Co- and Co(Ru)-Based Catalysts for Fischer-Tropsch Synthesis Prepared by High Power Ultrasound

Fischer Tropsch (FT) is an industrial process that converts syngas (H-2 + CO), using iron or cobalt based-catalysts, in hydrocarbons in the range C-1 to C-100. Cobalt-based catalysts have been used for FT for long time due to their long life-times, high CO conversion and high selectivity to heavy hydrocarbons; moreover they are characterized by low water gas shift activity, so avoiding the CO2 formation. The use of ultrasound in material chemistry is a very interesting technique to prepare novel supported materials with particular properties as nanostructured catalysts. The catalysts were prepared by a modified impregnation method. The metal precursors (cobalt and ruthenium carbonyl) were dissolved in n-decane together with the different support (SiO2, Al2O3 or TiO2) and irradiated by an US horn. After precipitation of metal nanoclusters on supports, the catalysts were dried and calcinated. All the catalyst were characterized by BET, TPR, FE-SEM, TEM, micro-Raman and XRD analysis. Tests in a pilot laboratory-scale plant have evidenced the peculiar quality of synthetic procedures and suggested new strategies for improving the efficiency of catalytic compounds. The catalysts show a low selectivity to methane and carbon dioxide and formation of higher hydrocarbons. The more interesting results are the highest CO conversion, at lower temperatures, obtained with Ru-promoted catalysts.