LUBRICITY ADDITIVE FOR TRANSPORTATION FUELS

Abstract

Oxidized disulfide oil (ODSO) compounds, derived from by-product disulfide oil (DSO) compounds from the MEROX process, are effective as lubricity additives for transportation fuels. Significant increases in lubricity of ultra-low sulfur fuels as measured by the WSD test were observed with addition of ODSO compounds in the range of from 0.1 ppmw to 10 ppmw. This use of ODSO compounds as lubricity additives converts an otherwise DSO waste oil product into a valuable commodity that has utility in improving lubricity properties of transportation fuels.

Claims

1. A lubricity additive for improving the lubricity of transportation fuel that is an oxidized disulfide oil (ODSO) selected from the group consisting of (RSOSR), (RSOOSR), (RSOOSOR), (RSOOSOOR), (RSOSOR), (RSOSOOOH), (RSOOSOOOH), (RSOSOOH), and (RSOOSOOH), and mixtures thereof, where R and R are alkyl groups comprising 1-10 carbon atoms.

2. The lubricity additive of claim 1, in which the number of carbon atoms in the lubricity additive compounds is in the range of from 1 to 20.

3. The lubricity additive of claim 1, in which the number of carbon atoms in the lubricity additive compounds is in the range of from 2 to 20.

5. The lubricity additive of claim 1, wherein the additive has at least 1 oxygen atom.

6. The lubricity additive of claim 1, wherein the additive has at least 3 oxygen atoms.

7. The lubricity additive of claim 6, wherein the alkyl groups have carbon numbers in the range of from 1 to 10.

8. A lubricity additive for a transportation fuel that is an ODSO produced by oxidizing a disulfide oil derived from the catalytic oxidation of mercaptans in a petroleum feedstream.

9. The lubricity additive of claim 1, wherein the WSD value for the transportation fuel as determined by ASTM D-6079 is reduced by at least 60 m.

10. A transportation fuel that contains one or more of the lubricity additives of claim 1.

11. The transportation fuel of claim 10 which is diesel fuel.

12. A method of improving the lubricity of an ultra-low sulfur gasoline or diesel transportation fuel that comprises adding to the fuel at least one of the compounds of claim 1.

13. The method of claim 12 in which the mixture includes ODSO compounds selected from the group consisting of (RSOSR), (RSOOSR), (RSOOSOR), (RSOOSOOR), (RSOSOR), (RSOSOOOH), (RSOOSOOOH), (RSOSOOH), and (RSOOSOOH).

14. The method of claim 12 or 13 in which the transportation fuel is diesel.

15. The method of claim 12, wherein the additive is present in fuel in the range of from 0.1 to 10 ppmw of the fuel.

16. The method of claim 12, wherein the fuel contains at least 1 ppmw of the additive.

17. The method of claim 12, wherein the lubricity additive is mixed with a fuel having a sulfur concentration that is not greater than 150 ppmw.

18. A transportation fuel composition that includes a lubricity additive that is a mixture of ODSO compounds that comprises two or more of the following: (RSOSR), (RSOOSR), (RSOOSOR), (RSOOSOOR), (RSOSOR), (RSOSOOOH), (RSOOSOOOH), (RSOSOOH), and (RSOOSOOH).

19. The composition of claim 18, where the transportation fuel is a low or ultra-low sulfur diesel.

20. The method of claim 13 in which the transportation fuel is diesel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The process of this disclosure will be described in more detail below and with reference to the attached figures in which:

[0035] FIG. 1 is a graph illustrating the effect of various types of commercial additives of the prior art on the lubricity of an ultra-low sulfur diesel fuel;

[0036] FIG. 2 is a graph illustrating the lubricity of hydrotreated diesels of the prior art as a function of the level of hydrodesulfurization, and

[0037] FIG. 3 is a graph illustrating the lubricity of hydrotreated diesel-range fuels as a function of sulfur concentration.

DETAILED DESCRIPTION OF THE INVENTION

[0038] The lubricity of transportation fuels such as diesel and gasoline are selectively improved by the addition of specified oxidized disulfide oil (ODSO) compounds. In certain embodiments, the transportation fuel has a sulfur level less than 150 ppmw, in preferred embodiments a sulfur level in the range of from 1 to 150 ppmw, and in more preferred embodiments a sulfur level in the range of from 1-5 ppmw. Compounds found to have utility as lubricity additives can advantageously be produced by the oxidation of disulfide oil (DSO) compounds recovered as a low value by-product of the catalyzed mercaptan oxidation of a hydrocarbon feedstock, commonly referred to as the MEROX process.

[0039] The lubricity additive can be mixed directly with the transportation fuel, or doped with a portion of the fuel for convenience and to facilitate its mixing, to provide a fuel with improved lubricity properties.

[0040] The lubricity additive can be pre-mixed with n-hexane or other solvent that is compatible with the fuel in order to facilitate its addition to, and uniform blending with the fuel to obtain the desired concentration of the additive in fuel.

