Protection of liquid fuels

Abstract

The formation in a liquid hydrocarbon fuel of ice particles having a weight average particle size greater than 1 μm when said liquid hydrocarbon fuel is cooled to temperatures in the range of from 0 to −50° C. can be reduced or eliminated by use of at least one surfactant that is 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 water phase is no greater than 0.25 μm.

Claims

1. A liquid hydrocarbon fuel composition, comprising: at least one liquid hydrocarbon; 45 to 4575 ppm by weight of at least one (C.sub.6-C.sub.15) alcohol ethoxylate; 2 to 425 ppm by weight of at least one (C.sub.8-C.sub.24alkyl amido (C.sub.1-C.sub.6)alkyl betaine; and greater than 0 ppm but less than 50 ppm water; wherein the amounts of said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine in said fuel composition are selected to be sufficient to disperse at least 50 ppm water in said liquid hydrocarbon fuel composition, thereby forming a stable clear water-in-oil microemulsion wherein the droplet size of the dispersed water phase is no greater than 0.25 μm in the liquid hydrocarbon fuel, and the content of ice particles having a weight average particle size greater than 1 μm in said liquid hydrocarbon fuel composition when said liquid hydrocarbon fuel composition is cooled to temperatures in the range of from 0 to −50° C. being (i) reduced as compared to the content of ice particles in an otherwise identical fuel composition not containing the recited amount of said ethoxylate in combination with the recited amount of said betaine or (ii) substantially eliminated.

2. A method of reducing or substantially eliminating the formation in a liquid hydrocarbon fuel of ice particles having a weight average particle size greater than 1 μm when said liquid hydrocarbon fuel is cooled to temperatures in the range of from 0 to −50° C., said method comprising a) providing a specified amount of liquid hydrocarbon fuel, said liquid hydrocarbon fuel comprising greater than 0 ppm but less than 50 ppm water, b) providing at least one (C.sub.6-C.sub.15) alcohol ethoxylate and at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine, c) adding said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine to said specified amount of liquid hydrocarbon fuel in an amount sufficient to provide from 45 to 4575 ppm by weight of at least one (C.sub.6-C.sub.15) alcohol ethoxylate and from 2 to 425 ppm by weight of at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine in said liquid hydrocarbon fuel, and d) dispersing said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine in said liquid hydrocarbon fuel.

3. The method as claimed in claim 2, wherein the total amount of said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine is sufficient to disperse no more than 5000 ppm water in said liquid hydrocarbon.

4. The method as claimed in claim 2, wherein the total amount of said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine is sufficient to disperse no more than 250 ppm water in said liquid hydrocarbon fuel.

5. The method as claimed in claim 4, wherein said hydrocarbon fuel after addition of said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine comprises i) about 160 ppm of at least one (C.sub.6-C.sub.15) alcohol ethoxylate and ii) about 10 ppm of at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine.

6. A method of refueling an aircraft with a liquid hydrocarbon fuel which after refueling has a reduced tendency to form ice particles having a weight average particle size greater than 1 μm when said liquid hydrocarbon fuel is cooled to temperatures in the range of from 0 to −50° C., said method comprising a) pumping a specified amount of liquid hydrocarbon fuel into a fuel tank of an aircraft, said liquid hydrocarbon fuel comprising greater than 0 ppm but less than 50 ppm water, b) providing at least one (C.sub.6-C.sub.15) alcohol ethoxylate and at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine, c) adding said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine to said liquid hydrocarbon fuel in an amount sufficient to provide from 45 to 4575 ppm by weight of at least one (C.sub.6-C.sub.15) alcohol ethoxylate and from 2 to 425 ppm by weight of at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine in said liquid hydrocarbon fuel during or after said liquid hydrocarbon fuel is pumped into said fuel tank, and d) dispersing said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine in said liquid hydrocarbon fuel.

7. The method as claimed in claim 6, wherein in step b) said at least one (C.sub.6-C.sub.15) alcohol ethoxylate and said at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine are provided as a liquid concentrate that in step c) is dosed directly into the fuel as it is pumped into the fuel tank of the aircraft.

