| Abstract
| - The preferential CO oxidation (PROX) on a Ru/Al2O3 catalyst was investigated at 115−185 °C in the presenceof 21−75 ppm NH3. With an increase in [O2]/[CO] ratios, the CO conversion decreased, though it increasedin the absence of NH3. In the presence of NH3, the catalytic activity was high at high temperature, whichindicates that O2 was consumed over the upstream of the catalyst bed and that the reaction atmosphere inmost portions of catalyst bed was reductive. Thus, a reduction atmosphere kept the catalyst active. For the H2oxidation without CO, the catalyst was immediately deactivated in the presence of NH3, which indicates thatthe activation of oxygen was suppressed. In the in-situ IR spectra, a band assigned to nitrosyls appearedduring the poisoning, and the intensity increased with time on stream. In addition, the band intensity ofmonocarbonyls decreased with an increase in that of multicarbonyls and nitrosyls. The presence ofmulticarbonyls indicates that the nitrosyls stabilized the oxidized Ru. In the presence of NH3, the oxidizedRu catalyst showed a low activity under an oxidation atmosphere, while the reduced Ru catalyst exhibited ahigh activity under a reduction atmosphere.
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