Stability of the so-called "Co-Mo-S" phase in a carbon-supported Co-Mo sulfide catalyst at very low Co/Mo ratio

Several aspects of the stability of the so-called "Co-Mo-S" phase in a fully sulfided Co(0.04)Mo(6.84)/C (wt%) catalyst have been examined by Mössbauer emission spectroscopy. The "Co-Mo-S" parameters turned out to be unchanged when the catalyst is exposed for 23 days to ambient air at room temperature. However, if this exposure to air is extended for over 100 days, the so-called "Co-Mo-S" phase was found to be oxidized to a high-spin Fe2+ phase which has no strong interaction with the "MoS2" particles. After resulfidation of the catalyst the so-called "Co-Mo-S" phase is formed again.