Plasma-catalytic methane conversion with carbon dioxide in dielectric barrier discharges

The hybrid plasma-catalytic system was tested for the mixture of methane and CO2 conversion at the pressure of 1.2 bar with the use of a dielectric barrier discharge (DBD) reactor powered at the frequency of 5.7–6 kHz. Three kinds of catalytic packing were examined: alumina ceramic carrier (Al2O3) and two catalysts, i.e. Ag/Al2O3 and Pd/Al2O3. The effects of temperature (120–290 °C), [CO2]:[CH4] molar ratio in the inlet gas mixtures (CH4 + CO2 + Ar), gas flow rate, and specific energy on the conversion were studied. Hydrogen, carbon oxide, hydrocarbons (ethane, ethylene + acetylene fraction, propane, propylene, n-butane, and i-butane), and alcohols (methanol and ethanol) were identified in the outlet gas. Among the organic gaseous products, ethane was dominant over the entire parameter range under examination. Non-volatile products (carbon, macromolecular substances) formed a visible deposit on the quartz dielectric barrier and metal electrode surfaces. With the Pd/Al2O3 catalyst, the overall methane conversion was 30–50% and the methane conversion to C2–C4 hydrocarbons reached 22%.