Observation of Phase Transformations during Sulfidation: An Ex-Situ Study Involving a Promoted Experimental Catalyst

Abstract

The stepwise, ex-situ gas phase (0.1 MPa 10% H 2 S/ 90% H 2 ) sulfidation of an unsupported, Co-promoted MoS 2 catalyst from an experimental Co 2 MoO x precursor is examined. Time−temperature transformation studies involving X-ray diffraction and transmission electron microscopy yield insights into the evolution of Co 9 S 8 and MoS 2 structures and the associated phase partitioning phenomena that occur during sulfidation. Discrete CoS x (initially Co 4 S 3 and then Co 9 S 8 ) structures form prior to the MoS 2 particle development. CoS x growth continues as MoS 2 slabs begin to form. However, substantial CoS x particle formation is essentially completed even as MoS 2 growth continues, suggesting that a significant amount of the Co promoter is consumed in the CoS x phase prior to the complete MoS 2 particle development. These data indicate that it is only those Co ions unable to diffuse into the CoS x phase that are ultimately available to create active sites by decorating the S-edges of the MoS 2 particles.

The critical role of solvent polarity in the preparation of tube-like Co–Mo sulfide catalysts for the hydrodeoxygenation of stearic acid

“…The diffraction peak intensity of Co 9 S 8 gradually increased with increasing solvent polarity (Table S1, ESI†), which to some extent indicates that increasing the solvent polarity promoted the growth of the Co 9 S 8 crystallites. 19…”

“…S1, ESI †), which to some extent indicates that increasing the solvent polarity promoted the growth of the Co 9 S 8 crystallites. 19 Morphology and structure analysis Fig. 2A shows the SEM image of the Co-Mo oxide precursor, which consisted of rod-like particles with a cross-section close to a square, and the rod-like particles were composed of smaller particles.…”