WO2011054817A1

WO2011054817A1 - Fuels, methods of making them and additives for use in fuels

Info

Publication number: WO2011054817A1
Application number: PCT/EP2010/066632
Authority: WO
Inventors: Alexander Francis Psaila; Patrick Grimes
Original assignee: Alternative Petroleum Technologies Sa
Priority date: 2009-11-06
Filing date: 2010-11-02
Publication date: 2011-05-12
Also published as: GB2475090B; JP2013510205A; ECSP12011952A; US20120216447A1; KR20120110169A; GB0919452D0; EP2496670A1; GB2475090A

Abstract

A water in oil emulsion comprising: a) 70 to 99wt% diesel fuel said diesel fuel comprising 0 to 50vol% biodiesel blended fuel; b) 0.5 to 30wt% water; c) 0.01 to 5wt% alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being C₁₀ to C₁₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being C₁₆ to C₁₈ alkyl amine ethoxylate; and d) 0.03 to lwt% of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 9000 to 2600 with 1 to 2 moles of a tertiary alkanol amine. The emulsion is stable and is useful as a biodiesel blended fuel.

Description

FUELS, METHODS OF MAKING THEM AND ADDITIVES

FOR USE IN FUELS

This invention relates to emulsion fuels, methods for making them, additives for use in fuels and the use of additives in fuels.

Diesel fuel is a mixture of various paraffinic, naphthenic and aromatic hydrocarbons with a carbon number of between 10 and 22. Diesel fuel also contains small quantities of organic compounds containing sulphur, nitrogen and oxygen. There are various grades of diesel tailored to suit different applications from on- and off-highway transport engines, open flame boilers, and turbine fuels. Conventional diesel is therefore oleophilic and nonpolar.

Water in conventional diesel emulsion fuels have been recognised as commercial fuels for some years. National standards were developed in France in 2000 and in Italy in 2001. The Coordinating European Council For The Development Of Performance Test For Fuels, Lubricants and Other Fluids ("CEC") has issued a workshop standard; CWA 15145:2004 for them.

The European Emulsion Fuels Manufacturers Association ("EEFMA") has published information summarising the results of many studies showing that water in conventional diesel emulsion fuels containing about 13wt% water have emissions reductions of about 25% in NO_x 60% in particulates, 80% in smoke and up to 5% in C0₂.

Biodiesel is also known. Biodiesel is a fatty acid alkyl ester. The fatty acid functionality typically comprises a mixture of C₁₈ fatty acids such stearic acid, oleic acid, and linoleic acids. Other fatty acids may also be present. The ester functionality is usually methyl on cost grounds but other esters such as ethyl, iso-propyl and butyl have been used. The fatty acid alkyl ester may be used as fuel alone or blended with conventional diesel to give fuels such as B20 and B50 which contain 20 and 50 vol% biofuel respectively. Fatty acid methyl ester is sometimes referred to as FAME. Fatty acid ethyl ester is sometimes referred to as FAEE. The fatty acid ester is polar with a hydrophilic -COOR head and an oleophilic alkyl tails. Accordingly the fatty acid ester will have a significant effect on the oil/water interface. Surfactants such as fatty amine ethoxylates (such as those derived from coco fatty acids) and polyz^'sobutylene succinate which give good emulsion stability in water in conventional diesel emulsions do not perform as well in fuels containing biodiesel.

It has been unexpectedly found that a mixture of fatty acid amine ethoxylates together with a poly/^'iObutylene succinic anhydride emulsifier obtainable by reacting a polyzsobutylene succinic anhydride ("PIBSA") containing at least 65mol%, more preferably at least 70mol% yet more preferably at least 80mol% still more preferably at least 85mol% vinylidene content with a tertiary alkanolamine can stabilise emulsions containing biodiesel. The PIBSA is sometimes known as a highly reactive polyisobutylene or "HR-PIB" from Texas Petrochemicals LP. The preparation of such polymers is known from US 4 152 499 and US 7 037 999. They are commercially available for example as Glissopal® from BASF TPC Isobutenes from Texas Petrochemicals and ULtravis®.

According to the invention there is provided a water in oil emulsion comprising:

a) 70 to 99wt% diesel fuel said diesel fuel comprising 0 to 50vol% biodiesel; b) 0.5 to 30wt% water;

c) 0.01 to 5wt% alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being do to C₁₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Ci₆ to Ci₈ alkyl amine ethoxylate; and

d) 0.03 to lwt% of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride to form a salt and / or ester.

