Heterogeneous Methane Conversion Processes Induced by a Pulse Microwave Discharge Near a Metal Surface

The degradation of methane in the batch mode by the action of a one-atmosphere pulse microwave discharge excited in a quartz reactor partially filled by a nickel gauze was studied. The fashion of gauze layout ensuring the sustainable excitation of discharge at an average power of 60–150 W and a pulse on/off ratio of 10 was described. Measurements of a pressure rise in the system simultaneously with the chromatographic analysis of the gas mixture sampled from the reactor showed that the product buildup kinetics were determined by the discharge character: when the discharge was maintained in the form of multiple sparks throughout the gauze-filled volume, the highest degradation rate was observed and all the products detected, including benzene, accumulated linearly with respect to the amount of methane decomposed. In the case of the formation of a local discharge zone in which the gauze was heated to a yellow heat, the benzene buildup followed a nonlinear law, its formation rate increased a few times with an increase in the degree of methane conversion. Although the total methane decomposition rate was lower in this case, conversion into benzene turned out to be a few times greater than in the previous experiment. For example, no more than 10–20% of methane decomposed within a discharge time of 10 min, whereas its conversion to benzene reached 10–15%.