Process for extraction of aromatics from petroleum streams

Abstract

The present invention provides a process for the extraction of aromatics from petroleum fractions i.e. naphtha, kerosene and gas oil, using re-extraction route for recovery of solvent.

We claim:  
     
         1 . A process for the extraction of aromatics from petroleum feed streams which comprises: 
 (a) contacting a petroleum feed with a polar organic solvent containing 2-20 wt % antisolvent in a extractor-A column to obtain a extract phase and a raffinate phase,    (b) contacting extract phase obtained in step (a) with 1-6 vol % of a secondary solvent in the extractor-B column to recover the extract hydrocarbons,    (c) distilling the bottom stream of extractor-B obtained in step (b) in column-F at reboiler temperature to recover the extraction solvent for further recycling    (d) washing the top stream of extractor-B obtained in step (b) with water in column-C, followed by fractionating the resultant hydrocarbons to obtain the extract hydrocarbons and secondary solvent and further recycling the secondary solvent to extractor-B,    (e) washing raffinate phase obtained in step (a) in column-E to obtain raffinate hydrocarbons.    
     
     
         2 . A process as claimed in  claim 1  wherein step (a) is carried out at a temperature in the range of 20-80° C.  
     
     
         3 . A process as claimed in  claim 1  wherein step (b) is carried out at a temperature in the range of 20-60° C. to recover the extract hydrocarbons.  
     
     
         4 . A process as claimed in  claim 1  wherein the reboiler temperature in step (c) is in the range of 90-180° C.  
     
     
         5 . A process as claimed in  claim 1  wherein flashing of top stream of extractor-B obtained in step (b) with water in column C. is done at temperature in range of 20-60° C., followed by fractionation of resultant hydrocarbons at temperature in the range of 100-400° C.  
     
     
         6 . A process as claimed in  claim 1  wherein the washing of the raffinate phase obtained in step (a) in Column E in step (e) is carried out at a temperature in the range of 20-60° C.  
     
     
         7 . A process as claimed in  claim 1  wherein the petroleum feed comprises an aromatic rich feed with a boiling temperature in the range of 90-360° C.  
     
     
         8 . A process as claimed in  claim 1  wherein the selective solvent used is N-Methyl pyrolidinone admixed with 2.0 to 15 wt. % water or sulpholane or glycol.  
     
     
         9 . A process as claimed in  claim 1  wherein the ratio of solvent mixture to feed is in the range of 1:1 to 5:1 wt %.  
     
     
         10 . A process as claimed in  claim 1  wherein the feed and extraction solvent is contacted countercurrently in extractor-A at a temperature in the range of 30˜80° C.  
     
     
         11 . A process as clamed in  claim 1  wherein the recovery of aromatics from extract phase is effected countercurrently in extractor-B using a secondary solvent selected from C6-C7 petroleum fraction at a temperature in the range of 30-60° C.  
     
     
         12 . A process as claimed in  claim 1  wherein the ratio of secondary solvent to extract phase is in range of 1 to 4 by volume.  
     
     
         13 . A process as claimed in  claim 1  wherein recovery of solvent from top phase of extractor-B and raffinate phase is done by water washing at temperature in range of 30-40° C.  
     
     
         14 . A process as claimed in  claim 1  wherein recovery of secondary solvent from top of extractor-B is done by distillation at atmospheric pressure at a temperature in the range of 110-300° C.  
     
     
         15 . A process as claimed in  claim 1  wherein the recovery of residual hydrocarbons in the bottom phase of extractor-B is done by distillation at a reboiler temperature in the range of 100-160° C.  
     
     
         16 . A process as claimed in  claim 1  wherein the petroleum feed is selected from the group consisting of heavy naphtha, kerosene and gas oil.  
     
     
         17 . A process as claimed in  claim 1  wherein the aromatics obtained are selected from the group consisting of high octane benzene free stock for gasoline pool, high Cetane Diesel, high aromatic solvent and feed-stock for needle coke production.  
     
     
         18 . A process as claimed in  claim 1  wherein refinery cut light naphtha cut is used as the re-extraction solvent.