An In Situ DRIFTS Study on SCR of NO with NH 3 Over V 2 O 5 /AC Surface
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An In Situ DRIFTS Study on SCR of NO with NH3 Over V2O5/AC Surface Dekui Sun Æ Qingya Liu Æ Zhenyu Liu Æ Guoqing Gui Æ Zhanggen Huang
Received: 19 May 2009 / Accepted: 26 June 2009 / Published online: 9 July 2009 Ó Springer Science+Business Media, LLC 2009
Abstract Selective catalytic reduction (SCR) of NO with NH3 on an activated coke supported V2O5 (V2O5/AC) catalyst was studied at 200 °C by in-situ diffuse reflectance infrared Fourier transform spectroscopy. Results indicate that NH3 is adsorbed in the forms of coordinated NH3, NH4? and –NH2. V2O5 promotes formation of –NH2. NO is oxidized to NO2 in the presence of O2. –NH2 and NO2 are the intermediates of the SCR reaction. Keywords NO NO2
V2O5/AC DRIFTS SCR NH3
1 Introduction Selective catalytic reduction (SCR) of NO with NH3 was regarded as the most effective method for NOx removal from flue gas [1]. The main SCR catalysts used in industrial application are V2O5/TiO2 promoted by WO3 or MoO3.
D. Sun Z. Liu (&) G. Gui Z. Huang State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, 030001 Taiyuan, People’s Republic of China e-mail: [email protected] D. Sun e-mail: [email protected] D. Sun Graduate University of Chinese Academy of Sciences, 100039 Beijing, People’s Republic of China Q. Liu Z. Liu State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, 100029 Beijing, People’s Republic of China
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These catalysts must be used at temperatures higher than 350 °C to avoid deactivation by ammonium bisulfate formed from reactions between SO2, NH3, O2 and H2O [2]. Consequently, the SCR unit must be installed in the upstream of particulates removal units, which makes retrofitting of the SCR unit to existing boiler systems difficult. For this reason, catalysts active at lower temperatures have been studied extensively. Many catalysts were reported to be active for the SCR at low temperatures especially those with carbon as the main component, including activated carbon (AC) [3], carbon fibers [4, 5], and AC supported MnOx, FeOx, CuO or V2O5 [6–9]. Among these catalysts, AC-supported V2O5 catalysts (V2O5/AC) are more promising because their activities are even promoted by SO2 under low moisture conditions [2, 10–12]. AC surface was suggested to catalyze reactions between ammonium bisulfate and NO, and V2O5 was suggested to adsorb and activate NH3 [2, 13]. Galvez et al. [14] studied mechanism of the SCR over a V2O5/AC catalyst. Based on diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) spectra of the catalyst under conditions of NO ? NH3 ? O2, NH3 ? O2 and NO at 150 °C, they proposed that the SCR involves reactions of gaseous NO with the adsorbed NH3, which agrees with the suggestion of Zhu et al. [11]. Teresa et al. studied the SCR over a carbon-ceramic supported vanadia catalyst at 150 °C, but suggested an different mechanism, which involves reactions between adsorbed NO and NH3 (i.e., a Langmuir–Hinshelwood mechanism) based on TPD-MS results [12
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