USE OF THE POSTDISCHARGE OF AN AIR OR NITROGEN MICROWAVE PLASMA FOR METHANE VALORIZATION

Valorization of methane is obtained by means of the reaction with a plasma. The plasma is produced in a quartz tube (30 mm in diameter) crossing a wave guide. The energy is supplied by a generator (Thomson CSF, 2 450 MHz, 15 to 1 500 W). Directional couplers followed by an attenuator and thermistor detectors enable forward PI(i) and reflected PI(r) power to be measured. Methane is introduced in the post-discharge zone through five tubes symmetrically arranged around the reactor. Methane consumption alpha, selectivity S(X) and yield R(X) are measured as a function of the following parameters : beta methane/air ratio, F gaz flow, d distance where methane is introduced in the plasma, P pressure, PI microwave power absorbed by air or nitrogen. It appears that acetylene is the major hydrocarbon obtained. The corresponding selectivity is increased when PI and P are increased or when d and F are decreased. The optimum value of beta is 4/5. If the best experimental conditions are selected, selectivity of total C2 reaches 44% with a conversion ratio of 80%. By decreasing methane/air ratio, carbon monoxide yield is increased. The ratio acetylene/ethylene can by varied without changing the conversion ratio, by introducing a catalyst in the post reaction zone.