Catalytic wet oxidation of phenol: Kinetics of the mineralization rate

Phenol mineralization in the aqueous phase was studied employing oxygen as the oxidant. The reaction was carried out at intermediate oxygen pressures (3.2-16 bar) and temperatures (127-180 degreesC) employing a commercial cat alyst supplied by Engelhard (Cu-203T). Two experimental setups were used: a basket stirred-tank reactor (BSTR) with the liquid phase in batch and an i ntegral fixed-bed reactor (FBR) with concurrent upflow of the gas and liqui d phases. These two apparatuses allowed the catalyst concentration to be ch anged over a wide range (4-1150 g/L) so that the influence of this variable could be more accurately determined. It was found that the reaction takes place to a significant extent both in the liquid phase and on the catalyst surface. A kinetic model for phenol mineralization was discriminated on the basis of a two-stage power-law kinetic expression. The first stage corresp onds to the induction period, and the second to the steady state. This mode l was able to predict accurately the experimental results over the entire r ange of the variables studied. The catalyst concentration was included in t his model with a power-law order of about 0.5 found for both the induction and steady-sate regions.