Hydrogenation of carbon dioxide over iron carbide prepared from alkali metal promoted iron oxalate

Iron carbide was prepared by the carburization of iron oxalate doped with various alkali metals in flowing CO at 400 °C. The addition of alkali metal (Li, Na, K, Rb or Cs) to iron oxalate was found to decrease the bulk iron carbides formation. However, the amount of carbon deposited on Fe as inferred from temperature programmed hydrogenation and high-resolution transmission electron microscopic studies show an increasing trend with the increase of the basicity of alkali added. The CO₂ and H₂ conversions of all alkali doped iron catalysts were initially higher but they declined over time irrespective of alkali. The benefits of addition of alkali to iron without any structural and reduction promoters, such as copper, is found to lower the selectivity for methane, higher olefins and oxygenates formation for CO₂ hydrogenation.