Gasoline composition

Abstract

This invention relates to a fuel composition comprising (i) a low sulphur fuel having a sulphur content of less than 30 ppm, a bromine number of less than 10 and an ultraviolet absorbance at 319 nm is below 0.15 and (ii) an effective amount of an ashless friction reducing additive which is a fatty acid having 10-30 carbon atoms or a derivative thereof. The fuel of the specified characteristics shown improved response to the friction reducing additive in respect of its lubricity performance.

Description

[0001] This invention relates to low sulphur gasoline compositions which have improved response to friction reducing additives.

[0002] Fuels such as gasolines and diesels are used rather widely in automotive transport and for providing power for heavy duty equipment, especially diesels due to their high fuel economy. However, one of the problems when such fuels are burned in internal combustion engines is their low lubricity. This reduction in lubricity arises because as the sulphur content in the fuel is reduced eg by hydrodesulphurisation, this process also incidentally removes the lubricity providing polar or friction reducing molecules such as eg the nitrogenous compounds present in such fuels. A prior published SAE Paper No. 962010 by Wei Dan Ping et al entitled “Comparison of the Lubricity of Gasoline and Diesel Fuels” (1996) describes the effects of various additives on such fuels including low sulphur fuels. Whilst efforts hitherto have been devoted to the addition of such friction reducing nitrogenous compounds into the fuels after hydrodesulphurisation to restore the lubricity of the fuel, little attention has been paid to the nature of the fuel itself in order to improve the efficiency of such fuels.

[0003] Prior published GB-A-2306246 and GB-A-2307247 relate to the use of carboxylic acid derivatives as an additive for improving the lubricity of low sulphur-content fuels which are primarily middle distillate fuels such as eg diesel, jet and biodiesel fuels. However, there is no mention of gasolines or fuels having a sulphur content of less than 30 ppm in these documents.

[0004] Similarly, EP-A-0860494, EP-A-0739970 and EP-A-0635558 relate to low sulphur diesel, gas oils and gas oils (diesel fuels) respectively containing esters derived by transesterification of vegetable oils, glycerol/fatty acid esters and lower alkyl esters of a mixture of saturated and unsaturated fatty acids derived from oleaginous seeds respectively as a lubricity improving agent. In each case there is no mention of low sulphur gasolines, especially gasolines having a sulphur content of <30 ppm.

[0005] WO99/00467 describes a fuel composition of improved lubricity comprising a spark ignition fuel and an alkanolamide of a fatty acid or a modified fatty acid having a maximum sulphur content of 0.05% based on mass. However, no gasolines are mentioned and all of the examples relate to diesels, especially Swedish Class I low sulphur diesel fuel. There is also no reference to the bromine number or UV absorbance of the fuels tested or claimed.

[0006] It has now been found that the efficacy of the friction reducing additives can be significantly improved by mixing the same with fuels of specific, predetermined characteristics.

[0007] Accordingly, the present invention is a composition comprising (i) a low sulphur gasoline having a sulphur content of less than 30 ppm, a bromine number of less than about 10 and an ultraviolet absorbance at 319 nm below 0.15 and (ii) an effective amount of an ashless friction reducing additive which is a fatty acid having 10-30 carbon atoms or a derivative thereof.

[0008] The gasoline should have a bromine number (which is related to the amount of olefins in the fuel) below 10, suitably below 5 and preferably below 4.5. Furthermore, the gasoline should have a sulphur content below 30 ppm, suitably below 20 ppm and preferably below 10 ppm. Again the UV absorbance of the fuel at 319 nm should be below 0.1, suitably below 0.07 and preferably below 0.05.

[0009] The ashless friction reducing additive in the composition is suitably a liquid at room temperature and pressure and is selected from C10-C30 fatty acids, preferably a C10-C24 fatty acid, or a derivative thereof and mixtures thereof. Such ashless friction reducing additives are suitably derived from naturally occurring fats and oils and the preferred derivatives are suitably selected from the alkylamine salts, alkyl amides and alkyl esters of such acids and oligomers thereof. An example of an alkyl amine carboxylate salt is n-butylamine oleate or a derivative thereof and an example of a naturally occurring fatty acid is a substance comprising a fatty acid, a tall oil fatty acid or derivatives thereof.

