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 i nvestigated. The catalysts were prepared from ammonium tetrathiotungstate a nd fully sulfided. The kinetic data were obtained by varying the initial re actant partial pressure and the reaction temperature, and a Langmuir-Hinshe lwood kinetic model was used to fit the data. The hydrodenitrogenation of m ethylcyclohexylamine takes place via two mechanisms, ammonia elimination to methylcyclohexene, and nucleophilic substitution by SH followed by hydroge nolysis of the C-S bond of methylcyclohexyl mercaptan to methylcyclohexane; The first mechanism has a higher activation energy than the second. Additi on of nickel changes the nature of the site for the elimination; it increas es the activation energy of the reaction and the equilibrium adsorption con stant of the reactant on the active site, Fluorination does not change the intrinsic properties of the active sites, but it decreases the number of th e active sites. (C) 2001 Academic Press.