HK1172050B - Protection of liquid fuels - Google Patents

Description

Protection of liquid fuels

Technical Field

The present invention relates to the protection of liquid fuels, such as those typically used in engines used to power vehicles, such as, but not limited to, turbine engine type aircraft. In particular, the present invention relates to the protection of such liquid fuels from the deleterious effects of water-borne contamination, such as on engines, due to the presence of water as a separate phase in the fuel. More importantly, the present invention provides protection of the liquid fuel from ice formation, thereby reducing the likelihood of ice debris (ice slug) being drawn into the engine.

The invention also relates to compositions, methods of their preparation and use, and concentrates. More particularly, but not exclusively, the invention relates to water-in-oil microemulsions suitable for use as fuel for turbine engine aircraft, for example, and their preparation.

In summary, the present invention relates to clear aqueous compositions comprising at least 99% by weight of a liquid fuel, and concentrates useful for preparing such compositions, and their preparation, which compositions are useful as fuels for turbine engine aircraft, such as water-in-oil emulsions, wherein the average droplet size of the aqueous phase in the oil phase is no greater than 0.25 μm, preferably no greater than 0.1 μm.

Background

Jet Fuel (JF) is often contaminated in the fuel tanks of turbine engine aircraft with small amounts of free water from condensation resulting from temperature changes due to altitude changes. On the ground, the fuel/tank temperature may be-18 ℃ to +40 ℃, while in flight it is typically-22 ℃ to-39 ℃.

After a number of temperature change cycles, for example after a number of flights, the condensation of water vapour may lead to an accumulation of water within the fuel tank, which may exist as a separate phase or free water within the fuel. If the free water is allowed to collect and freeze in the fuel tank, it may form ice debris (ice particles of sufficient size so that they may be trapped in the fuel filtration system) that may potentially be detrimental to the function of the aircraft engine. In fact, it is believed that boeing 777 aircraft lost enough power to cause an emergency landing in Heathrow 1 month in 2008 (AAIB phase report No2G-YMMM) due to ice formation reducing fuel flow from the fuel tank to the engine.

Currently, as an alternative to the use of fuel tank heaters, materials such as diethylene glycol monomethyl ether (DiEGME) are mixed with aviation fuel to prevent ice formation in the fuel. When DiEGME is approximately equally miscible in water and fuel at temperatures above freezing, careful monitoring must always be adhered to during mixing to ensure an initially homogeneous fuel. However, no matter how carefully mixed, DiEGME tends to preferentially concentrate in the aqueous phase at temperatures significantly below freezing. Thus, insufficient DiEGME in the fuel phase may result in the formation of a separate water phase (water and DiEGME) in the fuel due to the disproportionate distribution of DiEGME in water and fuel at low temperatures. The presence of DiEGME in the aqueous phase will prevent some of the water in this phase from turning into ice. However, an unusual property of the DiEGME/water mixture is that it forms a gel-like mass at low temperatures: the gelatinous mass is commonly referred to in the aviation industry as "apple jelly". Several aviation accidents have been attributed to the formation of this "apple jelly" material in the aircraft fuel tank by the U.S. federal aviation administration.

U.S. Pat. No. 3, 2886423(Vitalis et al) discloses the incorporation of certain acylamidoalkylglycine betaines into liquid hydrocarbon fuels such as aviation fuels to improve low temperature properties. Although acylamidoalkylglycine betaines are shown to reduce the temperature at which haze or cloudiness occurs in jet fuels, haze or cloudiness is disclosed as being caused by the appearance of small ice crystals or wax crystals. The visual appearance of these small ice or wax crystals indicates that a significant proportion of the crystals themselves, or the particles of agglomerated crystals, have a particle size of at least 1 μm or more. Aviation fuels containing dispersions of ice particles above 1 μm in size tend to exhibit instability in which particles at this size can settle out of suspension and/or agglomerate with other ice particles, leading to the potential formation of ice shavings.

It is an object of the present invention to reduce or eliminate the formation of ice chips and apple jelly in fuel within the fuel tanks of turbine engine aircraft.

The use of water as an additive in fuel oils to reduce the emission of pollutants and to facilitate the incorporation of other additives of beneficial properties has been known for many years. Water has also been known for many years as an additive in lubricating oils to improve the cooling properties of, for example, cutting oils. Water is incorporated into fuels and lubricating oils in the form of water-in-oil emulsions.

Water-in-oil emulsions formed with large water droplet sizes (greater than 1 μm) tend to have a milky appearance. These emulsions require a variety of secondary additives (such as corrosion inhibitors and biocides) to overcome the problems associated with the addition of the aqueous phase. These macroemulsions also tend to show instability leading to oil/water separation due to their large water droplet size. Naturally, this is undesirable, since it can lead not only to problems with machine failure, but also to problems with ignition, for example in diesel engines.

Cutting oils based on water-in-oil emulsions have been used to lubricate machine tools. The superior coolant properties of water have been demonstrated to improve the life of the machine tool. However, the incorporation of water plus the instability of the macroemulsion leads to other problems, such as the lubricity of the oil, which decreases with the addition of water, thereby affecting the surface finish of the metal.

The water-in-oil emulsion (hereinafter referred to as "microemulsion") formed with an average water droplet size of 0.25 μm or less, preferably 0.1 μm or less, more preferably 0.03 to 0.08 μm is translucent. A typical value for the average water droplet size is about 0.04 μm. This small droplet size not only provides a more aesthetic appearance to the user, but also provides several major advantages over systems with larger droplet sizes. These translucent or clear microemulsions tend to be more stable than the milky macroemulsions with larger droplet sizes because the water droplets remain in the dispersion longer and macroscopic oil/water phase separation does not easily occur. The small droplet size also shows that both corrosion inhibitors and biocides are not required.

