Topic
Ammonia
About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.
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TL;DR: In this paper, the formation rate and reaction rate of ammonium sulfate salts on V 2 O 5 /AC catalyst during selective catalytic reduction (SCR) of NO with NH 3 at low temperatures were studied using elemental analysis, transient response, and TPR methods.
163 citations
01 Jan 2021
TL;DR: In this paper, a newly compiled kinetic model was developed for the prediction of the oxidation of ammonia and ammonia-hydrogen blends in freely propagating and burner stabilized premixed flames, as well as in shock tubes, rapid compression machines and a jet-stirred reactor.
Abstract: Laminar flame speeds of ammonia with oxygen-enriched air (oxygen content varying from 21 to 30 vol.%) and ammonia-hydrogen-air mixtures (fuel hydrogen content varying from 0 to 30 vol.%) at elevated pressure (1–10 bar) and temperature (298–473 K) were determined experimentally using a constant volume combustion chamber. Moreover, ammonia laminar flame speeds with helium as an inert were measured for the first time. Using these experimental data along with published ones, we have developed a newly compiled kinetic model for the prediction of the oxidation of ammonia and ammonia-hydrogen blends in freely propagating and burner stabilized premixed flames, as well as in shock tubes, rapid compression machines and a jet-stirred reactor. The reaction mechanism also considers the formation of nitrogen oxides, as well as the reduction of nitrogen oxides depending on the conditions of the surrounding gas phase. The experimental results from the present work and the literature are interpreted with the help of the kinetic model derived here. The experiments show that increasing the initial temperature, fuel hydrogen content, or oxidizer oxygen content causes the laminar flame speed to increase, while it decreases when increasing the initial pressure. The proposed kinetic model predicts the same trends than experiments and a good agreement is found with measurements for a wide range of conditions. The model suggests that under rich conditions the N2H2 formation path is favored compared to stoichiometric condition. The most important reactions under rich conditions are: NH2+NH=N2H2+H, NH2+NH2=N2H2+H2, N2H2+H=NNH+H2 and N2H2+M=NNH+H+M. These reactions were also found to be among the most sensitive reactions for predicting the laminar flame speed for all the cases investigated.
162 citations
TL;DR: In this paper, the photocatalytic conversion of NH3 to N2 greatly increases when the Pt/TiO2 suspension is saturated with N2O gas, whereas N 2O itself shows little reactivity with naked and metallized TiO2.
Abstract: Selective photocatalytic oxidation of NH3 to N2 is proposed as a new treatment method for controlling the levels of ammonia in water. The photocatalytic oxidation of ammonia on naked and metallized TiO2 in water saturated with air, nitrogen, or N2O gas was investigated. While the slow photocatalytic oxidation of NH3 to NO2-/NO3- is the only pathway for decomposition of NH3 on naked TiO2 and Au/TiO2, a new pathway, that of selective oxidation of ammonia to dinitrogen, opens up on Pt/TiO2. The formation of dinitrogen from the oxidation of 15NH3 was confirmed by mass spectrometric detection of 15N2. The photocatalytic conversion of NH3 to N2 greatly increases when the Pt/TiO2 suspension is saturated with N2O gas, whereas N2O itself shows little reactivity with naked TiO2 and Au/TiO2. Over 80% of the total nitrogen available in ammonia (0.1 mM) is converted into N2 within 40 min illumination of the N2O-saturated Pt/TiO2 suspension. The ability of N2O to accept the conduction band electrons of Pt/TiO2 was veri...
162 citations
TL;DR: The electrochemical oxidation of ammonia has been studied in the most detail in alkaline solution at platinized platinum as discussed by the authors, in which elemental nitrogen is formed at mildly positive potentials with near quantitative current efficiency through dimerization of partly dehydrogenated ammonia molecules NH x (ads).
162 citations
TL;DR: In this article, a review of copper-based catalysts for the selective catalytic reduction of NO x with ammonia (NH 3 -SCR, DeNO x ) is presented.
Abstract: More restrictive standards of Euro VI concerning nitrogen oxide (NO x = NO, NO 2 ) emissions necessitate an enhanced urea injection, while generating a higher ammonia slip, which is also precisely limited. For this reason, ammonia slip catalysts (ASC) are an essential part of efficient aftertreatment systems. Currently, supported noble metal catalysts are applied but possess limited selectivity to nitrogen. Copper based catalysts present a promising alternative for the selective catalytic ammonia oxidation into nitrogen and water vapour (NH 3 -SCO). This review article focusses on NH 3 -SCO as appropriate solution to abate unreacted ammonia particularly after the selective catalytic reduction of NO x with ammonia (NH 3 -SCR, DeNO x ). A brief overview of potential catalyst systems is provided, followed by a comprehensive discussion of copper based catalysts. Potential material classes including oxides, exchanged zeolites, modified clays or mixed forms are described systematically. The review focusses on structure-performance correlations covering copper loading, redox properties of CuO species and available acid sites of the catalysts. Another emphasis concerns the influence of the feed composition on the catalytic performance including the content of oxygen and water vapour or sulphur oxide in the feed. Finally, the proposed i-SCR mechanism over copper based catalysts, including bimetallic systems, is described and critically reviewed followed by general conclusions together with a discussion of promising research directions.
162 citations