallisation method seems not able to yield improved catalysts for the transformation of bulky molecules as it was expected. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Microporous & Mesoporous Materials is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.micromeso.2006.05.006 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 12 StartPage: 92 Subjects: – SubjectFull: Crystallization Type: general – SubjectFull: Isomerization Type: general – SubjectFull: Glycerin Type: general – SubjectFull: X-ray diffraction Type: general Titles: – TitleFull: Recrystallisation of mesoporous SBA-15 into microporous ZSM-5 Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Campos, A.A. – PersonEntity: Name: NameFull: Dimitrov, L. – PersonEntity: Name: NameFull: da Silva, C.R. – PersonEntity: Name: NameFull: Wallau, M. – PersonEntity: Name: NameFull: Urquieta-González, E.A. IsPartOfRelationships: – BibEntity: Dates: – D: 18 M: 10 Text: Oct2006 Type: published Y: 2006 Identifiers: – Type: issn-print Value: 13871811 Numbering: – Type: volume Value: 95 – Type: issue Value: 1-3 Titles: – TitleFull: Microporous & Mesoporous Materials Type: main |
| ResultId | 1 |