US-A-3095286(Andress et al) discloses the problem of water accumulation in fuel oil storage tanks, which results from the "aeration" of the storage vessel, with problems with rust. In order to inhibit sedimentation, screen plugging and rust in fuel oil compositions during storage, the use of an additive selected from the group consisting of: anthranilic acid, tetrahydroanthranilic acid, hexahydroanthranilic acid, and nadimic acid, and their primary amine salts having from 4 to 30 carbon atoms per molecule. There is no disclosure of additives for forming water-in-oil microemulsions of fuel oils.

US-A-3346494(Robbins et al) discloses the preparation of microemulsions using A selected combination of three microemulsion liquefiers, particularly fatty acids, amino alcohols and alkyl phenols.

FR-A-2373328(Grangette et al) discloses the preparation of microemulsions of oil and brine by using sulphur containing surfactants.

US-A-3876391(McCoy et al) discloses A method of preparing A clear, stable water-in-oil microemulsion which may contain increased amounts of water soluble additives. The microemulsion is formed by using a gasoline soluble surfactant and a water soluble surfactant. The only water-soluble surfactant used in the working examples was ethoxylated nonylphenol.

US-A-4619967(Emerson et al) discloses the use of A water-in-oil emulsion for the emulsion polymerization process.

US-A-4744796(Hazbun et al) discloses water-in-fuel stable microemulsions using A co-surfactant combination of A tertiary butyl alcohol and at least one amphoteric, anionic, cationic or nonionic surfactant. Cocamidobetaine is disclosed as a possible amphoteric surfactant.

US-A-4770670(Hazbun et al) discloses water-in-fuel stable microemulsions using A co-surfactant combination of A phenyl alcohol and at least one amphoteric, anionic, cationic or nonionic surfactant. Cocamidobetaine is disclosed as a possible amphoteric surfactant.

US-A-4832868(Schmid et al) discloses surfactant mixtures that can be used to prepare oil-in-water emulsions. There is no disclosure of any water-in-oil microemulsion comprising at least 60 wt% of an oil phase.

US-A-5633220(Cawiezel) discloses the preparation of water-in-oil emulsion fracturing fluids comprising emulsifiers sold under the trademark Hypermer by ICI (the Hypermer emulsifier is not disclosed as C)₆-C₁₅Alcohol ethoxylates or mixtures thereof).

C₆-C₁₅Mixtures of alcohol ethoxylates are commercially available surfactants that are commonly sold for use in the preparation of, for example, detergents.

WO-A-9818884 discloses water-in-fuel microemulsions, including examples of such emulsions comprising A C having 6 EO groups mixed with polyglyceryl-4-monooleate₈Alcohol ethoxylates, and C in admixture with polyglyceryl oleate linear alcohols or POE sorbitan₉-C₁₁A mixture of alcohol ethoxylates. The presence of polyglyceryl oleate and POE sorbitan tends to have an adverse effect on the viscosity properties of the emulsion, which in turn has a severe adverse effect on the lubricating properties of the emulsion.

WO-A-9850139 discloses A water-in-oil microemulsion comprising A microemulsion containing A fatty acid amine ethoxylate, C₆-C₁₅Alcohol ethoxylate and optionally tall oil fatty acid amine. The water-in-oil microemulsion may be an industrial lubricant.

WO-A-0053699 discloses A water-in-oil microemulsion comprising A microemulsion containing C₆-C₁₅Alcohol ethoxylates, amine ethoxylates and polyisobutylsuccinimide or sorbitan esters. The water-in-oil microemulsion may be a fuel.

EP- ｃA-1101815 discloses ｃA fuel, in particular for diesel engines, in the form of ｃA microemulsion comprising ｃA liquid fuel, an emulsifier and an emulsion-forming agent (emulsifying agent) having an HLB value of above 9.

US-A-6716801 discloses A stable clear water-in-oil microemulsion consisting of about 5 to 40% by weight of an aqueous phase and about 95 to about 60% by weight of A non-aqueous phase. The microemulsion comprises about 5 to 30 wt% of an emulsifier consisting of: i) c₆-C₁₅Mixture of alcohol ethoxylates, said C₆-C₁₅The alcohol ethoxylates each comprise 2 to 12 EO groups, ii)0 to about 25 wt.% of a polyisobutylsuccinimide and/or sorbitan ester, and iii)0 to about 90 wt.% of an amine ethoxylate. The emulsions are described as being useful as fuels and/or lubricants/coolants.

Mixtures of liquid emulsifiers suitable for the preparation of water-in-oil microemulsions are disclosed in WO-A-07083106. Such mixtures (often referred to as concentrates) comprise about 0.5 to about 15 wt.% fat (C)₈-C₂₄) -amido- (C)₁-C₆) Alkyl betaines, about 5 to about 99% by weight of C comprising 2 to 12 EO groups₆-C₁₅Alcohol ethoxylate or a mixture (preferably a mixture) of such alcohol ethoxylates, 0.5 to about 15 wt.% (C)₆-C₂₄) An alkyl amine oxide, and 0 or up to about 94% by weight of other nonionic emulsifiers, based on the total weight of emulsifiers in the emulsion.

However, none of the prior art citations above discloses the performance of water-in-oil microemulsions at temperatures as low as-40 ℃ or below, for example, -50 ℃.

Disclosure of Invention

The invention in its various aspects is as set out in the appended claims.

In one aspect, the present invention provides the use of at least one surfactant in a liquid hydrocarbon fuel comprising less than 50ppm of water, said at least one surfactant being capable of dispersing water in the liquid hydrocarbon fuel to provide a stable clear water-in-oil microemulsion, wherein the droplet size of the dispersed aqueous phase is no greater than 0.25 μm, wherein the amount of said at least one surfactant used in said liquid hydrocarbon fuel is sufficient to disperse at least 50ppm of water in said liquid hydrocarbon fuel, to reduce or substantially eliminate the formation of ice particles having a weight average particle size of greater than 1 μm in said liquid hydrocarbon fuel when said liquid hydrocarbon fuel is cooled to a temperature of from 0 to-50 ℃.

