Kinetic and Mechanistic Analysis of Dibenzothiophene Hydrodesulfurization on Ti-SBA-15-NiMo Catalysts

MoS₂-based catalysts are the most commonly used systems for the hydrodesulfurization (HDS) process on an industrial scale. Different methods were employed to enhance the efficiency of the catalysts, which include changes in catalyst support and doping agents as well as tuning the dispersion of the MoS₂ phase using various synthetic techniques. In this work, we report the kinetic and mechanistic analysis of HDS of dibenzothiophene (DBT) for different NiMo-supported Ti-SBA-15 catalysts prepared by (1) direct single-pot (SP) synthesis and (2) impregnations of the NiMo phase into the Ti-SBA-15 support. Both methods were also repeated with and without the citric acid (CA) loading to achieve higher dispersion of the active metal sites. Kinetic modeling was performed to two "parallel-series" reactions of DBT, direct desulfurization (DDS) and hydrogenation (HYD), both leading to the final product of cyclohexylbenzene. Kinetic analysis reveals the considerable influence of the catalyst preparation methods to both steps of HDS of DBT. We found that apparent rate constants for DDS k₁ ^′ are highly dependent upon the employed synthetic method, while the effect of CA has a high contribution to the apparent rate constants for the conversion of partially hydrogenated dibenzothiophene intermediate, k₄ ^′.