CO hydrogenation over bimetallic nickel-vanadium catalysts

Abstract

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. ©2000 Elsevier Science B.V. All rights reserved.