[0010] n-Butylamine oleate has the formula:

CH3—(CH2)7—CH:CH—(CH2)7—C(O)O−+NH3C4H9

[0011] One such n-butylamine oleate is commercially sold as a friction modifier as RS124 by Bitrez Ltd.

[0012] The substance comprising fatty acids may be either 100% fatty acids, or substantially 100% fatty acids, or may be a mixture of fatty acids and/or tall oil acids or derivatives thereof. Such a mixture suitably contains at least 30% w/w, preferably at least 50% w/w of fatty acids. An example of a suitable commercially available substance containing fatty acids is TOLAD® 9103 (ex Baker-Petrolite Ltd).

[0013] The friction reducing additive is used in an amount sufficient to provide effective lubricity to the composition. The friction reducing additive is suitably used in an amount of less than 1000 mg per kilogram of base fuel in the composition, preferably from 1 to 500 mg and more preferably from about 5 to 100 mg per kg of base fuel in the composition. It has been found that a gasoline with these characteristics is much more responsive to the amount of the ashless friction reducing agent specified above added than conventional fuels which do not possess these characteristics. A typical example of such a gasoline is the so called “Rotterdam gasoline” which suitably has a final boiling point below 200° C., preferably about 185° C. The ashless friction reducing additive may be part of an additive concentrate comprising a number of additives. In the additive concentrate, the amount of the friction reducing additive is suitably from 0.2-25% w/w, preferably from 0.5-20% w/w and more preferably from 3 to 15% w/w. On the basis of the total concentrate, the treat level of the friction reducing additive in the gasoline is suitably from 4-200 ppm, preferably from 10-100 ppm and more preferably from 25-75 ppm.

[0014] The present invention is further illustrated with reference to the following Examples and comparative tests:

EXAMPLES

[0015] The following fuels with varying degrees of bromine numbers, sulphur content and UV absorbance at 319 nm were tested for their responsiveness to a lubricity additive. Of these, both the Rotterdam and the Neste 95UL base gasolines show comparable sulphur contents, yet the Rotterdam fuel (which has a final boiling point of 186.2° C.) is more responsive to lubricity additive. This responsiveness, as measured by the percentage reduction in friction relative to base fuel (Table 2) is linked to the fuel's substantially lower bromine number and UV absorption at 319 nm. (Table 1) (Note: the measure of UV absorbance and bromine number are both dimensionless quantities). 1 TABLE 1 FUEL & SOURCE BROMINE NO. % SULPHUR BY WT UVA (319 nm) Fawley (A)* 37.72 0.04 0.398 Neste 95UL* 21.7 0.0027 0.323 Rotterdam 4.17 0.0028 0.038 Fawley (B)* 16.11 0.01 0.172 Fawley (C)* 13.28 0.02 0.567 *Indicates a test fuel not according to the invention.

[0016] The above fuels were tested at various treat rates to determine the change in coefficient of friction and the mean friction values and the results are tabulated in Tables 2 and 3 below: 2 TABLE 2 Treat Rate Base Fuel Additive ml/1000 litres Mean FC &Dgr;FC % &Dgr;FC Fawley (A) None 0 0.224 Fawley (B) n-BAO 12.5 0.154 0.071 31.5 Fawley (C) Tolad ® 9103 12.5 0.145 0.079 35.3 Neste 95 UL None 0 0.225 Neste 95 UL n-BAO 12.5 0.152 0.073 32.5 Neste 95 UL Tolad ® 9103 12.5 0.153 0.072 32.1 Rotterdam# None 0 0.439 Rotterdam# n-BAO 12.5 0.157 0.283 64.4 Rotterdam# Tolad ® 9103 12.5 0.152 0.287 65.5 Fawley (B) None 0 0.304 Fawley (B) n-BAO 12.5 0.158 0.146 47.9 Fawley (B) Tolad ® 9103 12.5 0.214 0.090 29.7 Fawley (C) None 0* 0.315 Fawley (C) n-BAO 12.5* 0.204 0.111 35.2 Fawley (C) Tolad ® 9103 12.5* 0.218 0.097 30.8 Mean FC = mean friction coefficient &Dgr;FC = Mean FC (base fuel) − Mean FC (additised fuel) % &Dgr;FC = [Mean FC (base fuel) − Mean FC (additised fuel)] × 100/Mean FC (base fuel) *These are by weight ie mg/Kg #Fuels according to the invention.

