Mechanism Study of Organic Sulfur Hydrogenation over Pt- and Pd-Loaded Alumina-Based Catalysts

The hydrogenation of organic sulfur (CS₂) present in industrial off-gases to produce sulfur-free hydrocarbons and H₂S can be achieved by using noble-metal catalysts. However, there has been a lack of comprehensive investigation into the underlying reaction mechanisms associated with this process. In this study, we have conducted an in-depth examination of the activity and selectivity of Pt- and Pd-loaded alumina-based catalysts, revealing significant disparities between them. Notably, Pd/Al₂O₃ catalysts exhibit an enhanced performance at low temperatures. Furthermore, we have observed that CS₂ displays a higher propensity for conversion to methane when employing Pt/Al₂O₃ catalysts, while Pd/Al₂O₃ catalysts demonstrate a greater tendency for coke deposition. By combining experimental observations with theoretical calculations, we revealed that the capability of H₂ spillover along with the adsorption capacity of CS₂, play pivotal roles in determining the observed differences. Moreover, the key intermediate species involved in the methanation and coke pathways were identified. The intermediate CH₂S* is found to be crucial in the methanation pathway, while the intermediate CSH* is identified as significant in the coke pathway.