SURFACTANTS

Abstract: There is described a method of determining the homogeneity of a fuel composition which comprises measuring the conductivity of the composition. There is also described a method of determining the homogeneity of a light fraction fuel wherein the conductivity is not less than 1 mS cm<-1> and of a heavy fraction fuel wherein the conductivity is not more than 1 mS cm<-1>. Fuel compositions possessing the conductivity values mentioned above are also described.

Description: SURFACTANTS This invention relates to novel method of determining the homogeneity of a fuel composition which comprises measuring the conductivity of the composition. Surfactants have long had utility as additives which can affect the performance of fuels such as gasoline and diesel. British Patent No 2217229 describes a solubilising compound as a fuel additive. In particular there is described a composition comprising; 48 parts by volume of an alcohol ethoxylate; 3-8 parts by volume of lauric diethanolamide; 3-8 parts by volume of oleic diethanolamide; and 1.5-4 parts by volume of a polyglycol ether such as ethoxylated oleic acid. Such compositions are useful as fuel additives and enable the solubilisation of water in fuels thus reducing its potential corrosive effect. However, the compositions are disadvantageous in that, inter alia, they require a high additive to fuel ratio. Furthermore, they do not address the problems of emissions of gases such as CO, CO 2 and NOX. International Patent Application No WO 98/17745 describes an alternative formulation which comprises, 25% w/w of a diethanolamide, 50% w/w of an ethoxylated alcohol, and 25% w/w of a fourteen carbon chain fatty acid with seven ethoxylate groups. WO '745 especially describes fuel compositions comprising, ter alia, an additive made up of a fatty acid diethanolamide, an alcohol ethoxylate and an ethoxylate of a fatty acid, the degree of ethoxylation being selected so that a long term stable fuel composition is formed and, in particular, wherein, by carefully selecting the degree of ethoxylation, a balanced molecule can be produced, such that the molecular weight ratios of each of the three components are substantially equivalent. Whilst such additives provide significant reductions in emissions and are useable at low concentrations, there is still a need for a fuel composition which is capable of reducing emissions whilst maintaining performance levels. It has long been known to improve the efficiency of fuel consumption and reduce emissions, by the incorporation of oxygenators, such as alcohol, into the fuel. Furthermore, in the case of diesel fuel, improvements can also be made in the cold starting of an engine. The modern day automobile is controlled by an air/fuel ratio computer which is linked to the in-flowing fuel line. In order to perform at the most efficient level the calculation continuously being performed by the computer is LAMBDA. LAMBDA is the theoretical stoichiometric amount of a fuel divided by the actual performing stoichiometry, therefore normally LAMBDA is 1 if the engine performance is at its optimum. The advent of oxygenated fuels has caused problems in performance as for example; the air fuel ratio of ethanol is approximately 9 and gasoline 13.7. This creates a problem for the modern day vehicle running on various fuels. The manufacturers have tried to overcome the problem by measuring the conductivity of the fuel on the way to combustion. However, to date it has not been possible to use relatively large amounts of oxygenators in fuels since such mixtures can lose their homogeneity and push the fuel towards its cloud point. Indeed, we have now surprisingly found that the essential factor in producing such improved fuel compositions is the determination of the fuel composition's cloud point. Thus certain additives may then be used to adjust the cloud point, enabling clear homogenous solutions of fuel and oxygenator mixtures to be achieved. For the sake of clarity, the cloud point as referred to herein is defined as the temperature at which a substance begins to separate from solution, e.g. when a petroleum oil is chilled under definite prescribed conditions. We have also found that a measure of when a fuel composition is at or near its cloud point is the conductivity of the fuel. For example, water has a conductivity of 100 mS cm "1 and an alcohol, e.g. ethanol, a conductivity of 20 to 30 mS cm "1 . Fuels, such as gasoline or diesel, being non-ionic, generally have a conductivity of substantially zero. Furthermore, we have found that a non-homogenous mixture of a fuel, such as gasoline or diesel, will have a relatively high conductivity reading, and as homogeneity is approached, the conductivity will reduce and will reach a minimum when the composition is a clear homogenous solution. Thus according to a first feature of the invention we provide a method of determining the homogeneity of a fuel composition which comprises measuring the conductivity of the composition. The conductivity may be measured at varying temperatures. However, we have found that measuring at substantially ambient temperature is preferred and particularly at 27.1 °C. Conductivity values given hereinafter generally relate to such values when measured at 27.1°C. Furthermore, since it is known that conductivity may vary with temperature, any conductivity values taken at differing temperatures should be calibrated as if measured at 27.1°C. We especially provide a method of determining the homogeneity of a fuel composition which comprises a fuel and an oxygenator. In a further aspect of the invention we provide a method of determining the conductivity in a composition as herein before described which is not less than 1 mS cm "1 for a light fraction hydrocarbon and not more than 1 mS cm "1 for a heavier fraction hydrocarbon. Thus according to a further feature of the invention we provide a fuel composition, comprising an oxygenator and a hydrocarbon fuel which together form a continuous homogenous phase. In particular we provide a fuel composition as herein before described wherein the oxygenator and the hydrocarbon medium are capable of forming a clear homogeneous continuous phase which exhibits an undetectable electrical conductivity measured at 27.1 °C. In practice the conductivity may vary depending on the