The FCC process was originally developed to convert vacuum gasoil (VGO)range hydrocarbons to high octane gasoline.Highly active acid catalysis provided by the conventional FCC Y zeolite catalyst is very successful in fulfilling this purpose.Large molecules boiling above 340oC are cracked to smaller molecules,initially forming olefins,which may continue to react and cyclize forming naphtenes,hydrogen transfer from naphtenic hydrocarbons,also promoted by the Y zeolite,produce aromatics halting further reactions [1].This reaction scheme is very convenient,as many of the C7 to C10 aromatics preferentially formed in the FCC are in the gasoline range and are also desirable for their high octane.
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