Kinetics of cobalt-molybdate-catalyzed reactions of SO 2 with H 2S and COS and the hydrolysis of COS

Abstract

The following reactions: SO 2 + 2 H 2S ⇌ 2 H 2O + 3 x S x , (a) SO 2 + 2 COS ⇌ 2 CO 2 + 3 x S x , (b) COS + H 2O ⇌ CO 2 + H 2S, (c) which are important in Claus sulfur recovery process were studied over a commercial cobalt-molybdate catalyst. At 250 °C, which is close to the operating temperature for Claus catalytic reactors, the rate constants for the above reactions were 75:1:5. Considerable irreversible adsorption of SO 2 and H 2S on the catalyst was observed. Kinetically all reactions were similar in that the strongly adsorbed reactant (SO 2 and H 2O) was zero order and the other reactant (H 2S and COS) was first order. H 2SSO 2 reaction (Claus reaction) appeared to be diffusion controlled with an activation energy of 5.5 kcal/mole. No poisoning by CO 2 was observed for the COS reactions.