Hydrogen peroxide promoted wet air oxidation of phenol: influence of operating conditions and homogeneous metal catalysts
✍ Scribed by F Javier Rivas; Stan T Kolaczkowski; Fernando J Beltran; David B McLurgh
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1999
- Tongue
- English
- Weight
- 127 KB
- Volume
- 74
- Category
- Article
- ISSN
- 0268-2575
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✦ Synopsis
The promoted wet air oxidation of phenol has been investigated through the addition of hydrogen peroxide as a source of free radicals. The reaction has been shown to proceed in two stages, an initial fast reaction associated with hydrogen peroxide consumption and a second slower step that occurs at a rate comparable with conventional wet air oxidation. An increase in temperature has a positive effect on both stages, while oxygen partial pressure only in¯uences the second slower stage. The in¯uence of pH on phenol oxidation is shown to be signi®cant with the highest ef®ciency achieved at very alkaline conditions when phenol is completely dissociated. The catalytic activity of homogeneous metal salts was investigated in both the presence and absence of hydrogen peroxide. The combined addition of hydrogen peroxide and a bivalent metal (ie copper, cobalt or manganese) is shown to enhance the rate of phenol removal. However, in the absence of hydrogen peroxide only copper exhibited catalytic activity. Finally, a reaction mechanism involving different radical species has been proposed. From the experimental results the apparent activation energy (96.9 AE 3.5 kJ mol À1 ) and pre-exponential factor (1.6 AE 0.2 10 10 s À1 ) were calculated for hydrogen peroxide decomposition into hydroxyl radicals.