Hydrogen of adiponitrile

The main route for the production of hexamethylene diamine is the liquid-phase catalyzed hydrogenation of adiponitrile ... 

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. 

Solutia has been producing hexamethylenediamine via low pressure slurry hydrogenation of adiponitrile since 1973. This process can also been adapted for the production of other amines such as DMAPA. The catalyst employed for... 

A process for the hydrogenation of adiponitrile and 6-aminocapronitrile to hexamethylenediamine in streams of depolymerized Nylon-6,6 or a blend of Nylon-6 and Nylon-6,6 has been described. Semi-batch and continuous hydrogenation reactions of depolymerized (ammonolysis) products were performed to study the efficacy of Raney Ni 2400 and Raney Co 2724 catalysts. The study showed signs of deactivation of Raney Ni 2400 even in the presence of caustic, whereas little or no deactivation of Raney Co 2724 was observed for the hydrogenation of the ammonolysis product. The hydrogenation products from the continuous run using Raney Co 2724 were subsequently distilled and the recycled hexamethylenediamine (HMD) monomer was polymerized with adipic acid. The properties of the polymer prepared from recycled HMD were found to be identical to that obtained from virgin HMD. 

More recently, dihydrogen complexes have been patented for nitrile hydrogenation. For example, the complex Ru(7/2-H2)2(H)2(PCy3)2 (Fig. 3.6) catalyzes the hydrogenation of adiponitrile to hexamethylenediamine (HMD) in toluene at 90 °C, 70 bar H2 with TON 52, TOF 5 IT1 [68]. At intermediate conversions, the... 

Adipic acids gets converted to adiponitrile on treatment with NH3 at 350-450°C in presence of boron phosphate catalyst. Hydrogenation of adiponitrile can be done in presence of NH3 to Organisation and Qualities... 

Hexanediamine can also be obtained by the liquid phase catalytic hydrogenation of adiponitrile or adipamide, which is made from adipic acid. 

Hexamethylenediamine, 1,6 Hexanediamine (HMDA). H2N(CH2) NH2 mw 116.24, N 24.10% silk-like leaves, mp 42° bp 205° (subl), sol in water si sol in h eth. Prepd by hydrogenation of adiponitrile over Raney Ni or Co chlorination of butadiene then reactn with NaCN hydrogenation. Acute local irritant-mod flame hazard. Used in high polymer synth as a cross-linking agent (Refs 1, 3 4)... 

Adiponitrile. Adiponitrile is an important intermediate in polyamide manufacture. 1,6-Hexamethylenediamine formed by the hydrogenation of adiponitrile is used in the production of nylon-6,6, one of the most important polyamides in commercial production. 

The synthesis of l-aza-l-cyeloheptene and the study of its reactivity allows us to propose this compound as an important intermediate for the generation of secondary amines in the course of the catalytic hydrogenation of adiponitrile to hexamethylene diamine. 

Extraction and distillation is necessary to obtain pure adiponitrile. Even then the hexamethylenediamine made by hydrogenation of adiponitrile must also be distilled through seven columns to purify it before polymerization to nylon. Hexamethylenediamine is produced from adiponitrile by hydrogenation. 

C before use. The catalyst was used for the hydrogenation of adiponitrile and stearonitrile to the corresponding primary amines in high yields.94,95... 

Excellent yields (93-97%) of 1,6-hexanediamine were obtained in the hydrogenation of adiponitrile over Raney Co (eq. 7.24), Co-A1203 (Raney type), and Co-kieselguhr as catalysts with addition of ammonia.22 The yields decreased from 97.2 to 93.1% in the absence of ammonia and from 93 to 77% with nickel catalyst in place of cobalt catalyst. 

The byproducts of the hydrogenation of adiponitrile are small amounts of hexahydroazepine, 1,2-diaminocyclohexane and 2-(aminomethyl)cyclopentylamine, besides acyclic secondary products. In an example of a continuous process, a 1 12.5 molar ratio of adiponitrile and ammonia that was mixed with 10-fold amount of a hydrogenated reaction mixture from a prior run to give a 1 44 adiponitrile-ammonia mixture... 

