Catalytic oxidation of phenols

Oxidation of hydroquinone and pyrocatechol in aqueous solution is accelerated by quinones [228,229], which seems to be due to the formation of semiquinone radicals and their fast reaction with oxygen. Duro-hydroquinone oxidation is autocatalytic [229], due to the accumulation of quinone and formation of semiquinone radicals [230—233], 

Complexes of transition metals accelerate the oxidation of phenols in polar solvents [234], Formation of phenoxy radicals was established by the ESR technique [235—241], Molecular products are produced as a result of the reactions of ArO. The initial steps suggested are 

Phenoxyl radicals are converted to quinones and products of phenol dimerization. Phenol oxidizes in water giving pyrocatechol and hydroquinone in the presence of metal ions [242], The best yields were obtained with Cu2+ and Fe3+ ions (100—150° C). 

Catalytic oxidation of phenols in non-aqueous solutions under the action of certain catalysts is accompanied, together with the formation of quinones and dimers, by oxidative polymerization [243,244], viz. 

Selective polymerization can be produced by proper choice of the solvent and catalyst. 

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

The catalytic oxidation of liquid hydrocarbons with air or oxygen. Since oxygen is not very soluble in the liquid, while the hydrocarbon could well be present in high concentration we could end up in extreme 1 (excess of B). The removal of dissolved organics from industrial waste water by catalytic oxidation as an alternative to biooxidation. Here oxygen is not very soluble in water, but the organic waste is also present in low concentration. It is therefore not clear in what regime the kinetics lie. The catalytic oxidation of phenol is an example of such an operation. 

For example, the most noteworthy disadvantage of catalytic wet oxidation is the severe catalyst deactivation (Larachi el al., 1999). Hamoudi el al. (1998, 1999) systematically studied the deactivation of Mn02/Ce02 catalyst during wet catalytic oxidation of phenol and the catalyst-surface modifications. It was observed that deactivation was induced mainly by the formation of carbonaceous deposits on the catalyst surface. Ohta et al. (1980) reported that the size of the catalyst particles affected the stabilization of catalytic activity. For granular particles of supported copper oxide, the catalytic activity was decreased after each inn, even after six successive experiments. In contrast, for larger particles the catalytic activity was stabilized after the first three runs. 

Sadana A, Katzer JR. Catalytic oxidation of phenol in aqueous solution over copper oxide. Ind Eng Chem Fundam 1974 13 127-134. 

Cheng J, Yu SM, Zuo P (2006) Horseradish peroxidase immobilized on aluminum-pillared interlayered clay for the catalytic oxidation of phenolic wastewater. Water Res 40 283-290... 

Feng, Y. J. and Li, X. Y. (2003) Electro-catalytic oxidation of phenol on several metal-oxide electrodes in aqueous solution. Water Res. 37, 2399-2407. 

This study focused on the deactivation of the Mn/Ce catalysts during reaction. The catalytic oxidation of phenol in aqueous solution to carbon dioxide, water and other side-products was selected as the test reaction. Catalysts were prepared from amorphous precursors using the citrate method and controlling the calcination temperature. Activity performance as a function of the time on stream was studied by simultaneously analyzing the conversion of phenol, the total organic carbon content of the catiyst, the cations eluted and the elemental composition of both cerium and manganese. Experimental conditions were widely varied. Fresh and used catalysts were also analyzed by BET surface area, X-Ray Diffraction and X-Ray Photoelectron Spectroscopy. 

In contrast to the catalytic oxidation of phenols, stoichiometric amounts of oxidants are generally used. Therefore, efficient recycle systems must be deviced. In this section, phenolic oxidations using organic reagents is mainly described. In addition, some well known oxidants such as NaI04, Fremy s salt and others are briefly described. 

In this chapter, reagents are classihed mainly into three categories (1) for catalytic oxidation of phenols, (2) for phenolic oxidation with nonmetallic compounds and (3) for phenohc oxidation with metallic compounds. In the 21st century, regardless of metallic or nonmetallic compounds, catalytic oxidation systems with high efficiency must be constructed. K stoichiometric amounts of reagents are employed, efficient oxidation-reduction systems should be invented. 

M.A.Walsh and J.R.Katzer, Catalytic Oxidation of Phenol in Dilute Concentration in Air , prepared for Office of Water Research and Technology and presented at 74th National Meeting, American Institute of Chemical Engineers, March 11-15,1973, New Orleans, LA. 

Table 7.10 The content of total iron (mg 1 ) in the solution after the catalytic oxidation of phenol in the presence of composite and metallic iron 35) = 100mg 1/5 1 = 10ml ...

The use of MPc complexes for the oxidation of phenols was explored by Zagal and coworkers by employing Ni as the central metal in the catalytic oxidation of phenols. Electro-oxidation of 2-chlorophenol occurred on polymerized NiTSPc . The use of CoPc monomer to modify GCE resulted in less fouling of the GCE and improved sensitivity . ... 

A survey of literature data shows that these similarities are most pronounced for the catalytic oxidation of phenols and naphthols with at least 1 alkyl substituent on the aromatic ring. In this chapter we will be concerned with that group of phenolic substrates. Treatment will be done according to catalyst types. 

CATALYTIC OXIDATION OF PHENOLS (b) Upon adding phenol 1... 

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