Effect of the precursor on the activity of high temperature water gas shift catalysts

Abstract

The conventional catalysts used for high temperature water gas shift reaction are composed of Fe3O4–Cr2O3–CuO. The synthesis method to prepare them affects to their properties and catalytic activity. Moreover, the raw material used during the synthesis has also influence on their performance. In this work, the effect of the precursor on the activity of magnetite-based catalysts prepared by oxidation–precipitation method was studied. Ferrous sulfate and chloride were the precursors selected and the addition of Cu and Co as activity promoters was also studied. The materials prepared with sulfate showed larger crystallite sizes and lower specific surface areas but they were more active and selective than those obtained from chloride. This could be due to a decrease of the surface basicity that improves the reducibility and affects to the hydrogen adsorption and CO chemisorption. Addition of Cu or Co increased the CO conversion for the materials prepared with chloride but not for those prepared with sulfate. In the former case, Cu improved the reducibility of the samples. Cobalt was incorporated into magnetite lattice improving the covalency of Fe2+ ↔ Fe3+ redox couple of magnetite.