Effect of Na, Cu and Ru on metal-organic framework-derived porous carbon supported iron catalyst for Fischer-Tropsch synthesis

Abstract

• Fe was highly dispersed on MIL-100(Fe) derived porous carbon with a high loading (>37 wt%). • XRD and HRTEM show particle size decrease for Na, Cu, and Ru-promoted catalysts. • Cu-promoted catalysts show a high CO conversion and a stable FT activity. • Na addition increased O/P ratio and C 5+ selectivity in product distribution. • Ru-promoted catalysts show a deactivation at high reaction temperature (340 °C). Fischer-Tropsch synthesis (FTS) is studied over Metal-organic framework (MOF) based porous carbon supported iron catalysts promoted with Na, Cu and Ru metals. The FTS results showed that all promoters can enhance CO conversion, FT product yield (FTY), and CO 2 selectivity is also increased. Among all promoters, Cu-based sample exhibits the best promoting effect in activity (FTY=0.154 mol CO g Fe −1 h − 1 ). Interestingly, the activity is about 2 times higher to that of unpromoted catalysts. Ru-contained sample exhibits the most significant influence on the light hydrocarbon production, with the C 1–4 hydrocarbon selectivity above 70%. Na-contained sample performed the highest C 5+ selectivity of 66% with a medium CO conversion of 51%. The improved FTS activity and selectivity of promoted catalysts is related to the decrease in iron particle size as confirmed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is confirmed, the small iron particles of the promoted catalyst are stabilized on the surface of carbon matrix, preventing further aggregation at high temperature, which is contributed to the improved FTS performance. Our research study showed that Na, Cu and Ru can not only affect the distribution of resulting products but also improve the activity of FTS. In short, the effect of Cu is remarkable on the MOF-derived catalyst. Similarly, the MOF-derived porous carbon catalysts confined the iron species during the reaction process, provide a clear structure-activity relationship between the promoters and the catalytic performance. Finally, this novel work can provide a new pathway for metal-organic framework-derived Fe-embedded porous carbon catalysts for Fischer-Tropsch synthesis.