ausblenden:
Schlagwörter:
Fischer-Tropsch synthesis, C–C olefins, Iron catalysts, Carbon supports, Electronic junction
Zusammenfassung:
Carbon nanotubes with various surface modifications are utilized as supports for iron species and the resulting catalysts are used for the Fischer-Tropsch synthesis of C2–C4 olefins with and without the addition of Na and S promoters. A layer of nitrogen-doped carbon on the carbon nanotube surface serves as an efficient promoter independent of the presence of Na/S. It leads to significantly faster catalyst activation as compared to the tubes without such a layer resulting from an electronic junction effect at the iron-support interface. The tandem of Na/S- plus N-doped carbon promoted catalysts provide a record high iron-time-yield of up to 94∙10−5molCO gFe-1 s-1 under industrially relevant Fischer-Tropsch conditions (340 °C, 10 bar, H2/CO = 2) and slow deactivation over more than 185 h of time on stream. Furthermore, this tandem promotion leads to enhanced C2–C4 olefin and C5+ selectivity along with reduced methanization as compared to the solely Na/S-promoted catalysts.