Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

doi:10.1016/j.apsusc.2013.04.076

Cited by 75 publications

(25 citation statements)

References 71 publications

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“…In agreement with several previous reports [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Mn-based catalysts displayed significant SCR activity already at low temperatures where the 6 commercial V-based catalyst gave poor performance: at 150°C the NO x conversion over V 2 O 5 -WO 3 /TiO 2 catalyst was ca. 15%, whilst it was 30% over 10Mn/Z catalyst, and slightly above 80% for 10Mn/T catalyst.…”

Section: Nh 3 -Scr Testssupporting

confidence: 93%

“…Therefore, in recent years attention has been paid to the development of low temperature SCR catalysts to be used in a tail-end configuration after a flue gas desulphurization unit [11], such as a Dry or Sea Water Scrubber [9]. For the low temperature SCR reaction (50-250°C), supported transition metal oxide catalysts have been investigated [6, [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In particular MnO x based catalysts supported on TiO 2 [6, 10,12,13,[15][16][17][18][21][22][23][24], zeolites [14] or even activated carbon [20] were reported as active and stable at low temperature.…”

Section: Introductionmentioning

confidence: 99%

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Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Cimino

Lisi

Tortorelli

2016

Chemical Engineering Journal

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Section: Nh 3 -Scr Testssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Cimino

Lisi

Tortorelli

2016

Chemical Engineering Journal

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“…Recent applications include diesel engines, such as those found on large ships, diesel locomotives, and even automobiles. [3][4][5] However, ammonia is considered a hazardous chemical. 6 Therefore, instead of using ammonia, most SCR systems use urea (nontoxic).…”

mentioning

confidence: 99%

Electrochemically Induced Conversion of Urea to Ammonia

Botte

2015

ECS Electrochemistry Letters

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A novel electrochemically induced method for ammonia synthesis (eU2A) on demand from urea in alkaline media was demonstrated. A Nickel based electrode was employed as the active catalyst. The effective rate of ammonia generation of the eU2A process at 70 • C is ∼28 times higher than the thermal hydrolysis (THU) of urea. The eU2A operates at lower temperature (55% lower) and pressure (6 times lower) than the THU; this could lead to significant energy savings. The process finds applications on selective catalytic reduction (SCR) for the removal of nitride oxide from combustion systems (e.g., diesel vehicles, power plants, etc. 3-5 However, ammonia is considered a hazardous chemical.6 Therefore, instead of using ammonia, most SCR systems use urea (nontoxic). Urea can be thermally hydrolyzed into ammonia on demand as shown in Eq. 1The thermal conversion of urea to ammonia processes used in power plants -such as urea pyrolysis (540• C) 8 and urea hydrolysis (150• C, 5-6 atm) 9 -are not suitable for mobile engines since the reaction conditions are inaccessible. Current thermal hydrolysis of urea (THU) processes employed in diesel engine vehicles dose urea by injecting urea-water solutions (this mixture is known as diesel effluent fluid, DEF, 32.5% weight urea in deionized water) and use the exhaust temperature to convert urea to ammonia. However, in low-load urban driving, the exhaust temperature goes from 300• C to lower than 130• C. The overall NOx conversion effectiveness in the system is low due to the curtailed urea dosing caused by insufficient conversion of urea. 10 In addition, the quality of the DEF needs to be high since the SCR catalyst can be damaged if there is contamination in DEF (e.g., due to minerals in water used for making DEF 11 ). In this paper, we demonstrate a new technology that allows the electrochemical conversion of urea to ammonia, the eU2A process. 12,13The process allows the production of ammonia on demand by applying a cell voltage as depicted in Fig. 1a. 12,13 This technology could enable decoupling the ammonia production from the exhaust system in diesel engine vehicle SCR applications, as well as portable urea to ammonia reactors. ExperimentalThe eU2A reactor was built at the Center for Electrochemical Engineering Research and presented schematically in Fig. 1b. A heat jacket with a controller (Econo 12125-14) was used to heat and maintain the temperature of the reagent in the reactor. The eU2A process was performed in a two electrodes system and the cell voltage was controlled by an Arbin BT2000 potentiostat. The anode (working electrode) of the reactor was made by Ni beads and a Ni mesh was used as cathode, refer to Section S1 of supplementary information (SI) for details. Part of the ammonia produced was dissolved in the solution in the reactor, while the rest in vapor phase was captured in a glass vessel containing * Electrochemical Society Student Member. * * Electrochemical Society Fellow. z E-mail: botte@ohio.edu 1 L of 1 M sulfuric acid solution (Fig. 1b). An ammonia ion selec...

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“…The H 2 -TPR profiles of the three catalysts are shown in Figure 5. According to the previous reports, MnO 2 and Mn 2 O 3 always reduced firstly to Mn 3 O 4 in the lower temperature range, and secondly to MnO at higher temperature range [30,31]. With respect to the H 2 -TPR profiles of the Mn/TNTs-AC and Mn/TNTs-NE catalysts, the two-step reduction was obviously observed.…”

Section: Redox Propertymentioning

confidence: 57%

“…550 ∘ C and 750 ∘ C, respectively. The former peak could be ascribed to the desorption of chemisorbed ammonia at strong acid sites, and the later peak was generated by the decomposition of residual NaNO 3 and Mn-nitrate [30]. As to the NH 3 -TPD profile of the Mn/TNTs-AL sample, a strong peak ranging within 350-710 ∘ C was observed.…”

Section: Physical Characteristics and Chemical Compositionmentioning

confidence: 95%

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

Chen

Cen

Tang

et al. 2013

Journal of Nanomaterials

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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.

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Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

Cited by 75 publications

References 71 publications

Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Electrochemically Induced Conversion of Urea to Ammonia

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

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Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

Cited by 75 publications

References 71 publications

Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Low temperature SCR on supported MnOx catalysts for marine exhaust gas cleaning: Effect of KCl poisoning

Electrochemically Induced Conversion of Urea to Ammonia

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

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Resources

About

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