(500a) Synergistic Effect between Plasma and Catalyst on Dry Reforming of Methane

Dry reforming of methane (DRM) was performed by plasma-catalyst hybrid method. Plasma provides plentiful active species such as electrons, ions, radicals, excited molecules. While plasma can induce dry reforming reaction (CO2+CH4→2CO+2H2) by itself, the combination of plasma and catalyst has been known to enhance the reaction. The active species generated by plasma interact with the catalyst, so that the reaction is promoted by the synergistic effect. The purpose of this study is to investigate the synergistic effect between plasma and catalyst on dry reforming of methane. In this study, two types of plasmas; a dielectric barrier discharge (DBD) and a rotating arc plasma (RAP), respectively, were combined with the catalyst reactor to confirm which type of plasma shows higher synergistic effect with the catalyst. DBD provides relatively low gas temperature (~120℃) and high electron temperature (~10eV), whereas RAP provides relatively high gas temperature (~1,500℃) and low electron temperature (~3eV). The different type of hybrid reactor was introduced according to the type of plasma. For DBD, the catalyst bed was located inside the discharge region, so that the plasma is generated on the surface of catalyst. On the other, for RAP, the catalyst bed was located at the afterglow region to avoid thermal damage by high gas temperature of RAP. The experiments were performed using each hybrid reactor with/without the catalyst to investigate the synergistic effect. All experiments were performed under atmospheric pressure without any external heat source. The total conversion and the energy efficiency were evaluated at each experiment. A total conversion is an average of conversion of CO2 and CH4 considering mole fraction. An energy efficiency is a ratio of the required energy for 100% conversion to an enthalpy of dry reforming reaction. In the case of the DBD hybrid reactor, the total conversion and the energy efficiency increased from 4.3% and 11.2% to 36.4% and 35.2% by combining with the catalyst. In the case of the RAP hybrid reactor, the total conversion and the energy efficiency increased from 62.1% and 76% to 86.8% to 99.6% by applying the catalyst. The results shows that the DBD could create the higher synergistic effect, but the absolute values of the total conversion and the energy efficiency are lower in comparison to the RAP. Such a high synergy is considered to be the result of active interaction between the reactive species and the catalyst inside the discharge region. However, it seems that the low gas temperature of DBD didn’t allow to obtain the higher conversion by overcoming thermodynamic limit because dry reforming reaction is largely endothermic. Meanwhile, the use of RAP led to the higher conversion and the higher energy efficiency regardless of the presence or absence of the catalyst, although the increasing ratio of the conversion and the energy efficiency was not high as that of the DBD. Herein, the effect of the various experimental parameters including the types of catalysts, the ratio of CO2/CH4 and the flow rate of diluting gas on the synergy will be also discussed.