Adiponitrile acrylonitrile

Acrylonitrile resembles VC, a carcinogen, in structure. It is a flammable, explosive liquid (b.p. 77 C, V.P. 80 mm at 20°C). AN is a component of acrylic and modacrylic fibers produced by copolymerization with other monomers, e.g., with methyl acrylate, Me-methacrylate, vinyl acetate, VC and VDC. Other major uses of AN include copolymerizations with butadiene and styrene to produce ABS polymers, and with styrene to yield SAN resins which are used in the manufacture of plastics. Nitrile elastomers and latexes are also made with AN, as are a number of other chemicals, e.g. acrylamide and adiponitrile. Acrylonitrile is also used as a fumigant. 

Adiponitrile Acrylonitrile Monsanto (US) Monsanto (UK) Asahi (Japan) 10 kg/yr 10 kg/yr 2 X 107 kg/yr Reductive coupling... 

Adiponitrile Acrylonitrile Monsanto Asahi Chemical Rhone Poulenc... 

H2N (CH2)a NH2- Colourless solid when pure m.p. 4LC, b.p. 204 C. Manufactured by the electrochemical combination of two molecules of acrylonitrile to adiponitrile followed by catalytic reduction, or by a series of steps from cyclohexanone via adipic acid. Used in the production of Nylon [6, 6]. 

The reduction of acrylonitrile, CH2=CHCN, to adiponitrile, NC(CH2)4CN, is an important industrial process. A 0.594-g sample of acrylonitrile is placed in a 1 -L volumetric flask and diluted to volume. An exhaustive controlled-potential electrolysis of a 1.00-mL portion of the diluted acrylonitrile requires 1.080 C of charge. What is the value of n for this reduction ... 

Addition of HCN to unsaturated compounds is often the easiest and most economical method of making organonitnles. An early synthesis of acrylonitrile involved the addition of HCN to acetylene. The addition of HCN to aldehydes and ketones is readily accompHshed with simple base catalysis, as is the addition of HCN to activated olefins (Michael addition). However, the addition of HCN to unactivated olefins and the regioselective addition to dienes is best accompHshed with a transition-metal catalyst, as illustrated by DuPont s adiponitrile process (6—9). 

Adiponitrile is made commercially by several different processes utilizing different feedstocks. The original process, utilizing adipic acid (qv) as a feedstock, was first commercialized by DuPont in the late 1930s and was the basis for a number of adiponitrile plants. However, the adipic acid process was abandoned by DuPont in favor of two processes based on butadiene (qv). During the 1960s, Monsanto and Asahi developed routes to adiponitrile by the electrodimerization of acrylonitrile (qv). 

The Monsanto adiponitrile process, first commercialized in 1965 (65—67), involves the dimerization of acrylonitrile at the cathode in an electrolytic cell (eq. 7) ... 

Small amounts of propionitrile and bis(cyanoethyl) ether are formed as by-products. The hydrogen ions are formed from water at the anode and pass to the cathode through a membrane. The catholyte that is continuously recirculated in the cell consists of a mixture of acrylonitrile, water, and a tetraalkylammonium salt the anolyte is recirculated aqueous sulfuric acid. A quantity of catholyte is continuously removed for recovery of adiponitrile and unreacted acrylonitrile the latter is fed back to the catholyte with fresh acrylonitrile. Oxygen that is produced at the anodes is vented and water is added to the circulating anolyte to replace the water that is lost through electrolysis. The operating temperature of the cell is ca 50—60°C. Current densities are 0.25-1.5 A/cm (see Electrochemical processing). 

A typical composition of the catholyte is adiponitrile, 15 wt % acrylonitrile, 15 wt % quaternary ammonium salt, 39 wt % water, 29 wt % and by-products, 2 wt %. Such a solution is extracted with acrylonitrile and water, which separates the organics from the salt that can be returned to the cell. 

The acrylonitrile is distilled from the extract and the resultant residue consists of ca 91 wt % adiponitrile, which is purified further by distillation. The overall yield of acrylonitrile to adiponitrile is 92—95%. 

A.sahi Chemical EHD Processes. In the late 1960s, Asahi Chemical Industries in Japan developed an alternative electrolyte system for the electroreductive coupling of acrylonitrile. The catholyte in the Asahi divided cell process consisted of an emulsion of acrylonitrile and electrolysis products in a 10% aqueous solution of tetraethyl ammonium sulfate. The concentration of acrylonitrile in the aqueous phase for the original Monsanto process was 15—20 wt %, but the Asahi process uses only about 2 wt %. Asahi claims simpler separation and purification of the adiponitrile from the catholyte. A cation-exchange membrane is employed with dilute sulfuric acid in the anode compartment. The cathode is lead containing 6% antimony, and the anode is the same alloy but also contains 0.7% silver (45). The current efficiency is of 88—89%, with an adiponitrile selectivity of 91%. This process, started by Asahi in 1971, at Nobeoka City, Japan, is also operated by the RhcJ)ne Poulenc subsidiary, Rhodia, in Bra2il under Hcense from Asahi. 

