Catalytic wet air oxidation of phenol over platinum and ruthenium catalysts

Active platinum and ruthenium catalysts have been developed that are also highly selective in catalytic wet air oxidation (CWAO) of phenol. CWAO of phenol was studied using a trickle bed reactor over temperatures 393 and 473 K under total pressure of 5 and 8 MPa at LHV = 0.5-6 h(-1). The initial phenol concentration was ca. 50 mol/m(3) and the initial COD of the solution was ca. 12 kg O-2/m(3). Molar ratio of oxygen to phenol was ca. 38:1. A kinetic analysis of phenol conversion and COD changes has been elaborated based upon lumped reaction network according to which oxidation of phenol proceeds substantially via two routes: (1) directly to carbon dioxide, and (2) through intermediates which are difficult to oxidize over the catalysts studied. Estimates of chemical oxygen demand for the lumped intermediates amount to 64+/-30 g O-2/mol confirming the literature information that these are carboxylic acids, probably with predominant content of acetic acid that is most refractory at CWAO conditions. Power law kinetic equations describe satisfactorily CWAO of phenol over the catalysts of this work. Most activation energies range from 58 to 107 kJ/mol. Reaction orders for phenol range from 0.94 to 2.0 and these for oxygen from 0.22 to 0.85. (C) 2003 Elsevier B.V. All rights reserved.