Studying the Structure and CO₂ Methanation of Ni-Fe Supported Bimetallic Catalysts

The structures of nickel, iron and Ni-Fe Bimetallic catalysts supported on alumina and silica were characterized by EXAFS, XRD. The nickel reduction peak temperature of catalysts affected by support and adding iron oxide was studied with TPR, the results indicate that interaction between metal and support on alumina is stronger than that on silica. Both nickel and iron form Ni-Fe alloy particles in Ni-Fe bimetallic catalysts. The activity of CO₂ methanation is lower in the fcc structural α-Fe, but there is a highly activity for the fcc structural Fe in the Ni-Fe catalysts, comparable to the activity of nickel catalysts. It is interpreted that the distance between the iron atom and the neighbor atom at the first layer of surface is 2.87Å in bcc structural α-Fe, which is 0.39Å longer than that of fcc structural Fe, so the bcc α-Fe is diffcult to disociate H₂. The activity of Ni-Fe SiO₂ catalyst is many times lower than that of Ni-Fe/η-A1₂O₃ catalyst at the same reaction temperature. It was believed that iron is more rich and exists some property of the bcc α-Fe on the surface of Ni-Fe alloy particles in the Ni-Fe SiO₂ catalyst.