In the present article, the effects of Fe/Cu/K catalyst particle size have been considered on the CO and CO2 hydrogenation reactions. The variation of crucial factors such as surface area and basicity, reduction, carburization and catalytic behavior of precipitated Fe/Cu/K catalysts were scrutinized. Various surface tensions hematite nanoparticles catalysts were produced by homogeneous precipitation in alcohol/water mixed solvents. The CO2-TPD results revealed that the basicity of the potassium promoted iron catalyst is increased in iron catalysts with lower particle size. Increasing in K-basic sites at surface of lower particle size catalysts is attributed to their higher surface areas. Moreover, the CO-TPR results proved that the elevation of catalyst basicity leads to increasing in dissociative adsorption of CO considerably. Shifting the oxygen removal pattern to lower temperature is the consequence of faster nucleation of FeCx crystallites on promoted surface oxides. The results also indicate that the CO2 hydrogenation reaction can occurred in two distinct direct and indirect routs via Fischer-Tropsch mechanism.

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