Pressure cascaded two-stage hydrocracking unit

An apparatus for catalytically cracking of an oil feedstock, the apparatus comprising:

• a first reactor for hydrocracking the oil feedstock, wherein the oil feedstock is contacted over a hydrotreating catalyst to produce a mixed effluent stream;
• a fractionator for fractionating the mixed effluent stream into a first, second and third product streams,
• wherein the first product stream comprises C1-C4, naphtha, and diesel boiling in the range of 36-370° C., the second product stream comprises hydrocarbon components having an initial nominal boiling point of 370° C. and a final boiling point ranging from 420-480° C., and the third product stream fraction comprises heavy polynuclear aromatic (HPNA) hydrocarbons and other hydrocarbon components boiling above the second product final boiling point;
• a second reactor for hydrocracking the second product stream;
• and
• a third reactor for hydrocracking the third product stream (23),
• wherein the third reactor operates at a higher pressure than the second reactor and contains larger pore hydrogenation/hydrocracking catalysts.

An apparatus for catalytically cracking an oil feedstock comprising:

• a first hydroprocessing reactor including an inlet and an outlet and containing catalysts having hydrotreating and hydrocracking functions;
• a fractionator having an inlet in fluid communication with the outlet of the first reactor, the fractionator including an overhead outlet, a middle outlet and a bottom outlet;
• a second hydroprocessing reactor including an inlet in fluid communication with the middle outlet of the fractionator and an outlet in fluid communication with the inlet of the fractionator and/or the inlet of the first hydroprocessing reactor, the second hydroprocessing reactor containing catalysts having a first average pore size;
• and
• a third hydroprocessing reactor including an inlet in fluid communication with the bottom outlet of the fractionator and an outlet in fluid communication with the inlet of the fractionator and/or the inlet of the first hydroprocessing reactor, the third hydroprocessing reactor containing catalysts having a second average pore size, the second average pore size being larger than the first average pore size.