Catalytic cracking process

Claim 2

A fluid catalytic cracking process in which the virgin hydrocarbon feed is contacted in succession with a recycled spent catalyst prior to any contact with regenerated catalyst and then without separation of recycled spent catalyst and oil contact with a freshly regenerated catalyst to produce an improved yield structure, which process comprises the steps of: a. contacting a hydrocarbon feed in a primary short time dilute phase riser reaction zone with a recycled spent catalyst stream from a spent catalyst stripping zone in an amount sufficient to vaporize the oil feed and deposit nitrogen and carbon residue type contaminants in the feed on the spent catalyst; b. passing the feed and spent catalyst in admixture to a secondary riser reaction zone where freshly regenerated catalyst is added in an amount sufficient to obtain the desired conversion of and yield and quality of products from the oil feed; c. discharging the mixture into a separation zone to effect separation of the products and unreacted feed from the spent catalyst; d. recovering product and unreacted feed and passing spent catalyst from said separation means into a spent catalyst stripping zone to remove absorbed and interstitial hydrocarbons to form stripped spent catalyst containing coke; e. passing a portion of stripped spent catalyst from the stripping zone to the primary reaction zone as the recycle spent catalyst stream of step (a) above at a rate sufficient to vaporize the oil feed and deposit nitrogen and carbon residue type contaminants in the feed on the recycled spent catalyst; f. passing simultaneously a second portion of stripped spent catalyst from the stripping zone into a regeneration zone wherein coke is oxidized from the said catalyst to produce freshly regenerated catalyst; g. passing freshly regenerated catalyst from said regeneration zone to the secondary reaction zone of step (b) above at a rate sufficient to obtain the desired conversion of and yield and quality of products from the oil feed.

Claim 3

The process of claim 1 further characterized in that the catalytic cracking conditions in the primary reaction zone of step (a) include a temperature within the range of about 800° to 950° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 5 seconds.

Claim 4

The process of claim 1 further characterized in that the catalytic cracking conditions in the secondary reaction zone of step (b) include a temperature within the range of about 900° to 1100° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 15 seconds.

Claim 5

The process of claim 1 further characterized in that the catalytic cracking conditions include the presence of a diluent to reduce the partial pressure of the hydrocarbon feed.

Claim 6

The process of claim 1 further characterized in that the oxidizing conditions in the regeneration zone include a temperature within the range of about 1100° to 1500° F, a pressure from about atmospheric to about 100 psig, and a catalyst residence time of from about 1 to about 10 minutes.

Claim 7

The process of claim 1 further characterized in that the regeneration zone comprises a dense bed of catalyst with a dilute phase positioned above and in connection with it.

Claim 8

The process of claim 1 in which the spent catalyst recycled to the primary reaction zone of step (a) above is withdrawn from the top section of the stripping zone.

Claim 9

The process of claim 1 in which the portion of the hydrocarbon feed which is recycled from the recovery system as unreacted feed or as a product of the cracking reaction is fed to the secondary reaction zone along with the freshly regenerated catalyst.

Claim 10

A fluid catalytic cracking process in which the virgin hydrocarbon feed is contacted in succession with a recycled spent catalyst prior to any contact with regenerated catalyst and then without separation of recycled spent catalyst and oil contact with a freshly regenerated catalyst to produce an improved yield structure which process comprises the steps of: a. contacting a hydrocarbon feed in a primary shorttime dilute phase riser reaction zone with a recycled spent catalyst stream from a spent catalyst stripping zone at a temperature within the range of about 800° to 950° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 5 seconds; b. passing the feed and spent catalyst in admixture to a secondary riser reaction zone where it is contacted with freshly regenerated catalyst at a temperature within the range of about 900° to 1100° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 15 seconds; c. discharging the mixture into a separation zone to effect separation of the products and unreacted feed from the spent catalyst; d. recovering product and unreacted feed and passing spent catalyst from said separation means into a spent catalyst stripping zone to remove absorbed and interstitial hydrocarbons to form stripped spent catalyst containing coke; e. passing a portion of stripped spent catalyst from the stripping zone to the primary reaction zone as the recycle spent catalyst stream of step (a) above at a rate sufficient to vaporize the oil feed and deposit nitrogen and carbon residue type contaminants in the feed on the recycle spent catalyst; f. passing simultaneously a second portion of stripped spent catalyst from the stripping zone into a regeneration zone wherein coke is oxidized from said catalyst to produce freshly regenerated catalyst at a temperature within the range of about 1100° to 1500° F, a pressure from about atmospheric to about 100 psig, and a catalyst residence time of about 1 to about 10 minutes; g. passing freshly regenerated catalyst from said regeneration zone to the secondary reaction zone of step (b) above at a rate sufficient to obtain the desired conversion of and yield and quality of products from the oil feed.

Claim 11

A fluid catalytic cracking process in which the virgin hydrocarbon feed is contacted in succession with a recycled spent catalyst prior to any contact with regenerated catalyst and then without separation of recycled spent catalyst and oil contact with a freshly regenerated catalyst to produce an improved yield structure which process comprises the steps of: a. contacting a hydrocarbon feed in a primary shorttime dilute phase riser reaction zone with a recycled spent catalyst stream from a spent catalyst stripping zone at a temperature within the range of about 800° to 950° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 5 seconds; b. passing the feed and spent catalyst in admixture to a secondary riser reaction zone where it is contacted with freshly regenerated catalyst at a temperature within the range of about 900° to 1100° F, a pressure within the range of about atmospheric to about 100 psig, and a hydrocarbon residence time of less than 15 seconds; c. discharging the mixture into a separation zone to effect separation of the products and unreacted feed from the spent catalyst; d. recovering product and unreacted feed and passing spent catalyst from said separation means into a spent catalyst stripping zone to remove absorbed and interstitial hydrocarbons to form stripped spent catalyst containing coke; e. passing a portion of stripped spent catalyst from the stripping zone to the primary reaction zone as the recycle spent catalyst stream of step (a) above at a rate sufficient to vaporize the oil feed and deposit nitrogen and carbon residue type contaminants in the feed on the recycle spent catalyst; f. passing simultaneously a second portion of stripped spent catalyst from the stripping zone into a regeneration zone wherein coke is oxidized from said catalyst to produce freshly regenerated catalyst at a temperature within the range of about 1100° to 1500° F, a pressure from about atmospheric to about 100 psig, and a catalyst residence time of about 1 to about 10 minutes; g. passing freshly regenerated catalyst from said regeneration zone to the secondary reaction zone of step (b) above at a rate sufficient to obtain the desired conversion of and yield and quality of products from the oil feed.

Claim 12

The process of claim 9 further characterized in that the catalytic cracking conditions include the presence of a diluent to reduce the partial pressure of the hydrocarbon feed.