Hexanedinitrile

Adiponitrile is an organic compound with the chemical formula (CH₂)₄(CN)₂. This viscous, colourless dinitrile is an important precursor to the polymer nylon 66. In 2005, about one million tonnes of adiponitrile were produced.M. T. Musser, "Adipic Acid" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.

Production

Early methods

Because of the industrial value of adiponitrile, many methods have been developed for its synthesis. Early industrial methods started from furfural and later by the chlorination of butadiene to give 1,4-dichloro-2-butene, which with sodium cyanide, converts to 3-hexenedinitrile, which in turn can be hydrogenated to adiponitrile:
:ClCH₂CH=CHCH₂Cl + 2 NaCN → NCCH₂CH=CHCH₂CN + 2 NaCl
:NCCH₂CH=CHCH₂CN + H₂ → NC(CH₂)₄CN
Adiponitrile has also been produced from adipic acid, by dehydration of the diamide, but this is rarely employed.

Modern methods

After patent application in 2004, the majority of adiponitrile is prepared by the nickel-catalysed hydrocyanation of butadiene, as discovered at DuPont, pioneered by Drinkard. The net reaction is:
: CH₂=CHCH=CH₂ + 2 HCN → NC(CH₂)₄CN

The process involves several stages, the first of which involves monohydrocyanation (the addition of one molecule of HCN), affording isomers of pentenenitriles as well as 2- and 3-methylbutanenitriles. These unsaturated nitriles are subsequently isomerized to the 3-and 4- pentenenitriles. In the final stage, these pentenenitriles are subjected to a second hydrocyanation, in an anti-Markovnikov sense, to produce adiponitrile.

3-pentenenitrile, formed in the first hydrocyanation, can undergo alkene metathesis to give dicyanobutenes, which are readily hydrogenated as described above. A useful byproduct of the production of adiponitrile is 2-methylglutaronitrile.

The other major industrial method involves hydrodimerization, starting from acrylonitrile:
:2 CH₂=CHCN + 2 e⁻ + 2 H⁺ → NCCH₂CH₂CH₂CH₂CN

The electrolytic coupling of acrylonitrile was discovered at Monsanto Company.

Applications

Almost all adiponitrile is hydrogenated to 1,6-diaminohexane for the production of nylon:
:NC(CH₂)₄CN + 4 H₂ → H₂N(CH₂)₆NH₂
Like other nitriles, adiponitrile is susceptible to hydrolysis; however the resulting adipic acid is less expensively prepared via other routes.

Production

In 2018 there existed approximately 1.5 million tons of capacity. The main producers of adiponitrile are:

*Ascend: Decatur,AL 400kt, being expanded to 580kt by 2022
*Invista: Victoria,TX and Orange,TX.
*Invista and BASFjv 'Butachimie': Chalampé (France). Production to be increased from 100kt in 2020 to 600kt.
*Asahi Kasei

BASF closed the 128kt ADN plant at Seal Sands in 2009.

In 2015, the Shandong Runxing New Material 100kt plant suffered an explosion and was not reopened.
In 2022, Invista plans to open a 300-400kt plant in Shanghai.

Safety

The for adiponitrile is 300 mg/kg for oral ingestion by rats.

In 1990, ACGIH adopted a time-weighted average Threshold Limit Value of 2ppm for work-related skin exposure.

The NIOSH recommended skin exposure limit for a work related time weighted average concentration is 4ppm (18 mg/m3).NIOSH Pocket Guide
NIOSH Publication 2005-149; September 2005

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.

References

External links

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*{{PGCH, 0015
www.chemicalland.comwww.nist.gov

Alkanedinitriles