Fischer–Tropsch synthesis on potassium-modified Fe3O4 nanoparticles

Abstract

Synthesized magnetite (Fe3O4) nanoparticles, with an average crystallite size of 8 and 22 nm, were investigated for Fischer–Tropsch synthesis reaction to clarify the effects of iron crystallite size and a potassium promoter. The larger crystallite size of Fe3O4 without the potassium promoter showed an increased CO conversion with a lower selectivity of C5+ and olefinic hydrocarbons. This was mainly attributed to the enhanced reduction degree and an abundance of active edge sites of cube-like morphology. However, a modification of Fe3O4 nanoparticles with the potassium promoter significantly changed the product distribution by increasing C5+ and olefinic hydrocarbons with much higher CO conversions. The enhanced activity on the large crystallite size of K-modified Fe3O4 was mainly attributed to an enhanced secondary reaction of olefins formed on the active iron carbide sites. The positive effect of the potassium promoter was much significant on the larger Fe3O4 nanoparticles due to an abundant presence of potassium promoter on the outer surface of the large Fe3O4 nanoparticles with a bigger inter-particular pore diameter for an easy mass transport.