Increased yields and catalyst life in catalytic hydrocracking

Claim 1

A PROCESS FOR HYDROCRACKING A HYDROCARBON FRACTION HAVING AN INITIAL BOILING POINT OF AT LEAST ABOUT 400*F. AND A SULFUR CONENT OF LESS THAN 4 PERCENT BY EIGHT TO PRODUCE LOWER BOILING PRODUCTS WHICH COMPRISES CONTACTING SAID HYDROCARBON FRACTION IN THE PRESENCE OF HYDROGEN FOR AN EXTENDED PERIOD OF TIME WITH AN INITIALLY UJNAGED CATALYST COMPRISING BETWEEN ABOUT 0.05 PERCENT AND 10 PERCENT, BY WEIGHT OF THE CATALYST, OF AT LEAST ONE NOBLE METAL OF THE PLATINUM AND PALLADIUM SERIES DEPOSITED UPON A SYNTHETIC COMPOSITE OF REFRACTORY OXIDES OF AT LEAST TWO ELEMENTS OF GROUPS IIA, IIIB AND IV OF THE PERIODIC ARRANGEMENT OF ELEMENTS HAVING AN ACTIVITY INDEX OF AT LEAST 25 UNDER HYDROCRACKING RREACTION CONDITIONS TO CONVERT SAID HYDROCARBON FRACTION TO LOWER BOILING PRODUCTS WITH A NET CONSUMPTION OF HYDROGEN; ADDING SUBSTANTIAL QUANTITIES OF SULFUR COMPOUNDS TO SAID HYDROCARBON FRACTION TO OBTAIN A SULFUR CONTENT IN THE RANGE FROM ABOUT 0.5 TO ABOUT 5 WEIGHT PERCENT OF SAID HYDROCARBON FRACTION DURING A PERIOD OF TIME WHICH EXTENDS FROM THE INITIAL CONTACTING OF THE HYDROCARBON FRACTION WITH THE CATALYST TO A TME WITHIN THE RANGE FROM ABOUT 0.5 HOUR TO ABOUT 14 DAYS AFTER SAID INITIAL CONTACTING; DISCONTINUING SAID ADDITION OF SULFUR COMPOUNDS AFTER SAID PERIOD OF TIME HAS EXPIRED; AND CONTINUING THE CONVERSION OF SAID HYDROCARBON FRACTION WITHOUT ADDED SULFUR COMPOUNDS UNTIL SUCH TIME AS THE CATALYST BECOMES SUFFICENTLY AGED S TO REQUIRE REGENERATION.