The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5

dc.contributor.authorWeber, R W
dc.contributor.authorMöller, K P
dc.contributor.authorUnger, M
dc.contributor.authorO'Connor, C
dc.date.accessioned2016-08-05T10:37:15Z
dc.date.available2016-08-05T10:37:15Z
dc.date.issued1998
dc.date.updated2016-08-01T08:37:56Z
dc.description.abstractThe external acidity of ZSM-5 was modified by chemical vapour deposition (CVD) and chemical liquid deposition (CLD) of tetraethoxysilane [Si(OC2 H5 ) 4 ] using a static vacuum system, a vapour phase flow system and liquid phase deposition. Temperature programmed desorption (TPD) techniques were used to characterise the acidity changes arising from these modifications. Pyridine was used as a probe for the total acidity and 4-methyl quinoline (MQ) was used to probe the external acidity. The adsorption capacities of the samples were measured using n-hexane, p-xylene, o-xylene and 1,2,4-trimethyl benzene. The extent of Si(OC2 H5 ) 4 deposition was strongly dependent on temperature in both vapour phase flow and static vacuum systems. Continuous Si(OC2 H5 ) 4 deposition was observed in the presence of H2 O at relatively high temperatures when decomposition products were removed from the sample. It is proposed that physisorbed species need to be removed by evacuation or calcination to re-expose active sites, thereby enabling complete inertisation of the external surface acidity to occur, and that a more uniform covering can be obtained when a gradual deposition process is used. Such a process may be achieved by the use of diluents or by preventing overexposure of Si(OC2 H5 ) 4 to the sample under conditions where continuous deposition may occur. It was shown that it is possible to reduce the relative external surface acidity by 97% without significant changes in acidity as measured by Py-TPD or adsorption capacity.en_ZA
dc.identifierhttp://dx.doi.org/10.1016/S1387-1811(98)00061-4
dc.identifier.apacitationWeber, R. W., Möller, K. P., Unger, M., & O'Connor, C. (1998). The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5. <i>Microporous and Mesoporous Materials</i>, http://hdl.handle.net/11427/21133en_ZA
dc.identifier.chicagocitationWeber, R W, K P Möller, M Unger, and C O'Connor "The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5." <i>Microporous and Mesoporous Materials</i> (1998) http://hdl.handle.net/11427/21133en_ZA
dc.identifier.citationWeber, R. W., Möller, K. P., Unger, M., & O'Connor, C. T. (1998). The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5. Microporous and mesoporous materials, 23(3), 179-187.en_ZA
dc.identifier.issn1387-1811en_ZA
dc.identifier.ris TY - Journal Article AU - Weber, R W AU - Möller, K P AU - Unger, M AU - O'Connor, C AB - The external acidity of ZSM-5 was modified by chemical vapour deposition (CVD) and chemical liquid deposition (CLD) of tetraethoxysilane [Si(OC2 H5 ) 4 ] using a static vacuum system, a vapour phase flow system and liquid phase deposition. Temperature programmed desorption (TPD) techniques were used to characterise the acidity changes arising from these modifications. Pyridine was used as a probe for the total acidity and 4-methyl quinoline (MQ) was used to probe the external acidity. The adsorption capacities of the samples were measured using n-hexane, p-xylene, o-xylene and 1,2,4-trimethyl benzene. The extent of Si(OC2 H5 ) 4 deposition was strongly dependent on temperature in both vapour phase flow and static vacuum systems. Continuous Si(OC2 H5 ) 4 deposition was observed in the presence of H2 O at relatively high temperatures when decomposition products were removed from the sample. It is proposed that physisorbed species need to be removed by evacuation or calcination to re-expose active sites, thereby enabling complete inertisation of the external surface acidity to occur, and that a more uniform covering can be obtained when a gradual deposition process is used. Such a process may be achieved by the use of diluents or by preventing overexposure of Si(OC2 H5 ) 4 to the sample under conditions where continuous deposition may occur. It was shown that it is possible to reduce the relative external surface acidity by 97% without significant changes in acidity as measured by Py-TPD or adsorption capacity. DA - 1998 DB - OpenUCT DP - University of Cape Town J1 - Microporous and Mesoporous Materials LK - https://open.uct.ac.za PB - University of Cape Town PY - 1998 SM - 1387-1811 T1 - The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5 TI - The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5 UR - http://hdl.handle.net/11427/21133 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21133
dc.identifier.vancouvercitationWeber RW, Möller KP, Unger M, O'Connor C. The chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5. Microporous and Mesoporous Materials. 1998; http://hdl.handle.net/11427/21133.en_ZA
dc.languageengen_ZA
dc.publisherElsevieren_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsCreative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)*
dc.rights.urihttps://creativecommons.org/licenses/by-nc-nd/4.0/en_ZA
dc.sourceMicroporous and Mesoporous Materialsen_ZA
dc.source.urihttp://www.sciencedirect.com/science/journal/13871811
dc.subject.otherZSM-5
dc.subject.otherCVD
dc.subject.otherTPD
dc.subject.otherAdsorption
dc.subject.otherExternal surface
dc.titleThe chemical vapour and liquid deposition of tetraethoxysilane on the external surface of ZSM-5en_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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