Structural insight in TiO2 supported CoFe catalysts for Fischer-Tropsch synthesis at ambient pressure

Monometallic and bimetallic iron cobalt catalysts supported on home- made TiO2 were prepared by microwave assisted co-precipitation. The obtained samples, containing a total metal loading of 12 wt%, with different Co/Fe weight ratios, were characterized by N-2-adsorption-desorption isotherms, XRD, H-2-TPR, XPS and HRTEM techniques. The catalysts were tested in Fischer-Tropsch Synthesis reaction under atmospheric pressure using a continuous flow reactor with a gas feed of CO and H-2 in He (CO:H-2:He volume ratio of 1:1.7:2.3). The molar ratio H-2/CO was set to 1.7:1, slightly lower than the stoichiometric value of 2. The experiments were performed in the temperature range of 275-350 degrees C. Significant amount of methane and C-2-C-4 hydrocarbons formed at low temperature with all the catalysts. The selectivity to higher hydrocarbons increased with temperature. The iron containing catalysts gave rise to CO2 and also to methanol. The bimetallic catalysts exhibited the best performance in terms of CO conversion and selectivity to C-2-C-4 and high C5+ hydrocarbons. CoxFey crystallites, detected by XRD, were part of the active sites, contributing to the catalytic activity and also to the structural stability of the analysed systems.