Systems and methods of improving diesel fuel performance in cold climates
Embodiments of the present invention are directed toward systems and methods of providing a low-emissions diesel fuel for use in cold climates. Such fuels may be prepared by a Fischer-Tropsch process and include a pour point depressant. Furthermore, the fuel is used in conjunction with a heated fuel delivery system so that low cloud points are not necessary. Fuels prepared according to embodiments of the present invention may be produced in higher yields than otherwise possible because a higher paraffin wax content can be tolerated, thus obviating the need to remove or exclude the wax. These fuels are characterized by a sulfur content less than 1 ppm, a cetane number greater than 60, an aromatics content less than 1 wt %, and a difference between the cloud and pour points that is greater than about 5° C. The present fuel may be prepared by a Fischer-Tropsch synthesis from any number of carbon-containing sources such natural gas, coal, petroleum products, and combinations thereof.
1. A Fischer-Tropsch derived diesel fuel having a cloud point and a pour point, the fuel comprising:
a. a cetane number greater than about 60;
b. a pour point depressant; and
c. a flash point for a diesel fuel as provided by ASTM D-975,
wherein the difference between the cloud point and the pour point of the fuel is greater than about 5° C. and wherein the fuel is formulated such that it comprises a 95% point as measured by ASTM D-2887 in excess of 625° F.
2. The diesel fuel of claim 1 , wherein the difference between the cloud point and the pour point of the fuel is greater than about 10° C.
3. The diesel fuel of claim 1 , wherein the difference between the cloud point and the pour point of the fuel is greater than about 15° C.
4. The diesel fuel of claim 1 , wherein the cetane number of the fuel is greater than about 65.
5. The diesel fuel of claim 3 , wherein the cetane number of the fuel is greater than about 65.
6. The diesel fuel of claim 1 , wherein the fuel is formulated such that it comprises a 95% point as measured by ASTM D-2887 in excess of 650° F.
7. The diesel fuel of claim 1 , wherein the fuel is formulated such that it comprises a 95% point as measured by ASTM D-2887 in excess of 690° F.
8. The diesel fuel of claim 1 , wherein the cloud point of the fuel is less than about 0° C.
9. The diesel fuel of claim 1 , wherein the cloud point of the fuel is less than about −15° C.
10. The diesel fuel of claim 1 , wherein the cloud point of the fuel is less than about −25° C.
11. The diesel fuel of claim 1 , wherein the pour point depressant comprises a linear component and a branched component.
12. The diesel fuel of claim 11 , wherein the branched component is selected from the group consisting of fumarates, bridged alkylaromatics, acrylates, and acetates.
13. The diesel fuel of claim 1 , wherein the amount of the pour point depressant in the diesel fuel is greater than about 10 mg/kg.
14. The diesel fuel of claim 1 , wherein the amount of the pour point depressant in the diesel fuel is greater than about 50 mg/kg and less than about 1000 mg/kg.
15. The diesel fuel of claim 1 , wherein the amount of the pour point depressant in the diesel fuel is greater than about 100 mg/kg and less than about 500 mg/kg.
16. The diesel fuel of claim 1 , wherein the paraffin wax content of the fuel is substantially in solution.
17. The diesel fuel of claim 1 , wherein the temperature of the fuel is above the fuel's cloud point.
18. The diesel fuel of claim 1 , wherein the fuel has a sulfur content less than about 1 ppm, and an aromatics content of less than about 1 percent by weight.
19. The diesel fuel of claim 1 , wherein the flash point is greater than 52° C.
20. The diesel fuel of claim 1 , wherein the flash point is ≧58° C.