Fischer-Tropsch synthesis over cobalt-containing unsupported catalysts in slurry reactor. Effect of the metallic Co particle size on the catalyst selectivity

Catalytic properties of a variety of Co-MgO and Co-ZnO unsupported catalysts were investigated in Fischer-Tropsch synthesis in a tetradecane-filled slurry reactor at atmospheric pressure and a CO/H-2 ratio 1:2. An effect of size of dispersed metallic cobalt on the selectivity of catalyst in the FT synthesis (the a value of the Anderson-Schulz-Flory distribution) has been found: the smaller the particle, the higher the a value. A possibility to control the a value in the range of 0.6-0.8 for both saturated and unsaturated hydrocarbons has been shown. An explanation of the above data can be based on an assumption that hydrogen atoms dissolved in octahedral interstitial positions of the metallic cobalt particle lattice are responsible for hydrogenation of the FT hydrocarbon intermediates into the hydrocarbons.