Kinetic Investigation of the Effect of Nickel and Fluorine on the HDN of Methylcyclohexylamine over WS2/Al2O3 Catalysts

The effects of incorporation of nickel and fluorine in WS2/Al2O3 catalysts on the kinetics of the hydrodenitrogenation of methylcyclohexylamine were investigated. The catalysts were prepared from ammonium tetrathiotungstate and fully sulfided. The kinetic data were obtained by varying the initial reactant partial pressure and the reaction temperature, and a Langmuir-Hinshelwood kinetic model was used to fit the data. The hydrodenitrogenation of methylcyclohexylamine takes place via two mechanisms, ammonia elimination to methylcyclohexene, and nucleophilic substitution by SH followed by hydrogenolysis of the C–S bond of methylcyclohexyl mercaptan to methylcyclohexane. The first mechanism has a higher activation energy than the second. Addition of nickel changes the nature of the site for the elimination; it increases the activation energy of the reaction and the equilibrium adsorption constant of the reactant on the active site. Fluorination does not change the intrinsic properties of the active sites, but it decreases the number of the active sites.