Continual catalytic wet oxidation of phenol and its derivatives as a suitable chemical pretreatment before a biological treatment process was investigated. The evaluation of (i) the inÑuence of amino-, carboxy-and sulfo-phenol substituents on the course of the oxidation of hydroxyl-aromatics, (ii) the catalytic ability of an active carbon, and (iii) the inÑuence of reaction conditions, viz. temperature (120È160¡C) and oxygen partial pressure (2È5 MPa) in the continuous trickle bed reactor, is presented. The active carbon type catalyst seems to be active enough for phenol oxidation, but it is not so e †ective for aromatic acids. The results of trickle bed operation were strongly inÑuenced by hydrodynamics, viz. wetting efficiency. An insufficient catalyst wetting compensates for an e †ect of residence time in the bed and undesirable Ñuctuation of conversion appears at the low liquid velocities which are typical for waste water treatment processes. It is possible to achieve an optimal value of reactor productivity. ( 1998 SCI

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Catalytic wet oxidation carried out in a continual three-phase trickle-bed reactor contributes to the sustainability of chemical technology. It was found that the hydrodynamics and the masstransfer of reactants could have a signi®cant impact on the performance of the trickle-bed reactor. An aqueous phenol oxidation was tested at different temperatures and liquid feed rates and the activities of both the CuO-supported catalyst and the extruded active carbon were compared. To avoid the impact of liquid maldistribution, a bed of catalyst particles diluted with ®ne glass spheres was also used. Ratelimited conditions of both liquid-and gas-phase presented reactants were determined. Under the conditions of gas component transfer limitation, a better wetting of the diluted catalyst bed can lead to a worsening in the reactor performance due to the lower overall reaction rates.

The catalytic effects of hydrophilic granulated active carbon black Chezacarb have been tested in the oxidation of dilute (5 000 ppm) aqueous solutions of phenol. The research was focused on combined utilization of sorption and chemical (oxygen functional groups) properties of carbon black which support formation of free radicals in oxidation and on the catalytic effects of metals (Fe, Ni and V) present in the sorbent mentioned. The oxidation was carried out in a stainless steel autoclave of 1.25 l capacity. The reaction temperatures and the total pressures varied in the intervals of 120-160 °C and 3-5 MPa, respectively. The reaction mixture was analyzed by means of HPLC with UV detection (254 nm). The experimental data were evaluated by means of the ASPEN PLUS 9.2 program. The model of laboratory autoclave involved the reaction kinetics as well as the phase equilibria and dissolution of oxygen and carbon dioxide in the reaction mixture. Although the active carbon black shows a lower catalytic activity than the usual copper catalyst in the wet oxidation, it has the advantage of avoiding the undesirable releases of heavy metals in waste waters, which escapes accompany the application of copper catalysts.