Characterization and carbon monoxide oxidation activity of La1.ySryCr1.xRuxO3 perovskites
The oxidation of CO over La1-y Sr y Cr1-xRuxO3 perovskite type oxides with y=0.3 and 0 £x £0.100 have been studied. X-ray fluorescence analysis confirmed that content of elements in the bulk corresponds to the established nominal perovskite stoichiometry, indicating that no significant o...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Serbian Chemical Society
2000-01-01
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| Series: | Journal of the Serbian Chemical Society |
| Subjects: | |
| Online Access: | http://www.doiserbia.nb.rs/img/doi/0352-5139/2000/0352-51390001015T.pdf |
| Summary: | The oxidation of CO over La1-y Sr y Cr1-xRuxO3 perovskite type oxides with
y=0.3 and 0 £x £0.100 have been studied. X-ray fluorescence analysis
confirmed that content of elements in the bulk corresponds to the
established nominal perovskite stoichiometry, indicating that no significant
oxidation of ruthenium into volatile polyvalent oxides with their
consequented escape from the sample occurred in air up to the temperature of
1000ºC. According to X-ray diffraction analysis, all sampls achieved the
perovskite hexagonal with the presence of some SrCrO4. X-ray photoelectron
spectroscopy analysis of ruthenium samples shows higher Ru and Sr surface
concentrations than in the bulk. The binding energy for Ru3p is virtually
the same in all samples and consistent with that of Ru 4+ (463.6.464.3eV).
Kinetic studies were performed in a differential recycle reactor with a
recycling ratio 80. The results show that substitution of Ru 4+ for Cr 3+ in
La1-y Sr y CrO3 leads to a significant increase in both the activity and the
activation energy. The global CO oxidation rate, referred on the BET surface
area, correlates with the surface Ru 4+ atomic concentration. Hence, the
activity reflect the surface enrichment in ruthenium. Moreover, an identical
apparent activation energy E = 93 kJ/mol and the same specific rate per
ruthenium surface ion were obtained for samples with a Ru content x ‡ 0.05
suggest that exposed Ru 4+ ions mainly participate in the reaction. |
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| ISSN: | 0352-5139 1820-7421 |