[0017] 3 TABLE 3 Treat Rate Mean Friction % &Dgr;Friction Base Fuel Additive mg/Kg Coefficient Coefficient Fawley (C) None 0 0.315 Fawley (C) n-BAO 12.5 0.204 35.2 Fawley (C) n-BAO 25 0.146 53.6 Fawley (C) n-BAO 50 0.132 58.1 Fawley (C) n-BAO 100 0.118 62.5 Fawley (C) None 0 0.315 Fawley (C) Tolad ® 9103 12.5 0.218 30.8 Fawley (C) Tolad ® 9103 25 0.174 44.8 Fawley (C) Tolad ® 9103 50 0.149 52.7 Fawley (C) Tolad ® 9103 100 0.137 56.5 n-BAO - n-butylamine oleate; Tolad ® FC-Friction Coefficient

Claims

1. A composition comprising (i) a low sulphur gasoline having a sulphur content of less than 30 ppm, a bromine number of less than 10 and an ultraviolet absorbance at 319 nm below 0.15 and (ii) less than 1000 mg per kg of the low sulphur gasoline of an ashless friction reducing additive which is a fatty acid having 10-30 carbon atoms or a derivative thereof selected from the alkylamine salts, alkylamides and alkylesters of such acids and oligomers thereof.

2. A composition according to claim 1 wherein the gasoline has a bromine number below 5 ppm.

3. A composition according to any one of the preceding claims wherein the gasoline has a sulphur content below 20 ppm.

4. A composition according to any one of the preceding claims wherein the gasoline has an UV absorbance at 319 nm of below 0.07.

5. A composition according to any one of the preceding claims wherein the fatty acid is derived from naturally occurring fats and oils and oligomers thereof.

6. A composition according to any one of the preceding claims wherein the ashless friction reducing additive is an alkylamine salts of a fatty acid derived from naturally occurring fats and oils and oligomers thereof.

7. A composition according to any one of claims 1-4 wherein the ashless friction reducing additive is an alkylamide of a fatty acid derived from naturally occurring fats and oils and oligomers thereof.

8. A composition according to any one of the preceding claims 1-4 wherein the ashless friction reducing additive is an alkylester of a fatty acid derived from naturally occurring fats and oils and oligomers thereof.

9. A composition according to claim 6 wherein the alkylamine carboxylate salt is n-butylamine oleate as shown in the formula below or a derivative thereof

CH3—(CH2)7—CH:CH—(CH2)7—C(O)O−+NH3C4H9

10. A composition according to any one of claims 1-4 wherein the long chain fatty acid or a derivative thereof is a substance comprising tall oil acid or derivatives thereof.

11. A composition according to claim 10 wherein the substance containing fatty acid is TOLAD® 9103 (ex Petrolite Ltd).

12. A composition according to any one of the preceding claims wherein the treat level of the friction reducing additive is from 1-500 mg per kg of gasoline.

13. A composition according to any one of the preceding claims wherein the treat level of the friction reducing additive is from 4-200 ppm based on the gasoline.

14. A composition according to any one of the preceding claims wherein the treat level of the friction reducing additive is from 10-100 ppm based on the gasoline.

15. A composition according to any one of the preceding claims wherein the treat level of the friction reducing additive is from 25-75 ppm based on the gasoline.