Oxidative hydrogenation 91 phenol

Titanium Silicates. A number of titanium siUcate minerals are known (160) examples are Hsted in Table 19. In most cases, it is convenient to classify these on the basis of the connectivity of the SiO building blocks, eg, isolated tetrahedra, chains, and rings, that are typical of siUcates in general. In some cases, the SiO units may be replaced, even if only to a limited extent by TiO. For example, up to 6% of the SiO in the garnet schorlomite can be replaced by TiO. In general, replacement of SiO by TiO bull ding blocks increases the refractive indices of these minerals. Ti has also replaced Si in the framework of various zeofltes. In addition, the catalytic activity of both titanium-substituted ZSM-5 (TS-1) and ZSM-11 (TS-2) has received attention (161), eg, the selective oxidation of phenol, with hydrogen peroxide, to hydroquinone and catechol over TS-1 has been operated at the 10,000 t/yr scale in Italy (162). 

New materials are also finding application in the area of catalysis reiated to the Chemicals industry. For example, microporous [10] materials which have titanium incorporated into the framework structure (e.g. so-calied TS-1) show selective oxidation behaviour with aqueous hydrogen peroxide as oxidizing agent (Figure 5). Two processes based on these new catalytic materials have now been developed and commercialized by ENl. These include the selective oxidation of phenol to catechol and hydroquinone and the ammoxidation of cyclohexanone to e-caproiactam. 

Zeolite based ceramics as catalysts for wet hydrogen peroxide catalytic oxidation of phenol and poly-phenols... 

Yube, K. and Furuta, M. and Mae, K. (2007). Selective oxidation of phenol with hydrogen peroxide using two types of catalytic microreactor, Catalysis Today, 125, 56-63. 

It is well known that U.S. space vehicles obtain their auxiliaiy power in space by the use of fuel cells (Chapter 13), electrochemical devices in which the spontaneous tendency of hydrogen to combine with oxygen drives the cell and produces electricity, with water as a by-product (pure enough to drink). It stands to reason then, that one might think of producing substances more economically valuable than water in this electrogenerative way. Such work is into its first decade and Fig. 7.190 shows an example benzene is oxidized to phenol with electricity as a by-product Clearly, the economics of such a process depend on the cost of the H2 and whether one can sell the electricity. This gives rise to a speculation. 

Benzoquinone [106-51-4], C6H402 (quinone) has been reported as a by-product of benzene oxidation at 410—430°C. Benzene can be oxidized to phenols with hydrogen peroxide and reducing agents such as Fe(II) and Ti(II). Frequendy ferrous sulfate and hydrogen peroxide are used (Fenton s reagent), but yields are generally low (12) and the procedure is of limited utility. Benzene has also been oxidized in the vapor phase to phenol in low yield at 450—800°C in air without a catalyst (13). 

Rivas, F., Kolaczkowski, S., Beltran, F., and McLurgh, D., Hydrogen peroxide promoted wet air oxidation of phenol influence of operating conditions and homogeneous metal catalysts, ]. Chem. Technol. Biotechnol., 74(5), 390-398, 1999. 

Oxidation of Phenolic Compound, 3 1 Hydrogen Peroxide Phenol Mole Ratio... 

Certain dinuclear iron complexes are found to be efficient catalysts for the oxidation of primary and secondary alcohols with hydrogen peroxide.214 Metalloporphyrins are used as peroxidase mimics in the oxidation of phenol with hydrogen peroxide. 

A final type of oxidation reaction associated with the loss of hydrogen atoms is seen in the oxidative dimerisation of phenols. In general, the oxidation of phenols, in either the presence or absence of metal ions, is not a clean process, and many products, derived from... 

Let us consider the reaction of benzene oxidation with hydrogen peroxide in the Fenton system as the classical situation [30], In the absence of iron ions benzene does not in practice interact with H202. The addition of bivalent iron salt to the system C6H6-H202-H20 induces benzene oxidation to phenol and diphenyl according to the following mechanism ... 

Irritant dermatitis does not involve an immune response and is typically caused by contact with corrosive substances that exhibit extremes of pH, oxidizing capability, dehydrating action, or tendency to dissolve skin lipids. In extreme cases of exposure, skin cells are destroyed and a permanent scar results. This condition is known as a chemical burn. Exposure to concentrated sulfuric acid, which exhibits extreme acidity, or to concentrated nitric acid, which denatures skin protein, can cause bad chemical bums. The strong oxidant action of 30% hydrogen peroxide likewise causes a chemical bum. Other chemicals causing chemical bums include ammonia, quicklime (CaO), chlorine, ethylene oxide, hydrogen halides, methyl bromide, nitrogen oxides, elemental white phosporous, phenol, alkali metal hydroxides (NaOH, KOH), and toluene diisocyanate. 

