Fischer-Tropsch synthesis using Co and Co-Ru bifunctional nanocatalyst supported on carbon nanotube prepared via chemical reduction method

We used a chemical reduction method to synthesize the catalysts of cobalt (Co) and cobalt-ruthenium (Co-Ru) bifunctional supported on carbon nanotubes (CNTs) for Fischer-Tropsch synthesis (FTS) in a fixedbed reactor. These Co-Ru/CNTs catalysts were synthesized with various weight proportions of Ru/Co (0.1 to 0.4 wt%) with keeping a fixed amount of cobalt (10 wt%). Moreover, for comparison purpose, CNTs supported Co- and Co (Ru)-based catalysts at same loading as the above catalysts were prepared through impregnation method. We characterize the present catalysts through the various techniques such as Energy-dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET), Hydrogen-Temperature-Programmed Reduction (H-2 -TPR), Hydrogen-Temperature-Programmed Desorption (H-2-TPD) and O-2 titration. Thus using the chemical reduction method, a narrow particle size distribution was obtained so that the small cobalt particles were confined inside the CNTs. The Co-based catalyst prepared by impregnation was compared with the Co-Ru catalysts at the same loading. The results demonstrated that the use of chemical reduction method led to decrease the average Co oxide cluster size to 8.7nm so that the reduction enhanced about 24% and stabilized an earlier time at the stream. Among the prepared catalysts, the results indicated that the Co-Ru/CNTs catalysts demonstrated high catalytic activity with the highest long-chain hydrocarbons (C5+), selectivity up to 74.76%, which was higher than those we obtained by the Co-Ru/gamma-Al2O3 (61.20%), Co/CNTs (43.68%) and Co/gamma-Al2O3 (37.69%). At the same time, comparing with those catalyst synthesized by impregnation, the use of chemical reduction led to enhancement of the C-5(+) selectivity from 59.30% to 68.83% and increment in FTS rate about 11% for the Co-Ru/CNTs catalyst. (C) 2017 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.