Cobalt supported on silica–alumina nanocomposite for use in CO 2 methanation process: effects of Si/Al molar ratio and Co loading on catalytic activity

Metal-based nanocatalysts have emerged as important materials to turn carbon dioxide (CO 2 ) into hydrocarbon fuels in order to deal with global climate issues and solve growing energy needs. Here, mesoporous silica–alumina (SA) nanocomposites are synthesized by a facile sol–gel method using citric acid monohydrate with different Si/Al molar ratios ( X = 0.1–10), followed by impregnating cobalt on them. The resulting Co/SA-X catalysts are characterized by various techniques and utilized in the production of substitute natural gas through CO 2 methanation as a renewable energy storage system. The porous structure of the supports with suitable particle size distribution and superior reduction behavior provides the catalysts with high stability. The Si/Al molar ratio and Co loading are optimized at 0.5 and 15 wt%, respectively, achieving a high CO 2 conversion of 78.5% and CH 4 selectivity of 89%. Alternatively, different amounts of cobalt are loaded on the selected support (SA-0.5), while also investigating various parameters such as the feed ratio (H 2 /CO 2 molar ratio), gas hourly space velocity, and catalyst stability. By increasing the feed ratio to 4, the CO 2 conversion and CH 4 selectivity are enhanced to 83 and 90%, respectively, indicating the excellent performance of the SA-supported nanocatalysts to address both the environmental concerns and the needs for sustainable energy.