Industrial processes adiponitrile

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 ... 

Development of the industrial process for electrochemical conversion of acrylonitrile to adiponitrile led to extensive investigation into the mechanism of the dimerization process. Reactions of acrylonitrile radical-anion are too fast for investigation but the dimerization step, for a number of more amenable substrates, has been investigated in aprotic solvents by electrochemical techniques. Pulse-radiolysis methods have also been used to study reactions in aqueous media. 

The initial drive for acrylonitrile (AN) production (6.2 Mt/a in 2004 worldwide) was the discovery, in the late 1930s, of the synthetic rubber Buna N. Today nitrile rubbers represent only a minor outlet for AN which is utilized primarily for polymerization to give textile fibres (50%) and ABS resins (24%), and for dimerization to adiponitrile (10%). Early industrial processes depended on the addition of hydrogen cyanide to acetylene or to ethylene oxide, followed by the dehydration of intermediate ethylene cyanohydrin. Both processes are obsolete and are now supplanted by the ammoxidation of propylene (Equation 34) introduced in 1960 by Standard Oil of Indiana (Sohio). The reason for the success stems from the effectiveness of the catalyst and because propylene,... 

The main disadvantages of the present industrial process are the use of large amounts of ammonia as solvent and the degradation of the Raney nickel catalyst either by attrition or leaching (solubilization in liquid ammonia). Considerable efforts are currently being made to search for efficient and resistant catalysts for the gas phase hydrogenation of adiponitrile with high hexamethylenediamine selectivity. 

In this chapter we shall consider first the largest-scale industrial process, the Monsanto hydrodimerization of acrylonitrile to adiponitrile, and then go on to discuss the other processes presently used or likely to be introduced in the near future. 

The single most successful industrial process based upon organic electrochemistry is the electrohydrodimerization of acrylonitrile to yield adiponitrile, introduced commercially in 1965 by Monsanto. The discovery, development, and commercialization of this process have been described in detail in recent articles that provide excellent insight into the commitment that is required to bring a process to commercial success. 

Production of Adiponitrile. The production of adiponitrile by hydrodimerization of acrylonitrile is the only organic electrochemical process used commercially to produce a large volume of organic chemical. Throughout the world, a total of more than 100,000 metric tons per year of adiponitrile is produced by this process. Adiponitrile is hydrogenated to hexamethylenediamine which is one of the components of nylon 66. The success in this process gave a significant impact to nylon industry. 

Presently the number of industrial processes using metal complex catalysts is continuously increasing. They include such classical large-tonnage processes as polymerization on the Ziegler catalysts, olefin oxidation by molecular oxygen to aldehydes, hydroformylation of saturated compounds, preparation of acetic acid from methanol and carbon monoxide, synthesis of adiponitrile fijom butadiene, and others. 

The production of adiponitrile (intermediate in the production of nylon 66) via electrosynthesis is an important industrial process. It also is a good example of how electrogenerated hydrogen atoms [H ] induce the dimerization and oligerimization of terminal olefins. In this process a solution that contains acrylonitrile and a quaternary ammonium salt is circulated through a cathode compartment with a lead electrode. A dilute solution of sulfuric acid is circulated through an anode compartment with a lead-alloy electrode. An ion-exchange membrane separates the two compartments ... 

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. 

The original process used aqueous tetraethylammonium ethylsulfate as the electrolyte, a lead cathode, and a lead-silver alloy anode. The Mark II process, commercialized in the mid-1970s, uses an emulsion of acrylonitrile in aqueous sodium phosphate containing a salt of the hexamethylene-bis-(ethyldibutylammonium) cation. The process was invented in 1959 by M. M. Baizer at Monsanto Corporation, St. Louis, MO. It was commercialized in 1965 and has been continuously improved ever since. The process is also operated in Japan by Asahi Chemical Industry Company. In 1990, the world production of adiponitrile by this process was over 200,000 tonnes per year. 

