바나듐 계열 촉매를 통한 NOX의 NH3-SCR에 관한 실험적 연구

Abstract

The NH3-SCR characteristics of NOX over a V-based catalyst are experimentally examined over a wide range of operating conditions, i.e., 170-590°C and 30,000-50,000 h-1, with a simulated diesel exhaust containing NH3, NO, NO2, O2, H2O, and N2. The influences of the space velocity and oxygen concentration on the standard-SCR reaction are analyzed, and it is shown that the low space velocity and high oxygen concentration promote the SCR activity b ammonia. The best deNOX efficiency is obtained with a NO2/NOX ratio of 0.5 because of an enhanced chemical activity induced by the fast-SCR reaction, while at the NO2/NOX ratios above 0.5 the deNOX activity decreases due to the slow-SCR reaction. The oxidation of ammonia begins to take place at about 300°C and the reaction products, such as N2, NO, NO2, N2O, and H2O, are produced by the undesirable oxidation reactions of ammonia, particularly at high temperatures above 450°C. Also, NO2 decomposes to NO and O2 at temperatures above 240°C. Therefore, NO2 decomposition and ammonia oxidation reactions deteriorate significantly the SCR catalytic activity at high temperatures.