Support Effects on Thiophene Hydrodesulfurization over Co-Mo-Ni/Al2O3 and Co-Mo-Ni/TiO2-Al2O3 Catalysts

Hierarchically macro-/mesoporous structured Al₂O₃ and TiO₂-Al₂O₃ materials were used as supports to prepare novel Co-Mo-Ni hydrodesulfurization (HDS) catalysts. A commercial Co-Mo-Ni/Al₂O₃ catalyst without macroporous channels was taken as a reference. The catalysts were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), energy-dispersive spectrometry (EDS), N₂ adsorption-desorption, X-ray diffraction (XRD), and temperature programmed reduction (TPR). The apparent activities of the hierarchically porous catalysts for thiophene HDS were superior to those of the commercial catalyst, which was mainly ascribed to the diffusion-enhanced effect of the hierarchically bimodal pore structure. The addition of titania to alumina in the support helped to weaken the interaction between the active phase and the support, and as a result, the novel Co-Mo-Ni/TiO₂-Al₂O₃ catalyst with a low titania loading (28%, by mass) in the support exhibited high HDS activities, even without presulfiding treatment. However, the catalyst with a high titania loading (61%, by mass) showed much lower activities, which was mostly caused by its low surface area and pore volume as well as the non-uniform distribution of titania and alumina. The kinetic analysis further demonstrated the support effects on HDS activities of the catalysts.