Phenol from cyclohexane

Halcon (1) Halcon International (later The Halcon SD Group) designed many organic chemical processes, but is perhaps best known for its process for making phenol from cyclohexane. Cyclohexane is first oxidized to cyclohexanol, using air as the oxidant and boric acid as the catalyst, and this is then dehydrogenated to phenol. Invented in 1961 by S. N. Fox and J. W. Colton, it was operated by Monsanto in Australia for several years. 

A route to phenol has been developed starting from cyclohexane, which is first oxidised to a mixture of cyclohexanol and cyclohexanone. In one process the oxidation is carried out in the liquid phase using cobalt naphthenate as catalyst. The cyclohexanone present may be converted to cyclohexanol, in this case the desired intermediate, by catalytic hydrogenation. The cyclohexanol is converted to phenol by a catalytic process using selenium or with palladium on charcoal. The hydrogen produced in this process may be used in the conversion of cyclohexanone to cyclohexanol. It also may be used in the conversion of benzene to cyclohexane in processes where benzene is used as the precursor of the cyclohexane. 

About half of the nylon made in the world is made from the polymerization of caprolactam. Although the cyclohexanone needed to make caprolactam can be made from cyclohexane as shown above, most of it is made from phenol. 

Oxidation of organic compounds by dioxygen is a phenomenon of exceptional importance in nature, technology, and life. The liquid-phase oxidation of hydrocarbons forms the basis of several efficient technological synthetic processes such as the production of phenol via cumene oxidation, cyclohexanone from cyclohexane, styrene oxide from ethylbenzene, etc. The intensive development of oxidative petrochemical processes was observed in 1950-1970. Free radicals participate in the oxidation of organic compounds. Oxidation occurs very often as a chain reaction. Hydroperoxides are formed as intermediates and accelerate oxidation. The chemistry of the liquid-phase oxidation of organic compounds is closely interwoven with free radical chemistry, chemistry of peroxides, kinetics of chain reactions, and polymer chemistry. 

About Half the caprolactam is made from phenol. (The other half comes from cyclohexane.) Caprolactam is an intermediate step in making Nylon 6. 

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... 

Adipic acid historically has been manufactured predominantly from cyclohexane and, to a lesser extent, phenol. During the 1970s and 1980s, however, much research has been directed to alternative feedstocks, especially butadiene and cyclohexene, as dictated by shifts in hydrocarbon markets. All current industrial processes use nitric acid in the final oxidation stage. Growing concern with air quality may exert further pressure for alternative routes as manufacturers seek to avoid NO, abatement costs, a necessary part of processes dial use nitric acid. 

Carboxonium-carbenium dications have also been proposed in the reactions of aryl ethers, phenols, and naphthols, with superacids. When 2-naphthol is reacted with an excess of AICI3 (3 equivalents) and cyclohexane, the product of ionic hydrogenation is observed in 59% yield (eq 15).24 This conversion is thought to occur by double protonation of the 2-naphthol ring to give the dication 48, which is capable of abstracting hydride from cyclohexane. Similar intermediates are formed by the reactions of HF-SbFs with naphthyl ethers (eq 16).25... 

Liquid phase oxidation of hydrocarbons by molecular oxygen forms the basis for a wide variety of petrochemical processes,3 "16 including the manufacture of phenol and acetone from cumene, adipic acid from cyclohexane, terephthalic acid from p-xylene, acetaldehyde and vinyl acetate from ethylene, propylene oxide from propylene, and many others. The majority of these processes employ catalysis by transition metal complexes to attain maximum selectivity and efficiency. 

Caprolactam. Essentially all caprolactam is used in the manufacture of nylon 6 fibers. In 1998, global demand reached nearly 7.3 billion lb with 1.7 billion lb used in North America. This is a fast-growing nylon with applications in carpets, textiles, and tires. Caprolactam can be produced from cyclohexane, phenol, and toluene via cyclohexanone. It is then reacted with hydroxylamine to give an oxime. The oxime undergoes an acid-catalyzed rearrangement to give caprolactam. 

Zeolites have been used as (acid) catalysts in hydration/dehydration reactions. A pertinent example is the Asahi process for the hydration of cyclohexene to cyclo-hexanol over a high silica (Si/Al>20), H-ZSM-5 type catalyst [57]. This process has been operated successfully on a 60000 tpa scale since 1990, although many problems still remain [57] mainly due to catalyst deactivation. The hydration of cyclohexanene is a key step in an alternative route to cyclohexanone (and phenol) from benzene (see Fig. 2.19). The conventional route involves hydrogenation to cyclohexane followed by autoxidation to a mixture of cyclohexanol and... 

Molecular oxygen can also oxidize a variety of organic compounds, including hydrocarbons, aldehydes, amines, ethers and ketones. These autooxidation reactions can be used to make a variety of small molecules and a number of industrial processes rely on the controlled oxidation of organics using molecular oxygen (often with a metal catalyst). Examples include the formation of phenol and acetone from cumene (isopropylbenzene) and cyclohexanone from cyclohexane. Phenol is a popular starting material for a number... 

HoUow-fiber SLMs have been used in the removal of phenol from aqueous matrices. Kujawski et al. [142, 143] studied polypropylene membranes impregnated with methyl-terbutyl ether, cumene, and/or a mixture of hydrocarbons. With Cyanex 923 (a mixture of trialkylphosphine oxides), the recoveries of phenol reached of 98% into the stripping phase from the 0.2 mol.dm solution of caustic soda [144, 145]. Carriers for phenol removal from wastewaters have included hnear monoalkyl cyclohexane [146], N,N-di(l-methyl heptyl) acetamide [147], dibenzo-18-crown-6 [148], dodecane [149], trioctylamine [150], and N-octanoylpyr-rolidine [151]. Many diluents and carriers are of synthetic origin, and so their application carries with issues of flammabUity, volatility, toxicity, and potential detrimental effects to the environment and the health of the human population [152]. 

The catalytic properties of the supported samples were tested in oxidation of cyclohexane and benzene with a mixture of O2/H2 gases at a temperature of 20-40°C. Cyclohexanol and cyclohexanone were obtained from cyclohexane and phenol with admixtures of cyclohexanol and hydroquinone (no more than 2% mol. of each) was obtained from benzene. 

Adipic acid (dj5 = 1.360(2), mp = 135°C) is manufactured industrially from cyclohexane for about 95 per cent of total production, or from phenoL... 

Processes for producing caprolactam from phenol and cyclohexane... 

Reduction of enones and bicyclic phenols. French chemists have reported transfer of hydrogen from cyclohexane to enones and phenols in this super acid. The products are the more stable isomers. This method has obvious advantages over Li-NHa for reduction of bicyclic phenols. 

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