Enhanced effect of water vapor on complete oxidation of formaldehyde in air with ozone over MnO x catalysts at room temperature

Abstract: At room temperature, the enhanced effect of water vapor on ozone catalytic oxidation (OZCO) of formaldehyde to CO2 over MnO x catalysts and the reaction stability was reported. In a dry air stream, only below 20% of formaldehyde could be oxidized into CO2 by O3. In humid air streams (RH≥55%), ∼100% of formaldehyde were oxidized into CO2 by O3 and the reaction stability was significantly enhanced. Meanwhile, in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectra of OZCO of HCHO demonstrate that the amount of both monodentate and bidentate carbonate species on MnO x , in the dry stream, increased gradually with time on stream (TOS). However, in the humid stream, almost no accumulation of carbonate species on the catalysts was observed. To clarify the enhanced mechanism, formaldehyde surface reactions and CO2 adsorption/desorption on the fresh, O3 and O3 +H2O treated MnO x catalysts were examined comparatively. [Copyright &y& Elsevier]