Fe-Ru small particle bimetallic catalysts supported on carbon nanotubes for use in Fischer–Tröpsch synthesis

Fe-Ru bimetallic catalysts for Fischer–Tröpsch (FT) synthesis were prepared by co-impregnation of Fe nitrate and Ru acetate salts on purified carbon nanotube (CNT) supports. The Fe-Ru/CNT catalysts were promoted with potassium and/or copper using an incipient wetness procedure in which the promoter was added at the same time as the Fe-Ru. The structures of the CNTs and sizes of the Fe-Ru metal particles (on average 2.1 nm) were determined by high-resolution TEM and HAADF-STEM. The reducibility of the catalysts was studied by temperature-programmed reduction (TPR) and the expected promoter effects (K, Cu on Fe) were observed. All the catalysts were used for the FT synthesis in a fixed-bed microreactor (275 °C, 8 bar, H2/CO = 2/1). The effect of Cu and K on CO conversion, product selectivity and FT synthesis activity was investigated. The observed behaviour of the small particles obtained in this study followed similar trends to what has been observed before for Fe promoted catalysts suggesting that support interactions do not strongly affect the promoter properties of the metals. All the catalysts were found to be stable in the FT reaction (ca. 120 h) indicating that the Fe-Ru clusters possess remarkable stability in the FT reaction when supported on carbon nanotubes. This resistance to sintering is attributed to the metal support interaction characteristic of CNT supports.

Graphical abstractFe-Ru catalysts for Fischer–Tröpsch synthesis were prepared by co-impregnation of Fe nitrate and Ru acetate on purified carbon nanotubes. The catalysts were promoted with K and Cu. HAADF-STEM evidenced metal particles with an average size of 2.1 nm. The catalysts show behaviour typical of Ru:Fe catalysts, with remarkable stability. Moreover the support interaction with the carbon does not hinder reduction and produces a catalyst which does not sinter.Figure optionsDownload full-size imageDownload as PowerPoint slide