8. An aircraft fuel having a reduced tendency to form ice particles having a weight average particle size greater than 1 μm when said liquid hydrocarbon fuel is cooled to temperatures in the range of from 0 to −50° C., said liquid hydrocarbon fuel comprising: i) from 45 to 4575 ppm of at least one (C.sub.6-C.sub.15) alcohol ethoxylate and ii) from 2 to 425 ppm of at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine.

9. The aircraft fuel as claimed in claim 8 comprising: i) from 45 to 200 ppm of at least one (C.sub.6-C.sub.15) alcohol ethoxylate and ii) from 2 to 15 ppm of at least one (C.sub.8-C.sub.24)alkyl amido (C.sub.1-C.sub.6)alkyl betaine.

10. The aircraft fuel as claimed in claim 9 comprising one or more static dissipaters, antioxidants, metal deactivators, leak detector additives, corrosion inhibitors, lubricity improvers, alcohols, glycols, or contaminants.

Description

DRAWINGS

(1) FIG. 1. Shows a DSC of Jet fuel with 200 ppm water and 700 ppm DiEGME

(2) FIG. 2. shows a DSC of Jet fuel with 200 ppm water and 200 ppm concentrate of Example 4.

(3) FIG. 3 A shows a container at −17° C. vented to the atmosphere containing: jet fuel, 200 ppm water dyed red and 200 ppm composition from Example 4.

(4) FIG. 3 B shows a container at −17° C. vented to the atmosphere containing jet fuel, 200 ppm water dyed red and 700 ppm DiEGME.

(5) FIG. 4 Shows a comparison of a DSC of Jet fuel with 200 ppm water and 500 ppm rapeseed methyl ester against a DSC of Jet fuel with 200 ppm water, 500 ppm rapeseed methyl ester and 200 ppm concentrate from Example 4.

DETAILED DESCRIPTION

(6) The present invention may provide a water content fluid that due to the inherent stability prevents the formation of ice particles having a particle size greater than 1 μm, preferably it prevents the formation of ice particles having a particle greater than 0.1 μm, and apple jelly.

(7) Prior to the present invention, materials such as diethylene glycol monomethyl ether (DiEGME) have been used to prevent ice formation in fuel in small and military aircraft (commercial airlines tend to use tank heaters). Due to their chemical properties they are more soluble in water than in fuel and take a great deal of mixing to get into the fuel. Careful monitoring during the mixing process must be adhered to at all times to ensure an initial homogenous fuel. However, no matter how carefully mixed the DiEGME, (the chemistry is such that it will preferentially reside in the water phase as temperature reduces) it can separate from the fuel at low temperatures and enter the water phase. The DiEGME will prevent some of this water from turning to ice. However, the DiEGME water mixture has an unusual characteristic in that it forms a gel like substance often referred to as “apple jelly” in the aviation industry. Federal Aviation authorities have attributed several aviation accidents to this material. The present invention overcomes this problem by, it is believed, preventing the formation of large ice crystals or ice crystal agglomerates. Indeed, it is believed that if ice crystals and agglomerates are formed in the fuel, the size of such particles is restricted to sub-micron particles (<1 μm). DSC results in FIGS. 1 & 2 show the comparison between a DiEGME containing fuel and a water-in-fuel microemulsion, respectively. The microemulsion offers several advantages over the use of DiEGME. The latter tends to be more hygroscopic in nature and will draw water into a system. The DiEGME is also chemically aggressive and may attack fuel tank linings etc, and needs to be used at higher levels than the emulsifying agents. The handling and disposal of DiEGME is also costly due to the hazardous nature of the product.

