CATALYTIC-HYDROGENATION AND HYDROCRACKING OF FLUORENE - REACTION PATHWAYS, KINETICS, AND MECHANISMS

Catalytic hydrogenation and hydrocracking reaction pathways were determined for fluorene at 335-380-degrees-C and 153-atm total pressure. A presulfided NiW/Al2O3 catalyst was active for isomerization and hydrogenation, and reaction of fluorene gave 1,2,3,4,4a,9a-hexahydrofluorene and ultimately perhydrofluorene. The much more acidic (presulfided) NiMo/zeolite Y catalyst was active for hydrogenation and isomerization and also for hydrocracking through the central five-carbon-membered ring, which gave equimolar yields of saturated and aromatic single-ring products. The fluorene disappearance rate constants k [(cm3 of solution/(g of catalyst s)] were 0.13 and 0.41 at 380-degrees-C for reaction catalyzed by NiW/Al2O3 and by NiMo/zeolite, respectively. Arrhenius parameters were [log A [(cm3 of solution/(g of catalyst s)], E(act) (kcal/mol)] = [5.7, 19.8] and [9.7, 30.3], respectively. Hydrocracking of the five-carbon-membered-ring-containing (5-CMRC) fluorene occurred via cleavage pathways distinct from those for 6-CMRC fused-ring polynuclear aromatic compounds. The major fluorene hydrocracking pathway, giving 2 mol of single-ring products, leads to less hydrogen consumption than the hydrocracking of a comparable 6-CMRC compound such as phenanthrene, which gives only 1 mol of single-ring products and lower value light-gas products. These results provide guidelines for modeling the hydrocracking of feeds containing polynuclear aromatic hydrocarbons.