In another aspect, the present invention provides a method of reducing or substantially eliminating the formation of ice particles having a weight average particle size of greater than 1 μm in a liquid hydrocarbon fuel when the fuel is cooled to a temperature of from 0 to-50 ℃, the method comprising: a) providing a specified amount of a liquid hydrocarbon fuel comprising less than 50ppm water, b) providing at least one surfactant capable of dispersing water in said liquid hydrocarbon fuel to provide a stable clear water-in-oil microemulsion, wherein the droplet size of the dispersed aqueous phase is no greater than 0.25 μm, c) adding said at least one surfactant to said specified amount of liquid hydrocarbon fuel in an amount sufficient to disperse at least 50ppm of water in said liquid hydrocarbon fuel, and d) dispersing said at least one surfactant in said liquid hydrocarbon fuel.

In another aspect, the present invention provides a method of fuelling an aircraft with a liquid hydrocarbon fuel having a reduced tendency to form ice particles having a weight average particle size of greater than 1 μm when the liquid hydrocarbon fuel is cooled to a temperature of from 0 to-50 ℃ after fuelling, the method comprising: a) pumping a specified amount of liquid hydrocarbon fuel into a fuel tank of an aircraft, the liquid hydrocarbon fuel comprising less than 50ppm water, b) providing at least one surfactant capable of dispersing water in the liquid hydrocarbon fuel to provide a stable clear water-in-oil microemulsion, wherein the droplet size of the dispersed aqueous phase is no greater than 0.25 μm, c) adding the at least one surfactant to the liquid hydrocarbon fuel during or after pumping the liquid hydrocarbon fuel into the fuel tank in an amount sufficient to disperse at least 50ppm of the water in the liquid hydrocarbon fuel, and d) dispersing the at least one surfactant in the liquid hydrocarbon fuel. Also described is a method of adding the composition at or as close as possible to the aircraft wing to prevent undesirable water accumulation during the transfer of fuel from the refinery to the fuel depot. The composition may be supplied and intimately mixed with the fuel using standard fuel fuelling vehicles currently operating in any airport. When the additive composition is pumped into the aircraft wing using a venturi and/or a standard injection system, the additive composition is added directly to the fuel at a desired rate.

In another aspect, the present invention provides an aviation fuel having a reduced tendency to form ice particles having a weight average particle size of greater than 1 μm when cooled to a temperature of from 0 to-50 ℃, the liquid hydrocarbon fuel comprising:

i)45 to 4575ppm, preferably 45 to 500ppm, of at least one (C)₆-C₁₅) Alcohol ethoxylate, and/or ii)0 or up to 425ppm, for example 5 to 425ppm, preferably 2 to 50ppm, of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine.

In addition to surfactants/emulsifiers, aviation fuels may contain one or more additional components, such as antistatic agents, antioxidants, metal deactivators, leak detector additives, corrosion inhibitors, lubricity improvers, alcohols, glycols and other standard products known to those skilled in the art, as well as impurities (contaminants), such as fatty acid methyl esters.

In one aspect, the present invention provides a liquid concentrate, the liquid concentrate substantially comprising:

(A)0.1 to 10 wt% of one or more amphoteric emulsifiers;

(B)30 to 95 weight percent of one or more nonionic alkoxylated surfactants;

(C)0 to 20 wt% of one or more glycol-based solubilizers; and

(D)0 to 65 wt% of one or more organic solvents.

In another aspect, the present invention provides a process for the manufacture of a concentrate as described above, characterized in that components (a) to (D) are mixed together at a temperature of-10 ℃ to 60 ℃, preferably 0 ℃ to 40 ℃.

In another aspect, the present invention provides a stable water-in-oil emulsion, preferably a water-in-oil microemulsion, comprising:

(a) a liquid fuel or oil immiscible with water;

(b) up to 1% by weight, preferably up to 0.1% by weight, based on the amount of (a), of water; and

(c) from 10 to 10,000 wt. ppm, preferably from 10 to 1,000 wt. ppm, based on the amount of (a), of the concentrate as described above.

In another aspect, the invention provides the use of a concentrate as described above in a liquid fuel for a turbo-engine aircraft, wherein the liquid fuel is immiscible with water, characterized in that the use is for scavenging free water present as a contaminant in or introduced into the liquid fuel or oil by forming a stable water-in-oil emulsion or water-in-oil microemulsion, thereby bringing or maintaining the liquid fuel or oil in a usable state.

In another aspect, the present invention provides a method of scavenging free water present as a contaminant in or introduced into a liquid fuel, whereby the liquid fuel or oil is in or remains in a useable state, the liquid fuel being immiscible with water, the method comprising: the concentrate as described above is added to a substantially anhydrous liquid fuel or to a liquid fuel contaminated with free water to form a stable water-in-oil emulsion or water-in-oil microemulsion.

In various aspects of the invention referring to concentrates as described above, the amounts of components (a) to (D) preferably total up to 100%.

The term "free water" refers to water that exists as a separate visible liquid phase in a two-phase liquid fuel and water mixture. This may result from entrained water or water dissolved in the liquid fuel phase. The dissolved water becomes free water as the solubility of water in the liquid fuel decreases as the temperature decreases.

