Caprolactam Beckmann rearrangement

Ingredients. Nylon-6 is produced commercially from caprolactam [105-60-2] which is the most important lactam industrially. AH industrial production processes for caprolactam are multistep and produce ammonium sulfate [7783-20-2] or other by-products. Approximately 95% of the world s caprolactam is produced from cyclohexanone oxime [100-64-1] via the Beckmann rearrangement (144). The starting material for cyclohexanone can be... 

Cyclohexanone oxime is converted quantitatively to caprolactam by Beckmann rearrangement in the presence of oleum, which is of sufficient strength to consume the several percent water in the molten oxime. The reaction mass is neutralized with aqueous ammonia to a cmde caprolactam layer and a saturated solution of ammonium sulfate. Approximately 1.5 kg of the total 4.4 kg ammonium sulfate per kilogram of caprolactam is produced in this step. Purification is by multistage vacuum crystallization from aqueous solution in neatly quantitative yield. 

The oxime is converted to caprolactam by Beckmann rearrangement neutralization with ammonia gives ca 1.8 kg ammonium sulfate per kilogram of caprolactam. Purification is by vacuum distillation. A no-sulfate, extraction process has been described, but incineration of the ammonium bisulfate recovers only sulfur values and it is not practiced commercially (14). 

Toray. The photonitrosation of cyclohexane or PNC process results in the direct conversion of cyclohexane to cyclohexanone oxime hydrochloride by reaction with nitrosyl chloride in the presence of uv light (15) (see Photochemical technology). Beckmann rearrangement of the cyclohexanone oxime hydrochloride in oleum results in the evolution of HCl, which is recycled to form NOCl by reaction with nitrosylsulfuric acid. The latter is produced by conventional absorption of NO from ammonia oxidation in oleum. Neutralization of the rearrangement mass with ammonia yields 1.7 kg ammonium sulfate per kilogram of caprolactam. Purification is by vacuum distillation. The novel chemistry is as follows ... 

The conversion of cyclohexanone to cyclohexanone oxime is brought about by the use of hydroxylamine sulphate. The sulphuric acid is neutralised with ammonia to ammonium sulphate and this is separated from the oxime. In the presence of oleum the oxime undergoes the process known as the Beckmann rearrangement to yield the crude caprolactam. After further neutralisation with ammonia the caprolactam and further ammonium sulphate are separated by solvent extraction (Figure 18.7). 

A regio- and stereoselective Beckmann rearrangement utilized diastereose-lective host guest interactions of the inclusion complexes 225 and 228 in a solid state reaction. Initially, a 1 1 mixture of the chiral host 223 and the racemic oximes 224 and 227, respectively, was treated with ultra sound in the solid state to induce the optical resolution. Then H2SO4 was added to start the Beckmann rearrangement, the corresponding c-caprolactams 226 and 229 were isolated in 68 % and 64 % yields and ee of about 80 % and 69 % (determined by HPLC analysis on chiracel OC) (Scheme 43) [46]. 

Zeolites have also been described as efficient catalysts for acylation,11 for the preparation of acetals,12 and proved to be useful for acetal hydrolysis13 or intramolecular lactonization of hydroxyalkanoic acids,14 to name a few examples of their application. A number of isomerizations and skeletal rearrangements promoted by these porous materials have also been reported. From these, we can underline two important industrial processes such as the isomerization of xylenes,2 and the Beckmann rearrangement of cyclohexanone oxime to e-caprolactam,15 which is an intermediate for polyamide manufacture. Other applications include the conversion of n-butane to isobutane,16 Fries rearrangement of phenyl esters,17 or the rearrangement of epoxides to carbonyl compounds.18... 

This, on treatment with sulfuric acid, then undergoes the Beckmann rearrangement to caprolactam. The nitrosyl chloride is made by reacting nitrosyl sulfuric acid (made from oxides of nitrogen and sulfuric acid) with hydrogen chloride gas ... 

The transformation of oximes to lactams (the Beckmann rearrangement) was one of the earliest such acid-catalyzed reactions to be reported with TS-1 (138) and TS-2 (247) catalysts. The rearrangement of cyclohexanone oxime to e-caprolactam proceeds with high selectivity in the presence of TS-1, with high catalyst stability (138,247). 

