Monitoring the Reaction Mechanism in Model Biogas Reforming by In Situ Transient and Steady-State DRIFTS Measurements

Abstract

In this work, the reforming of model biogas was investigated on a Rh/MgAl₂ O₄ catalyst. In situ transient and steady-state diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements were used to gain insight into the reaction mechanism involved in the activation of CH₄ and CO₂ . It was found that the reaction proceeds through of an initial pathway in which methane and CO₂ are both dissociated on Rh metallic sites and additionally a bifunctional mechanism in which methane is activated on Rh sites and CO₂ is activated on the basic sites of the support surface via a formate intermediate by H-assisted CO₂ decomposition. Moreover, this plausible mechanism is able to explain why the observed apparent activation energy of CO₂ is much lower than that of CH₄ . Our results suggest that CO₂ dissociation facilitates CH₄ activation, because the oxygen-adsorbed species formed in the decomposition of CO₂ are capable of reacting with the CH_x species derived from methane decomposition.

Keywords: IR spectroscopy; biogas reforming; reaction mechanisms; rhodium; syngas.