Five different Fe-Cu/SiO2 catalysts were prepared by a combination of co-precipitation and wet impregnation technique at different K-loading ranging from 0 to 5 wt.% for the conversion of syngas to liquid fuel. The physiochemical characterization of these catalysts was performed by using N-2 adsorption, X-ray diffraction (XRD), H-2-TPR, NH3-TPD, TEM, Inductive Couple Plasma Mass Spectroscopy (ICP-MS), and SEM-EDX to study the effect of potassium on the textural properties, structural change, reduction behavior, acidity and morphological change to the above K-loading catalysts. The effect of addition of potassium promoter was studied for CO-Hydrogenation in a fixed bed reactor simultaneously with the effect of promoter on the CO-conversion, selectivity and deactivation. The maximum catalytic activity was obtained from 1% K-loading and the catalytic activity decreased thereafter. The activity for water-gas shift (WGS) also enhanced with increasing K loading. The results revealed that increasing K loading decreases gaseous hydrocarbon formation and shifts selectivity to higher molecular weight hydrocarbons. Incorporation of potassium suppresses the hydrogenation activity of the Fe-Cu/SiO2 catalyst, leading to higher olefin yield in the products. (C) 2013 Elsevier Ltd. All rights reserved.