Process for cracking a residual oil containing metallic impurities

Claim 1

A PROCESS FOR TREATING A RESIDUAL HYDROCARBON OIL BOILING ABOVE THE GASOLINE RANGE AND CONTAINING MORE THAN ABOUT 25 TO ABOUT 50 P.P.M. NICKEL AND MORE THAN ABOUT 50 TO ABOUT 1000 P.P.M. VANADIUM WHICH COMPRISES TREATING SAID HYDROCARBON OIL AT AN ELEVATED TEMPERATURE UNDER VISBREAKING CONDITIONS, FRACTIONATING THE RESULTING VISBROKEN OIL TO YIELD TO GAS OIL FRACTION CONTAINING AT LEAST ABOUT 0.8 TO LESS THAN 25 P.P.M. NICKEL AND AT LEAST ABOUT 1.5 TO LESS THAN ABOUT 50 P.P.M. VANADIUM, SAID GAS OIL FRACTION HAVING ABOUT 40 TO 85% OF ITS VOLUME BOILING PRIMARILY IN THE RANGE OF ABOUT 900*F. TO 1200* F., SUBJECTING SAID GAS OIL FRACTION TO CATALYTIC CRACKING, SAID GAS OIL BEING PRESENT IN THE CRACKING FEEDSTOCK IN AN AMOUNT TO SUPPLY AT LEAST ABOUT 1 P.P.M NICKEL AND AT LEAST ABOUT 1 P.P.M. VANADIUM AND SAID FEEDSTOCK CONTAINING LESS THAN ABOUT 10 P.P.M. NICKEL AND LESS THAN ABOUT 20 P.P.M. VANADIUM, REGENERATING THE CATALYST, REMOVING A PORTION OF METAL CONTAMINATED CATALYST FROM THE CRACKING SYSTEM, THE REMOVED CATALYST CONTAINING MORE THAN ABOUT 200 P.P.M. NICKEL AND MORE THAN ABOUT 500 P.P.M. VANADIUM, DEMETALLIZING SAID METAL CONTAMINATED CATALYST TO REMOVE AT LEAST 50% OF THE NICKEL AND AT LEAST 15% OF THE VANADIUM FROM THE CATALYST, AND RETURING RESULTING DEMETALLIZED CATALYST TO SAID CRACKING SYSTEM AND RECOVERING GASOLINE FROM SAID CATALYTIC CRACKING, SAID METAL CONTENTS BEING CALCULATED AS THE METAL OXIDES.