Metal Oxides as Catalysts and Adsorbents in Ozone Oxidation of NOx

NOx represents an important group of pollutants that are formed in fuel combustion. As these pollutants cause significant environmental problems, removal of NOx from exhaust gases is necessary. The present study investigated the influence of metal oxide powders on the removal of NOx by oxidation with ozone. The aim of the study was to compare the catalytic effect of TiO2, Al2O3, and Fe2O3 and to investigate the dependence of the effective rate constant on temperature. NOx (400 ppm) and a variable concentration of ozone in a mixture of N-2 and O-2 was directed through the catalyst chamber and heated to 60-140 degrees C. The addition of metal oxides resulted in a significant increase in the efficiency of the oxidation of NO to N2O5. Fe2O3 had the largest effect with a maximum of an approximately 3-fold increase in the effective rate constant at 100 degrees C. At the same time Fe2O3 had the lowest NOx adsorption capacity. In the case of all metal oxides, oxidation of NO to N2O5 caused an abrupt increase in adsorption of NOx.