Baeyer-Villiger oxidation.1 Aromatic aldehydes can be converted to phenols in generally high yield by oxidation with hydrogen peroxide (30%) activated by an areneseleninic acid. Polymethoxyacetophenones are also oxidized to phenols, but in lower yields. 

Caprolactam is usually manufactured from cyclohexanone, made by the oxidation of cyclohexane or by the hydrogenation/oxidation of phenol (Fig. 1), although the manufacture can be an integrated process with several starting materials (Fig. 2). The cyclohexanol that is also produced with the cyclohexanone can be converted to cyclohexanone by a zinc oxide (ZnO) catalyst at 400°C. The cyclohexanone is converted into the oxime with hydroxylamine, which then undergoes rearrangement to give caprolactam. 

In 1983, Mimoun and co-workers reported that benzene can be oxidized to phenol stoichiometrically with hydrogen peroxide in 56% yield, using peroxo-vana-dium complex 1 (Eq. 2) [20]. Oxidation of toluene gave a mixture of ortho-, meta-and para-cresols with only traces of benzaldehyde. The catalytic version of the reaction was described by Shul pin[21] and Conte [22]. In both cases, conversion of benzene was low (0.3-2%) and catalyst turned over 200 and 25 times, respectively. The reaction is thought to proceed through a radical chain mechanism with an electrophilic oxygen-centered and vanadium-bound radical species [23]. 

How can we keep our health against these reactive oxygen radicals Fortunately, vitamin C (hydrophilic), vitamin E (hydrophobic), flavonoids, and other polyphenols can function as anti-oxidants. These anti-oxidants are phenol derivatives. Phenol is a good hydrogen donor to trap the radical species and inhibits radical chain reactions. The formed phenoxyl radical is actually stabilized by the resonance effect as shown in eq. 1.8. Thus, phenol and polyphenol derivatives are excellent hydrogen donors to inhibit the radical reactions and, therefore, they are called radical inhibitors. 

Fig- 6-1 Some examples of peroxidase-catalyzed oxidations of phenols and naphtols in (d), R1 represents a hydrogen or a bromine atom and R2 a hydrogen, methyl, or carboxymethyl groups... 

Danner DJ, Brignac PJ Jr, Arceneaux D et al (1973) The oxidation of phenol and its reaction product by horseradish peroxidase and hydrogen peroxide. Arch Biochem Biophys... 

Chung N, Aust SD (1995) Inactivation of lignin peroxidase by hydrogen peroxide during the oxidation of phenols. Arch Biochem Biophys 316 851-855... 

Pignatello, J.J. (1992) Dark and photoassisted iron (3+)-catalyzed degradation of chlorophenoxy herbicides by hydrogen peroxide. Environ. Sci. Technol. 26, 944-951 Polcaro, A.M., Mascia, M, Palmas, S. and Vacca, A. (2002) Electrochemical oxidation of phenolic and other organic compounds at boron doped diamond electrodes for wastewater treatment Effect of mass transfer. Ann. Chim. 93, 967-976... 

Q Predict the products of oxidation and reduction of the aromatic ring, including hydrogenation, chlorination, and Birch reduction. Predict the products of the oxidation of phenols. 

The detrimental effect could also be explained by the fact that hydrogen peroxide and hydroperoxides are produced by the oxidation of phenols, lignin and xylan. These peroxides easily decompose in the presence of metals like cobalt and iron, producing radicals like OH and H02 which are certainly very reactive (23). 

New synthetic processes for the preparation of established products were also industrially developed in Japan the manufacture of methyl methacrylate from C4 olefins, by Sumitomo and Nippon Shokubai in France, the simultaneous production of hydroquinone and pyro-catechin through hydrogen peroxide oxidation of phenol by Rhone-Poulenc in the United States the production of propylene oxide through direct oxidation of propylene operating jointly with styrene production, developed by Ralph Landau and used in the Oxirane subsidiary with Arco, which the latter fully took over in 1980 in Germany and Switzerland, the synthesis of vitamin A from terpenes, used by BASF and Hoffmann-La Roche. 

In plants, catalase appears to have two functions. First is the ability to dispose of the excess H202 produced in oxidative metabolism, and second is the ability to use H202 in the oxidation of phenols, alcohols, and other hydrogen donors. The difference in heat stability of catalase and peroxidase was demonstrated by Lopez et al. (1959). They found that blanching of southern peas for one minute in boiling water destroys 70 to 90 percent of the peroxidase activity and 80 to 100 percent of the catalase activity. 

Td configuration. The Sn-ZSM-12 catalyses the oxidation of phenol, m-cresol and xylene using aqueous hydrogen peroxide (Figure 4.8). 

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