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本文用EXAFS、XRD实验方法研究了负载在η-Al_2O_3和Si_2载体上的镍、铁金属及Ni-Fe双全属催化剂的结构,TPR技术考察载体和加入的第二组分铁对镍还原峰温度的影响。结果表明η-Al_2O_3载体与金属的相互作用比相应SiO_2的大,Ni-Fe双金属催化剂形成镍铁合金晶粒.bcc结构α-Fe的CO_2加氢甲烷化活性很低,Ni-Fe双金属催化剂中fcc结构铁的活性相当高,与镍的活性相近,认为是bcc结构α-Fe的表面层铁原子间距离2.87A,较fcc结构铁的长0.39A,使H_2难于形成的解离吸附所致。在相同反应温度下Ni-Fe/SiO_2催化剂的活性比Ni-Fe/η-Al_2O_3催化剂的小几倍的主要原因是Ni-Fe/SiO_2催化剂的Ni-Fe合金晶粒中铁在表面偏析的程度大和仍带有部分bcc结构α-Fe的性质。
In this paper, the structures of Ni, Fe and Ni-Fe catalysts supported on η-Al 2 O 3 and Si 2 O were investigated by EXAFS and XRD. The effect of TPR on the structure, Impact. The results show that the interaction between η-Al 2 O 3 support and metal is larger than that of SiO 2, and the Ni-Fe bimetallic catalyst forms Ni-Fe alloy grains. The CO 2 hydromethanation activity of α-Fe in bcc structure is very low, and the Ni-Fe bimetallic catalyst The activity of iron in fcc structure is quite high, which is similar to the activity of nickel. It is considered that the distance between iron atoms in the surface layer of bcc structure α-Fe is 2.87A, which is 0.39A longer than that of fcc structure iron, making it difficult for H 2 to form dissociative adsorption To The main reason why the activity of Ni-Fe / SiO 2 catalyst is several times smaller than that of Ni-Fe / η-Al 2 O 3 catalyst at the same reaction temperature is that the Ni-Fe / SiO 2 catalyst has a large degree of segregation of iron on the surface in the Ni- Still with partial bcc structure α-Fe properties.