[0041] In a preferred embodiment, the number of carbon atoms in the ODSO lubricity additive is in the range of from 2 to 20. In certain embodiments, the number of carbon atoms in the ODSO lubricity additive is in the range of from 1 to 20, 1 to 10, or 2 to 10.

[0042] The ODSO lubricity additives of the present disclosure are soluble in oil at the working concentrations. The water soluble ODSO compounds have a boiling point in the range of from 20 C. to 650 C. The water insoluble ODSO compounds have a boiling point in the range of from 20 C. to 250 C. In preferred embodiments, the lubricity additives contain alkyl groups with carbon numbers in the range of from 1 to 20. In certain embodiments, the lubricity additives contain alkyl groups with carbon numbers in the range of from 1 to 10. In preferred embodiments, each alkyl group has a carbon number in the range of from 1 to 3.

EXAMPLES

[0043] The ASTM D6079 HFRR test method for diesel fuel lubricity was applied in the following examples to determine the lubricity of the fuel and additive mixture.

Example 1

[0044] Two gas oils derived from light and medium crude oils were used as feedstocks to test the lubricity improvements with the additives. The gas oils were first hydrotreated in a pilot plant using various methods and conditions known to those skilled in the art to obtain ultra-low sulfur diesel. The composition and properties of the gas oils before hydrotreating are shown in Table 3.

TABLE-US-00002 TABLE 3 Composition and Properties of Gas oils before Hydrotreating Diesel Unit Diesel 1 Diesel 2 API Gravity 0.8222 0.8432 sulfur ppmw 8901 13090 nitrogen ppmw 49 71 Simulated Distillation Initial B.P./5/10 W % C. 84/131/160 141/188/204 30/50 W % C. 217/262 249/286 70/90 W % C. 305/351 319/351 95 W %/Final B.P. C. 367/391 364/400

[0045] The gas oils were hydrotreated at a hydrogen partial pressure of 33 bars, LHSV of 1.5 h.sup.1 and at a temperature in the range of from 320 C. to 355 C. The product gas oils contained sulfur in the range of from 5-777 ppmw.

[0046] FIG. 2 shows the effect on the lubricity of the diesel fuels tested as a function of the percent completion of hydrodesulfurization measured along the x-axis. It is clear that the lubricity level of the fuel decreased as the percent completion of the hydrodesulfurization process approached the theoretical value of 100%. It is clear that there were unacceptable lubricity characteristics (a WSD of more than 460 m) in the fuels with higher levels of completion of hydrodesulfurization.

[0047] FIG. 3 illustrates the lubricity of the hydrotreated diesels as a function of sulfur content. For untreated fuel samples, Diesel I (.square-solid.) and Diesel 2(.diamond-solid.), respectively, the diesel lubricity decreased with reduced sulfur level in the diesels, resulting in an increase in WSD levels. It is clear that there were unacceptable lubricity characteristics, i.e., a WSD of more than 460 m, in the fuels with sulfur levels of less than 150 ppm by weight for untreated diesels. For diesels treated with the lubricity additive, (.circle-solid.) and (.box-tangle-solidup.) in FIG. 3, there is an improvement in lubricity and that the fuel and additive mixture has acceptable lubricity characteristics, i.e., a WSD of less than 460 m.

[0048] Table 4 shows the compositions and properties of the two hydrotreated diesel samples with the lowest sulfur amounts, i.e., 6 and 21 ppmw, respectively.

TABLE-US-00003 TABLE 4 Composition and Properties of Gas oil samples after Hydrotreating Hydrotreated Hydrotreated Diesel Unit Diesel 1 Diesel 2 API Gravity 0.8139 0.8274 sulfur ppmw 6 21 nitrogen ppmw 3 4 Simulated Distillation Initial B.P./5/10W % C. 86/139/163 135/187/202 30/50 W % C. 215/256 245/278 70/90 W % C. 297/344 311/348 95 W %/Final B.P. C. 362/392 361/397

[0049] Each of the diesel samples were mixed with the ODSO additive compounds at a concentration in the range of from 1.0 ppmw to 5.0 ppmw. Table 5 shows the effect of the ODSO additive on the lubricity of the diesels.

TABLE-US-00004 TABLE 5 Lubricity of diesels mixed with ODSO additive Diesel ODSO lubricity WSD, WSD Delta, Source additive, ppmw m Improvements, m Diesel 1 0.0 532 Diesel 1 1.0 375 157 Diesel 1 4.0 436 96 Diesel 1 5.0 417 115 Diesel 2 0.0 504 Diesel 2 1.0 390 114 Diesel 2 4.0 426 78 Diesel 2 5.0 373 131

[0050] It is clear from Table 5 that the presence of ODSO additives in the fuels tested improved their respective lubricities. As indicated by the data, no direct correlation was observed between the degree of improved lubricity and the concentration of the ODSO additive. Even at the lower concentrations of 1 ppmw of additive, the lubricity of the fuel was improved.

[0051] The methods and compositions of the present invention have been described in detail above and in the attached drawings; however, modifications will be apparent to those of ordinary skill in the art from this description and the scope of protection for the invention is to be determined by the claims that follow.