Relationship between vibrational temperature and CO₂ methanation with plasma catalysis

CO₂ methanation technology has been attracting attention in order to realize a sustainable society. It is desirable to proceed the process at lower temperatures from the viewpoint of catalyst stability and equilibrium state, since the reaction is exothermic reaction. Plasma catalysis is a promising method which can achieve lower process temperatures. Methanation with plasma catalysis can be proceeded at 100 °C lower than conventional thermal catalysis process, which need the high temprature over 250 °C. The main factor can be generation of vibrational excited species due to collisions between the molecules and electrons. In this study, the vibrational temperature, which is an indicator of the density of generated vibrational excited molecules, was determined by optical emission spectroscopy, and the relationship between the vibrational temperature and methanation was investigated. We can estimate the vibrational temperature from the emission spectrum of the plasma. To derive the vibrational temperature, we used pgopher, which is a simulation software for optical emission intensity. As a result, the vibrational temperature increased with decreasing pressure and increasing discharge power. In addition, the CH₄ generation rate increases exponentially with vibrational temperature.