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Encyclopedia > Nitrogen oxide

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The term nitrogen oxide typically refers to any binary compound of oxygen and nitrogen, or to a mixture of such compounds: A binary compound is a compound that contains two different elements, such as NaCl (salt). ... This article is about the chemical element and its most stable form, or dioxygen. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...

(Note that the last three are unstable.) R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... For other uses, see Nitrous oxide (disambiguation). ... The chemical compound dinitrogen trioxide (chemical formula: N2O3) is a pale blue liquid, and is unstable above 3°C (37° F) at standard pressure. ... Nitrogen tetroxide (or dinitrogen tetroxide) is the chemical compound N2O4. ... Dinitrogen pentoxide is the binary nitrogen oxide N2O5, also known as nitrogen pentoxide. ...


Chemical reactions that produce nitrogen oxides often produce several, the proportions depending on the specific reaction and conditions. This is one reason why secondary production of N2O is undesirable; the other two stable oxides — which are extremely toxic — are liable to be produced. For other uses, see Chemical reaction (disambiguation). ...

Image File history File links Download high-resolution version (1100x886, 154 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Nitric oxide Nitrogen oxide ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... Image File history File links Download high-resolution version (1100x858, 154 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Inorganic chemistry Nitrogen dioxide Nitrogen oxide ... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... Image File history File links Download high-resolution version (1100x807, 150 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Nitrous oxide Nitrogen oxide ... For other uses, see Nitrous oxide (disambiguation). ... Image File history File links Download high-resolution version (1100x955, 196 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Nitrogen oxide Dinitrogen trioxide ... The chemical compound dinitrogen trioxide (chemical formula: N2O3) is a pale blue liquid, and is unstable above 3°C (37° F) at standard pressure. ... Image File history File links Download high resolution version (1100x948, 199 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Dinitrogen tetroxide Nitrogen oxide User:Benjah-bmm27/Gallery User:Ben Mills/Gallery ... Nitrogen tetroxide (or dinitrogen tetroxide) is the chemical compound N2O4. ... Image File history File links Download high-resolution version (1100x756, 157 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Nitrogen oxide Dinitrogen pentoxide ... Dinitrogen pentoxide is the binary nitrogen oxide N2O5, also known as nitrogen pentoxide. ...

NOx

NOx is a generic term for mono-nitrogen oxides (NO and NO2). These oxides are produced during combustion, especially combustion at high temperatures. Look up nox, Nox in Wiktionary, the free dictionary. ... This article is about the chemical reaction combustion. ...


At ambient temperatures, the oxygen and nitrogen gases in air will not react with each other. In an internal combustion engine, combustion of a mixture of air and fuel produces combustion temperatures high enough to drive endothermic reactions between atmospheric nitrogen and oxygen in the flame, yielding various oxides of nitrogen. In areas of high motor vehicle traffic, such as in large cities, the amount of nitrogen oxides emitted into the atmosphere can be quite significant. General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... A colorized automobile engine The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... This article is about the chemical element and its most stable form, or dioxygen. ... An oxide is a chemical compound containing at least one oxygen atom and other elements. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...


In the presence of excess oxygen (O2), nitric oxide (NO) will be converted to nitrogen dioxide (NO2), with the time required dependent on the concentration in air as shown below:[1] R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ...

NO concentration in air

(ppm)

Time required for half NO

to be oxidized to NO2 (min)

20,000 0.175
10,000 0.35
1,000 3.5
100 35
10 350
1 3500

When NOx and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog, a significant form of air pollution, especially in the summer. Children, people with lung diseases such as asthma, and people who work or exercise outside are susceptible to adverse effects of smog such as damage to lung tissue and reduction in lung function.[2] This article describes a highly specialized aspect of its subject in the Terminology and legal definitions section. ... For other uses, see Smog (disambiguation). ...


Mono-nitrogen oxides eventually form nitric acid when dissolved in atmospheric moisture, forming a component of acid rain. The following chemical reaction occurs when nitrogen dioxide reacts with water: The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ... The term acid rain is commonly used to mean the deposition of acidic components in rain, snow, fog, dew, or dry particles. ...

2NO2 + H2O → HNO2 + HNO3

(nitrogen dioxide + water → nitrous acid + nitric acid).


Nitrous acid then decomposes as follows:

3HNO2 → HNO3 + 2NO + H2O

(nitrous acid → nitric acid + nitric oxide + water),


where nitric oxide will oxidize to form nitrogen dioxide that again reacts with water, ultimately forming nitric acid: R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... To oxidize an element or a compound is to increase its oxidation number. ...

4NO + 3O2 + 2H2O → 4HNO3 (nitric oxide + oxygen + water → nitric acid).

Mono-nitrogen oxides are also involved in tropospheric production of ozone.[3] The troposphere is the lowermost portion of Earths atmosphere and the one in which most weather phenomena occur. ... For other uses, see Ozone (disambiguation). ...


