Decomposition of NO in a microwave-absorbent assisted discharge of N2 at atmospheric pressure

The decomposition of NO has been studied in a microwave-absorbent assisted discharge of N2 at atmospheric pressure. Although microwave discharge could not be maintained at high N2 pressure (>50 torr) without using microwave absorbents, the maintenance of the discharge for pressure values of 50–760 torr has been provided by using graphite, Zr, or W as microwave absorbents. The NO conversion obtained by using two short rod-form absorbents was higher than that by using one long rod-form absorbent, though the higher branching ratios of the oxides CO, CO2, ZrO2 and WO3 in the former case. It was concluded that W rods were the best microwave absorbents due to high NO conversion and high stability of discharge. The effects of the addition of O2 to the NO/N2 mixture were examined. The decomposition mechanisms of NO in the gas phase and on the hot surfaces of absorbents were discussed on the basis of optical spectroscopic analysis of discharge spectra.