The Rh-1.5P catalyst exhibited the highest activity among the investigated catalysts. ► Rh2P was easily formed in catalysts with a higher P loading. ► Higher P loadings and higher reduction temperatures led to aggregation of Rh species. ► RhP2 exhibits lower catalytic activity than Rh2P. ► High HDS activity was caused by small Rh2P formation at lower reduction temperature.

Preparat ion o f no ble met al (NM) (Rh, Pd, Ru, Pt) phosphide species and t heir cat alyt ic act ivit ies for hydrodesulfur izat ion (HDS) of t hiophene w er e invest igat ed. Noble met al phosphides (NM X P Y) cat alyst s were prepared by reduct ion o f Padded NM (NM-P) support ed on silica (S iO 2) wit h hydrogen. Hydrogen co nsumpt io n peaks at around 350−700 °C, which wer e at t ribut ed t o t he for mat io n o f NM X P Y , were obser ved in t emper at ure-programmed reduct io n (TPR) spect ra of al l NM-P/S iO 2. Furt her more, X-ray diffr act ion (XRD) pat t erns o f NM-P/S iO 2 indicat e t hat NM X P Y (Rh 2 P, Pd 4. 8 P, Ru 2 P, Pt P 2) were for med by hydrogen reduct ion at high t emperat ure. The reduct ion t emperat ure st rongly affect ed HDS act ivit ies o f NM-P/S iO 2 cat alyst s. The NM-P/S iO 2 cat alyst s, ot her t han Pt , showed higher HDS act ivit ies t han NM/S iO 2 cat alyst s. The HDS act ivit y o f t he Rh-P/S iO 2 cat alyst was t he highest amo ng t hose o f NM-P/S iO 2 cat alyst s. This act ivit y was higher than that of the NiP catalyst and was t he same as t hat of pre-sulfided CoMoP/Al 2 O 3 cat alyst. Furt her more, t he Rh-P/S iO 2 cat alyst showed st able act ivit y even aft er react ion for 30 h. The XRD, t ransmiss io n elect ron microscopy (TEM), and energy disper sive X-ray spect roscopy (EDS) result s revealed t hat t he for mat io n o f sma ll Rh 2 P part icles and suit able P addit io n t o for m Rh 2 P caused t he high HDS act ivit y o f t he Rh-P cat alyst .

The effects of the support on active site formation and hydrodesulfurization (HDS) activity of Rh2P catalyst were examined, using metal oxides (MOx), such as SiO2, TiO2, Al2O3, MgO and ZrO2, as the support. Rh2P was formed on MOx support after reduction of supported rhodium and phosphorus (Rh _ P) catalysts. However, differences in the formation temperatures of Rh2P were observed by changing the MOx support. Furthermore, the HDS activities of the supported Rh _ P catalysts strongly changed with higher reduction temperature. The order of HDS activities of Rh _ P/MOx catalysts reduced at optimal temperatures was SiO2 ~ TiO2 ~ Al2O3 MgO ZrO2. The TOF of Rh _ P/MOx catalysts was enhanced by increasing the reduction temperature to form Rh2P. The order of TOF of supported Rh2P catalysts was TiO2 ZrO2 Al2O3 SiO2 MgO, and this order disagreed with that of thiophene conversion. The high TOF of Rh _ P/TiO2 catalyst may be explained by formation of partially sulfided TiO2 in the HDS reaction. The low TOF of Rh _ P/MgO catalyst was attributed to the basicity of the support with low sulfur tolerance.