UCB-MCI [Union Chimique—Chemische Bedrijven and Ministry of Chemical Industry for the USSR] An EHD process for making adiponitrile, differing from the Monsanto process in using an emulsion of acrylonitrile and in not using a membrane. 

The industrial use of 1,3-dienes and of their electrophilic reactions has strongly stimulated the field in recent years. Because of the low cost of butadiene, abundantly available from the naphtha cracking process, very large scale applications in the synthesis of polymers, solvents and fine chemicals have been developed, leading to many basic raw materials of the modem chemical industry. For example, the primary steps in the syntheses of acrylonitrile and adiponitrile have been the electrophilic addition of hydrocyanic acid to butadiene24. Chlorination of butadiene was the basis of chloroprene synthesis25. 

The transition metal catalysed addition of HCN to alkenes is potentially a very useful reaction in organic synthesis and it certainly would have been more widely applied in the laboratory if its attraction were not largely offset by the toxicity of HCN. Industrially the difficulties can be minimised to an acceptable level and we are not aware of major accidents. DuPont has commercialised the addition of HCN to butadiene for the production of adiponitrile [ADN, NC(CH2)4CN], a precursor to 1,6-hexanediamine, one of the components of 6,6-nylon and polyurethanes (after reaction with diisocyanates). The details of the hydrocyanation process have not been released, but a substantial amount of related basic chemistry has been published. The development of the ligand parameters % and 0 by Tolman formed part of the basic studies carried out in the Du Pont labs related to the ADN process [1],... 

Hydrogen cyanide is an important building block chemical for the synthesis of a variety of industrially important chemicals, such as 2 hydroxy-4 methylthiobutyric acid, adiponitrile, nitrilotriacetic acid, lactic acid, and methyl methacrylate. The primary commercial routes to hydrogen cyanide are the reaction of methane and ammonia under aerobic (Andrussow Process) or anaerobic conditions (Degussa Process), or the separation of hydrogen cyanide as a by-product of the ammoxidation of propylene < ) The ammoxidation of methanol could represent an attractive alternate route to HCN for a number of reasons. First, on a molar basis, the price of methanol has become close to that of methane as world methanol capacity has increased. However, an accurate long term pricing picture for these two raw... 

Byproducts of large industrial-scale processes are valorized for instance, in the DuPont process for adiponitrile, the byproduct a-methylglutaronitrile is upgraded to p-picoline and further to niacinamide. 

Adiponitrile, a key intermediate in the manufacture of nylon, is made industrially by an electrolytic process that reduces acrylonitrile ... 

The electrohydrodimerisation of acrylonitrile to give adiponitrile (a one-electron process at high substrate concentrations, Scheme 1.8A and Chapter 6) is an example of how an industrially important electrosynthetic process has been investigated following recent instrumental developments, viz. the application of ultramicroelectrodes at low-voltage sweep rates. Use of conventional electrodes would have required substrate concentrations in the mM range but, under these conditions, acrylonitrile undergoes a different reaction - a two-electron electrochemical reduction of the alkene residue (Scheme 1.8B). The switchover between the two reactions occurs at about 1 mol dm-3 substrate concentration. 

Electrochemical reactions may be carried out at any scale from the smallest to the largest and progress in nanotechnology has made it possible to address electron transfer at the single molecule level [26, 27]. Conversions at the laboratory scale are well established and have been addressed by numerous authors [1, 2] and, at the industrial scale, more than 50 electrochemical processes have reached a respectable level with the reductive hydrodimeri-sation of acrylonitrile to adiponitrile topping the list with an annual production of about 300 000 tons [28],... 

The application of electrochemistry in organic synthesis had already served to bring on stream in the United States in 1965 Monsanto s first industrial adiponitrile process from acrylonitrile. This was followed in 1977 by a similar installation in Seal Sands, England, which was later bought up by BASF. 

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