Catalytic activity and mechanism of selective catalytic oxidation of ammonia by Ag–CeO 2 under different preparation conditions

Abstract

(1) Ag/CeO 2 -IM catalyst synthesized by impregnation method achieves 90% conversion of NH 3 at 200 °C. (2) The better low-temperature activity of Ag/CeO 2 -IM catalysts stems from the high Ag 0 content, which has stronger redox properties. Given the problem of the high-temperature window of CeO 2 catalyst activity, this study evaluated the catalytic properties of Ag/CeO 2 prepared by changing the preparation methods and loadings. Our experiments showed that Ag/CeO 2 -IM catalysts prepared by the equal volume impregnation method could have better activity at lower temperatures. The Ag/CeO 2 -IM catalyst achieves 90% NH 3 conversion at 200 °C, and the main reason is that the Ag/CeO 2 -IM catalyst has more vital redox properties, and the NH 3 catalytic oxidation temperature is lower. However, its high-temperature N 2 selectivity still needs to be improved and may be related to the less acidic sites on the catalyst surface. On both catalyst surfaces, the i-SCR mechanism governs the NH 3 -SCO reaction.