Carbon Dioxide Decomposition With Dielectric Barrier Discharge Microplasma

Carbon dioxide（CO₂） is the major contributor to the greenhouse effect, so its treatment is of great significance. However, it is difficult for CO₂ to be activated efficiently via conventional catalytic and thermal reaction processes because CO 2 molecule is thermodynamically stable. Dielectric barrier discharge（DBD） microplasma combines the advantages of non-thermal plasma with those of microreactors, it has the characteristics of high stability, high density, portable and low-energy. It provides an effective way to activate and degrade CO₂. In this work, DBD microplasma reactor was used to degrade CO₂ to carbon monoxide（CO） at a normal atmosphere and room temperature. The effects of reactor configuration and process parameters on CO₂ conversion were discussed.In the process of pure CO₂ conversion by DBD microplasma, no carbon deposition was found. The results indicated that a higher conversion of CO₂ could be realized with a lower feed flow rate and a limited higher input power. When the discharge gap was 0.6 mm, 18.0 k Hz may approach the resonant frequency point, which was the best discharge frequency for CO₂ conversion.When Ar was used as adding gas, the conversion of CO₂ achieved high value in a certain range of frequency. Compared with the pure CO₂ conversion, the adding of H₂/Ar was positive for the process, and the effect of H₂ on the conversion of CO₂ was more remarkable. However, the appearance of N₂ was negative for the CO₂ conversion. With the input power increasing, the conversion of CO₂ with H₂ as adding gas increased rapidly at lower input power then decreased at higher input power, the conversion of CO₂ with N₂ as adding gas kept increasing when the input power was higher than 15.0 W.When the DBD microplasma reactor was packed with dielectric materials（including quartz wool, quartz sand, γ-Al₂O₃, MgO, and CaO）, the electric field intensity was enhanced, and the average electron energy increased. Meanwhile, chemical reactions shifted from gas-phase reactions to heterogeneous reactions plus gas-phase reactions. The result indicated that the introduction of dielectric materials was positive for CO₂ conversion. Particle size, dielectric constant, particle morphology, and acid-base properties of the dielectric materials all affected the CO₂ decomposition process. The conversion of CO₂ reached the highest value of 41.9 % in a CaO-packed reactor with a feed flow rate of 20.0 mL/min, input power of 25.0 W, frequency of 18.0 k Hz, discharge gap of 0.6mm, external electrode length of 80.0 mm, and particle size of 0.18-0.25 mm.