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

(9) The microemulsion of the present invention may be prepared from fuels that are standard grades available at any service station or from industrial suppliers. Preferably, the fuel oil is selected from jet fuels, aviation gasolines, military grade fuels, diesel, kerosene, gasoline/petrol (leaded or unleaded) and mixtures thereof. Preferably the liquid fuel is for a turbine engine aircraft i.e. a liquid turbine fuel. A liquid turbine fuel is a turbine fuel customary in civilian or military aviation. These include, for example, fuels of the designation 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 A and Jet A-1 are commercially available turbine fuel specifications based on kerosene. Current standards include, for example, ASTM D 1655 and DEF STAN 91-91. Jet B is a more highly cut fuel based on naphtha and kerosene fractions. JP-4 is equivalent to Jet B. JP-5, JP-7, JP-8 and JP-8+100 are military turbine fuels. Some of these standards relate to formulations which already comprise further additives such as corrosion inhibitors, icing inhibitors, static dissipators, detergents, dispersants, antioxidants, metal deactivators, etc. Typical classes and species of such further additives are disclosed in US 2008/0178523 A1, US 2008/0196300 A1, US 2009/0065744 A1, WO 2008/107371 and WO 2009/0010441.

(10) The mixture ratios of the fuel and water employed in the present emulsion are dependent upon many factors. Generally speaking, the fuel comprises at least about 99%, preferably at least about 99.5%, more preferably at least about 99.995%, most preferably about 99.999% by weight, based on the total weight of the clear aqueous composition or emulsion. Generally speaking, the fuel phase comprises no greater than about 99.999% by weight, and preferably no more than about 99.99% by weight.

(11) Typically, the composition or microemulsion comprises from about 0.0001 to about 1.0% by weight of surfactants/emulsifying agents, preferably from about 0.0001 to about 0.5%, more preferably from about 0.0001 to about 0.1%, and even more preferably from about 0.0001 to about 0.025%. The emulsifier is most preferably a mixture of emulsifying agents selected to minimise the total amount of emulsifier required to form a microemulsion for a given fluid.

(12) Where a compound is referred to as being “ethoxylated”, we mean it includes at least 2 EO groups. Preferably ethoxylated compounds comprise from 2 to 12 EO groups.

(13) In a preferred embodiment, the one or more C.sub.6-C.sub.15 alkanol ethoxylates as component (B) have an average degree of methyl branching for the alkanol unit of 3.7 or less, preferably of 2.5 or less, typically of from 1.5 to 2.5, or, as an alternative, of 3.7 or less, preferably of 1.5 or less, typically of from 1.05 to 1.0.

(14) When a mixture of C.sub.6-C.sub.15 alcohol ethoxylates is employed in the microemulsion, it is preferably a mixture of C.sub.9-C.sub.14 alcohol ethoxylates, such as a mixture of C.sub.9 to C.sub.11 alcohol ethoxylates or a mixture of C.sub.12-C.sub.14 alcohol ethoxylates. The distribution of any of the components in the mixture can range from 0 to 50% by weight, and are preferably distributed in a Gaussian format. Commercially available C.sub.6-C.sub.15 alcohol ethoxylates include relevant products sold by leading chemical companies. An example of a commercial C.sub.12-C.sub.14 alcohol ethoxylate is Lauropal 2 (available from Witco, England).

(15) In one embodiment, the emulsifying agent comprises the following: (i) 3 parts by wt cocoamidopropyl betaine; (ii) 97 parts by wt C.sub.9-C.sub.11 alcohol ethoxylate; In another embodiment, the emulsifying agent comprises the following: (i) 1 part by wt cocoamidopropyl betaine; (ii) 8 parts by wt C.sub.9-C.sub.11 alcohol ethoxylate; (iii) 3 parts by wt C.sub.10 alkyl amine oxide and iv) 90 parts nonionic fatty (C.sub.6-C.sub.24)acid amine ethoxylates comprising from about 2 to 20 EO groups.

(16) In another embodiment, the emulsifying agent comprises the following: (i) 5 parts by wt cocoamidopropyl betaine; (ii) 75 parts by wt C.sub.6-C.sub.15 alcohol ethoxylate; (iii) 10 parts by wt C.sub.10 alkyl amine oxide and iv) 10 parts nonionic fatty (C.sub.6-C.sub.24) acid amine ethoxylates comprising from about 2 to 20 EO groups.

