Al Organization in the SSZ-13 Zeolite. Al Distribution and Extraframework Sites of Divalent Cations

0503931 - ÚFCH JH 2020 RIV US eng J - Journal Article
Mlekodaj, Kinga - Dědeček, Jiří - Pashkova, Veronika - Tabor, Edyta - Klein, Petr - Urbanová, Martina - Karcz, R. - Sazama, Petr - Whittleton, Sarah R. - Thomas, Haunani M. - Fishchuk, Anna V. - Sklenák, Štěpán
Al Organization in the SSZ-13 Zeolite. Al Distribution and Extraframework Sites of Divalent Cations.
Journal of Physical Chemistry C. Roč. 123, č. 13 (2019), s. 7968-7987. ISSN 1932-7447. E-ISSN 1932-7455
R&D Projects: GA ČR(CZ) GA17-00742S; GA ČR(CZ) GA15-14007S; GA MŠMT(CZ) LM2015073
Grant - others:Ga MŠk(CZ) LM2015070
Institutional support: RVO:61388955
Keywords : SSZ-13 zeolite * catalysis * zeolites
OECD category: Physical chemistry
Impact factor: 4.189, year: 2019
Method of publishing: Limited access

SSZ-13 is a Si-rich (Si/Al > 5) small pore zeolite (chabazite topology) important for both acid and redox catalysis. Using a sample with Si/Al = 12, a new procedure involving 27Al (3Q) MAS NMR spectroscopy and extensive periodic DFT calculations with molecular dynamics, in addition to the standard methods based on bare Co(II) cations as probes monitored by FTIR spectroscopy and UV-vis spectroscopy, was employed. The placement of the Al-O-(Si-O)2-Al and Al-O-(Si-O)3-Al sequences in the zeolite framework was determined (Al-O-Si-O-Al sequences are absent). 54% of the framework Al atoms correspond to Al-O-(Si-O)3-Al sequences which cannot form cationic sites for bare divalent cations but are able to accommodate divalent Co(II) hexaaqua complexes. The corresponding Al-O-(Si-O)3-Al sequence is located in two double 6-ring cages with one Al located in the 4-ring connecting two double 6-ring units. Our study also reveals that 35% of the framework Al atoms can accommodate neither divalent Co(II) hexaaqua complexes nor bare divalent cations. Furthermore, the siting of the Al atoms of the Al-O-(Si-O)2-Al and Al-O-(Si-O)3-Al sequences forming four cationic sites for divalent cations located in the 6-ring (Al-O-(Si-O)2-Al), 8-ring (Al-O-(Si-O)2-Al and Al-O-(Si-O)3-Al), and double 6-ring (Al-O-(Si-O)2-Al) was determined. These Al atoms correspond to a minority of the Al framework atoms.
Permanent Link: http://hdl.handle.net/11104/0295697