Stable, moderately unsaturated distillate fuel blend stocks prepared by low pressure hydroprocessing of Fischer-Tropsch products

Abstract

The invention relates to a distillate fuel comprising a stable, low sulfur, highly paraffinic, moderately unsaturated distillate fuel blend stock. The highly paraffinic, moderately unsaturated distillate fuel blend stock exhibits excellent combustion properties in diesel and jet engines as a result of the high paraffin content. The blend stock is preferably prepared from a Fischer-Tropsch derived product that is hydroprocessed under conditions during which a moderate amount of unsaturates are formed or retained.

1 . A distillate fuel comprising a Fischer Tropsch distillate fuel blend stock, wherein the Fischer Tropsch distillate fuel blend stock comprises: 
 a) unsaturates in an amount between 2 and 20 weight %;    b) paraffins in an amount 80 weight % or greater;    c) sulfur in an amount less than 1 ppm;    d) a cetane index of greater than 60; and    e) peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60° C. for four weeks.    
   
   
       2 . A distillate fuel according to  claim 1 , wherein the peroxide precursors are in an amount such that less than 4 ppm peroxides are formed after storage at 60° C. for four weeks.  
   
   
       3 . A distillate fuel according to  claim 1 , wherein the peroxide precursors are in an amount such that less than 1 ppm peroxides are formed after storage at 60° C. for four weeks.  
   
   
       4 . A distillate fuel according to  claim 1 , wherein approximately 100 weight % of the distillate fuel is a Fischer Tropsch distillate fuel blend stock.  
   
   
       5 . A distillate fuel according to  claim 1 , further comprising petroleum blend stock.  
   
   
       6 . A distillate fuel according to  claim 5 , wherein the fuel comprises 5 to 75 weight % Fischer Tropsch distillate fuel blend stock and 95 to 25 weight % petroleum blend stock.  
   
   
       7 . A distillate fuel according to  claim 1 , wherein the distillate fuel further comprises nitrogen in an amount less than 1 ppm.  
   
   
       8 . A distillate fuel according to  claim 1 , wherein the unsaturates are in an amount between 2 and 15 weight %.  
   
   
       9 . A distillate fuel according to  claim 1 , wherein the unsaturates are in an amount between 5 and 10 weight %.  
   
   
       10 . A distillate fuel according to  claim 1 , wherein the fuel conforms to at least one specification for either diesel fuel or jet fuel.  
   
   
       11 . A distillate fuel according to  claim 10 , wherein the distillate fuel conforms to at least one specification for a diesel fuel and has a cetane index greater than 60.  
   
   
       12 . A distillate fuel according to  claim 11 , wherein the distillate fuel has a cetane index greater than 65.  
   
   
       13 . A diesel fuel according to  claim 11 , wherein the fuel has a percent reflectance according to ASTM D6468 in excess of 65% when measured at 150° C. for 90 minutes.  
   
   
       14 . A diesel fuel according to  claim 11 , wherein the fuel has a percent reflectance according to ASTM D6468 in excess of 65% when measured at 150° C. for 180 minutes.  
   
   
       15 . A diesel fuel according to  claim 11 , wherein the fuel has a percent reflectance according to ASTM D6468 in excess of 99% when measured at 150° C. for 180 minutes.  
   
   
       16 . A distillate fuel according to  claim 10 , wherein the distillate fuel conforms to at least one specification for a jet fuel and has a passing rating in ASTM D3241 at 260° C. for 2.5 hours.  
   
   
       17 . A distillate fuel according to  claim 16 , wherein the fuel has a passing rating in ASTM D3241 at 270° C. for 2.5 hours.  
   
   
       18 . A distillate fuel according to  claim 16 , wherein the fuel has a passing rating in ASTM D3241 at 300° C. for 2.5 hours.  
   
   
       19 . A Fischer-Tropsch diesel fuel blend stock comprising: 
 a) unsaturates in an amount between 2 and 10 weight % wherein the unsaturates comprise less than 10 weight % polynuclear aromatics;    b) paraffins in an amount 90 weight % or greater;    c) sulfur in an amount less than 1 ppm; and    d) peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60° C. for four weeks,    wherein the Fischer-Tropsch diesel fuel blend stock has a cetane index greater than 60, and a percent reflectance according to ASTM D6468 at 150° C. in excess of 99% when measured at 180 minutes.    
   
   
       20 . A blend stock according to  claim 19 , wherein the blend stock has a cetane index of greater than 65.  
   
   
       21 . A blend stock according to  claim 19 , wherein the blend stock has a cetane index of greater than 70.  
   
   
       22 . A Fischer-Tropsch jet fuel blend stock comprising: 
 a) unsaturates in an amount between 2 and 10 weight % wherein the unsaturates comprise less than 10 weight % polynuclear aromatics;    b) paraffins in an amount 90 weight % or greater;    c) sulfur in an amount less than 1 ppm; and    d) peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60° C. for four weeks,    wherein the Fischer-Tropsch jet fuel blend stock has a smoke point of 30 mm or greater, and a passing rating in ASTM D3241 at 260° C. for 2.5 hours.    
   
   
       23 . A blend stock according to  claim 22 , wherein the fuel has a passing rating in ASTM D3241 at 270° C. for 2.5 hours.  
   
   
       24 . A blend stock according to  claim 22 , wherein the fuel has a passing rating in ASTM D3241 at 300° C. for 2.5 hours.  
   
   
       25 - 32 . (canceled)  
   
   
       33 . A distillate fuel comprising a Fischer Tropsch distillate fuel blend stock, wherein the Fischer Tropsch distillate fuel blend stock is made by a process comprising: 
 a) converting syngas to a Fischer Tropsch derived feedstock by a Fischer Tropsch process;    b) hydroprocessing the Fischer-Tropsch derived feedstock at a temperature of 525-775° F., a pressure of less than 1000 psig, and a liquid hourly space velocity of greater than 0.25 hr −1 ; and    c) recovering a Fischer Tropsch distillate fuel blend stock, wherein the Fischer Tropsch distillate fuel blend stock comprises between 2 and 20 weight % unsaturates, less than 1 ppm sulfur, and peroxide precursors in an amount such that less than 5 ppm peroxides are formed after storage at 60° C. for four weeks.    
   
   
       34 . A distillate fuel according to  claim 33 , wherein the fuel conforms to at least one specification for either diesel fuel or jet fuel.  
   
   
       35 . A distillate fuel according to  claim 34 , wherein the fuel conforms to at least one specification for a diesel fuel and has a cetane index greater than 60.  
   
   
       36 . A distillate fuel according to  claim 34 , wherein the fuel conforms to at least one specification for a diesel fuel and has a cetane index greater than 65.  
   
   
       37 . A distillate fuel according to  claim 34 , wherein the fuel conforms to at least one specification for a jet fuel and has a passing rating in ASTM D3241 at 260° C. for 2.5 hours.  
   
   
       38 - 41 . (canceled)