Stable olefinic, low sulfur diesel fuels
The present invention relates to a stable blended diesel fuel comprising an olefinic diesel fuel blending stock. The olefinic diesel fuel blending stock of the invention comprises olefins in an amount of 2 to 80 weight percent, non-olefins in an amount of 20 to 98 weight percent wherein the non-olefins are substantially comprised of paraffins, oxygenates in an amount of at least 0.012 weight percent and sulfur in an amount of less than 1 ppm. To provide acceptable stability, the blended diesel fuel comprising the olefinic diesel fuel blending stock comprises a sulfur-free antioxidant. The blended diesel fuel comprising the olefinic diesel fuel blending stock and sulfur-free antioxidant added has a peroxide content of less than 5 ppm when stored at 60° C. for 4 weeks. The present invention also relates to processes for making the stable blended diesel fuel and olefinic diesel fuel blending stocks as defined above.
1. A process for making a diesel fuel blend component comprising:
a) converting at least a portion of a hydrocarbon asset to synthesis gas;
b) converting at least a portion of the synthesis gas to a hydrocarbon stream in a Fischer Tropsch process reactor;
c) isolating a diesel fraction from the hydrocarbon stream, wherein the diesel fuel fraction comprises olefins in an amount of 10 to 80 weight %; non-olefins in an amount of 20 to 90 weight %, wherein the non-olefins comprise paraffins in an amount of at least 50 weight %; oxygenates in an amount of at least 0.012 weight %; and sulfur in an amount of less than 1 ppm; and
d) adding at least one sulfur-free antioxidant to the diesel fuel fraction.
2. A process according to claim 1 , wherein the diesel fuel fraction comprises olefins in an amount of at least 25 weight %.
3. A process according to claim 1 , wherein the at least one sulfur-free antioxidant is selected from the group consisting of phenols, cyclic amines, and combinations thereof.
4. A process according to claim 1 , wherein the at least one sulfur-free antioxidant is a blend of a phenol and a cyclic amine.
5. A process for making a blended diesel fuel comprising:
a) converting at least a portion of a hydrocarbon asset to synthesis gas;
b) converting at least a portion of the synthesis gas to a hydrocarbon stream in a Fischer Tropsch reactor;
c) isolating a diesel fraction from the hydrocarbon stream, wherein the diesel fuel fraction comprises olefins in an amount of at 10 to 80 weight %; non-olefins in an amount of 20 to 90 weight %, wherein the non-olefins comprise paraffins in an amount of at least 50 weight %; oxygenates in an amount of at least 0.012 weight %;
d) mixing the Fischer Tropsch derived diesel fuel fraction with a diesel selected from the group consisting of a hydrocracked Fischer Tropsch derived diesel, a hydrotreated Fischer Tropsch diesel, a hydrocracked petroleum derived diesel, a hydrotreated petroleum diesel, and mixtures thereof to provide a blended diesel fuel; and
e) adding an effective amount of at least one sulfur-free antioxidant to the blended diesel,
wherein the blended diesel fuel comprises sulfur in an amount of less 1 ppm.
6. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is added in an amount of 5 to 500 ppm.
7. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is added in an amount of 20 to 100 ppm.
8. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is selected from the group consisting of phenols, cyclic amines, and combinations thereof.
9. A process according to claim 8 , wherein the at least one sulfur-free antioxidant is a cyclic amine having the following formula:
wherein:
A is a six-membered cycloalkyl or aryl ring,
R 1 , R 2 , R 3 , and R 4 are independently H or alkyl; and
x is 1 or 2.
10. A process according to claim 8 , wherein the at least one sulfur-free antioxidant is an alkylphenol having the formula:
wherein R 5 and R 6 are independently H or alkyl and n is 1 or 2.
11. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is selected from the group consisting of 4,4′-methylene-bis(2,6-di-tert-butylphenol), 4,4′-bis(2,6-di-tert-butylphenol), 4,4′-bis(2-methyl-6-tert-butylphenol), 2,2′-methylene-bis(4-methyl-6-tert-butyl-phenol), 4,4′-butylidene-bis(3-methyl-6-tert-butylphenol), 4,4′-isopropylidene-bis(2,6-di-tert-butylphenol), 2,2′-methylene-bis(4-methyl-6-nonylphenol), 2,2′-isobutylidene-bis(4,6-dimethylphenol), 2,2′-methylene-bis(4-methyl-6-cyclohexylphenol), 2,6-di-tertbutyl-4-methylphenol, 2,6-di-tertbutyl-4-ethylphenol, 2,4-dimethyl-6-tert-butyl-phenol, 2,6-di-tert-butyl-dimethylamino-p-cresol, 2,6-di-tert-4-(N,N′-dimethyl-aminomethylphenol), bis(3,5-di-tert-butyl-4-hydroxybenzyl), alkylated diphenylamine, phenyl-alpha-naphthylamine, alkylated-alpha-naphthylamine, and combinations thereof.
12. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is selected from the group consisting of dimethylcyclohexylamine, N,N′-di-sec-butyl-p-phenylenediamine, 2,6-di-tert-butylphenol, 4-tert-butylphenol, 2-tert-butylphenol, 2,4,6-tri-tert-butylphenol, and combinations thereof.
13. A process according to claim 5 , wherein the at least one sulfur-free antioxidant is a blend of a phenol and a cyclic amine.
14. A process according to claim 5 , wherein the blended diesel fuel has a peroxide content of less than 5 ppm after storage at 60° C. for four weeks.
15. A process according to claim 5 , wherein the blended diesel fuel has a reflectance as measured by ASTM D6468 of greater than 65% when measured at 150° C. for 90 minutes.
16. A process according to claim 5 , wherein the blended diesel fuel has a reflectance as measured by ASTM D6468 of greater than 80% when measured at 150° C. for 90 minutes and a peroxide content of less than 4 ppm after storage at 60° C. for four weeks.
17. A process according to claim 5 , wherein the blended diesel fuel has a reflectance as measured by ASTM D6468 of greater than 90% when measured at 150° C. for 90 minutes and a peroxide content of less than 1 ppm after storage at 60° C. for four weeks.
18. A process according to claim 5 , further comprising the step of adding an effective amount of a lubricity additive to provide an ASTM D6079 wear scar of 450 micros or less.
19. A process according to claim 18 , wherein the lubricity additive is an ester.
20. A process for making a blended diesel fuel comprising:
a) providing a Fischer Tropsch derived diesel fuel fraction comprising olefins in an amount of at 10 to 80 weight %; non-olefins in an amount of 20 to 90 weight %, wherein the non-olefins comprise paraffins in an amount of at least 50 weight %; oxygenates in an amount of at least 0.012 weight %;
b) mixing the Fischer Tropsch derived diesel fuel fraction with a diesel selected from the group consisting of a hydrocracked Fischer Tropsch derived diesel, a hydrotreated Fischer Tropsch diesel, a hydrocracked petroleum derived diesel, a hydrotreated petroleum diesel, and mixtures thereof to provide a blended diesel fuel; and
c) adding an effective amount of at least one sulfur-free antioxidant to the blended diesel,
wherein the blended diesel fuel comprises sulfur in an amount of less 1 ppm.
21. A process according to claim 20 , wherein the at least one sulfur-free antioxidant is added in an amount of 5 to 500 ppm.
22. A process according to claim 20 , wherein the blended diesel fuel has a reflectance as measured by ASTM D6468 of greater than 80% when measured at 150° C. for 90 minutes and a peroxide content of less than 4 ppm after storage at 60° C. for four weeks.