New insights into the effect of sodium on Fe3O4- based nanocatalysts for CO2 hydrogenation to light olefins

Abstract

A series of Fe₃O₄-based nanocatalysts with different residual sodium contents were prepared by a simple one-pot synthesis method. The effects of residual sodium on the physico-chemical properties and catalytic performance for CO₂ hydrogenation of the catalysts were investigated. The residual sodium has significant influences on the textural properties of the iron-based catalysts, and slightly hinders the reduction of the catalysts. However, it obviously promotes the surface basicity of the catalysts, which is favored for olefin production. Furthermore, increasing sodium content can greatly improve the carbonization of the iron catalysts. Compared with the sodium-free Fe₃O₄ catalysts, the sodium-containing Fe₃O₄ catalysts exhibited higher activity and produced more C₂–C₄ olefins and C₅₊ hydrocarbons. The optimized FeNa(1.18) (Na/Fe weight ratio of 1.18/100) catalyst showed excellent catalytic activity with a high olefin/paraffin ratio (6.2) and selectivity to C₂–C₄ olefins (46.6%) and C₅₊ (30.1%), as well as low CO and CH₄ production at a CO₂ conversion of 40.5%.