Dry reforming of methane was investigated by non-thermal plasma coupled with different metal oxides: BaO, La2O3, ZnO, CaO, -Al2O3, MgO, γ-Al2O3, TiO2 and CeO2. The deposited power was fixed at 8W and the total gas flow at 40 mL.min-1 (75% helium as diluent). Electrical characterization showed that the CO2 and CH4 conversions were enhanced (from 5.6 to 30.6% for CH4 and from 1.9 to 16.1 % for CO2) when the permittivity was reduced from 2903 to 4.1, respectively. Methanol selectivities were favored for the oxides presenting low permittivities, indicating that reaction is favored under a low electric field, thus low density of reactive species. The effect of reaction temperature was evaluated on MgO catalyst. The increase of the temperature favored CH4 conversion, while reducing methanol selectivity. The oxide characterization by TGA revealed the re-hydroxylation of MgO at low temperature, which was correlated to the improved oxygenated compounds selectivities.

Calcium oxide, calcium hydroxide and calcium carbonate were tested for the CO2/CH4 reaction in a dielectric barrier discharge plasma reactor under humid conditions. It appeared that the presence of water in the gas stream enhanced slightly the selectivity to CO and H2 syngas on each support (2 to 5 %), contrary to the selectivities to CxHy that decreased (0.5 to 2 %). The water showed little effect on oxygenates selectivities (in the order of 0.1%) compared to dry treatment. The three materials were characterized by thermogravimetric analysis and infrared spectroscopy prior and after, dry and humid, plasma treatments. Addition of humidity in the plasma gas stream led to the formation of calcium hydroxide on the surface of CaO and enhanced the carbonation of Ca(OH)2. We showed that the carbonation of Ca(OH)2, H2O proceeded through simultaneous CO2 capture and H2O release, highlighting an oscillating behavior.