Sulfur Tolerance Properties of Rhodium Phosphide Evaluated by a New Temperature-programmed Sulfidation Technique

Abstract

Sulfur tolerance properties of rhodium phosphide (Rh₂P) were qualitatively and quantitatively evaluated by the temperature-programmed sulfidation (TPS) technique. The TPS profile of the Rh/SiO₂ catalyst demonstrated a peak attributed to Rh₂S₃ formation around 400 °C. The TPS profiles of P-added Rh (Rh–P) catalysts showed this peak shifted to higher temperatures and lower intensity with higher P/Rh ratio or reduction temperature. Quantitative analysis of TPS profiles revealed that the amount of reacted H₂S was remarkably lower (about 80 %) with P/Rh ratio more than 1.5, compared with Rh catalyst. The amount of reacted H₂S decreased with greater intensity of the Rh₂P peak in the XRD pattern, indicating that Rh₂P has high sulfur tolerance. Furthermore, the relationship between P/Rh ratio and S/Rh ratio (calculated from TPS profile) of Rh–P catalysts agreed with the reported S/Rh value, showing the TPS method has high validity for qualitative analysis. We conclude that the TPS technique is a superior method for evaluation of sulfur tolerance for phosphide catalysts, and Rh₂P has remarkably high sulfur tolerance compared with Rh catalyst.