Title: Understanding the reactivity and basicity of zeolites: A periodic DFT study of the disproportionation of N2O4 on alkali-cation-exchanged zeolite Y
Authors: Mignon, Pierre ×
Pidko, Evgeny A
Van Santen, Rutger A
Geerlings, Paul
Schoonheydt, Robert #
Issue Date: 2008
Publisher: VCH Verlagsgesellschaft
Series Title: Chemistry - a European Journal vol:14 issue:17 pages:5168-5177
Abstract: The disproportionation of N2O4 into NO3- and NO+ on Y zeolites has been studied through periodic DFT calculations to unravel 1) the role of metal cations and the framework oxygen atoms and 2) the relationship between the NO+ stretching frequency and the basicity of zeolites. We have considered three situations: adsorption on site II cations with and without a cation at site III and adsorption on a site III cation. We observed that cations at sites II and III cooperate to stabilize N2O4 and that the presence of a cation at site III is necessary to allow the disproportionation reaction. The strength of the stabilization is due to the number of stabilizing interactions increasing with the size of the cation and to the Lewis acidity of the alkali cations, which increases as the size of the cations decreases. In the product, NO3- interacts mainly with the cations and NO+ with the basic oxygen atoms of the tetrahedral aluminium through its nitrogen atom. As the cation size increases, the NO3-center dot center dot center dot cation interaction increases. As a result, the negative charge of the framework is less well screened by the larger cations and the interaction between NO+ and the basic oxygen atoms becomes stronger. NO+ appears to be a good probe of zeolite basicity, in agreement with experimental observations.
Description: R1298
ISSN: 0947-6539
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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