Ag/La_(0.6)Sr_(0.4)MnO_3基催化剂上CH_3OH和CO的完全氧化

COMPLETE OXIDATION OF CH_3OH AND CO AT LOW CONCENTRATIONS OVER Ag/La_(0.6)Sr_(0.4)MnO_3-BASED CATALYSTS

合成了Ag/La0 6 Sr0 4 MnO3和Ag/La0 6 Sr0 4 MnO3/γ -Al2 O3两系列催化剂 ;发现钙钛矿型La0 6 Sr0 4 MnO3对低浓度CH3OH或CO的完全氧化显示出相当高的催化活性 ,适量Ag对钙钛矿型La0 6 Sr0 4 MnO3基质的修饰使其对CH3OH或CO完全氧化催化活性获明显提高 ;在 6%Ag/2 0 %La0 6 Sr0 4 MnO3/γ -Al2 O3催化剂上 ,CH3OH完全氧化的T95温度可低至 4 1 3K ,反应尾气中CH3OH氧化中间产物HCHO和CO的含量在检测极限以下 ;而在相同反应条件下在 1 %Pd/γ -Al2 O3和 1 %Pt/γ -Al2 O3催化剂上 ,CH3OH完全氧化的T95温度分别为 5 1 2和 4 68K ,相应反应尾气中HCHO含量分别为 2 0 0× 1 0 -6 和 63 0× 1 0 -6 ;对比考察了这些催化剂的耐热性能和操作稳定性 ,并结合XRD、XPS和H2 -TPR的表征结果 。

The Ag/La 0 6 Sr 0 4 MnO 3 and Ag/La 0 6 Sr 0 4 MnO 3/γ-Al 2O 3 catalysts were prepared and their catalytic performance for complete oxidation of CH 3OH and CO at low concentrations were evaluated The results showed that the La 0 6 Sr 0 4 MnO 3 catalyst displayed considerably high catalytic activities for complete oxidation of CH 3OH and CO at low concentrations and that 6%Ag-modification to La 0 6 Sr 0 4 MnO 3 host catalyst resulted in the enhancement of the activities for the catalytic complete oxidation of CH 3OH and CO, decreasing the T 95 (the reaction temperatures required for the conversion of 95% CH 3OH or CO) to 421 and 370K from 465 and 420K for the corresponding Ag-unmodified system, respectively Over a 6%Ag/20%La 0 6 Sr 0 4 MnO 3/γ-Al 2O 3 catalyst, T 95 temperature for the CH 3OH oxidation was further lowered to 413K, and even at so low reaction temperatures the contents of HCHO and CO in the reaction-exit gas were under the GC-detectable limits, while over the 0 1%Pd/γ-Al 2O 3 and 0 1%Pt/γ-Al 2O 3 catalysts the contents of HCHO in the reaction-exit gases remained at the levels of about 200×10 -6 and 630×10 -6 at their T 95 temperatures respectively The nature of interaction of Ag-dopant with the surface of the La 0 6 Sr 0 4 MnO 3 host catalyst with the perovskite structure was discussed together with the results of XRD, XPS and H 2-TPR characterizations of the catalysts