CO methanation over supported bimetallic Ni–Fe catalysts: From computational studies towards catalyst optimization

Abstract

Abstract DFT calculations combined with a computational screening method have previously shown that bimetallic Ni–Fe alloys should be more active than the traditional Ni-based catalyst for CO methanation. That was confirmed experimentally for a number of bimetallic Ni–Fe catalysts supported on MgAl 2 O 4 . Here, we report a more detailed catalytic study aimed at optimizing the catalyst performance. For this purpose, two series of mono and bimetallic Ni–Fe catalysts supported on MgAl 2 O 4 and Al 2 O 3 , respectively, were prepared. All catalysts were tested in the CO methanation reaction in the temperature interval 200–300 °C, and characterized using elemental analysis, N 2 physisorption measurements, XRD and TEM. Optimization of the catalyst performance was made by varying the Ni:Fe ratio, the total metal loading and the support material. For both support materials, the bimetallic catalysts with compositions 25Fe75Ni and 50Fe50Ni showed significantly better activity and in some cases also a higher selectivity to methane compared with the traditional monometallic Ni and Fe catalysts. A catalyst with composition 25Fe75Ni was found to be the most active in CO hydrogenation for the MgAl 2 O 4 support at low metal loadings. At high metal concentrations, the maximum for the methanation activity was found for catalysts with composition 50Ni50Fe both on the MgAl 2 O 4 and Al 2 O 3 supports. This difference can be attributed to a higher reducibility of the constituting metals with increasing metal concentration. The maximum of the catalytic activity and the highest selectivity to methane were observed for the sample with 20 wt% total metal loading. It appears that it is possible to increase substantially the efficiency of Ni-based methanation catalyst by alloying with Fe.