Preparation of Manganese Oxide Catalysts for Decomposition of Ozone by Alkali and Ozone Precipitation Methods

To clarify the effect of the preparation conditions of Mn2O3 catalysts on their activity for the decomposition of ozone, Mn2O3 catalysts were prepared from manganese salts [Mn (NO3) 2, MnCl2, MnSO4] using alkali (NaOH, KOH, Na2CO3, NH3) and ozone (O3-O2 mixed gas) under different conditions. Catalytic activities (conversion of O3 to O2) of the prepared samples were measured using a fixed-bed flow type reactor.The inlet gas was mainly composed of O3 (235 ppm), O2 (18.2%), H2O (2.35%) and N2 (balance). The rate of catalytic decomposition was analyzed as a first order reaction with regard to O3 concentration, and the rate constant, k thus obtained was used to evaluate the surface activity. The total surface area of the sample charged in the reactor (Sv) was calculated from the specific surface area and weight of the sample, and used for evaluation of the effect of surface area on catalytic activity. By evaluating k and Sv, the effects of preparation conditions on the activity of the sample were clarified. Furthermore, differences between alkali precipitation and ozone precipitation methods were also clarified. From this study, it was concluded that an active catalyst for ozone decomposition could be prepared by the ozone precipitation method as well as by the alkali precipitation method.