Nitrogen oxides chemical manufacturing release

NDMA is not an industrially or commercially important chemical nevertheless, it can be released into the environment from a wide variety of manmade sources. This is due to the inadvertent formation of NDMA in industrial situations when alkylamines, mainly dimethylamine and trimethylamine, come in contact and react with nitrogen oxides, nitrous acid, or nitrite salts, or when trans-nitrosation via nitro or nitroso compounds occurs. Thus, potential exists for release into the environment from industries such as tanneries, pesticide manufacturing plants, rubber and tire manufacturers, alkylamine manufacture/use sites, fish processing industries, foundries and dye manufacturers. At this time, NDMA has been found in at least 1 out of 1177 hazardous waste sites on the National Priorities List (NPL) in the United States (VIEW Database 1989). 

The third principal source of nitrobenzene is the atmospheric photo-chemical reaction of nitrogen oxides with benzene, which presumably is derived from automobile fuels and, to a lesser extent, solvent uses of benzene (Dorigan and Hushon 1976). As benzene releases decline, this source (not quantified) should diminish as well. The contribution of this source is difficult to estimate since most measurements of ambient atmospheric nitrobenzene have been made in urban areas near sites of nitrobenzene manufacture, use, and disposal (see Section 5.4.1). Seasonal variations and those associated with air pollution episodes suggest that this source, although limited, may form a significant proportion of nonoccupational human exposure. 

A variation of the bios3mthesis described above can be used to make adipic acid, a key feedstock in the manufacture of nylon 6,6. As with catechol, the conventional chemical synthesis of adipic acid commonly starts with benzene, which is hydrogenated to cyclohexane. Air oxidation of cyclohexane over metal catalysts yields cyclo-hexanol and byproduct cyclohexanone. The oxidation of cyclohexanol with 60% nitric acid yields adipic acid. Elevated temperature (250°C), high pressure (50 atm), and the use of strong oxidant nitric acid, which carries with it the possibihty of nitrogen oxides release, are problems with the synthesis. 

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