Fluidized bed and slurry reactors were employed to increase the CO2 conversion and desirable product selectivity in the direct hydrogenation of CO2 to hydrocarbons over K-promoted iron catalysts, as it is beneficial for the removal of heat generated due to highly exothermic nature of the reaction. The iron catalysts (Fe-K/Al2O3 and Fe-Cu-Al-K) were characterized by BET surface area, CO2 and H-2 chemisorption, temperature-programmed reduction (TPR), X-ray diffraction (XRD) and temperature-programmed hydrogenation (TPH). The results of TPR and TPH study clearly indicated that co-precipitated Fe-Cu-Al-K catalyst has much higher reducibility and catalytic activity Of CO2 hydrogenation at low temperature than Fe-K/Al2O3. The performance of fluidized bed or slurry reactors was superior to that of fixed bed reactor for the CO2 hydrogenation over Fe-Cu-Al-K catalyst in terms of CO2 conversion and hydrocarbon productivity. Moreover, light olefins and heavy hydrocarbons were selectively synthesized in fluidized bed and slurry reactors, respectively. The optimum operation conditions and the effects of operating variables on the CO2 conversion and its product distribution in these catalytic reactors were also discussed. (c) 2006 Elsevier B.V. All rights reserved.