Process for fluid catalytic cracking

Abstract

The invention relates to a process for the fluid catalytic cracking of hydrocarbons using a downflow reactor and a catalyst with an Akzo Accessibility Index (AAI) of at least 3.5. This process combines the advantages of the use of downflow and riser reactors: minimal overcracking and high conversion of the higher boiling fraction. The use of a downflow reactor minimizes overcracking, while the cracking catalyst facilitates high conversions, even for high-boiling fractions in the feed.

1 . A process for the fluid catalytic cracking of hydrocarbons comprising the following steps: 
 a) atomizing and injecting a hydrocarbon feedstock into the top portion of a tubular downflow reactor and contacting this hydrocarbon feedstock with a catalyst having an AAI of at least 3.5,    b) separating reaction products and spent catalyst at the bottom of said downflow reactor,    c) treating the spent catalyst with steam,    d) regenerating the spent catalyst in a regeneration zone, and    e) recycling the regenated catalyst to the downflow reactor.    
     
     
         2 . The process of  claim 1  wherein the catalyst has an AAI of at least 5.0.  
     
     
         3 . The process of  claim 2  wherein the catalyst has an AAI of at least 6.0.  
     
     
         4 . The process of  claim 1  wherein the catalyst has been obtained by combining catalyst components or precursors thereof in an aqueous medium to form a catalyst precursor mixture, feeding the mixture to a shaping apparatus, and shaping the mixture to form particles, in which process just before being fed to the shaping apparatus the mixture is destabilized.  
     
     
         5 . The process of  claim 1  wherein the catalyst has been obtained by mixing the catalyst components or precursors thereof in an aqueous mixture, adding a pore-forming agent to this mixture, followed by shaping.  
     
     
         6 . The process of  claim 5  wherein the pore-forming agent is a water-soluble carbohydrate.  
     
     
         7 . The process of  claim 1  wherein the catalyst comprises 10-60 wt. % of a solid acid, 0-50 wt. % of alumina, 0-40 wt. % of silica, and the balance kaolin.  
     
     
         8 . The process of  claim 7  wherein the catalyst comprises 20-50 wt. % of solid acid, 5-40 wt. % of alumina, 5-25 wt. % of silica, and the balance kaolin.  
     
     
         9 . The process of  claim 8  wherein the catalyst comprises 25-45 wt. % of solid acid, 10-30 wt. % of alumina, 5-20 wt. % of silica, and the balance kaolin.  
     
     
         10 . The process of  claim 7  wherein the solid acid is selected from the group consisting of ZSM-type zeolites, faujasite-type zeolites, silicoaluminophosphate (SAPO), aluminophosphate (ALPO), and combinations thereof.  
     
     
         11 . The process of  claim 10  wherein the solid acid is a rare earth exchanged zeolite.  
     
     
         12 . The process of  claim 11  wherein the rare earth content of the zeolite is below 16 wt %.