A Magnetic Resonance Study of the Fe2O3/Al2O3 Catalyst in a CO–N2O Reaction

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Abstract
A magnetic resonance study was performed in order to determine the phase of iron oxide supported on Al2O3 and to measure in situ the surface conditions during the reaction. The irreversible transition of α-Fe2O3 into Fe3O4 by the reduction of the supported catalyst and the reversible transition between Fe3O4 and γ-Fe2O3 were confirmed at 280 °C. The spectrum appearing at g=2.03 and having the line width of about 1000 gauss clearly showed ferrimagnetic behavior; it could be attributed to the ferrimagnetic resonance (FMR) of Fe3O4 and/or γ-Fe2O3. Kinetic study suggested that the CO–N2O reaction took place in the oxidation-reduction mechanism. The concentration of γ-Fe2O3 was calculated from not only the kinetic equation, but also the in situ measurement of the FMR signal; these values were consistent. The γ-Fe2O3/Al2O3 had nearly the same activity as the α-Fe2O3/Al2O3, whereas the unsupported γ-Fe2O3 had a lower activity than the α-Fe2O3. Such a difference in catalytic activity was discussed in comparison with other oxidation reactions.