Highly effective cobalt catalyst for wax production in Fischer–Tropsch synthesis

Fischer–Tropsch synthesis (FTS) was carried out in a fixed bed reactor with a highly effective cobalt catalyst for wax production. The procedure for reducing the inactive cobalt oxide to the active cobalt catalyst was examined by X-ray diffraction (XRD) and temperature-programmed reduction (TPR). The results showed that 300 ml/min H2 at 350 °C for 16 h was suitable for reducing the inactive Co oxides to active metallic Co sites. In the case of the powder and pellet type cobalt catalysts with a reactant (H2/CO = 2:1) flow rate of 15 gcat min L−1, catalyst deactivation occurred as a result of mass transfer limitations of the hydrocarbon and water produced on the catalyst. On the other hand, the pellet type cobalt catalyst with a reactant flow rate of 45 gcat min L−1 showed activity not only for liquid hydrocarbon (C5+) formation but also for gas product (CH4 and CO2) formation. In particular, the methane yield reached almost 20% due to heat transfer limitation in the catalyst. Considering the heat and mass transfer limitations in the cobalt catalyst, a Co-foam catalyst with an inner metallic foam frame and an outer cobalt catalyst was developed. SEM–EDS Co-mapping revealed the cobalt atoms to be distributed equally over the surface of the Co-foam catalyst. The Co-foam catalyst was highly selective toward liquid hydrocarbon production and the liquid hydrocarbon productivity at 203 °C was 52.5 ml kgcat-1 h−1, which was higher than that by the Co-pellet. In addition, the chain length probability, α, by the Co-foam catalyst was 0.923 and wax formation was especially favored.