Mechanistic study of lean NOx reduction with propene over Ag/Al2O3 by in situ DRIFTS

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	Mechanistic study of lean NOx reduction with propene over Ag/Al2O3 by in situ DRIFTS
	Yu, YB; He, H
刊名	CHINESE JOURNAL OF CATALYSIS
	2003
卷号	24 期号:5 页码:385-390
关键词	silver alumina supported catalyst in situ diffuse reflectance infrared Fourier transform spectroscopy propene selective catalytic reduction nitric oxides reaction mechanism water vapor
英文摘要	Ag/Al2O3 Is known as one of the most effective catalysts for the hydrocarbon selective catalytic reduction (HC-SCR) of NOx. However, the HC-SCR of NO,. is usually suppressed in the presence of water vapor, which inevitably exists in various exhausts, resulting in a difficulty for utilization of the catalysts. Thus, it is necessary to understand the effect of water vapor on mechanistic level. The Ag/Al2O3 catalyst with Ag loading of 5% was prepared by the impregnation method. Al2O3 powder was dissolved in an appropriate amount of silver nitrate aqueous solution. The sample was dried at 393 K for 3 It and calcined at 873 K for 3 h in air. The catalyst activity test was carried out in a fixed-bed reactor with a gas mixture containing 0.08% NO, 0.1714% C3H6, 10.0% O-2 and a balance of N-2 at a total flow rate of 4 L/min ( W/F = 0.018 g/cm(3), GHSV = 50 000 h(-1)) in a temperature range of 473 similar to 923 K. Water vapor was supplied with a syringe pump into the gas stream and vaporized by a coiled heater set at inlet of the reactor. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra were recorded on a Nexus 670 (Thermo Nicolet) FT-IR equipped with an in situ diffuse reflection chamber and a high sensitivity MCT detector. Because water vapor in gas phase and adsorbed water on Ag/Al2O3 surface strongly absorb infrared ray, a reference spectrum of Ag/Al2O3 in a flow Of O-2 + N-2 (and water vapor, if any) was subtracted from each spectrum at the same temperature respectively. The mechanism of lean NOx reduction with C3H6 over Ag/Al2O3 was studied by in situ DRIFTS under the real reaction condition and the results are in good agreement with our previous conclusions obtained in a vacuum system, suggesting that R-ONO and R-NO2 species are formed by the reactions Of C3H6 with NO2 and/or NO3- species and convert to Ag-NCO and Al-NCO species over the Ag/Al2O3 surface. This is the rate-determining step in catalytic reduction of NO into N-2 in a steady state because Ag-NCO and Al-NCO species have very high reactivity for converting NOx and O-2 to N-2 and CO2. The presence of water vapor suppresses the formation of R-ONO and R-NO2 on the Ag/Al2O3 surface and thus limits the reaction rate. These results indicate that it is necessary to design a water resistant catalyst or to find an effective reductant to vary the reaction path.
研究领域[WOS]	Chemistry ; Engineering
WOS记录号	WOS:000183665900016
内容类型	期刊论文
源URL	[http://ir.rcees.ac.cn/handle/311016/23655]
专题	生态环境研究中心_大气环境科学实验室
推荐引用方式 GB/T 7714	Yu, YB,He, H. Mechanistic study of lean NOx reduction with propene over Ag/Al2O3 by in situ DRIFTS[J]. CHINESE JOURNAL OF CATALYSIS,2003,24(5):385-390.
APA	Yu, YB,&He, H.(2003).Mechanistic study of lean NOx reduction with propene over Ag/Al2O3 by in situ DRIFTS.CHINESE JOURNAL OF CATALYSIS,24(5),385-390.
MLA	Yu, YB,et al."Mechanistic study of lean NOx reduction with propene over Ag/Al2O3 by in situ DRIFTS".CHINESE JOURNAL OF CATALYSIS 24.5(2003):385-390.