Preferential CO oxidation in H2-rich stream over Au/CeO2 catalysts prepared via modified deposition-precipitation

摘要

Preferential CO oxidation in a H2-rich stream over Au/CeO2 catalysts prepared via modified deposition-precipitation by using different precipitating agents at various pH values was investigated in this research work. The prepared catalysts were characterized by XRD, TEM, XRF, BET, TPR, UV-vis, and FTIR. The experimental results showed that the Au/CeO2 catalysts prepared by using NaOH as a precipitating agent at pH 7 expressed the highest catalytic activities (complete conversion and 51% selectivity at 40 °C) due to its well-dispersed nano-size Au particles on the support surface with narrower particle size distribution. When adding CO2 to the feed stream, the catalytic performance was decreased dramatically due to the formation of the formate species. The co-addition of CO2 and H2O in the feedstream had a less negative effect on the CO oxidation compared to the effect of CO2 alone. Water can attack and decompose the carbonate intermediate; the accumulation of the formate species on the active sites of the catalysts is then decreased and the catalytic performance is improved. After in situ thermal regeneration under 5% oxygen in helium at 110 °C for 2 h, more active sites for the preferential CO oxidation reaction were recovered since the oxygen reacted with the formate species to form CO2. In addition, the Au/CeO2 catalysts exhibited good stability during the tested time in this study.