Dehydration adiponitrile

The reaction of adipic acid with ammonia in either Hquid or vapor phase produces adipamide as an intermediate which is subsequentiy dehydrated to adiponitrile. The most widely used catalysts are based on phosphoms-containing compounds, but boron compounds and siHca gel also have been patented for this use (52—56). Vapor-phase processes involve the use of fixed catalyst beds whereas, in Hquid—gas processes, the catalyst is added to the feed. The reaction temperature of the Hquid-phase processes is ca 300°C and most vapor-phase processes mn at 350—400°C. Both operate at atmospheric pressure. Yields of adipic acid to adiponitrile are as high as 95% (57). 

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 ... 

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,... 

Ammonium adipate and adipamide are formed as intermediates, which are dehydrated to adiponitrile by means of the catalyst... 

The commercial diamines used for nylon manufacture are usually best made by hydrogenation of the corresponding dinitriles. Hexamethylene-diamine is made by hydrogenation of the adiponitrile. Adiponitrile is now commercially produced by several methods. In the oldest method, ammonium adipate was catalytically dehydrated to the dinitrile. In a method developed since World War II, butadiene is treated with chlorine to produce mixture of dichlorobutenes. Reaction with hydrogen cyanide in the prewnce of cuprous halides yields l,4-dicyanobutene-2 exclusively. Hy-dn enation produces adiponitrile. 

Adiponitrile in turn is obtained from processes starting from (a) adipic acid, (b) butadiene, and (c) acrylonitrile. The process starting from adipic add (process 7 in Figure 2.13) is rather well developed and used by most of the major raw material suppliers. It consists of a gas-phase reaction between adipic acid and ammonia at about 270°C at atmospheric pressure. In the presence of dehydration catalysts, such as phosphonic acid or a mixture of phosphoric and boric acids, the reaction proceeds via the formation of adipic add amide to adiponitrile with about 90% yield. 

The major nitrile products produced in addition to acrylonitrile, HCN, and acetonitrile have significant commercial value in their own right. HCN is used mainly in the manufacture of methyl methacrylate. Methyl methacrylate is prepared by acid dehydration and methanol esterification of acetone cyanohydrin produced from the reaction of HCN and acetone. HCN is also a feedstock for the production of methionine, an important animal feed supplement, and is used to produce pesticides and herbicides. For example, HCN is utilized to manufacture disodium iminodiacetate, which is a key intermediate in the production of the widely used herbicide Roundup (Monsanto Co., St. Louis U.S.A.). It is also valuable as a feedstock for the production of adiponitrile by the hydrocyana-tion of butadiene. Adiponitrile is a feedstock for the manufacture of Nylon. In... 

Nylon 6,6. Phenol is hydrogenated, or cyclohexane is cata-lytically oxidized with air, and the resulting cyclohexanol is oxidized to adipic acid. Dehydration of ammonium adipate then yields adiponitrile, which is hydrogenated to hexamethylenediamine. Equivalent amounts... 

Dehydration of amides is often carried out in the presence of ammonia. Acetonitrile, adiponitrile, and 6-aminocaprolactam ° are formed from acetamide, adipic acid and E-aminocaprolactam over MgiPiO , phosphoric acid supported on silica, and MgHP04, respectively in high yields. o-Chloronitrile can be produced from o-chlorobenzoic acid or its amide over alumina around 623... 

In the first process adipic acid was converted to adiponitrile by a high temperature reaction with ammonia over a boron phosphate catalyst at temperatures in the range 300-350°C. The process was thought to proceed via the formation of diammonium adipate, followed by dehydration to adiponitrile ... 

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