Characterization of Al- and Ti-modified MCM-41 using adsorption techniques
Φόρτωση...
Ημερομηνία
Συγγραφείς
Rosenholm, J. B.
Rahiala, H.
Puputti, J.
Stathopoulos, V.
Pomonis, P.
Beurroies, I.
Backfolk, K.
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Elsevier
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Colloids and Surfaces a-Physicochemical and Engineering Aspects
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
The 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.
Περιγραφή
Λέξεις-κλειδιά
mesoporous silicate, mcm-41, al- and ti-surface modification, lewis and bronsted acid-base, surface charge density, adsorption isotherm, calorimetry, nh3-tpd, drift, mesoporous molecular-sieves, solid-solution interface, silicon-nitride powders, surface-chemistry, thermogravimetric analysis, thermoporometry, polymerization, (hydr)oxides, catalysis, behavior
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://000226157000041
http://ac.els-cdn.com/S0927775704005047/1-s2.0-S0927775704005047-main.pdf?_tid=439603945f7b940de90a6ce1d179ef9a&acdnat=1333036654_65c7c7dcd78d427862e867b7e796b220
http://ac.els-cdn.com/S0927775704005047/1-s2.0-S0927775704005047-main.pdf?_tid=439603945f7b940de90a6ce1d179ef9a&acdnat=1333036654_65c7c7dcd78d427862e867b7e796b220
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας