CO2 dissociation in a packed-bed plasma reactor: effects of operating conditions

An extensive study of CO2 conversion in a non-thermal, barium titanate packed-bed plasma reactor was conducted to investigate the influence of discharge power, gas flow rate and Ar dilution on the CO2 conversion, energy efficiency, identity of products and electrical characteristics of the discharge. The maximum energy efficiency in this study (0.29 mmol kJ−1, i.e. 8.3%) was achieved for a pure CO2 plasma, whereas the maximum CO2 conversion (46%) was obtained in a 20/80 CO2/Ar plasma. The results also showed that the energy efficiency was approximately constant at a given gas composition regardless of the gas flow rates. In addition, ozone (up to 100 ppm) was detected and its formation was affected by the gas flow rate. The electrical characteristics of the plasma in the packed-bed reactor were deduced using a simplified DBD equivalent model. The electrical characterisation showed that dilution with argon decreased the discharge breakdown voltage resulting in a higher mean electron energy and increased electron density enhancing conversion. The results also indicated that using a lower flow rate can increase the charge transferred per half-cycle of the applied voltage to facilitate the electron-induced CO2 dissociation, and this effect is more pronounced upon adding Ar