Selective Catalytic Reduction of NOx with Ammonia: NH3-SCR
Selective Catalytic Reduction of NOx with Hydrocarbons: HC-SCR
Application Research on Diesel Engine Emission Control
Catalytic Purification of Indoor Air Pollutants
Heterogeneous Atmospheric Chemistry
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Selective Catalytic Reduction of NOx with Hydrocarbons: HC-SCR

Using on-board diesel fuel as a reductant for SCR technology (diesel-SCR) can avoid infrastructure development for reductant storage and delivery, simplifying exhaust after-treatment systems. With this in mind, diesel-SCR can be regarded as the ultimate goal for the reduction of NOx emission from diesel engines. When employing diesel as a reductant, however, the light-off temperature for NOx reduction is still too high to be used for commercial application in diesel vehicles. It is therefore highly desirable to obtaina thorough understanding of the structure-activity relationship of the HC-SCR system for NOx reduction; and then develop new principles and methods for NOx reduction by on-board fuel with high efficiency.

 

Characteristics of reductants with high efficiency for HC-SCR

ü A surface enolic species (R-CH=CH-O-) produced by the partial oxidation of ethanol, which played a key role in the ethanol-SCR of NOx, was found for the first time on the surface of Ag/Al2O3 and reported.

ü Alcohols containing at least one α-H and one C-C bond are a prerequisite for their partial oxidation to produce active enolic species over Ag/Al2O3, providing an intrinsic criterion for obtaining alcohol-SCR with high efficiency.

ü Employing hydrocarbons containing at least two carbon atoms is necessary for the formation of active enolic species during their partial oxidation over Ag/Al2O3, providing a principle for the promoting effect of H2 on the low-temperature activity of HC-SCR of NOx.

Activity of butanols with different structures for the SCR of NOx and the formation of surface enolic species over Al2O3

 


Structure-activity relationship of HC-SCR system based on chemical bond analysis

ü Surface enolic species, produced by the partial oxidation of alcohols over Ag/Al2O3, prefer to adsorb on or close to oxidized Ag sites.

ü A mixing of Ag, O, and Al orbitals in the Ag-O-Al entity significantly decreases the band gap and likely enhances the reactivity of this entity, therefore serving as the active center for ethanol-SCR over Ag/Al2O3.


Principles for approaching diesel-SCR

ü Diesel-SCR technology with high efficiency for diesel engine emission control: diesel reforming coupled with HC-SCR

ü Principles for diesel reforming: transformation of diesel to active small hydrocarbons or oxygenated small hydrocarbons containing at least two carbon atoms, beneficial for the formation of enolic species; in situ H2 production to enhance low-temperature activity and expand the operating temperature window.


                                         (Chem. Commun., 2014, 50: 8445)

Related Papers:

35. Hua Deng, Yunbo Yu, Hong He*, Discerning the role of AgOAl entities on Ag/-Al2O3 surface in NOx Selective reduction by ethanol, J. Phys. Chem. C, 119, (2015) 31323142.

34. Yunbo Yu, Yi Li, Xiuli Zhang, Hua Deng, Hong He*, Yuyang Li, Promotion effect of H2 on the ethanol oxidation and NOx reduction with ethanol over Ag/Al2O3 catalyst, Environ. Sci. Technol., 49, (2015) 481488.

33. Hua Deng, Yunbo Yu, Fudong Liu, Jinzhu Ma, Yan Zhang, Hong He*, Nature of Ag Species on Ag/g-Al2O3: A Combined Experimental and theoretical study, ACS Catal., 4, (2014) 27762784.

32. Fudong Liu, Yunbo Yu, Hong He*, Environmentally-benign catalysts for the selective catalytic reduction of NOx from diesel engines: Structure-activity relationship and reaction mechanism aspects, Chem. Commun., 50 (62), (2014) 84458463.

31. Yunbo Yu, Hong He*, Xiuli Zhang, Hua Deng, A common feature of H2-assisted HC-SCR over Ag/Al2O3, Catal. Sci. Technol., 4, (2014) 12391245.

