Catalytic wet oxidation of phenol: Kinetics of phenol uptake

Catalytic phenol oxidation in aqueous phase under intermediate temperature and pressure has been carried out in order to determine the kinetic model o f phenol uptake rate. The catalyst employed here was a commercial one based on copper supplied by Engelhard (Cu-0203T). Operational variables have bee n studied in the following ranges: temperature from 127 to 180 degreesC, ox ygen pressure from 3.2 to 16 bar, initial phenol concentration from 680 to 1200 ppm, and catalyst concentration from 0 to 1550 g/L of liquid phase. Be cause of the wide interval here employed for the catalyst concentration, tw o experimental setups have been used: a basket stirred tank reactor (BSTR) with the liquid phase in batch and an integral fixed-bed reactor (FBR) with co-current upflow of gas and liquid phases. An important influence of the reaction in the bulk liquid was obtained in both types of reactor. This fac t has been taken into account in the kinetic model according to different a pproaches. The first approach was a breakup of the reaction rate in two kin etic expressions, considering the homogeneous and heterogeneous contributio n separately; the second approach was empirical where the reaction tate is a potential function of the catalyst concentration. It was found that the e xtent of reaction in the bulk liquid is also influenced by the catalyst con centration and that the first approach is not able to adequately predict th e experimental results. Finally a kinetic model, based on the second approa ch, was discriminated, with a power law for the catalyst concentration with an order about 0.4. This model fits quite well the experimental data obtai ned in both experimental setups, BSTR and FBR, throughout the wide range of variables studied.