Effect of Ce/Y Addition on Low-Temperature SCR Activity and SO2 and H2O Resistance of MnOx/ZrO2/MWCNTs Catalysts

Chao Yang,Yinming Fan,Bichun Huang,Wei Ling,Lifu Dong

doi:10.3390/catal7060181

Abstract

The effects of SO2 and H2O on the low-temperature selective catalytic reduction (SCR) activity over MnOx/ZrO2/MWCNTs and MnOx/ZrO2/MWCNTs catalysts modified by Ce or Y was studied. MnCeZr and MnYZr catalysts reached nearly 100% and 93.9% NOx conversions at 200 °C and 240 °C, respectively. They displayed a better SO2 tolerance, and the effect of H2O was negligible. The structural properties of the catalysts were characterized by XRD, H2-TPR, XPS, and FTIR before and after the reaction. The results showed that Ce could increase the mobility of the oxygen and improve the valence and the oxidizability of manganese, while the effect of Y was the opposite. This might be the main reason why the catalytic activity of MnCeZr was better than MnYZr in the presence or absence of SO2 and H2O. Doping Ce or Y broadened the active temperature window. Ce or Y, which existed in the catalysts with a high dispersion or at the amorphous state, preferred to react with SO2 to form sulfate species, and protected the manganese active sites from combing with SO2 to some extent, which coincided with the theory of ionic polarization.

Highlights

Selective catalytic reduction (SCR) technology is widely used to remove nitrogen oxides from flue gas and has the advantages of stability and efficiency [1,2]
The addition of Ce or Y loading on the MnOx /ZrO2 /multi-wall carbon nanotubes (MWCNTs) catalysts were prepared using the step impregnation method
Under simulated SCR reaction conditions, Ce improved the activity of the catalysts while the effect of Y was the opposite, they both enlarged the active temperature windows

Summary

Introduction

Selective catalytic reduction (SCR) technology is widely used to remove nitrogen oxides from flue gas and has the advantages of stability and efficiency [1,2]. Conventional commercial catalysts (V2 O5 -WO3 (MoO3 )/TiO2 ) have a relatively narrow temperature window of 300–400 ◦ C, and they are not active at the typical temperature of flue gases (≤250 ◦ C) in the catalytic bed located downstream of the desulfurizer and particulate removal device, and will be deactivated by SO2 and. There is great interests in developing new catalysts which are active at relatively low temperatures and have better resistance to SO2 and H2 O. Some transition metal oxides (Fe, V, Cr, Cu, Mn) supported on catalysts have been found with high activities at low temperatures [5,6,7,8,9]. MnO2 is the most active species among MnO2 , Mn5 O8 , Mn2 O3 , and Mn3 O4 [17]

Methods

Results

Conclusion