Cu/SSZ-13 and Cu/SAPO-34 catalysts for deNOx in diesel exhaust: Current status, challenges, and future perspectives

Zhang, Shoute; Pang, Lei; Chen, Zhe; Ming, Shujun; Dong, Yahao; Liu, Qian; Liu, Peng; Cai, Weiquan; Li, Tao

doi:10.1016/j.apcata.2020.117855

Cited by 63 publications

(35 citation statements)

References 199 publications

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“…Cu-exchanged chabazite (Cu-CHA) has been commercialized as a catalyst for the selective catalytic reduction (SCR) of nitrogen oxides (NO x ) by NH 3 (NH 3 –SCR) in diesel emission control systems. − Experimental and computational studies in the last decade have been focused on the mechanism of NO reduction by NH 3 in the presence of oxygen as the so-called standard SCR − …”

Section: Introductionmentioning

confidence: 99%

“…32−34 Below 150 °C, NO 2 formed in the DOC upstream of the SCR converter can react with NH 3 , leading to the accumulation of ammonium nitrate (NH 4 NO 3 ) in the zeolite pores and hence decreasing the NO x conversion. 33 Additionally, NH 4 undesirable byproduct N 2 O. 35−40 Based on this background, fundamental understanding of the elementary reaction steps involving NO, NO 2 , and NH 3 in Cu-CHA below 150 °C is indispensable for designing a next generation SCR system workable at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

et al. 2021

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In situ/operando infrared (IR) spectroscopy, kinetics, and density functional theory (DFT) calculations were combined to propose a comprehensive mechanistic model of the selective catalytic reduction (SCR) of the NO/NO 2 mixture by NH 3 , the so-called fast SCR, over Cu-CHA zeolites. Steady-state kinetics for standard and fast SCR over H-CHA and Cu-CHA show that the promotional effect of NO 2 on SCR is less significant for Cu-CHA than H-CHA, suggesting that the Brønsted acid site (BAS;in fast SCR chemistry. In situ IR experiments show that NO 2 disproportionates on Cu-CHA to NO + on the cation-exchange site (NO + O Z − ) of CHA and NO 3 − on Cu II sites. Operando IR studies under transient or temperature-programmed surface reaction conditions indicate that the NO + O Z − intermediate is reduced by NH 3 to yield N 2 below 200 °C, while NO 3 − on the Cu II site is rather stable under NH 3 and is reduced by NO to afford NO + O Z − . BASs, rather than Cu sites, promote the side reactions via ammonium nitrate (NH 4 NO 3 ). The dual-site (Cu II and BAS sites) catalytic mechanism of fast SCR was verified by DFT calculations. First, two NO 2 molecules are converted to a nitrous acid (HONO) intermediate and NO 3 − on the Cu II site, which is then reduced by NO to afford HONO and regenerate the Cu II site. HONO reacts with the BAS to afford NO + O Z − , which reacts with NH 3 to produce N 2 and H 2 O, via nitrosamide (NH 2 NO), along with the regeneration of the BAS.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

et al. 2021

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“…The CHA zeolite structure and ion-exchanged Cu are stable up to 750 • C and start deteriorating at 800 • C. With BEA-and ZSM-5-based Cu zeolites, SCR activity is severely reduced after ageing at 650 • C due to the collapse of the zeolite structure accompanied by the formation of CuAl 2 O 4 spinels and extra framework CuO. Cu-SAPO-34 and Cu-SSZ-13 can achieve higher NO x conversion rates, generally in the order SSZ-13 = SAPO-34 > ZSM-5 > BEA [29][30][31][32]. Extensive spectroscopic and reactivity characterizations of the Cu-CHA SCR catalysts have demonstrated the importance of small zeolite pores, especially for SCRoF applications where high hydrothermal stability is of paramount importance.…”

Section: Scr Catalysts For Scrofmentioning

confidence: 99%

Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems

2021

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The abatement of the pollutants deriving from diesel engines in the vehicle sector still represents an interesting scientific and technological challenge due to increasingly limiting regulations. Meeting the stringent limits of NOx and soot emissions requires a catalytic system with great complexity, size of units, and number of units, as well as increased fuel consumption. Thus, an after-treatment device for a diesel vehicle requires the use of an integrated catalyst technology for a reduction in the individual emissions of exhaust gas. The representative technologies devoted to the reduction of NOx under lean-burn operation conditions are selective catalytic reduction (SCR) and the lean NOx trap (LNT), while soot removal is mainly performed by filters (DPF). These devices are normally used in sequence, or a combination of them has been proposed to overcome the drawbacks of the individual devices. This review summarizes the current state of NOx and soot abatement strategies. The main focus of this review is on combined technologies for NOx removal (i.e., LNT–SCR) and for the simultaneous removal of NOx and soot, like SCR-on-Filter (SCRoF), in series LNT/DPF and SCR/DPF, and LNT/DPF and SCR/DPF hybrid systems.

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“…9–11 Typical examples of zeolites are SAPO-34 and SSZ-13, which have been successfully industrialized and applied for the above catalytic processes. Recent reviews about the synthesis and application of SAPO-34 and SSZ-13 zeolites have been conducted by researchers, 12–14 but it is rare to briefly summarize the synthesis and application of novel small-pore zeolite structures with good catalytic properties.…”

Section: Introductionmentioning

confidence: 99%

Advances in the synthesis and application of the SSZ-39 zeolite

Zhu

et al. 2022

Inorg. Chem. Front.

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Cu/SSZ-13 and Cu/SAPO-34 catalysts for deNOx in diesel exhaust: Current status, challenges, and future perspectives

Cited by 63 publications

References 199 publications

Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems

Advances in the synthesis and application of the SSZ-39 zeolite

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Cu/SSZ-13 and Cu/SAPO-34 catalysts for deNOx in diesel exhaust: Current status, challenges, and future perspectives

Cited by 63 publications

References 199 publications

Mechanism of NH3–Selective Catalytic Reduction (SCR) of NO/NO2 (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

Mechanism of NH3–Selective Catalytic Reduction (SCR) of NO/NO2 (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

Aftertreatment Technologies for Diesel Engines: An Overview of the Combined Systems

Advances in the synthesis and application of the SSZ-39 zeolite

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Product

Resources

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Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory

Mechanism of NH₃–Selective Catalytic Reduction (SCR) of NO/NO₂ (Fast SCR) over Cu-CHA Zeolites Studied by In Situ/Operando Infrared Spectroscopy and Density Functional Theory