The diesel fuel can comprise 5 to 50vol% biodiesel. The alkyl amine ethoxylate can comprises a mixture of polyoxyethylene tallow amine and polyoxyethylene coco amine.

The tertiary alkanolamine can be diethylethanolamine.

The emulsion can further comprise 0.01 to 0.1 wt% ammonium nitrate.

The emulsion can further comprise a cetane improver such as 2- ethylhexylnitrate.

The emulsion can further comprise ethylene glycol for example such that the ratio of ethylene glycol to water is in the range 1 :3 to 1 :13.

The invention further provides the use of alkyl amine ethoxylate comprising at least 25wt% do to d₄ alkyl amine ethoxylate and at least 25wt% Ci₆ to C_\% alkyl amine ethoxylate, and the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary

alkanolamine per mole of polyisobutylene succinic anhydride in stabilizing water in oil emulsions comprising dies el fuel.

The invention still further provides a composition comprising 1 to 500 parts by weight alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being Cto to Ci₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Cj6 to Cis alkyl amine ethoxylate; and 3 to 100 parts by weight of the product obtainable by reacting a polyisobutylene succinic anhydride adduct of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride.

In accordance with the invention the above composition can be used to stabilise a water in oil emulsion comprising 70 to 99 parts by weight diesel fuel and 5 to 30 parts by weight water.

The invention yet further provides a method of making an emulsion comprising blending a) 70 to 99wt% diesel fuel said diesel fuel comprising 0 to 50vol% biodiesel; b) 0.5 to 30wt% water;

c) 0.01 to 5wt% alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being C₎₀ to Q alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Ci₆ to Qg alkyl amine ethoxylate; and

d) 0.03 to lwt% of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride. The fuel base generally contains 5 to 50vol% for example 5 to 1 lvol% of biodiesel such as fatty acid methyl ester. Typically the biodiesel conforms to

EN14214 and/or ASTM D67 1. The biodiesel and diesel blend may conform to EN590. The fuel base may comprise 70 to 99wt%, such as 80 to 95wt% for example

85 to 90% of the fuel.

Water, preferably deionised water, comprises 0.5 to 30wt%, such as 5 to 25wt% for example 12 to 15wt% of the fuel.

The fuel further comprises 0.01 to 5wt% for example 0.03 to 3wt% such as 0.1 to 2wt% alkyl amine ethoxylate surfactant. Preferably the fuel comprises 0.03 tol% alkyl amine ethoxylate surfactant. At least 25wt% for example at least 35wt% such as at least 40wt% of the alkyl amine ethoxylate surfactant is Cio to C₁₄ alkyl amine ethoxylate surfactant. At least 25wt% for example at least 35wt% such as at least 40wt% of the alkyl amine ethoxylate surfactant is Ci₆ to C[₈ alkyl amine ethoxylate surfactant. The amine can be a monoamine or a diamine or a mixture thereof.

Typically each mole of functionality amine is reacted with 3 to 8 preferably 4 to 6 moles of ethylene oxide.

By at least 25wt% Cio to C₁₄ alkyl amine ethoxylate surfactant it is meant that at least 25% of the alkyl amine ethoxylate has a hydrocarbon chain containing at Cio to CM carbon atoms. Mixtures of Cio to Q₄ hydrocarbon chains to make up the requisite amount fall within the definition. By at least 25wt% Ci₆ to Ci 8 alkyl amine et oxylate surfactant it is meant that at least 25% of the alkyl amine ethoxylate has a hydrocarbon chain containing at C₁₆ to Cfs carbon atoms. Mixtures of Ci₆ to C s hydrocarbon chains to make up the requisite amount fall within the definition. The hydrocarbon chains may be saturated or unsaturated or mixtures thereof but the term alkyl is used in respect of all.

The alkyl amine ethoxylate will generally be derived from plant or animal sources. Few, if any, commercially available plant or animal sources of fatty acids have the desired chain length profile and mixtures of them will therefore generally be used. In general the alkyl chain will not be subjected to hydrogenation but it may be hydro genated.

Coconut oil typically contains a large proportion of esters of capric, lauric and myristic acid. Palm kernel oil typically contains large amounts of esters of lauric and myristic acid. These oils either alone or in mixture can comprise a source of fatty acid for the Cio to Ci₄ alkyl amine ethoxylate surfactant. An example of a Cjo to Ci alkyl amine ethoxylate containing surfactant is Ethomeen® C/15. This is a monoamine ethoxylated with 5 moles of ethylene oxide per mole of amine functionality. Tallow, canola, olive, palm, soybean and sunflower oils are each good sources of fatty acids in the C₁₆ to C|₈ range. Examples of Ci₆ to C_{[ 8} alkyl amine ethoxylate containing surfactants are Ethomeen® T/15 and SV/15 which are respectively tallow and soybean based. Each are monoamines ethoxylated with 5 moles of ethylene oxide. Another example this time a tallow diamine with three moles of ethylene oxide is Ethoduomeen®. These products are produced by Akzo Nobel.

