Absorption recovery processing of FCC-produced light olefins

Abstract

Processing schemes and arrangements are provided for the processing a heavy hydrocarbon feedstock via hydrocarbon cracking processing with selected hydrocarbon fractions being obtained via absorption-based product recovery.

1 . A process for catalytically cracking a heavy hydrocarbon feedstock and obtaining selected hydrocarbon fractions, the process comprising:
 contacting a heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst in a fluidized reactor zone to produce a hydrocarbon effluent comprising a range of cracked hydrocarbon products including light olefins;   separating the hydrocarbon effluent in a separation section to form at least one separator liquid stream and a separator vapor stream, the at least one separator liquid stream comprising C 3 + hydrocarbons, the separator vapor stream comprising C 3 − hydrocarbons;   contacting the separator vapor stream with a first absorption solvent in an absorption zone to remove C 3 + hydrocarbons therefrom and form a process stream comprising C 2 − hydrocarbon materials;   stripping C 2 − hydrocarbon materials from the at least one separator liquid stream to form a C 3 + hydrocarbon process stream substantially free of C 2 − hydrocarbons;   separating C 5 + hydrocarbon materials from the C 3 + hydrocarbon process stream to form a first product process stream comprising C 5 + hydrocarbon materials and a second product process stream comprising C 3  and C 4  hydrocarbons; and   introducing at least a first portion of the first product stream to the absorption zone as at least a portion of the first absorption solvent.   
     
     
         2 . The process of  claim 1  wherein said contacting of the heavy hydrocarbon feedstock with a hydrocarbon cracking catalyst comprises contacting the heavy hydrocarbon feedstock with a blended catalyst comprising regenerated catalyst and coked catalyst in a fluidized reactor zone at hydrocarbon cracking reaction conditions to produce a cracked stream containing hydrocarbon products including light olefins, said catalyst having a catalyst composition including a first component comprising a large pore molecular sieve and a second component comprising a zeolite with no greater than medium pore size, said zeolite with no greater than medium pore size comprising at least 1.0 wt. % of the catalyst composition. 
     
     
         3 . The process of  claim 1  wherein the first portion of the first product stream introduced to the absorption zone comprises a majority of the first absorption solvent therewithin. 
     
     
         4 . The process of  claim 1  additionally comprising splitting at least a second portion of the first product stream in a divided wall separation column to form a light fraction comprising compounds containing four to six carbon atoms, an intermediate fraction comprising compounds containing seven to eight carbon atoms and a heavy fraction comprising compounds containing more than eight carbon atoms. 
     
     
         5 . The process of  claim 1  additionally comprising splitting the second product process stream in a C 3 -C 4  splitter to form a first C 3 -C 4  splitter process stream comprising primarily C 3  hydrocarbons and a second C 3 -C 4  splitter process stream comprising primarily C 4  hydrocarbons. 
     
     
         6 . The process of  claim 5  additionally comprising:
 separating propylene from the C 3 − containing process stream to form a process stream comprising primarily propylene and a process stream comprising primarily propane.   
     
     
         7 . The process of  claim 1  wherein the second product process stream comprising C 3  and C 4  hydrocarbons includes a quantity of mercaptans, the process additionally comprising:
 selectively removing at least a portion of the mercaptans from at least a portion of the second process stream.   
     
     
         8 . The process of  claim 1  wherein the process stream comprising C 2 − hydrocarbon materials additionally comprises a quantity of carbon dioxide, the process additionally comprising:
 treating at least a portion of the process stream comprising C 2 − hydrocarbon materials to remove at least a portion of the quantity of carbon dioxide therefrom.   
     
     
         9 . The process of  claim 1  wherein the process stream comprising C 2 − hydrocarbon materials additionally comprises a quantity of acetylene, the process additionally comprising:
 hydrogenating at least a portion of the quantity of acetylene to form additional ethylene.   
     
     
         10 . The process of  claim 1  additionally comprising:
 demethanizing at least a portion of the process stream comprising C 2 − hydrocarbon materials to form a first demethanizer process stream comprising primarily hydrogen and methane and a second demethanizer process stream comprising primarily C 2  hydrocarbons.   
     
     
         11 . The process of  claim 10  additionally comprising splitting at least a portion of the second demethanizer process stream in a C 2  splitter to form a first C 2  splitter product stream comprising primarily ethylene and a second C 2  splitter product stream comprising primarily ethane. 
     
     
         12 . The process of  claim 1  wherein said contacting the separator vapor stream with a first absorption solvent in an absorber zone comprises:
 contacting the separator vapor stream with a first absorption solvent in a primary absorber to form a first primary absorber process stream comprising primarily C 2 − hydrocarbons and residual amounts of C 3 + hydrocarbons; and   contacting the first primary absorber process stream with a second absorption solvent in a secondary absorber to form the overhead stream comprising C 2 − hydrocarbon materials and a process stream comprising residual C 3 + hydrocarbons and the second absorption solvent.   
     
