TY - JOUR
T1 - Extraframework aluminum species in zeolites: Ab initio molecular dynamics simulation of gmelinite
AU - Benco, Lubomir
AU - Demuth, T.
AU - Hafner, Juergen
AU - Hutschka, Francois
AU - Toulhoat, Hervé
N1 - DOI: 10.1006/jcat.2002.3631
Affiliations: Institut für Materialphysik, Ctr. for Computational Mat. Science, Universität Wien, Sensengasse 8, A-1090 Vienna, Austria
Adressen: Benco, L.; Institut für Materialphysik; Ctr. for Computational Mat. Science; Universität Wien; Sensengasse 8 A-1090 Vienna, Austria; email: [email protected]
Import aus Scopus: 2-s2.0-0036306844
22.10.2007: Datenanforderung 1935 (Import Sachbearbeiter)
22.10.2007: Datenanforderung 1936 (Import Sachbearbeiter)
PY - 2002
Y1 - 2002
N2 - The dynamical behavior of extraframework aluminum particles (EFAL) in zeolites has been investigated using a first-principles molecular dynamics technique. Small clusters of hydrated aluminum hydroxide Al(OH)3(H2O)3 and Al(OH)3(H2O) are located both in the main channel and in the cage. The simulation of the hexacoordinated cluster at T = 300 K shows an overcoordination of the central atom and a release of H2O molecules. When placed in the main channel both the EFAL and the noncoordinated H2O molecules are mobile. When placed in the cage, a network of hydrogen bonds is established, occluding the EFAL and suppressing its mobility. The basic character of the EFAL causes an exchange of Brønsted acid protons between the zeolite and the EFAL particle. In a high-acidity zeolite a multiple, simultaneous proton exchange is observed, leading to a separation of charges (EFAL2+, zeolite2-). The calculated stretching OH frequencies of the EFAL are ?60 cm-1 higher than those of the Brønsted OH, in good agreement with IR measurements. Œ 2002 Elsevier Science (USA).
AB - The dynamical behavior of extraframework aluminum particles (EFAL) in zeolites has been investigated using a first-principles molecular dynamics technique. Small clusters of hydrated aluminum hydroxide Al(OH)3(H2O)3 and Al(OH)3(H2O) are located both in the main channel and in the cage. The simulation of the hexacoordinated cluster at T = 300 K shows an overcoordination of the central atom and a release of H2O molecules. When placed in the main channel both the EFAL and the noncoordinated H2O molecules are mobile. When placed in the cage, a network of hydrogen bonds is established, occluding the EFAL and suppressing its mobility. The basic character of the EFAL causes an exchange of Brønsted acid protons between the zeolite and the EFAL particle. In a high-acidity zeolite a multiple, simultaneous proton exchange is observed, leading to a separation of charges (EFAL2+, zeolite2-). The calculated stretching OH frequencies of the EFAL are ?60 cm-1 higher than those of the Brønsted OH, in good agreement with IR measurements. Œ 2002 Elsevier Science (USA).
U2 - 10.1006/jcat.2002.3631
DO - 10.1006/jcat.2002.3631
M3 - Article
SN - 0021-9517
VL - 209
SP - 480
EP - 488
JO - Journal of Catalysis
JF - Journal of Catalysis
IS - 2
ER -