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

Fe-Ru bimetallic catalysts for Fischer-Tr6psch (1717) 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 degrees 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 FIF reaction (ca. 120 h) indicating that the Fe-Ru clusters possess remarkable stability in the Fr reaction when supported on carbon nanotubes. This resistance to sintering is attributed to the metal support interaction characteristic of CNT supports. (c) 2007 Elsevier B.V. All rights reserved.