Benzene production from cyclohexane over

The catalytic performances obtained during transalkylation of toluene and 1,2,4-trimethylbenzene at 50 50 wt/wt composition over a single catalyst Pt/Z12 and a dualbed catalyst Pt/Z 121 HB are shown in Table 1. As expected, the presence of Pt tends to catalyze hydrogenation of coke precursors and aromatic species to yield undesirable naphthenes (N6 and N7) side products, such as cyclohexane (CH), methylcyclopentane (MCP), methylcyclohexane (MCH), and dimethylcyclopentane (DMCP), which deteriorates the benzene product purity. The product purity of benzene separated in typical benzene distillation towers, commonly termed as simulated benzene purity , can be estimated from the compositions of reactor effluent, such that [3] ... 

Alkanes appear to react with platinum(IV) in an identical manner to benzene (34, 84) chloromethane and chloroethane can be detected as the reaction products from methane and ethane, respectively. When propane, butane, or hexane is the reactant, the terminal chloro isomers predominate over the internal isomers. This was interpreted to mean that primary C—H bonds are the most reactive (34), but a more detailed study has shown that this conclusion does not necessarily follow from the experimental results (84). When cyclohexane is the reactant, dehydrogenation (or chlorination and then dehydrohalogenation) occurs to give benzene as one of the reaction products (29, 34, 84). 

The fluorination of cyclohexane probably takes place via an initial conversion into benzene, brought about by the fluorinating agent, as under certain conditions (CeF4 at 300 C, a temperature at which benzene does not fluorinate over this reagent) benzene can be isolated as the near-sole product.42 If cyclohexane is first converted into benzene, then all fluorinations of saturated compounds might also proceed via an initial desaturation step this point is touched on several times throughout Section 25.1. The products are much the same as those obtained from benzene (Section 25.1.1.2.). 

To 21.6 kg (17.8 I) of 98% formic acid was added 1.14 kg (7.5 mols) of D-(-)-mandelic acid and the reaction mixture was heated for 4 hours at 70°C with stirring. The excess formic acid was evaporated off in vacuo and the residual syrup was dissolved in 6 I of benzene. The solution was washed twice with 6 I portions of water and was dried over magnesium sulfate. The drying agent was filtered and washed with 1.5 I of benzene, the washes being added to the filtrate. The dried filtrate was evaporated in vacuo to obtain the D-(-)-mandelic acid formate ether as a syrup. The product can be crystallized from cyclohexane to yield material melting at about 55°C to 58°C. 

The oil that separates is extracted with ether, the extract dried over anhydrous sodium sulfate and then evaporated at reduced pressure. The residue is dissolved in boiling benzene (75 ml) treated with decolorizing charcoal, filtered, treated with boiling cyclohexane (275 milliliters) and cooled to give 22.3 grams of 2,3-dichloro-4-butyrylphenoxyacetic acid. After several recrystallizations from a mixture of benzene and cyclohexane, then from methyl-cyclohexane, next from a mixture of acetic acid and water, and finally from methylcyclo-hexane, the product melts at 110° to 111°C (corr). 

B. 2,2-(Trimethylenedithio)cyclohexanone. A solution of 3.02 g. (0.02 mole) of freshly distilled 1-pyrrolidinocyclohexene, 8.32 g. (0.02 mole) of trimethylene dithiotosylate4 (Note 2), and 5 ml. of triethylamine (Note 3) in 40 ml. of anhydrous acetonitrile (Note 4), is refluxed for 12 hours in a 100-ml., round-bottom flask under a nitrogen atmosphere. The solvent is removed under reduced pressure on a rotary evaporator, and the residue is treated with 100 ml. of aqueous 0.1 N hydrochloric acid for 30 minutes at 50° (Note 5). The mixture is cooled to ambient temperature and extracted with three 50-ml. portions of ether. The combined ether extracts are washed with aqueous 10% potassium bicarbonate solution (Note 6) until the aqueous layer remains basic to litmus, and then with saturated sodium chloride solution. The ethereal solution is dried over anhydrous sodium sulfate, filtered, and concentrated on a rotary evaporator. The resulting oily residue is diluted with 1 ml. of benzene and then with 3 ml. of cyclohexane. The solution is poured into a chromatographic column (13 x 2.5 cm.), prepared with 50 g. of alumina (Note 7) and a 3 1 mixture of cyclohexane and benzene. With this solvent system, the desired product moves with the solvent front, and the first 250 ml. of eluent contains 95% of the total product. Elution with a further 175 ml. of solvent removes the remainder. The combined fractions are evaporated, and the pale yellow, oily residue crystallizes readily on standing. Recrystallization of this material from pentane gives 1.82 g. of white crystalline 2,2-(trimethylenedithio)cyclo-hexanone, m.p. 52-55° (45% yield) (Note 8). 

If various feeds give the same TPR spectrum for their end product, a common rate determining step can be assumed. This was the situation when TPR spectra of benzene formed over Pt-AljOj from adsorbed n-hexane, 1-hexene, and 1,5-hexadiene were studied. This re-confirms the hexane-hexene-hexadiene stepwise mechanism since cyclohexane, cyclohexene, and cyclohexadiene gave another type of TPR spectrum (62b). 

