Effect of CaO on NH₃ + NO + O₂ reaction system in the absence and presence of high concentration CO₂

Abstract

The effect of CaO on the NH 3 + NO + O 2 reaction system at 650-850• C was investigated. High CO 2 concentration was added to investigate the effect of CaCO 3 on this reaction system also. Experimental results showed that CaO had a strong catalytic effect on NH 3 decomposition, NH 3 oxidation by O 2 to NO, and NO reduction by NH 3 in the absence of O 2 . The overall effect of CaO on the NO + NH 3 + O 2 reaction was to enhance NH 3 oxidation by O 2 to produce more NO. A small amount of NO 2 and no N 2 O was detected in the outlet gas stream over CaO in the NH 3 + NO + O 2 reaction. NO 2 formation decreased with temperature increase. NO 2 formation in the NH 3 + NO + O 2 reaction over CaO was attributed to the oxidization of NH 3 and NO by O 2 . The performance of CaCO 3 was different from CaO. NH 3 decomposition was promoted, but NH 3 oxidation to NO was inhibited after CaO was converted to CaCO 3 . No catalytic activity for NO reduction was detected in NO + NH 3 reaction over CaCO 3 , but strong activity for NH 3 decomposition was observed. NO and NH 3 outlet concentration over CaCO 3 in the NH 3 + NO + O 2 reaction was lower and higher, respectively, than that of CaO, which was mainly due to the difference of CaO and CaCO 3 for NH 3 oxidation. NO 2 formation was inhibited, but N 2 O was observed over CaCO 3 . N 2 O formation increased with temperature increase at 650-750• C, and then decreased at 750-850

DRIFTS Study of Ammonia Activation over CaO and Sulfated CaO for NO Reduction by NH3

“…Previous studies of NH 3 oxidation over CaO have indicated that -CaN would be formed after NH 3 adsorbed on the CaO surface, and then the formed -CaN would react with O 2 to reproduce CaO and NO, or would react with NO to produce N 2 O (6). Considering almost no N 2 O has been found during the oxidation of NH 3 over CaO in the stream of NH 3 + NO + O 2 + N 2 (6,30), -CaN reacting with NO is of minor importance, suggesting that reaction 4 is of minor importance under this condition. Therefore, the main reaction is -CaN reacting with O 2 to form CaO and NO and providing surface O to reaction 5.…”

Chemical kinetics and particle size effects of activated carbon for free chlorine removal from drinking water

“…To provide clean and safe drinking water through the urban water supply system, water is usually chlorinated to prevent microbial contamination (Yu & Shi 2010). For example, in China, a free chlorine content of !0.3 mg L À1 after 0.5 h of standing at the end point of an urban water supply system is required (Li et al 2010). However, a high concentration of the chlorine in the drinking water may result in serious health concerns.…”

Effect of CaO on NOx Reduction by Selective Non-Catalytic Reduction under Variable Gas Compositions in a Simulated Cement Precalciner Atmosphere

“…CaO also catalyzes reactions between NH 3 and NO in an O 2 -free atmosphere [ 5 , 14 ]. When O 2 is present, these reactions do not apply, and the main effect of CaO is to catalyze NH 3 oxidation with high NO selectivity [ 15 , 16 ].…”