Characterization of Al- and Ti-modified MCM-41 using adsorption techniques

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dc.contributor.authorRosenholm, J. B.en
dc.contributor.authorRahiala, H.en
dc.contributor.authorPuputti, J.en
dc.contributor.authorStathopoulos, V.en
dc.contributor.authorPomonis, P.en
dc.contributor.authorBeurroies, I.en
dc.contributor.authorBackfolk, K.en
dc.date.accessioned2015-11-24T16:53:40Z
dc.date.available2015-11-24T16:53:40Z
dc.identifier.issn0927-7757-
dc.identifier.urihttps://olympias.lib.uoi.gr/jspui/handle/123456789/10051
dc.rightsDefault Licence-
dc.subjectmesoporous silicateen
dc.subjectmcm-41en
dc.subjectal- and ti-surface modificationen
dc.subjectlewis and bronsted acid-baseen
dc.subjectsurface charge densityen
dc.subjectadsorption isothermen
dc.subjectcalorimetryen
dc.subjectnh3-tpden
dc.subjectdriften
dc.subjectmesoporous molecular-sievesen
dc.subjectsolid-solution interfaceen
dc.subjectsilicon-nitride powdersen
dc.subjectsurface-chemistryen
dc.subjectthermogravimetric analysisen
dc.subjectthermoporometryen
dc.subjectpolymerizationen
dc.subject(hydr)oxidesen
dc.subjectcatalysisen
dc.subjectbehavioren
dc.titleCharacterization of Al- and Ti-modified MCM-41 using adsorption techniquesen
heal.abstractThe influence of aluminium and titanium dopants on the structure and properties of MCM-41 silica has been evaluated and compared with previously published results. The acidity and basicity of the surface states (adsorption sites) were of special interest. The total acidity was studied by using temperature-programmed ammonia desorption (NH3-TPD). Additionally, organic probe molecules with known Lewis and/or Brphinsted acid or base functional groups were adsorbed on the powder samples in dry cyclohexane. Both UV-vis spectroscopy and microcalorimety were used to quantity the adsorption. The adsorption data of the monofunctional probes were fitted with Langmuir-, Freundlich-and Henry-corrected Langmuir isotherms providing both the number of the surface sites and strength of probe molecule adsorption. The surface charge densities, relating to Brphinsted acidity and basicity. were determined for the doped samples in water using potentiometric titration. DRIFT spectroscopy was used to identify the type of the surface sites. The hexagonal pore structure of the doped MCM-41 samples was observed to remain roughly unaltered for all samples. The NH3-TPD analysis indicates that the acidity increases as a result of modification. The probe adsorption showed that the number of sites increases and the strength of adsorption enhances with surface modification. It seems that the simple Langmuir-isotherm is sufficient for the Surface state analysis in most cases. In a few cases, the Freundlich- or the Henry-corrected Langmuir isotherm gave, however, a superior fit to the experimental surface excess data. The DRIFT-analysis confirmed the existence of Lewis sites and the formation of Brphinsted type acid sites with enhanced Al- or Ti-doping, which was supported by the other methods used. (C) 2004 Elsevier B.V. All rights reserved.en
heal.accesscampus-
heal.fullTextAvailabilityTRUE-
heal.identifier.primaryDOI 10.1016/j.colsurfa.2004.04.086-
heal.identifier.secondary<Go to ISI>://000226157000041-
heal.identifier.secondaryhttp://ac.els-cdn.com/S0927775704005047/1-s2.0-S0927775704005047-main.pdf?_tid=439603945f7b940de90a6ce1d179ef9a&acdnat=1333036654_65c7c7dcd78d427862e867b7e796b220-
heal.journalNameColloids and Surfaces a-Physicochemical and Engineering Aspectsen
heal.journalTypepeer reviewed-
heal.languageen-
heal.publicationDate2004-
heal.publisherElsevieren
heal.recordProviderΠανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείαςel
heal.typejournalArticle-
heal.type.elΆρθρο Περιοδικούel
heal.type.enJournal articleen

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