Kinetic processes of photocatalytic mineralization of alcohols on metallized titanium dioxide

The metallization of TiO2 photocatalyst with 1%Pt gave increasing rates of alcohol conversions and carbon dioxide production. A new porous powder micro-cell model was proposed. Heterogeneous reactions of photocatalytic oxidation, and final mineralizing to CO,, of methanol, ethanol in dilute (50-400 pm) aqueous solution should take place on the solid-liquid interface of the photocatalyst. It has similar kinetic behavior as reactions on the solid-gas interface of a heterogeneous catalyst. The process can be described by the Langmuir adsorption isotherm. These photocatalytic degradations can be expressed as a first-order reaction. Maximum rates of photocatalytic reactions and efficiencies can be estimated according to the calculation of surface coverage of certain compounds on TiO2. Because ethanol have the double coverage of methanol at same concentration, it is presumed that methanol and ethanol have the same adsorption state of the end-group on catalyst surfaces. In a closed reactor, if oxygen pressure was controlled at 76 cm H2O its reduction rate was nearly of zero order. (C) 1999 Elsevier Science Ltd. All rights reserved.