催化剂Pd/γ-Al_2O_3上Pd的双态行为

The Dual States of Pd on Catalyst Pd/γ-Al_2O_3

采用模拟配气系统和 XPS技术研究了活化气体的氧化还原特性对催化剂中 Pd质量分数为 7%的 Pd/γ- Al2 O3催化活性的影响 .得出 :催化剂经过贫燃保持 /贫燃下降或富燃保持 /贫燃下降处理后 ,催化剂失活 ,表面钯以 Pd O形式存在 ;经过贫燃保持 /富燃下降 ,富燃保持 /富燃下降 ,或富燃保持 /等化学计量下降处理后 ,催化剂被活化 ,表面钯以Pd0 形式存在 .Pd0 的钯对混合配气的催化活性比 Pd O的高得多 .催化剂活性具有可逆性 .等化学计量的气体具有保持催化剂活性的功能 .

Effects of different reduction atmospheres on the catalytic activity of 7% Pd/γ Al 2O 3 catalyst were investigated using simulated exhaust gas and XPS. The results are: Once the catalysts were treated by lean hold/lean down or rich hold/lean down step, the catalyst lost their activities and Palladium particles on the catalysts existed in oxidation states. While the catalysts treated by lean hold/rich down, rich hold/rich down or stoichiometric steps, these catalysts were activated and Palladium particles on the catalysts occurred in metallic states. The catalytic activity of Pd 0 was higher than that of PdO in the experimental condition. The activity of this kind of catalyst was reversible. Stoichiometric gas could keep the activity of the catalyst.