hydrocarbon fuel. Hydrocarbon fuels which may be used in the course of the invention may be alkanes from C5 to C50. Particularly preferred fuels are gasoline, diesel, aviation fuel, etc. The conductivity should be not less than lmS cm " for a light fraction hydrocarbon and not more than lmS cm "1 for a heavier fraction hydrocarbon. In a particular preferred embodiment we provide a heavy fraction fuel, eg a diesel fuel, composition as herein before described which has a conductivity of not greater than 1 mS cm "1 i.e. from 0 to lmScm "1 . In another embodiment of the invention we provide a light fraction fuel, eg a gasoline fuel, composition as herein before described which has a conductivity of not less than 1 mS cm "1 , for example, from 1 to 2 mS cm "1 . Such compositions with conductivity levels as described may be achieved by inclusion of a modifier, although this is not deemed essential. The homogenous fuel mixture may preferentially comprise a mixture of a fuel, an oxygenator and surfactant additive. Preferred surfactant additives are those which have the relative molecular weights substantially balanced. Particularly preferred surfactant additives are those described in International Patent Application No WO98/17745 which is incorporated herein by reference. Oxygenators which may be used include water, ethers, furans and the like and especially alcohols. Suitable alcohols are alkyl Cl to 10 alcohols, preferably alkyl Cl to 5 alcohols. Particular alcohols which may be mentioned are methanol, ethanol and propanol, but a preferred alcohol is ethanol. When the oxygenator comprises an ether, dialkyl ethers are preferred. Any conventionally known dialkyl ethers used as fuel oxygenators may be included in the formulation. However, a preferred ether is methyl t-butyl ether (MTBE). The amount of oxygenator present may vary depending upon, mter alia, the fuel and the oxygenator. Preferably, the oxygenator is present as from 10 to 20% w/w of the composition, preferably from 12 to 18% w/w and especially 15% w/w. The storage characteristics of the fuel may be improved by the addition of a higher alcohol. By the term higher alcohol we generally mean an alkyl alcohol with more than 10 carbon atoms, e.g. alkyl CIO to 50 alcohols. One object of the present invention is to provide a permanent, clear fuel with a consistent conductivity reading which will, ter alia, increase the performance of the vehicle immensely. According to a further feature of the invention we also provide the use of a surfactant composition as hereinbefore described in the manufacture of a light fraction fuel composition having a conductivity of not less than lmScm "1 . We also provide the use of a surfactant composition as hereinbefore described in the manufacture of a heavy fraction fuel composition having a conductivity of not more than lmS cm "1 . We further provide the use of a heavy fraction fuel in the manufacture of a heavy fuel composition as hereinbefore described. We also provide the use of a light fraction fuel in the manufacture of a light fuel composition as hereinbefore described. An increase in performance by utilising the calculation and controlling conductivity is shown in the examples below. Major benefits are Nox reduction in gasoline + oxygenate vehicles and particulate reduction in diesel + oxygenate vehicles. The invention will now be described by way of example only. Example 1 In order to show the performance of the formula in a light fraction fuel utilising conductivity measurements to confirm homogenisation. Samples were set up of, 1. 400ml Unleaded gasoline + 80ml H20 + 50ml AAE7 2. 400ml Unleaded gasoline + 80ml H20 + 70ml AAE7 3. 400ml Unleaded gasoline + 80ml EtOH + 20ml AAE7 4. 400ml Unleaded gasoline + 80ml EtOH + 40ml AAE7 5. 400ml Unleaded gasoline 6. 400ml H 2 O 7. 400ml AAE7 Where AAE 7 is a surfactant composition comprising 50% w/w of an ethoxylated alcohol, said alcohol having a ratio of 3:1 of ethoxylate groups to Cl l alcohol; 25% w/w of a fatty acid diethanolamine and an ethoxylated fatty acid. More specifically, AAE 7 comprises: 50% w/w of an oil soluble primary alcohol ethoxylate (mean 2.75mols ethylene oxide: lmol of C9-C1 1 alcohol) available as NEODOL 91/2.5 25% w/w of lauric diethanolamide 25% w/w of an ethoxylated fatty acid with 7 ethoxylates per mol of fatty acid available as ATLAS G5507. The preparation of AAE 7 is described in International Patent Application No WO98/17745 which is incorporated herein by reference. A 30 litre tank was filled with water and maintained at a temperature of 27.1°C. The samples were placed in the tank and a temperature equilibrium was formed. An HI 8733 conductivity meter manufactured by Haana was used to measure conductivity of the above samples in mS/cm (micro Siemans/centimetre). Sample No Conductivity 1 0.0 2 0.0 3 0.5 4 1.5 5 0.0 6 127.0 In view of the zero conductivity reading on samples 1 and 2 further amounts of surfactant AAE 7 were added and conductivity measured. Sample No Composition Conductivity 8 1 + 30ml AAE 7 2.0 9 2 + 20ml AAE 7 1.9 As samples are heated the measurement of conductivity is more pronounced, but it was decided that to heat higher than 27.1°C may initiate the start of the lighter fractions boiling off. Example 2 In order to show the performance of the formula in a heavy fraction utilising conductivity measurements to confirm homogenisation. Samples were set up of, 10. 400ml Diesel + 80ml H 2 0 + 50ml AAE7 11. 400ml Diesel + 80ml H 2 0 + 70ml AAE7 12. 400ml Diesel + 80ml EtOH + 20ml AAE7 13. 400ml Diesel + 80ml EtOH + 40ml AAE7 14. 400ml Diesel 15. 400ml H 2 O 16. 400ml AAE7 A 30 litre tank was filled with water and maintained at a temperature of 28°C. Sample No Conductivity 10. 71.0 1 1. 80.3 12. 5.6 13. 6.1 14. 0.0 15. 131.0 16. 10.1 j In an analogous manner to the conduct of Example 1, because the conductivity measurements for samples 10 and 11 were significantly higher than expected, suggesting that a clear homogenous solution had not been achieved. Sample No Composition Conductivity 17 10 + 50ml AAE 7 0.0 18 1 1 + 50ml AAE 7 0.0 In examples 1 and 2 the H 2 O phases recorded were not in the first instant clear so further formula was added. The addition proved that conductivity is directly related to cloud points and the addition of ionic will reduce the dose of formula required.

