ANALYSIS OF HETEROGENEOUSLY CATALYZED FREE-RADICAL OXIDATION OF PHENOL IN AQUEOUS-SOLUTION

The rate constants for free-radical initiation, uninhibited and inhibited oxidizability, and relative inhibitor efficiencies were determined in aqueous-phase phenol oxidation by the inhibitor method. The kinetics of free-radical inhibitor consumption, phenol hydroperoxide formation, and kinetic chain length growth were examined theoretically along with their implications. A method of estimating the length of the induction period and a criterion for Critical Catalyst Concentration (infinite length of the induction period—no oxidation) expectation in aqueous-phase phenol oxidation is presented. Another method for estimating CCC from the calculated kinetic chain length (kcl) in the steady-state activity regime is also presented. CCC is directly proportional to kcl and phenol hydroperoxide concentration in solution, and it is shown theoretically that CCC decreases on increasing the free-radical initiation rate constant and on decreasing the liquid-phase parameter and oxygen pressure in phenol oxidation. © 1979, American Chemical Society. All rights reserved.