In a more recent study of the dehydrogenation of cyclohexane to benzene over a chromium oxide catalyst at 450°C., Balandin and coworkers (Dl) concluded that benzene was formed by two routes. One of these, the so-called consecutive route, involves cyclohexene as a gas phase intermediate, while the other proceeds by a direct route in which intermediate products are not formed in the gas phase. It was concluded that the latter route played a larger role in the reaction than did the former. These conclusions were derived from experiments on mixtures of cyclohexane and Cl4-labeled cyclohexene, which made it possible to evaluate the individual rates Wi, BY, Wt, and Wz in the reaction scheme... 

Cyano-10-(3-methanesulfonyloxypropyl)phenthiazine and 4-hydroxypiperidine in toluene were heated under reflux with stirring. The reaction mixture was allowed to cool and water was added. The resulting toluene solution layer was decanted and washed twice with water. The toluene solution was then stirred with 5% hydrochloric acid. The hydrochloride of the desired phenthiazine base precipitated in gummy condition in the aqueous layer. This was decanted and treated with sodium hydroxide (density 1.33). It was then extracted three times with ethyl acetate. The extracts were dried over sodium sulfate, filtered and concentrated in vacuum. A resinous product was obtained. This product was dissolved in a mixture of benzene and cyclohexane and chromatographed on a column containing alumina. The chromatographed product was eluted successively with mixtures of benzene and cyclohexane and then with benzene and finally with a mixture of benzene and ethyl acetate. The eluates were evaporated to yield a crude product. This product was recrystallised from aqueous ethanol (40% water) and yielded 2-cyano-10-[3-(4-hydroxy-l-piperidyl)propyl]phenthiazine as white crystals. 

VOCs are the most well-known air contaminants released by chemical, petrochemical, and other industries. Benzene, toluene, xylenes, hexane, cyclohexane, thiophene, diethylamine, acetone, and acetaldehyde are examples of VOCs [77,78], Possibly, presently the most relevant technology for VOC control is adsorption on activated carbon [135-145], It is a recognized technology, largely applied in industrial processes for the elimination and recovery of hydrocarbon vapors from gaseous streams [77,136], Additionally, it offers several benefits over the others, that is, the opportunity of pure product retrieval for reuse, high removal efficiency at low inlet concentrations, and low fuel/ energy costs [135],... 

Hydrogenation of benzene over acidic catalysts or in the presence of acid results in the formation of the products resulting from alkylation by the intermediate cyclohexene such as cyclohexylbenzene, together with cyclohexane, as shown in Scheme 11.1. Slaugh and Leonard obtained cyclohexylbenzene in high selectivity in the hy-... 

Our final example of a complex column is an azeotropic system in which we add a light entrainer to facilitate the separation of two components. The classical example of this type of system is the use of benzene or cyclohexane to break the ethanol-water azeotrope. As shown in Fig. 6.26, the vapor from the top of the column is condensed and fed into a decanter in which the two liquid phases separate. The aqueous phase is removed as product. The organic phase (the light entrainer) is refluxed back to the column. Some of the organic may also be added to the feed stream to alter the composition profiles in the column (if more entrainer is needed lower in the column). Note that the organic level in the decanter is not controlled. A small stream of fresh entrainer ivould be added to make up for any losses of entrainer over a long period... 

Another approach to achieve higher conversions is to start from cyclohexene, which is much more reactive than cyclohexane towards autoxidation [6], and can be prepared by hydrogenation of benzene over a ruthenium catalyst [7]. The higher reactivity of cyclohexene also allows for lower reaction temperatures thus further limiting overoxidation. The 2-cyclohexen-l-one product formed by decomposition of cyclohexenyl hydroperoxide can subsequently be hydrogenated to cyclohexanone. The net reaction stoichiometry is the same as the current process. We now report our results on the use of CrAPO-5, CrS-1 and other transition-metal substituted molecular sieves for the decomposition of cyclohexenyl hydroperoxide. 

The conversion of cyclohexanes to aromatics is a classical dehydrogenation reaction which will readily take place on many transition metals and metal oxides. On chromia-alumina Herington and Eideal (S) have demonstrated the occurrence of cyclo-olefin intermediate products. Weisz and Swegler 25) have demonstrated the effect on benzene yield of allowing early diffusional escape of cyclo-olefin from the porous catalyst particle. Prater et al. 26) have developed evidence that cyclohexene occurs as a quasi-intermediate in aromatization catalysis over platinum catalyst also, although at a smaller concentration, because of a larger ratio of effective rate constants fe/Zci in the scheme... 

Sulfonation by Means of Fuming Sulfuric Acid. (Demonstration) Use n-hexane, cyclohexane and benzene. Place 0.5 ml of each hydrocarbon in separate marked test tubes. Add about 1 ml of fuming sulfuric acid (20-25 per cent SO3), and shake cautiously from time to time over a period of 15 minutes. Add the contents of each tube very slowly and carefully to a 150 ml beaker containing 25-30 ml of water. When all the acid mixture has been added stir the contents of the beaker, and then note whether a layer of hydrocarbon separates on the top of the diluted acid. If the hydrocarbon is completely sulfonated, the product is soluble. Record your data. 

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