Effect of direct synthesis Al–SBA-15 supports on the morphology and catalytic activity of the NiMoS phase in HDS of DBT

Abstract

A series of Al–SBA-15 (Al-15) materials was prepared by direct synthesis method with a broad range of Si/Al molar ratios (X = 40, 20, 10, 5, and 2.5), and the corresponding NiMoS/Al-15(X) catalysts were used to perform the hydrodesulfurization (HDS) reaction with dibenzothiophene (DBT). The prepared samples were characterized by N₂ physisorption, ICP-OES, powder XRD, ²⁷Al MAS NMR, H₂-TPR, pyridine-FTIR and HRTEM. Al–SBA-15(10) had the highest number of Brønsted acid sites and the total acid density of silica–alumina supports increased with Al loading. The enhanced acidity of the Al-15-type materials led to higher catalyst activity compared to those of NiMo/γ-Al₂O₃ and NiMo/SBA-15. A suitable stacking of the NiMoS slabs favors the hydrogenation reaction of DBT while introduction of Al into the silica supports can help the hydrogenolysis of the C–S bond. The acid density and surface roughness of the support (the surface periodicity of the support in the atomic scale) impact the morphology of the active phase, which, in turn, affects the reaction selectivity of DBT HDS.