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Comparative study of selective CO oxidation over Pt-Co-M/ $Al_2O_3$ catalysts (M=Ce, Mg, Mn, Zr, Fe) in hydrogen-rich streams: effects of a second promoter

The selective CO oxidation over Pt-Co/Al 2O3 catalyst in hydrogen-rich streams was studied in the presence of Ce, Mg, Mn, Ze, and Fe as the second promoters. The catalysts were prepared using incipient to wetness co-impregnation, and tested in a microflow reaction system. The effects of the second promoter were investigated in near 100% CO conversion conditions both in the absence and presence of $CO_2$ and H2O in the feed. 100% CO conversion was obtained with the addition of each second promoter at 110 $^{circ}C$ while Pt-Co/$Al_2O_3$ catalyst had 96%-98% CO conversion. It was also found that changing the Pt ratio from 1.4 wt.% to 0.7 wt.% at 110 $^{circ}C$ did not have any significant effects on catalysts containing Ce, Mg, or Mn, and it had negative effects in the case of Fe and Zr. The CO conversion decreased for all the catalysts in the presence of 25% $CO_2$ in the feed as expected, and recovered fully or significantly with the addition of 10% $H_2O$. The addition of Ce, Mg, and Mn as the second promoter also improved the performance 2%-3% compared to Pt-Co/$Al_2O_3$ catalysts in the presence of CO and $H_2O$. The increase in the reaction temperature to 130 $^{circ}C$ decreased the CO conversion over all the catalysts.

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