NOx should not be confused with NOS, a term used to refer to nitrous oxide (N2O) in the context of its use as a power booster for internal combustion engines. This page discusses the use of nitrous oxide in a racing context. ...


Definition of NOx and NOy in atmospheric chemistry

In atmospheric chemistry the term NOx is used to mean the total concentration of NO plus NO2. During daylight NO and NO2 are in equilibrium with the ratio NO/NO2 determined by the intensity of sunshine (which converts NO2 to NO) and ozone (which reacts with NO to give back NO2). NO and NO2 are also central to the formation of tropospheric ozone. This definition excludes other oxides of nitrogen such as nitrous oxide (N2O). NOy (reactive odd nitrogen) is defined as the sum of NOx plus the compounds produced from the oxidation of NOx which include nitric acid and peroxyacetyl nitrate. In this context nitrous oxide and ammonia are not considered as reactive nitrogen compounds. Atmospheric chemistry is a branch of atmospheric science in which the chemistry of the Earths atmosphere and that of other planets is studied. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... [1] R-phrases , S-phrases , , , , , Supplementary data page Structure and properties n, εr, etc. ... Seasonal average concentrations of tropospheric ozone in Dobson units over the period 1979 to 2000. ... The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ... Peroxyacetyl nitrate, or PAN for shorthand, is an organic compound consisting of oxygen, and nitrogen as well as a short hydrocarbon chain. ... For other uses, see Ammonia (disambiguation). ...


Industrial sources of NOx

The three primary sources of NOx in combustion processes: This article is about the chemical reaction combustion. ...

  • thermal NOx
  • fuel NOx
  • prompt NOx

Thermal NOx formation, which is highly temperature dependent, is recognized as the most relevant source when combusting natural gas. Fuel NOx tends to dominate during the combustion of fuels, such as coal, which have a significant nitrogen content, particularly when burned in combustors designed to minimise thermal NOx. The contribution of prompt NOx is normally considered negligible. A fourth source, called feed NOx is associated with the combustion of nitrogen present in the feed material of cement rotary kilns, at between 300° and 800°C, where it is also a minor contributor.


Thermal NOx

Thermal NOx refers to NOx formed through high temperature oxidation of the diatomic nitrogen found in combustion air. The formation rate is primarily a function of temperature and the residence time of nitrogen at that temperature. At high temperatures, usually above 1600°C (2900°F), molecular nitrogen (N2) and oxygen (O2) in the combustion air disassociate into their atomic states and participate in a series of reactions. A residence time is the average time a substance spends within a specified region of space, such as a reservoir. ...


The three principal reactions producing thermal NOx are:


(Extended Zeldovich Mechanism) Yakov Borisovich Zeldovich (Russian:Яков Борисович Зельдович) (March 8, 1914 – December 2, 1987) was a prolific Soviet physicist. ...

  • N2 + O → NO + N
  • N + O2 → NO + O
  • N + OH → NO + H

all 3 reactions are reversible. Zeldovich was the first to suggest the importance of the first two reactions. The last reaction of atomic Nitrogen with Hydroxyl radical, OH, was added by Lavoie, Heywood and Keck to the mechanism and makes a significiant contribution to the formation of thermal NOxx.


Fuel NOx

The major source of NOx production from nitrogen-bearing fuels such as certain coals and oil, is the conversion of fuel bound nitrogen to NOx during combustion. During combustion, the nitrogen bound in the fuel is released as a free radical and ultimately forms free N2, or NO. Fuel NOx can contribute as much as 50% of total emissions when combusting oil and as much as 80% when combusting coal. In chemistry, radicals (often referred to as free radicals) are atomic or molecular species with unpaired electrons on an otherwise open shell configuration. ...


Although the complete mechanism is not fully understood, there are two primary paths of formation. The first involves the oxidation of volatile nitrogen species during the initial stages of combustion. During the release and prior to the oxidation of the volatiles, nitrogen reacts to form several intermediaries which are then oxidized into NO. If the volatiles evolve into a reducing atmosphere, the nitrogen evolved can readily be made to form nitrogen gas, rather than NOx. The second path involves the combustion of nitrogen contained in the char matrix during the combustion of the char portion of the fuels. This reaction occurs much more slowly than the volatile phase. Only around 20% of the char nitrogen is ultimately emitted as NOx, since much of the NOx that forms during this process is reduced to nitrogen by the char, which is nearly pure carbon. Charring is a process of incomplete combustion that often occurs when biological tissue (living or dead) is subjected to heat. ...


Prompt NOx

This third source is attributed to the reaction of atmospheric nitrogen, N2, with radicals such as C, CH, and CH2 fragments derived from fuel, where this cannot be explained by either the aforementioned thermal or fuel processes. Occurring in the earliest stage of combustion, this results in the formation of fixed species of nitrogen such as NH (nitrogen monohydride), HCN (hydrogen cyanide), H2CN (dihydrogen cyanide) and CN- (cyano radical) which can oxidize to NO. In fuels that contain nitrogen, the incidence of prompt NOx is especially minimal and it is generally only of interest for the most exacting emission targets. R-phrases , , , , . S-phrases , , , , , , , , . Flash point −17. ... A cyanide is any chemical compound that contains the cyano group C≡N, with the carbon atom triple-bonded to the nitrogen atom. ...


