Hexamethylenediamine production

Table 5.1 Comparing alternative production processes - metrics for hexamethylenediamine production (more favorable metrics are shown in bold). Source Schwarz et al. [21],...

Neutrahse about one third of the filtrate with 5N sodium hydroxide and add a further 2 ml. of the alkah solution. Add 1 ml. of benzoyl chloride and stir until the odour of the acid chloride disappears. Collect the solid by suction filtration, wash it with water until free from alkah, and then recrystalhse it from dilute alcohol. The product is the dibenzoyl derivative of hexamethylenediamine and melts at 159°. 

The United States accounts for about a third of the world s consumption of cyclohexane, or 3.785 x 10 m /yr (about 1 biUion gallons per year). U.S. producers and their 1990 capacities are Hsted in Table 13. Texaco has aimounced that it is leaving the cyclohexane business, but the timing is not yet certain. Over 90% of all cyclohexane goes to the production of nylon through either adipic acid (qv) or caprolactam (qv). The balance is used to produce 1,6-hexamethylenediamine [124-09-4] (HMD A) and for various solvent uses (see Diamines and higher amines, aliphatic Polyamides). 

Virtually all the hexamethylenediamine manufactured is used captively in the production of nylon-6,6, with a small amount being used to produce diisocyanates. It is produced via the reduction of adiponittile [111-69-3] (ADN) ... 

In the final step the dinitrile is formed from the anti-Markovrukov addition of hydrogen cyanide [74-90-8] at atmospheric pressure and 30—150°C in the hquid phase with a Ni(0) catalyst. The principal by-product, 2-methylglutaronitrile/4j5 j5 4-ti2-, when hydrogenated using a process similar to that for the conversion of ADN to hexamethylenediamine, produces 2-meth5i-l,5-pentanediamine or 2-methylpentamethylenediamine [15520-10-2] (MPMD), which is also used in the manufacture of polyamides as a comonomer. 

Polymer Production. Three processes are used to produce nylon-6,6. Two of these start with nylon-6,6 salt, a combination of adipic acid and hexamethylenediamine in water they are the batch or autoclave process and the continuous polymerisation process. The third, the soHd-phase polymerisation process, starts with low molecular weight pellets usually made via the autoclave process, and continues to build the molecular weight of the polymer in a heated inert gas, the temperature of which never reaches the melting point of the polymer. 

Hexamethylenediamine [124-09-4] and adipic acid [124-04-9] are used in the commercial production of nylon-6,6 and S-caprolactam [105-60-2] is used for nylon-6 (see also Adipic acid Caprolactam). 

The manufacture of hexamethylenediamine [124-09-4] a key comonomer in nylon-6,6 production proceeds by a two-step HCN addition reaction to produce adiponittile [111-69-3] NCCH2CH2CH2CH2CN. The adiponittile is then hydrogenated to produce the desired diamine. The other half of nylon-6,6, adipic acid (qv), can also be produced from butadiene by means of either of two similar routes involving the addition of CO. Reaction between the diamine and adipic acid [124-04-5] produces nylon-6,6. 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

Nylon 66 is produced by the reaction of hexamethylenediamine and adipic acid (see Chapters 9 and 10 for the production of the two monomers). This produces hexamethylenediammonium adipate salt. The product is a dilute salt solution concentrated to approximately 60% and charged with acetic acid to a reactor where water is continuously removed. The presence of a small amount of acetic acid limits the degree of polymerization to the desired level ... 

Nylon 66 was the first polyamide to be produced commercially. Developed by Wallace Carothers at the DuPont Chemical Company In 1935, it still leads the polymer industry in annual production. Figure 13-7 illustrates that Nylon 66, made from adipic acid and hexamethylenediamine, is so easy to make that it is often used for a classroom demonstration ... 

Adiponitrile is readily hydrogenated catalytically to hexamethylenediamine, which is an important starting material for the prodnction of nylons and other plastics. The electrochemical production of adiponitrile was started in the United States in 1965 at present its volume is about 200 kilotons per year. The reaction occurs at lead or cadmium cathodes with current densities of np to 200 mA/cm in phosphate buffer solutions of pH 8.5 to 9. Salts of tetrabntylammonium [N(C4H9)4] are added to the solution this cation is specihcally adsorbed on the cathode and displaces water molecules from the first solution layer at the snrface. Therefore, the concentration of proton donors is drastically rednced in the reaction zone, and the reaction follows the scheme of (15.36) rather than that of (15.35), which wonld yield propi-onitrile. 

This chapter reports about an investigation on the catalytic gas-phase armnoxidation of u-hexane aimed at the production of 1,6-Ce dinitriles, precursors for the synthesis of hexamethylenediamine. Catalysts tested were those also active and selective in the ammoxidation of propane to aciylonitrile mtile-type V/Sb and SnA /Nb/Sb mixed oxides. Several A-containing compounds formed however, the selectivity to cyano-containing aliphatic linear Ce compounds was low, due to the relevant contribution of side reactions such as combustion, cracking and formation of heavy compounds. 

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. 

Hexamethylenediamine (HMD) and adiponitrile (ADN) are formed from Nylon-6,6, while 6-aminocapronitrile (ACN) and caprolactam (CL) are formed from Nylon-6. The ammonolysis product, which also contains many minor byproduct components, is fractionated by distillation with the HMD, ACN, ADN, and CL in one fraction. This fraction is subsequently hydrogenated to form HMD. Caprolactam remains intact during the hydrogenation reaction. 

The hydrogenation products from the continuous run using Raney Co 2724 were subsequently distilled and the product hexamethylenediamine monomer (i.e. recycled HMD ) 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, indicating that the continuous hydrogenation of ammonolysis product offers potential for the commercial production of recycled Nylon. 

When the reactants involved in a step growth polymerization process are mutually immiscible, we can employ an interfacial polymerization method. Two solutions, each containing one of the monomers, are layered one on top of the other. This creates a phase boundary that forms wth the least dense liquid on top. The different monomers can then meet and polymerize at the interface. A commonly demonstrated example of this is the manufacture of nylon 610 by the interfacial reaction between an aqueous solution of hexamethylenediamine with sebacoyl chloride dissolved in carbon tetrachloride. Because the reaction only occurs at the interface, it is possible to pull the products from this interface to isolate the final product. 

Butadiene, the simplest conjugated diene, appears to be a promising substrate for the hydroformylation reaction, because the expected product (hexanedial) could be easily converted to useful products. Oxidation would produce adipic acid, hydrogenation hexanediol, and reductive amination hexamethylenediamine. However, this objective has been difficult to realize. 

Du Pont. Product Description Hexamethylenediamine (Wilmington, DE Du Pont de Nemours, 1999c). 

Carothers next step was to move from polyesters to nylons and to increase the fractional conversion (p) by making salts using the equivalent reaction of 1,6-hexanediamine (hexamethylenediamine) and adipic acid. These salts were recrystallizable from ethanol giving essentially a true 1 1 ratio of reactants. Thus, a high molecular weight polyamide, generally known as simply a nylon, in this case nylon-6,6, was produced from the thermal decomposition of this equimolar salt as shown in structure 4.55. This product has a melting point of 265°C. 

---