ISSN:
1573-1111
Schlagwort(e):
Nitrogen monoxide
;
ESR spectroscopy
;
disproportionation reaction
;
CaHY-type zeclite
;
kinetics
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract An ESR spectroscopic study of adsorbed NO on CaHY-type zeolite was carried out and the kinetics are discussed on the basis of a mechanistic model of the disproportionation reaction. An amount of NO less than the amount of Ca2+ distributed in Site II of the faujasite structure was admitted onto the sample maintained at 373 K. ESR spectra were recorded at room temperature. The spectra consisted of well-resolved signals. It is proposed that NO molecules on CaHY-type zeolite have two kinds of adsorption patterns. The initial formation of N2O may be expressed by the following reactions: $$[ ] + NO\mathop \rightleftharpoons \limits_{}^{K_1 } [NO],[NO] + NO\mathop \rightleftarrows \limits_{\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftharpoonup}$}} {k} _2 }^{\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {K} _2 } [N_2 O_2 ],[N_2 O_2 ] + NO\mathop \to \limits_{}^{\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {K} _3 } [NO_2 ] + N_2 O,$$ where [], [NO] and [N2O2] denote vacant adsorption, NO adsorption, and N2O2 adsorption sites, respectively. A rate equation for N2O appearance (α) has been derived by a steady state approximation: $$\alpha = \frac{{\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {k} _3 K_1 K_2 P^3 }}{{1 + (K_1 + \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {k} _3 /\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftharpoonup}$}} {k} _2 )P + K_1 (K_2 + \overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\rightharpoonup}$}} {k} _3 /\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\leftharpoonup}$}} {k} _2 )P^2 }},$$ WhereP is the pressure of NO. The rate equation was used to explain the kinetic results of the disproportionation of NO.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00665372
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