It can be obtained from cyclohexane. Cyclohexane is air oxidised to yield a mixture of cyclohexanol and cyclohexanone. Cyclohexanol is dehydrogenated to cyclohexanone over copper catalyst. Cyclohexanone when treated with hydroxylamine sulphate at 20°-95°C gives an oxime. The oxime when treated with concentrated sulphuric acid undergoes Beckmann rearrangement to yield caprolactam. 

The common name caprolactam comes from the original name for the Ce carboxylic acid, caproic acid. Caprolactam is the cyclic amide (lactam) of 6-aminocaproic acid. Its manufacture is from cyclohexanone, made usually from cyclohexane (58%), but also available from phenol (42%). Some of the cyclohexanol in cyclohexanone/cyclohexanol mixtures can be converted to cyclohexanone by a ZnO catalyst at 400°C. Then the cyclohexanone is converted into the oxime with hydroxylamine. The oxime undergoes a very famous acid-catalyzed reaction called the Beckmann rearrangement to give caprolactam. Sulfuric acid at 100-120°C is common but phosphoric acid is also used, since after treatment with ammonia the by-product becomes... 

Perhaps the most notable application of the Beckmann rearrangement is in the industrial production of 8-caprolactam from cyclohexanone (or its oxime), which is used as monomer for the polymerization to a polyamide for the production of synthetic fibres (for example, nylon 6). Furthermore, Beckmann rearrangement provides a facile route for the... 

The production of the nylon precursor e-caprolactam via the Beckmann rearrangement is one of the largest industrial processes worldwide. There are a large number of synthetic routes to e-caprolactam, most of which need to be improved because, without exception, all are multistage processes that produce large amounts of by-products, primarily ammonium sulfate. Due to its industrial application, the improvement of the Beckmann rearrangement of e-caprolactam was the aim of several smdies and a lot of scientific papers, patents and book chapters have been published on this topic during the last century. 

The classical production of e-caprolactam is based on cyclohexanone oxime and on its Beckmann rearrangement. For this step, aU manufacmrers use fuming sulfuric acid or oleum, sometimes enriched with more sulfur trioxide than present anyway in the oleum, to increase the rate of the rearrangement process. 

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. 

The deactivation and regeneration of the catalyst are also important processes in the industrial production of the caprolactam by the Beckmann rearrangement and have been... 

Recently, the Sumitomo Chemical Co., Ltd. developed the vapour-phase Beckmann rearrangement process for the production of 8-caprolactam. In the process, cyclohexanone oxime is rearranged to e-caprolactam by using a zeolite as a catalyst instead of sulfuric acid. EniChem in Italy developed the ammoximation process that involves the direct production of cyclohexanone oxime without producing any ammonium sulfate. The Sumitomo Chemical Co., Ltd. commercialized the combined process of vapour-phase Beckmann rearrangement and ammoximation in 2003 ". 

Apart from the uses in the production of e-caprolactam, the Beckmann rearrangement has been used industrially in the synthesis of various APIs (Active Pharmaceutical Ingredient) or other compounds with economical value (essentially monomers for the production of polymers). A survey of the bulk reaction scaled in the GMP facilities at... 

Gui et reported the Beckmann rearrangement of ketoximes using a sulfonyl chloride-containing imidazolium-based TSIL to furnish s-caprolactam, which was immiscible in the IL, resulting in easy separation. Similar ILs were... 

Alternative purification protocols are available. Zhaolin Sun of Lanzhou University reports (Tetrahedron Lett. 45 2681,2004) that the ionic liquid TISC was specifically designed to promote Beckmann rearrangement. TISC is not soluble in water, so the product caprolactam was easily removed from the ionic liquid by extraction with water. 

The yield of cyclohexanone is estimated at about 867r by weight. Then, in a Beckmann rearrangement, the cyclohexanone oxime hydrochloride is convened to 6-caprolactam ... 

It has been described the reaction of cyclohexanone oxime with solids of different nature, as zeolites (refs. 4 and 5) and aluminum phosphates (ref. 6), giving rise to the Beckmann rearrangement product, E-caprolactame when the reactions are carried out in the gas phase at relatively high temperatures (>300°C). 

The synthesis of aza-2-cycloheptanone (e-caprolactam) by the Beckmann rearrangement of the oxime of cyclohexanone is of commercial importance because the lactam is an intermediate in the synthesis of a type of nylon (a polyamide called nylon-6 2) ... 

Nylon 6 can be prepared by polymerization of l-aza-2-cycloheptanone (e-caprolactam), obtained through the Beckmann rearrangement of cyclohexanone oxime (Section 24-3C) ... 

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