A novel process of ozone catalytic oxidation for low concentration formaldehyde removal

To reduce energy costs, minimize secondary pollution from undecomposed ozone, and improve the efficiency of ozone use, a novel process of cycled storage-ozone catalytic oxidation (OZCO) was employed to remove formaldehyde (HCHO) at low concentrations in air. We applied Al2O3-supported manganese oxide (MnOx) catalysts to this process, and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts. Owing to the high dispersion of MnOx and low oxidation state of manganese, the MnOx/Al2O3 catalysts with a manganese acetate precursor and 10%-Mn loading showed good performance in both storage and OZCO stages. The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage; however, high relative humidity (RH) favored complete conversion of stored HCHO to CO2 at the OZCO stage and contributed to an excellent carbon balance. Four low concentration HCHO storage-OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3 catalyst at room temperature and a RH of 50%, demonstrating that the proposed storage-OZCO process is an economical, reliable, and promising technique for indoor air purification.