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Catalysis Letters

, Volume 11, Issue 2, pp 183–190 | Cite as

Effects of SO2 on the alkane activity of three-way catalysts

  • Graham P. Ansell
  • Stanislaw E. Golunski
  • Helen A. Hatcher
  • Raj R. Rajaram
Article

Abstract

Over current Pt-Rh/CeO2-Al2O3 catalysts, the conversion of alkanes occurs by two principal mechanisms: direct oxidation (HC + O2) and steam reforming (HC+H2O). Sulphur dioxide can influence both these mechanisms. Direct oxidation, which predominates when the exhaust-gas is fuel-lean, ispromoted by the adsorption of SOx species by the support. Under fuel-rich atmospheres, the presence of SO2 severelyinhibits steam reforming. The poisoning is associated with the formation of S2− on the platinum and of SO 4 2− on the support, but there is no indication of S-species being retained by the rhodium. It is proposed that each of the two mechanisms is sensitive to a different type of interaction at the metal-support interface. Direct oxidation is enhanced by the transfer of electrons from the precious metal to the support; steam reforming occurs at interfacial sites, which can be blocked by adsorbed SOx species.

Keywords

Three-way catalysts sulphur dioxide poisoning promotion oxidation steam reforming 

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Copyright information

© J.C. Baltzer A.G. Scientific Publishing Company 1991

Authors and Affiliations

  • Graham P. Ansell
    • 1
  • Stanislaw E. Golunski
    • 1
  • Helen A. Hatcher
    • 1
  • Raj R. Rajaram
    • 1
  1. 1.Jchnson Matthey Technology CentreReadingUK

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