Catalytic cracking in two stages
AssigneeMobil Oil Corporation
InventorsMohsen N. Harandi, Hartley Owen
Life of this patent
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Abstract
A process for multi-stage catalytic cracking is disclosed. A first stage cracks a first feed at atmospheric to 100 psig over a shape selective zeolite to convert from 10 to 90%, by volume, to lighter products rich in iso-compounds which may be used to make ethers. A second feed, which may include 700.degree. F.+ liquid from the selective cracking reaction, is cracked in a catalytic cracking (FCC) unit. Preferably all or some of the products from the shape selective cracking reactor are fractionated in the FCC main column.
Claims15
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.
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.
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.
Dependencies are inferred from the claim text.