Hydrogenation, catalytic phenols

Allied-Signal Process. Cyclohexanone [108-94-1] is produced in 98% yield at 95% conversion by liquid-phase catal57tic hydrogenation of phenol. Hydroxylamine sulfate is produced in aqueous solution by the conventional Raschig process, wherein NO from the catalytic air oxidation of ammonia is absorbed in ammonium carbonate solution as ammonium nitrite (eq. 1). The latter is reduced with sulfur dioxide to hydroxylamine disulfonate (eq. 2), which is hydrolyzed to acidic hydroxylamine sulfate solution (eq. 3). 

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... 

Cyclohexanol [108-93-0] is a colorless, viscous liquid with a camphoraceous odor. It is used chiefly as a chemical iatermediate, a stabilizer, and a homogenizer for various soap detergent emulsions, and as a solvent for lacquers and varnishes. Cyclohexanol was first prepared by the treatment of 4-iodocyclohexanol with ziac dust ia glacial acetic acid, and later by the catalytic hydrogenation of phenol at elevated temperatures and pressures. 

Cyclohexanol. This alcohol is produced commercially by the catalytic air oxidation of cyclohexane or the catalytic hydrogenation of phenol. 

Dihydrothebainone-A-5 6-methyl enolate, CjaHjjOjN, m.p. 164-165-5°, [a] ° — 115-7° (EtOH). Cold N/HCl converts it into dihydrothebainone hydrochloride. The isomeric dihydrothebainone-J-6 7-methyl enolate is formed on catalytic hydrogenation of phenolic dihydrothebaine. It has m.p. 127-8°, [a] ° — 8° (EtOH) and yields dihydrothebainone on acid hydrolysis. ... 

From the results of this kinetic study and from the values of the adsorption coefficients listed in Table IX, it can be judged that both reactions of crotonaldehyde as well as the reaction of butyraldehyde proceed on identical sites of the catalytic surface. The hydrogenation of crotyl alcohol and its isomerization, which follow different kinetics, most likely proceed on other sites of the surface. From the form of the integral experimental dependences in Fig. 9 it may be assumed, for similar reasons as in the hy-drodemethylation of xylenes (p. 31) or in the hydrogenation of phenol, that the adsorption or desorption of the reaction components are most likely faster processes than surface reactions. 

Finally, Jessop and coworkers describe an organometalhc approach to prepare in situ rhodium nanoparticles [78]. The stabilizing agent is the surfactant tetrabutylammonium hydrogen sulfate. The hydrogenation of anisole, phenol, p-xylene and ethylbenzoate is performed under biphasic aqueous/supercritical ethane medium at 36 °C and 10 bar H2. The catalytic system is poorly characterized. The authors report the influence of the solubility of the substrates on the catalytic activity, p-xylene was selectively converted to czs-l,4-dimethylcyclohexane (53% versus 26% trans) and 100 TTO are obtained in 62 h for the complete hydrogenation of phenol, which is very soluble in water. 

Cinnamic acid may also be hydrogenated catalytically (p. 377). If the sodium amalgam method is chosen, the catalytic method should be practised with phenol. 

Acetophenone can be hydrogenated catalytically to 1-phenylethanol. It is obtained as a byproduct in the Hock phenol synthesis and is purified from the high-boiling residue by distillation. The quantitites obtained from this source satisfy the present demand. 

The reaction of hydrogen peroxide with copper(I) salts produces a Fenton-like hydroxylating system involving reactive hydroxyl radical intermediates (equation 265).486,491 Hydroxylation of benzene to phenol can be achieved by air in the presence of copper(I) salts in an acidic aqueous solution.592 593 This reaction is not catalytic (phenol yields are ca. 8% based on copper(I) salts) and stops when all copper(I) has been oxidized to copper(II). A catalytic transformation of benzene to phenol can occur when copper(II) is electrolytically reduced to copper(I) (equation 266).594,595... 

A manufacturing process that is specific for cyclohexylamines is the catalytic hydrogenation of anilines or phenols in the presence of ammonia. The catalytic hydrogenation of aniline is the classical method for the manufacture of cyclohexylamine. Hydrogenation of phenol in the presence of ammonia produces predominantly cyclohexyl or dicyclohexylamine depending upon catalysts, reaction conditions and reactant ratios116. 

About 90% of the caprolactam is produced by the conventional cyclohexanone process. Cyclohexanone is obtained by catalytic oxidation of cyclohexane with air, or by hydrogenation of phenol and dehydrogenation of the cyclohexanol byproduct. The conversion of cyclohexanone to cyclohexanone oxime followed by Beckmann rearrangement gives caprolactam. About 10% of caprolactam is produced by photonitrosation of cyclohexane or by nitrosation of cyclohexanecarboxylic acid in the presence of sulfuric acid264. 

