Bimetallic Ni–Fe total-methanation catalyst for the production of substitute natural gas under high pressure

The bimetallic Ni–Fe catalysts used in CO total-methanation reaction were prepared by the impregnation method on γ-Al2O3 support for the production of substitute natural gas (SNG). The catalysts were characterized by N2 physisorption measurements, field-emission scanning electron microscopy (FE-SEM), and H2 temperature-programmed reduction (H2-TPR). The methanation performance under the industrial total-methanation conditions (0.1–3.0 MPa, H2/CO = 3.0–3.1) was studied in detail using Ni–Fe/γ-Al2O3 as a heterogeneous catalyst. The results showed that the addition of Fe to the catalyst can effectively improve the catalytic activity of Ni/γ-Al2O3, while the high activity of bimetallic Ni–Fe catalyst was attributed to the quality of Ni–Fe alloy in the catalyst in terms of the experimental results of H2-TPR. The sample with appropriate Ni/Fe molar ratio of about 3 exhibited the highest CO conversion (near 100% at 225–550 °C) and the highest CH4 selectivity (over 99% at 300–450 °C) under the reaction pressure of 3.0 MPa. Furthermore, based on the systematic study of catalyst components, MgO in the catalyst can increase the reduction temperature of nickel oxide on the support. The silicon species as an impurity in the support play a negative role in the catalytic activity, especially for the CH4 selectivity.