This invention relates to a process for cracking hydrocarbon oils. The process comprises contacting a hydrocarbon oil with a catalyst that has been contacted with an atmosphere containing a reducing gas, separating cracked products and the catalyst, and regenerating the catalyst. The catalyst is a cracking catalyst containing a metal component, or a catalyst mixture of a cracking catalyst containing a metal component and a cracking catalyst free of metal component. The catalyst is contacted with the atmosphere containing a reducing gas at a temperature of 100 to 900.degree. C. for at least 1 second, and the amount of the atmosphere containing a reducing gas is not less than 0.03 cubic meters of reducing gas per ton of the cracking catalyst containing a metal component per minute, at a pressure of 0.1-0.5 MPa in the reduction reactor. The process has enhanced capability for desulfurizing and cracking heavy oils.

A novel process for cracking olefins including contacting a hydrocarbon oil with a catalyst in a riser reactor having multiple reaction zones under cracking reaction conditions; separating reaction products and the catalyst; regenerating at least a part of spent catalyst obtained, contacting a part of the regenerated catalyst with the hydrocarbon in the first reaction zone; contacting the other part of the spent catalyst and/or regenerated catalyst in at least one reaction zone after the first reaction zone with the products obtained in previous reaction zones.

The present invention discloses a high stability rare earth zeolite Y with high rare earth and the preparation process thereof, which zeolite has a content of rare earth of 4 15 wt %, a unit cell constant of 2.450 2.458 nm, a differential thermal collapsed temperature of 1000 1056.degree. C., a silica to alumina ratio of 8.3 8.8, and a content of sodium oxide less than 1.0 wt %. Said zeolite is prepared by drying a rare earth-containing zeolite Y, introducing gaseous silicon tetrachloride carried by dry air and reacting at a temperature of 150 600.degree. C. for 10 min to 6 h, then purging with dry air and washing with de-cationized water to remove the soluble by-products. The rare earth zeolite Y possesses high activity and selectivity for cracking the heavy oils, high activity for hydrogen transfer, has good coke selectivity, can effectively increase the yield of light oils, and improve the quality of gasoline and thus can directly serve as an active component for preparing various hydrocarbon cracking catalysts.

The present invention relates to a cracking catalyst comprising layered clays and a process for cracking hydrocarbon oils using said catalyst. Said catalyst is prepared by the process comprising the following steps: mixing and slurrying an expandable clay, a modifier component, pseudo-boehmite and water for 0.1-10 h to obtain a slurry, aging the slurry at 50-85.degree. C. for 0.1-10 h, then drying and forming the slurry to obtain a formed material, water washing and aging the solid, and finally drying and calcining the solid, and said modifier being one or more selected from the group consisting of hydroxyl polymers of silicon, aluminum, zirconium or titanium, and substances comprising one or more of said hydroxyl polymers. Said process for cracking hydrocarbon oils comprises contacting a hydrocarbon oil with a catalyst under the cracking conditions, said catalyst being the aforesaid cracking catalyst comprising layered clays or a mixture of at least 1% by weight of said cracking catalyst comprising layered clays and a prior cracking catalyst. The catalyst according to the present invention has an improved ability to convert heavy oils. The process according to the present invention for cracking hydrocarbon oils has higher conversion of hydrocarbon oils and higher yield of light oils.

The present invention discloses a high stability rare earth zeolite Y with high rare earth and the preparation process thereof, which zeolite has a content of rare earth of 4-15 wt %, a unit cell constant of 2.450-2.458 nm, a differential thermal collapsed temperature of 1000-1056.degree. C., a silica to alumina ratio of 8.3-8.8, and a content of sodium oxide less than 1.0 wt %. Said zeolite is prepared by drying a rare earth-containing zeolite Y, introducing gaseous silicon tetrachloride carried by dry air and reacting at a temperature of 150-600.degree. C. for 10 min to 6 h, then purging with dry air and washing with de-cationized water to remove the soluble by-products. The rare earth zeolite Y possesses high activity and selectivity for cracking the heavy oils, high activity for hydrogen transfer, has good coke selectivity, can effectively increase the yield of light oils, and improve the quality of gasoline and thus can directly serve as an active component for preparing various hydrocarbon cracking catalysts.