Multiple pass catalytic cracking

Claim 1

A PROCESS FOR HYDROCRACKING HYDROCARBON FRACTIONS IN A MANNER WHICH PRODUCES LOWER DRY GAS YIELD, LOWER C5+ LIGHT NAPHTHA YIELD, HIGHER HEAVY NAPHTHA YIELD AND A FUEL OIL WITH A HIGHER DIESEL INDEX AS COMPARED TO ONCE-THROUGH OPERATIONS, WHICH COMPRISES: CONTACTING IN A FIRST REACTION ZONE, A HYDROCARBON FRACTION HAVING AN INITIAL BOILING POINT OF AT LEAST ABOUT 400*F., A 50 PERCENT POINT OF AT LEAST 500*F. AND AN END BOILING POINT OF AT LEAST ABOUT 600*F., WITH A CATALYST COMPRISING BETWEEN ABOUT 0.05 PERCENT AND ABOUT 20 PERCENT, BY WEIGHT OF THE CATALYST, OF AT LEAST ONE METAL OF THE PLATINUM AND PALLADIUM SERIES DEPOSITED UPON A SYNTHETIC COMPOSITE OF OXIDES OF AT LEAST TWO METALS OF GROUPS IIA, IIIB AND IV OF THE PERIODIC ARRANGEMENT OF THE ELEMENTS HAVING AN ACTIVITY INDEX OF AT LEAST 25 IN THE PRESENCE OF HYDROGEN AND UNDER HYDROCRACKING CONDITIONS WHICH EFFECT A PORTION OF THE DESIRED ULTIMATE CONVERSION OF SAID HYDROCARBON FRACTION INTO PRODUCTS BOILING BELOW 390*F. WITH A NET CONSUMPTION OF HYDROGEN BY SAID FRACTION, CONTACTING AT LEAST THE PORTION OF THE EFFLUENT OF SAID FIRST REACTION ZONE WHICH BOILS ABOVE 390*F. WITH A CATALYST OF THE SAME TYPE USED IN THE FIRST REACTION ZONE IN A SECOND REACTION ZONE UNDER HYDROCRACKING CONDITIONS MILDER THAN THOSE OF THE FIRST REACTION ZONE, WHICH CONDITIONS INCLUDE A TEMPERATURE SUBSTANTIALLY BELOW THE TEMPERATURE USED IN THE FIRST REACTION ZONE, TO EFFECT THE REMAINDER OF THE DESIRED CONVERSION TO PRODUCTS BOILING BELOW 390*F. WITH A NET CONSUMPTION OF HYDROGEN IN SAID SECOND REACTION ZONE AND THE REACTION CONDITIONS IN BOTH OF SAID ZONES INCLUDING TEMPERATURES WITHIN THE RANGE ABOUT 400 TO ABOUT 825*F., HYDROGEN PRESSURES WITHIN THE RANGE ABOUT 100 TO 2500 POUNDS PER SQUARE INCH GAUGE, A MOLAR RATIO OF HYDROGEN TO HYDROCARBON CHARGE WITHIN THE RANGE ABOUT 2 TO ABOUT 80 AND A LIQUID HOURLY SPACE VELOCITY WITHIN THE RANGE ABOUT 0.1 TO ABOUT 10.