The kinetic study of light alkene syntheses by CO 2 hydrogenation over Fe-Ni catalysts

Abstract

A kinetics model of CO₂ hydrogenation over iron-nickel catalysts was developed based on the detailed mechanism of alkenes re-adsorption and secondary reaction. The corresponding kinetical experiments are conducted in a continuous fixed bed reactor. The effect of reaction conditions on catalyst performance was analyzed according to the results of orthogonal experiments. The results of the experiments show that more methane in products can be obtained with iron-nickel catalysts, the trend of which is consistent with the thermodynamic analysis. However, the content of alkenes in products is equivalent with that of alkanes. This shows that the reaction is controlled by kinetics. In all, the results of the experiments also substantiate that the model can give a good representation of the reaction mechanism of CO₂ hydrogenation over iron-nickel catalysts. The parameters of this model give a better explanation for the question why the iron-nickel catalysts have a higher selectivity toward alkenes compared with other iron-based catalysts.