Influence of inert gases on the catalytic oxidation of SO₂

A study was made of the influence of diluent gases on the reaction rate and activation energy of the oxidation of sulfur dioxide over vanadium pentoxide catalyst, an effect noted by Baron, Manning, and Johnstone in 1952. Results confirmed the occurrence of the effect in a still lower temperature range (350–470 °C). Using non-adsorbing gases, helium and argon, the effect was demonstrated to be free from chemisorption of the diluents.Data on activation energy vs. molecular weight of the gas phase, using helium and argon, were in qualitative agreement with predictions based on a momentum-exchange model of Baron etal. However, comparison of rates obtained with argon (monatomic) and nitrogen (diatomic) as diluents, combined with independent study of the rate controlling steps, casts doubt on the adequacy of the explanation offered by Baron etal.