Caprolactam, manufacture

Nylon-12. Laurolactam [947-04-6] is the usual commercial monomer for nylon-12 [24937-16-4] manufacture. Its production begins with the mixture of cyclododecanol and cyclododecanone which is formed in the production of dodecanedioic acid starting from butadiene. The mixture is then converted quantitatively to cyclododecanone via dehydrogenation of the alcohol at 230—245°C and atmospheric pressure. The conversion to the lactam by the rearrangement of the oxime is similar to that for caprolactam manufacture. There are several other, less widely used commercial routes to laurolactam (171). 

A small amount of adipic acid, 2%, is made by hydrogenation of phenol with a palladium or nickel catalyst (150°C, 50 psi) to the mixed oil, then nitric acid oxidation to adipic acid. If palladium is used, more cyclohexanone is formed. Although the phenol route for making adipic acid is not economically advantageous because phenol is more expensive than benzene, the phenol conversion to greater cyclohexanone percentages can be used successfully for caprolactam manufacture (see next section), where cyclohexanone is necessary. 

Although the phenol route for making adipic acid is not economically advantageous because phenol is more expensive than benzene, the phenol conversion to greater cyclohexanone percentages can be used successfully for caprolactam manufacture, where cyclohexanone is necessary. 

All caprolactam manufacturers use sulfuric acid or oleum as a rearrangement medium. The rearrangement is more complete in concentrated sulfuric acid. Excess sulfur trioxide further increases the speed of the rearrangement. This step is based on chemistry that was discovered by E. Beckmann in 1886 [see Eq. 21.8)]. Commercial development of this process was carried out by BASF46,264. 

The hydroxylamine content in this solution, which also contains ammonium sulfate, is ca. 70g/L. In an integrated caprolactam manufacturing plant using the Raschig process for hydroxylamine production, ca. 1.8 kg of ammonium sulfate is produced per kg of caprolactam. 

Not only strong acid sites but also relatively weak acid sites could be utilized in the development of improved industrial processes. One of the most significative examples is the new Sumitomo process for caprolactam manufacture, which combines a first step of ammoximation (originally developed by the Eni group [241-243]) with a second step of Beckmann rearrangement based on the use of silicalite-1 (Eigure 2.32). 

Figure 2.32 Commercial (a) versus Sumitomo (b) process for caprolactam manufacture.

Figure 2.35 Reaction scheme of current routes of caprolactam manufacturing process.

In conclusion, a correct analysis of the sustainability in caprolactam manufacture should consider the full scheme of production and the alternatives, including the critical steps to be further developed. 

About 15< o of the caprolactam manufactured worldwide is used to produce engineering resins. This is currently the highest growth segment. About 80synthetic fibers market. The balance of about 5% is used for specialty organic synthesis [31]. 

Leaving the Byproduct Ammoruum Sulfate Out of Caprolactam Manufacture. 1977. Nitrogen, 108 33-36. 

Bodanyl n. Poly(caprolactam). Manufactured by Feldmiihle, Rorschach, Switzerland. 

Ammonia. Ammonia oxidation yields two very important products, hydrazine and hydroxylamine, the latter of particular importance in caprolactam manufacture. 

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