Ternary Oxide Catalysts CoMCeO(M=Mn,Zr) Used For CO Preferential Oxidation

CO preferential oxidation?CO-PROX?is considered to be currently the most economical and effective approach for the removal of trace CO in the hydrogen rich gas.In this paper,Co CeMnO catalysts with different Mn doping amount and CoCeZrO catalysts with different Zr doping amount were prepared,and the CO-PROX activity of the catalysts were investigated.CoCeMnO catalysts with the Co/?Mn+Ce?molar ratio of 9:1 were prepared by one-step thermal decomposition of mixed oxalates.The effects of different Mn/?Mn+Ce?molar ratio on the catalytic activity of CO-PROX reaction were investigated.The catalysts were characterized using BET,XRD,Raman,HRTEM,H₂-TPR,XPS,O₂-TPD,and Co K-edge XAFS techniques.The structure properties of the catalyst,the redox ability and the state of cobalt species were elaborated.The relationship between the properties and the catalytic activity of the catalyst was discussed.The results showed that the catalyst Co₉Ce_0.8Mn_0.2 with the Mn/?Mn+Ce?molar ratio of 0.2 displayed the best catalytic activity for the CO-PROX.The conversion of CO to CO₂ and the selectivity of O₂ over the catalyst Co₉Ce_0.8Mn_0.2 are more than 96 % in the temperature range of 100-120 ?.The results of XRD and Raman showed that a ternary Co-Mn-Ce-O solid solution was formed in the catalysts,which enhanced the interaction of Co,Ce and Mn.The catalyst Co₉Ce_0.8Mn_0.2 has the best redox ability,the most of the surface adsorbed oxygen and lattice oxygen species.These factors are very beneficial for the CO-PROX reaction.CoCeZrO catalysts with the Co/?Zr+Ce?molar ratio of 9:1 were prepared by one-step thermal decomposition of mixed oxalates.The effects of Zr doping on the catalytic activity of CoCeZrO catalyst for CO-PROX reaction were investigated.The catalysts were characterized using BET,XRD,TEM,and H₂-TPR techniques.The structure properties of the catalyst,the redox ability and the state of cobalt species were elaborated.The relationship between the properties and the catalytic activity of the catalyst was discussed.The results showed that the catalyst Co₉Ce_0.85Zr_0.15 with the Zr/?Zr+Ce?molar ratio of 0.15 displayed the best catalytic activity for the CO-PROX.CO can be completely transformed at 110 ?,and the selectivity of O₂ to CO₂ maintained 100 % at the temperature below 100 ?.The catalyst Co₉Ce_0.85Zr_0.15 has the largest specific surface area,and active sites can be exposed more than the other CoCeZrO catalyst.The catalyst Co₉Ce_0.85Zr_0.15 has the best redox properties.These factors are very beneficial for the CO-PROX reaction.According to the above results,the stability test was carried out at 120 ? for 53 h over the catalyst Co₉Ce_0.8Mn_0.2 which has the best catalytic activity in the two catalyst systems.The test results showed that the conversion of CO and the selectivity of O₂ to CO₂ remains 100 %,which indicated this catalyst has the advantage of good stability.However,the addition of H₂ O and CO₂ exhibited obvious negative influence on the catalytic performance,which not only made the temperature rise of CO complete transformation,but also narrowed the complete CO conversion window.