On NOxproduction and volatile organic compound removal in a pulsed microwave discharge in air

The production of NO and NO 2 and the removal of 3-pentanone, as an example for volatile organic compounds (VOCs), in a pulsed microwave discharge in air, near atmospheric pressure has been studied. The influence of changing the pulse duration from 25 to 500 µs and of the pulse repetition rate from 10 to 500 Hz is reported. At a relatively high pressure of p = 800 mbar, plasma ignition is achieved by inserting BaTiO 3 pellets inside the microwave excitator. The concentrations of NO and NO 2 have been monitored by infrared tunable diode laser absorption spectroscopy. It was found that their concentrations increase monotonically with the average power injected into the plasma. Further, the efficiency of the pulsed microwave discharge for VOC oxidation, in this case of 1400 ppm of 3-pentanone in dry air, has been studied. The VOC removal efficiency has been determined using gas chromatography. The oxidative efficiency of the discharge was found to increase linearly with the pulse repetition rate as well as with the pulse duration, the power duty cycle ratio being the key parameter.