Effects of Zr and K Promoters on Precipitated Iron-Based Catalysts for Fischer–Tropsch Synthesis

The effects of Zr and K promoters on the structure, adsorption, reduction, carburization and catalytic behavior of precipitated iron-based Fischer–Tropsch synthesis (FTS) catalysts were investigated. The catalysts were characterized by N 2 physisorption, temperature-programmed reduction/desorption (TPR/TPD) and Mössbauer effect spectroscopy (MES) techniques. As revealed by N 2 physisorption, Zr and/or K promoted catalysts showed lower surface area than Fe/SiO 2 catalyst. Zr promoter inhibited the reduction and carburization because of the interaction between Fe and Zr in Fe–Zr/SiO 2 catalysts. K promoter enhanced the reduction in CO and apparently facilitated the CO adsorption, thus promoted the carburization, but it retarded the reduction in H 2 and severely suppressed the H 2 adsorption. Compared with the singly promoted catalysts, the doubly promoted catalyst had the highest FTS activity. In addition, both Zr and K promoters suppressed the formation of methane and shifted the production distribution to heavy hydrocarbons. Graphical Abstract Both Zr and K restrained the formation of methane, and increased the heavy hydrocarbons selectivity. In the FTS reaction, the doubly promoted catalyst Fe–Zr–K/SiO 2 had the highest FTS activity.