(17) The emulsifying compositions employed in the present invention are liquids at room temperature.

(18) As well as emulsifying agents, the emulsifier composition may also include other materials such as aliphatic alcohols, glycols and other components which are typically added to be added to a fuel as standard additives.

(19) In another embodiment, the emulsifying composition comprises the following: (i) 2 parts cocoamidopropyl betaine; (ii) 60 parts C.sub.9-C.sub.11 alcohol ethoxylate; (iii) 4 parts ethylene glycol and (iv) 34 parts ethanol

(20) In one embodiment of the present invention, a microemulsion is prepared by mixing: (a) about 99.995 to 99.999 parts, e.g. 99.998 parts, fuel, e.g. a jet fuel; and (b) about 0.0001 to about 0.01 parts, e.g. 0.025 parts, emulsifying agents, wherein the emulsifying agents include i) a fatty (C.sub.8-C.sub.24)-amido-(C.sub.1-C.sub.6)alkyl betaine, ii) a C.sub.6-C.sub.15 alcohol ethoxylate comprising from 2 to 12 EO groups or a mixture of such alcohol ethoxylates, wherein all parts are by volume.

(21) The present invention may be utilised in, among others, jet engines, diesel engines, oil burning heating systems and is suited to all uses within these application areas. Other uses within the fuels industry will be apparent to those skilled in the art.

(22) The microemulsion may comprise additional components. These additional components may be incorporated to improve anti-wear, extreme pressure properties, improve cold weather performance or improve fuel combustion. The requirement to add additional components may be dictated by the application area in which the microemulsion is used. Suitable additional components, and the requirement thereof depending on application area, will be apparent to those skilled in the art.

(23) The composition may be added at the wing of the aircraft to prevent unwanted water pick up during the process of transferring the fuel from refinery to fuel depot. The composition can be supplied and intimately mixed with the fuel using a standard fuel bowser that is currently in operation at any airport. The additive composition can be dosed at the required rate directly into the fuel as it is pumped into the aircraft wing using e.g. a venturi system. This allows intimate mixing to occur and due to the nature of the composition it readily distributes throughout the fuel and will remain distributed in the fuel even at temperatures down to as low as −50° C.

(24) The present invention will now be further described by way of example.

EXAMPLES

(25) Reference hereafter to “a water-in-oil microemulsion wherein the emulsion is a clear translucent emulsion” is believed to be analogous to “a water-in-oil microemulsion, wherein the average droplet size of the water phase of the water-in-oil emulsion is no greater than 0.25 μm, preferably no greater than 0.1 μm”. In the present examples, the emulsions were visually inspected. Those which were clear were considered to have an average droplet size of the water phase of the water-in-oil emulsion of no greater than 0.1 μm.

(26) In the following examples, all “parts” are parts by weight, unless stated otherwise.

Example 1

(27) A concentrate suitable for combining jet fuel (kerosene) with water was prepared by adding the following components in the quantities stated:

(28) (i) 97 parts C.sub.9-C.sub.11 alcohol ethoxylate and (ii) 3 parts cocoamidopropyl betaine.

(29) The components were gently mixed to form a homogenous composition.

Example 2

(30) A concentrate suitable for combining jet fuel with water was prepared by adding the following components in the quantities stated:

(31) i) 1 part by wt cocoamidopropyl betaine; (ii) 8 parts by wt C.sub.9-C.sub.11 alcohol ethoxylate; (iii) 3 parts by wt C.sub.10 alkyl amine oxide and iv) 90 parts fatty (C.sub.6-C.sub.24) acid amine ethoxylates comprising from about 2 to 20 EO groups.

(32) The components were gently mixed to form a homogenous composition.

Example 3

(33) A concentrate suitable for combining jet fuel with water was prepared by adding the following components in the quantities stated:

(34) (i) 5 parts by wt cocoamidopropyl betaine; (ii) 75 parts by wt C.sub.6-C.sub.15 alcohol ethoxylate; (iii) 10 parts by wt C.sub.10 alkyl amine oxide and iv) 10 parts fatty (C.sub.6-C.sub.24) acid amine ethoxylates comprising from about 2 to 20 EO groups.

