Heterogeneous oxidation of carbonyl sulfide on atmospheric particles and alumina.

Heterogeneous oxidation of carbonyl sulfide (OCS) on atmospheric particles and alumina (Al2O3) was investigated in a closed system and a flowed system using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). At room temperature, OCS could be catalytically oxidized on the surface of atmospheric particles and Al2O3 to form gas-phase CO2 and surface sulfate (SO4(2-)), sulfite (HSO3-), and hydrogen carbonate (HCO3-) species. The real atmospheric particles were characterized using X-ray fluorescence (XRF) and the Brunauer-Emmett-Teller (BET) method. As a simplified model, Al2O3 was used to study the reaction mechanism of heterogeneous oxidation of OCS. The hydrogen thiocarbonate surface (HSCO2-) species, an intermediate formed in the reaction of OCS with surface hydroxyl (OH), could only be observed on the prereduced Al2O3 sample. The experimental results also indicate that surface oxygen containing species on the atmospheric particle sample and the Al2O3 sample might be the key reactant for OCS oxidation. A reaction mechanism of heterogeneous oxidation of OCS on Al2O3 surface is discussed.