Cyclohexanol, dehydrogenation

The activity observed with cyclohexanol-which is usually quite refractory to oxidation under mild conditions-is striking. In fact, high-loading copper catalysts are widely employed in cyclohexanol dehydrogenation [61], but working at high reaction temperatures under vapor-phase conditions. 

Table 5.9 Parameters in LHHW kinetic model for cyclohexanol dehydrogenation.

Frenkel M.L., Yursha I.A., Kabo G.Y., Thermodynamic parameters of cyclohexanol dehydrogenation, J. Appl. Chan. (Russia) 62(5), 1173,1989... 

The cyclohexanol dehydrogenation was carried out at a level of 30-40% conversion. Cyclohexanone, phenol and hydrocarbons like cyclohexane, cyclohexene and benzene were analyzed. The results summarized in Table 4 show that the selectivity changes from 30% to 91% by using AC and CF-s, respectively. 

A traditional catalyzed cyclohexane oxidation process consists of an oxidation and heat recovery section, a neutralization and decomposition section, a cyclohexane recovery section, a cyclohexanone separation and purification section, and finally a cyclohexanol dehydrogenation section. A simplified diagram of such a catalyzed cyclohexane oxidation process that is operated in a continuous mode is shown in the following ... 

DSM developed the noncatalyzed DSM Oxanone cyclohexane oxidation process in order to overcome the disadvantages of the traditional catalyzed cyclohexane oxidation process, namely, high cyclohexane and NaOH consumption figures and a large number of downtime hours. In addition, the DSM Oxanone process produces, after decomposition of CHHP, a KA oil with a KA ratio of more than 1.5 that requires a cyclohexanol dehydrogenation section with just a limited capacity. 

Fig. 17 Intrinsic and effective rate parameters for the catalytic cyclohexanol dehydrogenation...

Cesara DV, Perez CA, Salima VMM, Schmal M. Stability and selectivity of bimetallic Cu-Co/ Si02 catalysts for cyclohexanol dehydrogenation. Appl Catal A Gen. 1999 176 205-12. 

Reactions. The most important commercial reaction of cyclohexane is its oxidation (ia Hquid phase) with air ia the presence of soluble cobalt catalyst or boric acid to produce cyclohexanol and cyclohexanone (see Hydrocarbon oxidation Cyclohexanoland cyclohexanone). Cyclohexanol is dehydrogenated with 2iac or copper catalysts to cyclohexanone which is used to manufacture caprolactam (qv). 

The condensation of cyclohexanol or cyclohexene is generally carried out in the presence of phosphoric acid, pyrophosphoric acid, or HY 2eohtes the aromatization of intermediate cyclohexyUiydroquinone [4197-75-5] (19) is realized in the presence of a dehydrogenation catalyst. 

Phenol Vi Cyclohexene. In 1989 Mitsui Petrochemicals developed a process in which phenol was produced from cyclohexene. In this process, benzene is partially hydrogenated to cyclohexene in the presence of water and a mthenium-containing catalyst. The cyclohexene then reacts with water to form cyclohexanol or oxygen to form cyclohexanone. The cyclohexanol or cyclohexanone is then dehydrogenated to phenol. No phenol plants have been built employing this process. 

BASF. In the Badische process, cyclohexanone is produced by Hquid-phase catalytic air oxidation of cyclohexane to KA oil, which is a mixture of cyclohexanone and cyclohexanol, and is followed by vapor-phase catalytic dehydrogenation of the cyclohexanol in the mixture. Overall yields range from 75% at 10% cyclohexane conversion to 80% at 5% cyclohexane conversion. 

Dutch State Mines (Stamicarbon). Vapor-phase, catalytic hydrogenation of phenol to cyclohexanone over palladium on alumina, Hcensed by Stamicarbon, the engineering subsidiary of DSM, gives a 95% yield at high conversion plus an additional 3% by dehydrogenation of coproduct cyclohexanol over a copper catalyst. Cyclohexane oxidation, an alternative route to cyclohexanone, is used in the United States and in Asia by DSM. A cyclohexane vapor-cloud explosion occurred in 1975 at a co-owned DSM plant in Flixborough, UK (12) the plant was rebuilt but later closed. In addition to the conventional Raschig process for hydroxylamine, DSM has developed a hydroxylamine phosphate—oxime (HPO) process for cyclohexanone oxime no by-product ammonium sulfate is produced. Catalytic ammonia oxidation is followed by absorption of NO in a buffered aqueous phosphoric acid... 

Cyclohexanone [108-94-17 is a colorless, mobile Hquid with an odor suggestive of peppermint and acetone. Cyclohexanone is used chiefly as a chemical iatermediate and as a solvent for resias, lacquers, dyes, and iasecticides. Cyclohexanone was first prepared by the dry distillation of calcium pimelate [19455-79-9] OOC(CH2 )5COO Ca , and later by Bouveault by the catalytic dehydrogenation of cyclohexanol. 

This hypothesis would agree also with the results of the study of the influence of added substances on some other reactions (124). As an example, dehydration of cyclohexanol on alumina at 220°C is retarded by cyclohexanone, the dehydrogenation of cyclohexanol to cyclohexanone (the second reaction branch) not occurring with this catalyst at all. Hence, cyclohexanone is adsorbed on dehydration centers, on which the reaction which would lead to its formation does not take place at all. A similar result was obtained also for the second reaction branch, the dehydrogena-... 

Another recent patent (22) and related patent application (31) cover incorporation and use of many active metals into Si-TUD-1. Some active materials were incorporated simultaneously (e.g., NiW, NiMo, and Ga/Zn/Sn). The various catalysts have been used for many organic reactions [TUD-1 variants are shown in brackets] Alkylation of naphthalene with 1-hexadecene [Al-Si] Friedel-Crafts benzylation of benzene [Fe-Si, Ga-Si, Sn-Si and Ti-Si, see apphcation 2 above] oligomerization of 1-decene [Al-Si] selective oxidation of ethylbenzene to acetophenone [Cr-Si, Mo-Si] and selective oxidation of cyclohexanol to cyclohexanone [Mo-Si], A dehydrogenation process (32) has been described using an immobilized pincer catalyst on a TUD-1 substrate. Previously these catalysts were homogeneous, which often caused problems in separation and recycle. Several other reactions were described, including acylation, hydrogenation, and ammoxidation. 

Cu-Mg and Cu-Zn-Al catalysts are well known for the industrial dehydrogenation of cyclohexanol at 220-260°C (13), whereas Cu/Si02 catalysts are much less studied. 

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. 

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. 

Fig. 15.12 (a) Acid-base mechanism of alcohol dehydrogenation. Reprinted with permission from [70], Copyright (1993) Pergamon (Elsevier), (b) Redox mechanism of cyclohexanol ODH. Reprinted with permission from [74]. Copyright (1998) Elsevier. 

Two other, more recently popular routes are shown in Figure 7—6. In the first, benzene is hydrogenated to cyclohexane, followed by a partial oxidation to cyclohexanol. The cyclohexanol is then dehydrogenated to phenol. 

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