<i>In situ</i> DRIFT studies on N<sub>2</sub>O formation over Cu-functionalized zeolites during ammonia-SCR

Isapour, Ghodsieh; Wang, Aiyong; Han, Joonsoo; Feng, Yingxin; Grönbeck, Henrik; Creaser, Derek; Olsson, Louise; Skoglundh, Magnus; Härelind, Hanna

doi:10.1039/d2cy00247g

Cited by 7 publications

(9 citation statements)

References 72 publications

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“…Overall, the bands below 1580 cm −1 correspond to the N-O stretching vibrations of surface nitrate species [43]. In contrast, despite that, in the spectrum of the experiment with NO 2 /He, peaks at 1630 and 1600 cm −1 can be identified, the intensity of the bands below 1580 cm −1 are much lower.…”

Section: Drifts Measurementsmentioning

confidence: 81%

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

et al. 2023

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NO2 is one of the main greenhouse gases, which is mainly generated by the combustion of fossil fuels. In addition to its contribution to global warming, this gas is also directly dangerous to humans. The present work reports the structural and gas sensing properties of the CaCu3Ti4O12 compound prepared by the sol-gel technique. Rietveld refinement confirmed the formation of the pseudo-cubic CaCu3Ti4O12 compound, with less than 4 wt% of the secondary phases. The microstructural and elemental composition analysis were carried out using scanning electron microscopy and X-ray energy dispersive spectroscopy, respectively, while the elemental oxidation states of the samples were determined by X-ray photoelectron spectroscopy. The gas sensing response of the samples was performed for different concentrations of NO2, H2, CO, C2H2 and C2H4 at temperatures between 100 and 300 °C. The materials exhibited selectivity for NO2, showing a greater sensor signal at 250 °C, which was correlated with the highest concentration of nitrite and nitrate species on the CCTO surface using DRIFT spectroscopy.

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Section: Drifts Measurementsmentioning

confidence: 81%

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

et al. 2023

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“…The peak of NO 2 (1621 cm –1 ) decreased rapidly after NH 3 was introduced and the peak (3573 cm –1 ) generated by the N–H stretching vibration and the peaks (923 and 917 cm –1 ) generated by gaseous or weakly adsorbed NH 3 , indicating that NO 2 has been consumed by adsorbed NH 3 . The peak of free nitrate was basically unchanged, the peaks of monodentate nitrite and bridging nitrate shifted, and the NO – species (1133 cm –1 ) and bidentate nitrate (1012 cm –1 ) disappeared and then were replaced by adsorbed NH 3 (1205 cm –1 ). − Thus, nitrogen dioxide, bridging nitrate, and monodentate nitrite are deemed to be the main active species, which can easily react with the adsorbed NH 3 species to generate N 2 and H 2 O, and the L-H mechanism occurs during the reaction. Therefore, both the E-R and L-H reaction mechanisms take place over Mn-BTC-335 °C during the SCR de-NO x reaction.…”

Section: Resultsmentioning

confidence: 98%

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

et al. 2023

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NO x emission is a major environmental issue, and selective catalytic reduction (SCR) is the most effective method for the conversion of NO x to harmless N2 and H2O. Manganese oxide has excellent low-temperature (LT) denitration (de-NO x ) activity, but poor SO2 tolerance hinders its application. Herein, we report an interesting SCR catalyst, quasi-metal–organic-framework (MOF) nanorod containing manganese (quasi-Mn-BTC) with abundant oxygen vacancies (Vo), unique hierarchical porous structure, and half-metallic property, which successfully overcome the disadvantage of poor SO2 tolerance of Mn-based catalysts. The NO x conversion over the Mn-BTC-335 °C only drops by 7% until SO2 is gradually increased to 200 ppm from 100 ppm for 36 h. Furthermore, the quasi-Mn-BTC presents excellent LT de-NO x performance with above 90% NO x conversion between 120 and 330 °C at a gas hourly space velocity of 36,000 h–1. Experimental and theoretical calculations confirm that the difficult electron transport between SO2 and active sites can prevent it from competing adsorption with NH3 and NO. Furthermore, the low degree of d–p hybridization and unstable p–p hybridization of SO2 on the active sites make it difficult for adsorption and oxidation; thus, the weak adsorption of SO2 can prevent it from sulfation on the active sites, ensuring Mn-BTC-335 °C excellent SO2 tolerance. Additionally, the half-metallicity property, the extraordinary d–sp hybridization, and the high degree of s–p hybridization cause strong bonding and the delocalization of electrons that promote the charge transfer and adsorbed ion diffusion for NH3 and NO adsorption, promoting the LT de-NO x performance. In situ diffuse reflectance infrared Fourier transform spectra and density functional theory calculation further reveal that the de-NO x reaction over Mn-BTC-335 °C follows both Eley–Rideal (E-R) and Langmuir–Hinshelwood (L-H) mechanisms. The “standard reaction” is more likely to occur in the E-R reaction, while the “fast reaction” is prone to occur in the L-H pathway, and HNNOH and NH3NO2 are the two key intermediates. This work provides a viable strategy for augmenting the LT de-NO x and SO2 tolerance of Mn-based catalysts, which may pave a new way in the application of MOFs in de-NO x , and the complete reaction mechanism provides a solid basis for future improvements of the LT NH3-SCR de-NO x reaction.