In the above aspect of the invention, free water is present in or introduced into the liquid fuel as a contaminant, i.e. it is not water which is deliberately added to the liquid fuel, such as water which is added to the liquid fuel in the preparation of a water-in-oil emulsion or microemulsion. When, for example, water is accidentally or unintentionally added to the liquid fuel, or the water is environmental moisture, for example from rain or condensed water resulting from changes in the humidity level in the atmosphere when the liquid fuel is in a tank leading to atmospheric conditions or in a tank subject to wide temperature variations, such as a tank on board an aircraft, free water is present in or introduced into the liquid fuel or water as a contaminant. In the above aspect of the present invention, the free water is preferably free water introduced as ambient moisture into the liquid fuel. While under extreme conditions the amount of free water that can be introduced as a contaminant may be above 0.5% by weight of the combined weight of water and liquid fuel, it will be apparent to those skilled in the art that in practice the amount of free water contaminant will typically be significantly less than 0.5% by weight of the combined weight of free water and liquid fuel. For example, typically the amount of free water contaminating the liquid fuel will be less than 0.2 wt.%, more typically less than 0.1 wt.%, such as 0.05 wt.% or less, based on the combined weight of water and liquid fuel.

The term "scavenging" is intended to mean acting as a scavenger, a "scavenger" being a substance added to a chemical reaction or mixture to counteract the effects of impurities, as defined in Collins English Dictionary, 4 th edition, 1998, reissue 1999 (twice), HarperCollins Publishers.

The terms "liquid hydrocarbon fuel", "hydrocarbon fuel" or "liquid fuel" are used herein as substantially equivalent generic terms for liquids, such as jet fuel, aviation gasoline, military grade fuel, diesel; kerosene; gasoline (lead-containing or lead-free); paraffinic oils, naphthenic oils, heavy fuel oils, biofuels, waste oils, Fatty Acid Methyl Esters (FAME), polyalphaolefins, and mixtures thereof, all of which are generally considered to be immiscible with water. Liquid fuels most suitable for the practice of the present invention are hydrocarbon fuel oils, most suitably jet fuel, aviation gasoline, military grade fuel, biodiesel, diesel, kerosene, gasoline and mixtures thereof, as well as mixtures of the foregoing with 1% by weight or more of bioethanol and/or FAME, such as Rapeseed Methyl Ester (RME).

The ability of the microemulsion to form surfactants/emulsifiers to reduce or eliminate the formation of ice particles larger than 1 μm is demonstrated by hydrocarbon fuels containing FAME, such as Rapeseed Methyl Ester (RME), as an impurity. Thus, in various related aspects of the invention, the liquid fuel may contain FAME (e.g., RME) as an impurity, for example, in an amount up to 500ppm, such as 100 ppm.

Preferably, the liquid fuel is used in a turbine engine type aircraft, i.e. is a liquid turbine fuel. The liquid turbine fuel is a turbine fuel that is conventional in civil or military aviation. These include, for example, fuels named jet fuel A, jet fuel A-1, jet fuel B, jet fuel JP-4, JP-5, JP-7, JP-8 and JP-8+ 100. Jet fuel a and jet fuel a-1 are commercially available turbine fuel specifications based on kerosene. Current standards include, for example, ASTM D1655 and DEFSTAN 91-91. Jet fuel B is a higher distillate fuel based on naphtha and kerosene fractions. JP-4 corresponds to jet fuel B. JP-5, JP-7, JP-8 and JP-8+100 are military turbine fuels. Some of these standards relate to formulations that already contain additional additives, such as corrosion inhibitors, other ice formation inhibitors, antistatic agents, detergents, dispersants, antioxidants, metal deactivators, and the like.

The term "water immiscible liquid fuel" means a liquid fuel that is immiscible with water at greater than about 0.1%, preferably at greater than 0.05%, such as a hydrocarbon fuel oil, i.e., any mixture of a liquid fuel and greater than 0.05% water separates into two phases upon standing.

The terms emulsifier, surfactant and microemulsion-forming surfactant as used herein refer to any suitable surfactant or mixture of surfactants capable of forming a water-in-oil microemulsion when simply mixed with a mixture comprising two visibly immiscible phases of liquid fuel and water. When the water: the proportion of the surfactant is 1: 1, the formation of the microemulsion is essentially spontaneous when one or more surfactants are added to a mixture comprising two visibly immiscible phases of liquid fuel and water at ambient temperature (e.g., 10-30 ℃). Such surfactants or surfactant mixtures are well known to the person skilled in the art, for example as disclosed in the microemulsion prior art references mentioned above. (while the method disclosed in US-A-3095286 for inhibiting settling, screen plugging and rust in fuel oil compositions during storage has not been investigated, the additive disclosed in US-A-3095286 is not believed to form A stable clear water-in-oil microemulsion when mixed with A mixture comprising two visibly immiscible phases of liquid fuel and water Active agent/emulsifier. However, for the avoidance of any doubt, the expression "one or more stable clear water-in-fuel microemulsion forming surfactants" as used herein excludes the amic acids of formulae (1), (2), (3) and (4) disclosed in US-A-3095286 and their salts of primary amines having from 4 to 30 carbon atoms per molecule, as well as the acylamidoalkylglycine betaines disclosed in US-A-2886423)

Mixing of suitable surfactantsThe substance may comprise C₆-C₁₅Alcohol ethoxylates, or mixtures of such ethoxylates and/or fatty acid amine ethoxylates and optionally tall oil fatty acid amines. Another suitable surfactant mixture may comprise C₆-C₁₅Alcohol ethoxylates, or mixtures of such ethoxylates and/or fatty acid amine ethoxylates and polyisobutylsuccinimide and/or sorbitan esters. Particularly suitable stable clear water-in-oil microemulsions form mixtures of surfactants that are amphoteric or include a surfactant comprising at least one amphoteric surfactant. Preferred amphoteric surfactants are betaines and sulfobetaines, in particular betaines. The most preferred surfactants are the emulsifiers described herein below.

