Caprolactam alternative process

An alternative route to cyclohexanone oxime developed in Italy by Enichem is shown in the following reaction. Cyclohexanone oxime is produced by the ammoxidation of cyclohexanone with ammonia and aqueous hydrogen peroxide in the presence of a solid, recyclable catalyst, titanium silicalite (TS-1). This reaction step eliminates approximately one-third of total salt formation. However, the oxime is still converted to caprolactam through the conventional route (Beckmann rearrangement), catalyzed by stoichiometric amounts of sulfuric acid, and produces ammonium sulfate salt. Therefore, this alternative process still leaves something to be desired. 

The scope of this paper does not permit a detailed description of the caprolactam development. A competent, readable review, however, is available on this subject [20]. This deals also with later improvements by BASF and with alternative processes developed by other companies. 

With the advent of petrochemistry, BASF gradually replaced phenol by cyclohexane as the starting material. Development of a new continuous caprolactam process based on cyclohexane was started by BASF in 1950, and a full-scale plant went on stream in 1960 [20]. Similar processes based on cyclohexane were developed by DSM, Bayer and Inventa. A number of alternative processes were developed by other companies (Fig. 3). To name only some of them the cumene/phenol based process of Allied (on stream in 1958), the photonitrosation process of Toyo Rayon (1962), the toluene based Snia process (1964), and DuPont s nitrocyclohexane process (in operation from 1961 to 1966). 

Among the industrially produced lactams, e-caprolactam has by far the highest production capacity due to its important role as monomer in the polyamide business. There exist several synthetic routes to produce e-caprolactam. The most important one starts from benzene (Scheme 5.3.7). Benzene is hydrogenated in a first step to cyclohexane, followed by oxidation of the latter to a mixture of cyclohexanone and cydohexanol. This mixture is then reacted with NH2OH to give cyclohexanone oxime, which is converted under add catalysis in a so-called Beckmann rearrangement reaction to e-caprolactam. Alternative routes try to avoid the oxime intermediate (UCC peracetic add process via e-caprolactone), try to avoid the cydohexanone intermediate (e.g., DuPont process converting cydohexane directly into the oxime intermediate by reaction with nitric add), or start from toluene (Snia-Viscosa process). 

Since adipic acid has been produced in commercial quantities for almost 50 years, it is not surprising that many variations and improvements have been made to the basic cyclohexane process. In general, however, the commercially important processes stiU employ two major reaction stages. The first reaction stage is the production of the intermediates cyclohexanone [108-94-1] and cyclohexanol [108-93-0], usuaHy abbreviated as KA, KA oil, ol-one, or anone-anol. The KA (ketone, alcohol), after separation from unreacted cyclohexane (which is recycled) and reaction by-products, is then converted to adipic acid by oxidation with nitric acid. An important alternative to this use of KA is its use as an intermediate in the manufacture of caprolactam, the monomer for production of nylon-6 [25038-54-4]. The latter use of KA predominates by a substantial margin on a worldwide basis, but not in the United States. 

Direct use of dimethyl adipate from the oxycarbonylation process to produce nylon 6,6 could be an attractive alternative to current adipic acid/nylon 6,6 technology. Dimethyl adipate condensation with hexamethylene diamine would give methanol rather than water. Reactors, which currently use caprolactam to prepare nylon 6, could also easily be retrofitted to produce nylon 6,6. Dimethyl hex- nedioate or dimethyl adipate are also useful raw materials for preparation of other high volume chemicals including hexamethylene diamine, caprolactam, and 1, -hexanediol. 

The TS-l catalyzed hydroxylation of phenol to a 1 1 mixture of catechol and hydroquinone has already been commercialized by Enichem. Another reaction of considerable commercial importance is the above mentioned ammoximation of cyclohexanone to cyclohexanone oxime66, an intermediate in the manufacture of caprolactam. It could form an attractive alternative to the established process that involves a circuitous route via oxidation of ammonia to nitric acid followed by reduction of the latter to hydroxylamine (figure 4). 

Another process is the conversion of toluene into caprolactam that provides an alternative basic building block for this chemical other than benzene. Toluene is oxidized to benzoic acid, and hydrogenation to cyclohexanecar-boxylic acid is followed by treatment with nitrosylsulfuric acid to form cyclohexanone oxime followed by rearrangement to caprolactam. 

