Kinetics of simultaneous hydrodesulfurization and hydrodenitrogenation reactions using CoMoP/Al₂O₃ and NiMoP/Al₂O₃

Hydrodesulfurization (HDS) is a key reaction to achieve diesel production at the specified low sulfur levels and is highly affected by a competing reaction involving nitrogen removal through hydrodenitrogenation (HDN). This work evaluated kinetic parameters of simultaneous reactions of HDS of dibenzothiophene (DBT) and HDN of quinoline (Q) using CoMoP/Al₂O₃ and NiMoP/Al₂O₃ catalysts under operational conditions that allow a wide range of reagent conversions. Estimated parameters were evaluated using rigorous statistical analysis. Good fits for the evaluated experimental data were provided by both power-law and Langmuir-Hinshelwood models. Turnover frequency values highlight adsorption and competition effects between nitrogen-containing compounds and sulfur-containing compounds. NiMoP catalyst showed higher hydrogenating power than CoMoP, with larger absolute value of the estimated adsorption enthalpy (−120 kJ.mol⁻¹ for NiMoP and −75 kJ.mol⁻¹ for CoMoP), suggesting strong adsorption of nitrogen compounds. A catalyst with more hydrogenating power is also more capable of performing both HDN and HDS reactions simultaneously.