Although the physical properties of the clear aqueous composition are not fully understood, it is believed that the clear aqueous composition comprises an aqueous phase distributed within a non-aqueous phase, wherein the aqueous phase is distributed in the non-aqueous phase in the form of droplets (possibly micelles) having an average size of no more than about 0.1 μm, such as 0.03 μm to 0.08 μm, typically about 0.04 μm.

The microemulsions of the present invention are referred to as "stable", the applicant meaning when 1: when water and a surfactant or emulsifier in a ratio of 1 are added to a liquid hydrocarbon fuel in an amount of 1 wt% (based on the total weight of the liquid hydrocarbon fuel, the water, and the surfactant/emulsifier) to form a water-in-oil emulsion, the water phase in the water-in-oil emulsion exists as dispersed droplets having an average particle diameter of not more than 0.1 μm in the oil phase for at least 12 months when stored at a constant temperature of 25 ℃ without stirring. Microemulsions have a continuous fuel phase in which are dispersed water droplets having an average droplet size of no more than 0.1 μm. The resulting clear translucent microemulsion remains thermodynamically stable when used as a fuel in an injection engine or a diesel engine. The droplets in the water-in-oil emulsion of the present invention may be in the form of micelles.

It has been unexpectedly found that when a liquid fuel containing a relevant amount of stable microemulsion forming surfactant/emulsifier and water is cooled to-50 ℃, very few, if any, visible ice particles are formed in the fuel and no gel is formed. As a way of attempting to explain the highly unexpected phenomenon, but without wishing to be bound by this explanation, it is believed that when the water-in-oil microemulsion is cooled, the presence of the surfactant/emulsifier in the liquid fuel initially prevents the water droplets dispersed in the fuel from freezing at normal temperatures by lowering the freezing point of the water, but if or when the temperature is lowered such that the water does eventually freeze, the surfactant/emulsifier limits the size of any ice crystals and agglomerates that may form in the cooled fuel. Thus, even if ice crystals form in the fuel, the surfactant/emulsifier in the fuel prevents the ice crystals from growing or agglomerating to form particles significantly above 1 μm in size, which thus means that no ice debris is formed. In addition, no formation of apple jelly was observed.

Drawings

Figure 1 shows the DSC of jet fuel with 200ppm water and 700ppm DiEGME.

Figure 2 shows the DSC of jet fuel with 200ppm water and 200ppm of the concentrate of example 4.

Figure 3A shows a container at-17 ℃ open to the atmosphere containing: jet fuel, 200ppm of red-dyed water and 200ppm of the composition from example 4.

Figure 3B shows a container at-17 ℃ to atmosphere containing jet fuel, 200ppm red-dyed water, and 700ppm DiEGME.

Figure 4 shows a comparison of the DSC of jet fuel with 200ppm water and 500ppm rapeseed methyl ester with the DSC of jet fuel with 200ppm water, 500ppm rapeseed methyl ester and 200ppm of the concentrate from example 4.

Detailed Description

The present invention may provide an aqueous fluid which, due to its inherent stability, prevents the formation of ice particles with a particle size of more than 1 μm, preferably it prevents the formation of apple jelly and ice particles with particles of more than 0.1 μm.

Prior to the present invention, materials such as diethylene glycol monomethyl ether (DiEGME) have been used to prevent ice formation in fuels in small military aircraft (commercial airlines tend to use box heaters). Due to their chemical nature, they are more soluble in water than in fuel and require significant mixing to enter the fuel. Careful monitoring must always be adhered to during mixing to ensure an initial homogenous fuel. However, no matter how carefully the DiEGME is mixed, it can separate from the fuel at low temperatures and enter the water phase (chemically, as it preferentially exists in the water phase as the temperature decreases). DiEGME will prevent a part of the water from turning into ice. However, an unusual characteristic of the DiEGME water mixture is that it forms a gel-like mass, often referred to as "apple jelly" in the aviation industry. Several aviation accidents have been attributed to this substance by the federal aviation administration. It is believed that the present invention overcomes this problem by preventing the formation of large ice crystals or ice crystal agglomerates. In fact, it is believed that the size of such particles is limited to sub-micron particles (<1 μm) if ice crystals and agglomerates form in the fuel. The DSC results in figures 1 and 2 show a comparison between fuel containing DiEGME and water-in-fuel microemulsions, respectively. The microemulsions provide several advantages over the use of DiEGME. The properties of DiEGME tend to be more hygroscopic and introduce water into the system. DiEGME is also chemically corrosive and can attack fuel tank liners and the like, and needs to be used at higher levels than emulsifiers. Handling and cleaning of DiEGME is also expensive due to the hazardous nature of the product.

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients used herein are to be understood as being modified in all instances by the term "about".

The microemulsions of the present invention may be made from standard grades of fuel available from any service station or industrial supplier. Preferably, the fuel oil is selected from the group consisting of jet fuel, aviation gasoline, military grade fuel, diesel, kerosene, gasoline (leaded or unleaded), and mixtures thereof. Preferably, the liquid fuel is used in a turbine engine type aircraft, i.e. is a liquid turbine fuel. The liquid turbine fuel is a turbine fuel that is conventional in civil or military aviation. These include, for example, fuels named jet fuel A, jet fuel A-1, jet fuel B, jet fuel JP-4, JP-5, JP-7, JP-8 and JP-8+ 100. Jet fuel a and jet fuel a-1 are commercially available turbine fuel specifications based on kerosene. Current standards include, for example, ASTM D1655 and DEF STAN 91-91. Jet fuel B is a higher distillate fuel based on naphtha and kerosene fractions. JP-4 corresponds to jet fuel B. JP-5, JP-7, JP-8 and JP-8+100 are military turbine fuels. Some of these standards relate to formulations that already contain additional additives, such as corrosion inhibitors, ice formation inhibitors, antistatic agents, detergents, dispersants, antioxidants, metal deactivators, and the like. Typical classes and species of such additional additives are disclosed in US 2008/0178523 a1, US 2008/0196300 a1, US 2009/0065744 a1, WO 2008/107371 and WO 2009/0010441.

