Catalytic ozonation of oxalic acid in an aqueous TiO2 slurry reactor

The ozonation of oxalic acid has been carried out in an agitated slurry semibatch reactor where powdered TiO2 has been used as a catalyst. The presence of TiO2 catalyst significantly improved the ozonation rate of oxalic acid compared to the results from non-catalytic ozonation. For gas flow rates higher than 121 h(-1) and agitation speed above 100 rpm, the catalytic process rate was chemically controlled. The kinetic study led to a zero-order kinetics for both the non-catalytic and catalytic ozonations. These experimental findings were corroborated by a mechanism of reactions. This kinetics also supported experimental results at different temperatures, ozone partial pressure and mass of catalyst per slurry volume. At low gas flow rate, where both mass transfer and chemical reaction controlled the process rate, the external gas to liquid mass transfer coefficient was also determined. (C) 2002 Elsevier Science B.V. All rights reserved.