Oxidative dehydrogenation cyclohexane

Minachev et al. (41, 42) have recently examined alkali metal ion forms of various zeolites (A, X, Y, L, chabazite, erionite, and mordenite) for cyclohexane oxidative dehydrogenation. Not surprisingly these alkali metal ion forms are considerably less active than those containing transition metal ions (reaction temperatures of approximately 300° and 450°C, respectively). Further, cyclohexene rather than benzene is the predominant product (selectivity to cyclohexane 67-84%), particularly with small-pore zeolites. In fact, NaA was the most active zeolite tested (42), which strongly suggests that the reaction is simply occurring on the outer surface of the zeolite crystallites. 

Aldehydes and ketones, which are produced by different methods and starting materials, are important carbonyl compounds that are widely used as such and for further processing [1], For example, cyclohexanone can be prepared upon cyclohexane oxidation, dehydrogenation of cyclohexanol at high temperature, or via catalytic oxidation of cyclohexanol under milder conditions. Acetophenone can be produced by the Hock process or be obtained via ethylbenzene oxidation with dioxygen, whereas benzaldehyde is produced industrially by toluene oxidation or by hydrolysis of benzal chloride in the presence of different acids and/or metal salts (i.e., tin(II), tin(IV), iron, or zinc chlorides) [1],... 

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... 

Selective transformations Selective styrene ring opening [103] One-pot domino process for regioselective synthesis of a-carbonyl furans [104] Tandem process for synthesis of quinoxalines [105] Atmospheric oxidation of toluene [106] Cyclohexane oxidation [107] Synthesis of imines from alcohols [108] Synthesis of 2-aminodiphenylamine [109] 9H-Fluorene oxidation [110] Dehydrogenation of ethane in the presence of C02 [111] Decomposition of methane [112] Carbon monoxide oxidation [113]... 

There are fewer studies of oxidative dehydrogenation of butane, and even fewer for cyclohexane than ethane or propane. The performance of the better catalysts in these two reactions are summarized in Table VII and Fig. 5. Because of the larger number of secondary carbon atoms in these molecules, they are more reactive with gaseous oxygen than the smaller alkanes. In ex-... 

Fig. 5. Selectivity for oxidative dehydrogenation of cyclohexane and butane. Data taken from Table 7.

Minachev et al. [76] studied oxidative dehydrogenation of cyclohexane on zeolite cationic forms at 300-475 °C, the main reaction product of which is cyclohexene. Cyclohexadiene and C02 are also formed, and at long-term contacts benzene is detected. Cyclohexene yield and selectivity of the reaction depend on zeolite structure and composition, reaction temperature and oxygen cyclohexane ratio in the reaction mixture. Among alkaline cationic forms of zeolite, the highest cyclohexene yield (21%) is observed for NaA zeolite (66% selectivity). 

The oxidative dehydrogenation of cyclohexane to benzene has been studied more extensively. Transition metal ion-exchanged forms of zeolite Y have been shown (34-39) to be particularly active catalysts for this reaction. Although the platinum metal ions exhibit the highest activity, CuY was found to be the most selective for benzene formation (38, 39). 

These results first appear to be unusual but can be explained as follows. As the heat transfer coefficient decreases, it becomes more difficult for heat to transfer from the permeate side (where oxidation of hydrogen takes place) to the feed side (where cyclohexane is dehydrogenated). The resulting excess heat goes to increasing the temperature of the permeate side which makes the oxidation reaction faster. This, in turn, leads to higher temperatures on both the feed and permeate sides. Therefore, at a given... 

The controlled oxidation of alkanes into alcohols also attracts attention from an industrial point of view. Copper-based catalysts containing Tp ligands have been employed as catalysts for this reaction that led to a very interesting as well as unprecedented transformation with copper. Thus, when cyclohexane was reacted with in the presence of these catalysts, cyclohexane was partially converted into cyclohexanol and cyclohexanone, as expected. However, a certain amount of cyclohexane underwent dehydrogenation affording cyclohexene, in the first example of a copper-mediated alkane dehydrogenation process. Part of the cyclohexene was epoxidized in the reaction... 

This system possesses sites able to perform the oxidative dehydrogenation of paraffins. This is demonstrated by the formation of benzene with high specificity from cyclohexane, as well as by the formation of olefins and diolefins from n-paraffins, of aromatic compounds... 

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. 

By far the largest outlet for benzene (approx. 60%) is styrene (phenyl-ethene), produced by the reaction of benzene with ethylene a variety of liquid and gas phase processes, with mineral or Lewis acid catalysts, are used. The ethylbenzene is then dehydrogenated to styrene at 600-650°C over iron or other metal oxide catalysts in over 90% selectivity. Co-production with propylene oxide (section 12.8.2) also requires ethylbenzene, but a route involving the cyclodimerization of 1,3-butadiene to 4-vinyl-(ethenyl-) cyclohexene, for (oxidative) dehydrogenation to styrene, is being developed by both DSM (in Holland) and Dow. 60-70% of all styrene is used for homopolymers, the remainder for co-polymer resins. Other major uses of benzene are cumene (20%, see phenol), cyclohexane (13%) and nitrobenzene (5%). Major outlets for toluene (over 2 5 Mt per annum) are for solvent use and conversion to dinitrotoluene. 

The phenol process based on the oxidation of cyclohexane has been operated for a short time by Monsanto in Australia and is of less importance. In this process, a mixture of cyclohexanone and cyclohexanol is dehydrogenated to phenol at 400 °C, using platinum/activated carbon or nickel/cobalt catalysts. The degree of conversion can reach 90 5%. The crude phenol is refined by distillation. A particular disadvantage of this process lies in the difficulty in refining the crude oxidation mixture from cyclohexane oxidation. 

The best olefin yields were observed over Pt-coated monoliths. In the case of ethane/02 mixtures, selectivities to ethylene up to 65% at 70% ethane conversion and complete O2 conversion were reported." The oxidative dehydrogenation of propane and -butane produced total olefin select vies of about 60% (mixtures of ethylene and propylene) with high paraffin conversions." " Mixtures of ethylene, propylene and 1-butene were observed by the partial oxidation of -pentane and n-hexane ethylene, cyclohexene, butadiene and propylene were the most abundant products of the partial oxidation of cyclohexane." ... 

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