Other suitable alkyl amine ethoxylates such as those selected from

Huntsman's Empilan® range can be used. The fuel yet further comprises a PIBSA derived emulsifier. The PIBSA from which the emulsifier is made contains at least 70mol% vinylidene and has a number average molecular weight in the range 900 to 2 600 such as 1 400 to 2 000 especially about 1 300. In some embodiments of the invention the PIBSA of molecular weight 900 to 2 600 is obtained by blending two or more PIBSAs. For example PIBSA of molecular weight 1 300 can be achieved by blending a mixture of 65 parts by weight of material having molecular weight of 950 with 35 parts by weight of material having molecular weight of 2 350 The PIBSA is further reacted with between one and two molar equivalents of a tertiary alkanolamine or mixture of tertiary alkanol amines. Tertiary alkanolamines include dimethylethanolamine and diethylethanolamine. The PIBSA is mainly in the form of monosuccinate. Less than 30 mol % preferably less than 20mol% of the PIBSA is in the form of the disuccinate. The emulsifier is present in an amount ranging from 0.03 to lwt% for example 0.05 to 0.5wt% such as 0.1 to 0.3wt%.

Optionally other components may be present.

For example the aqueous phase may contain a water soluble additive. An example is ammonium nitrate which acts as an emulsion stabiliser. Ammonium nitrate where present may be used in the range of 0.01 to 0.1 wt% preferably 0.04 to

0.08wt%.

Cetane improvers may be used. Examples of cetane improvers are alkyl nitrates such as 2-ethylhexyl nitrate and alkyl peroxides such as di /er/-butyl peroxide. If present preferably 2-ethylhexyl nitrate is used. Typically 2 000 to 8 OOOppm of cetane improver is used.

Antifreeze chemicals can also be used. Typically they are used to suppress the freezing point of water to -15°C or less. Examples of antifreezes are ethylene glycol and propylene glycol. Typically where present and depending on the ambient temperatures to which the fuel will be exposed the mass ratio of glycol to water is in the range 1 :3 to 1 :13.

The additives can be mixed together for example by dissolving in a

hydrocarbon such as an aliphatic or aromatic hydrocarbon or mixture thereof solvent. The water, fuel base and additive mixture can be mixed and emulsified in

conventional way. The invention will be illustrated by reference to the accompanying examples. Unless otherwise stated percentages are weight percentages.

The following techniques were used to characterize the emulsions:

(1) Optical microscopic examination of the emulsion using 400x magnification with a calibrated graticule for sizing of individual particles is routinely carried out to evaluate subjectively the size and population of the larger droplets. Phase contrast and polarised light microscopy can assist in determining the presence of multiple emulsion and similar phenomena. Capturing images is also a useful facility. Microscopy has the advantage of enabling the viewing of the undiluted emulsion. However it views only a drop and care needs to be exercised to ensure that the drop is representative of the bulk. Skilled microscopy can differential and rank various emulsions in order of size distribution accurately. Microscopy is not able to clearly resolve particles below 0.5μιη. A comparative system for ranking emulsions into categories can be useful.

(2) Centrifuge. The French and Italian national standards as well as CEN WS 15147:2004 define a method (MU 1548) where a 50cm³ sample of the emulsion is placed in a graduated tube and centrifuged for 5 minutes at 4200 rcf (relative centifugal force). The passing criteria are (a) no free water; and (b) a maximum white sediment band of 7% and 9% (vol.) for the 8% and 15% (mass) maximum water emulsions respectively. This test was originally conceived as a predictor of future emulsion stability (an accelerated aging test). In fact there is no simple test for predicting emulsion stability. Slow aging processes of the surfactant molecules (hydrolysis, oxidation, partitioning and redistribution of molecules, etc.) will adversely affect the ability of the surfactants to prevent the droplets from flocculating, coalescing and sedimenting. The centrifuge test can accelerate the sedimentation process but it cannot be used to predict the aging of the surfactants. The centrifuge test has been modified in order to characterise in detail the robustness of the emulsion by measuring the sediment formed after 5, 15, 25 and 35 minutes of centrifuge.

