Influence of support and supported phases on catalytic functionalities of hydrotreating catalysts

• Mixed oxide supports of Al2O3–zeolite, Al2O3–SiO2, and Al2O3–TiO2 were prepared.
• The HDS activity in DBT conversion was in the order: NiMo ⩾ NiW > CoMo on alumina.
• Al2O3–zeolite support was the most active in HDS of DBT.
• The most active catalyst in HDS of DBT was NiMo supported on Al2O3–zeolite.

Different mixed-oxide supports were synthesized using homogeneous co-precipitation methods. Alumina–silica, alumina–titania, and alumina–zeolite supports were prepared and then impregnated with Mo (or W) and Co (or Ni) in order to evaluate their behavior in the dibenzothiophene hydrodesulfurization. Supports and supported catalysts were characterized by atomic absorption and textural properties. The conversion of model compounds (tetralin, 1-methylnaphthalene, and decalin) was investigated with the aim of understanding ring opening reaction over the support in presence of hydrogen. The model test reactions for support as well supported sulfide catalysts were carried out in a batch reactor at 4 MPa and 340 °C. Conversion of cyclo-compounds showed that decalin had the highest conversion followed by 1-methylnaphthalene and tetralin when using a silica–alumina supported catalyst. The hydrodesulfurization results as a function of support variation indicated that high acidity of support has positive effect on the hydrogenolysis of CS bond breaking. Thus, it is inferred that a balance between metal sites of hydrogenation and cracking of the support is critical in order to synthesize a bifunctional catalyst for deep hydrodesulfurization where sulfur removal as well as cetane improvement are mandatory.