Exothermal acrylonitrile production

The acetylene process was developed in Germany in the early 1940s to supply the synthetic rubber industry [19]. Acetylene is reacted with hydrogen cyanide in an aqueous medium in the presence of catalytic amounts of cuprous chloride. The reaction is maintained at 80 90°C at a pressure of 1-2 atm. The reaction is highly exothermic forming a gaseous reactor effluent. This crude product is water-scrubbed and the pure acrylonitrile product is recovered from the resultant 1-3% aqueous solution by fractional distillation. The major drawbacks of this process are the large number of by-products formed by hydration, the loss of catalyst activity from hydrolysis reactions, and the buildup of ammonium chloride and tars. 

Simple alkyl radicals such as methyl are considered to be nonnucleophilic. Methyl radicals are somewhat more reactive toward alkenes bearing electron-withdrawing substituents than towards those with electron-releasing substituents. However, much of this effect can be attributed to the stabilizing effect that these substiments have on the product radical. There is a strong correlation of reaction rate with the overall exothermicity of the reaction. Hydroxymethyl and 2-hydroxy-2-propyl radicals show nucleophilic character. The hydroxymethyl radical shows a slightly enhanced reactivity toward acrylonitrile and acrolein, but a sharply decreased reactivity toward ethyl vinyl ether. Table 12.9 gives some of the reactivity data. 

The fluidized-bed process for this reaction has several advantages over a fixed-bed process. First, the process is highly exothermic, and the selectivity to C3H3N is temperature dependent. The improved temperature control of the fluidized-bed operation enhances the selectivity to acrylonitrile, and substantially extends the life of the catalyst, which readily sinters at temperatures in excess of 800 K. Furthermore, since both the reactants and products are flammable in air, the use of a fluidized bed enables the moving particles to act to quench flames, preventing combustion and ensuring safe operation. 

Further evidence for the hypothesis was found in the patent describing the isoprene—acrylonitrile—zinc chloride system (23). On adding a four-fold excess of isoprene to an equimolar mixture of acrylonitrile and zinc chloride, in the absence of a free radical catalyst, an exothermic reaction occurs after approximately 30 minutes. The recovered polymer is insoluble in hydrocarbons, chloroform, and acetone. This eliminates polyisoprene and the alternating copolymer. The yield of product is 12%, calculated a polyacrylonitrile, compared with the 16.8% yield of copolymer obtained when excess acrylonitrile and a free radical catalyst are used. 

Description Propylene, ammonia, and air are fed to a fluidized bed reactor to produce acrylonitrile (ACRN) using DuPont s proprietary catalyst system. Other useful products from the reaction are hydrogen cyanide (HCN) and acetonitrile (ACE). The reaction is highly exothermic and heat is recovered from the reactor by producing high-pressure steam. The reactor effluent is quenched and neutralized with a sulfuric solution to remove the excess ammonia. 

The reaction is highly exothermic and the heat of reaction is generally used to make high-pressure steam, utilized downstream in separation and purificahon operations. The main useful by-products from the process are HCN (about 0.1kg per kg of acrylonitrile), which is used primarily in the manufacture of methyl methacrylate, and acetonitrile (about 0.03 kg per kg of acrylonitrile), a common industrial solvent. Smaller quantities of carbon oxides and nitrogen (from ammonia combushon) are also obtained. Unreacted ammonia in the reactor effluent is neutralized with sulfuric acid. The resulting ammonium sulfate can be recovered for use as a fertilizer. 

The Sohio process is considered one of the most successful applications of FCB. Problems in industrial application of the reaction arose from the strong exothermicity of propylene ammoxidation and from the intermediate production of acrylonitrile in the consecutive reactions (V9). It is particularly noticeable that the catalyst gives high selectivity, and the reactor design aims at better fluidization and higher contact efficiency than in the FCC process. 

RUBIDIUM HYDROXIDE (1310-82-3) RbOH Extremely basic substance more basic than potassium hydroxide. Extremely hygroscopic. Violent, exothermic reaction with water. Violent reaction with acids, acrylonitrile, glycidol, nitrobenzene, TNT. Exothermic decomposition with maleic anhydride. Hydrolyzes angiotonin. Incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, isocyanates, ketones, glycols, nitrates, phenols, vinyl acetate. Increases the explosive sensitivity of nitromethane. Reacts with nitroalkanes, forming explosive products. Attacks glass, metals, plastics, and mbbers. 

The spun filament should have a relatively fine count (e.g., 1.22 d tex), which enables the fiber to be heated through to the center at a fairly rapid rate and conversely, permits more readily the dissipation of the heat evolved in the strongly exothermic initial oxidation stage of the carbon fiber manufacturing process. A precursor of about 0.8 d tex would permit a more uniform structure of the oxidized fiber, but with reduced production. The control of heat flux, reaction rate and temperature of initiation can also be influenced by the choice of comonomer(s) and the actual ratio of these comonomer(s) to the acrylonitrile content. 

Two investigations have been made on polyacrylonitrile in fibre form. The first reports on rates of formation of degradation products and the second on exothermic reactions and discolouration. The latter paper also reports the effect of copolymerization of acrylonitrile with 2-vinylpyridine upon these reactions. 

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