CO₂ dissociation in a packed bed DBD reactor: effect of streamer discharge

Abstract

Non-thermal plasma catalysis, as a special heterogeneous catalytic reaction, needs to consider both gas discharge and catalytic reaction. Packed bed dielectric barrier discharge (PB-DBD) is widely used in non-thermal plasma catalysis, but the exact control principle of gas discharge, especially streamer discharge, is not clear. In this study, therefore, the orderly arranged dielectric rods were packed in the discharge gap of PB-DBD, and the streamer discharge behaviors were controlled by adjusting their diameter(s), quantity(ies), location(s) and dielectric constant(s). Al2O3 and ZrO2 dielectric rods with dielectric constants of about 9 and 25 were used as packing material. Pure CO2 was used as reaction gas and discharge gas. Discharge images showed that stable and controllable streamer discharges can be formed between the dielectric rod and ground electrode. The intensity, width and length of the streamer discharge can be significantly changed by optimizing the dielectric constant, diameter, packing number and position of the dielectric rod, thereby affecting the CO2 conversion efficiency. Increasing dielectric constant and the distance between the dielectric rod and ground electrode can increase the intensity of streamer discharge, thus promoting the CO2 conversion efficiency. Compared with an empty reactor, after packing 24 ZrO2 dielectric rods with a diameter of 1 mm, the CO2 conversion and energy efficiency increased from 9.58% to 20.1% and from 1.67% to 2.89%, respectively. In short, this research has important implications for plasma catalysis. This study not only reveals the synergistic characteristics between streamer discharge and CO2 dissociation, but also provides an important idea for structural optimization of PB-DBD catalyst.

Full-wave and plasma simulations of microstrip excited, high-frequency, atmospheric pressure argon microdischarges

“…The filamentary nature of the discharge in a loosely PB-DBD and the influence of the streamers in the conversion efficiency has been recently demonstrated experimentally in Ref. [9]. In this reference, the authors show that a DBD reactor packed with simple, high-permittivity, dielectric rods (no active material) can significantly enhance the CO 2 conversion and efficiency.…”

“…The simulated geometry corresponds to the experimental study of Ref. [9] and the 12 dielectric rods case. It consists of a coaxial DBD reactor, with a ground rod electrode at its center and a highvoltage electrode wrapped around a quartz tube with dielectric permittivity of 4.5.…”

“…In the 2D approximation of the experimental domain, the axial length of the reactor which is 35 mm (note a possible error in Ref. [9] where it is noted that after the holders' positioning, the discharge length is reduced by half, so from 70 mm it should go down to 35 mm and not 3.5 mm as mentioned in the manuscript) is only used to scale the discharge current. Fig.…”

“…The ease of connection of DBD reactors in series or in parallel operation is yet another advantage of such very well-studied plasma sources in ambient conditions, towards increased conversion efficiency [8]. In addition, DBDs can be easily arranged in a co-axial configuration and packed with catalysts towards packed bed DBD (PB-DBD) reactors [9,10], leveraging plasma-catalyst synergies. Focusing on the latter, plasma catalysis remains an emerging field with large unexplored potential.…”

CO2 splitting in a micro DBD reactor with an electrode containing charge injector parts

“…Dielectric properties of the reactor material were shown to impact conversion in both tubular and planar DBD reactors [21,22]. Zhang et al found that the CO 2 conversion increased to 18% in a packed bed DBD reactor as the shorter distance between the glass particles enhanced the electric eld [23].…”