Influence of H₂O and CO₂ on the selective CO oxidation in H₂-rich gases over Au/α-Fe₂O₃

详细信息    查看全文

• 作者：Schubert ; Markus M. ; Venugopal ; Akula ; Kahlich ; Michael J. ; Plzak ; Vojtech ; Behm ; R. Jü ; rgen
• 关键词：Selective CO oxidation ; PROX ; Gold catalysts ; Au/Fe₂O₃ ; CO₂ effects ; H₂O effects ; Carbonate formation ; Deactivation ; CO adsorption ; DRIFTS ; Kinetics
• 刊名：Journal of Catalysis
• 出版年：2004
• 出版时间：February 15, 2004
• 年：2004
• 卷：222
• 期：1
• 页码：32-40
• 全文大小：343 K

文摘

The effects of CO₂ and H₂O on the preferential CO oxidation in H₂-rich gases (PROX) over Au/α-Fe₂O₃ have been studied by kinetic and IR spectroscopic measurements at 80°C. Addition of CO₂ reduces the CO oxidation rate and the selectivity, which based on a blue shift of the linearly adsorbed CO in the IR spectra is attributed to coadsorption of CO₂ on the gold particles or at the gold–metal oxide interface. Furthermore, deactivation is accelerated due to increased carbonate formation on the catalyst surface. Addition of H₂O results in opposite effects. It increases the selectivity by suppressing the competing H₂ oxidation reaction. The CO oxidation rate is slightly accelerated. The deactivation is significantly diminished, which is ascribed to the transformation of surface carbonates into thermally less stable bicarbonate species. The extent of the effect of water addition depends strongly on the reaction temperature, being most pronounced at lower temperatures (40°C). Under realistic conditions (25 % CO₂, 10–15 % H₂O, 80°C) water reduces, but cannot completely compensate, the negative influence of CO₂ on the PROX performance compared to CO₂-free gas mixtures.