Handl, V Beranek, L Kinetics of consecutive catalytic reactions hydrogenation of phenol on platinum catalyst, Chem. Eng. Sci., 25,1121-1126, 1970... 

Using peroxidases in the presence of hydrogen peroxide, phenolic substrates are converted catalytically to phenoxy radicals (Fig. 8.1). The phenoxy radicals produced in the enzymatic reaction step can then, in postenzymatic reactions, couple with each other or with other reactive substances present in the system [28-32]. Self-coupling of phenol molecules with each other dominates in systems that lack appropriate substrates to participate in cross-coupling reactions with phenol, leading to formation of precipitated polymeric products [9, 33] that can be readily removed from water. 

Allison et al. prepared the catalyst by decomposing nickel formate in a paraffin-paraffin oil mixture in a vacuum of a water-stream pump.45 The nickel catalyst thus prepared was not pyrophoric, not sensitive to air and chloride, and showed excellent catalytic properties in the hydrogenation of aqueous solutions of aromatic nitro compounds such as the sodium salts of m-nitrobenzenesulfonic acid, o-nitrobenzoic acid, and p-nitrophenol at pH 5-6. Sasa prepared an active nickel catalyst for the hydrogenation of phenol by decomposing nickel formate in boiling biphenyl [boiling point (bp) 252°C], diphenyl ether (bp 255°C), or a mixture of them (see eq. 11.12)42... 

Several processes are used for the industrial production of caprolactam. Generally cyclohexanone is the key intermediate and it is produced by catalytic hydrogenation of phenol (ex benzene or toluene) or the catalytic autoxidation of cyclohexane (from benzene hydrogenation) as shown in Fig. 2.27. 

Alternatively, pure cyclohexanone may be made by the catalytic hydrogenation of phenol in the presence of palladium on charcoal. 

The significance of the reaction of phenol with hydrogen has a number of important facets. First, the selective hydrogenation of phenol yields cyclohexanone, which is a key raw material in the production of both caprolactam for nylon 6 and adipic acid for nylon 6 . Second, due to the fact that phenol is an environmental toxin and phenolic waste has a variety of origins from industrial sources including oil refineries, petrochemical units, polymeric resin manufacturing and plastic units , catalytic hydrogenation of phenol is nowadays the best practicable environmental option . ... 

Wheland (64) describes 3-hydroxypyridine as a true phenol. Since phenols are the easiest of the substituted benzenes to hydrogenate catalytically (65), it should be of interest to examine some of the reductions of 3-hydroxypyridine for comparison. 

H, A. Smith University of Tennessee)-. Dr. Siegel (Lecture 4) suggests that his experiments indicate that a cyclohexene-type intermediate is formed in the catalytic hydrogenation of benzene. Further evidence for this is found in the hydrogenation of phenols, for when these are reduced under a variety of conditions and over a number of catalysts, cyclohexanone is formed as an intermediate and is readily isolated. The best explanation for this appears to be the addition of two moles of hydrogen per mole of phenol to form a cyclohexenol which isomerizes to cyclohexanone before further hydrogenation takes place. The cyclohexanone is desorbed from the catalyst, and may be subsequently reduced to cyclohexanol. 

The catalytic hydrogenation of thymol is of importance for the preparation of ( ) menthol (1J, out it may also be used as a model reaction for the reduction of substituted aromatics. The factors controlling the cis/trans ratios in the alcohols obtained on hydrogenating substimted phenols have been studied in detail in the case of cresols [2], but data are lacking for other alkylphenols. Thymol is reduced to the corresponding cyclohexanols (menthol, neomenthol, isomenthol and neoisomenthol), directly or via the cyclohexanones (menthone, isomenthone). Some hydrogenolysis (p-menthanes) may also occur. 

Catalytic hydrogenation of phenol and subsequent dehydrogenation of the resulting cyclohexanol... 

One-step catalytic hydrogenation of phenol using palladium on carbon catalyst... 

However, the production of caprolactam and adipic acid is predominantly based on cyclohexane (see Chapter 5.4). Cyclohexanol can be produced by catalytic hydrogenation of phenol. T e hydrogenation of phenol was first described by Paul Sabatier and Jean Baptiste Senderens in 1904. Figure 5.21 shows a flow diagram for the hydrogenation of phenol. 

Figure 5.22 shows the flow diagram for catalytic hydrogenation of phenol to cyclohexanone. 

Similarly, catalytic hydrogenation of phenol, produces cyclohexanol... 

Since the radicals RO and ROj, which are carriers of the kinetic oxidation chains, are formed in the catalytic decomposition of hydroperoxides, the appearance of phenoxyl radicals in such model systems of oxidation [14] gives evidence of stripping of the hydroxyl hydrogen of phenol by the active radicals, as the primary elementary event of inhibition, the reactivity of the OH-bond in the phenol being one of the most important characteristics of the effectiveness of the phenol as an inhibitor. 

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