(3) A storage stability test which involves placing a sample (usually 100 a tall, clear glass, flat bottomed seal tube and standing in the dark for up to 3 months, without agitation and at ambient temperature (~20°C). Periodically (typically after 1, 3, 7 days, 2, 3, 4 weeks, 2 and 3 months) the tubes are examined carefully. Observations are made for (a) signs of 'free⁵ water; droplets or layers formed at the bottom of the tubes; (b) the volume of 'white' sediment band formed at the bottom of the tube which is measured with a ruler and expressed as a % of the total height of the fluid in the tube; (c) the volume of 'clear oil' formed at the top of the sample. This is also expressed as a % volume.

(4) Particle Size Analysis by Laser Diffraction. A Coulter™ LS 13 320 was used to measures particle size distributions by measuring the pattern of light scattered by the particles in the sample. It uses a 5 mW laser diode with a wavelength of 750 nm (or 780 nm) as the main illumination source with a secondary tungsten- halogen light source for the Polarization Intensity Differential Scattering (PIDS) system. The light from the tungsten-halogen lamp is projected through a set of filters which transmit three wavelengths (450 nm, 600 nm, and 900 nm) through two orthogonally oriented polarizers at each wavelength. The PIDS assembly provides the primary size information for particles in the 0.04 μπι to 0.4 μηι range. It also enhances the resolution of the particle size distributions up to 0.8 μπι. The combined PIDS and laser assembly enables size distribution from 0.04 microns to 2000 microns to be observed.

By skilful application of these methods an excellent description of the stability of emulsions can be obtained which enables the ranking of changes in surfactants and fuel compositions.

Laboratory emulsions were prepared on a 500 cm³ scale. The hydrocarbon fuel (either diesel or a biodiesel blended fuel) was measured in a 1 litre tall form beaker (422.5g). The additive surfactant was added to the diesel (12.5g). Invariably the additive readily dissolved in the diesel with gentle stirring using a glass rod. The water to be emulsified was measured accurately in a separate clean beaker (65g). A Silverson™ Model L4RTA with a 3.1cm rotor stator mixer was lowered to a level just over mid way down the hydrocarbon phase. The mixer was started at 9200rpm, corresponding to a tip speed of 15 m/s. The stop watch was started as soon as the water addition was initiated. The water was added over 10 seconds and mixing continued for 5 minutes.

The emulsion was allowed to cool for two hours before centrifuge and particle size analyses were carried out. Changes in particle size were monitored for up to 3 months. Storage stability samples were set aside and observations of sediment, free water and clear oily layer were earned out over a 3 month period.

Surfactant formulations BA1 to BA4 were made by mixing together the components set forth in Table 1. Amounts are given in wt%

Table 1

Isopar® M is a isoparaffinic hydrocarbon available from ExxonMobil.

Ethoduomeen® and Ethomeen® are amine ethoxylates . They are available from Akzo Nobel. As hereinbefore noted the C/15 contains a significant proportion of CJO to Ci4 alkyl units and the T/13, SV/15 and T/15 contain significant proportions of Ci 6 to C] 8 alkyl units.

PIBSAa is a 1 :2 mole ratio salt of a high vinylidene PIBSA of molecular weight 1000 with diethylethanolamine "DEEA". Emulsions were prepared with the four additives BAl, 2, 3, and 4. In all cases the water content of the emulsions was 13wt%. The additive treat rate was 2wt% and 2.5wt%. The base fuel was US #2 diesel a conventional fuel obtained from a commercial outlet.

The results for 2% additive are shown in Table 2

Table 2

The results for 2.5% additive are shown in Table 3

Table 3

The results show that good emulsions were obtained in all cases with larger amounts of additive giving better results. Additives BA3 and BA4 gave better results than BAl and BA2. Since BA3 gave good results attempts were made to optimize the proportion of the surfactants in such as system.

The following additive compositions shown in Table 4 were made up

Table 4

Once again emulsions were made with 13wt% water and US #2 diesel with 2wt% and 2.5 wt% additive.

The results are shown in Table 5

Table 5

Centrifuge (%) Particle size (μπι) Storage Stability

5 min (4200rcf) Mean D90

Measured 7 days

BA3 2% 0.4 0.51 1.09 sediment (14 days)

BA5 2% 0.8 0.58 1.44 water tr. (7 days)

BA6 2% 0.4 0.52 1.24 no sediment

BA8 2% 0.2 0.47 1.07 no sediment

BA7 2.5% 0.2 0.37 0.54 no sediment

BA8 2.5% 0.2 0.38 0.58 no sediment The results show that the best initial emulsion and best emulsion on aging is obtained when equal mass of the two key surfactants are present in the surfactant additive formulation; that is to say using BA7 and BA8.

