Noble Metal Phosphides as New Hydrotreating Catalysts: Highly Active Rhodium Phosphide Catalyst

Abstract

Metal phosphide has been widely investigated as a hydrotreating catalyst. The preparation and performance of noble metal phosphide catalyst was examined to develop new phosphide hydrotreating catalysts. The supports affect reducibility of phosphate as a P precursor. Since phosphate does not strongly interact with SiO₂ and TiO₂ supports, Rh₂P was easily formed on these supports. Furthermore, formation of Rh₂P enhanced the hydrodesulfurization (HDS) activity of supported Rh–P catalyst. The type of noble metal (NM) and P/NM ratio also strongly affect formation of noble metal phosphide and HDS activity. Excess P facilitates formation of noble metal phosphides at lower reduction temperature. In contrast, excess P causes the aggregation of noble metal phosphide and formation of phosphorus rich noble metal phosphide. Rh–1.5P/SiO₂ catalyst had high and stable activity for HDS reaction. Furthermore, this catalyst showed significantly higher hydrodenitrogenation (HDN) activity than sulfided NiMoP/Al₂O₃ catalyst. Therefore, Rh₂P has great potential as a new hydrotreating catalyst.