High yield methane production from the hydrogenation of CO₂ using non-thermal plasma/catalysis

In this work, a dielectric barrier discharge (DBD) non-thermal plasma/catalytic reactor was used under a range of process conditions, designed to maximise the hydrogenation of CO₂ to methane. A Ni/Al₂O₃ catalyst was used in the plasma/catalysis reactor and the process parameters investigated were the effect of input plasma power, catalyst temperature, catalyst weight hourly space velocity (WHSV), and H₂/CO₂ ratio in relation to the methanation of CO₂. In addition, the effect of the catalyst active metal type (ruthenium, cobalt, and lanthanum) supported on Al₂O₃ under the optimum reaction conditions was investigated. The optimised system, using Ni/Al 2 O 3 , achieved a CO₂ conversion of 82.2 % with an energy efficiency of 22.5 g CO₂ kWh −1 , CH₄ selectivity of 90.2 % and energy efficiency of 7.4 g CH₄ kWh −1 at the plasma input power of 70 W, catalyst temperature of 280 °C, catalyst WHSV of 768 ml/g cat h, and H₂/CO₂ ratio of 4. The performance of the active catalyst metals in relation to CO₂ conversion to methane was Ru > Ni > Co > La. • CO₂ hydrogenation using non-thermal plasma/catalysis produces high yield CH₄. • Catalyst temperature and H₂/CO₂ ratio influence CH₄ yield. • Ru/Al₂O₃ and Ni/Al₂O₃ catalysts produced the highest CH₄ yields. • Maximum CO₂ conversion was 82.2 % with CH₄ selectivity of 90.2 %.