Hydrocracking of hydrocarbons

Claim 1

A PROCESS FOR THE CATALYTIC HYDROCRACKING OF A HIGH BOILING LIQUID HYDROCARBON CHARGE CONTAINING AT LEAST ONE OF THE FOLLOWING COMPONENTS IN AT LEAST THE QUANTITY INDICATED: NITROGEN 0.05 PERCENT BY WEIGHT, SULFUR 0.2 PERCENT BY WEIGHT, OXYGEN 0.1 PERCENT BY WEIGHT, UNSATURATES 20 PERCENT BY VOLUME, WHICH COMPRISES: MAINTAINING THREE SEPARATE HYDROCRACKING ZONES, EACH FILLED WITH A CATALYST AND ARRANGED IN SERIES, THE CATALYST IN THE LAST ZONE IN THE SERIES BEING GREATER IN VOLUME THAN THE TOTAL VOLUME OF CATALYST IN THE OTHER TWO ZONES AND HAVING BOTH HYDROGENATION AND CRACKING ACTIVITY, THE CATALYST IN THE SECOND OF SAID ZONES HAVING A GREATER RATIO OF HYDROGENATION ACTIVITY TO CRACKING ACTIVITY THAN THE RATIO OF SAID ACTIVITIES OF THE CATALYST IN THE LAST OF SAID ZONES AND THE CATALYST IN THE FIRST OF SAID ZONES HAVING A RATIO OF HYDROGENATION ACTIVITY TO CRACKING ACTIVITY LESS THAN THE RATIO OF SAID ACTIVITIES IN THE SECOND OF SAID ZONES;PASSING THE HYDROCARBON CHARGE THROUGH SAID ZONES IN SUCCESSION UNDER HYDROCRACING REACTION CONDITIONS WHICH INCLUDE A REACTION TEMPERATURE IN EACH ZONE ABOVE 700*F., WHEREBY UNIFORM DEPOSITION OF CARBONACEOUS CONTAMINANT ON ALL OF THE CATALYST IS PROMOTED.