Rare earth ions (La, Nd, Sm, Gd, and Tm) regulate the catalytic performance of CeO 2 /Al 2 O 3 for NH 3 -SCR of NO
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Shemin Zhub) College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China; Jiangsu Collaborative Innovation Center for Advanced Inorganic Function Composites, Nanjing Tech University, Nanjing 210009, China; and Shandong Gemsky Environmental Technology Co, Zibo 255086, China
Huiyuan Li Shandong Gemsky Environmental Technology Co, Zibo 255086, China
Yanbao Li College of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009, China (Received 8 February 2017; accepted 22 March 2017)
A series CeO 2/Al2 O3 catalysts was modified with rare earth element (La, Nd, Sm, Gd, and Tm) using extrusion method. The catalytic activities of the obtained catalysts were measured for the selective catalytic reduction (SCR) of NO with NH3 to screen suitable addition of rare earth element. These samples were characterized by X-ray diffraction (XRD), N 2 adsorption (N2-BET), NH3 temperature-programmed desorption analyses (NH3 -TPD), H2 temperature-programmed reduction (H2 -TPR), Raman spectra, pyridine adsorption Fourier-transform infrared (Py-IR) and X-ray photoelectron spectroscopy (XPS), respectively. Results showed that the CeO 2 /Al 2O3 exhibited excellent performance in resisting reactant poisoning caused by vapor and sulfur and the highest catalytic activity (98.35%) at 360 °C when the added Tm/Ce molar ratio is 0.10. The surface acidity of CeO2/Al2 O3 catalyst would be enhanced with the addition of rare earth ions. Consequently, rare earth ion was beneficial to catalytic activity at low temperatures and corresponded to similar law. Analysis revealed that the higher number of acid sites and the more Ce 31 were conductive to obtain the excellent NH3-SCR activity.
I. INTRODUCTION
Nitrogen oxides (NOx) are responsible for a wide range of environment problems such as acid rain, photochemical smog, and the greenhouse effect.1,2 Denitrification has become an active demand to protect the environment, and selective catalytic reduction of NO with NH3 (NH3-SCR) is the most widely used technique.3,4 Currently, the most commercially used catalysts are V2O5(WO3, MoO3)/TiO2 catalysts.5 However, the development of V2O5/TiO2 catalyst is limited because the second pollution of the waste catalyst needs to be solved. Consequently, more and more attention has been given to Contributing Editor: Chongmin Wang Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] c) These authors contributed equally to this work. DOI: 10.1557/jmr.2017.125
develop environment-friendly catalysts with highly NO conversion. Al2O3 with high specific surface area, excellent dispersion, and high temperature resistance of inertia is commonly used in catalyst support.6,7 Because of its unique redox properties and high oxygen storage capacities, CeO2 has attracted much interest in many catalytic fields, such as photocatalysis,8 fuel cell,9 and oxygen permeation membrane.10 For the NH3-SCR, the oxygen storage capacity of CeO2 can be increased by the introduction of other transition and
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