Dynamic adsorption studies on Ni-based methanation catalysts using the continuous flow method

Abstract

To elucidate the correlation between the adsorptive and reactive properties of Ni-based composite catalysts, the dynamic adsorption characteristics of gaseous reactants on the catalysts in both the methanation of carbon oxides and the hydrogenation of carbon were investigated by the continuous flow method.

The combining of La₂O₃ with Ni increased the adsorptions of both hydrogen and carbon oxides, especially in carbon dioxide, while the combining of Ru with Ni or Ni + La₂O₃ markedly increased the H₂ adsorption at a given hydrogen partial pressure. The former can be interpreted as an increase of the Ni dispersion by La₂O₃ and its basicity and the latter supports the hydrogen spillover mechanism. Fast and irreversible adsorption decreased when the temperatures for both catalysts of the silica support and active carbon support were raised, but above 200°C slow and irreversible adsorption increased for the catalyst with the active carbon support. It is suggested that the former corresponds to adsorption on a metallic surface and the latter is attributed to activated adsorption on an active carbon through metallic parts as the transport agents.

A linear relationship, in logarithmic coordinates, was found between the relative reaction rates and the products of the relative uptakes of reactants; the significance of this linear relationship is discussed.