Plasma-assisted partial oxidation of methane at low temperatures: numerical analysis of gas-phase chemical mechanism

Methane partial oxidation was investigated using a plasma microreactor. The experiments were performed at 5 and 300 degrees C. Microreactor configuration allows an efficient evacuation of the heat generated by methane partial oxidation and dielectric barrier discharges, allowing at the same time a better temperature control. At 5 degrees C, liquid condensation of low vapour pressure compounds, such as formaldehyde and methanol, occurs. H-1-NMR analysis allowed us to demonstrate significant CH3OOH formation during plasma-assisted partial oxidation of methane. Conversion and product selectivity were discussed for both temperatures. In the second part of this work, a numerical simulation was performed and a gas-phase chemical mechanism was proposed and discussed. From the comparison between the experimental results and the simulation it was found that CH3OO center dot formation has a determinant role in oxygenated compound production, since its fast formation disfavoured radical recombination. At 5 degrees C the oxidation leads mainly towards oxygenated compound formation, and plasma dissociation was the major phenomenon responsible for CH4 conversion. At 300 degrees C, higher CH4 conversion resulted from oxidative reactions induced by center dot OH radicals with a chemistry predominantly oxidative, producing CO, H-2, CO2 and H2O.