负载Ni催化剂表面Ni的形态及其甲烷化活性研究

Study of surface Ni nature and methanation performance of Ni catalysts

采用浸渍法制备了具有不同Ni负载量的NiO/γ-Al2O3催化剂,经过不同温度下的焙烧处理后得到一系列共9个催化剂样品。借助X射线光电子能谱分析比较Ni负载量和焙烧处理温度对Ni在催化剂载体表面存在的形态。结果表明,对于Ni负载量为10%的样品,Ni离子会在催化剂表面以八面体配位的镍和表面尖晶石NiAl2O4的形态存在,随着焙烧温度的提高,以表面尖晶石NiAl2O4形式存在的Ni的比例也增加;当Ni负载量达到20%以上,以NiO形态存在的Ni会更多的出现在催化剂表面,而提高焙烧温度不利于NiO的存在。CO甲烷化微反评价的结果显示,表面富集NiO的催化剂具有更好的甲烷化催化活性。

A series of Ni supported NiO/T-A12 03 catalysts are prepared by impregnating method. The amount of Ni loaded on the NiO/T-A1203 and calcining temperature on the surface Ni nature are investigated by X-Ray photoelectron spectroscopy. The results show that there are two kinds of Ni existences on the surface of NiO/T-A1203 catalysts withl0 wt. % Ni loading,octahedral site nickel and surface NiA12Q. Furthermore, the amount of Ni in ＂surface NiA12O4 is increased with the increase in calcining temperature. As Ni loading is beyond 20 wt. % , Ni in form of NiO is formed on the sample surface gradually. Increasing the calcining temperature is unfavorable for the existence of NiO on the surface. The testing results of methanation show that samples with more NiO on surface have better catalytic activity.