Method and apparatus for making a middle distillate product and lower olefins from a hydrocarbon feedstock

Abstract

Disclosed is a process for making middle distillate and lower olefins. The process includes catalytically cracking a gas oil feedstock within a riser reactor zone by contacting under suitable catalytic cracking conditions within the riser reactor zone the gas oil feedstock with a middle distillate selective cracking catalyst that comprises amorphous silica alumina and a zeolite to yield a cracked gas oil product and a spent cracking catalyst. The spent cracking catalyst is regenerated to yield a regenerated cracking catalyst. Within a dense bed reactor zone and under suitable high severity cracking conditions a gasoline feedstock is contacted with the regenerated cracking catalyst to yield a cracked gasoline product and a used regenerated cracking catalyst. The used regenerated cracking catalyst is utilized as the middle distillate selective catalyst.

1 . A process for making middle distillate and lower olefins, said process comprises: 
 catalytically cracking a gas oil feedstock within a riser reactor zone by contacting under suitable catalytic cracking conditions within said riser reactor zone said gas oil feedstock with a middle distillate selective cracking catalyst that comprises amorphous silica alumina and a zeolite to yield a riser reactor product comprising a cracked gas oil product and a spent cracking catalyst;    regenerating said spent cracking catalyst to yield a regenerated cracking catalyst;    contacing within a dense bed reactor zone and under suitable high severity cracking conditions a gasoline feedstock with said regenerated cracking catalyst to yield a cracked gasoline product and a used regenerated cracking catalyst; and    using said used regenerated cracking catalyst as said middle distillate selective catalyst.    
   
   
       2 . A process as recited in  claim 1 , further comprising: 
 separating said riser reactor product into said cracked gas oil product and said spent cracking catalyst.    
   
   
       3 . A process as recited in  claim 2 , further comprising: 
 adding to said regenerated cracking cracking catalyst a ZSM-5 additive.    
   
   
       4 . A process as recited in  claim 3 , further comprising: 
 introducing steam into said dense bed reactor zone.    
   
   
       5 . A process as recited in  claim 5 , wherein said suitable catalytic cracking conditions are such as to provide for a conversion of said gas oil feedstock in the range of from 40 to 85 weight percent of the total gas oil feedstock.  
   
   
       6 . A process as recited in  claim 5 , wherein said used regenerated cracking catalyst includes a small concentration of carbon.  
   
   
       7 . A process, comprising: 
 contacting a gas oil feedstock within a riser reactor zone under suitable catalytic cracking conditions with a cracking catalyst and yielding a riser reactor product comprising a cracked gas oil product and a spent cracking catalyst;    separating said riser reactor product into said cracked gas oil product and said spent cracking catalyst;    regenerating said spent cracking catalyst to yield a regenerated cracking catalyst;    splitting said regenerated cracking catalyst into at least a portion of said regenerated cracking catalyst and a remaining portion of said regenerated cracking catalyst;    passing said at least a portion of said spent cracking catalyst to a dense bed reactor zone wherein said at least a portion of said spent cracking catalyst is contacted under suitable high severity cracking conditions with a gasoline feedstock to yield a cracked gasoline product and a used regenerated cracking catalyst; and    using said remaining portion of said regenerated cracking catalyst and said used regenerated cracking catalyst as said cracking catalyst.    
   
   
       8 . A process as recited in  claim 7 , further comprising: 
 mixing with said at least a portion of said spent cracking catalyst a ZSM-5 additive.    
   
   
       9 . A process as recited in  claim 8 , further comprising: 
 introducing steam into said dense bed reactor zone.    
   
   
       10 . A process as recited in  claim 9 , further comprising: 
 separating a slurry product from said cracked gas oil product.    
   
   
       11 . A process as recited in  claim 10 , further comprising: 
 introducing said slurry product to said riser reactor zone.    
   
   
       12 . An apparatus, comprising: 
 riser reactor means for contacting a gas oil feedstock with a catalytic cracking catalyst under catalytic cracking conditions to yield a riser reactor product comprising a cracked gas oil product and a spent cracking catalyst;    separator means for separating said riser reactor product into said cracked gas oil product and said spent cracking catalyst;    regenerator means for regenerating said spent cracking catalyst to yield a regenerated catalyst;    dense bed reactor means for contacting a gasoline feedstock with said regenerated catalyst under high severity conditions to yield a cracked gasoline product and a used regenerated catalyst; and    means for providing for the use of said used regenerated catalyst as said catalytic cracking catalyst.