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Location of Framework Al Atoms in the Channels of ZSM‐5: Effect of the (Hydrothermal) Synthesis
Author(s) -
Pashkova Veronika,
Sklenak Stepan,
Klein Petr,
Urbanova Martina,
Dědeček Jiří
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201503758
Subject(s) - zeolite , ion , zsm 5 , hydrothermal circulation , hydrothermal synthesis , intersection (aeronautics) , spectroscopy , crystallography , ring (chemistry) , chemistry , tetrahedron , materials science , catalysis , physics , chemical engineering , organic chemistry , quantum mechanics , engineering , aerospace engineering
27 Al 3Q MAS NMR and UV/Vis spectroscopy with bare Co II ions as probes of Al pairs in the zeolite framework were employed to analyze the location of framework Al atoms in the channel system of zeolite ZSM‐5. Furthermore, the effect of Na + ions together with tetrapropylammonium cation (TPA + ) in the ZSM‐5 synthesis gel on the location of Al in the channel system was investigated. Zeolites prepared using exclusively TPA + as a structure‐directing agent (i.e., in the absence of Na + ions) led to 55–90 % of Al atoms located at the channel intersection, regardless the presence or absence of Al pairs [Al−O−(Si−O) 2 −Al sequences in one ring] in the zeolite framework. The presence of Na + ions in the synthesis gel did not modify the Al location at the channel intersection (55–95 % of Al atoms) and led only to changes in i) the distribution of framework Al atoms between Al pairs (decrease) and single isolated Al atoms (increase), and ii) the siting of Al in distinguishable framework tetrahedral sites.