Multi-stage hydrocracking process

Claim 1

A PROCESS FOR HYDROCRACKING A MINERAL OIL FEEDSTOCK BOILING OVER A SUBSTANTIAL TEMPERATURE RANGE AND CONTAINING A NON-HYDROCARBON IMPURITY SELECTED FROM THE CLASS CONSISTING OF ORGANIC NITROGEN COMPOUNDS AND ORGANIC SULFUR COMPOUNDS, WHICH COMPRISES: (1) SUBJECTING SAID FEEDSTOCK PLUS ADDED HYDROGEN TO CATALYTIC HYDROFINING UNDER CONDITIONS OF PRESSURE, TEMPERATURE AND FLUID DISTRIBUTION SUCH THAT A SUBSTANTIAL LIQUID PHASE IS PRESENT IN AT LEAST A PORTION OF THE HYDROFINING ZONE, AND A SUBSTANTIAL VAPOR PHASE IS PRESENT IN AT LEAST A PORTION OF THE HYDROFINING ZONE; (2) STRIPPING SAID LIQUID PHASE WITH HYDROGEN AFTER SUBSTANTIAL HYDROFINING HAS TAKEN PLACE AND AT SUBSTANTIALLY HYDROFINING PRESSURE TO PRODUCE A STRIPPED LIQUID-PHASE HYDROFINER EFFLUENT RELATIVELY LEAN IN SAID IMPURITIES AND A VAPOR-PHASE STRIPPING EFFLUENT CONTAINING RELATIVELY LIGHT HYDROCARBONS AND RELATIVELY RICH IN VOLATILE DECOMPOSITION PRODUCTS OF SAID IMPURITY; (3) SUBJECTING VAPOR-PHASE HYDROFINER EFFLUENT FROM STEP (1), WITHOUT INTERVENING PURIFICATION OR DEPRESSURING TO BELOW THE DESIRED HYDROCRACKING PRESSURE, TO CATALYTIC HYDROCRACKING IN A FIRST HYDROCRACKING ZONE IN THE ABSENCE OF SAID STRIPPED LIQUID PHASE AT A RELATIVELY HIGH TEMPERATURE; (4) SUBJECTING SAID STRIPPED LIQUID-PHASE HYDROFINER EFFLUENT, WITHOUT FURTHER PURIFICATION, TO CATALYTIC HYDROCRACKING IN A SECOND HYDROCRACKING ZONE AT A RELATIVELY LOW TEMPERATURE; AND (5) RECOVERING DESIRED LOW-BOILING HYDROCARBONS FROM EACH OF SAID HYDROCRACKING ZONES.