Asahi also reports an undivided cell process employing a lead alloy cathode, a nickel—steel anode, and an electrolyte composed of an emulsion of 20 wt % of an oil phase and 80 wt % of an aqueous phase (125). The aqueous phase is 10 wt % K HPO, 3 wt % K B O, and 2 wt % (C2H (C4H )2N)2HP04. The oil phase is about 28 wt % acrylonitrile and 50 wt % adiponitrile. The balance of the oil phase consists of by-products and water. The cell operates at a current density of 20 A/dm at 50°C. Circulated across the cathode surface at a superficial velocity of 1.5 m/s is the electrolyte. A 91% selectivity to adiponitrile is claimed at a current efficiency of 90%. The respective anode and cathode corrosion rates are about mg/(Ah). Asahi s improved EHD process is reported to have been commercialized in 1987. 

Hydrogen cyanide (hydrocyanic acid) is a colorless liquid (b.p. 25.6°C) that is miscible with water, producing a weakly acidic solution. It is a highly toxic compound, but a very useful chemical intermediate with high reactivity. It is used in the synthesis of acrylonitrile and adiponitrile, which are important monomers for plastic and synthetic fiber production. 

Hydrogen cyanide is a reactant in the production of acrylonitrile, methyl methacrylates (from acetone), adiponitrile, and sodium cyanide. It is also used to make oxamide, a long-lived fertilizer that releases nitrogen steadily over the vegetation period. Oxamide is produced by the reaction of hydrogen cyanide with water and oxygen using a copper nitrate catalyst at about 70°C and atmospheric pressure ... 

Acrylonitrile is mainly used to produce acrylic fibers, resins, and elastomers. Copolymers of acrylonitrile with butadiene and styrene are the ABS resins and those with styrene are the styrene-acrylonitrile resins SAN that are important plastics. The 1998 U.S. production of acrylonitrile was approximately 3.1 billion pounds. Most of the production was used for ABS resins and acrylic and modacrylic fibers. Acrylonitrile is also a precursor for acrylic acid (by hydrolysis) and for adiponitrile (by an electrodimerization). 

Adiponitrile is an important intermediate for producing nylon 66. There are other routes for its production, which are discussed in Chapter 9. The way to produce adiponitrile via propylene is the electrodimerization of acrylonitrile. The following is a representation of the electrochemistry involved ... 

Adiponitrile may also be produced by the electrodimerization of acrylonitrile (Chapter 8) or by the reaction of ammonia with adipic acid followed by two-step dehydration reactions ... 

Acrylic textile fibers are primarily polymers of acrylonitrile. It is copolymerized with styrene and butadiene to make moldable plastics known as SA and ABS resins, respectively. Solutia and others electrolytically dimerize it to adiponitrile, a compound used to make a nylon intermediate. Reaction with water produces a chemical (acrylamide), which is an intermediate for the production of polyacrylamide used in water treatment and oil recovery. 

Adiponitrile is produced at over 1 million tpa and, being used in the manufacture of hexamethylene diamine and (to a small extent) adipic acid, it is by far the highest-volume organic material that is produced electro-chemically. The mechanism (Scheme 7.13) involves electrolytic reduction of acrylonitrile followed by protonation, further reduction, Michael addition and a final protonation step. 

Reactions of this type are called electrochemical hydrodimerization. They are of great value for the synthesis of various bifunctional compounds. A reaction that has found wide commercial nse is the hydrodimerization of acrylonitrile to adiponitrile (the dinitrile of adipic acid) ... 

Electroorganic synthesis will be covered in section 4.5.4. It is appropriate, however, to make a reference here to the role of u/s in electroorganic processes. Atobe et al. (2000) have reported the effect of u/s in the reduction of acrylonitrile and mixtures of acrylonitrile and methyl acrylate. The selectivity for adiponitrile in the reduction of acrylonitrile was significantly increased under u/s irradiation with a power intensity over the u/s cavitation threshold ( 600 cm ). This favourable influence of u/s can be attributed to the improved mass transfer of acrylonitrile to the electrode interface by the cavitational high-speed jet-stream. 

Hexamethylenediamine (HMDA), a monomer for the synthesis of polyamide-6,6, is produced by catalytic hydrogenation of adiponitrile. Three processes, each based on a different reactant, produce the latter coimnercially. The original Du Pont process, still used in a few plants, starts with adipic acid made from cyclohexane adipic acid then reacts with ammonia to yield the dinitrile. This process has been replaced in many plants by the catalytic hydrocyanation of butadiene. A third route to adiponitrile is the electrolytic dimerization of acrylonitrile, the latter produced by the ammoxidation of propene. 

The primary use of acrylonitrile is as the raw material for the manufacture of acrylic and modacrylic fibers. Other Major uses include the production of plastics (acrylonitrile-butadiene- styrene (ABS) and styrene-acrylonitrile (SAN), nitrile rubbers, nitrile barrier resins, adiponitrile and acrylamide (EPA 1984). 

---