Microkinetics of water-gas shift over sulfided Mo/Al₂O₃ catalysts

A microkinetic model was developed to explain the catalysis of the water - gas shift reaction by sulfided, alumina-supported molybdenum. In this model, the reaction takes place through a regenerative (reduction-oxidation) scheme wherein the catalyst surface is alternately oxidized by water and then reduced by carbon monoxide. The surface of the catalyst is equilibrated with gas-phase H₂S under all reaction conditions studied. Coverages predicted by the model are consistent with the adsorption behavior of molybdenum sulfide catalysts. Simulations indicate that the effects of steam and H₂S levels are closely related. A maximum in CO conversion with increasing steam level may only occur at certain H₂S levels, and the ordering of CO conversion with increasing H₂S levels may invert as the steam level is changed.