Patent ID: 7347930

Claim:
A process for cracking hydrocarbon oils, comprising contacting a hydrocarbon oil with a catalyst in a riser reactor having at least 3 reaction zones under cracking reaction conditions, separating reaction products and the catalyst to obtain a spent catalyst, regenerating at least a part of the spent catalyst, wherein said catalyst is a cracking catalyst containing metal component or a catalyst mixture of the cracking catalyst containing metal component and a cracking catalyst free of metal component, wherein said metal component is present in maximum valence state or reduction valence state; based on said cracking catalyst containing metal component and calculated by oxide of the metal component in the maximum oxidation state, the content of metal component is 0.1-30 wt %; said metal component is one or more metals selected from the group consisting of non-aluminum metals of Group III A, metals of Group IVA, Group VA, Group IB, Group IIB, Group VB, Group VIB and Group VIIB, non-noble metals of Group VIII, and rare-earth metals in the Periodic Table of Elements; contacting a part of the spent catalyst and/or the regenerated catalyst with the hydrocarbon oil in the first reaction zone; contacting and reacting the other part of the spent catalyst and/or the regenerated catalyst in at least one of reaction zones after the first reaction zone with the products obtained in previous reaction zone; said process comprising further a step which comprises contacting the spent catalyst and/or the regenerated catalyst, or the mixture of the spent catalyst and/or the regenerated catalyst with a fresh catalyst with an atmosphere containing a reducing gas, prior to contacting and reacting with hydrocarbon oil or products obtained in previous reaction zones in at least a reaction zone; wherein the catalyst contacts with the atmosphere containing a reducing gas at a temperature of 100-900° C., at a pressure 0.1-0.5 MPa for at least 1 second and the amount of the atmosphere containing a reducing gas is no less than 0.03 cubic meters of the reducing gas per ton of the cracking catalyst containing metal component per minute, wherein cracking reaction conditions in the first reaction zone include a reaction temperature of 450-650° C., a reaction pressure of 0.1-0.5 MPa, a contact time of 0.4-6 seconds and a catalyst/oil weight ratio of 1-30; cracking reaction conditions in the second reaction zone include a reaction temperature of 470-650° C., a reaction pressure of 0.1-0.5 MPa, a contact time of 1-15 seconds and a catalyst/oil weight ratio of from above 1-3 times of that in the first reaction zone; cracking reaction conditions in the third reaction zone and subsequent reaction zones include a reaction temperature of 450-550° C., a reaction pressure of 0.1-0.5 MPa, a contact time of 1-4 seconds, and a catalyst/oil weight ratio of from above 1-3 times of that in the first reaction zone; the operating conditions in the outlet zone of the riser reactor include a temperature of 460-590° C. and a contact time of 0.1-1 second.