Additive BA8 was then optimized for concentration of surfactant and amount of ammonium nitrate. The additive compositions shown in Table 6 were prepared

Table 6

The stability of 13wt% water emulsions with US #2 diesel and 2% additive was again tested. The results obtained are shown in Table 7

Table 7

It is apparent from these results that ammonium nitrate has a significant effect on emulsion stability and quality. The optimized additive BA8 was then tested with biodiesel blended fuel B20 (ie diesel containing 20% biodiesel) and with US#2 hydrocarbon diesel. Once again 13wt% water and 2wt% additive were used. The results are shown in Table 8.

Table 8

The results shown in Table 8 show a dramatic difference between biodiesel blended fuel and conventional diesel. With conventional diesel an excellent emulsion with no sediment forming even after 3 months storage is obtained. When this additive is used with diesel containing 20% biodiesel the emulsion is unstable and worse than that obtained with conventional diesel and any of the other additives tried.

Investigation was then made of the effect of introducing a Ci₆ to Ci₈ alkyl ethoxylate to the additive BA8. The additives in Table 9 were prepared.

Table 9

BA8 BA9 BA10 BA11 BA12

Isopar M 13 13 13 13 13

Ethomeen C/15 35 0 15 20 10

Ethomeen T/15 0 35 20 15 25

PIBSAa 35 35 35 35 35

2-ethylhexylynitrate 12 12 12 12 12

52% aq. NH₄NO3 5 5 5 5 5 Once again 13wt% water emulsions using 2.5wt% additive were tested. The results are shown in Table 10.

Table 10

Again the differences between conventional diesel and biodiesel blended fuel are dramatic. All the additives gave excellent emulsions with conventional diesel but soon fell apart with biodiesel blended fuel. Experiments were then made to see the effect of varying the PIBSA emulsifier. The additives shown in Table 1 1 were prepared. Table 11

PIBSAb is a similar product to PIBSAa. The PIBSAb product is based on the 2350 molecular weight high vinylidene PIB, which is reacted with maleic anhydride to give the mono succinic anhydride which is reacted with water and DEEA to form a mixture of salt, ester and succinimide.

Once again 13wt% water emulsions with 2.5wt% additive were prepared and tested. The results are shown in Table 12.

Table 12

Promising emulsions were obtained with BA13, 14 and 18. The low levels of PIBSAb (or none) give poor emulsions. This confirms that better emulsions are obtained in the presence of PIBSAb.

The surfactant ratio was further optimized by trials with differing surfactant ratios. The additives shown in Table 13.

Table 13

BA23 BA24 BA25 BA26

Isopar M 17 17 17 17

Ethomeen C/l 5 21 19 17 15

Ethomeen T/15 9 11 13 15

PIBSAa 22.5 22.5 22.5 22.5

PIBSAb 12.5 12.5 12.5 12.5

2-ethylhexylynitrate 12 12 12 12

52% aq. NH₄N0₃ 6 6 6 6 As in previous tests the stability of 13wt% emulsions and 2.5wt additive were determined. The results are shown in Table 14.

Table 14

The best emulsion was obtained with BA26. The initial emulsion was good and readily formed and no water or significant sediment observed over a 1 month period. All the additives tested in this trial however gave satisfactory results with biodiesel blended fuels.

The effect of B26 in stabilizing a range of diesels was then determined. The results are shown in Table 15.

Table 15

Fuel BA26 Centrifuge (%) Particle size (μηι) Storage Stability

% mass (4200rcf) Mean D90 (after 7 days)

5 35 min Measured 7 days

B6 1.7 1.6 8.4 0.69 1.66 no sediment

B6 2.5 0.8 4.8 0.46 1.50 no sediment

B20 2.5 0.8 4.8 0.33 1.14 no sediment

US#2 2.5 0.4 3.6 0.47 1.43 no sediment It is clear that the additive stabilized a range of conventional diesel and biodiesel blend emulsions.

The effect of BA26 in stabilizing emulsions with different water and ethylene glycol content was then tested as shown in Table 16.

Table 16

It will be apparent that the formed emulsion is stable in the presence of ethylene glycol and with different water content.

