N2O Formation during NH3-SCR over Different Zeolite Frameworks: Effect of Framework Structure, Copper Species, and Water

The cerium and/or zirconium-doped Cu/ZSM-5 catalysts (CuCexZr1−xOy/ZSM-5) were prepared by ion exchange and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction by hydrogen (H2-TPR). Activities of the catalysts obtained on the selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia were measured using temperature programmed reactions. Among all the catalysts tested, the CuCe0.75Zr0.25Oy/ZSM-5 catalyst presented the highest catalytic activity for the removal of NO, corresponding to the broadest active window of 175–468 °C. The cerium and zirconium addition enhanced the activity of catalysts, and the cerium-rich catalysts exhibited more excellent SCR activities as compared to the zirconium-rich catalysts. XRD and TEM results indicated that zirconium additions improved the copper dispersion and prevented copper crystallization. According to XPS and H2-TPR analysis, copper species were enriched on the ZSM-5 grain surfaces, and part of the copper ions were incorporated into the zirconium and/or cerium lattice. The strong interaction between copper species and cerium/zirconium improved the redox abilities of catalysts. Furthermore, the introduction of zirconium abates N2O formation in the tested temperature range.

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Understanding the nature of NH3-coordinated active sites and the complete reaction schemes for NH3-SCR using Cu-SAPO-34 catalysts

Physical Chemistry Chemical Physics ◽

10.1039/d0cp06285e ◽

2021 ◽

Author(s):

Guangpeng Yang ◽

Jingyu Ran ◽

Xuesen Du ◽

Xiangmin Wang ◽

Zhilin Ran ◽

...

Keyword(s):

Low Temperature ◽

Active Sites ◽

Zeolite Catalysts ◽

Copper Species ◽

Nh3 Scr ◽

Complete Reaction ◽

Catalytic Capacity ◽

Reaction Schemes

Cu-SAPO-34 zeolite catalysts show excellent NH3-SCR performance at low temperature, which is due to the catalytic capacity of copper species.

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Insights into the impact of lanthanum on hydrothermal-induced migration and transformation of copper species in Cu/SAPO-34 catalyst for NH3-SCR

Molecular Catalysis ◽

10.1016/j.mcat.2021.111914 ◽

2021 ◽

Vol 515 ◽

pp. 111914

Author(s):

Huimin Wang ◽

Wei Li ◽

Siyuan Xu ◽

Mo Liu ◽

Jiming Hao ◽

...

Keyword(s):

Copper Species ◽

Nh3 Scr ◽

The Impact

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N2O Formation Pathways over Zeolite-Supported Cu and Fe Catalysts in NH3-SCR

Energy & Fuels ◽

10.1021/acs.energyfuels.7b03405 ◽

2018 ◽

Vol 32 (2) ◽

pp. 2170-2182 ◽

Cited By ~ 21

Author(s):

Dong Zhang ◽

Ralph T. Yang

Keyword(s):

N2o Formation ◽

Nh3 Scr ◽

Fe Catalysts

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The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

Catalysts ◽

10.3390/catal9090741 ◽

2019 ◽

Vol 9 (9) ◽

pp. 741 ◽

Cited By ~ 1

Author(s):

Wang ◽

Hou ◽

Yan ◽

Zhang ◽

Wang ◽

...

Keyword(s):

Copper Sulfate ◽

Active Sites ◽

Catalytic Reduction ◽

Copper Ions ◽

Acid Resistance ◽

Temperature Program Reduction ◽

Copper Species ◽

Nh3 Scr ◽

Scr Catalysts

To reveal the role of SO3 poisoning in Cu/SSZ-13 NH3-SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO3 flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO3/SOx. The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO3/SOx ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H2-TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO3/SOx ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH3-SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NOx elimination, especially when SO3 exists.

