Promoted oxidation of phenol in aqueous solution using molecular oxygen atmild conditions

Wet oxidation with molecular oxygen at mild conditions. (temperature < 200 degrees C, pressure less than or equal to 2 MPa) is an economically attract ive pretreatment step Sor non-biodegradable aqueous waste streams. In order to overcome the low reactivity of molecular oxygen towards organic molecul es at these mild process conditions, an initiator was used in combination w ith ferrous ions in the acidic range. The promoted oxidation of phenol in a queous solution was investigated in a 4 liters stirred autoclave. It was po ssible to degrade the Phenol at temperatures as low as 100 degrees C withou t observing an induction time. The remaining solution contained mainly acet ic and formic acid and was well biodegradable. The oxidative behavior of the oxygen/phenol system could be explained using the well-known autoxidation mechanism Sor aliphatic molecules. 4-hydroxype roxy-phenol is suggested as a key intermediate. Measured products are p-ben zoquinone, hydroquinone, catechol, maleic, oxalic, pyruvic, formic, and ace tic acid. Dimers could also be identified in sample extracts. A global path way including all identified products is presented.