Al-modified yolk-shell silica particle-supported NiMo catalysts for ultradeep hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene: Efficient accessibility of active sites and suitable acidity

Yolk-shell SiO2 particles（YP） with center-radial meso-channels were fabricated through a simple and effective method. Al-containing YP-supported NiMo catalysts with different Al amounts（NiMo/AYP-x,x = Si/Al molar proportion） were prepared and dibenzothiophene（DBT） and 4,6-dimethyl-dibenzothiophene（4,6-DMDBT） were employed as the probes to evaluate the hydrodesulfurization（HDS） catalytic performance. The as-prepared AYP-x carriers and corresponding catalysts were characterized by some advanced characterizations to obtain deeper correlations between physicochemical properties and the HDS performance. The average pore sizes of series AYP-x supports are above 6.0 nm, which favors the mass transfer of organic sulfides. The cavity between the yolk and the shell is beneficial for the enrichment of S-containing compounds and the accessibility between reactants and active metals.Aluminum embedded into the silica framework could facilitate the formation of Lewis（L） and Br?nsted（B） acid sites and adjust the metal-support interaction（MSI）. Among all the as-synthesized catalysts,NiMo/AYP-20 catalyst shows the highest HDS activities. The improved HDS activity of NiMo/AYP-20catalyst is attributed to the perfect combination of excellent structural properties of the yolk-shell mesoporous silica, enhanced acidity, moderate MSI, and good accessibility/dispersion of active components.