Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Tsukamoto, Yoshihisa; Fukuma, Takao; Kusaka, Jin

doi:10.4271/2019-24-0150

Cited by 10 publications

(2 citation statements)

References 24 publications

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“…The SCR redox model shown in this work combines recent kinetic, spectroscopic, and computational findings on the mechanism of standard SCR over Cu-SSZ-13. While several kinetic models have previously been developed to represent NH 3 -SCR over small-pore Cu-zeolites, ,− the model proposed in this work represents one of the first of its kind in quantitatively correlating macroscopic observables to intrinsic microscopic descriptions of the Cu-SSZ-13 material surface.…”

Section: Discussionmentioning

confidence: 99%

Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13

et al. 2022

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In this work, a kinetic model is developed for the reduction of CuII sites by NO + NH3 and the reoxidation of NH3-solvated CuI sites by O2 and NO in Cu-SSZ-13. Fourier transform infrared (FTIR) spectroscopy and spatially resolved capillary inlet mass spectrometry (SpaciMS) measurements during transient reactor experiments are utilized to identify the rate parameters associated with NO + NH3 RHC (reduction half-cycle), proposed to occur via two distinct pathways involving adsorbed NH3 and gas-phase NH3. The resulting NO + NH3 RHC model is validated using spatiotemporal N2 measurements covering a wide range of temperatures (200–450 °C) and space velocities (53 000–640 000 h–1). N2O formation is observed and modeled during NO + NH3 RHC, with quantitative validation under standard selective catalytic reduction (SCR) conditions. Experimentally measured enthalpic and entropic changes associated with O2 adsorption on NH3-solvated CuI (ZCu(NH3)2) complexes [KamasamudramK. Kamasamudram, K. Catal. Today2010151212222], along with activation energies estimated computationally for the intercage diffusion of ZCu(NH3)2 complexes [PaolucciC. Paolucci, C. Science2017357898903], are incorporated into a mean field kinetic model for the low-temperature oxidation half-cycle (OHC). Significant NH3 release is observed during the isothermal oxidation of CuI sites, attributed to desorption of NH3 ligands from NH3-solvated CuII dimers (Z2Cu2(NH3)4O2). Reduction of these dimeric complexes leads to the consumption of one NO/CuII, contradicting the expected reduction stoichiometry. Inclusion of a global Arrhenius rate for the NO titration of Z2Cu2(NH3)4O2 complexes provides accurate representations of standard SCR on reduced and oxidized catalysts, predicting transient NO and NH3 consumption between 150 and 250 °C as a function of hydrothermal aging. Deactivation of low-temperature standard SCR by NH3 is observed at high NH3 pressures, modeled via the formation of superoxo amino (ZCu(NH3)3OO*) complexes during NH3 titration of Z2Cu2(NH3)4O2 complexes [NegriC. Negri, C. J. Am. Chem. Soc.20201421588415896]. The redox kinetic model presented here provides a foundational description of active site redox during low-temperature standard SCR, combining the recent kinetic, spectroscopic, and computational findings on the mechanism of standard SCR over Cu-SSZ-13.

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Section: Discussionmentioning

confidence: 99%

Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13

et al. 2022

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“…The common zeolite skeleton configurations include MFI ( Yuan et al, 2016 ), AEI ( Wu et al, 2022 ), BEA ( Lin et al, 2018 ), LTA ( Lin et al, 2021 ), CHA ( Wang et al, 2015 ; Bergmana et al, 2020 ; Sun et al, 2020 ; Zhang et al, 2021a ; Bello et al, 2022 ), AFX ( Li et al, 2022a ), etc. The zeolite SCR catalyst ( Tsukamoto et al, 2019 ) represented by CHA has advantages including good low-temperature activity, a wide active temperature window, high nitrogen selectivity, green environmental protection due to its unique micropore structure, and suitable surface acidity ( Xu et al, 2020 ; Wang et al, 2021 ; Zhang et al, 2022a ). In recent years, in-depth studies have evaluated the formula, performance, and mechanism of an SCR catalyst with single-structure zeolite.…”

Section: Introductionmentioning

confidence: 99%

The investigation of the NH3-SCR performance of a copper-based AEI-CHA intergrown zeolite catalyst

Ren

Wang

et al. 2022

Front. Chem.

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This work prepared an ISAPO-34/SAPO-18 intergrown zeolite using phosphate organoamine as the structure guiding agent. Physical-chemical characterizations by XRD, SEM, TG, and BET showed that the SAPO-34/SAPO-18 presents a cross-stacked cubic block-like microscopic morphology, with characteristic diffusive diffraction peaks at 2θ = 16–18° and 30–33° and a specific surface area of 557 m2 g−1. The series of copper-based catalysts prepared from SAPO-34/SAPO-18 showed a shift of the active temperature window to a lower temperature with increasing copper content. Moreover, the Brønsted acid site decreased significantly due to copper ion exchange and zeolite structure framework damage. Among them, the 1.2 wt% sample showed the widest active temperature window, with a T90 range of 175–435°C. After low-temperature hydrothermal aging treatment, the zeolite structure was eroded and the catalyst activity deteriorated significantly.

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Promotional effect of ion-exchanged K on the low-temperature hydrothermal stability of Cu/SAPO-34 and its synergic application with Fe/Beta catalysts

Wang

et al. 2020

Front. Environ. Sci. Eng.

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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Cited by 10 publications

References 24 publications

Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13

Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13

The investigation of the NH3-SCR performance of a copper-based AEI-CHA intergrown zeolite catalyst

Promotional effect of ion-exchanged K on the low-temperature hydrothermal stability of Cu/SAPO-34 and its synergic application with Fe/Beta catalysts

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Analysis and Modeling of NOx Reduction Based on the Reactivity of Cu Active Sites and Brønsted Acid Sites in a Cu-Chabazite SCR Catalyst

Cited by 10 publications

References 24 publications

Kinetic Model for the Reduction of CuII Sites by NO + NH3 and Reoxidation of NH3-Solvated CuI Sites by O2 and NO in Cu-SSZ-13

Kinetic Model for the Reduction of CuII Sites by NO + NH3 and Reoxidation of NH3-Solvated CuI Sites by O2 and NO in Cu-SSZ-13

The investigation of the NH3-SCR performance of a copper-based AEI-CHA intergrown zeolite catalyst

Promotional effect of ion-exchanged K on the low-temperature hydrothermal stability of Cu/SAPO-34 and its synergic application with Fe/Beta catalysts

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Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13

Kinetic Model for the Reduction of Cu^II Sites by NO + NH₃ and Reoxidation of NH₃-Solvated Cu^I Sites by O₂ and NO in Cu-SSZ-13