Catalytic Cracking of Heavy Aromatics and Polycyclic Aromatic Hydrocarbons over Fluidized Catalytic Cracking Catalysts

The distribution of products in the range of gasoline and middle distillate cuts obtained in the catalytic cracking of heavy aromatics and polycyclic aromatic hydrocarbons over a fluidized catalytic cracking (FCC) catalyst was studied. 1-Phenyloctane, biphenyl, fluorene, 9,10-dihydrophenanthrene, naphthalene, phenanthrene, pyrene, and benz[a]anthracene were used as model compounds of alkylaromatic, naphthenic-aromatic, and polyaromatic hydrocarbons, which are present in vacuum gas oil and residual feedstocks in the FCC process. The catalyst was used in its fresh and equilibrium forms at 450 degrees C in a Chemical Reactor Engineering Centre Riser Simulator reactor with reaction times from 2 to 6 s. Thermal cracking reactions overwhelm the catalytic conversion of naphthenic-aromatic compounds, such as fluorene and 9,10-dihydrophenanthrene. Under the same conditions, the fresh catalyst was more active than the equilibrium catalyst. The alkylaromatic, naphthenic-aromatic, and polyaromatic hydrocarbons, showed catalytic conversions that increased, were relatively stable, and decreased, respectively, as a function of the reaction time. The distribution of products suggested that the most important reactions were thermal dehydrogenation, hydrogen transfer, ring opening, cracking, and condensation. It was shown that all of the model compounds are cracked, yielding particularly benzene in the gasoline range and coke.