Sulfidation reactions in catalysis
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The company uses sulfur-resistant CoMo catalysts. The reactions involved are likely CoO + H2S → CoS + H2O, with ΔH0298 = -13.4 KJ/mol; and MoO3 + 2H2S + H2 → MoS2 + 3H2O, with ΔH0298 = -48.1 KJ/mol. Let’s discuss what changes occur in the valence states of Co and Mo before and after sulfidation, especially the change in Co’s valence state during sulfidation – it’s a bit complicated
In CoO, the Co has a +2 oxidation state, and in CoS as well, the Co also has a +2 oxidation state; there is no change in the oxidation state. In MoO3, Mo is in the +6 valence state, while in MoS2, Mo is in the +4 valence state.