Reaction mechanism explorations on non-thermal plasma reforming of CO2-CH4 by combining kinetics modeling and emission spectroscopy measurements.

[Display omitted] • Comprehensive mechanism explorations on plasma-based dry reforming by detailed kinetic modeling and in-situ OES measurements. • A CH 4 conversion as high as 44.76 % was achieved without catalyst at 300 °C. • Plasma kinetic model with incorporation of dynamic electron filed and thermal effects. • The formation of C 2 hydrocarbons followed a pathway of CH 4 ↔ CH 3 /CH → C 2 H 6 ↔ C 2 H 5 ↔ C 2 H 4 → C 2 H 2. Plasma-based dry reforming in an atmospheric dielectric barrier discharge (DBD) reactor has been thoroughly studied by combination of experiments and detailed kinetics simulation. With the assistances of in-situ optical emission spectroscopy (OES) measurements and reaction pathway analysis based on plasma kinetic simulation considering non-constant electric field and thermal effects, this study provided deep insights into the reaction mechanism of plasma-based dry reforming under varied feeding gas composition, gas residence time and operation temperature. A CH 4 conversion as high as 44.76 % could be achieved without catalyst at 300 °C, with an SEI of 78 J/cm3 and feeding CH 4 ratio of 50 %. Increase of feeding CH 4 proportions were found to enhance the generation of C 2 and C 3 hydrocarbons. Consistently, the OES analysis showed that the relative intensities of spectra bands induced by deexcitation of CH, CO, and C 2 also increased monotonically. With the same increment in SEI, increasing gas residence time led to larger promotions in CH 4 and CO 2 conversion, as being compared to increase of input power. The reason could be explained as that CH 4 and CO 2 molecules experienced more successive micro-discharges with a longer gas residence time, so more energy would be devoted into CH 4 /CO 2 conversion, whereas more energy was dissipated into heat as rudely increased the discharge power due to the limit of reaction time. CO 2 conversion continuously decreased with increasing gas temperature, owing to the recombination of CO and O enhanced at higher gas temperatures. Reaction pathway analysis showed that CH 4 conversion was mainly induced by electronic dissociation and ionization at the discharge stage, while CO 2 was mainly converted by recombination reaction CO 2 + CH 2 → CH 2 O + CO and also electron collision vibrational reaction e + CO 2 → e + CO 2 (v n). The formation of C 2 hydrocarbon products was supposed to follow the path of CH 4 ↔ CH 3 /CH → C 2 H 6 ↔ C 2 H 5 ↔ C 2 H 4 → C 2 H 2. [ABSTRACT FROM AUTHOR]