水汽-CO_2环境下Pt/CeZrO_2催化剂的CO氧化性能研究

Pt/CeZrO_2 Catalysts for CO Oxidation in Water Vapor-CO_2 Environment

采用浸渍法制备了Pt/Ce0.6Zr0.4O_2粉末催化剂,涂覆到蜂窝陶瓷载体表面得到整体式催化剂。考察了Pt含量及焙烧温度对催化剂在水汽-CO_2环境下催化CO氧化性能的影响,并用XRD,TEM和H2-TPR等手段对载体和催化剂进行了表征。结果表明,在空速50000 h-1的反应条件下,当焙烧温度为300℃时,3.0Pt/Ce0.6Zr0.4O_2整体式催化剂的CO氧化活性最高,反应温度200℃时,CO转化率为87%,具有较高的水汽-CO_2环境下的CO氧化活性。通过对2.0Pt/Ce0.6Zr0.4O_2催化剂在无水汽,无CO_2,无水汽-CO_2及水汽-CO_2环境下的对比实验,发现水汽和CO_2对催化剂的活性有明显的抑制作用,水汽的影响比CO_2的影响要更大一些。这说明水汽、CO_2和CO对催化剂存在竞争吸附。结合催化剂的H2-TPR表征结果,发现催化剂的还原能力越高,相对应的CO氧化活性也越高。添加适量的Pt有利于提高催化剂的还原能力,从而提高其活性,但是过量的Pt会使催化剂活性下降。

A series of PtYCe0.6Zr0.4O2 powder prepared by an impregnation method were coated to honeycomb ceramic carrier to produce monolithic catalysts. The effects of Pt content and calcination temperature on the catalytic performance of CO oxidation in water vapor-CO2 environment were investigated. It was found that under the reaction conditions of 50000 h^-1 GHSV, the 3.0Pt/Ce0.6Zr0.402 monolithic catalyst calcined at 300℃ exhibited the highest activity, with a CO conversion of 87 % at 200℃. By comparing the catalytic behaviors of the 2.0Pt/Ce0.6Zr0.4O2 catalyst in various reaction conditions, it was found that both the water vapor and CO2 obviously suppressed the activity, while the effect of water vapor was more significant than that of CO2. This implied competitive adsorptions among water vapor, CO2 and CO on the catalyst. The H2-TPR results indicated that the addition of proper amount of Pt in the catalyst could enhance the reducibility of the catalyst, which was beneficial to the improvement of the activity. However, excess of Pt content resulted in the decrease of activity.