Ozone Decomposition over Manganese Oxide Supported on ZrO2 and TiO2: A Kinetic Study Using in Situ Laser Raman Spectroscopy

Ozone decomposition on ZrO2- and TiO2-supported manganese oxide was studied using in situ laser Raman spectroscopy along with simultaneous steady-state kinetic measurements. The Raman spectra showed the presence of an adsorbed peroxide species for both catalysts under reaction conditions. The experimental data were well represented by a nonuniform surface kinetic treatment that assumed that the activation energies of adsorption and desorption were linear functions of the surface coverage of the peroxide species. Steady-state reaction rates were monitored for varying ozone partial pressure (0.6–3 kPa) and temperature (293–343 K). The reaction order with respect to ozone partial pressure for the ZrO2-supported sample was 0.98 and that for the TiO2-supported sample was 0.85. At zero surface coverage of the peroxide species, the activation energy for adsorption was 6 and 7 kJ/mol for the ZrO2- and TiO2-supported catalysts, respectively. The activation energies for desorption at zero coverage were 62 and 44 kJ/mol, respectively, for the same catalysts. The difference in ozone decomposition activity for the catalysts was primarily due to the difference in desorption kinetic parameters.