NOx Selective Catalytic Reduction (NOx-SCR) by Urea: Evidence of the Reactivity of HNCO, Including a Specific Reaction Pathway for NOx Reduction Involving NO + NO2

Seneque, Mickael; Can, Fabien; Duprez, Daniel; Courtois, Xavier

doi:10.1021/acscatal.6b00785

Cited by 59 publications

(29 citation statements)

References 17 publications

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“…Consequently, the GHSV was of 180,000 h -1 (100 L h -1 gcata -1 ). The experimental setup has been previously described in [36,37]. The gas mixture was adjusted using Bronkhorst mass-flow controllers, except for ethanol, acetaldehyde and water which were vaporized into the reactor via a micro-nozzle (The Lee Company (Ønozzle= 50 µm)) placed into the quartz reactor in a heated zone at 200°C.…”

Section: Catalytic Testsmentioning

confidence: 99%

Selective catalytic reduction of NO at low temperature using a (ethanol+ammonia) mixture over a Ag/Al2O3 + WO3/Cex-ZryO2 dual-bed catalytic system: Reactivity insight of WO3/Cex-ZryO2

2020

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The Selective Catalytic Reduction (SCR) is one of the most efficient process for NOx removal from Diesel exhaust gas. However, the urea/NH3-SCR process implemented in recent vehicles still suffers from a poor activity in the low temperature range (T < 250°C). One main reason is its dependency against the NO2/NOx ratio, limiting the expected fast-SCR reaction in this temperature range. Recently, we shown that the addition of ethanol to ammonia led to a significant increase of the activity of a Ag/Al2O3 catalyst in this low temperature range. Moreover, in a dual-bed configuration (Ag/Al2O3+WO3/Cex-ZryO2), a remarkable improvement was achieved at low temperature using only NO as NOx. The present work aims to highlight the DeNOx chemistry encountered over the WO3/Cex-ZryO2 catalyst in a bifunctional (EtOH+NH3) mixture. In addition to the fact that this process takes advantage of the low temperature NO2 formation over the upstream Ag/Al2O3 catalyst, this work also puts in evidenced unexpected interactions between NO2 and CH3CHO (resulting from ethanol oxidation over Ag/Al2O3) thus leading to NO emission.

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Section: Catalytic Testsmentioning

confidence: 99%

Selective catalytic reduction of NO at low temperature using a (ethanol+ammonia) mixture over a Ag/Al2O3 + WO3/Cex-ZryO2 dual-bed catalytic system: Reactivity insight of WO3/Cex-ZryO2

2020

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“…Urea-containing creams are used as topical dermatological products to promote skin hydration 3 , and large amounts of urea are used for the synthesis of barbiturates 4 . Since NH 3 produced by the hydrolysis of urea can react with nitrogen oxides (NO x ) to produce nitrogen, an increasingly important application of urea is to reduce NO x impurities in exhaust gases from diesel and lean-burn natural gas engines 5 . Therefore, maintaining a sustainable and efficient urea industry is of great importance for the development of human society.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical synthesis of urea on MBenes

et al. 2021

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Urea is an important raw material in the chemical industry and is widely used as a nitrogen source in chemical fertilizers. The current industrial urea synthesis not only requires harsh reaction conditions, but also consumes most of the NH3 obtained through artificial synthesis. The conversion of N2 and CO2 into urea through electrochemical reactions under ambient conditions represents a novel green urea synthesis method. However, the large-scale promotion of this method is limited by the lack of suitable electrocatalysts. Here, by means of density functional theory computations, we systematically study the catalytic activity of three experimentally available two-dimensional metal borides (MBenes), Mo2B2, Ti2B2, and Cr2B2 toward simultaneous electrocatalytic coupling of N2 and CO2 to produce urea under ambient conditions. According to our results, these three MBenes not only have superior intrinsic basal activity for urea formation, with limiting potentials ranging from −0.49 to −0.65 eV, but also can significantly suppress the competitive reaction of N2 reduction to NH3. In particular, 2D Mo2B2 and Cr2B2 possess superior capacity to suppress surface oxidation and self-corrosion under electrochemical reaction conditions, rendering them relatively promising electrocatalysts for urea production. Our work paves the way for the electrochemical synthesis of urea.

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“…The exhaust line was not equipped with a clean-up catalyst (CUC) to oxidise excessive ammonia, and therefore, sudden release of NH 3 was noted with the gas-temperature increase. The NH 3 storage capacity of an SCR catalyst is inversely proportional to its temperature, and therefore, the greater the temperature the less NH 3 can be stored inside the catalyst [20][21][22]. The NH 3 concentration measured downstream of the SCR was greater for the gaseous urea system for both α = 0.8 and α = 1.0.…”

Section: Relying Onmentioning

confidence: 98%

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

2017

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This work tried to identify the influence of dosing vaporized urea solution in a selective catalytic reduction (SCR) system. In the SCR method, optimising the urea evaporation and mixing properties can significantly improve the NO x conversion efficiency in the catalyst. It can also exert a positive effect on the uniformity of NH 3 concentration distribution across the catalyst face. The concept of an electrically evaporated urea-dosing system was investigated and it was found that urea pre-heating prior to introduction into the exhaust gas is favourable for enhancing NO x removal under steady-state and transient engine operation. In the urea evaporating system the heating chamber was of a cylindrical tube shape and the urea vapour was introduced into the exhaust by means of a Venturi orifice. The concept urea dosing was only a custom-made solution, but proved to be superior to the regular dosing system operating in the liquid phase.

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NOx Selective Catalytic Reduction (NO_x-SCR) by Urea: Evidence of the Reactivity of HNCO, Including a Specific Reaction Pathway for NOx Reduction Involving NO + NO₂

Cited by 59 publications

References 17 publications

Selective catalytic reduction of NO at low temperature using a (ethanol+ammonia) mixture over a Ag/Al2O3 + WO3/Cex-ZryO2 dual-bed catalytic system: Reactivity insight of WO3/Cex-ZryO2

Selective catalytic reduction of NO at low temperature using a (ethanol+ammonia) mixture over a Ag/Al2O3 + WO3/Cex-ZryO2 dual-bed catalytic system: Reactivity insight of WO3/Cex-ZryO2

Electrochemical synthesis of urea on MBenes

Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

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