(35) The components were gently mixed to form a homogenous composition.

Example 4

(36) A concentrate suitable for combining jet fuel with water was prepared by adding the following components in parts by volume in the quantities stated:

(37) (i) 2 parts cocoamidopropyl betaine; (ii) 60 parts C.sub.9-C.sub.11 alcohol ethoxylate; (iii) 4 parts ethylene glycol and (iv) 34 parts ethanol

(38) The components were gently mixed to form a homogenous composition.

Example 5

(39) 0.001 l of the concentrate from Example 1 was added to 1 l of jet fuel (kerosene) contaminated with 200 ppm of water. The composition was introduced to the oil and water from a micro pipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remains stable after more than one year.

Example 6

(40) 0.001 l of the concentrate from Example 2 was added to 1 l of jet fuel contaminated with 200 ppm of water. The composition was introduced to the oil and water from a micro pipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remains stable after more than one year.

Example 7

(41) 0.001 l of the concentrate from Example 3 was added to 1 l of jet fuel contaminated with 200 ppm of water. The composition was introduced to the oil and water from a micro pipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remains stable after more than one year.

Example 8

(42) 0.001 l of the concentrate from Example 4 was added to 1 l of jet fuel contaminated with 200 ppm of water. The composition was introduced to the oil and water from a micro pipette. The resulting fluid was gently mixed until a clear translucent fluid was observed. The resulting fluid remains stable after more than one year.

Example 9

(43) 200 ppm of the concentrate from Example 4 in 1 l of jet fuel (kerosene) was subject to differential scanning calorimetry (DSC) in comparison to 700 ppm of current anti icing product diethylene glycol monomethyl ether (DiEGME) in 1 l of jet fuel. The resulting scans showed that the composition performed equally as well as the DiEGME in the absence of water but in the presence of 200 ppm water contamination the composition showed no phase changes indicating no ice formation, whereas the DiEGME showed that ice was forming due to its poor solubility in fuel allowing free water particularly at lower temperatures i.e. −40° C. The scans can be seen in FIGS. 1 & 2.

(44) FIG. 3 A shows a container at −17° C. vented to the atmosphere containing: jet fuel, 200 ppm water dyed red and 200 ppm composition from Example 4. The mixture of jet fuel, water and composition of Example 4 is clear and substantially transparent, indicating that the water and any atmospheric condensation is in the fuel as a water-in oil microemulsion. No ice particles or apple jelly are observed in the composition.

(45) FIG. 3 B shows a container at −17° C. vented to the atmosphere containing jet fuel, 200 ppm water dyed red and 700 ppm DiEGME. The mixture of jet fuel, water and DiEGME is substantially opaque, indicating that the DiEGME has not absorbed all the water and any atmospheric condensation. Instead, the water appears dispersed in the fuel as visible droplets or ice crystals, i.e. particles over 1 micron, which over time agglomerate and form an apple jelly with the DiEGME at the bottom of the tank.

Example 10

(46) The concentrate from Example 4 was used to evaluate microbial growth in aviation fuel. A series of tests based upon the Speed of Kill and the Persistence of Kill were carried out in comparison to an untreated water contaminated aviation fuel. In all cases the composition prevented the growth of microbial content whereas, the untreated control showed growth up to 10.sup.7 colony forming units.

Example 11

(47) 200 ppm water, 200 ppm of the concentrate from Example 4 and 500 ppm rapeseed methyl ester (RME) in 1 l of jet fuel (kerosene) was subject to DSC in comparison to 200 ppm water and 500 ppm RME in 1 L of jet fuel (kerosene). The resulting scans showed a peak at about −20° C. for the fuel that contained no concentrate from Example 4, which was indicative of the presence of ice particles forming with a particle size of greater than 1 μm: no such peak is shown for the jet fuel containing the concentrate of Example 4, which is indicative of no ice particles forming with a particle size of greater than 1 μm.

(48) Various modifications and variations of the described methods and system of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should 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.