The mixture ratio of fuel and water used in the emulsion of the present invention depends on many factors. Generally, the fuel comprises at least about 99 wt%, preferably at least about 99.5 wt%, more preferably at least about 99.995 wt%, and most preferably about 99.999 wt% of the total weight of the clear aqueous composition or emulsion. Generally, the fuel phase comprises no more than about 99.999 weight percent, and preferably no more than about 99.99 weight percent.

Typically, the compositions or microemulsions comprise from about 0.0001 to about 1.0 wt% of the surfactant/emulsifier, preferably from about 0.0001 to about 0.5 wt%, more preferably from about 0.0001 to about 0.1 wt%, even more preferably from about 0.0001 to about 0.025 wt%. The emulsifier is most preferably a mixture of emulsifiers selected to minimize the total amount of emulsifier required to form a microemulsion for a given fluid.

When a compound is referred to as being "ethoxylated", it is meant that it contains at least 2 EO groups. Preferably, the ethoxylated compound comprises 2 to 12 EO groups.

In a preferred embodiment, one or more C as component (B)₆-C₁₅The alkanol ethoxylate has an average degree of methyl branching of the alkanol units of 3.7 or less, preferably 2.5 or less, typically 1.5 to 2.5, or alternatively 3.7 or less, preferably 1.5 or less, typically 1.05 to 1.0.

When C is present₆-C₁₅When a mixture of alcohol ethoxylates is used in the microemulsion, it is preferably C₉-C₁₄Mixtures of alcohol ethoxylates, e.g. C₉To C₁₁Mixtures of alcohol ethoxylates or C_h-C₁₄A mixture of alcohol ethoxylates. The distribution of any of the components in the mixture may be from 0 to 50% by weight and is preferably in a gaussian distribution. Commercially available C₆-C₁₅Alcohol ethoxylates include related products sold by major chemical companies. Commercial sale C_h-C₁₄An example of an alcohol ethoxylate is Lauropal2 (available from Witco, England).

In one embodiment, the emulsifier comprises the following: (i)3 parts by weight of cocamidopropyl betaine; (ii)97 parts by weight of C₉-C₁₁An alcohol ethoxylate; in another embodiment, the emulsifier comprises the following: (i)1 part by weight of cocamidopropyl betaine; (ii)8 parts by weight of C₉-C₁₁An alcohol ethoxylate; (iii)3 parts by weight of C₁₀Alkylamine oxide and iv)90 parts of a non-ionic fat (C) comprising about 2 to 20 EO groups₆-C₂₄) Acid amine ethoxylates.

In another embodiment, the emulsifier comprises the following: (i)5 parts by weight of cocamidopropyl betaine; (ii)75 parts by weight of C₆-C₁₅An alcohol ethoxylate; (iii)10 parts by weight of C₁₀Alkylamine oxide and iv)10 parts of a non-ionic fat (C) comprising about 2 to 20 EO groups₆-C₂₄) Acid amine ethoxylates.

The emulsified composition used in the present invention is a liquid at room temperature.

In addition to the emulsifier, the emulsifier composition may also comprise other materials, such as aliphatic alcohols, glycols and other components that are commonly added to fuels as standard additives.

In another embodiment, the emulsified composition comprises the following: (i)2 parts of cocamidopropyl betaine; (ii)60 parts of C₉-C₁₁An alcohol ethoxylate; (iii) (iii)4 parts of ethylene glycol and (iv)34 parts of ethanol.

In one embodiment of the invention, the microemulsion is prepared by mixing: (a) about 99.995 to 99.999 parts, such as 99.998 parts, of a fuel, such as jet fuel; and (b) from about 0.0001 to about 0.01 parts, e.g., 0.025 parts, of an emulsifier, wherein the emulsifier comprises: i) fat (C)₈-C₂₄) -amido- (C)₁-C₆) Alkyl betaines, ii) C containing 2 to 12 EO groups₆-C₁₅Alcohol ethoxylates or mixtures of such alcohol ethoxylates, wherein all parts are by volume.

The invention can be used in particular in injection engines, diesel engines, fuel heating systems, etc., and is suitable for all applications in these fields of application. Other uses within the fuel industry will be apparent to those skilled in the art.

The microemulsion may comprise additional components. These additional components may be incorporated to improve antiwear, extreme pressure properties, improve cold weather performance or improve fuel combustion. The need to add additional components may be limited by the application in which the microemulsion is used. Suitable additional components, as well as their requirements depending on the field of application, will be apparent to the person skilled in the art.

The composition may be added to an aircraft wing to prevent unwanted water accumulation during the transfer of fuel from a refinery to a fuel depot. The composition may be supplied and intimately mixed with the fuel using standard fuel fuelling vehicles currently operating in any airport. When the additive composition is pumped into an aircraft wing using, for example, a venturi system, the additive composition is added directly to the fuel at a desired rate. This allows intimate mixing to occur and, due to the nature of the composition, the composition is readily distributed throughout the fuel and remains distributed in the fuel even at temperatures as low as-50 ℃.

The invention will now be further described by way of example.

Examples

Reference hereinafter to a "water-in-oil microemulsion, wherein the emulsion is a clear translucent emulsion" is considered to be analogous to a "water-in-oil microemulsion, wherein the mean droplet size of the aqueous phase of the water-in-oil emulsion is not more than 0.25 μm, preferably not more than 0.1 μm". In the examples of the present invention, the emulsions were visually inspected. Those emulsions that are clear are considered to have an average droplet size of the water phase of the water-in-oil emulsion of no more than 0.1 μm.

