Fe-based Fischer–Tropsch synthesis catalysts containing carbide-forming transition metal promoters

Abstract

Surprisingly, although the impacts of promoters such as K and Cu on the activity of Fe catalysts have been studied extensively, the effects of many other potential promoters for Fe catalysts similar to the commercial Ruhrchemie catalyst have not been significantly investigated or compared directly in a comprehensive study reported in the literature. In this study, the impact of adding various different transition metals (Cr, Mn, Mo, Ta, V, W, and Zr) on the catalytic properties of precipitated bulk Fe-based catalysts was investigated using the same preparation method and reaction conditions. All of the Fe catalysts prepared in this study exhibited high BET surface areas with excellent metal distributions. The addition of the third metal in addition of Fe and Cu (all except W) increased the activity of the Fe catalyst for CO hydrogenation and for the water–gas shift (WGS) reaction, with Cr-, Mn- and Zr-promoted Fe-based catalysts exhibiting the highest catalytic activities. However, hydrocarbon selectivity was not affected by the presence or type of added third metal. The enhanced activity of the Fe catalyst by third metal promotion (with the exception of Mn and Zr) appears to have been primarily due to a higher degree of Fe dispersion on the surface of catalyst whereas the higher activities observed for Mn- and Zr-promoted Fe catalysts were especially due to higher TOF chem values based on CO chemisorption.