Promotion Effects of Nitrogen Doping into Carbon Nanotubes on Supported Iron Fischer–Tropsch Catalysts for Lower Olefins

Fischer–Tropsch synthesis (FTS) is a classical topic of great significance because of the approach of post-petroleum times. For decades, people have attempted to develop iron-based FTS catalysts with high selectivity for lower olefins. By means of the anchoring effect and the intrinsic basicity of nitrogen-doped carbon nanotubes (NCNTs), iron nanoparticles were conveniently immobilized on NCNTs without surface premodification. The so-constructed Fe/NCNTs catalyst presents superb catalytic performance in FTS with high selectivity for lower olefins of up to 46.7% as well as high activity and stability. The excellent performance is well-correlated with enhanced dissociative CO adsorption, inhibition of secondary hydrogenation of lower olefins, and promoted formation of the active phase of χ-Fe5C2. All of these merits result from participation of the nitrogen, as revealed by our experimental characterization. These results may lead to a new strategy for exploring advanced FTS catalysts with abundant N-doped carbon nanostructures.