Low toxicity fischer-tropsch derived fuel and process for making same

Abstract

A method for preparing low toxicity Fischer-Tropsch fuels suitable for use in a diesel engine and Fischer-Tropsch derived fuel compositions having low toxicity suitable for use in diesel engines characterized by a boiling range distribution wherein the 5 weight percent point is at a temperature of 570 degrees F. or less and the 95 weight percent point is at or above a temperature of 680 degrees F.; a kinematic viscosity at 40 degrees C. of less than 5.5 cSt; and a cloud point of less than −18 degrees C.

1 . A liquid transportation fuel suitable for use in a diesel engine which comprises a Fischer-Tropsch derived composition characterized by a boiling range distribution when measured by ASTM D2887 or its equivalent wherein the 5 weight percent point is at a temperature of 570 degrees F. or less and the 95 weight percent point is at or above a temperature of 730 degrees F.; a mid boiling point of 665 degrees F. or more; a kinematic viscosity at 40 degrees C. of less than 5.5 cSt; and a cloud point of less than −18 degrees C.  
   
   
       2 . The liquid transportation fuel of  claim 1  wherein the temperature of the 5 weight percent point of the boiling range distribution is above about 250 degrees F.  
   
   
       3 . The liquid transportation fuel of  claim 2  wherein the temperature of the 5 weight percent of the boiling range distribution is above about 300 degrees F.  
   
   
       4 . The liquid transportation fuel of  claim 3  wherein the temperature of the 5 weight percent of the boiling range distribution is above about 350 degrees F.  
   
   
       5 . (canceled)  
   
   
       6 . The liquid transportation fuel of  claim 1  wherein the temperature of the 95 weight percent point of the boiling range distribution is above about 850 degrees F.  
   
   
       7 . The liquid transportation fuel of  claim 1  wherein the viscosity is less than about 4.1 cSt at 40 degrees C.  
   
   
       8 . The liquid transportation fuel of  claim 1  wherein the cloud point is less than about −25 degrees C.  
   
   
       9 . The liquid transportation fuel of  claim 8  wherein the cloud point is less than about −30 degrees C.  
   
   
       10 . The liquid transportation fuel of  claim 1  wherein no more than 30 weight percent of the fuel boils between 500 degrees F. and 600 degrees F.  
   
   
       11 . The liquid transportation fuel of  claim 10  wherein no more than 25 weight percent of the fuel boils between 500 degrees F. and 600 degrees F.  
   
   
       12 . The liquid transportation fuel of  claim 11  wherein no more than 20 weight percent of the fuel boils between 500 degrees F. and 600 degrees F.  
   
   
       13 . The liquid transportation fuel of  claim 12  wherein no more than 15 weight percent of the fuel boils between 500 degrees F. and 600 degrees F.  
   
   
       14 . The liquid transportation fuel of  claim 13  wherein no more than 10 weight percent of the fuel boils between 500 degrees F. and 600 degrees F.  
   
   
       15 . The liquid transportation fuel of  claim 1  wherein the total sulfur content is less than 5 ppm.  
   
   
       16 . The liquid transportation fuel of  claim 1  characterized as displaying lower toxicity when contacted with a biological system than fuel compositions boiling within the range of conventional diesel.  
   
   
       17 - 38 . (canceled)  
   
   
       39 . A process for preparing a liquid transportation fuel suitable for use in a diesel engine which comprises: 
 (a) preparing a Fischer-Tropsch derived hydrocarbon composition characterized by a high paraffin content and a boiling range distribution when measured by ASTM D2887 or its equivalent wherein (i) the 5 weight percent point is at a temperature of 570 degrees F. or less, (ii) the 95 weight percent point is at or above a temperature of 730 degrees F., and (iii) the mid boiling point is at or above 665 degrees F.;    (b) improving the cold-flow properties of the Fischer-Tropsch derived hydrocarbon composition by reducing the paraffin content and increasing the isoparaffin content in a hydrocracking/hydroisomerization operation; and    (c) recovering a Fischer-Tropsch derived liquid transportation fuel suitable for use in a diesel engine characterized by a boiling range distribution when measured by ASTM D2887 or its equivalent wherein (i) the 5 weight percent point is at a temperature of 570 degrees F. or less, (ii) the 95 weight percent point is at or above a temperature of 730 degrees F., and (iii) the mid boiling point is at or above 665 degrees F., (iv) a kinematic viscosity at 40 degrees C. of less than 5.5 cST, and a cloud point of less than −18 degrees C.