Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-IV-17DIRECT DECOMPOSITION OF NITROUS OXIDE OVER A K-DOPEDCo 3 O 4 CATALYST IN THE PRESENCE OF OXYGENC. Ohnishi, H. Yoshino, S. Imamura, S. Iwamoto and M. Inoue*Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering,Kyoto University, Katsura, Kyoto 615-8510, Japan*Tel: +81 75 383 2478; Fax: +81 75 383 2479, E-mail: inoue@scl.kyoto-u.ac.jp1. IntroductionNitrous oxide (N 2 O) has a high global warming potential, 310 times larger than that ofCO 2 and contributes to the destruction of the ozone layer in the stratosphere [1]. Withincreasing concerns about protecting our environment, the catalytic removal of nitrous oxidefrom exhaust becomes very attractive. We reported that the alkali-promoted Co 3 O 4 catalystshave high activities even in the presence of oxygen [2,3]. In the present work, reaction rateand activation energy for N 2 O decomposition in the presence of oxygen over a K-dopedCo 3 O 4 catalyst was examined.2. ExperimentalThe catalyst (K/Co = 0.02) was prepared by impregnation of CoCO 3 (Nacalai) with asolution of potassium nitrate and subsequent thermal decomposition in air at 400 °C for 4 h.Catalyst tests were carried out in a fixed-bed flow reactor. The catalyst was tabletted,pulverized into 10–22 mesh, and set in the reactor together with 15–20 mesh sea sand. Thecatalyst bed was heated to 500 °C in a helium gas flow and held at that temperature for30 min and cooled to 300 °C. Then, the reaction gas composed of 0.25–2 % N 2 O, 1–3 % O 2and He balance was introduced to the catalyst bed at W/F = 0.019 g s ml –1 (total gas flow =400 ml min –1 ). The effluent gases from the reactor were analyzed every 5 min with an on-linemicro-gas-chromatograph and data after keeping the reaction temperature for 10 min aregiven in this paper.3. Results and discussion426