Mechanism of the heteroge-neous reaction of carbonyl sulfide with typical compo-nents of atmospheric aerosol

Abstract

The homogeneous reactions of carbonyl sulfide (COS) with OH and oxygen radicals have been studied thoroughly. However, the heterogeneous chemical processes involving COS and atmospheric particles are still not well understood. The reactivity of COS with atmospheric mineral oxides such as A12O3, CaO, SiO2, Fe2O3 and MnO2 has been explored. The gaseous and solid products of the reaction were identified by in situ Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy respectively. The mechanism and kinetics of the heterogeneous reaction are also discussed in detail. The results showed that COS can be catalytically oxidized on the surfaces of different atmospheric mineral oxides with the products of CO2, S and SO42−. The reactivity of the oxides with COS differs widely. A12O3 exhibits excellent reactivity, and Fe2O3 is inferior to it. CaO shows weak reactivity, while SiO2 and MnO2 nearly have no activity for the oxidation of COS. The absorbed oxygen and hydroxyls on the surfaces of the oxides are the main active sites in the conversion of COS. When O2 in the experimental system was much excessive, the catalytic oxidation on the surface of A12O3 is a pseudo first order reaction with respect to COS. The acidity of A12O3 influences the reactivity significantly. The rate constants of the catalytic oxidation of COS on the surface of basic, neutral and acidic A12O3 are respectively 1.51×10−4, 9.81×10−5 and 3.06×10−66 s−1.