30. Zhao Jiaojiao, Yu Yunbo*, Han Xue, He Hong, Fuel reforming over Ni‐based catalysts coupled with selectivecatalytic reduction of NOx, Chin. J. Catal.,34, (2013) 1407–1417.

29. Yunbo Yu*, Jiaojiao Zhao, Yong Yan, Xue Han, Hong He, A cyclic reaction pathway triggered by ammonia for the selective catalytic reduction of NOx by ethanol over Ag/Al2O3, Appl.Catal. B, 136-137, (2013) 103111.

28. HeHong*, Liu Fudong, Yu Yunbo, ShanWenpo, Environmental-friendly SCR technique (selective catalytic reduction) for the deNOx process from diesel engines,SCIENCE CHINA: Chemistry,42, (2012) 446468. (in Chinese)

27. Yong Yan,Yunbo Yu*, Hong He, Jiaojiao Zhao, Intimate contact of enolic species with silver sites benefits the SCR of NOx by ethanol over Ag/Al2O3, J. Catal., 293, (2012) 1326.

26. He Hong*, Yu Yunbo, Li Yi, Wu Qiang, Zhang Xiuli, Zhang Changbin, Shi Xiaoyan, Song Xiaoping,Advances in mechanistic and practical studies on the selective catalytic reduction of NOx by oxygenated hydrocarbons over Ag/Al2O3, Chin. J. Catal., 31, (2010) 491501. (in Chinese)

25. Yunbo Yu, Xiaoping Song, Hong He*, Remarkable influence of reductant structure on the activity of alumina-supported silver catalyst for the selective catalytic reduction of NOx, J Catal.,271, (2010) 343350.

24. Yi Li, Xiuli Zhang, Hong He*, Yunbo Yu, Tao Yuan, Zhenyu Tian, Jing Wang, Yuyang Wang, Effect of the pressure on the catalytic oxidation of volatile organic compounds over Ag/Al2O3 catalyst,Appl. Catal. B, 89, (2009) 659664.

23. Xiuli Zhang, Hong He*, Hongwei Gao, Yunbo Yu, Experimental and theoretical studies of surface nitrate species on Ag/Al2O3 using DRIFTS and DFT,Spectrochim. Acta A,71, (2008) 14461451.

22. Hong He*, Xiuli Zhang, Qiang Wu, Changbin Zhang, Yunbo Yu, Review of Ag/Al2O3-reductant system in the selective catalytic reduction of NOx, Catal. Surv. Asia,12, (2008) 3855.

21. Xiuli Zhang, Yunbo Yu, Hong He*, Effect of hydrogen on reaction intermediates in the selective catalytic reduction of NOx by C3H6, Appl. Catal. B, 76, (2007) 241247.

20. Yunbo Yu, Xiuli Zhang, Hong He*, Evidence for the formation, isomerization and decomposition of organo-nitrite and -nitro species during the NOx reduction by C3H6 on Ag/Al2O3, Appl. Catal. B, 75, (2007) 298302.

19. Xiuli Zhang, Hong He*, Zichuan Ma, Hydrogen promotes the selective catalytic reduction of NOx by ethanol over Ag/Al2O3, Catal. Commun., 8, (2007) 187192.

18. Shuxia Xie, Jin Wang, Hong He*, Poisoning effect of sulphate on the selective catalytic reduction of NOx by C3H6 over Ag-Pd/Al2O3, J. Mol. Catal.A:Chem.,266, (2007) 166172.

17. Qiang Wu, Yunbo Yu, Hong He*, Mechanistic study of selective catalytic reduction of NOx with C2H5OH and CH3OCH3 over Ag/Al2O3 by in situ DRIFTS, Chin. J. Catal., 27(11), (2006) 993998.

16. Shuxia Xie, Yunbo Yu, Jin Wang, Hong He*, Effect of SO2 on the performance of Ag-Pd/Al2O3 for the selective catalytic reduction of NOx with C2H5OH, J. Environ. Sci.,18(5), (2006) 973978.

