Claims
- 1. A multi-stage process for the catalytic cracking of hydrocarbons to lighter products comprising:
- shape selectively cracking a hydrocarbon chargestock which is completely vaporizable in a first reactor, a shape selective cracking reactor operating at atmospheric to 100 psig and containing an inventory of shape selective catalyst having a constraint Index of 1-12, at shape selective cracking conditions including a temperature sufficient to convert less than 50 volume % of the feed to lower boiling components and produce selectively cracked products including iso-olefins and normally liquid products;
- separating said shape selectively cracked products into at least a lighter fraction and a heavier, liquid fraction comprising 650.degree. F.+ hydrocarbons;
- charging at least a portion of said selectively cracked liquid fraction comprising 650.degree. F.+ hydrocarbons to a catalytic cracking reactor;
- catalytically cracking, in the absence of added hydrogen a cat cracking chargestock comprising a fresh feed comprising normally liquid hydrocarbons boiling above 650.degree. F. and said portion of selectively cracked liquid in a second reactor, a catalytic cracking means operating at catalytic cracking conditions including a reactor temperature of 425.degree.-600.degree. C. and sufficient to convert at least a majority, by volume, of the cat cracking chargestock to lower boiling components and produce catalytically cracked products; and
- fractionating said catalytically cracked products to produce a gasoline boiling range liquid product, at least one fuel oil boiling range liquid product, and at least one product boiling below the gasoline boiling range.
- 2. The process of claim 1 wherein the hydrocarbon chargestock to said shape selective cracking reactor is a gas oil, a vacuum gas oil, a paraffinic resid, a naphthenic resid or mixtures thereof.
- 3. The process of claim 1 wherein the hydrocarbon chargestock to said shape selective cracking reactor is essentially free of hydrocarbons boiling above 1000.degree. F.+ and the hydrocarbon chargestock to the catalytic cracking reactor comprises at least 10 wt % 1000.degree. F.+ material.
- 4. The process of claim 1 wherein the cracked products from the shape selective cracking reactor are separated to produce at least one light product fraction boiling below 700.degree. F. and at least one liquid product boiling above 700.degree. F., and said light product fraction is charged to and fractionated in said catalytic cracking fractionator and said liquid product boiling above 700.degree. F. is mixed with the feed to said catalytic cracking reactor.
- 5. The process of claim 1 wherein the shape selective cracking catalyst contains at least 30 wt % zeolites having a Constraint Index (CI) of 1-12.
- 6. The process of claim 1 wherein the shape selective cracking catalyst contains at least 30 wt % of a zeolite is selected from the group of ZSM-5, ZSM-12, MCM-22, zeolite Beta and mixtures thereof.
- 7. The process of claim 1 wherein the shape selective cracking catalyst consists of zeolites in a matrix, and the matrix is at least 95 wt % silica.
- 8. The process of claim 1 wherein the shape selective cracking reactor is a riser reactor.
- 9. A multi-stage process for the catalytic cracking of a first chargestock having less than 10 wt % 1000.degree. F.+ components selected from the group of a vacuum gas oil, a paraffinic distillate and a naphthenic distillate and mixtures thereof and a second chargestock having at least 10 wt % 1000.degree. F.+ components to lighter products comprising:
- heating and completely vaporizing said first chargestock;
- shape selectively cracking, in a first reactor in the absence of added hydrogen, said vaporized first chargestock in a shape selective cracking reactor containing an inventory of shape selective cracking catalyst containing zeolites selected from the group of ZSM-5, ZSM-12, MCM-22, zeolite Beta and mixtures thereof, and operating at shape selective cracking conditions including a pressure of atmospheric to 100 psig, and a temperature and space velocity sufficient to convert less than 50 volume % of said first chargestock to selectively cracked products including lower boiling iso-olefin components and normally liquid products boiling above 700.degree. F.;
- cooling, condensing, and separating selectively cracked products to produce at least one normally liquid fraction comprising 650.degree. F.+ hydrocarbons and at least one lighter fraction comprising selectively cracked products boiling below 650.degree. F.;
- catalytically cracking, in a second reactor, a catalytic cracking reactor operating at catalytic cracking conditions including a reactor temperature of 425.degree.-600.degree. C. and, said second chargestock having at least 10 wt % 1000.degree. F.+ components and at least a portion of said normally liquid fraction boiling above 650.degree. F. from said shape selective cracking reactor, by contact with a source of hot regenerated FCC catalyst to produce catalytically cracked products and spent FCC catalyst; and
- fractionating, in an FCC main fractionator, said catalytically cracked products from said FCC reactor to produce a plurality of catalytically cracked product fractions including a gasoline boiling range fraction, a fuel oil fraction boiling above the gasoline range and at least one fraction boiling below the gasoline range.
