Catalytic oxidation of substituted phenols in a trickle bed reactor

The catalytic wet oxidation was studied of phenol, 2-aminophenol, salicyclic acid and 5-sulfosalicylic acid performed in a laboratory trickle bed reactor. A three-phase high-pressure catalytic reactor with an inside diameter of 18 mm and length of catalytic bed of 200 mm was operated at temperatures 90-180 degrees C, pressures 2-7 MPa and liquid space velocity 1-10 h(-1). Simultaneously, the catalytic activity and the stability of extruded active carbon black Chezacarb(R) and active carbon Chemviron(R) were tested. At a comparable activity, the active carbon Chemviron(R) exhibited a greater mechanical strength and stability. The influence of phenol substituents on the oxidation conversion corresponded to their inductive effect: The electropositive amino group supported the oxidation, on the contrary, the presence of carboxy and sulfo groups on aromatic ring led to only low conversion. The complications on evaluating the experimental data are caused by the non-isothermal temperature profile along the catalyst bed, the non-ideal oxygen dissolution in aqueous solutions and especially the hydrodynamic effect of flow rate on the degree of catalyst wetting and thus on the entire effectiveness of the oxidation process.