Mechanism of the catalytic oxidation of hydrogen sulfide. II. Kinetics and mechanism of hydrogen sulfide oxidation catalyzed by sulfur. [20 to 250/sup 0/C]

The kinetics of the catalytic oxidation of hydrogen sulfide by molecular oxygen have been studied in the temperature range 20-250/sup 0/C. The primary reaction product is sulfur which may undergo further oxidation to SO/sub 2/ at temperatures above 200/sup 0/C. From the kinetics of this autocatalytic reaction an oxidation-reduction mechanism was derived. The two rate influencing steps are the chemisorption of oxygen and the reaction between dissociatively chemisorbed H/sub 2/S and chemisorbed oxygen. The high activation energy for the formation of SO/sub 2/ (120 kJ mol/sup -1/) explains the high selectivity towards sulfur, although SO/sub 2/ is thermodynamically the most favored product. At temperatures above 300/sup 0/C, where the formation of SO/sub 2/ occurs readily, the SO/sub 2/ may be an intermediate in the reaction of H/sub 2/S with O/sub 2/ leading to S and H/sub 2/O.