On the Mechanism of Ammonia SCR over Cu- and Fe-Containing Zeolite Catalysts

Jiang, Ting; Lobo, Raúl F.

doi:10.1007/430_2018_23

Cited by 10 publications

(13 citation statements)

References 95 publications

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“…On the other hand, we can clearly rule out that "Peak A" is due to the coordination of NO to the iron center, as was suggested in Ref. 27.…”

Section: Resultssupporting

confidence: 66%

“…19 Even though many details of the catalytic mechanism have been elucidated, the SCR mechanism is still not fully understood. [24][25][26][27] This is particularly true for Fe-doped zeolite catalysts, which have been studied less extensively than Cu-doped zeolite catalysts.…”

Section: Introductionmentioning

confidence: 99%

“…1a (Ref. 27). First, in the reduction half-cycle, NO and NH 3 react to N 2 and H 2 O while reducing the catalytic metal center.…”

Section: Introductionmentioning

confidence: 99%

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Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Rudolph¹,

Jacob²

2019

Preprint

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<div> <div> <div> <p>We computationally investigate the mechanism of the reduction half-cycle of the selective catalytic reduction (SCR) of nitrogen oxides with ammonia. We compare both Fe- and Cu-doped zeolite catalysts and aim at exploring all accessible reaction pathways. From our calculations, a comprehensive picture emerges that unifies sev- eral previous mechanistic proposals. We find that both for Fe and for Cu catalysts, different reaction pathways are feasible, but some of the possible reaction pathways differ in these two cases. Our computational results provide a basis for the inter- pretation of in situ spectroscopic investigations that can possibly distinguish the different mechanistic pathways. </p> </div> </div> </div>

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“…On the other hand, we can clearly rule out that "Peak A" is due to the coordination of NO to the iron center, as was suggested in Ref. 27.…”

Section: Resultssupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Rudolph¹,

Jacob²

2019

Preprint

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“…The burning of fossil fuels and intense human activities have caused sharp increases in the emissions of CO 2 , SO x (SO 2 and SO 3 ) and nitrogen oxides (NO x , mainly NO and NO 2 ) in the atmosphere, which have resulted in a series of environmental problems, such as acid rain, photochemical smog, the greenhouse effect and haze [1][2][3]. As a very stable gas in the atmosphere with 114 years of half-life, NO x has attracted considerable attention in recent years due to its much higher greenhouse gas effect: 298 CO 2 global warning equivalents in 100 years [4]. Selective catalytic reduction of NO x by ammonia (NH 3 -SCR) is one of the most widely used methods to reduce NO x emissions from both industrial off-gases and diesel engine exhausts due to its high efficiency and low cost, as it can use liquid ammonia or urea as the NH 3 source [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…Limited by the narrow temperature window (320-450 • C), insufficient hydrothermal stability and biotoxicity, conventional vanadia catalysts have gradually been replaced by nontoxic metal-based zeolite catalysts, especially Cu-based zeolites with a wide temperature window (200-500 • C) and high hydrothermal stability in NH 3 -SCR [4,5], owing to their unique properties such as high surface areas, considerable acidity and well-defined pore systems with stable structure which can sustain up to 800 • C [6,7]. In addition, due to the high redox activity of Cu species, Cu-based zeolites such as Cu/SSZ-13 [7,8], Cu/SAPO-34 [9,10], Cu/LTA [8,11] and Cu/SSZ-39 [12,13] have become the most used catalysts in NH 3 -SCR, especially in the low temperature range (200-350 • C) [13,14].…”

Section: Introductionmentioning

confidence: 99%

Catalytic Performances of Cu/MCM-22 Zeolites with Different Cu Loadings in NH3-SCR

et al. 2020

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The NH3-SCR activities and hydrothermal stabilities of five xCu/MCM-22 zeolites with different Cu loadings (x = 2–10 wt%) prepared by incipient wetness impregnation method were systematically investigated. The physicochemical properties of xCu/MCM-22 zeolites were analyzed by XRD, nitrogen physisorption, ICP-AES, SEM, NH3-TPD, UV-vis, H2-TPR and XPS experiments. The Cu species existing in xCu/MCM-22 are mainly isolated Cu2+, CuOx and unreducible copper species. The concentrations of both isolated Cu2+ and CuOx species in xCu/MCM-22 increase with Cu contents, but the increment of CuOx species is more distinct, especially in high Cu loadings (>4 wt%). NH3-SCR experimental results demonstrated that the activity of xCu/MCM-22 is sensitive to Cu content at low Cu loadings (≤4 wt%). When the Cu loading exceeds 4 wt%, the NH3-SCR activity of xCu/MCM-22 is irrelevant to Cu content due to the severe pore blockage effects caused by aggregated CuOx species. Among the five xCu/MCM-22 zeolites, 4Cu/MCM-22 with moderate Cu content has the best NH3-SCR performance, which displays higher than 80% NOx conversions in a wide temperature window (160–430 °C). Furthermore, the hydrothermal aging experiments (xCu/MCM-22 was treated at 750 °C for 10 h under 10% water vapor atmosphere) illustrated that all the xCu/MCM-22 zeolites exhibit high hydrothermal stability in NH3-SCR reactions.

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Unexpected Low Temperature Activity with Low N₂O Emission of Stabilized Al‐rich Zeolite Beta for Selective Catalytic Reduction of NO_x

Yu,

Iyoki,

Elangovan

et al. 2023

Chemistry A European J

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The low temperature activity of Fe‐loaded zeolites as selective catalytic reduction of NOx by NH3 (NH3‐SCR) catalysts is a critical drawback for practical application. Here, we found unexpected improvement of low temperature activity by our proposed post‐synthetic treatment. An Al‐rich zeolite beta (Si/Al=5) is employed as the catalyst support, and the parent sample is dealuminated for higher hydrothermal stability, followed by the liquid‐mediated stabilization treatment and impregnation. It is found that stabilized samples feature excellent low temperature activity and high N2 selectivity even for a long‐term operation, along with the ability to maintain high NOx conversion after aging. The improved SCR activity should be attributed to abundant acid sites in Al‐rich framework and better stabilization of monomeric iron species after the stabilization treatment. Furthermore, the low yield of side product N2O is probably due to the absence of the generation of NH4NO3 during NH3‐SCR catalyzed by Fe‐loaded zeolites.

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On the Mechanism of Ammonia SCR over Cu- and Fe-Containing Zeolite Catalysts

Cited by 10 publications

References 95 publications

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Catalytic Performances of Cu/MCM-22 Zeolites with Different Cu Loadings in NH3-SCR

Unexpected Low Temperature Activity with Low N₂O Emission of Stabilized Al‐rich Zeolite Beta for Selective Catalytic Reduction of NO_x

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On the Mechanism of Ammonia SCR over Cu- and Fe-Containing Zeolite Catalysts

Cited by 10 publications

References 95 publications

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Computational Insights into the Mechanism of the Selective Catalytic Reduction of NOx: Fe- Versus Cu-Doped Zeolite Catalysts

Catalytic Performances of Cu/MCM-22 Zeolites with Different Cu Loadings in NH3-SCR

Unexpected Low Temperature Activity with Low N2O Emission of Stabilized Al‐rich Zeolite Beta for Selective Catalytic Reduction of NOx

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Unexpected Low Temperature Activity with Low N₂O Emission of Stabilized Al‐rich Zeolite Beta for Selective Catalytic Reduction of NO_x