Multi-stage hydrocracking process

Claim 1

AN INTEGRATED PROCESS FOR THE MANUFACTURE OF HIGHOCTANCE GASOLINE AND HIGH-QUALITY JET FUEL BY HYDROCRACKING WHICH COMPRISES: (1) SUBJECTING A GAS OIL FEEDSTOCK CONTAINING HYDROCARBON COMPONENTS BOILING ABOVE THE END-POINT OF THE DESIRED JET FUEL PRODUCT, AND ALSO CONTAINING ORGANIC SULFUR AND/OR NITROGEN COMPOUNDS, TO CATALYTIC HYDROFINING TO EFFECT DECOMPOSITION OF SAID SULFUR AND NITROGEN COMPOUNDS; (2) SUBJECTING EFFLUENT FROM SAID HYDROFINING, WITHOUT INTERVENING TREATMENT FOR THE REMOVAL OF AMMONIA AND HYDROGEN SULFIDE, TO A FIRST STAGE OF CATALYTIC HYDROCRACKING AT A TEMPERATURE BETWEEN ABOUT 500* AND 850*F. AND A PRESSURE BETWEEN ABOUT 400 AND 3,000 P.S.I.G., SAID TEMPERATURE BEIN ADJUSTED TO GIVE A 20-70% CONVERSION PER PASS TO 400*F. END-POINT PRODUCTS; (3) TREATING THE EFFLUENT FROM SAID FIRST-STAGE HYDROCRACKING TO SEPARATE OUT WATER-SOLUBLE SULFUR ANDNITROGEN COMPOUNDS; (4) FRACTIONATING THE HYDROCARBON PRODUCT FROM SAID FIRST-STAGE HYDROCRACKING TO RECOVER (A) A GASOLINE PRODUCT FRACTION HAVING AN END-BOILING-POINT ABOVE ABOUT 350*F., (B) A LIGHT GAS OIL FRACTION BOILING ABOVE SAID GASOLINE PRODUCT FRACTION AND HAVING AN END-BOILINGPOINT BETWEEN ABOUT 500* AND 550*F., AND (C) A HEAVY GAS OIL BOILING ABOVE THE END-BOILING-POINT OF SAID LIGHT GAS OIL FRACTION AND ABOVE THE END-BOILING-POINT OF THE DESIRED JET FUEL PRODUCT; (5) RECYCLING SAID LIGHT GAS OIL TO SAID FIRST HYDROCRACKING STAGE; (6) SUBJECTING SAID HEAVY GAS OIL TO A SECOND STAGE OF CATALYTIC HYDROCRACKING IN THE PRESENCE OF A GROUP VIII METAL-MOLECULAR SIEVE ZEOLITE TYPE HYDROCRACKING CATALYST, AND AT A TEMPERATURE WHICH IS (A) BETWEEN ABOUT 400* AND 750*F., AND (B) LOWER THAN THE TEMPERATURE EMPLOYED IN SAID FIRST-STAGE HYDROCRACKING, AND AT A SPACE VELOCITY ADJUSTED TO GIVE ABOUT 40 TO 80% CONVERSION TO JET FUEL AND LIGHTER PRODUCTS PER PASS; (7) FRACTIONATING THE EFFLUENT FROMSAID SECOND-STAGE HYDROCRACKING TO RECOVER A LIGHT GASOLINE FRACTION, A JET FUEL PRODUCT FRACTION HAVING AN INITIAL BOILING POINT BETWEEN ABOUT 600* AND 400*F., AN END-BOILING POINT BETWEEN ABOUT 50* AND 550*F., AND HAVING A FREEZING POINT BELOW ABOUT -60*F. WHICH IS WITHDRAWN FROM THE PROCESS, AND A HEAVY BOTTOMS FRACTION; AND (8) RECYCLING AT LEAST A PORTION OF SAID HEAVY BOTTOMS FRACTION TO SAID SECOND HYDROCRACKING STAGE.