Time-resolved observation of V2O5/TiO2 in NH3-SCR reveals the equivalence of Brønsted and Lewis acid sites

Song, In Kyu; Lee, Hwangho; Jeon, Se Won; Kim, Tae-Jin; Kim, Do Heui

doi:10.1039/d0cc06006b

Cited by 24 publications

(22 citation statements)

References 31 publications

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“…Besides, simple N 2 /Ar/NH 3 thermal treatment was proved to eliminate sulfates without affecting the surface area and redox characteristics over specific CeO 2 and Fe 2 O 3 catalysts. The synergistic catalysis between acid and metal sites and the interfacial effect caused by sulfates were not fully understood. Recently, time-resolved in situ DRIFTS observations have been demonstrated to study the migration and transformation of NH 3 species over V–OH and VO sites on V 2 O 5 -based catalysts . Additionally, control of the proximity of acid and metal sites was used to explore the interfacial effect.…”

Section: Discussionmentioning

confidence: 99%

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

Xie

et al. 2021

ACS Catal.

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Sulfur poisoning is a common problem causing catalyst deactivation during the industrial catalytic process. However, for selective catalytic reduction of NO x with ammonia (NH3-SCR) technology, the formation of sulfate species from SO2 in flue gas could remarkably improve NH3-SCR performance by adjusting the surface acidity of the metal oxides. This Review systematically summarizes recent advances concerning sulfur promotion roles of metal oxide catalysts for the NH3-SCR reaction. First, the effects of sulfation treatment on the properties of sulfate species are discussed and compared in detail. The synthesis procedures and the critical parameters of gas-phase and liquid-phase methods are introduced. Second, it is tentative to conclude how the sulfation treatments coordinate acid and metal sites and propose a comprehensive overview of the reaction mechanisms over sulfated catalysts. Subsequently, it summarizes the effective methods to construct appropriate acidity and reducibility of sulfated metal oxides by exposing crystal planes and creating specific structures, including CeO2-, Fe2O3-, V2O5-, and CuO-based catalysts. The corresponding reaction pathways are also deliberated over specific catalysts. Finally, current scientific issues and prospects of sulfated catalysts are put forward, and other acidification methods are supposed to improve the surface acidity effectively. For future NH3-SCR technology, the experimental and mechanistic discussions in this Review will be beneficial to understand reaction chemistry and design highly efficient NH3-SCR catalysts.

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Section: Discussionmentioning

confidence: 99%

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

Xie

et al. 2021

ACS Catal.

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“…The transient reaction of B−NH 3 with NO + NO 2 (Figure 6, middle) resulted in a higher rate of N 2 formation than under NO 2 and the following changes in the IR features. After an induction period of 600 s, the height of the NH 4 + band (1450 cm −1 ) decreased with time, accompanied by a pseudo-steadystate 51 formation of N 2 (600−1600 s). Then the N 2 formation rate decreased with further consumption of B−NH 3 .…”

Section: Thementioning

confidence: 99%

In Situ/Operando IR and Theoretical Studies on the Mechanism of NH₃–SCR of NO/NO₂ over H–CHA Zeolites

et al. 2021

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The mechanism of selective catalytic reduction (SCR) of a NO/NO2 mixture by NH3 (fast SCR) over H–CHA zeolites was revealed by in situ/operando IR spectroscopy and DFT calculations. Kinetic results show that the rate of fast SCR is 2 orders of magnitude higher than that for standard SCR by H–CHA. Combined experimental and computational results show a complete mechanism of fast SCR initiated by the disproportionation of NO2 into adsorbed NO+ and NO3 – species. NO+ reacts with NH3 to produce N2 and H2O, while NO3 – reacts with NH3 on Brønsted acid sites (NH4 +) to yield NH4NO3. In the presence of NO, NH4NO3 is reduced by NO to afford NH4NO2, which then decomposes into N2 and H2O, while thermal decomposition of NH4NO3 yields N2O and H2O in the absence of NO. The activation and reaction energies for all of the elementary steps are computed by DFT, which support the experimentally proposed mechanism of fast SCR over H–CHA. During the SCR process where NO2 participated, the Brønsted acid sites of the zeolite play an essential catalytic role in key elementary reactions.

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“…In contrast, the peak between ∼1500 and 1380 cm −1 characterized to be NH 4 + adsorbed on Brønsted sites gradually increased. 41 According to the decomposition equation of ABS: NH 4 HSO 4 → 1/3 NH 3 + 1/3 N 2 + SO 2 + 2 H 2 O, 21 one third of the NH 4 + species are eventually released in the form of NH 3 , and the formed NH 3 will be adsorbed on the regenerated Brønsted sites, explaining the increase of signal between ∼1500 and 1380 cm −1 in Fig. 5b.…”

Section: Resultsmentioning

confidence: 94%

Single Mo atoms paired with neighbouring Ti atoms catalytically decompose ammonium bisulfate formed in low-temperature SCR

et al. 2022

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Time-resolved observation of V₂O₅/TiO₂ in NH₃-SCR reveals the equivalence of Brønsted and Lewis acid sites

Abstract: Reaction rates of Lewis-NH3 and Brønsted-NH3 species were measured to be equivalent in the selective catalytic reaction over V2O5/TiO2 catalyst.

Cited by 24 publications

References 31 publications

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

In Situ/Operando IR and Theoretical Studies on the Mechanism of NH₃–SCR of NO/NO₂ over H–CHA Zeolites

Single Mo atoms paired with neighbouring Ti atoms catalytically decompose ammonium bisulfate formed in low-temperature SCR

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Time-resolved observation of V2O5/TiO2 in NH3-SCR reveals the equivalence of Brønsted and Lewis acid sites

Abstract: Reaction rates of Lewis-NH3 and Brønsted-NH3 species were measured to be equivalent in the selective catalytic reaction over V2O5/TiO2 catalyst.

Cited by 24 publications

References 31 publications

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NOx Emission Control

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NOx Emission Control

In Situ/Operando IR and Theoretical Studies on the Mechanism of NH3–SCR of NO/NO2 over H–CHA Zeolites

Single Mo atoms paired with neighbouring Ti atoms catalytically decompose ammonium bisulfate formed in low-temperature SCR

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Time-resolved observation of V₂O₅/TiO₂ in NH₃-SCR reveals the equivalence of Brønsted and Lewis acid sites

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

Review of Sulfur Promotion Effects on Metal Oxide Catalysts for NO_x Emission Control

In Situ/Operando IR and Theoretical Studies on the Mechanism of NH₃–SCR of NO/NO₂ over H–CHA Zeolites