Characterization and Activity of Iron‐Manganese Catalysts for Carbon Monoxide Hydrogenation

Abstract

Studies on the structural changes and catalytic behavior of iron‐manganese catalysts for CO hydrogenation were conducted using Mossbauer spectroscopy, X‐ray diffraction, temperature programmed reduction and kinetic measurements. It was observed that the reduction of the mixed oxide catalyst precursors proceeds via the formation of Fe3‐xMnxO4,Mn3‐xFexO4 mixed spinel and Fe1‐zMn2O mixed oxide to α‐iron and MnO. After use for CO hydrogenation, catalysts are oxidized as well as carburized. The Mn3‐yFeyO4 mixed spinel and Fe1‐2MnzO mixed oxide are the most powerful phases for olefin production. The highest attainable 2–4 low carbon olefin selectivity is 41% with an 86% conversion level. Higher manganese content or lower reduction temperatures may change the carbide formed from χ‐Fe5C2 to the more unstable ϵ′‐Fe22C. Carbide formation is greatly dependent on manganese content and activation procedure used.