AbstractIn this study the effect of (0.1 %Ru, 0–10 % Zr) and (0.1 %Ru, 0–10 % Ce) promoters on dispersion, strong metal-support interaction and reduction behavior of cobalt-supported alumina catalyst in the Fischer-Tropsch synthesis was investigated. The synthesized catalysts were characterized by BET, XRD, ICP, TPR, XPS, and TEM techniques. The results show that addition of Ce to the catalyst leads to the shift of the TPR peaks to lower temperatures which expected that shows higher activity due to higher reducibility, but surprisingly due to SMSI effect results in the lower catalyst activity compared with the unpromoted catalyst. Also, there was a synergistic effect between Ce and Ru in the reduction behavior of Ru-Ce promoted catalyst. The other notable finding of this study was the improvement in the catalyst reducibility in the presence of Zr compared with the unpromoted one that equivalently means the higher catalyst activity. Comparison of the Zr-promoted with the Ce-promoted catalysts show that the former have higher catalyst activity than the latter due to higher acidity and SMSI effect in the presence of the Zr promoter. The C5selectivity of the 0.1Ru10Zr/15Co and 3Ce/15Co catalysts at low pressure have shown more than 50 % improvement compared to the unpromoted one. Based on the activity at atmospheric pressure; the unpromoted, 0.1Ru/15Co, 0.1Ru3Ce/15Co and 0.1Ru10Zr/15Co catalysts were selected for high pressure condition tests, in which the 0.1Ru10Zr/15Co catalyst shows the highest catalyst activity and heavier hydrocarbon selectivity.