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A Computational Study of the Translational Motion of Protons in Zeolite H-ZSM-5

Published online by Cambridge University Press:  18 March 2011

M.E. Franke ,
M. Sierka ,
J. Sauer  and
U. Simon
M.E. Franke
Affiliation:
Aachen University of Technology, Institute of Inorganic Chemistry, Professor Pirlet Str. 1, Aachen, Germany
M. Sierka
Affiliation:
Humboldt University of Berlin, Institute of Chemistry/Quantum Chemistry, Jägerstr. 10/11, Berlin, Germany
J. Sauer
Affiliation:
Humboldt University of Berlin, Institute of Chemistry/Quantum Chemistry, Jägerstr. 10/11, Berlin, Germany
U. Simon
Affiliation:
Aachen University of Technology, Institute of Inorganic Chemistry, Professor Pirlet Str. 1, Aachen, Germany
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Abstract

The potential energy profile for proton translational motions between two neighboring Alsites in zeolite H-ZSM-5 is calculated by a combined quantum mechanics-interatomic potential function approach. Thepotential energies of the six stable intermediate proton positions and the five transition structures along this path show an almost symmetrical trend reaching the maximum in the middle between these sites. Therefore, the maximum barrier will decrease with decreasing SiO2/Al2O3 ratio of thezeolite. For the SiO2/Al2O3 ratio examined (190) an activation energy of∼ 210 kJ/mol is calculated. This is much lower than the energy of deprotonation, about 1300 kJ/mol. The deprotonation energy of an Al-OH-Si bridge is obviously partially compensated by the proton affinity of the Si-O-Si bridges.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 658: Symposium GG – Solid-State Chemistry of Inorganic Materials III , 2000 , GG7.4
Copyright
Copyright © Materials Research Society 2001

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References

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