Influence of precursor compounds on the structural and catalytic properties of CoNiMo/SBA-15 catalysts used in the hydrodesulfurization of dibenzothiophene

Abstract

In the present research project, it was studied in detail how the incorporation of different precursor compounds and the supplementary addition of amounts of nickel in the MoS2 slabs can influence the structural and catalytic properties of trimetallic CoNiMo catalysts supported on SBA-15 mesoporous support with precise control of the amount and nature of the promoters. The catalysts were prepared by the incipient impregnation method using ammonium heptamolybdate and cobalt and nickel acetate, and nitrate as precursors adding nickel in molar amounts (5, 10, and 20%) of the cobalt atomic loading. Adding the Ni in small amounts allows us to keep the (Co + Ni)/(Co+Ni+Mo) molar ratio near 0.3. The catalysts formed were labeled according to the precursor compounds used (CoNixMo-Ac for acetates and CoNixMo-N for nitrates), where x is the percentage of nickel. Catalysts were then characterized by N2 adsorption-desorption isotherms, X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. Catalysts were tested in the HDS of dibenzothiophene (DBT).Results show a significant impact of adding small amounts of nickel and the type of precursor compounds used for the CoNiMo trimetallic catalysts on the final HDS activity. In the case of the catalysts prepared with cobalt and nickel acetates, it was observed that the initial reaction rate values increased as the amount of Ni increased, being the CoNi5Mo-Ac, the catalyst with the lower catalytic activity. Increasing the amount of Ni causes an increase in the HDS of DBT. In the case of the catalysts prepared with nitrates, it could be observed a similar effect. The catalyst with the higher catalytic activity in both series was the CoNi20Mo-Ac. These results agree with the TEM analysis in which a decrease in the slab length of the MoS2 could be regarded as the de Ni amount increase. This means that the type of precursor used has an essential effect on the catalysts since modify their properties and catalytic activity and suggests that the materials synthesized with acetate precursors can help to improve the intrinsic activity of the HDS sites.