W dniach od 2 kwietnia do 5 kwietnia 2024 r. prowadzone będą prace związane z wdrożeniem nowej wersji systemu Repozytorium UJ. Nie będzie możliwe wprowadzanie nowych informacji do repozytorium. Za utrudnienia przepraszamy.
IR studies of OH groups in mesoporous aluminosilicates
pl
dc.type
JournalArticle
pl
dc.description.physical
104-109
pl
dc.abstract.en
The properties of acidic hydroxyl groups and Lewis acid sites in amorphous mesoporous aluminosilicates was followed by quantitative IR studies of ammonia adsorption and by low temperature studies of CO adsorption. We studied aluminosilicates synthesized by three methods: via atrane complexes, by grafting aluminium onto the siliceous material (HMCM-48) and in aqueous solution following a typical synthesis procedure (HMCM-41). IR spectra of OH groups showed weak but well seen band of Si-(OH)-Al groups at $3600–3610cm^{-1}$. The post-synthesis grafting of Al into MCM-48 was found to be the most effective way to produce mesoporous material with large content of Brønsted acid sites. IR studies have shown that the stoichiometry of dehydroxylation of the amorphous mesoporous materials was different than for zeolites: in mesoporous materials one Brønsted site lost created one Lewis acid site. IR experiments of CO sorption evidenced that generally two kinds of Si-(OH)-Al groups exist in mesoporous aluminosilicates: weakly acidic ones of $\Delta v_{OH\cdots CO} \approx160cm^{-1}$ (similar to that in zeolite NaHX), present in all the materials, hydroxyls of moderate acidity of $\Delta v_{OH\cdots CO} \approx200cm^{-1}$ (acid strength intermediate between that in zeolites NaHX and NaHY) present in HMCM-41 and HMCM-48, or hydroxyls of high acidity of $\Delta v_{OH\cdots CO} \approx300cm^{-1}$ (similar to that in highly siliceous zeolite HZSM-5) present in aluminoslicate prepared via atrane complexes method. This method of synthesis was found to be the most effective in preparation of mesoporous aluminosilicates with the strongest Brønsted acid sites. The weakly acidic hydroxyls in mesoporous aluminosilicates are very prone to dehydroxylation, they are lost at as low temperature as 800 K, hydroxyls of moderate, or high acidity are resistant to dehydroxylation and behave like zeolitic OH groups.
pl
dc.subject.en
acidity
pl
dc.subject.en
OH groups
pl
dc.subject.en
mesoporous materials
pl
dc.subject.en
dehydroxylation
pl
dc.subject.en
IR spectroscopy
pl
dc.description.volume
302
pl
dc.description.number
1
pl
dc.identifier.doi
10.1016/j.apcata.2005.12.027
pl
dc.identifier.eissn
1873-3875
pl
dc.title.journal
Applied Catalysis. A, General
pl
dc.language.container
eng
pl
dc.affiliation
Wydział Chemii : Zakład Chemii Nieorganicznej
pl
dc.subtype
Article
pl
dc.rights.original
bez licencji
pl
Pliki tej pozycji
Plik
Rozmiar
Format
Przeglądanie
Nie ma plików powiązanych z tą pozycją.
Pozycja umieszczona jest w następujących kolekcjach