Effect of Silica Encapsulation on Cobalt-Based Catalysts for Fischer–Tropsch Synthesis under Different Reaction Conditions
Juliana L. Smarzaro, Maria A. S. Baldanza, António J. Almeida, Alexander Caytuero, Vera Maria Martins Salim, Fábio B. Passos, Victor Teixeira da Silva
Abstract
Cobalt nanoparticles prepared by a solvothermal treatment were encapsulated in silica with different shell thicknesses by the Stöber method. The application of these materials as catalysts in Fischer–Tropsch synthesis was investigated under different reaction conditions, and their behaviors were compared to a silica-supported cobalt catalyst. The protective effect displayed by the silica shell avoided sintering of the active phase and influenced the reaction selectivity and activity in comparison with the supported catalyst. The silica shell thickness also played an important role in catalytic performance. A decrease in shell thickness caused an enhancement in selectivity toward C19–C24 hydrocarbons, indicating the occurrence of a confinement effect by silica pores over hydrocarbon growth. Furthermore, a high production of methane might be related to the occurrence of CO diffusion limitations due to the thicker silica shell. The activity and selectivity remained similar at different reaction temperatures. However, the use of a lower temperature caused an increase in stability.