Preparation, characterization of Mo catalysts supported on Ni- containing calcium deficient hydroxyapatite and reactivity for the thiophene HDS reaction

Université Hassan II, Faculté des Sciences Aïn-Chock, BP. 5366, Mâarif Casablanca, Maroc

Abstract

Ni-containing Calcium Hydroxyapatite (NiCaHAp; 3.31 wt.% Ni) was synthesized by coprecipitation and used as catalyst support. Molybdenum was supported on NiCaHAp by impregnation using ammonium heptamolybdate. The prepared catalysts Mo(x)/NiCaHAp (x: 2 to 8 wt % in Mo) were characterized by elemental analysis, XRD, FT-IR, N₂ adsorption-desorption and TEM-EDX. The catalysts were sulfided in-situ at 673 K under flowing H₂S/H₂ (15 Vol.% H₂S) and tested in hydrodesulfurization (HDS) of thiophene at 673 K. The main XRD peaks of hydroxyapatite CaHAp phase were observed in all samples and a peak due probably to crystalline MoO₃ phase was also identified from the results. However, no crystalline phase of NiO was found for the catalysts, which showed its Ni species were highly dispersed. The sulfided catalysts Mo(x)/NiCaHAp presented are active in HDS of thiophene, despite the presence of some large MoO₃ crystallites and incomplete sulfidation. This activity may be due to interaction of NiO and MoO₃ on CaHAp resulting in the formation of Ni-Mo-S phase under flowing H₂S/H₂. When the molybdenum content increased the HDS activity increasead slightly, which was caused by the agglomeration of MoO₃. The Mo(8)/NiCaHAp catalyst is about two times less active for thiophene HDS than the commercial NiMoP/Al₂O₃.