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An Experimental Study on the NH3-SCR of NOx over a Vanadium-based Catlayst

바나듐 계열 촉매를 통한 NOx의 NH3-SCR에 관한 실험적 연구

Jeong, Hee-Chan;Sim, Sung-Min;Kim, Young-Deuk;Jeong, Soo-Jin;Kim, Woo-Seung
정희찬;심성민;김영득;정수진;김우승

  • Received : 2010.08.20
  • Accepted : 2011.07.18
  • Published : 2012.01.01

Abstract

The $NH_3$-SCR characteristics of $NO_X$ over a V-based catalyst are experimentally examined over a wide range of operating conditions, i.e., $170-590^{\circ}C$ and $30,000-50,000h^{-1}$, with a simulated diesel exhaust containing $NH_3$, NO, $NO_2$, $O_2$, $H_2O$, and $N_2$. 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 by ammonia. The best $deNO_X$ efficiency is obtained with a $NO_2/NO_X$ ratio of 0.5 because of an enhanced chemical activity induced by the fast-SCR reaction, while at the $NO_2/NO_X$ ratios above 0.5 the $deNO_x$ activity decreases due to the slow-SCR reaction. The oxidation of ammonia begins to take place at about $300^{\circ}C$ and the reaction products, such as $N_2$, NO, $NO_2$, $N_2O$, and $H_2O$, are produced by the undesirable oxidation reactions of ammonia, particularly at high temperatures above $450^{\circ}C$. Also, $NO_2$ decomposes to NO and $O_2$ at temperatures above $240^{\circ}C$. Therefore, $NO_2$ decomposition and ammonia oxidation reactions deteriorate significantly the SCR catalytic activity at high temperatures.

Keywords

$NH_3$-SCR;$DeNO_X$ efficiency;Oxygen;Space velocity;$NO_2/NO_X$ ratio

References

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Acknowledgement

Grant : 가솔린 다운사이징 엔진 기술