Tailoring the surface characteristic of alumina for preparation of highly active NiMo/Al2O3 hydrodesulfurization catalyst

• Hydrothermal treatment can tailor the distribution of alumina hydroxyl groups.
• Hydrothermal treatment can change the Al(IV)/Al(VI) ratio of alumina.
• The surface properties of tailored alumina facilitate the sulfiding of Ni and Mo.
• The (Ni)MoS2 slabs grow accordingly with the increasing γ-Al2O3 crystallite size.
• NiMo supported on moderately crystallized γ-Al2O3 exhibits better HDS activity.

Tailoring alumina surface via hydrothermal treatment route was investigated so as to design highly active NiMo/Al2O3 hydrodesulfurization catalysts. First, two types of tailored γ-Al2O3 supports were prepared from hydrothermally treated pseudo-boemhite or hydrothermally treated γ-Al2O3, respectively. The characterization results showed that compared with reference γ-Al2O3, the tailored γ-Al2O3 supports have a notable increase in their crystallite size, terminal hydroxyl groups and the ratio of Al(tetrahedral)/Al(octahedral), but an obvious decrease in surface area, pore volume, and the amount of hydroxyl groups and tetrahedral cation vacancies. Metal species supported on the tailored γ-Al2O3 supports are easier to be reduced or sulfided. And for the sulfided catalysts, the average slab length and stacking number of (Ni)MoS2 obviously increase with the crystallite growth of the corresponding γ-Al2O3 supports. NiMo supported on the tailored γ-Al2O3 support obtained from hydrothermally treated pseudo-boehmite, exhibits the highest hydrodesulfurization activity for 4,6-DMDBT. It can be ascribed to its moderately crystallized particles, proper decrease in the amount of hydroxyl groups and tetrahedral cation vacancies, and more well-dispersed Ni–Mo–S active phases.

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