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Ferrierite and Its Delaminated and Silica-Intercalated Forms Modified with Copper as Effective Catalysts for NH3-SCR Process

Catalysts ◽

10.3390/catal10070734 ◽

2020 ◽

Vol 10 (7) ◽

pp. 734 ◽

Cited By ~ 4

Author(s):

Aneta Święs ◽

Andrzej Kowalczyk ◽

Małgorzata Rutkowska ◽

Urbano Díaz ◽

Antonio E. Palomares ◽

...

Keyword(s):

Low Temperature ◽

Ammonia Oxidation ◽

Catalytic Reduction ◽

Surface Acidity ◽

Side Reaction ◽

Copper Species ◽

Nh3 Scr ◽

Scr Catalysts ◽

Catalytically Active ◽

Fast Scr

The main goal of the study was the development of effective catalysts for the low-temperature selective catalytic reduction of NO with ammonia (NH3-SCR), based on ferrierite (FER) and its delaminated (ITQ-6) and silica-intercalated (ITQ-36) forms modified with copper. The copper exchange zeolitic samples, with the intended framework Si/Al ratio of 30 and 50, were synthetized and characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low-temperature N2 adsorption), form and aggregation of deposited copper species (UV-vis-DRS), surface acidity (NH3-TPD) and reducibility (H2-TPR). The samples of the Cu-ITQ-6 and Cu-ITQ-36 series were found to be significantly more active NH3-SCR catalysts compared to Cu-FER. The activity of these catalysts in low-temperature NH3-SCR was assigned to the significant contribution of highly dispersed copper species (monomeric cations and small oligomeric species) catalytically active in the oxidation of NO to NO2, which is necessary for fast-SCR. The zeolitic catalysts, with the higher framework alumina content, were more effective in high-temperature NH3-SCR due to their limited catalytic activity in the side reaction of ammonia oxidation.

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Spherical Al-MCM-41 Doped with Copper by Modified TIE Method as Effective Catalyst for Low-Temperature NH3-SCR

Molecules ◽

10.3390/molecules26061807 ◽

2021 ◽

Vol 26 (6) ◽

pp. 1807

Author(s):

Aleksandra Jankowska ◽

Andrzej Kowalczyk ◽

Małgorzata Rutkowska ◽

Marek Michalik ◽

Lucjan Chmielarz

Keyword(s):

Low Temperature ◽

Ion Exchange ◽

Ammonia Oxidation ◽

Surface Acidity ◽

Ammonia Solution ◽

Exchange Method ◽

Copper Species ◽

Nh3 Scr ◽

Side Process ◽

Mcm 41

Aluminum containing silica spherical MCM-41 was synthesized and modified with copper by the template ion-exchange method (TIE) and its modified version, including treatment of the samples with ammonia solution directly after template ion-exchange (TIE-NH3). The obtained samples were characterized with respect to their chemical composition (ICP-OES), structure (XRD), texture (low temperature N2 sorption), morphology (SEM-EDS), form and aggregation of deposited copper species (UV-vis DRS), reducibility of copper species (H2-TPR), and surface acidity (NH3-TPD). The deposition of copper by the TIE-NH3 method resulted in much better dispersion of this metal on the MCM-41 surface comparing to copper introduced by TIE method. It was shown that such highly dispersed copper species, mainly monomeric Cu2+ cations, deposited on aluminum containing silica spheres of MCM-41, are significantly more catalytically effective in the NH3-SCR process than analogous catalysts containing aggregated copper oxide species. The catalysts obtained by the TIE-NH3 method effectively operated in much broader temperature and were less active in the side process of direct ammonia oxidation by oxygen.

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The Role of H+- and Cu+-Sites for N2O Formation during NH3-SCR over Cu-CHA

The Journal of Physical Chemistry C ◽

10.1021/acs.jpcc.0c11008 ◽

2021 ◽

Vol 125 (8) ◽

pp. 4595-4601

Author(s):

Yingxin Feng ◽

Ton V. W. Janssens ◽

Peter N. R. Vennestrøm ◽

Jonas Jansson ◽

Magnus Skoglundh ◽

...

Keyword(s):

N2o Formation ◽

Nh3 Scr

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