Biomass, biogas, and other carbon-based matters can be processed to generate syngas, which may be catalytically converted to useful hydrocarbons through Fischer-Tropsch reactions. A series of Fe/K catalysts were synthesized using high temperature treated supports with different ratios of zinc aluminate spinel to alumina and were examined by XRD, ICP, FESEM, CO2-TPD, nitrogen physisorption, and syngas conversion tests. At a total pressure of 2 MPa (approximate to 20 bar) and a CO conversion of 38.3%, the C-2, C-3 and C-4 olefin/paraffin ratios of catalyst 15%Fe/2% K2O/83%(ZnAl2O4 center dot 1Al(2)O(4)) exhibit impressive values of 9.8, 17.7 and 13.0, respectively. Meanwhile, its C-2(=)-C-4(=) HC selectivity reaches a considerable value of 52.1%, where its C-2, C-3 and C-4 olefin fractions attain ultra-high values of 90.7%, 94.7%, and 92.9%, respectively. Its methane HC selectivity is also successfully restrained to be lower than 9% even at the highest CO conversion.