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

N2O removal was investigated in N-2 or air using 172 nm Xe-2 excimer lamps (50 or 300 mW/cm(2)) 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 O-2 concentration. N2O (100 ppm) was completely converted to N-2 and O-2 without NOx emission in N-2 at atmospheric pressure after 30 min photoirradiation using a high-power Xe-2 excimer lamp (300 mW/cm(2)). 76% of N2O (100 ppm) was also converted to N-2, O-2, and HNO(0)3 in air (20% O-2) after 30 min photoirradiation using the high-power lamp. We concluded that N2O is dominantly decomposed by 172 nm photolysis in N-2 and by the O(D-1) + N2O reaction in air, where O(D-1) atoms dominantly arise from the 172 nm photolysis Of O-2. 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(D-1) by N-2 and O-2 buffer gases. In a flow experiment, the conversion of N2O in N-2 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. (c) 2009 The Japan Society of Applied Physics