In the following examples, all "parts" are parts by weight unless otherwise indicated.

Example 1

A concentrate suitable for combining jet fuel (kerosene) and water is prepared by adding the components in the amounts described below:

(i)97 parts of C₉-C₁₁Alcohol ethoxylate and (ii)3 parts of cocamidopropyl betaine.

The components are gently mixed to form a homogeneous composition.

Example 2

A concentrate suitable for combining jet fuel and water is prepared by adding the following components in the amounts indicated:

(i)1 part by weight of coconut oil amidePropyl betaine; (ii)8 parts by weight of C₉-C₁₁An alcohol ethoxylate; (iii)3 parts by weight of C₁₀Alkylamine oxide and iv)90 parts of fat (C) containing about 2 to 20 Eo groups₆-C₂₄) Acid amine ethoxylates.

The components are gently mixed to form a homogeneous composition.

Example 3

A concentrate suitable for combining jet fuel and water is prepared by adding the following components in the amounts indicated:

(i)5 parts by weight of cocamidopropyl betaine; (ii)75 parts by weight of C₆-C₁₅An alcohol ethoxylate; (iii)10 parts by weight of C₁₀Alkylamine oxide and iv)10 parts of a fat (C) comprising about 2 to 20 EO groups₆-C₂₄) Acid amine ethoxylates.

The components are gently mixed to form a homogeneous composition.

Example 4

A concentrate suitable for combining jet fuel and water is prepared by adding the following components in the amounts indicated in parts by volume:

(i)2 parts of cocamidopropyl betaine; (ii)60 parts of C₉-C₁₁An alcohol ethoxylate; (iii) (iii)4 parts of ethylene glycol and (iv)34 parts of ethanol.

The components are gently mixed to form a homogeneous composition.

Example 5

0.001 l of the concentrate from example 1 was added to 1 l of jet fuel (kerosene) contaminated with 200ppm of water. The composition was introduced into oil and water from a micropipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remained stable over a year.

Example 6

0.001 l of the concentrate from example 2 was added to 1 l of jet fuel contaminated with 200ppm of water. The composition was introduced into oil and water from a micropipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remained stable over a year.

Example 7

0.001 l of the concentrate from example 3 was added to 1 l of jet fuel contaminated with 200ppm of water. The composition was introduced into oil and water from a micropipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remained stable over a year.

Example 8

0.001 l of the concentrate from example 4 was added to 1 l of jet fuel contaminated with 200ppm of water. The composition was introduced into oil and water from a micropipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remained stable over a year.

Example 9

200ppm of the concentrate from example 4 in 1 liter of jet fuel (kerosene) were subjected to Differential Scanning Calorimetry (DSC) in comparison with 700ppm of the current anti-icing product diethylene glycol monomethyl ether (DiEGME) in 1 liter of jet fuel. The resulting scan shows that the composition performed as well as DiEGME in the absence of water, but in the presence of 200ppm water contamination, the composition showed no phase change, indicating no ice formation, whereas DiEGME provided free water due to its poor solubility in fuel, especially at lower temperatures (i.e., -40 ℃), where DiEGME showed ice formation. The scans can be seen in fig. 1 and 2.

Figure 3A shows a container at-17 ℃ open to the atmosphere containing: jet fuel, 200ppm of red-dyed water and 200ppm of the composition from example 4. The mixture of jet fuel, water and the composition of example 4 was clear and substantially transparent, indicating that water and any atmospheric condensate act as a water-in-oil microemulsion in the fuel. No ice particles or apple jelly were observed in the composition.

Figure 3B shows a container at-17 ℃ to atmosphere containing jet fuel, 200ppm red-dyed water, and 700ppm DiEGME. The mixture of jet fuel, water and DiEGME was substantially opaque indicating that DiEGME did not absorb all of the water and any atmospheric condensation. Instead, the water appears to disperse in the fuel as visible droplets or ice crystals (i.e., particles over 1 micron) that agglomerate over time and form apple jelly with DiEGME at the bottom of the tank.

Example 10

The concentrate from example 4 was used to evaluate microbial growth in aviation fuel. A series of tests based on Kill rate (Speed of Kill) and Kill durability (Persistence of Kill) were performed compared to untreated water-contaminated aviation fuel. In all cases, the composition prevented the increase of microbial content, while the untreated control showed up to 10⁷Growth of colony forming units.

Example 11

DSC was performed on 200ppm water, 200ppm concentrate from example 4, and 500ppm Rapeseed Methyl Ester (RME) in 1 liter of jet fuel (kerosene) as compared to 200ppm water and 500ppm RME in 1 liter of jet fuel (kerosene). For fuels without the concentrate from example 4, the resulting scan shows a peak at about-20 ℃, indicating the presence of ice particles formed with a particle size greater than 1 μm: for jet fuel containing the concentrate of example 4, the peaks are not shown, indicating that no ice particles larger than 1 μm in size are formed.

Various modifications and variations of the described methods and systems of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. While the invention has been described in connection with certain preferred embodiments, it is to be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in chemistry or related fields are intended to be within the scope of the following claims.

Claims (20)

1. At least one of (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) Use of an alkyl betaine in a liquid hydrocarbon fuel comprising less than 50ppm water for reducing or substantially eliminating the formation of ice particles having a weight average particle size of greater than 1 μm in the liquid hydrocarbon fuel when the liquid hydrocarbon fuel is cooled to a temperature of 0 to-50 ℃, wherein the droplet size of the aqueous phase dispersed in the liquid hydrocarbon fuel is not greater than 0.25 μm, the at least one (C)₆-C₁₅) Alcohol ethoxylates in the liquidThe amount in the hydrocarbon fuel is 45 to 4575ppm, and the at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) The amount of alkyl betaine in the liquid hydrocarbon fuel is from 5 to 425 ppm.

