In the SOHIO process, propylene, ammonia, and air (oxidizer) are passed through a fluidized bed reactor containing the catalyst at 400–510 °C and 50–200 kPag. The reactants pass through the reactor only once, before being quenched in aqueous sulfuric acid. Excess propylene, carbon monoxide, carbon dioxide, and dinitrogen that do not dissolve are vented directly to the atmosphere, or are incinerated. The aqueous solution consists of acrylonitrile, acetonitrile, hydrocyanic acid, and ammonium sulfate (from excess ammonia). A recovery column removes bulk water, and acrylonitrile and acetonitrile are separated by distillation. One of the first useful catalysts was bismuthphosphomolybdate (Bi9PMo12O52) supported on silica.[11] Further improvements have since been made.[5]
Alternative routes
Various green chemistry routes to acrylonitrile are being explored from renewable feedstocks, such as lignocellulosic biomass, glycerol (from biodiesel production), or glutamic acid (which can itself be produced from renewable feedstocks). The lignocellulosic route involves fermentation of the biomass to propionic acid and 3-hydroxypropionic acid, which are then converted to acrylonitrile by dehydration and ammoxidation.[12][9] The glycerol route begins with its dehydration to acrolein, which undergoes ammoxidation to give acrylonitrile.[13] The glutamic acid route employs oxidative decarboxylation to 3-cyanopropanoic acid, followed by a decarbonylation-elimination to acrylonitrile.[14] Of these, the glycerol route is broadly considered to be the most viable, although none of these green methods are commercially competitive.[12][13]
Hydrogenation of acrylonitrile is one route to propionitrile. Hydrolysis with sulfuric acid gives acrylamide sulfate, CH=CHC(O)NH2·H2SO4. This salt can be converted to acrylamide with treatment with base or to methyl acrylate by treatment with methanol.[5]
The reaction of acrylonitrile with protic nucleophiles is a common route to a variety of specialty chemicals. The process is called cyanoethylation:
It evaporates quickly at room temperature (20 °C) to reach dangerous concentrations; skin irritation, respiratory irritation, and eye irritation are the immediate effects of this exposure.[24] Pathways of exposure for humans include emissions, auto exhaust, and cigarette smoke that can expose the human subject directly if they inhale or smoke. Routes of exposure include inhalation, oral, and to a certain extent dermal uptake (tested with volunteer humans and in rat studies).[25] Repeated exposure causes skin sensitization and may cause central nervous system and liver damage.[24]
There are two main excretion processes of acrylonitrile. The primary method is excretion in urine when acrylonitrile is metabolized by being directly conjugated to glutathione. The other method is when acrylonitrile is enzymatically converted into 2-cyanoethylene oxide which will produce cyanide end products that ultimately form thiocyanate, which is excreted via urine.[25] Exposure can thus be detected via blood draws and urine sampling.[18]
Incidents
A large amount of acrylonitrile (approximately 6500 tons) leaked from an industrial polymer plant owned by Aksa Akrilik after the violent 17 August earthquake in Turkey. Over 5000 people were affected and the exposed animals had died.[26] The leak was only noticed by the company 8 hours after the incident. Healthcare workers did not know about the health effects of acrylonitrile and tried to treat the victims with painkillers and IV fluids.[27] One lawyer, Ayşe Akdemir, sued the company with 44 families as the plaintiffs.[27] Aksa Akrilik was sued by 200 residents who were affected by acrylonitrile.[28] An increase in cancer cases in the area was confirmed by the Turkish Medical Association,[28] as the cancer rate in the affected area has increased by 80%, from 1999 to April 2002.[27] In 2003, the owner of Aksa Akrilik has died from lung cancer related to acrylonitrile exposure.[27] As of 2001, this is the largest acrylonitrile leak known.[26]
Occurrence
Acrylonitrile is not naturally formed on Earth. It has been detected at the sub-ppm level at industrial sites. It persists in the air for up to a week. It decomposes by reacting with oxygen and hydroxyl radical to form formyl cyanide and formaldehyde.[29]
Acrylonitrile is harmful to aquatic life.[24]
Acrylonitrile has been detected in the atmosphere of Titan, a moon of Saturn.[30][31][32] Computer simulations suggest that on Titan conditions exist such that the compound could form structures similar to cell membranes and vesicles on Earth, called azotosomes.[30][31]
Moureu, C. (1893). "Contribution à l'étude de l'acide acrylique et de ses dérivés" [Contribution to the study of acrylic acid and of its derivatives]. Annales de chimie et de physique. 7th. 2: 145–212. See especially pp. 187–189 ("Nitrile acrylique ou cyanure de vinyle (Propène-nitrile)").
^Grasselli, Robert K. (2014). "Site isolation and phase cooperation: Two important concepts in selective oxidation catalysis: A retrospective". Catalysis Today. 238: 10–27. doi:10.1016/j.cattod.2014.05.036.
^ abGrasselli, Robert K.; Trifirò, Ferruccio (2016). "Acrylonitrile from Biomass: Still Far from Being a Sustainable Process". Topics in Catalysis. 59 (17–18): 1651–1658. doi:10.1007/s11244-016-0679-7. ISSN1022-5528. S2CID99550463.
^ abGuerrero-Pérez, M. Olga; Bañares, Miguel A. (2015). "Metrics of acrylonitrile: From biomass vs. petrochemical route". Catalysis Today. 239: 25–30. doi:10.1016/j.cattod.2013.12.046. ISSN0920-5861.
^Le Nôtre, Jérôme; Scott, Elinor L.; Franssen, Maurice C. R.; Sanders, Johan P. M. (2011). "Biobased synthesis of acrylonitrile from glutamic acid". Green Chemistry. 13 (4): 807. doi:10.1039/c0gc00805b. ISSN1463-9262.
^Ellis, Paul G (1972). A radiation-chemical study of the hydrodimerisation of acrylonitrile. UK: Leeds University, Ph D thesis.
^Buxton, George V.; Ellis, Paul G.; McKillop, Thomas F.W. (1979). "Pulse radiolysis study of acrylonitrile in aqueous solution". J. Chem. Soc., Faraday Trans. 1. 75: 1050. doi:10.1039/f19797501050.
^Cunningham FH, Fiebelkorn S, Johnson M, Meredith C. A novel application of the Margin of Exposure approach: segregation of tobacco smoke toxicants. Food Chem Toxicol. 2011 Nov;49(11):2921-33. doi: 10.1016/j.fct.2011.07.019. Epub 2011 Jul 23. PMID21802474
^Pu X, Kamendulis LM, Klaunig JE. Acrylonitrile-induced oxidative stress and oxidative DNA damage in male Sprague-Dawley rats. Toxicol Sci. 2009;111(1):64-71. doi:10.1093/toxsci/kfp133
