TY - JOUR
T1 - A density functional theory study of molecular and dissociative adsorption of H2 on active sites in mordenite
AU - Benco, Lubomir
AU - Bucko, Tomas
AU - Hafner, Juergen
AU - Toulhoat, Hervé
N1 - DOI: 10.1021/jp0533729
Coden: JPCBF
Affiliations: Institut für Materialphysik, Center for Computational Materials Science, Universität Wien, Sensengasse 8, A-1090 Wien, Austria; Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dubravska cesta 9, SK-84236 Bratislava, Slovakia; Institut Français du Pétrole, F- 92852 Rueil-Malmaison Cedex, France
Adressen: Benco, L.; Institut für Materialphysik; Center for Computational Materials Science; Universität Wien; Sensengasse 8 A-1090 Wien, Austria; email: [email protected]
Import aus Scopus: 2-s2.0-29144472185
22.10.2007: Datenanforderung 1935 (Import Sachbearbeiter)
22.10.2007: Datenanforderung 1936 (Import Sachbearbeiter)
PY - 2005
Y1 - 2005
N2 - Adsorption and chemisorption of H2 in mordenite is studied using ab initio density functional throry (DFT) calculations. The geometries of the adsorption complex, the adsorption energies, stretching frequencies, and the capacity to dissociate the adsorbed molecule are compared for different active sites. The active centers include a Brønsted acid site, a three-coordinated surface Al site, and Lewis sites formed by extraframework cations: Na+, Cu+, Ag+, Zn2+, Cu2+, Ga3+, and Al3+. Adsorption properties of cations are compared for a location of the cation in the five-membered ring. This location differs from the location in the six-membered ring observed for hydrated cations. The five-membered ring, however, represents a stable location of the bare cation. In this position any cation exhibits higher reactivity compared with the location in the six-membered ring and is well accessible by molecules adsorbed in the main channel of the zeolite. Calculated adsorption energies range from 4 to 87 kJ/mol, depending on electronegativity and ionic radius of the cation and the stability of the cation-zeolite complex. The largest adsorption energy is observed for Cu+ and the lowest for Al3+ integrated into the interstitial site of the zeolite framework. A linear dependence is observed between the stretching frequency and the bond length of the adsorbed H2 molecule. The capacity of the metal-exchanged zeolite to dissociate the H2 molecule does not correlate with the adsorption energy. Dissociation is not possible on single Cu+ cation. The best performance is observed for the Ga 3+, Zn2+, and Al3+ extraframework cations, in good agreement with experimental data. Œ 2005 American Chemical Society.
AB - Adsorption and chemisorption of H2 in mordenite is studied using ab initio density functional throry (DFT) calculations. The geometries of the adsorption complex, the adsorption energies, stretching frequencies, and the capacity to dissociate the adsorbed molecule are compared for different active sites. The active centers include a Brønsted acid site, a three-coordinated surface Al site, and Lewis sites formed by extraframework cations: Na+, Cu+, Ag+, Zn2+, Cu2+, Ga3+, and Al3+. Adsorption properties of cations are compared for a location of the cation in the five-membered ring. This location differs from the location in the six-membered ring observed for hydrated cations. The five-membered ring, however, represents a stable location of the bare cation. In this position any cation exhibits higher reactivity compared with the location in the six-membered ring and is well accessible by molecules adsorbed in the main channel of the zeolite. Calculated adsorption energies range from 4 to 87 kJ/mol, depending on electronegativity and ionic radius of the cation and the stability of the cation-zeolite complex. The largest adsorption energy is observed for Cu+ and the lowest for Al3+ integrated into the interstitial site of the zeolite framework. A linear dependence is observed between the stretching frequency and the bond length of the adsorbed H2 molecule. The capacity of the metal-exchanged zeolite to dissociate the H2 molecule does not correlate with the adsorption energy. Dissociation is not possible on single Cu+ cation. The best performance is observed for the Ga 3+, Zn2+, and Al3+ extraframework cations, in good agreement with experimental data. Œ 2005 American Chemical Society.
U2 - 10.1021/jp0533729
DO - 10.1021/jp0533729
M3 - Article
SN - 1520-6106
VL - 109
SP - 22491
EP - 22501
JO - The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
JF - The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
IS - 47
ER -