Regulation and emission control technologies

The United States Environmental Protection Agency (EPA) regulates and enforces NOx emission limits in the U.S. in accordance to legislation passed by the United States Congress. The Kyoto Protocol, ratified by 54 nations in 1997, calls for a substantial world wide reduction of greenhouse gases including nitrous oxide. EPA redirects here. ... The Kyoto Protocol is a protocol to the international Framework Convention on Climate Change with the objective of reducing greenhouse gases that cause climate change. ... Greenhouse gases are gaseous components of the atmosphere that contribute to the greenhouse effect. ...


Technologies such as flameless oxidation (FLOX) and staged combustion significantly reduce thermal NOx in industrial processes. Bowin low NOx technology is a hybrid of staged-premixed-radiant combustion technology with a major surface combustion preceded by a minor radiant combustion. In the Bowin burner, air and fuel gas are premixed at a ratio greater than or equal to the stoichiometric combustion requirement.[4] Water Injection technology, wherby water is introduced into the combustion chamber, is also becoming an important means of NOx reduction through increased efficiency in the overall combustion process. Alternatively, the water (e.g. 10 to 50%) is emulsified into the fuel oil prior to the injection and combustion. This emulsification can either be made in-line (unstabilized) just before the injection or as a drop-in fuel with chemical additives for long term emulsion stability (stabilized). Other technologies, such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) reduce post combustion NOx. FLOX® is a combustion process developed by WS Wärmeprozesstechnik GmbH. It is said to reduce NOx formation by suppressing peak flame temperatures. ... One of John Joyces early sketches of the Low NOx burner A LO-NOx burner is a type of gas burner, invented by John Joyce, that significantly reduces the formation of oxides of nitrogen. ... One of John Joyces early sketches of the Low NOx burner A LO-NOx burner is a type of gas burner, invented by John Joyce, that significantly reduces the formation of oxides of nitrogen. ... Water injection is a method for cooling the combustion chambers of engines by adding water to the incoming fuel-air mixture, allowing for greater compression ratios and largely eliminating the problem of engine knocking. ... Selective Catalytic Reduction (SCR): Gaseous or liquid ammonia is added to the flue gas stream and is absorbed onto a catalyst. ... Selective Non Catalytic Reduction (SNCR) is a method for reducing nitrogen oxide emissions in conventional power plants that burn biomass. ...


The use of Exhaust gas recirculation and catalytic converters in motor vehicle engines have significantly reduced emissions. Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines. ... Catalytic converter on a Dodge Ram Van. ... Vehicle emissions inspection station Automobile emissions control covers all the technologies that are employed to reduce the air pollution-causing emissions produced by automobiles. ...


Biogenic sources

Agricultural fertilization and the use of nitrogen fixing plants also contribute to atmospheric NOx, by promoting nitrogen fixation by microorganisms.[5][6] Farming, ploughing rice paddy, in food, feed, fiber and other desired products by cultivation of certain plants and the raising of domesticated animals (livestock). ... Soil Fertilization or Crop Fertilization are methods of improving soil quality with a view towards improving soil fertility. ... Nitrogen fixation is the process by which nitrogen is taken from its relatively inert molecular form (N2) in the atmosphere and converted into nitrogen compounds useful for other chemical processes (such as, notably, ammonia, nitrate and nitrogen dioxide). ... For other uses, see Plant (disambiguation). ... Nitrogen fixation is the process by which nitrogen is taken from its natural, relatively inert molecular form (N2) in the atmosphere and converted into nitrogen compounds (such as, notably, ammonia, nitrate and nitrogen dioxide)[1] useful for other chemical processes. ...


References

  1. ^ NOx Removal. Branch Environmental Corp. Retrieved on 2007-12-26.
  2. ^ Health and Environmental Impacts of NOx. United States Environmental Protection Agency. Retrieved on 2007-12-26.
  3. ^ D. Fowler, et al. (1998). "The atmospheric budget of oxidized nitrogen and its role in ozone formation and deposition". New Phytologist 139: 11-23. 
  4. ^ Bob Joynt & Stephen Wu, Nitrogen oxides emissions standards for domestic gas appliances background study Combustion Engineering Consultant; February 2000
  5. ^ J.N. Galloway, et al. (Sep 2004). "Nitrogen cycles: past, present, and future". Biogeochemistry 70 (2): 153-226. doi:10.1007/s10533-004-0370-0. 
  6. ^ E.A. Davidson & W. Kingerlee (1997). "A global inventory of nitric oxide emissions from soils". Nutrient Cycling in Agroecosystems 48: 37-50. 
Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 360th day of the year (361st in leap years) in the Gregorian calendar. ... EPA redirects here. ... Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 360th day of the year (361st in leap years) in the Gregorian calendar. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

 
 

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