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SURFACE REACTIONS OF OXIDES OF SULFUR
Citation:
Lunsford, J. SURFACE REACTIONS OF OXIDES OF SULFUR. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/7-79/088 (NTIS PB297410), 1979.
Description:
Surface reactions of several sulfur-containing molecules have been studied in order to understand the mechanism by which sulfate ions are formed on atmospheric aerosols. At 25C the heterogeneous oxidation of SO2 by NO2 to sulfuric acid and sulfate ions occurred on hydrated silica and silica-alumina surfaces. The oxidation of SO2 by O2 was undetectably slow on these surfaces; however, the reaction was catalyzed by Mn(+2) ions in a Y-type zeolite. In this case the only reaction product was a SO4(-2) species which was strongly bound in the zeolite micropores. Molecular oxygen also reacted with H2S on zeolites and magnesium oxide. The primary reactions on zeolites resulted in the formation of elemental sulfur; whereas, on MgO a variety of products were observed including elemental sulfur, sulfide ions, sulfite ions and a number of paramagnetic ions such as S3(-), S2O(-) and S sub n(-). Experiments were also carried out to identify and to determine the mechanism by which S2O(-) and H2S2(-) are formed on MgO. To establish the geometric structure of the S2O(-) ion and other paramagnetic sulfur-containing molecules on MgO, CNDO semiempirical calculations were carried out to determine theoretical values of g tensors and spin densities as a function of bond angles and bond lengths.