Regeneration of hydrocracking catalysts

Claim 1

A PROCESS OF HYDROCRACKING A HYDROCARBON FEEDSTOCK TO PRODUCE LOWER BOILING HYDROCARBONS, WHICH COMPRISES CONTCTING SAID FEEDSTOCK PLUS ADDED HYDROGEN AND UNDER HYDROCRACKING CONDITIONS WITH A HYDROCRACKING CATALYST COMPRISING A ZEOLITIC ALUMINO-SILICATE MOLECULAR SIEVE CRACKING BASE AND A GROUP VIII NOBLE METAL HYDROGENATING COMPONENT, SAID HYDROCRACKING CATALYST HAVING BEEN PREVIOUSLY UTILIZED FOR HYDROCRACKING A SULFUR-CONTAINING FEED TO A POINT OF SUBSTANTIAL DEACTIVATION WITH CONCOMITNT DEPOSITION OF DEACTIVATING CARBONACEOUS DEPOSITS AND AT LEAST ABOUT 0.1 PERCENT BY WEIGHT OF SULFUR THEREON, AND HAVING BEEN THEN REGENERATED BY: (1) SUBSTANTIALLY COMPLETELY STRIPPING VOLATILE HYDROCARBONS FROM SAID DEACTIVATED CATALYST; (2) SUBJECTING THE STRIPPED CATALYST TO REDUCTION BY CONTACTING WITH A STREAM OF GAS CONSISTING ESSENTIALLY OF HYDROGEN AT A TEMPERATURE BETWEEN ABOUT 650* AND 1,300*F. FOR A LENGTH OF TIME EXTENDING AT LEAST ABOUT FIVE HOURS BEYOND THE POINT AT WHICH THE SULFUR CONTENT OF THE CATALYST HAS BEEN REDUCED TO A SUBSTANTIALLY CONSTANT LEVEL; AND (3) SUBJECTING THE REDUCED CATALYST TO OXIDATION BY CONTACTING WITH AN OXYGEN-CONTAINING GAS AT ELEVATED TEMPERATURES TO BURN OFF SAID CARBONACEOUS MATERIALS.