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Nanosized Fe-Co catalysts were prepared by co-precipitation method and studied for the conversion of synthesis gas to light olefins.In particular,the effects of a range of preparation variables such as Co/Fe molar ratios of the precipitation solution,pH value of precipitate,temperature of precipitation,promoters and loading of optimum promoter on the structure and catalytic performance are investigated.The optimal nano catalyst for light olefins (C2-C4) production was obtained overthe catalyst with Co/Fe molar ratio of 3/1 which promoted with 2 wt％ K.The results show that the best operational conditions were GHSV =2200 h-1 (H2/CO =2/1) at 260 ℃ under atmospheric pressure.Characterization of catalysts were carried out using X-ray diffraction (XRD),thermal gravimetric analysis (TGA),differential scanning calorimetry (DSC),scanning electron microscopy (SEM),transmission electron microscopy (TEM) and N2 physisorption measurements such as BrunauerEmmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods.