Photochemical Removal of N2O in N2 or Air Using 172 nm Excimer Lamps

N2O removal was investigated in N2 or air using 172 nm Xe2 excimer lamps (50 or 300 mW/cm2) without using any expensive catalysts. The residual amount of N2O and the formation ratios of products were measured as functions of photoirradiation time, N2O concentration, and O2 concentration. N2O (100 ppm) was completely converted to N2 and O2 without NOx emission in N2 at atmospheric pressure after 30 min photoirradiation using a high-power Xe2 excimer lamp (300 mW/cm2). 76% of N2O (100 ppm) was also converted to N2, O2, and HNO3 in air (20% O2) after 30 min photoirradiation using the high-power lamp. We concluded that N2O is dominantly decomposed by 172 nm photolysis in N2 and by the O(1D) + N2O reaction in air, where O(1D) atoms dominantly arise from the 172 nm photolysis of O2. The conversion of N2O in air increased more than twofold by decreasing the total pressure from atmospheric pressure to 20 kPa by suppressing the collisional quenching of O(1D) by N2 and O2 buffer gases. In a flow experiment, the conversion of N2O in N2 was only 6–18% in the total flow rate range of 0.1–1 L/min owing to the short residence time of N2O in the photolysis chamber.