Hydrodesulfurization of 4,6-Dimethyldibenzothiophene over CoMo Catalysts Supported on γ‑Alumina with Different Morphology

Nanostructured γ-alumina with two different morphologies (rod-like and cube-like) was used as support for CoMo hydrodesulfurization catalyst. Both γ-aluminas were prepared by thermal decomposition of ammonium aluminum carbonate hydroxide precursor, which was synthesized by a convenient hydrothermal method at two pH values. Fourier transform infrared spectroscopy of prydine adsorption, thermogravimetric analysis, and ²⁷Al magic angle spinning (MAS) NMR showed that the rod-like γ-alumina exhibited a lower acidity than the cube-like γ-alumina. The result of X-ray diffraction and temperature-programmed reduction indicated that CoMo oxidic catalysts supported on the rod-like γ-alumina presented higher reducibility compared to those of cube-like γ-alumina, because more β-CoMoO₄ was formed on the surface of the rod-like γ-alumina than that of the cube-like γ-alumina. After sulfidation, a large stack with slightly longer MoS₂ slabs was formed on the rod-like γ-alumina supports, thereby creating a catalyst with higher hydrodesulfurization activity and hydrogenation selectivity. The morphology of γ-alumina has an influence on the activity and selectivity of the as-synthesized CoMo catalyst