Abstract
Catalysts of Pt on Fe2O3 and mixed oxides FexZr(1−x)O2 were prepared for the selective CO+H2 oxidation. X-ray diffraction and Mössbauer spectroscopy showed α-Fe2O3 in pure support, a solid solution for x=0.25 and mixed oxides with segregated phases for higher “x” values. Mössbauer results showed also that with increasing the Zr content Zr4+ ions substitute the Fe3+ ions in the α-Fe2O3 lattice, and also Fe3+ ions diffusing into the zirconia lattice. The Pt/Fe0.25Zr0.75O2(p) exhibited only Fe3+ inside the ZrO2 lattice. After reduction, Fe3O4 was found in the catalysts, which decreased with increasing zirconium loading. It is interesting to note that the corresponding precursor presents 83% of Fe3+ located in the ZrO2 lattice and the remaining 17% corresponds to hematite.Catalytic tests for the preferential oxidation of CO containing H2 showed a maximum CO conversion at different temperatures after reaching total oxygen conversion. The CO conversion decreased with increasing iron content in the mixed oxide. The Pt/Fe2O3 catalyst is the most active compared to the other Pt/mixed oxide and Pt/ZrO2. Results showed the following order: Pt/Fe2O3(c)>Pt/Fe0.75Zr0.25O2(c)>Pt/Fe0.25Zr0.75O2(c)>Pt/ZrO2. The Pt/Fe0.25Zr0.75O2(c) presented high selectivity (56%) at 90°C and is 2-fold higher compared to the Pt/Fe2O3 and Pt/ZrO2 catalyst.
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