Table 17 sets forth further compositions of the invention:

Table 17

All percentages are by mass. EES6535SX is obtained by reacting a 65:35 mass ratio mixture of

poly sobutylsuccinate of molecular weight (M_w) 950 and 2 350 with maleic anhydride and then with alkanol amine. The obtained additives produced stable biodiesel blended fuel emulsions.

In addition to stabilizing water in diesel and biodiesel emulsions the invention can be used to stabilize emulsions of other distillate containing fuels such as marine gas oil ("MGO") and Marine Fuel Oil ("MFO") which is also known as Residual Fuel Oil ("RFO") and mixtures thereof such as Intermediate Fuel Oil ("IFO") which is also known as Marine Diesel Fuel ("MDF") as can be seen from the following experiments using IFO380 which is to say IFO having a kinematic viscosity at 50°C of 380mm /s using a emulsifier BA27 having the following composition :

Solvesso 150ND (ex ExxonMobil) 29wt%

Ethomeen C/15 15wt%

Ethomeen T/15 15wt%

PIBSAa 22.5wt%

PIBSAb 12.5wt%

52% aq NH₄N0₃ 6

Emulsions of the IFO380 were prepared by preheating the ingredients to 60°C and mixing for three minutes at 2400rpm using an UltraTurrax T25. All proportions are by weight.

12A 12B 12C 12D 12E

IFO380 85 84.7 84.5 84 83.5

BA27 0 0.3 0.5 1 1.5

Water 15 15 15 15 15

Total 100 100 100 100 100 The emulsions were stored in an oven at 70°C. Samples were taken from the top, middle and bottom daily and the water content (wt%) determined using the Karl Fischer method. Several samples of each example were prepared since determination destroyed the samples. The results obtained were as follows:

It will be seen that without the emulsifier the emulsion is unstable and heterogeneous but with the emulsifier it is stable and homogenous.

Claims

1. A water in oil emulsion comprising:

a) 70 to 99wt% diesel fuel said diesel fuel comprising 0 to 50vol% biodiesel blended fuel;

b) 0.5 to 30wt% water;

c) 0.01 to 5wt% alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being C₁₀ to C₁₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Cj₆ to Ci₈ alkyl amine ethoxylate; and

d) 0.03 to lwt% of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride.

2. An emulsion as claimed in claim 1 wherein said diesel fuel comprises 5 to 50vol% biodiesel blended fuel.

3. An emulsion as claimed in claim 1 or claim 2 wherein the alkyl amine ethoxylate comprises a mixture of polyoxyethylene tallow amine and polyoxyethylene coco amine.

4. An emulsion as claimed in any one of the preceding claims wherein the tertiary alkanolamine is di ethyl ethanol amine.

5. An emulsion as claimed in any one of the preceding claims further comprising

0.01 to 0.1 wt% ammonium nitrate.

6. An emulsion as claimed in any one of the preceding claims further comprising a cetane improver.

7. An emulsion as claimed in claim 6 wherein the cetane improver comprises 2- ethylhexylnitrate.

8. An emulsion as claimed in any one of the preceding claims further comprising ethylene glycol.

9. An emulsion as claimed in claim 8 wherein the ratio of ethylene glycol to water is in the range 1 :3 to 1 :13.

10. The use of alkyl amine ethoxylate comprising at least 25wt% Cio to C₁₄ alkyl amine ethoxylate and at least 25wt% Ci₆ to Cis alkyl amine ethoxylate, and the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 reacted with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride in stabilizing water in oil emulsions comprising diesel fuel.

11. A composition comprising 1 to 500 parts by weight alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being do to Cj₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Ci₆ to Cis alkyl amine ethoxylate; and 3 to 100 parts by weight of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride.

12. The use of the composition as claimed in claim 11 in stabilizing a water in oil emulsion comprising 70 to 99 parts by weight diesel fuel and 0.5 to 30 parts by weight water.

13. A method of making an emulsion comprising blending

a) 70 to 99wt% diesel fuel said diesel fuel comprising 0 to 50vol% biodiesel fuel;

b) 0.5 to 30wt% water;

c) 0.01 to 5wt% alkyl amine ethoxylate at least 25wt% of the alkyl amine ethoxylate being do to Cj₄ alkyl amine ethoxylate and at least 25wt% of the alkyl amine ethoxylate being Ci6 to Cis alkyl amine ethoxylate; and

d) 0.03 to lwt% of the product obtainable by reacting a polyisobutylene succinic anhydride of molecular weight 900 to 2600 with 1 to 2 moles of a tertiary alkanolamine per mole of polyisobutylene succinic anhydride .