Cyclohexanone mixtures

Hydrocarbon Oxidation. The oxidation of hydrocarbons (qv) and hydrocarbon derivatives can be significantly altered by boron compounds. Several large-scale commercial processes, such as the oxidation of cyclohexane to a cyclohexanol—cyclohexanone mixture in nylon manufacture, are based on boron compounds (see Cylcohexanoland cyclohexanone Eibers, polyamide). A number of patents have been issued on the use of borate esters and boroxines in hydrocarbon oxidation reactions, but commercial processes apparently use boric acid as the preferred boron source. The Hterature in this field has been covered through 1967 (47). Since that time the Hterature consists of foreign patents, but no significant appHcations have been reported for borate esters. 

The transformation of a cyclopentanol/cyclohexanone mixture allows us to estimate simultaneously the acidity and the basicity of catalysts. Two reactions take place the hydrogen transfer (HT) on basic sites and the alcohol dehydration (DEH) on acid sites. This reaction was carried out at two temperatures over four aluminas. Theta alumina seems to be the most basic of the aluminas tested. Correlation between model reaction and IR study were also discussed. 

Figure 1. Reaction scheme of cyclopentanol-cyclohexanone mixture transformation.

The transformation of cyclopentanol-cyclohexanone mixture was carried out in a fixed-bed reactor at 200°C and 250°C under atmospheric pressure and in the presence of nitrogen (nitrogen/reactant molar ratio = 4). The reactant was an equimolar mixture of cyclopentanol and cyclohexanone. The reaction products were analyzed on line by GC (VARIAN 3400 chromatograph, equipped with a SGE CIDEX B 25 m x 0.22 mm column and a flame ionization detector). The deactivation profile was obtained by analyzing reaction effluent for various times-on-stream (TOS). 

The transformation of cyclopentanol-cyclohexanone mixture was carried out on aluminas, and compared with a basic (MgO) and acidic (HMOR zeolite, Si/Al = 80) catalysts. Figure 2 shows the activities, expressed as mmol.h 1.m 2, for the two reactions, for the different catalysts. 

Figure 2. Transformation of cyclopentanol-cyclohexanone mixture at 250°C. Initial activity in mmol.h. m 2. (a) basic character and (b) acid character.

The transformation of cyclopentanol/cyclohexanone mixture was also carried out at 200°C. The strength of the acid and basic sites was estimated from the activation energy (Ea) for the both reaction (Table 1). 

Alumina is an amphoteric catalyst, which can difficult to characterize via chemical and physic methods. The transformation of cyclopentanol/cyclohexanone mixture allows us to estimate at the same time the acid-base properties of aluminas. From this transformation, it was shown that aluminas can be classified into two families only basic aluminas, such as theta, which were more basic than MgO, and acido-basic aluminas, eta, gamma and delta, which possess an acidic character less pronounced than dealuminated HMOR zeolite... 

Nitric acid is used for nitrating numerous other compounds to produce nitrates. Nitric acid is used to produce adipic acid (C6H4O10), which is used in the production of nylon (see Nylon). In this process, cyclohexane is oxidized to a cyclohexanol-cyclohexanone mixture. Cyclohexanol and cyclohexanone are then oxidized with nitric acid to adipic acid. 

Homolytic liquid-phase processes are generally well suited to the synthesis of carboxylic acids, viz. acetic, benzoic or terephthalic acids which are resistant to further oxidation. These processes operate at high temperature (150-250°C) and generally use soluble cobalt or manganese salts as the main catalyst components. High conversions and selectivities are usually obtained with methyl-substituted aromatic hydrocarbons such as toluene and xylenes.95,96 The cobalt-catalyzed oxidation of cyclohexane by air to a cyclohexanol-cyclohexanone mixture is a very important industrial process since these products are intermediates in the manufacture of adipic acid (for nylon 6,6) and caprolactam (nylon 6). However, the conversion is limited to ca. 10% in order to prevent consecutive oxidations, with roughly 70% selectivity.97... 

Adipic acid is a most important petrochemical product which is mostly used for the synthesis of nylon 6.6 from its condensation with hexamethylenediamine. Cyclohexane is transformed to adipic acid in two steps (a) oxidation of cyclohexane to a cyclohexanol-cyclohexanone mixture (ol-one) via the formation of cyclohexyl hydroperoxide followed by (b) oxidation of the ol-one mixture to adipic acid by nitric acid (equation 239). 

Adipic acid (melting point 152.1°C, density 1.344) is manufactured predominantly by the oxidation of cyclohexane followed by oxidation of the cyclohexanol/cyclohexanone mixture with nitric acid (Figs. 1 and 2) ... 

There is no need to separate the cyclohexanol/cyclohexanone mixture into its individual components oxidation of the mixture is carried out directly. 

In the second step of the process, the cyclohexanol/cyclohexanone mixture is further oxidized to adipic acid by nitric acid at 75-80°C and 1-4 bar. 

When the imine has more than one site capable of undergoing fluorination (e.g., imines of cyclopentanone or cyclohexanone), mixtures of fluorinated products arc obtained. 