Scheme 7.2 The formation pathways of the carbocyclic byproducts in the hydrogenation of adiponitrile.

Currently the global production of hexamethylenediamine exceeds 1.2 Mt/a and production (e.g. ICI, BASF and Rhone-Poulenc in Europe) is based on the hydrogenation of adiponitrile, largely obtained by catalytic addition of HCN to butadiene. Celanese produced hexamethylenediamine by reaction of ammonia with hexane-1,6-diol, coming from the hydrogenation of adipic acid. However, production by this method was abandoned in 1984. 

The hydrogenation of adiponitrile has additional complications in some kinetic studies 6-aminohexanonitrile was detected in solution and is considered a reaction intermediate (Figure 9). Alternatively, it may be a by-product if the hydrogenation is incomplete. Furthermore, the addition of the amines to the imine intermediates leads to an increased number of possible by-products, including cyclic compounds, due to the bifunctional character of the substrate. 

Raney nickel is the most commonly used catalyst for the hydrogenation of adiponitrile and seems to be the only one now employed in industry. It is more active and less expensive than the Raney cobalt previously used. 

Figure 9 The hydrogenation of adiponitrile, an a,(n-dinitrile, to hexamethylenediamine via 6-aminohexanonitrile.

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. 

Hexamethylene diamine (mp=42°C bpl 013 = 204oC) is obtained by the catalytic hydrogenation of adiponitrile or through 1,6-hexanediol as an intermediate. 

Table 3 shows the activity data for the trickle phase hydrogenation of adiponitrile (ADN) at the LHSV of 1.03 and 0.26. The Co hollow spheres were far more active than the Co tablets on both a weight and volume basis due to the increased porosity of the hollow spheres. Adding Cr and Ni dopants to the Co / Al alloy did not change the activity of the Co hollow spheres, however preadsorbing LiOH on the Cr and Ni doped Co hollow spheres did increase its activity at the LHSV h" of... 

Activated hollow spheres have been found to be advantageous for the hydrogenation of carbonyl compounds, nitriles, aromatics, and unsaturated C-C bounds. In the case of carbonyl conqrounds, promoters (e.g.. Mo and Cr) that exist as surface cations were found to be the most effective. In the case of nitriles, the use of promoters to stabilize the residual A1 content of the catalyst so that it can be used with base modifiers was found to be the most useful combination. An example of this was the improved performance of the LiOH treated Cr / Ni promoted Co hollow spheres for the hydrogenation of adiponitrile to hexamethylenediamine. Some reactions were found to be more sensitive to the type of promoter they require. In the case of l,4-dihydroxy-2-butyne, it was found that Mo worked satisfactory as a promoter while the Cr / Fe combination led to worse results. Nonetheless, for all of the reactions studied here it was found that the activate hollow spheres were more active than the activated tablets on both a volume and weight basis, thereby allowing increased flexibility in the use of promoters and other selectivity enhancing additives. 

Catalytic sites of formation of DCH seemed to be specific and rather reactive. They were easily deactivated or poisoned. The addition of sodium carboxylates (5% of nickel surface coverage) lowered the 1,2-DCH formation by 40% during the hydrogenation of adiponitrile without any loss of activity (semibatch test). 

In the case of the hydrogenation of adiponitrile we have shown that cyclic and linear secondary imines are in equilibrium through a transimina-tion reaction (8). 

The relative rate of formation of the impurity comparatively to the rate of formation of the corresponding diamine (vficArfdiamine) at iso conversion. For each impurity, we fixed arbitrarily this ratio equal to 1 for the hydrogenation of adiponitrile. When this ratio is 0 this by-product has not been detected by gas chromatography that means its content is less than 100 ppm. 

The production of diamines, both aliphatic and aromatic, has become of increasing importance during recent years. Hexamethylenediamine, produced by catalytic hydrogenation of adiponitrile, is an essential component in the manufacture of nylon 66. This step in the synthesis of hexamethylenediamine may be represented as follows ... 

---