Process Economics Program Report SRI International. Menlo Park, CA, Isocyanates IE, Propylene Oxide 2E, Vinyl Chloride 5D, Terephthalic Acid and Dimethyl Terephthalate 9E, Phenol 22C, Xylene Separation 25C, BTX, Aromatics 30A, o-Xylene 34 A, m-Xylene 25 A, p-Xylene 93-3-4, Ethylbenzene/Styrene 33C, Phthalic Anhydride 34B, Glycerine and Intermediates 58, Aniline and Derivatives 76C, Bisphenol A and Phosgene 81, C1 Chlorinated Hydrocarbons 126, Chlorinated Solvent 48, Chlorofluorocarbon Alternatives 201, Reforming for BTX 129, Aromatics Processes 182 A, Propylene Oxide Derivatives 198, Acetaldehyde 24 A2, 91-1-3, Acetic Acid 37 B, Acetylene 16A, Adipic Acid 3 B, Ammonia 44 A, Caprolactam 7 C, Carbon Disulfide 171 A, Cumene 92-3-4, 22 B, 219, MDA 1 D, Ethanol 53 A, 85-2-4, Ethylene Dichloride/Vinyl Chloride 5 C, Formaldehyde 23 A, Hexamethylenediamine (HMDA) 31 B, Hydrogen Cyanide 76-3-4, Maleic Anhydride 46 C, Methane (Natural Gas) 191, Synthesis Gas 146, 148, 191 A, Methanol 148, 43 B, 93-2-2, Methyl Methacrylate 11 D, Nylon 6-41 B, Nylon 6,6-54 B, Ethylene/Propylene 29 A, Urea 56 A, Vinyl Acetate 15 A. 

In classical processes cyclohexanone is converted to the corresponding oxime by reaction with hydroxylamine (see Fig. 2.27). The oxime subsequently affords caprolactam via the Beckmann rearrangement with sulphuric or phosphoric acid. Alternatively, in a more recent development, not yet commercialized, a mixture of cyclohexanone, ammonia and hydrogen peroxide is directly converted to cyclohexanone oxime over a titanium(IV)-silicalite (TS-1) catalyst. This route is more direct than the classical route and reduces the amount of salt formation but it involves the use of a more expensive oxidant (H2O2 rather than O2). 

Alternatively, caprolactam can be produced from butadiene, via homogeneous nickel-catalysed addition of HCN (DuPont process) followed by selective catalytic hydrogenation of the adiponitrile product to the amino nitrile and vapor phase hydration over an alumina catalyst (Rhodia process) as shown in Fig. 1.49 [137]. 

L-Lysine, an essential amino acid, is used in very large quantities to supplement human foods and animal feeds. Traditionally, L-Lysine is produced by fermentation processes. An alternative route developed by Toray Ind. involves the chemical synthesis of D/L-a-amino-s-caprolactam followed by the selective hydrolysis of the L-a-amino-s-caprolactam catalyzed by intracellular lactamase in Cryptococcus laurentii, to give L-Lysine. The process can be improved by adding a second micro-organism, Achromobacter obae, containing a-amino-E-caprolactam racemase.Thus, quantitative yields of L-lysine are obtained. 

Since its discovery some 55 years ago, the synthesis of caprolactam has been the subject of intense research and development. Interest in alternative routes continues today and current activities receiving a lot of attention are carbon monoxide-based routes under development by DSM, EniChem and DuPont [32]. Numerous routes using a variety of feedstocks have been patented and many have been piloted, however, only seven have actually been commercialized. The first was the process developed by I. G. Farben based on Schlack s chemistry known today as the Rashig or conventional route. Other commercial routes are the CAPROPOL process, the BASF process, the DSM-HPO process, the Allied process, the Toray PNC process, and the SNIA Viscosa process. 

Over 500 different a-amino acids have now been synthesized or isolated. About 20 of them form the main components of proteins (see also Chapter 30). a-Amino acids are commerically obtained by fermentation of glucose (arg, asp, gin, glu, his, ile, lys, pro, val, thr) or glycine (ser), or enzymatic attack on aspartic acid (ala) or fumaric acid (asp), by hydrolysis, for example, of casein or sugar beet waste (arg, cys, his, hyp, leu, tyr), by transformation of ornithine (arg) or glutamic acid (gin), or, alternatively, by complete synthesis from aldehydes using the Strecker synthesis (ala, gly, leu, met, phe, thr, trp, val), from acrylonitrile (gly, lys), or from caprolactam (lys). The racemates are obtained by total synthesis, but L-amino acids are produced by all the other processes. The racemates are separated and the D-isomers produced are again racemized. 

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