Phenol oxidation in supercritical water was carried out in a tubular l
aboratory-scale reactor operated at a temperature range of 380 degrees
C to 450 degrees C and pressures between 230 and 265 bar The phenol f
eed concentrations were between 500 and 1,000 mg/L, while oxygen was f
ed into the reactor at 50 to 1,000% of the stoichiometric amount neede
d to oxidize phenol completely to carbon dioxide. Phenol conversions f
rom 16 to 96% were attained as the reactor residence times varied from
15 to 203 s. The oxidation obeys a parallel-consecutive reaction sche
me that involves multiring, intermediate products such as phenoxy-phen
ol, biphenol, dibenzo-dioxin, maleic acid, and succinic acid. Experime
ntal results showed that the phenol disappearance rate is represented
well by a power-law kinetic model in which the rate is proportional to
the 0.4 power of the oxygen mole fraction and roughly linearly propor
tional to the phenol mole fraction. The pressure effect on the disappe
arance rate was appropriately accounted for by introducing the molar v
olume of the reaction mixture, which was readily calculated by an equa
tion of state. Total organic carbon reduction can be estimated by a lu
mped kinetic equation. In the P-T region the activation energy of the
phenol disappearance was 124.7 kJ/mol.