Effects of Different Loadings of Ru and Re on Physico-Chemical Properties and Performance of 15% Co/Al2O3 FTS Catalysts

An extensive study of Fischer-Tropsch synthesis (FTS) on alumina-supported cobalt catalysts promoted with different amounts of ruthenium and rhenium is reported. Up to 2 wt% of promoters, are added to the catalyst by coimpregnation. The catalysts are characterized by different methods including: BET physisorption, X-ray diffraction, hydrogen chemisorption, and temperature-programmed reduction. The effect of the promoters on the reducibility of the cobalt oxide species, dispersion of the cobalt, and activity and selectivity of FTS is investigated. The Re enhances the reducibility of the CoO to Co0 and small cobalt oxide particles with higher interaction with the support. However, Ruthenium was found to enhance the reducibility of Co3O4 to CoO and that of CoO to Co0 and small cobalt oxide particles with higher interaction with the support. 1wt% Ru and 1.4wt% Re increased the activity of the catalyst by a factor of 2.8 and 2.5 respectively. Both promoters enhance the selectivity of Fischer-Tropsch synthesis towards the higher molecular weight hydrocarbons. However, the effect of Re is less pronounced.