Hydrocracking and rejuvenation of hydrocracking catalyst

Claim 1

IN A PROCESS OF HYDROCRACKING HYDROCARBON STOCKS AT ELEVATED TEMPERATURES AND PRESSURES WITH EXCESS HYDROGEN AND A CATALYST COMPRISING A NICKEL SULFIDE AS THE HYDROGENATION METAL COMPONENT ON A SILICEOUS CRACKING SUPPORT, WHEREIN SAID CATALYST ACCUMULATES CARBONACEOUS DEPOSITS AND MEASURABLY DEACTIVATES AFTER EXPOSURE IN EXCESS OF 1000 HOURS OF SAID HYDROCRACKING CONDITIONS, THE IMPROVEMENT WHICH COMPRISES DISCONTINUING THE FLOW OF HYDROCARBON STOCK OVER SAID DEACTIVATED CATALYST AND REJUVENATING SAID DEACTIVATED CATALYST BY OXIDIZING SAID CATALYST TO BURN OFF SAID CARBONACEOUS DEPOSITS AND CONVERT THE HYDROGENATING NICKEL COMPONENT TO NICKEL OXIDE, THEN CONTACTING SAID OXIDIZED CATALYST WITH HYDROGEN DILUTED WITH AN INERT GAS SUCH THAT THE PERFLUENT GAS MIXTURE CONTAINS 0.1 TO 1 MOL PERCENT OF HYDROGEN TO REDUCE SAID NICKEL OXIDE TO NICKEL, SAID REDUCTION BEING CARRIED OUT AT TEMPERATURES OF 450* TO 900*F. WITH THE FIRST PART OF SAID REDUCTION BEING IN THE LOWER PORTION OF SUCH TEMPERATURE RANGE, THE REDUCING GAS BEING FREE OF WATER AND PASSING OVER THE CATALYST AT A RATE OF AT LEAST 500 VOLUMES PER VOLUME OF CATALYST PER HOUR, THEN SULFIDING THE CATALYST, AND THEREAFTER HYDROCRACKING HYDROCARBON STOCKS WITH THE RESULTANT REJUVENATED CATALYST.