Processing of FCC naphtha

Abstract

A fluid cracked naphtha stream is subjected to hydrodesulfurization and fractionation, preferably simultaneously in catalytic distillation reactors. The overheads and a portion of the bottoms from the fractionation are recombined to produce a naphtha blend having an ASTM D-86 95% point greater than the end point of the overheads and less than the ASTM D-86 95% point of the bottoms.

1 . A process for the desulfurization of a catalytic cracked naphtha comprising contacting the catalytic cracked naphtha and hydrogen in the presence of the hydrodesulfurization catalyst to react a portion of the organic sulfur compounds contained within the naphtha with hydrogen to form H 2 S; separating the naphtha stream by distillation into a lighter fraction and a heavier fraction; withdrawing the lighter fraction as an overheads; withdrawing the heavier fraction as a bottoms; and combining a portion of the heavier fraction with the lighter fraction to obtain an ASTM D-86 95% point greater than the end point of the lighter fraction and less than the ASTM D-86 95% point of the heavier fraction.  
   
   
       2 . The process according to  claim 1  wherein said contacting and separating are carried out concurrently in a reaction distillation zone.  
   
   
       3 . The process according to  claim 2  comprising contacting said heavier fraction with hydrogen in the presence of the hydrodesulfurization catalyst to react a portion of the organic sulfur compounds contained therein with hydrogen to form H 2 S; separating the heavier fraction by distillation into a second lighter fraction and a second heavier fraction; withdrawing the second lighter fraction as an overheads; withdrawing the second heavier fraction as a bottoms.  
   
   
       4 . The process according to  claim 3  wherein said contacting and separating of the heavier fraction are carried out concurrently in a reaction distillation zone.  
   
   
       5 . The process according to  claim 1  wherein said contacting and separating are carried out consecutively in a fixed bed, straight pass reaction zone followed by a distillation zone.  
   
   
       6 . The prosess according to  claim 5  comprising contacting said heavier fraction with hydrogen in the presence of the hydrodesulfurization catalyst to react a portion of the organic sulfur compounds contained therein with hydrogen to form H 2 S; separating the heavier fraction by distillation into a second lighter fraction and a second heavier fraction; withdrawing the second lighter fraction as an overheads; withdrawing the second heavier fraction as a bottoms.  
   
   
       7 . The process according to  claim 3  wherein said contacting and separating of the heavier fraction are carried out consecutively in a fixed bed, straight pass reaction zone followed by a distillation zone.  
   
   
       8 . The process according to  claim 1  comprising the steps of: 
 (a) feeding hydrogen and a naphtha stream containing organic sulfur compounds to a distillation column reactor containing a bed of hydrodesulfurization catalyst;    (b) concurrently in said distillation column reactor 
 (i) contacting the naphtha and hydrogen in the presence of the hudrodesulfurization catalyst to react a portion of the organic sulfur compounds contained within the naphtha with hydrogen to form, and  
 (ii) separating the naphtha stream into a lighter fraction and a heavier fraction;  
   (c) withdrawing the lighter fraction from the distillation column reactor as an overheads;    (d) withdrawing the heavier fraction from the distillation column reactor as a bottoms; and    (e) combining a portion of the heavier fraction with the lighter fraction to obtain an ASTM D-86 95% point greater than the end point of the lighter fraction and less than the ASTM D-86 95% point of the heavier fraction.    
   
   
       9 . The process according to  claim 8  wherein said lighter fraction is stripped of hydrogen sulfide prior to combining with a portion of said heavier fraction.  
   
   
       10 . The process according to  claim 9  wherein said heavier fraction is stripped of hydrogen sulfide prior to combining a portion of said heavier fraction with said lighter fraction.  
   
   
       11 . The process according to  claim 8  wherein said blend is stripped of hydrogen sulfide.  
   
   
       12 . The process according to  claim 8  wherein said naphtha stream is a full boiling range fluid cracked naphtha containing olefins, mercaptans and other organic sulfur compounds and said full boiling range fluid cracked naphtha is treated to removed mercaptans and C 6  and lighter material prior to feeding to said distillation column reactor.  
   
   
       13 . The process according to  claim 12  wherein the treatment is by thioetherification in a distillation column reactor containing a thioetherification catalyst.  
   
   
       14 . A process for the treatment of a full boiling range fluid cracked naphtha comprising the steps of: 
 (a) feeding hydrogen and a full boiling range fluid cracked naphtha containing olefins, diolefins, mercaptans and other organic sulfur compounds to a first distillation column reactor containing a thioetherification catalyst;    (b) concurrently in said first distillation column reactor, 
 (i) reacting diolefins with mercaptans to form sulfides, and  
 (ii) separating by fractional distillation the C 6  and lighter materials from the C 7  and heavier materials including said sulfides;  
   (c) removing said C 6  and heavier materials from said first distillation column reactor as a first overheads;    (d) removing said C 7  and heavier materials from said first distillation column as a first bottoms;    (e) feeding hydrogen and said first bottoms to a second distillation column reactor containing a bed of hydrodesulfurization catalyst;    (f) concurrently in said distillation column reactor 
 (i) contacting the C 7  and heavier materials and hydrogen in the presence of the hydrodesulfurization catalyst to react a portion of the sulfides and other organic sulfur compounds with hydrogen to form hydrogen sulfide,and  
 (ii) separating the C7 and heavier materials into a first fraction having an ASTM D-86 end point below a second fraction;  
   (g) withdrawing the first fraction from the distillation column reactor as a second overheads;    (h) withdrawing the second fraction from the distillation column reactor as a second bottoms;    (i) stripping said second overheads to remove hydrogen sulfide;    (j) stripping said second bottoms to remove hydrogen sulfide; and    (k) combining a portion of the second fraction with the first fraction to obtain an ASTM D-86 95% point greater than the end point of the first fraction and less than the ASTM D-86 95% point of the second fraction.    
   
   
       15 . A process for the desulfurization of a catalytic cracked naphtha comprising: 
 fractionating a full boiling range naphtha, containing diolefins and organic sulfur compounds, including mercaptan into a first heavy fraction and a light fraction;    contacting the light fraction with a thioetherification catalyst under conditions of concurrent fractionation and reaction to react diolefins and mercaptans to form organic sulfides and to fractionate the organic sulfides into the first heavy fraction;    recovering the light fraction having a reduced sulfur content as overheads;    recovering and fractionating the first heavy fraction into an intermediate fraction and a second heavy fraction;    individually contacting said fist heavy fraction and said intermediate fraction with a hydrogensulfurization catalyst and hydrogen under conditions of concurrent fractionation and reaction to react organic sulfur including organic sulfides from the light fraction with the hydrogen to form H 2 S and hydrocarbons;    recovering the intermediate fraction having a reduced sulfur content from the first heavy feed and combining said intermediate fraction with the light fraction; and    recovering a second heavy fraction having a reduced sulfur content from that of the first heavy feed and combining a portion of the second heavy fraction with the combined intermediate fraction and light fraction to obtain an ASTM D-86 95% point greater than the end point of the combined intermediate fraction and light fraction and less than the ASTM D-86 95% point of the second heavy fraction.    
   
   
       16 . The process according to  claim 1  wherein said combined portions of the heavier fraction with the light fraction has an ASTM D-86 95% point less than the D-86 95% point of the catalyst cracked naphtha.