Kinetics of 4-Methoxybenzyl Alcohol Oxidation in Aqueous Solution in a Fixed Bed Photocatalytic Reactor

The photocatalytic oxidation of 4-methoxybenzyl alcohol in water was performed in a fixed bed continuous annular reactor by using a home-prepared TiO2 catalyst supported on Pyrex glass beads. The investigation was aimed to modeling the complex kinetics of the photoprocess which occurs through two parallel pathways: (i) partial oxidation to the corresponding aldehyde and (ii) total oxidation to CO2 and H2O. On these grounds, the influence of liquid flow rate, inlet concentrations of alcohol and oxygen, catalyst amount, and irradiation power on the photoreactivity were studied. A kinetic model like that of Langmuir-Hinshelwood satisfactorily fitted the experimental results and allowed determination of the values of model parameters. It was found that all these parameters are positively affected by an increase of radiant energy absorbed by the catalyst. All the reactivity results indicate that the partial oxidation pathway is favored by the low flux of absorbed photons and by low oxygen coverage on the TiO2 surface; opposite conditions favor the mineralization pathway.