Caprolactam processes

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

In the Hquid-phase process, both benzaldehyde and benzoic acid are recovered. This process was iatroduced and developed ia the late 1950s by the Dow Chemical Company, as a part of their toluene-to-phenol process, and by Snia Viscosa for their toluene-to-caprolactam process. The benzaldehyde recovered from the Hquid-phase air oxidation of toluene may be purified by either batch or continuous distillation. Liquid-phase air oxidation of toluene is covered more fully (see Benzoic acid). 

Caprolactam was first successfully polymerized to Pedon in 1938 by I. G. Farben and the associated technology was acquired as a part of postwar reparations by the Western AUies and the former USSR (1). By 1965 other countries, eg, Italy and Japan, had developed their own caprolactam processes, each involving nitrosation of an aUphatic ring. 

The formation of oxime and rearrangement to caprolactam are conventional. The rearrangement produces 1.5 kg of the total 2.4 kg by-product ammonium sulfate per kilogram of caprolactam. Purification is accompHshed by vacuum distillation. A similar caprolactam process is offered by Inventa (11). 

The most important use of cyclohexanone is as a chemical intermediate in nylon manufacture 97% of all cyclohexanone output is used either to make caprolactam for nylon-6, or adipic acid for nylon-6,6. In the caprolactam process cyclohexanone is converted to cyclohexanone oxime (mp,... 

Two commercial photochemical processes quoted in most texts are the syntheses of caprolactam and vitamin D3. The caprolactam process. 

The ultimate greening of fine chemical synthesis is the replacement of multistep syntheses by the integration of several atom-efficient catalytic steps. For example. Figure 9.9 shows the new Rhodia, salt-free caprolactam process involving three catalytic steps. The last step involves cyclization in the vapor phase over an alumina catalyst in more than 99% conversion and more than 99.5% selectivity. 

The industrial e-caprolactam processes with cyclohexanone oxime as intermediate product were recently reviewed . The catalytic gas-phase Beckmann rearrangement has great industrial interest. Since the process proposed by DuPont in 1938 the investigation on catalytic gas-phase Beckmann rearrangement has been investigated, and a large variety of catalysts have been tested for the reaction. 

Caprolactam is used principally in the production of nylon 6 fibers. In the production of caprolactam, ammonia is used to maintain a reaction pH of 7 in one step, and in another step ammonia is used to neutralize sulfuric acid. Both of these steps result in the production of a low-grade ammonium sulfate fertilizer. In the classical process 5 kg of (NHO2SO4 are produced per kilogram of caprolactam, hi 1992 about 33% of the worldwide caprolactam capacity was based on DSM s caprolactam process that only produces 1.8 kg of (NH SC per kilogram of caprolactam46. 

All commercial caprolactam processes are based on benzene or toluene. These processes employ cyclohexanone, cyclohexane or toluene as starting materials. Large-scale industrial processes are multistage processes in which ammonium sulfate and sometimes organic compounds are formed as byproducts. At least seven processes are used commercially254,266. And each of these processes still has room for improvement. 

The results obtained with the different catalysts indicate that both Ti02 supported on silica and TS-1 perform well. However, TS-1 was the superior catalyst. The Enichem process for this step in the e-caprolactam process greatly simplifies the current technology (Figure 4.7). 

Recently developed caprolactam processes incidence of byproducts significantly reduced... 

In the classical caprolactam process, in which hydroxylamine sulfate produced by the Raschig process and the oxime is rearranged in sulfuric acid, 4.4 t of ammonium sulfate are produced per t caprolactam. In recently developed processes the incidence of byproducts has been significantly reduced or even eliminated. 

To complete the analysis of caprolactam process, it should be also considered how the cyclohexanone is produced, starting from the raw material, which is benzene. 

As a second step, ModKit- - is used to define the flowsheet model of the -caprolactam process, using the imported models from Aspen Plus, gPROMS, and MOREX as building blocks. The flowsheet topology is defined according to Fig. 5.20. The next step concerns the specification of a simulation experiment to be executed by the CHEOPS simulation framework. ModKit-f supports this step by generating a template of an input file for CHEOPS, which contains the necessary information except for the actual values of the feed streams and the parameters of the simulation. These have to be filled in by the user before he finally launches the simulation in CHEOPS. 

Achflladdis, B., A study in technological history, Part U The development of the BASF caprolactam process", Chemistry and Industry (50) 1584-1588 (1970). 

Caprolactam route avoids byproducts", Chem. mi Engng News, 14-L5 (9 April 1973V KANEBO develops sew caprolactam process Ewop. Chem, News, 35 (11 May 1973). 

This is one step in the Stamicarbon caprolactam process whereby the reaction is performed in a phosphate buffer system using a catalyst activator. Overhydrogenation will form ammonium salts and underhydrogenation nitrogen and nitrous oxide. Although not a Fine Chemical example it clearly demonstrates the synergistic effect of platinum on palladium. 

Other variations of the caprolactam process produce hydroxylamine disulfonic acid which is hydrolyzed to hydroxylamine sulfate and an ammonium sulfate by-product. Additional ammonium sulfate is produced downstream in the oximation step by the reaction of ammonia with sulfuric acid. Ammonium sulfate is a low value by-product and there is an advantage to producing hydroxylamine sulfate directly in order to avoid the production of unwanted ammonium sulfate downstream. The oxygen-based NO reduction process provides this advantage and the processes that use it are characterized as low by-product production processes. 

The economics of the oxygen-based NO reduction process is difficult to compare because different caprolactam processes vary so widely. Nevertheless, an early study by Stanford Research Institute (SRI) found that the capital investment for the NO reduction process was about one-half that for the conventional Rashig process. The basis of this comparison included both the hydroxylamine unit as well as the oximation step. Operating costs were not reported, but the conclusion by SRI was that the NO Reduction process offered a decided advantage over the conventional Rashig process [31]. 

KK Ushiba, Caprolactam, Process Economics Program, SRI International (January, 1976). 

An industrial plant using this reaction at 12000t/y has been operated by EniChem since 1994 as part of their new caprolactam process. The conversion and selectivity of the conversion of cyclohexanone exceeds 99% and the... 

Figure 7-2 shows, for example, crystallization of ammonium sulfate from a crude solution, obtained from a caprolactam process, in a three stage evaporation crystallization unit [7.16], The unsaturated crude solution is fed to a crystal washer (1), in which... 

Fig. 7-2. Flow sheet of a three-stage crystallization unit of ammonium sulfate from a crude solution of a caprolactam process.

---