THE EFFECT OF AN ACIDIC CATALYST ON SIMULTANEOUS HYDRODENITROGENATION AND HYDRODESULFURIZATION OF MODEL COMPOUNDS

The hydrodesulfurization (HDS) of thiophene and the hydrodenitrogenation (HDN) of pyridine over acidic catalysts was studied in this research. Four catalysts were considered; CoMo-SiO(,2)/Al(,2)O(,3), CoMo-Al(,2)O(,3), NiW-SiO(,2)/Al(,2)O(,3), and NiW-Al(,2)O(,3). These catalysts were chosen so that the effect of the metallic complex (CoMo or NiW) and the effect of the acidic support (SiO(,2)/Al(,2)O(,3) or Al(,2)O(,3)) could be isolated. Reaction conditions of 200 to 400(DEGREES)C and 40 to 200 psia were used.; A two-site reaction mechanism (sites I and II), based on the Langmuir adsorption isotherm, was used to model the reaction of thiophene. A single site (site I) analysis described the reaction of pyridine. Values of the reaction rate constants (k), and the adsorption equilibrium constants (K) were calculated from the data collected for pure thiophene, pure pyridine, and for a 50/50 solution of each. The results showed that both thiophene and pyridine adsorb significantly on the type I sites, but not on the type II sites. No consistent metal effect (NiW or CoMo) was observed. However, alumina was the more effective catalyst substrate for the reaction of both thiophene and pyridine for 50/50 feeds. Alumina was also more effective for pure thiophene reaction, but silica-alumina was more effective for pyridine reaction from a pure feed.