A superior catalyst with dual redox cycles for the selective reduction of NOx by ammonia

Liu, Zhiming; Yang, Yi; Li, Junhua; Woo, Seong Ihl; Wang, Boyu; Cao, Xingzhong; Li, Zhuoxin

doi:10.1039/c3cc43041c

Cited by 185 publications

(94 citation statements)

References 18 publications

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“…26,27 The onset consumption order is FeW(5) (555 °C) < FeW(10) (574 °C) < FeW(3) (579 °C) < FeW(1) (668 °C), representing that H 2 reduction is promoted first, and then suppressed with decreased concentration of WO 3 . 29 As is presented in Fig.5b, it is clear that FeW (5) catalyst has the greatest amount of chemisorbed oxygen species (O α /(O α +O β )=29.4%) among the FeW(x) catalysts. However, The H 2 consumption amounts (the total peak areas) are significantly decreased by the tungsten doping.…”

Section: Redox Propertiesmentioning

confidence: 75%

Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Peng

et al. 2015

Catal. Sci. Technol.

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A series of novel FeW(x) catalysts with different Fe/W molar ratios prepared by the coprecipitation method were investigated on selective catalytic reduction (SCR) of NO x with NH 3 . Among the tested catalysts, the FeW(5) shows the highest catalytic activity, nearly 100% of NO conversion and N 2 selectivity from 250 to 450 °C, and good H 2 O/SO 2 durability above 300 °C. After the introduction of WOx species, the lattice structure change of hematite phase and high dispersion of WOx on the surface of catalysts are observed for FeW(x) catalysts. The abundance of surface adsorbed oxygen arises from charge imbalance and unsaturated chemical bonds formation by the interaction between iron oxide species and tungsten oxide species. The Brønsted acid sites are mainly supplied by the W-OH bond, while the Lewis acid sites are related to iron oxide species. Meanwhile the addition of WO x not only leads to the formation of lower-valent iron species and consequently decreases the Lewis acidity, thereby improving N 2 selectivity, but also enhances the stability of surface acid sites and adsorption of monodentate nitrite and NO 2 species, which account for the excellent catalytic performance of FeW(5) at low temperature. According to the reaction details, Brønsted acid sites play a leading role at low temperature and Lewis acid sites may be the major active centers at high temperature in the SCR process for FeW(x) catalysts.

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Section: Redox Propertiesmentioning

confidence: 75%

Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Peng

et al. 2015

Catal. Sci. Technol.

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“…Referring to the standard Raman spectrum, the peaks at 640 cm −1 , 515 cm −1 , 398 cm −1 , 198 cm −1 and 147 cm −1 are representative peaks of anatase TiO2. The anatase bands at 515 and 398 cm −1 could be attributed to the Ti-O-stretching vibration, and the bands at 640 cm −1 could be attributed to O-Ti-O-bending vibrations [18,19]. Obviously, the Raman spectra of Ce/Ti-400 coincides with the standard anatase TiO2 Raman spectrum well.…”

Section: Catalytic Activity Testsmentioning

confidence: 51%

Active Site of O2 and Its Improvement Mechanism over Ce-Ti Catalyst for NH3-SCR Reaction

et al. 2018

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Abstract:The current study on Ce-Ti catalyst was mainly focused on the function of NH 3 and NO adsorption sites. In our study, by comparing Ce-Ti (doped catalyst) to Ce/Ti (supported catalyst), the active site of O 2 and its improvement mechanism over Ce-Ti catalyst for NH 3 -Selective catalytic reduction (SCR) reactions were investigated. For Ce-Ti catalyst, a cerium atom was confirmed entering a TiO 2 crystal lattice by X-ray diffraction (XRD) and Raman; the structure of Ce--Ti ( represents oxygen vacancy) in Ce-Ti catalyst was confirmed by X-ray photoelectron spectroscopy (XPS) and Photoluminescence spectra (PL spectra). The nature of this structure was characterized by electron paramagnetic resonance (EPR), Ammonia temperature-programmed desorption (NH 3 -TPD), hydrogen temperature-programmed reduction (H 2 -TPR), Nitric oxide temperature-programmed desorption (NO-TPD) and In situ DRIFT. The results indicated that oxygen vacancies had a promotive effect on the adsorption and activation of oxygen, and oxygen was converted to superoxide ions in large quantities. Also, because of adsorption and activation of NO and NH 3 , electrons were transferred to adsorbed oxygen via oxygen vacancies, which also promoted the formation of superoxide ions. We expected that our study could promote understanding of the active site of O 2 and its improvement mechanism for doped catalyst.

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“…Furthermore, previous literature had proven that a redox cycle existed between Ce and Cu cations over Cu‐Ce‐Ti catalyst, and the electron transfer could be expressed as follows: Ce 4+ ‐O 2 ‐ – Cu 2+ + e ‐

\Leftrightarrow

Ce 4+ ‐O 2 ‐ – Cu +

\Leftrightarrow

Ce 3+ ‐O 2‐ – Cu 2+ . This process results in a decrease in the energy required for the electron transfer between Cu and Ce active sites, promoting the activation of NH 3 and NO (Figure b and Figure ).…”

Section: Resultsmentioning

confidence: 99%

The effective promotion of trace amount of Cu on Ce/WO₃‐ZrO₂‐TiO₂ monolithic catalyst for the low‐temperature NH₃‐SCR of NO_x

Feng

et al. 2017

Can J Chem Eng

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The selective catalytic reduction of NOx with NH3 (NH3‐SCR) activity of 0.10 g/g CeO2/WO3‐ZrO2‐TiO2 (Ce/WZT) in low temperature range was greatly enhanced by the addition of 0.00010 g/g Cu (Cu/Ce mass ratio = 1:1000). The temperature of complete NOx conversion (T90) decreased as much as 36 °C (from 263 °C to 227 °C) under a gas hourly space velocity (GHSV) of 30 000 h−1. XPS, NH3/O2‐TPD, H2‐TPR, XRD, and FTIR characterizations revealed that the interaction between Cu and Ce, more active oxygen species, stronger NH3 and NO oxidation ability, better redox ability, together with the abundant Brønsted acid sites contributed to better catalytic activity of 0.00010 g/g Cu‐0.10 g/g Ce/WO3‐ZrO2‐TiO2 (CC/WZT) catalyst at low temperatures.

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A superior catalyst with dual redox cycles for the selective reduction of NOx by ammonia

Cited by 185 publications

References 18 publications

Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Active Site of O2 and Its Improvement Mechanism over Ce-Ti Catalyst for NH3-SCR Reaction

The effective promotion of trace amount of Cu on Ce/WO₃‐ZrO₂‐TiO₂ monolithic catalyst for the low‐temperature NH₃‐SCR of NO_x

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A superior catalyst with dual redox cycles for the selective reduction of NOx by ammonia

Cited by 185 publications

References 18 publications

Selective catalytic reduction of NO with NH3 over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Selective catalytic reduction of NO with NH3 over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Active Site of O2 and Its Improvement Mechanism over Ce-Ti Catalyst for NH3-SCR Reaction

The effective promotion of trace amount of Cu on Ce/WO3‐ZrO2‐TiO2 monolithic catalyst for the low‐temperature NH3‐SCR of NOx

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Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

Selective catalytic reduction of NO with NH₃ over novel iron–tungsten mixed oxide catalyst in a broad temperature range

The effective promotion of trace amount of Cu on Ce/WO₃‐ZrO₂‐TiO₂ monolithic catalyst for the low‐temperature NH₃‐SCR of NO_x