Naphtha and cycle oil conversion process

Abstract

The invention relates to a process for converting naphtha and cycle oils produced in catalytic cracking reactions into light olefins. More particularly, the invention relates to a process for hydroprocessing a catalytically cracked light cycle oil, and then re-cracking it along with naphtha in an upstream zone of the primary FCC riser reactor.

What is claimed is:  
     
         1 . A process for catalytically cracking a hydrocarbonaceous feed comprising the steps of: 
 (a) introducing a catalytic cracking catalyst into a FCC riser reactor, said riser reactor having a first reaction zone and a second reaction zone, said first reaction zone downstream from said second reaction zone;    (b) introducing said hydrocarbonaceous feed into said first reaction zone;    (c) contacting said hydrocarbonaceous feed with said catalytic cracking catalyst in said first reaction zone under catalytic cracking conditions to produce a cracked product;    (d) separating said cracked product from said catalyst;    (e) stripping said catalyst;    (f) separating at least a naphtha fraction and a cycle oil fraction from said cracked product, said cycle oil fraction containing aromatic species;    (g) hydroprocessing at least a portion of said cycle oil fraction to saturate a substantial portion of said aromatic species in said cycle oil fraction, thereby forming a hydroprocessed cycle oil;    (h) contacting said catalyst from step (e) with a gas comprising oxygen;    (i) introducing said naphtha fraction and said hydroprocessed cycle oil into said second reaction zone; and,    (j) contacting said naphtha fraction and said hydroprocessed cycle oil with said catalytic cracking catalyst under catalytic cracking conditions in said second reaction zone, thereby producing a product stream having an increased concentration of C 2  to C 4  olefins.    
     
     
         2 . The process according to    claim 1    further comprising the step of introducing steam into said first reaction zone.  
     
     
         3 . The process according to    claim 1    further comprising the step of introducing steam into said second reaction zone.  
     
     
         4 . The process according to    claim 1    wherein said naphtha fraction and said hydroprocessed cycle oil are injected into said second reaction zone at a rate sufficient to keep the weight ratio of the total naphtha fraction and hydroprocessed cycle oil to said catalyst between about 1 and 100.  
     
     
         5 . The process according to    claim 1    wherein the temperature in said first reaction zone is between about 450° C. and about 650° C.  
     
     
         6 . The process according to    claim 1    wherein the temperature in said second reaction zone is between about 550° C. and about 700° C.  
     
     
         7 . The process according to    claim 1    wherein the weight ratio of said naphtha fraction to hydroprocessed cycle oil is between about 1 and 10.  
     
     
         8 . The process according to    claim 1    wherein the weight of said aromatic species in said hydroprocessed cycle oil is less than or equal to about 1 wt. % of the total weight of the hydroprocessed cycle oil introduced into said second reaction zone.  
     
     
         9 . A process for catalytically cracking a hydrocarbonaceous feed comprising the steps of: 
 (a) contacting said hydrocarbonaceous feed with a catalytic cracking catalyst in a FCC reactor under catalytic cracking conditions to form a cracked product;    (b) separating at least a naphtha fraction and a cycle oil fraction from said cracked product, said cycle oil containing aromatic species;    (c) hydroprocessing at least a portion of said cycle oil fraction to convert a substantial portion of said aromatic species in said cycle oil fraction, thereby forming a hydroprocessed cycle oil; and,    (d) introducing said naphtha fraction and said hydroprocessed cycle oil into said FCC reactor at a point upstream from a point at which said hydrocarbonaceous feed is contacted with said catalytic cracking catalyst.    
     
     
         10 . The process according to    claim 9    further comprising the step of contacting said naphtha fraction and said hydroprocessed cycle oil with said catalytic cracking catalyst.  
     
     
         11 . The process according to    claim 10    wherein said naphtha fraction and said hydroprocessed cycle oil are introduced at a rate sufficient to keep the weight ratio of the naphtha fraction and hydroprocessed cycle oil to catalyst between about 1 and 100.  
     
     
         12 . The process according to    claim 11    wherein the weight ratio of said naphtha fraction to hydroprocessed cycle oil is between about 1 and 10.  
     
     
         13 . The process according to    claim 12    wherein the weight of said aromatic species in said hydroprocessed cycle oil is less than or equal to about 1 wt. % of the total weight of the hydroprocessed cycle oil introduced into said FCC reactor upstream from said point at which said hydrocarbonaceous feed is contacted with said catalytic cracking catalyst.  
     
     
         14 . The process according to    claim 13    further comprising the step of separating said cracked product from said catalyst.  
     
     
         15 . The process according to    claim 14    further comprising the step of stripping said catalyst.  
     
     
         16 . The process according to    claim 15    further comprising the step of regenerating said catalyst.  
     
     
         17 . The process according to    claim 16    further comprising the step of introducing a regenerated catalyst into said FCC reactor.  
     
     
         18 . The process according to    claim 1    wherein said naphtha fraction and said hydroprocessed cycle oil are injected into said second reaction zone at a rate sufficient to keep the weight ratio of the total naphtha fraction and hydroprocessed cycle oil to said catalyst between about 1 and 5.  
     
     
         19 . The process according to    claim 13    wherein said naphtha fraction and said hydroprocessed cycle oil are injected into said second reaction zone at a rate sufficient to keep the weight ratio of the total naphtha fraction and hydroprocessed cycle oil to said catalyst between about 1 and 5.  
     
     
         20 . The process according to    claim 1    wherein the weight ratio of said naphtha fraction to hydroprocessed cycle oil is between about 3 and 4.  
     
     
         21 . The process according to    claim 12    wherein the weight ratio of said naphtha fraction to hydroprocessed cycle oil is between about 3 and 4.  
     
     
         22 . The process according to    claim 1    wherein the weight of said aromatic species in said hydroprocessed cycle oil is less than or equal to about 0.1 wt. % of the total weight of the hydroprocessed cycle oil introduced into said second reaction zone.  
     
     
         23 . The process according to    claim 13    wherein the weight of said aromatic species in said hydroprocessed cycle oil is less than or equal to about 0.1 wt. % of the total weight of the hydroprocessed cycle oil introduced into said FCC reactor upstream from said point at which said hydrocarbonaceous feed is contacted with said catalytic cracking catalyst.  
     
     
         24 . The process according to    claim 13    wherein the weight of said aromatic species in said hydroprocessed cycle oil is less than or equal to about 0.01 wt. % of the total weight of the hydroprocessed cycle oil introduced into said FCC reactor upstream from said point at which said hydrocarbonaceous feed is contacted with said catalytic cracking catalyst.