Fischer-Tropsch Synthesis on Co/SBA-15 Catalyst: Characterization and Oligomerization Modeling

In this study, we investigated the oligomerization mechanism of the Fischer-Tropsch synthesis catalyzed by a cobalt-based catalyst supported by SBA-15. The Co/SBA-15 catalyst contained 20% w/w of cobalt. It was prepared by the wet impregnation method and characterized by X-ray diffraction (XRD), N2 adsorption-desorption, temperature-programmed reduction (TPR), and scanning electron microscopy coupled to X-ray energy dispersion spectroscopy (SEM-EDS). The FT synthesis was conducted in a slurry bed reactor operating at 240–270°C, 2.0–3.0 MPa, and 1:1–2:1 H2:CO ratio (mol:mol). An oligomerization model, based on alkyl and alkenyl mechanisms for hydrocarbon chain propagation, was used for product distribution. Impregnation with cobalt and calcination did not alter the structure of SBA-15. Cobalt oxides, including Co2O3 and Co3O4, were the active phases of the reaction. Adding cobalt to the support lowered the specific surface area and the pore volume of the support but did not change the structure of SBA-15. Fischer-Tropsch synthesis and C5+ hydrocarbon selectivity increased at a low H2:CO ratio (1.0) and low temperatures (240–255°C). The content of branched-chain paraffin and olefins increased with a decrease in the H2:CO ratio and temperature. The parameters of the model were estimated, and the assumption of a dual mechanism was satisfied.