Selective Catalytic Reduction (SCR) of NO with Methane over CoZSM-5 and HZSM-5 Zeolites: On the Role of Free Radicals and Competitive Oxidation Reactions

1996 ◽  
Vol 163 (2) ◽  
pp. 447-456 ◽  
Author(s):  
Dmitri B. Lukyanov ◽  
E.A. Lombardo ◽  
Gustave A. Sill ◽  
Julie L. d'Itri ◽  
W.Keith Hall
Keyword(s):  
Free Radicals ◽  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Oxidation Reactions ◽  
Scr Of No

scholarly journals Unraveling the Structure and Role of Mn and Ce for Selective Catalytic Reduction of NOx in Application-Relevant Catalysts and Conditions

2021 ◽  
Author(s):  
Lieven Gevers ◽  
Linga Enakonda ◽  
Ameen Shahid ◽  
Samy Ould-Chikh ◽  
Pasi Paalanen ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Surface Area ◽  
Active Sites ◽  
Catalytic Reduction ◽  
Intrinsic Activity ◽  
Oxidation Reactions ◽  
Promoting Effect ◽  
N2o Formation ◽  
Intimate Contact

Abstract Mn-based oxides are promising catalysts for the selective catalytic reduction (SCR) of NOx with NH3 at temperatures below 200 °C. There is a general agreement that combining Mn with another metal oxide, such as CeOx improves catalytic activity. However, to date, there is an unsettling debate on the role of Ce as Mn promoter on the SCR reaction. To solve this, here we have systematically studied the effect Ce by preparing, characterizing and testing around 30 catalysts aiming for a well-controlled homogeneous dispersion of the metal oxides. Our results show that, at low-temperature SCR conditions, the intrinsic activity of the Mn active sites is not positively affected by Ce species in intimate contact. In fact, the results suggest that Ce is electronically interacting with Mn and decreasing the active-site average activity. To confirm our findings, activities reported in literature were surface-area normalized and the analysis do not support an increase in activity by Ce addition. Therefore, we can unequivocally conclude that the beneficial effect of Ce is textural, increasing catalyst surface area and therefore the total number of active sites. Besides, addition of Ce is increasing N2 selectivity as it suppresses second-step oxidation reactions and thus N2O formation by structurally diluting the MnOx active sites. Therefore, the textural promoting effect still makes Ce an interesting additive for Mn catalysts.

Hybrid catalysts for the selective catalytic reduction (SCR) of NO by NH 3 . On the role of fast SCR in the reaction network

2016 ◽  
Vol 199 ◽  
pp. 433-438 ◽  
Author(s):  
Mariam Salazar ◽  
Stefanie Hoffmann ◽  
Vera Singer ◽  
Ralf Becker ◽  
Wolfgang Grünert
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Reaction Network ◽  
Hybrid Catalysts ◽  
Scr Of No ◽  
Fast Scr

scholarly journals The Key Role of pH Value in the Synthesis of Titanate Nanotubes-Loaded Manganese Oxides as a Superior Catalyst for the Selective Catalytic Reduction of NO with NH3

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Xiongbo Chen ◽  
Chaoping Cen ◽  
Zhixiong Tang ◽  
Wenhao Zeng ◽  
Dingsheng Chen ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Surface Area ◽  
Manganese Oxides ◽  
Ph Value ◽  
Catalytic Reduction ◽  
Catalyst Support ◽  
Titanate Nanotubes ◽  
Scr Of No ◽  
Scr Catalysts

Titanate nanotubes (TNTs) synthesized by hydrothermal method were increasingly used as the catalyst support for the selective catalytic reduction (SCR) of NO with ammonia. This paper reports the critical process of postwashing to prepare satisfactory TNTs for the uses of SCR catalysts. Herein, alkaline TNTs (TNTs-AL), acidic TNTs (TNTs-AC), and neutral TNTs (TNTs-NE) were synthesized by controlling washing pH value. When these TNTs were utilized as the catalyst supports for manganese oxides (Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE), the key role of pH value was found. Titanate nanosheets, titanate nanorods and titanate nanotubes were dominated in Mn/TNTs-AL, Mn/TNTs-AC, and Mn/TNTs-NE, respectively. MnO2crystal was observed when using TNTs-AC or TNTs-NE as the support. By contrast, Mn3O4and NaNO3were observed when using TNTs-AL as the support. Mn/TNTs-NE showed the best SCR activity, in line with the largest surface area, the best dispersion, and the most active redox property of manganese oxides. Mn/TNTs-AL showed negligible SCR activity, resulting from the minimum surface area, the Mn3O4-dominating crystal structure, and the bad dispersion of manganese oxides.

scholarly journals Novel Preparation of Cu and Fe Zirconia Supported Catalysts for Selective Catalytic Reduction of NO with NH3

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 55
Author(s):  
Katarzyna Świrk ◽  
Ye Wang ◽  
Changwei Hu ◽  
Li Li ◽  
Patrick Da Costa ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Catalytic Reduction ◽  
Supported Catalysts ◽  
Catalytic Performance ◽  
Experimental Conditions ◽  
One Pot ◽  
Nh3 Scr ◽  
Scr Of No ◽  
Temperature Programmed ◽  
Stationary Sources

Copper and iron promoted ZrO2 catalysts were prepared by one-pot synthesis using urea. The studied catalysts were characterized by XRD, N2 physisorption, XPS, temperature-programmed desorption of NH3 (NH3-TPD), and tested by the selective catalytic reduction by ammonia (NH3-SCR) of NO in the absence and presence of water vapor, under the experimental conditions representative of exhaust gases from stationary sources. The influence of SO2 on catalytic performance was also investigated. Among the studied catalysts, the Fe-Zr sample showed the most promising results in NH3-SCR, being active and highly selective to N2. The addition of SO2 markedly improved NO and NH3 conversions during NH3-SCR in the presence of H2O. The improvement in acidic surface properties is believed to be the cause.

The selective catalytic reduction of NOx over a Cu/ZSM-5/SAPO-34 composite catalyst

RSC Advances ◽  
2015 ◽  
Vol 5 (127) ◽  
pp. 104923-104931 ◽  
Author(s):  
Jixing Liu ◽  
Weiyu Song ◽  
Chi Xu ◽  
Jian Liu ◽  
Zhen Zhao ◽  
...  
Keyword(s):  
Selective Catalytic Reduction ◽  
Mass Fraction ◽  
Catalytic Reduction ◽  
Composite Catalyst ◽  
Composite Catalysts ◽  
Scr Of No ◽  
Reduction Of Nox ◽  
Seed Method ◽  
Catalytic Performances

A series of Cu/ZSM-5/SAPO-34 composite catalysts with varying ZSM-5 mass fraction were synthesized using a pre-seed method, and their catalytic performances were tested for selective catalytic reduction (SCR) of NO with NH3.

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