The Effects of Pulse Shape on the Selectivity and Production Rate in Non-oxidative Coupling of Methane by a Micro-DBD Reactor

Abstract

The conversion of methane to ethylene has been investigated in a micro-DBD reactor with electrodes containing charge injector parts and excited with a negatively nano-second pulse voltage superimposed on a positive dc voltage. The effect of changing the characteristics of pulsed voltage such as pulse rise time (5–7 ns), total pulse width (12–14 ns), and pulse fall time (5–7 ns) on generation rate and products selectivity of the methane plasma has been studied. The kinetic model includes twenty species (electron, ions, radicals, and neutrals). The results showed that change in input pulse shape changes the generation rate and selectivity of neutral products. The rate of voltage change during pulse on-time significantly changed the instant C2H4 selectivity. With increasing the pulse rise and fall times the ethylene selectivity decreases, while the hydrogen selectivity increases. Results also showed that the electron reactions are dominant conversion channels during pulse on-time, while they had lower contributions in conversion progress during pulse off-time and the conversion process during this period is mainly governed by the radical reactions.

Nonoxidative methane coupling in a micro‐DBD with enhanced secondary electron emission

“…These pointy edges are the charge injection parts. [ 18,19 ] Additionally, the strong reduced‐electric field ($$E\unicode{x02215}{N}_{\mathrm{gas}}$$) because of the surface imperfections accelerates electrons and collides them aggressively with other species to create more reactive species and a reactive environment. It is noteworthy to mention that the pyramid electrode DBD presented in this work has been designed based on our previous computational research, [ 18,19 ] where the effects of sharp points in DBD on the physics and chemistry of the plasma have been discussed in more detail.…”

“…[15][16][17] Recently, we have shown theoretically and computationally that dielectric barrier discharges with charge injection points have further practical benefits. [18,19] Following that, in this experimental study, we explore methane conversion in an AC-driven charge injector DBD and compare the results to the usual flat electrode DBD plasma. The sharp points on the electrodes of this specific DBD produce a high-rate secondary electron emission due to the high strength of the local electric field, which might eventually boost methane activation and energy efficiency of the process.…”

Research progress on key factors of dielectric-barrier discharge plasma for wastewater treatment

“…These characteristics make the discharge not heat the gas, but directly lead to electron-induced chemical reactions, causing high threshold electron state excitation of molecules and their dissociation and ionization, and used to increase the vibration temperature, which is beneficial when the catalyst material is coupled with the plasma. In addition, they can generate high-density charged particles at lower specific deposition energy values, resulting in higher energy efficiency [22]. The above characteristics can be controlled by a variety of adjustable parameters of pulse power supply, such as pulse repetition frequency, pulse shape, pulse rise time, pulse fall time, pulse width and pulse voltage amplitude [23][24][25][26].…”

Study of plasma parameters and gas heating in the voltage range of nondischarge to full‐discharge in a methane‐fed dielectric barrier discharge

“…Also, the gas temperature must initially be fixed. All cross-section data and reaction considered here for methane plasma are the same as data used in our previous works [34,35] . Determining the C b is straightforward and it is given by:…”