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“…Therefore, they were denoted as M-NNO species adsorbed on surface cation and further desorbed to gaseous N 2 O. 16,24,39,40 The peak of 2237 cm −1 was ascribed to the vibration of the N�N bond of adsorbed intermediate, 41 possibly NH 2 NO ads , originating from the reaction of adsorbed NO + and NH 3 . 42,43 DRIFTS results suggested that the NH 3 −SCO over Ag HDs/Al 2 O 3 follows the internal NH 3 −SCR (i-SCR) reaction pathways, 44 where NO + is the key intermediate.…”

Section: Resultsmentioning

confidence: 99%

“…It was reported that double peaks at 2237 and 2210 cm –1 appeared when N 2 O adsorbed on the catalyst surface or NH 3 oxidation occurred at high temperatures. Therefore, they were denoted as M-NNO species adsorbed on surface cation and further desorbed to gaseous N 2 O. ,,, The peak of 2237 cm –1 was ascribed to the vibration of the NN bond of adsorbed intermediate, possibly NH 2 NO ads , originating from the reaction of adsorbed NO + and NH 3 . , …”

Section: Resultsmentioning

confidence: 99%

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N₂ Selectivity

Wang,

Murayama,

Ishida

et al. 2024

ACS Appl. Mater. Interfaces

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Supported particulate noble-metal catalysts are widely used in industrial catalytic reactions. However, these metal species, whether in the form of nanoparticles or highly dispersed entities, tend to aggregate during reactions, leading to a reduced activity or selectivity. Addressing the frequent necessity for the replacement of industrial catalysts remains a significant challenge. Herein, we demonstrate the feasibility of the 'regenerable catalytic system' exemplified by selective catalytic oxidation of ammonia (NH 3 − SCO) employing Ag/Al 2 O 3 catalysts. Results demonstrate that our highly dispersed Ag catalyst (Ag HD) maintains >90% N 2 selectivity at 80% NH 3 conversion and >80% N 2 selectivity at 100% NH 3 conversion after enduring 5 cycles of reducible aggregation and oxidative dispersion. Moreover, it consistently upholds over 98% N 2 selectivity at 100% NH 3 conversion after 10 cycles of Ar treatment. During the aggregation−dispersion process, the Ag HD catalyst intentionally aggregated into Ag nanoparticles (Ag NP) after H 2 reduction and exhibited remarkable regenerable capabilities, returning to the Ag HD state after calcination in the air. This structural evolution was characterized through in situ transmission electron microscopy, atomically resolved high-angle annular dark-field scanning transmission electron microscopy, and X-ray absorption spectroscopy, revealing the on-site oxidative dispersion of Ag NP. Additionally, in situ diffuse reflectance infrared Fourier transform spectroscopy provided insights into the exceptional N 2 selectivity on Ag HD catalysts, elucidating the critical role of NO + intermediates. Our findings suggest a sustainable and cost-effective solution for various industry applications.

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In situ DRIFT studies on N₂O formation over Cu-functionalized zeolites during ammonia-SCR

Abstract: The influence of the zeolite framework structure on the formation of undesired by-products during ammonia-SCR of NOx is studied for three different copper-functionalized zeolite samples, namely Cu-SSZ-13 (CHA), Cu-ZSM-5 (MFI)...

Cited by 7 publications

References 72 publications

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N₂ Selectivity

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In situ DRIFT studies on N2O formation over Cu-functionalized zeolites during ammonia-SCR

Abstract: The influence of the zeolite framework structure on the formation of undesired by-products during ammonia-SCR of NOx is studied for three different copper-functionalized zeolite samples, namely Cu-SSZ-13 (CHA), Cu-ZSM-5 (MFI)...

Cited by 7 publications

References 72 publications

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

Selective NO2 Detection of CaCu3Ti4O12 Ceramic Prepared by the Sol-Gel Technique and DRIFT Measurements to Elucidate the Gas Sensing Mechanism

Insight into the Origin of Excellent SO2 Tolerance and de-NOx Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N2 Selectivity

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In situ DRIFT studies on N₂O formation over Cu-functionalized zeolites during ammonia-SCR

Insight into the Origin of Excellent SO₂ Tolerance and de-NO_x Performance of quasi-Mn-BTC in the Low-Temperature Catalytic Reduction of Nitrogen Oxide

The Development of the Regenerable Catalytic System in Selective Catalytic Oxidation of Ammonia with High N₂ Selectivity