2. A method of reducing or substantially eliminating the formation of ice particles having a weight average particle size of greater than 1 μ ι η in a liquid hydrocarbon fuel when the liquid hydrocarbon fuel is cooled to a temperature of from 0 to-50 ℃, the method comprising: a) providing a defined amount of a liquid hydrocarbon fuel comprising less than 50ppm of water, b) providing at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) Alkyl betaines, C) reacting said at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine sufficient to provide 45 to 4575ppm by weight of at least one (C) in the liquid hydrocarbon fuel₆-C₁₅) Alcohol ethoxylate and 5 to 425ppm by weight of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An amount of alkyl betaine to the prescribed amount of the liquid hydrocarbon fuel in which the droplet size of the dispersed aqueous phase is not more than 0.25 μm, and d) allowing the at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine is dispersed in the liquid hydrocarbon fuel.

3. Use or method, respectively, according to any of the preceding claims, wherein the at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) The total amount of alkyl betaines is sufficient to disperse no more than 5000ppm by weight of water in the liquid hydrocarbon.

4. Respectively according to any of the preceding claimsThe use or method of, wherein the at least one of (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) The total amount of alkyl betaines is sufficient to disperse no more than 250ppm by weight of water in the liquid hydrocarbon fuel.

5. The use or method according to claim 4, wherein the at least one (C) is added₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) The liquid hydrocarbon fuel after the alkyl betaine comprises: i) 160ppm by weight of at least one (C)₆-C₁₅) Alcohol ethoxylate, and ii)10 ppm by weight of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine.

6. A method of fuelling an aircraft with a liquid hydrocarbon fuel having a reduced tendency to form ice particles having a weight average particle size of greater than 1 μ ι η when the liquid hydrocarbon fuel is cooled to a temperature of from 0 to-50 ℃ after fuelling, the method comprising: a) pumping a defined amount of a liquid hydrocarbon fuel into a fuel tank of an aircraft, the liquid hydrocarbon fuel comprising less than 50ppm of water, b) providing at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) Alkyl betaines, C) pumping the at least one (C) during or after the liquid hydrocarbon fuel is pumped into the fuel tank₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine sufficient to provide 45 to 4575ppm by weight of at least one (C) in the liquid hydrocarbon fuel₆-C₁₅) Alcohol ethoxylate and 5 to 425ppm by weight of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) The amount of alkyl betaine added to the liquid hydrocarbon fuelThe droplet size of the dispersed aqueous phase in the fuel is not more than 0.25 μm, and d) the at least one (C)₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine is dispersed in the liquid hydrocarbon fuel.

7. The process according to claim 6, wherein the at least one (C) is provided in step b) in the form of a liquid concentrate₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) Alkyl betaines, such that in step C) the at least one (C) is injected when using a venturi tube and/or a standard injection system₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) (ii) the at least one (C) is pumped into the aircraft wing₆-C₁₅) Alcohol ethoxylate and at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) Alkyl betaines are added directly to the liquid hydrocarbon fuel.

8. An aviation fuel having a reduced tendency to form ice particles having a weight average particle size of greater than 1 μm when cooled to a temperature of from 0 to-50 ℃, the liquid hydrocarbon fuel comprising:

i)45 to 4575ppm of at least one (C)₆-C₁₅) Alcohol ethoxylate, and ii)5 to 425ppm of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine.

9. The aviation fuel of claim 8, comprising:

i)45 to 200ppm of at least one (C)₆-C₁₅) Alcohol ethoxylate, and ii)5 to 15ppm of at least one (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine.

10. The aviation fuel of claim 9 comprising one or more additional components selected from the group consisting of: one or more antistatic agents, antioxidants, metal deactivators, leak detector additives, corrosion inhibitors, lubricity improvers, alcohols, and other standard products known to those skilled in the art, as well as impurities.

11. A liquid concentrate suitable for use in the method of claim 7, consisting essentially of:

(A)0.1 to 10% by weight of one or more (C)₈-C₂₄) Alkylamide group (C)₁-C₆) An alkyl betaine;

(B)30 to 95% by weight of one or more (C)₆-C₁₅) An alcohol ethoxylate;

(C)0 to 20 wt% of one or more glycol-based solubilizers; and

(D)0 to 65 wt% of one or more organic solvents.

12. The concentrate of claim 11, consisting essentially of:

(A)0.5 to 5 wt.% of one or more fats (C)₈-C₂₄) -amido- (C)₁-C₆) -an alkyl betaine emulsifier;

(B)45 to 75 wt% of one or more C₆-C₁₅-an alkanol ethoxylate surfactant;

(C)0.5 to 10 wt% of one or more glycol-based solubilizers; and

(D)5 to 50 wt% of one or more organic solvents.

13. The concentrate of any of claims 11-12 comprising cocamidopropyl betaine as component (a).

14. The concentrate of any one of claims 11-13 comprising one or more C having an average of from 2 to 5 moles of ethylene oxide units per mole of alkanol₆-C₁₅-an alkanol ethoxylate as component (B).

15. The concentrate of any one of claims 11-14 comprising one or more C's having an average degree of methyl branching of the alkanol units of 3.7 or less₆-C₁₅-an alkanol ethoxylate as component (B).

16. The concentrate of any one of claims 11-15 comprising one or more C₆-C₁₁-an alkanol ethoxylate as component (B).

17. The concentrate of claim 16 comprising one or more C having an average of from 2 to 12 moles of ethylene oxide units per mole of alkanol₆-C₁₁-an alkanol ethoxylate as component (B).

18. The concentrate of any of claims 11-17, comprising ethylene glycol as component (C).

19. The concentrate of any one of claims 11-18 comprising one or more C₁-C₄An alkanol as component (D).

20. The concentrate of claim 19, comprising ethanol as component (D).