Key Laboratory for Green Chemical Technology of Ministry of Education, School of Chemical Engineering & Technology, Tianjin University, Tianjin, China
The recent renewed interest in Fischer–Tropsch (FT) synthesis has largely been driven by the growing demand for clean fuels and the utilization of remote sources of natural and associated gas. Supported cobalt catalysts have been considered the preferred catalyst for the conversion of synthesis gas to long-chain parafﬁn. Typical FT synthesis catalyst supports are oxide supports like Al2O3, SiO2 and TiO2. However, the use of these supports can generate a strong metal-support interaction and lead to the formation of hardly reducible compounds. As an inert material, carbon materials display special properties like high purity, high mechanical strength, good electrical conductivity, high thermal stability and large surface area. In contrast to oxide supports, only weak interaction between the metal and carbon is evident on carbon supported cobalt catalysts, which can improve FT performance and allow better study of the intrinsic properties of the cobalt active sites.
In this work, bamboo-shaped multiwalled carbon nanotubes doped with nitrogen (NB-CNTs) was used as support for preparing the cobalt catalyst. The activity studies revealed that the acid treatment can significantly enhance the activity of the cobalt catalyst supported on NB-CNTs. Nitrogen incorporation and the surface groups formed during the acid treatment have deep influence upon carbon structure, cobalt dispersion and reducibility of the cobalt catalyst. Compared with cobalt catalysts supported on CNTs, NB-CNTs supported cobalt catalyst has an increased activity for FT synthesis though it has smaller surface area.
Keywords: Fischer-Tropsch synthesis, Cobalt catalyst, Nitrogen doped bamboo-shaped multiwalled carbon nanotubes