15. Qiang Wu, Hongwei Gao, Hong He*, Study on effect of SO2 on the selective catalytic reduction of NOx with propene over Ag/Al2O3 by in situ DRIFTS,Chin. J. Catal.,27(5), (2006) 403408.

14. Qiang Wu, Hongwei Gao, Hong He*, Conformational analysis of sulfate species on Ag/Al2O3 by means of theoretical and experimental vibration spectra,J. Phys. Chem. B, 110, (2006) 83208324.

13. Qiang Wu, Qingcai Feng, Hong He*, Disparate effects of SO2 on the selective catalytic reduction of NO by C2H5OH and IPA over Ag/Al2O3,Catal. Commun.,7, (2006) 657661.

12. Hongwei Gao, Hong He*, Yunbo Yu, Qingcai Feng, Density functional theory (DFT) and DRIFTS investigations of the formation and adsorption of enolic species on Ag/Al2O3 surface, J. Phys. Chem. B, 109, (2005) 1329113295.

11. Qiang Wu, Hong He*, Yunbo Yu, In situ DRIFTS study of the selective catalytic reduction of NOx with alcohols over Ag/Al2O3 catalyst: role of surface enolic species, Appl. Catal. B, 61, (2005) 107113.

10. Hong He*, Yunbo Yu, Selective catalytic reduction of NOx over Ag/Al2O3 catalyst: from reaction mechanism to diesel engine test, Catal. Today, 100, (2005) 3747.Invited paper

9Hongwei Gao, Hong He*, Conformational analysis and comparison between theoretical and experimental vibration spectra for isocyanate species on Ag/Al2O3 catalyst, Spectrochim. Acta A, 61, (2005) 12331238.

8.  Jin Wang, Hong He*, Shuxia Xie, Yunbo Yu, Novel Ag-Pd/Al2O3-SiO2 for lean NOx reduction by C3H6 with high tolerance of SO2, Catal. Commun., 6, (2005) 195200.

7.  Jin Wang, Hong He*, Qingcai Feng, Yunbo Yu, Kiyohide Yoshida, Selective catalytic reduction of NOx by C3H6 over an Ag/Al2O3 catalyst with a small quantity of noble metal, Catal. Today, 9395, (2004) 783789.

6.  Hong He*, Changbin Zhang, Yunbo Yu, A comparative study of Ag/Al2O3 and Cu/Al2O3 catalysts for the selective catalytic reduction of NO by C3H6,Catal. Today,90, (2004) 191197.

5.  Yunbo Yu, Hong He*, Qingcai Feng, Hongwei Gao, Xin Yang, Mechanism of the selective catalytic reduction of NOx by C2H5OH over Ag/Al2O3, Appl. Catal. B,49, (2004) 159171.

4 . Yunbo Yu, Hong He*, Qingcai Feng, Novel enolic surface species during partial oxidation of CH3CHO, C2H5OH, and C3H6 on Ag/Al2O3: an in situ DRIFTS study, J. Phys. Chem. B,107, (2003) 1309013092.

3. Hong He*, Jin Wang, Qingcai Feng, Yunbo Yu, Kiyohide Yoshida, Novel Pd promoted Ag/Al2O3 catalyst for the selective reduction of NOx, Appl. Catal. B, 46, (2003) 365370.

2. Satosi Sumiya, Hong He, Akira Abe, Nobutsune Takezawa, Kiyohide Yoshida, Formation and reactivity of isocyanate (NCO) species on Ag/Al2O3, J. Chem. Soc., Faraday Trans., 94(15), (1998) 22172219.

1. Satoshi Sumiya,Mika Saito, Hong He, Qingcai Feng, Nobutsune Takezawa, Kiyohide Yoshida, Reduction of lean NOX by ethanol over Ag/Al2O3 catalysts in the presence of H2O and SO2, Catal. Lett., 50, (1998) 8791.

 
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