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Production. Until the mid-1970s malononitrile was obtained by dehydration of cyanoacetamide [107-91-5], with phosphorous pentachloride or phosphorous oxychloride in a batch process. Nowadays, only Chinese producers use this process for the production of small amounts. By far the major part is manufactured by a continuous high-temperature process in which acetonitrile and cyanogen chloride are fed into a tube reactor above 700°C. Almost complete conversion is attained in one pass. The reaction products are malononitrile, excess acetonitrile, hydrochloric acid, and traces of maleic, succinic, and fumaric acids. The products leaving the reactor are immediately quenched to 40 - 80°C, and gaseous hydrogen chloride is simultaneously separated, fed into a scrubber, and recovered as dilute hydrochloric acid. Excess acetonitrile is removed by a combination of vacuum distillation and thin-film evaporation. The recovered acetonitrile contains very little hydrogen chloride and can be recycled.
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Production plant in Visp, Switzerland
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Removal of maleic and fumaric acid from the crude malononitrile by fractional distillation is impractical because the boiling points of these acids and malononitrile differ only slightly. Therefore, the impurities are converted into high-boiling compounds in a conventional reactor by means of a Diels - Alder reaction. The byproducts are finally removed by two vacuum distillations.
Lonza in Visp (Switzerland) brought the first and so far the only industrial plant using this process on stream in 1973
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Packaging specification
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| Malononitrile is shipped as solidified melt packed into 50 kg and 200 kg net special lined drums or as a solution in methanol. |
Contents partly based on Ullmanns Encyclopedia http://www.ullmanns.de
Malonic Acid and Derivatives, Product: Ullmann's Encyclopedia of Industrial Chemistry, Section: Malononitrile, 15 March, 2001, Stefan Hildbrand Peter Pollak with the authorization of Wiley - VCH http://www.interscience.com |
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