Dry Reforming of Methane in a Gliding Arc Plasmatron: Towards a Better Understanding of the Plasma Chemistry.

Dry reforming of methane (DRM) in a gliding arc plasmatron is studied for different CH fractions in the mixture. The CO and CH conversions reach their highest values of approximately 18 and 10 %, respectively, at 25 % CH in the gas mixture, corresponding to an overall energy cost of 10 kJ L (or 2.5 eV per molecule) and an energy efficiency of 66 %. CO and H are the major products, with the formation of smaller fractions of C H (x=2, 4, or 6) compounds and H O. A chemical kinetics model is used to investigate the underlying chemical processes. The calculated CO and CH conversion and the energy efficiency are in good agreement with the experimental data. The model calculations reveal that the reaction of CO (mainly at vibrationally excited levels) with H radicals is mainly responsible for the CO conversion, especially at higher CH fractions in the mixture, which explains why the CO conversion increases with increasing CH fraction. The main process responsible for CH conversion is the reaction with OH radicals. The excellent energy efficiency can be explained by the non-equilibrium character of the plasma, in which the electrons mainly activate the gas molecules, and by the important role of the vibrational kinetics of CO . The results demonstrate that a gliding arc plasmatron is very promising for DRM.