Catalytic cracking of light naphtha over dual riser fcc reactor

Abstract

Systems and methods for producing light olefins and aromatics from light naphtha are disclosed. The light naphtha is fed to a first catalyst riser to crack the C 5 to C 7 hydrocarbons in the light naphtha stream. The cracked naphtha stream is fractionated to produce a stream comprising primarily C 4 to C 6 hydrocarbons or a stream comprising primarily C 5 to C 12 hydrocarbons. When the stream comprising primarily C 4 to C 6 hydrocarbons is fed to the second catalyst riser, the product stream from the second riser comprises light olefins as the main product. When the stream comprising primarily C 5 to C 12 hydrocarbons is fed to the second riser, the product stream from the second riser comprises aromatics as the main product.

1 . A method of producing olefins and aromatics, the method comprising:
 feeding a light naphtha stream to a first catalyst riser of a fluid catalytic cracking (FCC) unit, the light naphtha stream having an initial boiling point (IBP) in a range 15 to 40° C. and a final boiling point (FBP) in a range 65 to 350° C.;   contacting the light naphtha stream with a first catalyst in the first catalyst riser under reaction conditions sufficient to crack C 5  to C 7  hydrocarbons of the light naphtha stream and form a first cracked stream;   fractionating the first cracked stream to produce a plurality of streams that comprises a first stream comprising primarily C 4  to C 6  hydrocarbons;   flowing the first stream to a second catalyst riser of the FCC unit;   contacting the first stream with a second catalyst in the second catalyst riser under reaction conditions sufficient to crack C 4  to C 6  hydrocarbons of the first stream to form a second cracked stream comprising C 2  to C 3  olefins, wherein the first catalyst and the second catalyst are different and wherein the reaction conditions in the first catalyst riser are adapted such that yield of light olefins from C 5  to C 7  hydrocarbons is 20 to 60 wt. % and yield of aromatics from C 5  to C 7  hydrocarbons is 3 to 20 wt. %; and   regenerating the first catalyst and the second catalyst separately.   
     
     
         2 . The method of  claim 1 , wherein the fractionating of the first cracked stream further produces a second stream comprising primarily C 2  to C 3  olefins; a third stream comprising primarily benzene, toluene, and xylene, collectively; and a fourth stream comprising dry gas. 
     
     
         3 . The method of  claim 2 , wherein the fractionating further produces a bottom stream comprising C 12 + hydrocarbons. 
     
     
         4 . The method of  claim 3 , wherein the bottom stream is recycled back to the first catalyst riser. 
     
     
         5 . The method of  claim 2 , wherein the dry gas is used as fluidization medium in the first catalyst riser and/or the second catalyst riser. 
     
     
         6 . The method of  claim 1 , wherein the reaction conditions in the second catalyst riser are adapted such that the yield of light olefins from C 4  to C 6  hydrocarbons is 0 to 90 wt. %. 
     
     
         7 . The method of  claim 1 , wherein the first catalyst and/or the second catalyst comprises an acidic porous zeolite including Mordenite Framework Inverted (MFI), Faujasite (FAU), Mordenite (MOR), Beta, Omega structure type zeolites. 
     
     
         8 . The method of  claim 1 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promotor, or combinations thereof. 
     
     
         9 . The method of  claim 1 , wherein the reaction conditions in the first catalyst riser include a reaction temperature of 600 to 720° C., a steam to hydrocarbon ratio of 0 to 0.5, and dry gas to hydrocarbon ratio of 0 to 0.5. 
     
     
         10 . The method of  claim 1 , wherein the reaction conditions in the second catalyst riser include a reaction temperature of 600 to 720° C., a steam to hydrocarbon ratio of 0 to 0.5, and dry gas to hydrocarbon ratio of 0 to 0.5. 
     
     
         11 . A method of producing olefins and aromatics, the method comprising:
 feeding a light naphtha stream to a first catalyst riser of a fluid catalytic cracking (FCC) unit, the light naphtha stream having an initial boiling point in a range 15 to 40° C. and a final boiling point (FBP) in a range 65 to 350° C.;   contacting the light naphtha stream with a first catalyst in the first catalyst riser under reaction conditions sufficient to crack C 5  to C 7  hydrocarbons of the light naphtha stream and form a first cracked stream;   fractionating the first cracked stream to produce a plurality of streams that comprises a hydrocarbon processing stream comprising primarily C 5  to C 12  hydrocarbons;   flowing the hydrocarbon processing stream to a second catalyst riser of the FCC unit;   contacting the hydrocarbon processing stream with a second catalyst in the second catalyst riser under reaction conditions sufficient to crack C 5  to C 12  hydrocarbons of the hydrocarbon processing stream to form a second cracked processing stream comprising aromatics, wherein the first catalyst and the second catalyst are different, and wherein the reaction conditions in the first catalyst riser are adapted such that yield of light olefins from C 5  to C 7  hydrocarbons is 5 to 35 wt. % and yield of aromatics from C 5  to C 7  hydrocarbons is 5 to 50 wt. % and wherein the reaction conditions in the second catalyst riser are adapted such that yield of aromatics from C 5  to C 12  nonaromatic hydrocarbons is 5 to 60 wt. %; and   regenerating the first catalyst and the second catalyst separately.   
     
     
         12 . The method of  claim 11 , wherein the fractionating further produces a light recycling stream comprising primarily C 4  to C 6  hydrocarbons, a light olefin stream comprising primarily C 2  and C 3  olefins, a dry gas stream comprising primarily methane and hydrogen, collectively, an aromatic stream comprising primarily benzene, toluene, and xylene, collectively. 
     
     
         13 . The method of  claim 12 , wherein the light recycling stream is recycled back to the first catalyst riser. 
     
     
         14 . The method of  claim 11 , wherein the first catalyst and/or the second catalyst comprises an acidic porous zeolite including Mordenite Framework Inverted (MFI), Faujasite (FAU), Mordenite (MOR), Beta, Omega structure type zeolites. 
     
     
         15 . The method of  claim 11 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promoter composition, or combinations thereof. 
     
     
         16 . The method of  claim 12 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promoter composition, or combinations thereof. 
     
     
         17 . The method of  claim 13 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promoter composition, or combinations thereof. 
     
     
         18 . The method of  claim 14 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promoter composition, or combinations thereof. 
     
     
         19 . The method of  claim 15 , wherein the first catalyst and the second catalyst are different in parameters comprising silicon to aluminum ratio, pore size, surface area, promoter composition, or combinations thereof. 
     
     
         20 . The method of  claim 2 , wherein the reaction conditions in the second catalyst riser include a reaction temperature of 600 to 720° C., a steam to hydrocarbon ratio of 0 to 0.5, and dry gas to hydrocarbon ratio of 0 to 0.5.