CATALYTIC WET AIR OXIDATION OF PHENOL USING CeO₂ AS THE CATALYST. KINETIC STUDY AND MECHANISM DEVELOPMENT

ABSTRACT

Using a CeO₂ catalyst prepared from CeCl₃ ċ 7H₂O under high thermal impact, the catalytic wet air oxidation (CWAO) of phenol was effectively implemented. With initial phenol concentrations of between (400 and 2500) mg/L, and at a temperature of 160°C, the rate of phenol conversion increased with increased catalyst loading (0.2 g/L–1.0 g/L) and oxygen pressure (0.5 MPa–1.5 MPa). Even at an initial concentration of 2500 mg/L, conversion of phenol was as high as 95% after 3 h reaction. The effect of phenol concentration, catalyst loading, and oxygen pressure on the initial rate of phenol conversion was evaluated in a kinetic study. The initial rate equation derived from kinetic study is: R _o = k ₁ × [Ph]^1.3–1.4 × W^0.5–0.6 × P_{o 2} ^0.9–1.1, where k ₁ is a rate constant, and [Ph], W and P_{o 2} refer to phenol concentration, catalyst loading and oxygen pressure, respectively. A free-radical involved reaction mechanism was proposed and an initial rate expression based on this mechanism was derived: R _o = k ₂ × [Ph]^1.5 × W^0.5, where k ₂ is also a rate constant. Fitting of experimental data with the theoretically derived initial rate equation resulted in good correlation: the coefficient is greater than 0.99.

Keywords:

• CeO₂
• CWAO
• Phenol
• Kinetic study
• Reaction mechanism

Acknowledgments