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In atmospheric chemistry, NOx is shorthand for nitric oxide (NO) and nitrogen dioxide (NO2), the nitrogen oxides that are most relevant for air pollution. [1][2] These gases contribute to the formation of smog and acid rain, as well as affecting tropospheric ozone. NOx gases are usually produced from the reaction between nitrogen and oxygen ...
Nitric oxide (nitrogen oxide or nitrogen monoxide[1]) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula (• N=O or • NO).
Selective catalytic reduction (SCR) means converting nitrogen oxides, also referred to as NO x with the aid of a catalyst into diatomic nitrogen (N 2), and water (H 2 O). A reductant, typically anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH), or a urea (CO(NH 2) 2) solution, is added to a stream of flue or exhaust gas and is reacted onto a ...
NOx (or NO x) refers to the sum of NO and NO2. [1][2] NOy (or NO y) refers to the sum of NOx and all oxidized atmospheric odd-nitrogen species (e.g. the sum of NOx, HNO3, HNO2, etc.) NOz (or NO z) = NOy − NOx. Mixed Oxides of Nitrogen ("MON"): solutions of nitric oxide in dinitrogen tetroxide/nitrogen dioxide. Nitric oxide, NO.
The term NO x represents several forms of nitrogen oxides such as NO (nitric oxide), NO 2 (nitrogen dioxide) and N 2 O (nitrous oxide, also known as laughing gas).In a gasoline engine, NO is the most common form of NO x at around 93%, while NO 2 is around 5% and the rest is N 2 O.
Nitrogen dioxide is a chemical compound with the formula NO2. One of several nitrogen oxides, nitrogen dioxide is a reddish-brown gas. It is a paramagnetic, bent molecule with C 2v point group symmetry. Industrially, NO2 is an intermediate in the synthesis of nitric acid, millions of tons of which are produced each year, primarily for the ...
Ozone is least concentrated in the ground layer (or planetary boundary layer) of the troposphere. Ground-level or tropospheric ozone is created by chemical reactions between NOx gases (oxides of nitrogen produced by combustion) and volatile organic compounds (VOCs). The combination of these chemicals in the presence of sunlight form ozone.
The early standards mainly concerned carbon monoxide (CO) and hydrocarbons (HC). Regulations on nitrogen oxide emissions (NO x) were introduced in the United States, Japan, and Canada in 1973 and 1974, with Sweden following in 1976 and the European Economic Community in 1977. These standards gradually grew more and more stringent but have never ...