Improving CO2 conversion in warm plasma by suppressing CO-O back-reactions through particle-assisted rapid cooling and catalytic O-O recombination

Atmospheric pressure warm plasmas can achieve high CO 2 conversion, but their performance is strongly limited by CO reoxidation during cooling of the plasma effluent. We investigate a new quenching strategy that combines particle-assisted rapid cooling with catalytic promotion of O atom recombination to O 2 using suspended Al 2 O 3 particles and/or SO 2 -based gas-phase catalysis. We developed a chemical kinetic model to evaluate the effects of cooling rate, particle loading and catalyst properties on the quenching efficiency of a CO 2 /CO/O 2 /O mixture at 3500 K, typical for a warm plasma effluent. The results show that conventional quenching of pure CO 2 plasma effluents requires cooling rates of 10 8 –10 9 K/s, as well as cooling to near-ambient temperatures, to reach energy efficiencies above 40%, highlighting the extreme difficulty of attaining such conditions experimentally. In contrast, our calculations reveal that particle-assisted catalytic quenching increases the energy efficiency from 29% to 47%, and the conversion from 49% to 79%, hence close to the thermodynamic limits of 48% and 82%, respectively, even when cooling down to temperatures around 1500 K instead of 300 K. Similarly, SO 2 addition to a quenching gas increases the energy efficiency and conversion to 43% and 72%. These improvements result from enhanced O-O recombination, which suppresses CO-O back-reactions and enables efficient quenching, even at relatively high temperatures around 1500 K. Our proposed approach therefore offers a promising pathway towards efficient quenching of warm CO 2 plasma, with simultaneous opportunities for effective heat recovery.