Methods for splitting mixed hydrocarbon streams

Abstract

Methods of extracting and enriching high value pentane streams suitable for adding to refinery grade gasoline are provided by balancing the relative amounts of isopentane and n-pentane in the output stream of a depentanizer tower, and by balancing the sulfur fractions in the input and output streams of the tower.

1 ) A method of making pentanes suitable for mixing into a refined gasoline stream meeting applicable ASTM specifications comprising:
 a) providing a natural gasoline stream comprising:
 i) 0 wt % methane or ethane or propane; 
 ii) from 0 to 5.0 wt % butane; 
 iii) from 5 to 80 wt % isopentane; 
 iv) from 5 to 80 wt % normal pentane; and 
 v) from 10 to 90 wt % of hydrocarbons consisting of 6 or more carbon atoms (C 6+  hydrocarbons); 
   b) splitting said natural gasoline stream into a bottom stream and an enriched overhead pentane stream comprising:
 i) greater than 95 wt % of said butane in said natural gasoline stream; 
 ii) greater than 95 wt % of said isopentane in said natural gasoline stream; 
 iii) greater than 95 wt % of said normal pentane in said natural gasoline stream; and 
 iv) from 0 to 20 wt % of said C 6+  hydrocarbons in said natural gasoline stream; and 
   c) recovering said enriched overhead pentane stream.   
     
     
         2 ) The method of  claim 1  comprising splitting said natural gasoline stream in a distillation column comprising from 15 to 70 trays having a tray efficiency of greater than 80%. 
     
     
         3 ) The method of  claim 1  wherein:
 a) said natural gasoline stream comprises:
 i) from 0.01 to 1.5 wt % butane; 
 ii) from 10 to 50 wt % isopentane; 
 iii) from 10 to 50 wt % normal pentane; and 
 iv) from 20 to 80 wt % C6+ hydrocarbons; 
 
 b) said enriched overhead pentane stream comprises:
 i) greater than 98 wt % of said butane in said natural gasoline stream; 
 ii) greater than 97 wt % of said isopentane in said natural gasoline stream; 
 iii) greater than 97 wt % of said normal pentane in said natural gasoline stream; and 
 iv) from 0.1 to 5 wt % of said C6+ hydrocarbons in said natural gasoline stream. 
 
 
     
     
         4 ) The method of  claim 1  wherein:
 a) said natural gasoline stream comprises:
 i) from 0 to 0.5 wt % butane; 
 ii) from 15 to 35 wt % isopentane; 
 iii) from 15 to 35 wt % normal pentane; and 
 iv) from 30 to 70 wt % C6+ hydrocarbons; 
 
 b) said enriched overhead pentane stream comprises:
 i) greater than 99.5 wt % of said butane in said natural gasoline stream; 
 ii) greater than 98 wt % of said isopentane in said natural gasoline stream; 
 iii) greater than 98 wt % of said normal pentane in said natural gasoline stream; and 
 iv) from 0.01 to 2 wt % of said C6+ hydrocarbons in said natural gasoline stream. 
 
 
     
     
         5 . The method of  claim 1  wherein said natural gasoline stream comprises less than 5 or 2 wt % of olefinic and aromatic compounds. 
     
     
         6 ) The method of  claim 1 , wherein:
 a) said liquid gasoline stream comprises from 5 to 50 ppm sulfur compounds;   b) said enriched overhead pentane stream comprises less than 60% of said sulfur compounds in said liquid gasoline stream; and   c) said enriched overhead pentane stream comprises greater than 1 and less than 30 ppm sulfur compounds.   
     
     
         7 ) The method of  claim 1 , wherein:
 a) said liquid gasoline stream comprises from 10 to 30 ppm sulfur compounds;   b) said enriched overhead pentane stream comprises less than 40% of said sulfur compounds in said natural gasoline stream; and   c) said enriched pentane stream comprises greater than 1 and less than 10 ppm sulfur compounds.   
     
     
         8 ) The method of  claim 1 , wherein:
 a) said liquid gasoline stream comprises from 15 to 40 ppm sulfur compounds;   b) said enriched overhead pentane stream comprises less than 60% of said sulfur compounds in said natural gasoline stream; and   c) said enriched pentane stream comprises greater than 1 and less than 10 ppm sulfur compounds.   
     
     
         9 ) The method of  claim 6  wherein said sulfur compounds are selected from the group consisting of hydrogen sulfide (H 2 S), carbonyl sulfide (COS), methyl mercaptan (MeSH), ethyl mercaptan (EtSH), carbon disulfide (CS 2 ), isopropyl mercaptan (iC 3 SH), and isobutyl mercaptan (iC 4 SH). 
     
     
         10 ) An enriched pentane stream suitable for mixing into a refined gasoline stream meeting ASTM D4814-13b made by the process of  claim 1 . 
     
     
         11 ) An enriched pentane stream suitable for mixing into a refined gasoline stream meeting ASTM D4814-13b comprising:
 a) 0 wt % methane or ethane or propane;   b) from 0.01 to 5 wt % butane;   c) from 30 to 70 wt % isopentane;   d) from 30 to 70 wt % normal pentane; and   e) from 0.01 to 5 wt % hydrocarbons having 6 or more carbons.   
     
     
         12 ) The enriched pentane stream of  claim 11  comprising greater than 1 ppm and less than 30 ppm sulfur compounds. 
     
     
         13 ) The enriched pentane stream of  claim 11  comprising greater than 1 ppm and less than 10 ppm sulfur compounds. 
     
     
         14 ) The enriched pentane stream of  claim 12  wherein said sulfur compounds are selected from the group consisting of hydrogen sulfide (H 2 S), carbonyl sulfide (COS), methyl mercaptan (MeSH), ethyl mercaptan (EtSH), carbon disulfide (CS2), isopropyl mercaptan (iC 3 SH), and isobutyl mercaptan (iC 4 SH).