Development of cobalt-based catalyst prepared from natural kaolin for production of green diesel by Fischer-Tropsch synthesis

The Fischer-Tropsch (FT) synthesis is a catalytic process that converts syngas into primarily straight-chain hydrocarbons, including alkenes and alkanes. In the heterogeneous catalysis, the roles of active metals and catalyst supports are crucial for enhancing the FT reaction and improving the production rate. In this study, the porous silicas as catalyst support were synthesized from natural kaolin clay by facile acid leaching at different HCl concentrations (2M, 5M, and 8M), abbreviated as SiO ₂ -2M, SiO ₂ -5M, and SiO ₂ -8M. The cobalt supported on the as-prepared SiO ₂ was prepared and tested in FT process for green diesel production, with comparison to the commercial supports such as Al ₂ O ₃ , ZSM-5, and SiO ₂ . At 220°C and a pressure of 20 bar, the Co/SiO ₂ -5M could exhibit an outstanding catalytic performance, with 83.23% CO conversion and a selectivity of diesel of 42.40wt%. Furthermore, the Co/SiO ₂ -5M catalyst was characterized, and it was found to have a high surface area of 122.1 m ² /g, which facilitates the adsorption of syngas reactants on the catalyst surface. The larger metal particle size in the cobalt-based catalysts also contributes to the enhanced catalytic activity in the FT synthesis by improving the reducibility of cobalt species and reducing the interaction between cobalt and the support, as revealed by H ₂ -TPR analysis. The characterization and catalytic testing results demonstrate a strong correlation between the physicochemical properties of the catalysts, such as the porosity of the silica support, cobalt metal size, and catalyst reducibility, and the FT catalytic performance of the prepared catalysts for diesel production.