HYDROCRACKING OF POLYNUCLEAR AROMATIC-HYDROCARBONS - DEVELOPMENT OF RATE LAWS THROUGH INHIBITION STUDIES

The relationship between molecular structure and reactivity during hyd rocracking of model polynuclear aromatic hydrocarbons was examined thr ough detailed kinetic studies. Naphthalene and phenanthrene were react ed over a presulfided NiW/USY zeolite catalyst in an 1-L batch autocla ve at P-H2 = 68.1 atm and T = 350 degrees C, in a cyclohexane solvent. Pure-component experiments were combined with experiments where hydro carbons and ammonia were added as inhibitors to aid quantitative netwo rk analysis. In all, 21 rate, 18 equilibrium, and 36 adsorption parame ters were estimated through fitting of the kinetics data to a dual-sit e Langmuir-Hinshelwood-Hougen-Watson rate law. Adsorption parameters o n both metal and acid sites increased with the number of aromatic ring s and the number of saturated carbons; however, the quantitative value s were higher for the acid sites. Rate parameters showed that, for a g iven total number of aromatic rings, hydrogenations at terminal aromat ic rings were favored over hydrogenations at internal rings. Isomeriza tions and ring openings were favored at positions a to an aromatic rin g or a tertiary carbon. Equilibrium concentration ratios for all hydro genation and ring-opening reactions were larger than unity; equilibriu m ratios for all isomerizations were less than unity, indicating signi ficant reverse reactions. The hydrocracking networks were organized in to the reaction families of hydrogenation, isomerization, ring opening , and dealkylation. The reactivity trends within each reaction family may be used for the development of quantitative structure/reactivity r elationships.