- 10. The process of claim 9 wherein said at least one lighter fraction comprising selectively cracked products boiling below 700.degree. F.+ from the shape selective cracking reactor is charged to said FCC main fractionator.
- 11. The process of claim 9 wherein the FCC catalyst is regenerated in a catalyst regenerator operating at catalyst regeneration conditions including a temperature of 1100.degree. to 1500.degree. F. and said shape selective cracking catalyst is regenerated in a catalyst regenerator operating at catalyst regeneration conditions including a temperature of 950 to 1350.degree. F. and at least 100.degree. F. below the temperature in said FCC catalyst regenerator.
- 12. The process of claim 9 wherein said selectively cracked products are cooled, condensed, and separated to produce a normally liquid fraction boiling above 400.degree. F. and at least one lighter fraction comprising selectively cracked products boiling below 400.degree. F.; and said liquid product boiling above 400.degree. F. is mixed with the feed to the catalytic cracking reactor, and said selectively cracked product boiling below 400.degree. F. is charged to said FCC main fractionator.
- 13. A process for the catalytic cracking of a first chargestock which is wholly distillable and a second chargestock having at least 10 wt % non-distillable components boiling above 1000.degree. F. comprising:
- heating said first chargestock;
- shape selectively cracking in a first reactor, in the absence of added hydrogen, said first chargestock in a shape selective cracking reactor containing an inventory of shape selective cracking catalyst containing zeolites selected from the group of ZSM-5, ZSM-12, MCM-22, zeolite Beta and mixtures thereof, and operating at shape selective cracking conditions including a temperature and space velocity sufficient to convert from less than 50 volume % of said first chargestock to selectively cracked products;
- fractionating, in a fractionator having no more than three product withdrawal lines, said selectively cracked products to produce at least a selectively cracked liquid fraction comprising 650.degree. F.+ liquid and a selectively cracked vapor fraction;
- charging to a catalytic cracking reactor said selectively cracked liquid fraction;
- catalytically cracking, in said catalytic cracking reactor operating at catalytic cracking conditions including a reactor temperature of 425.degree.-600.degree. C. and, said second chargestock having at least 10 wt % 1000.degree. F.+ components and said selectively cracked liquid fraction by contact with a source of hot regenerated FCC catalyst to produce catalytically cracked products and spent FCC catalyst;
- fractionating, in an FCC main fractionator, said catalytically cracked products from said FCC reactor to produce a plurality of product fractions including a gasoline boiling range fraction, a fuel oil fraction boiling above the gasoline range and at least one fraction boiling below the gasoline range; and
- charging said selectively cracked vapor fraction to said FCC main fractionator.
- 14. The process of claim 13 wherein said selectively cracked vapor is added to said FCC main fractionator at an elevation above the point of addition of catalytically cracked products from said FCC reactor.
- 15. The process of claim 13 wherein said selectively cracked products are fractionated in a vapor liquid separator having a vapor line connective with said FCC main column and a liquid line connective with said FCC reactor.
Parent Case Info
This is a continuation of application Ser. No. 07/807,005, filed on Dec. 13, 1991, now abandoned.
US Referenced Citations (15)
Continuations (1)
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Number |
Date |
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807005 |
Dec 1991 |
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