Production of C₂ −C₄ Olefins with Fischer‐Tropsch‐Synthesis: The Effect of Cu Promoter Loading on an Fe−Cu−K/SiO₂ Catalyst

In this study we focus on the iron-based catalyst to produce C2−C4 olefin hydrocarbons via the high-temperature Fischer-Tropsch synthesis. Promoters have a significant impact on catalyst stability, activity, and product selectivity. Therefore, we investigated the effect of the Cu promoter in an Fe−Cu−K/SiO2 catalyst. We compared the catalyst without Cu and 1, 2, 3, 4, and 5 wt % Cu loadings. The overall catalyst activity increased from 0 to 3 wt % Cu loading and started to decrease at 4 and 5 wt % Cu loadings. Although overall catalyst activity had an optimum with 3 and 4 wt % Cu loading, the Cu loading had a negligible effect on product selectivity. However, when compared to a non-Cu promoted catalyst, the Cu addition increased the selectivity towards olefinic C2−C4 hydrocarbons. The Fischer-Tropsch experiments were performed in a tubular reactor system at 300 °C, 21 bar and H2 : CO=2 at different feed volume flows, with hydrogen activation. According to the performed temperature-programmed dynamic chemisorption analysis, the Cu promoter assisted the iron reduction, and the lower overall activity to 0–2 wt % Cu loading might relate to insufficient dissociated H surface species, rather than the availability of C from dissociated CO.