CO hydrogenation over bimetallic nickel–vanadium catalysts Original Research Article

A series of γ-Al2O3 supported Ni, Ni–V, Ni–V–K catalysts were prepared by impregnation or sequential impregnation to study the effects of V and K promotion on structural properties of Ni catalysts and their catalytic performance in CO hydrogenation. The Ni content of the samples was fixed at 5 wt.% while the V content was varied between 0.5 and 2 wt.%. Finally, 0.5 wt.% K was added to 5 wt.% Ni–1 wt.% V/Al2O3 for obtaining enhanced olefin selectivities. Experimental results indicate that total activity and C2–C4 hydrocarbons production are increased by V addition up to 1 wt.% while olefin selectivities show a decreasing trend in the same range. The addition of K decreases the total hydrocarbons production of the catalyst, more specifically the production of paraffinic hydrocarbons and CO2, resulting in an increase in the ratio of C2–C3 olefins to paraffins. The maximum selectivity for lower hydrocarbons is obtained at 548 K with the 5 wt.% Ni–1 wt.% V–0.5 wt.% K catalyst. Regression analysis of intrinsic kinetic data obtained in the initial rate region on the Ni–V–K catalyst shows that CO consumption kinetics is best correlated by the surface carbide mechanism with irreversible dissociative adsorption of hydrogen as the rate-limiting step.