Ru/γ-Al_2O_3和Ru/AC催化剂的制备及其对氨氧化反应的催化性能

分别以γ-Al_2O_3和活性炭(AC)为载体,采用浸渍法制备了Ru质量分数均为2.0%的Ru/γ-Al_2O_3和Ru/AC催化剂,并用X射线衍射仪和透射电子显微镜等方法对催化剂结构进行了表征.实验结果表明:Ru/AC中Ru沉积在AC表面,分散度较低;而Ru/γ-Al_2O_3中Ru进入到γ-Al_2O_3内部,形成了一种高度分散体系.Ru/γ-Al_2O_3对氨的催化活性高于Ru/AC,氨在Ru/γ-Al_2O_3和Ru/AC上的起活温度分别为200 ℃和266 ℃,T_(90)(氨去除率达90%时的反应温度)分别为267℃和320 ℃.随混合气体空速增大,Ru/γ-Al_2O_3催化剂的T_(90)逐渐升高,气体空速分别为3 600,4 800,5 400 h~(-1)时,T_(90)分别为235,266,303 ℃.随反应前混合气体中氨质量分数增加,氨的去除率降低.

Preparation of Ru/γ-Al_2O_3 and Ru/AC Catalysts and Their Catalytic Capabilities on Oxidation of Ammonia

Using γ-Al_2O_3 and activated carbon (AC) as carriers, the catalysts Ru/γ-Al_2O_3 and Ru/ AC with 2. 0% of Ru mass concentration were prepared by dipping method, and characterized by means of XRD and TEM. The experimental results indicate that: In Ru/AC, Ru atoms only locate on the surface of AC with a lower dispersion; However, in Ru/γ-Al_2O_3, Ru atoms enter into γ-Al_2O_3 and form a high- dispersion system. The catalytic capability of Ru/γ-Al_2O_3 on oxidation of ammonia is higher than that of Ru/AC; The light-off temperature of ammonia on the catalyst Ru/γ-Al_2O_3 is 200 ℃, and that on the catalyst Ru/AC is 266 ℃, and T_(90)(reaction temperature for 90% of ammonia removal rate) is 267 ℃ and 320 ℃, respectively. The T_(90) on the catalyst Ru/γ-Al_2O_3 increases with the increasing of the gas space velocity, which is 235, 266, 303 ℃ when the gas space velocity is 3 600, 4 800, 5 400 h~(-1), respectively. The ammonia removal rate decreases with the increasing of the initial ammonia mass fraction in the mixed gas.