On completion, water is added to the mixture after which it is fractionated. Cyclohexane (b.p. 81°C) containing some benzene is collected from the top of the column, and after hydrogenation of the benzene, is recycled. The cyclo-hexanol-cyclohexanone mixture consists of approximately equal volumes of cyclohexanol (b.p. 161°C), cyclohexanone (b.p. 156°C), plus a mixture of several esters and ethers. It is collected from the bottom with 80+% yields on cyclohexane. An alternative route to cyclohexanol used by some plants is to catalytically hydrogenate phenol. 

The cyclohexanol-cyclohexanone mixture isolated from air oxidation, without separation, is oxidized with 5 volumes of 50% nitric acid plus catalyst at 50-90°C, and pressures only slightly above ambient for 10-30 min, depending on the temperature used (Eq. 19.58). 

The third method to stain the PMMA is to add the fluorescent dye after particle synthesis. This is achieved by finding a solvent that will dissolve the dye and also be taken up by the particles. Thus, an acetone/cyclohexanone mixture can be used to deliver rhodamine perchlorate dye to preformed PMMA spheres [13]. Tire advantage of this method is that once a suitable delivery system is found, many possible dyes, and even multiple dyes, may be added to tire spheres. The disadvantage is that the solvent mixture may attack the spheres, swell them or alter their physical properties. 

Historically, several processes have been developed to an industrial scale to produce phenol, including (i) sulfonation of benzene and alkali fusion of the benzene sulfonate (ii) chlorination of benzene and hydrolysis of chlorobenzene (iii) the cumene process (Section 13.2) (iv) toluene oxidation to benzoic add and subsequent oxidative decarboxylation of the latter to phenol and (v) dehydrogenation of cyclohexanol-cyclohexanone mixtures. Today, however, only the cumene process and the toluene oxidation are still run on an industrial scale, all the other processes having been given up due to economic reasons or environmental problems. 

Despite its brilliant results, it seems unlikely that the Solutia process can become a major source of phenol. Nitrous oxide availability is quite limited and its production on-purpose (by the conventional ammonium nitrate decomposition, which enables nitrous oxide of high purity to be produced for medical anesthetic applications, or even by selective oxidation of ammonia) would result too expensive. Therefore, the only reasonable scenario to exploit the Solutia process is its implementation close to adipic acid plants, where nitrous oxide is co-produced by the nitric oxidation of cyclohexanol-cyclohexanone mixtures and where it could be used to produce phenol instead of being disposed of However, the stoichiometry of the process is such that a relatively small phenol plant would require a world-scale adipic acid plant for its nitrous oxide supply. In fact, a pilot plant has been operated using this technology, but its commercialization has been postponed. 

Scheme 3. Reaction of the cyclopentanol/cyclohexanone mixture at 350°C over various metal oxide catalysts, from reference 15.

Oxidation of cyclohexane with hydrogen peroxide and a SiWio[Fe(H20)]20386 catalyst at 83°C for 96 h gave a 55 45 cyclohexanol/cyclohexanone mixture in 66% conversion with 95% utilization of hydrogen peroxide.301 If the time can be reduced and cheap hydrogen peroxide is available, this could replace the current relatively inefficient air oxidation of cyclohexane in the production of nylon. 

These processes involve two stages. Cyclohexane is first oxidized to a cydohexanol/ cyclohexanone mixture (see Section 9.1.6.1 and Section 121.22X which is then dehydrogenated (Fig. 121IX This Ol/One mixture is first fractionated in a series of three distillation columns operating under vacuum, of which the first two (20 trays each) separate the... 

Figure 3.1 ranslonnaiion ol ihc cvclopentuno) cyclohexanone mixture as suggested by Berkam et al [222]. 

Methyl ethyl ketone Acetyl ketone Cyclohexanone Mixtures... 

Nitric Acid Oxidation of a Cyclohexanol/Cyclohexanone Mixture to Produce Adipic Acid... 

Adipic acid (AA) is produced almost exclusively by nitric acid oxidation of a cyclohexanol/cyclohexanone mixture in the presence of copper and vanadium catalysts in a homogeneous phase with the reaction mixture. 

The high demand for nylon has stimulated the development of several ingenious cheap syntheses of the monomeric precursors. Thus, hexanedioic (adipic) acid is currently produced from benzene by three different multistep routes, all culminating in the last step in the salt-catalyzed oxidation of cyclohexanol (or cyclohexanol/cyclohexanone mixtures) with nitric acid. A green approach was disclosed in 2006 by chemists at Rhodia Chimie, France, in which air is used as the oxidizing agent instead of the toxic and corrosive (and more expensive) HNO3. 

Chromatogram of 2,4-dinitrophenyl-hydrazones of carbonyl compounds in 25% dimethylformamide/cyclohexane (1) formaldehyde, acetaldehyde, and acrolein, (2) formaldehyde, acetaldehyde, -butyraldehyde, and -valer-aldehyde, (3) -hexylaldehyde and w-dodecylaldehyde, (4) diacetyl (mono-hydrazone), cyclopentanone, cyclohexanone, mixture of methylcyclohe-xanones, (5) fural (trans-derivative), fural (cis-derivative), acetaldehyde, acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Spots near the start are due to 2,4- dinitrophenylhydrazine. 

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