De-NOx Performance and Mechanism of Mn-Based Low-Temperature SCR Catalysts Supported on Foamed Metal Nickel

Baozhong Zhu,Shoulai Yin,Qilong Fang,Zicheng Zhu,Zhaohui Zi,Keke Mao,Yunlan Sun,Jiaxin Li,Guobo Li

doi:10.21577/0103-5053.20180042

Baozhong Zhu, Shoulai Yin + Show 7 more

Open Access

https://doi.org/10.21577/0103-5053.20180042

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Abstract

A series of manganese-based catalysts supported on foamed metal nickel (FMN) with various Mn/Ni ratios was prepared for low-temperature selective catalytic reduction (SCR) of NO with NH3 (NH3-SCR). The effects of calcination temperature, amount of added Mn, optimal operating conditions, and H2O on the elimination of nitrogen oxides (de-NOx) performance of catalysts were studied. The catalysts were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption experiments of NH3 analyses. The experimental results revealed that the Mn7.5/FMN catalyst calcined at 350 oC exhibited the best NO conversion that was ca. 100% at 120-200 oC. Moreover, it had excellent H2O tolerance. The superior activity of the Mn7.5/FMN catalyst, which was calcined at 350 oC, was attributed to the presence of amorphous manganese oxide, more unsaturated Ni atoms and structural defects, an increase in NH3 adsorbance, and the number of surface acid sites. Based on these studies, we established that the reaction of the NH3-SCR with Mn7.5/FMN catalyst mainly exhibits an Eley-Rideal mechanism.

Highlights

Nitrogen oxides (NOx) such as NO and NO2 resulting from fossil fuel combustion are one of the main pollutants in the atmosphere
The sat I and sat II ratios for the Mn7.5/foamed metal nickel (FMN) catalyst calcined at 350 °C are larger than those of the Mn7.5/FMN catalyst calcined at 550 °C, illustrating that there are more unsaturated Ni atoms and structural defects on the surface of the former catalyst
Comparison of the TPD profile of the Mn7.5/FMN catalyst calcined at 350 and 550 °C suggests that the peak areas located at the weak and medium acid sites are larger for the catalyst calcined at 350 °C, while the peak areas of its strong acid sites are smaller. This indicates an increase in NH3 adsorbance and in the number of acid sites on the surface of the Mn7.5/FMN catalyst calcined at 350 °C at low temperature

Summary

Introduction

Nitrogen oxides (NOx) such as NO and NO2 resulting from fossil fuel combustion are one of the main pollutants in the atmosphere. The NO conversion activity of the Mn7.5/FMN catalyst firstly increased and decreased with the rise of calcination temperature. In NH3-SCR, both O2 and NO have oxidative capacity and the oxidation reaction at the catalyst surface is a very critical step.[35] it is essential to study the effect of O2 concentration on the catalytic activity.

Results

Conclusion