Dry reforming of methane in a temperature-controlled dielectric barrier discharge reactor: disclosure of reactant effect

Abstract

Plasma-assisted dry reforming of methane has attracted much research attention because this process simultaneously utilizes greenhouse, methane and carbon dioxide, to produce hydrogen-rich syngas at a relative low temperature. Although it is generally recognized that the gas composition of reactant has great effect on the methane conversion and products distribution, systematic studies that clarify the roles that electron-induced chemistry and thermochemistry play are needed for a full understanding of reactant effect. Here, we compared the reforming performance by varying the ratio of CO2/CH4 or O2/CH4 at the similar reduced field intensity (E/N) in a temperature-controlled dielectric barrier discharge reactor to elaborate the role of electron-induced chemistry and thermo-chemistry in the dry reforming process. By conducting optical emission spectrum measurement, the enrichment of O atoms was observed at the increased CO2/CH4 or O2/CH4 ratios. At T = 293 K, methane conversion was only dependent on the electron-induced chemistry regardless of the specific reactant gas composition. At a relative high temperature condition, however, thermochemistry could become pronounce when sufficient O atoms were added into the dry reforming process. In contrast, the chemical pathways to the products were overall controlled by the thermochemistry at the tested background temperatures. Due to the conversion of carbon-based products into the carbon dioxide, the conversion of carbon dioxide was influenced by the thermochemistry when the concentration of O atoms was high. Our findings may improve the understanding of reactant effect and the designs of plasma-reformer.

Recent Developments in Dielectric Barrier Discharge Plasma-Assisted Catalytic Dry Reforming of Methane over Ni-Based Catalysts

“…DBD plasma is a means to effectively activate molecules. First of all, it can often activate high-stability methane molecules under milder conditions, usually at a pressure of 104-106 Pa and a frequency of 50 Hz [42]. Secondly, the simple design and easy-tooperate characteristics of the DBD reactor facilitates the miniaturization or expansion with high portability [39].…”

From thermal catalysis to plasma catalysis: a review of surface processes and their characterizations

“…These applications used a number of different plasma sources [9,[25][26][27][28][29]. Plasma sources employed for plasma catalytic reactors include dielectric-barrier discharge (DBD) plasma sources [30][31][32][33][34][35][36][37][38][39][40], gliding arc plasma sources [41,42], plasma jet sources [25,[43][44][45], glow [46][47][48] and corona [49] discharges, and others [50,51]. Additionally, catalyst properties vary widely, e.g.…”

Ammonia cracking for hydrogen production using a microwave argon plasma jet

“…Conversions of NH 3 for various combinations of P MW and Q t for the controlled C NH3,i = 0.5% v/v (figure 5(a)) could be correlated successfully with the energy density, as illustrated in figure 6. Like other plasma-assisted chemical processes [18,46], the energy density (input energy per unit volume of the treated gas) accurately characterized the NH 3 cracking process in the MWPJ. The conversion trend in figure 6 can be divided into two regimes: a linear regime and a full conversion regime.…”

“…On the other hand, because of the highly energetic electrons in nonthermal plasmas (e.g. T e ∼10 eV for dielectric barrier discharges, DBDs, or nanosecond repeatedly pulsed discharges, NRPDs), the electron-induced reactions play a significant role in producing chemically active species (electrons, radicals, and metastable excited states) [15][16][17], although a final product composition is governed mostly by thermal reactions for a given T g [18,19]. For this reason, nonthermal plasmas were widely used in plasma chemical kinetic studies with a particular focus on electron-induced reactions [15][16][17][18][19][20][21][22].…”

“…T e ∼10 eV for dielectric barrier discharges, DBDs, or nanosecond repeatedly pulsed discharges, NRPDs), the electron-induced reactions play a significant role in producing chemically active species (electrons, radicals, and metastable excited states) [15][16][17], although a final product composition is governed mostly by thermal reactions for a given T g [18,19]. For this reason, nonthermal plasmas were widely used in plasma chemical kinetic studies with a particular focus on electron-induced reactions [15][16][17][18][19][20][21][22]. Recently, Bang et al [23] published the first comprehensive plasmachemical kinetic mechanism for ammonia cracking based on DBD, which included both electron-induced and conventional thermal reactions.…”