Dissociation of vibrationally excited methane on Ni catalyst Part 2. Process diagnostics by emission spectroscopy

Barrier discharge enhanced catalyst bed (BEC) reactor was developed for methane steam reforming. Synergistic effect between barrier discharge and Ni/SiO2 catalyst was clearly observed when bed temperature exceeded 400 °C, energy cost and energy efficiency achieved 134 MJ/kg H2 and 26%, respectively. This paper concentrates on two-temperature analysis of BEC reactor for better understanding of reaction mechanism. Catalyst bed temperature and plasma gas temperature were separately analyzed by emission spectroscopy of rotational band of CH(A^2(delta)). Gas temperature distribution in packed-bed reactor was also estimated by using empirical correlations, and compared to spectroscopic data. Even though plasma gas temperature reached 400–500 °C, synergistic effect was not observed when catalyst bed temperature was below 400 °C. On the other hand, thermal reforming reaction was dominated over barrier discharges if the bed temperature exceeded 700 °C. As key radical species, reactivity of vibrationally excited methane is discussed based on vibrational temperature of CH(A^2(delta)). Vibrational temperature was significantly increased in the presence of nickel catalyst, showing increased reactivity of vibrationally excited species.