Cobalt supported on silica–alumina nanocomposite for use in CO2 methanation process: effects of Si/Al molar ratio and Co loading on catalytic activity

Abstract

Metal-based nanocatalysts have emerged as important materials to turn carbon dioxide (CO2) 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 CO2 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 CO2 conversion of 78.5% and CH4 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 (H2/CO2 molar ratio), gas hourly space velocity, and catalyst stability. By increasing the feed ratio to 4, the CO2 conversion and CH4 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.