     
         13 . A process for catalytically cracking a heavy hydrocarbon feedstock and obtaining selected hydrocarbon fractions, the process comprising:
 contacting a heavy hydrocarbon feedstock with a blended cracking catalyst comprising regenerated catalyst and coked catalyst in a fluidized reactor zone at hydrocarbon cracking reaction conditions to produce a hydrocarbon effluent stream comprising a range of hydrocarbon products including light olefins, said catalyst having a catalyst composition including a first component comprising a large pore molecular sieve and a second component comprising a zeolite with no greater than medium pore size, said zeolite with no greater than medium pore size comprising at least 1.0 wt. % of the catalyst composition;   separating the hydrocarbon effluent in a separation section to form at least one separator high pressure liquid stream and a separator high pressure vapor stream, the at least one separator high pressure liquid stream comprising C 3 + hydrocarbons, the separator high pressure vapor stream comprising C 3 − hydrocarbons;   contacting the separator high pressure vapor stream with a first absorption solvent in a primary absorber to form a first primary absorber process stream comprising primarily C 2 − hydrocarbons and residual amounts of C 3 + hydrocarbons;   contacting the first primary absorber process stream with a second absorption solvent to form a process stream comprising C 2 − hydrocarbon materials and a process stream comprising residual C 3 + hydrocarbons and the second absorption solvent;   stripping C 2 − hydrocarbon materials from the separator high pressure liquid stream to form a C 3 + hydrocarbon process stream substantially free of C 2 − hydrocarbons;   separating C 5 + hydrocarbon materials from the C 3 + hydrocarbon process stream to form a first product process stream comprising C 5 + hydrocarbon materials and a second product process stream comprising C 3  and C 4  hydrocarbons; and   introducing at least a first portion of the first product stream to the primary absorber as a majority of the first absorption solvent.   
     
     
         14 . The process of  claim 13  additionally comprising splitting at least a second portion of the first product stream in a divided wall separation column to form a light fraction comprising compounds containing four to six carbon atoms, an intermediate fraction comprising compounds containing seven to eight carbon atoms and a heavy fraction comprising compounds containing more than eight carbon atoms. 
     
     
         15 . The process of  claim 13  additionally comprising splitting the second product process stream in a C 3 -C 4  splitter to form a first C 3 -C 4  splitter process stream comprising primarily C 3  hydrocarbons and a second C 3 -C 4  splitter process stream comprising primarily C 4  hydrocarbons. 
     
     
         16 . The process of  claim 15  additionally comprising:
 separating propylene from the C 3 − containing process stream to form a process stream comprising primarily propylene and a process stream comprising primarily propane.   
     
     
         17 . The process of  claim 13  wherein the second product process stream comprising C 3  and C 4  hydrocarbons includes a quantity of mercaptans, the process additionally comprising:
 selectively removing at least a portion of the mercaptans from at least a portion of the second process stream.   
     
     
         18 . The process of  claim 12  wherein the process stream comprising C 2 − hydrocarbon materials additionally comprises a quantity of carbon dioxide, the process additionally comprising:
 treating at least a portion of the process stream comprising C 2 − hydrocarbon materials to remove at least a portion of the quantity of carbon dioxide therefrom.   
     
     
         19 . The process of  claim 13  additionally comprising:
 demethanizing at least a portion of the process stream comprising C 2 − hydrocarbon materials to form a first demethanizer process stream comprising primarily hydrogen and methane and a second demethanizer process stream comprising primarily C 2  hydrocarbons; and   splitting at least a portion of the second demethanizer process stream in a C 2  splitter to form a first C 2  splitter product stream comprising primarily ethylene and a second C 2  splitter product stream comprising primarily ethane.   
     
     
         20 . A system for catalytically cracking a heavy hydrocarbon feedstock and obtaining selected hydrocarbon fractions, the system comprising:
 a fluidized reactor zone wherein the heavy hydrocarbon feedstock contacts a blended catalyst comprising regenerated catalyst and coked catalyst at hydrocarbon cracking reaction conditions to produce a cracked effluent stream containing hydrocarbon products including light olefins,   a separation section for separating the a cracked effluent stream to form at least one separator liquid stream and a separator vapor stream, the at least one separator liquid stream comprising C 3 + hydrocarbons, the separator vapor stream comprising C 3 − hydrocarbons;   an absorption zone to absorb C 3 + hydrocarbons from the separator high pressure vapor stream in a first absorption solvent and to form an absorption zone effluent stream comprising C 2 − hydrocarbons, including ethylene,   a stripper for stripping C 2 − hydrocarbon materials from the separator liquid stream to form a C 3 + process stream substantially free of C 2 − hydrocarbons;   a debutanizer for separating C 5 + hydrocarbon materials from the C 3 + hydrocarbon process stream to form a first process stream comprising C 5 + hydrocarbon materials and a second process stream comprising C 3  and C 4  hydrocarbons; and   a process line for introducing at least a first portion of the first product stream to the absorption zone as a majority of the first absorption solvent.