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

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.