Q #1. In simulation of reactions in an automobile catalytic converter, the reaction
N2O + CO ? N2 + CO2 has been studied in a CSTR reactor at 1 atm and
300 °C, using a ceria-promoted rhodium catalyst. The data below were obtained in
a series of steady state runs made by varying the reactant composition.
Pco (atm)
PN20 (atm)
Rate (moles N2O/gcat-sec)
0.05
0.01
5.0 x 10-3
0.05
0.02
1.0 x 10-2
0.05
0.05
1.8 x 10-2
0.05
0.07
2.1 x 10-2
0.05
0.10
2.3 x 10-2
0.01
0.05
3.0 x 10-2
0.02
0.05
2.5 x 10-2
0.07
0.05
1.3 x 10-2
0.10
0.05
1.0 x 10-2
In order to explain these observations, the following reaction mechanism has been
proposed:
N2O + ?v ? ?N2O
?N2O ? N2 + ?o
CO + ?v ? ?CO
?CO + ?o ? CO2 + 2?v
In the above mechanism, note that second and fourth steps are irreversible,
whereas the first and third steps are reversible. Is this mechanism consistent with
the observed rate data? Which is the rate-limiting step? Derive a kinetic rate
expression based on the above Langmuir-Hinshelwood mechanism.
