New insights on the adsorption, thermal decomposition and reduction of NOx over Pt- and Ba-based catalysts

Castoldi, L.; Matarrese, Roberto; Morandi, Sara; Righini, Laura; Lietti, Luca

doi:10.1016/j.apcatb.2017.10.019

Cited by 46 publications

(24 citation statements)

References 35 publications

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“…H 2 O was also observed as a product, reaching 1300 ppm after 200 s. The amounts of N 2 and H 2 O produced is close to the 1:5 ratio, indicating nitrites/nitrates reduction through reactions (1) and (2). In line with literature no N 2 O was observed under these conditions [18,20,49,50].…”

Section: Activity Studysupporting

confidence: 87%

“…Most of them have compared the catalysts in terms of oxidation and adsorption capacities but not so many papers have been focused on the reduction step of the cycle. Nitrogen selectivity is required, however, in certain conditions or depending on the materials, NH 3 and/or N 2 O are observed, both undesired products that should not be emitted [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

et al. 2018

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NO X reduction in lean-burn gasoline or diesel engines is challenging in the oxidizing environment, and depending on the after-treatment technology, can lead to by-product, such as N 2 O or ammonia, formation. The current study focuses on possible N 2 O formation pathways over NO x storage/reduction (NSR) catalysts. More specifically, NH 3 reactivity with catalyst surface species was investigated over a model Pt-Ba/γ-Al 2 O 3 (1/20/100, w/w) NSR catalyst with and without NO x species stored (nitrites and nitrates). The NH 3 originates from reduction of NO x in the regeneration phase. With NH 3 , two overall reactions can lead to N 2 or N 2 O formation, namely 3NO + 2NH 3 → 5/2 N 2 + 3H 2 O and 4NO + NH 3 → 5/2 N 2 O + 3/2H 2 O. These two are considered for catalyzed reaction between the entering NO and NH 3. Surface nitrite and nitrate reduction reactions leading to N 2 or N 2 O were also evaluated, all as a function of temperature and relative amount of NH 3 in the gas phase. N 2 O was formed in the lower temperature range, and was more significant with lower NH 3 concentrations. At higher temperatures, above 423 K, for NH 3 concentrations higher than stoichiometric, only N 2 was produced. In comparing the results from the samples with preformed nitrites/nitrates on the surface to those without, it is apparent that NH 3 first reacts with gas-phase NO and then with pre-stored surface NO x species. Moreover, the reduction of surface nitrites/nitrates is complete only for high NH 3 /NO ratios, and when NH 3 is the limiting reactant, they remain on the catalyst surface unreacted until temperatures higher than 623 K, where they decompose. In general, for all performed experiments, N 2 O was the dominant product at low temperature, when NO and NH 3 conversions are low. At higher temperature, with increasing NO and NH 3 conversions, N 2 selectivity increases.

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Section: Activity Studysupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

et al. 2018

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“…Nova et al [11] and Lietti et al [8] demonstrated that the NOx disproportionation reaction did not represent the major storage route under NO and NO/O2 mixtures due to the presence of nitrites in higher amounts than nitrates during the initial NOx adsorption at low temperatures. Same conclusion can be seen in Castoldi L et al [12] works which have confirmed participation of nitrite at 150℃, and nitrite only can be observed at the beginning of adsorption phase at 350℃. Epling W S et al [13] revealed that the two of major components of lean-burn engine exhaust, CO2 and H2O, compete for the same NOx adsorption sites, resulting in reduction of NOx storage capacity of LNT.…”

Section: Introductionsupporting

confidence: 85%

The effects of exhaust gas recirculation on NO_x storage pathway

Zhao

et al. 2021

E3S Web Conf.

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A LNT (lean NOx trap) model coupled with EGR (exhaust gas recirculation) was developed based on the Langmuir–Hinshelwood mechanism to investigate the EGR effects on NOx adsorption pathway of LNT catalysts with temperature changed in range 150℃~550℃. Both the nitrate and nitrite adsorption paths were considered for the NOx storage process in the model as well as the spillover of stored NOx between Ba and Pt sites. The data and validation for modelling were from literatures of predecessors and our previous lean-burn gasoline engine experiment*. The model quantified the contributions of both nitrate route and nitrite route to the NOx storage with change of EGR rate (0%~30%) under raw emission atmosphere from tested gasoline engine. The model captured key feature of different trends of nitrate route and nitrite route with increasing temperature (150℃~550℃) under EGR rate varying from 0% to 25%. The LNT model provided insight of reaction mechanism for interpreting the behaviour of NOx storage with change of GER rate and temperature, which contributed to improve the NOx storage capacity when mapping EGR rate for lean-burn engine and catalyst operation strategy optimization.

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“…Strategy I is the electrocatalytic oxidation of N 2 to HNO 3 by using air as the nitrogen source. Strategy II is the electrochemical reduction preparation of NH 3(aq) from residual nitrate ion ( \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}${\rm NO_{3}^{-}}$\end{document} ) contamination in water [ 25 , 26 ]: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}\begin{equation*} {\rm{NO}}_{3\;({\rm{aq}})}^ - \!+\! 6{{\rm{H}}_2}{{\rm{O}}_{({\rm{liq}})}} + 8{{\rm{e}}^ - }\!…”

Section: Introductionmentioning

confidence: 99%

Electrochemical synthesis of nitric acid from air and ammonia through waste utilization

Wang

Jia

et al. 2019

National Science Review

339

224

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Commercial nitric acid (HNO3) and ammonia (NH3) are mostly produced through the Ostwald process and the Haber-Bosch process, respectively. However, high energy demand and enormous greenhouse gas accompy these processes. The development of economical and green ways to synthesize HNO3 and NH3 is highly desirable for solving the global energy and environmental crisis. Here, we present two energy-efficient and environmentally friendly strategies to synthesize HNO3 and NH3 at distributed sources, including the electrocatalytic oxidation of N2 in air to HNO3 and the electrocatalytic reduction of residual ${\rm NO_{3}^{-}}$ contamination in water to NH3. The isotope-labeling studies combined with theoretical calculation reveal the reaction path of the two proposed strategies, confirming the origin of the electrochemical products. Importantly, the electrooxidation-generated ${\rm NO_{3}^{-}}$ ions may also serve as reactants for the electroreduction synthesis of NH3 in the future. Our work may open avenues for energy-efficient and green production of HNO3 and NH3 at distributed sources.

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New insights on the adsorption, thermal decomposition and reduction of NOx over Pt- and Ba-based catalysts

Cited by 46 publications

References 35 publications

Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

The effects of exhaust gas recirculation on NO_x storage pathway

Electrochemical synthesis of nitric acid from air and ammonia through waste utilization

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New insights on the adsorption, thermal decomposition and reduction of NOx over Pt- and Ba-based catalysts

Cited by 46 publications

References 35 publications

Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

Mechanistic Aspect of N2O Formation Over Pt–Ba/γ-Al2O3 Catalysts

The effects of exhaust gas recirculation on NOx storage pathway

Electrochemical synthesis of nitric acid from air and ammonia through waste utilization

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Product

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The effects of exhaust gas recirculation on NO_x storage pathway