Phenols by Fenton’s reagent

Kinetic Rate Constants of Chlorinated Phenols by Fenton s Reagent... 

The rate equation for dechlorination of chlorinated phenols by Fenton s reagent can be expressed as follows ... 

The MEO of BZ is much more complicated than the MEO of EG. One of the first intermediates formed during the oxidation of BZ by Ag(II) has been identified as phenol. References pertaining to this specific reaction have not been found. However, the conversion of BZ to phenol by Fenton s reagent, a mixture of hydrogen peroxide and ferric ions, is well known [32]. This synthesis is initiated by cathodic reduction of the ferric ion, Fe . 

The distributions of phenolic isomers in hydroxylations in the animal body arc often similar to those obtained by Fenton s reagent. For example, the hydroxylation of coumarin by the rabbit gives the six hydroxycoumarins in amounts decreasing in the order 3- >7->6- >8- >4- /—5-, whereas Fenton s reagent gives mainly the 3-, 5-, and 7-derivatives with traces of the 6- and 8-derivatives. It may, however, be misleading to draw conclusions about the nature of... 

The feasibility of benzenic ring amines, benzenic ring structures and aliphatic acids oxidation by means of Fenton chemistiy was tested in synthetic, acidic wastewaters by Fenton s reagent electrogenerated at a reticulated vitreous carbon cathode using the flow-cell. The organic molecules considered were phenol (Ph), cresol (Cr), aniline (An) hydroquinone (HQ), catechol (Cat), parabenzoquinone (pBQ) and oxalic acid (OxAc). Their initial... 

Tang, W.Z. and Huang, C.P., The effect of chlorine position of chlorinated phenols on their dechlorination kinetics by Fenton s reagent, Waste Manage., 15(8), 615-622, 1995. 

When benzene is oxidized by Fenton s reagent in the presence of air or oxygen, the only detectable organic product is phenol (that is, equation 76) whereas in the absence of air both phenol and diphenyl are produced (31). This oxygen effect may be due to the interaction of free phenyl radicals with oxygen, forming free radical peroxides, and ultimately phenol, in the presence of ferrous ion. The reaction between free radical and oxygen therefore appears to be faster than the dimerization of the free radical (31). 

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). 

Oxidation by H.O Phenol, anisole Pe(ll) (Fenton s reagent). Fe( II )-hydmquirionc Fei 11)-EDTA-ascorbic acid... 

My research on AOPs began over 12 years ago at the University of Delaware. When I worked on the degradation of phenols by a visible photon/ CdS system, I had to wake up at midnight in order to take samples from a photocatalytic reactor because the reaction half time in degrading 0.001-M phenol is about 1 day. After I found that Fenton s reagent was an extremely... 

For phenol hydroxylation it is shown that Fe2+ and Fe3+ ion activity increases in the presence of other ions, among which the highest activity is displayed by salts and complexes of the following metals Co, Mn, Mo, Cu, Fe, etc. In aqueous solution Fenton s reagent oxidizes substrates according to the radical mechanism in which reactions with 0H radicals play the central role. In aprotic solvents oxidation with Fenton s reagent suggests the participation of different intermediates—complexes with iron ions, Fe=0, for example. 

The reaction mechanism was first proposed by Haber and Weiss. The reactions involved in the oxidation of organics with Fenton s reagent can be quite complicated and will not be discussed here for example, the oxidation of phenol entails some 24 possible intermediate reactions ... 

Phenols — Phenol containing effluents can be efficiently destroyed by using Fenton s reagent (H202 with iron catalysis). This reagent produces the highly reactive OH radical. 

The most recent processes particularly for the industrial synthesis of catechol and hydroquinone are by the direct hydroxylation of phenol at SOX with 70% hydrogen peroxide solution in the presence of catalytic quantities of strong mineral acids, such as perchloric acid, with ferrous sulphate (Fenton s reagent) or cobaltous sulphate (ref.35). The organic products are solvent extracted and fractionated to separate the two products from the starting material. With a ferrous catalyst, resorcinol accompanies the two main products. 

For better understanding of the mechanisms of the electrochemical oxidation of phenol a comparative study was undertaken between electrochemical (with Pt and Sn02 anodes) and chemical oxidation of phenol with H2O2 in the presence of Fe+2 catalyst (Fenton s reagent) which is well known to occur by electrophilic attack of hydroxyl radicals on the organic compound (8). 

---