Kinetics of reverse water gas shift (RWGS) reaction on metal disulfide catalysts

Abstract The hydrogenation of CO 2 was studied on disulfides of molybdenum and tungsten by comparison with that on the group VIII metals of Fe, Co, and Ni supported on Al 2 O 3 . The hydrogenation activity was lower on the disulfides on a per active site of catalyst basis than on the transition metals, however, the selective reverse water gas shift (RWGS) reaction (CO 2 + H 2 → CO + H 2 O) was observed on the disulfides. The selectivity was close to ca. 100% in the reaction conditions examined. The rate was expressed by the equation: r = kP 0.61–0.73 CO 2 P 0.36 H 2 on the disulfides, and the activation energy was ca. 18.0–19.1 kcal mol −1 . The disulfides exhibited little activities for the hydrogenation of CO (viz. CO + 3H 2 → CH4 + H 2 O) and also for the disproportionation of CO (viz. 2CO → C + CO 2 ). These results were in contrast to those for the transition metals where high activities were observed for both reactions, suggesting that the retardation of CO bond cleavage in the CO molecule produced by the CO 2 hydrogenation must be the cause for the selective hydrogenation of CO 2 to CO on the disulfides. The effect of supports on the hydrogenation of CO 2 was also investigated for MoS 2 . The reaction rate on a per active site of catalyst basis was not influenced by the supports, suggesting that the CO 2 H 2 reaction is insensitive to the morphology of MoS 2 supported on metal oxides.