Investigation Of Ozone Oxidation For Formaldehyde Removal Over MnO_x/γAl₂O₃ Catalysts

As one of the typical volatile organic compounds, HCHO is a great threat to human health. HCHO could be oxidized at room temperature using non-noble metal catalysts by ozone catalytic oxidation. In this paper, we studied ozone catalytic oxidation and "HCHO storage-Ozone oxidation" for HCHO removal in simulated air. The results are listed as follows:The performance of ozone decomposition over MnOx/Al2O3 catalysts is studied. The increase of Mn loadings shows an enhanced effect of ozone decomposition while Mn precursor has little effect of it. The increase of humidity can enhance the performance of ozone decomposition.The performance of ozone catalytic oxidation of HCHO over MnOx/Al2O3 catalysts is studied.10 wt% MA/Al2O3 catalysts have the better performance for HCHO oxidation than other catalysts at room temperature. When the mole ratio of O3 to HCHO is over 2 (the stoichiometric ratio), HCHO could be totally oxidized to CO2, while HCHO to CO2 conversion decreases as the decrease of the mole ratio of O3 to HCHO when it is below stoichiometric ratio. HCHO to CO2 conversion increases from 52.4% to 65.2% as relative humidity increases from 20% to 80%."HCHO storage-ozone oxidation" approach is studied for indoor HCHO removal in synthetic air. MA/Al2O3 catalysts have a better performance than MN/Al2O3 catalysts in both storage stage and OZCO stage. The increase of Mn loadings shows a significantly enhance in HCHO breakthrough capacity. In OZCO stage, the carbon balance increases at first and then decreases as the increase of Mn loadings.10 wt% MA/Al2O3 catalysts are the optimal catalysts to guarantee both high HCHO breakthrough capacity and high carbon balance and CO2 selectivity. The effect of relative humidity is also investigated. Compared with supports, MnOx/Al2O3 catalysts have better performance in HCHO storage and water resisitance. HCHO breakthrough capacity decreases as the relative humidity increases, while in OZCO stage, the stored HCHO could be more easily oxidized with higher relative humidity. MnOx/Al2O3 catalysts also exhibit good stability during "HCHO storage-Ozone oxidation" cycles.