Aqueous-Phase Oxidation: Rate Enhancement Studies

In an effort to discover techniques for increasing intrinsic aqueous-phase oxidation rates, the rate of m-xylene oxidation has been studied at 400–473 K and 13.8 MPa in the presence of hydrogen peroxide and phenol. At these conditions, hydrogen peroxide decomposes instantaneously to produce free radicals necessary to initiate the m-xylene oxidation, thereby greatly reducing or even eliminating the induction period normally associated with m-xylene oxidation. Once the peroxide radicals are consumed, however, the m-xylene oxidation rate in the rapid reaction phase returns to the values expected in the absence of peroxide. Addition of more easily oxidized phenol to m-xylene produces a synergizing effect in which cross-initiation greatly enhances the m-xylene oxidation rate. The length of the m-xylene induction phase is greatly reduced, approaching the intrinsic phenol induction time, and the rapid reaction-phase rate constant for m-xylene can be increased by almost 2 orders of magnitude compared to the rate constant for m-xylene reacting alone.