Adiabatic plasma-catalytic reactor configuration: Energy efficiency enhancement by plasma and thermal synergies on CO2 methanation

In the present work, CO2 methanation was performed in an adiabatic hybrid plasma-catalytic system, activated only by DBD plasma and without external heating. It was found that both plasma discharges and the reaction exothermicity were two important activation pathways. In order to discern between both phenomena, the role of the released heat was studied in two reactor configurations, pseudo-adiabatic and adiabatic approaches, revealing that conversions were sharply increased as soon as the reactor was thermally insulated. Accordingly, DBD plasma reactor isolation is an interesting approach to take advantage of the released heat in plasma-catalysis CO2 methanation and other exothermic reactions. However, a balance between the plasma power and the reacting flow must be adjusted because an excess of heat could be counterproductive for the reaction. In this sense, it was inferred that a way to control the released heat is by means of the inlet gas flow. In optimal adiabatic conditions (140,000 mL.h(-1).g(-1) and 18 kJ.mol(-1)), the energy efficiency of the process was increased up to 73%, highly upgrading the 40% efficiency at conventional pseudo-adiabatic conditions (40,000 mL.h(-1).g(-1) and 146 kJ.mol(-1)). At this efficiency level, hybrid plasma-catalysis can compete directly with thermally activated reactors for CO2 methanation with an unprecedented energy consumption of 130 kJ.mol(CH4)(-1).