Fj. Rivas et al., DEVELOPMENT OF A MODEL FOR THE WET AIR OXIDATION OF PHENOL BASED ON AFREE-RADICAL MECHANISM, Chemical Engineering Science, 53(14), 1998, pp. 2575-2586
A model for the wet air oxidation of phenol is proposed, based on elem
entary radical reactions that are known to occur in the oxidation proc
ess. By applying this model to associated experimental data, unknown r
ate constants have been calculated using numerical techniques to solve
the system of differential equations that describes the proposed mech
anism. The activation energy and pre-exponential factor for the elemen
tary reaction between phenol and the phenoxyperoxyl radical (PhOO .) w
ere estimated to be 47 +/- 3 kJ mol(-1) and 1.7 +/- 0.1 x 10(10) l mol
(-1) s(-1) respectively, while values of 126 +/- 4 kJ mol(-1) and 4.7
+/- 0.2 x 10(10) s(-1) were found for the decomposition of phenoxy hyd
roperoxide (PhOOH). The operating parameters of temperature, oxygen co
ncentration, pH and addition of free radical promoters (H2O2) have bee
n studied, and in general, a good agreement has been obtained between
experimental data and calculated concentration profiles. According to
the proposed mechanism, it is shown that hydroxyl radicals (OH .) and
phenoxyperoxyl radicals (PhOO .) are primarily responsible for the des
truction of phenol, with perhydroxyl radicals (HO2.) having a less sig
nificant role to play in the process. The principles described in this
paper may be applied to understand the wet air oxidation mechanism of
other organic compounds. (C) 1998 Elsevier Science Ltd. All rights re
served.