Claims: CLAIMS 1. A method of determining the homogeneity of a fuel composition which comprises measuring the conductivity of the composition. 2. A method according to claim 1 wherein the fuel composition comprises at least a fuel component and an oxygenator 3. A method according to claim 2 which is capable of determining the homogeneity of the composition. 4. A method according to any one of the preceding claims wherein the fuel is a light fraction fuel and the conductivity is not less than 1 mS cm "1 . 5. A method according to any one of the preceding claims wherein the fuel is a heavy fraction fuel and the conductivity is not more than 1 mS cm "1 . 6. A fuel composition comprising at least an oxygenator and a hydrocarbon fuel which together form a continuous homogenous phase. 7. A fuel composition according to claim 6 characterised in that the fuel is a light fraction fuel and the conductivity is not less than 1 mS cm " . 8. A fuel composition according to claim 6 characterised in that the fuel is a heavy fraction fuel and the conductivity is not more than 1 mS cm "1 . 9. A fuel composition according to claim 6 which also comprises an alkylamidoethoxylate surfactant additive. 10. A fuel composition according to claim 6 wherein the fuel is a C5 to C50 hydrocarbon. 11. A fuel composition according to claim 6 comprising from 65-75% w/w of a C5 to C50 hydrocarbon fuel, from 10-15% w/w of an oxygenator and the remainder being an alkylamido ethoxylate. 12. A fuel composition according to claim 6 wherein the fuel is gasoline. 13. A fuel composition according to claim 12 comprising 75% w/w gasoline, 15% w/w of an oxygenator and 10% w/w alkylamidoethoxylate. 14. A fuel composition according to claim 6 wherein the fuel is diesel. 15. A fuel composition according to claim 14 comprising 69% w/w diesel, 14% w/w of an oxygenator and 17% w/w alkylamidoethoxylate. 16. A fuel composition according to claim 6 comprising a higher alcohol. 17. A fuel composition according to claim 16 wherein the higher alcohol is present in from 0.1 to lOppm of the composition. 18. A fuel composition according to claim 17 wherein the higher alcohol is cetyl alcohol. 19. A fuel composition according to claim 6 comprising an ionic modifier. 20. A fuel composition according to claim 19 wherein the modifier is present as less than 1% w/w of the composition. 21. A fuel composition according to claim 19 wherein the ionic modifier is an anionic modifier. 22. A fuel composition according to claim 21 wherein the anionic modifier is an ethoxylated lauryl sulphate. 23. The use of a surfactant composition comprising an alkanolamide, an alkoxylated alcohol and an alkoxylated fatty acid ester in the manufacture of a light fraction fuel composition having a conductivity of not less than 1 mS cm "1 . 24. The use of a surfactant composition comprising an alkanolamide, an alkoxylated alcohol and an alkoxylated fatty acid ester in the manufacture of a heavy fraction fuel composition having a conductivity is not more than 1 mS cm "1 . 25. The use of a heavy fraction fuel in the manufacture of a fuel composition according to claim 8. 26. The use of a light fraction fuel in the manufacture of a fuel composition according to claim 7. 27. A method or a fuel composition substantially as described with reference to the accompanying examples.

Inventors: HAZEL CLIFFORD JAMES, WILLIAMSON IAN VERNON, HAZEL, CLIFFORD, JAMES, WILLIAMSON, IAN, VERNON
Applicants: AAE HOLDINGS PLC, HAZEL CLIFFORD JAMES, WILLIAMSON IAN VERNON, HAZEL, CLIFFORD, JAMES, WILLIAMSON, IAN, VERNON
Application year: 2000
Main classification: G01N27
IPC codes: C10L1, G01N27, G01N33