Multicatalyst hydroconversion

Claim 1

A PROCESS FOR THE HYDROCRACKING OF HYDROCARBON FRACTIONS BOILING ABOVE 400*F. WHICH CONTAIN 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 A BED OF HYDROCRACKING CATALYST WITHIN AN ENCLOSED HOUSING, MAINTAINING AN OUTLET REGION OF SAID BED WHICH EXTENDS FROM THE END THEREOF FROM WHICH PRODUCTS ARE REMOVED FOR A DISTANCE AMOUNTING TO AT LEAST TWO-THIRDS OF THE TOTAL LENGTH OF THE BED CONTAINING A STANDARD HYDROCRACKING CATALYST, MAINTAINING A MIDDLE REGION OF SAID BED WHICH NEXT PRECEDES SAID OUTLET REGION WITH A CATALYST HAVING A HIGHER RATIO OF HYDROGENATION ACTIVITY TO CRACKING ACTIVITY THAN THE CATALYST IN SAID OUTLET REGION, MAINTAINING AN INLET REGION OF SAID BED EXTENDING FROM THE END OF THE BED TO WHICH THE HYDROCARBON FRACTION IS SUPPLIED TO SAID MIDDLE ZONE FILLED WITH A CATALYST HAVING A LOWER RATIO OF HYDROGENATION ACTIVITY TO CRACKING ACTIVITY THAN THE CATALYST IN SAID MIDDLE ZONE, MAINTAINING SAID BED AT A PRESSURE WITHIN THE RANGE 500 TO 10,000 POUNDS PER SQUARE INCH GAUGE, SUPPLYING THE HYDROCARBON FRACTION AND HYDROGEN TO THE INLET END OF SAID BED AT A TEMPERATURE WITHIN THE RANGE 700*F. TO 1000*F. AND PASSING SAID PETROLEUM FRACTION AND HYDROGEN THROUGH THE BED TO EFFECT A CONVERSION, AT LEAST IN PART, TO LOWER BOILING PRODUCTS AND PRODUCE EXOTHERMIC HEAT OF REACTION THROUGHOUT SAID BED, REMOVING SAID PRODUCTS FROM SAID BED AND SEPARATING THE DESIRED LOWER BOILING PRODUCTS FROM HIGHER BOILING RECYCLE MATERIAL, RETURNING SAID HIGHER BOILING RECYCLE MATGERIAL, RETURNING INJECTING SAID MATERIAL INTO SAID BED AT THE INLET TO SAID MIDDLE REGION AT A TEMPERATURE AND IN A QUANTITY THAT THE EFFLUENT FROM THE FIRST REGION OF THE BED THEREABOVE IS COOLED TO A TEMPERATURE BELOW ABOUT 790*F., AND PASSING SAID RECYCLE MATERIAL THROUGH THE MIDDLE AND OUTLET REGIONS OF THE BED, WHEREBY UNIFORM DEPOSITION OF CARBONACEOUS CONTAMINANTS ON ALL OF THE CATALYST IN SAID BED IN PROMOTED.