FUEL COMPOSITIONS COMPRISING AN ADDITIVE, AND METHODS AND USES RELATING THERETO

The present invention relates to methods and uses for improving the performance of fuel compositions using additives. The invention relates to diesel fuel and gasoline fuel compositions suitable for use in modern engines in which fuel injectors are exposed to high temperatures and pressures. In particular the invention relates to additives for diesel fuel compositions, especially for use in diesel engines with high pressure fuel systems.

Due to consumer demand and legislation, diesel engines have in recent years become much more energy efficient, show improved performance and have reduced emissions.

These improvements in performance and emissions have been brought about by improvements in the combustion process. To achieve the fuel atomisation necessary for this improved combustion, fuel injection equipment has been developed which uses higher injection pressures and reduced fuel injector nozzle hole diameters. The fuel pressure at the injection nozzle is now commonly in excess of 1500 bar (1.5 x 10 ⁸ Pa). To achieve these pressures the work that must be done on the fuel also increases the temperature of the fuel. These high pressures and temperatures can cause degradation of the fuel. Furthermore, the timing, quantity and control of fuel injection has become increasingly precise. This precise fuel metering must be maintained to achieve optimal performance.

Diesel engines having high pressure fuel systems can include but are not limited to heavy duty diesel engines and smaller passenger car type diesel engines. Heavy duty diesel engines can include very powerful engines such as the MTU series 4000 diesel having 20 cylinder variants designed primarily for ships and power generation with power output up to 4300 kW or engines such as the Renault dXi 7 having 6 cylinders and a power output around 240kW. A typical passenger car diesel engine is the Peugeot DW10 having 4 cylinders and power output of 100 kW or less depending on the variant.

A common problem with diesel engines is fouling of the injector, particularly the injector body, and the injector nozzle. Fouling may also occur in the fuel filter. Injector nozzle fouling occurs when the nozzle becomes blocked with deposits from the diesel fuel. Fouling of fuel filters may be related to the recirculation of fuel back to the fuel tank. Deposits increase with degradation of the fuel. Deposits may take the form of carbonaceous coke-like residues, lacquers or sticky or gum-like residues. Diesel fuels become more and more unstable the more they are heated, particularly if heated under pressure. Thus diesel engines having high pressure fuel systems may cause increased fuel degradation. In recent years the need to reduce emissions has led to the continual redesign of injection systems to help meet lower targets. This has led to increasingly complex injectors and lower tolerance to deposits.

The problem of injector fouling may occur when using any type of diesel fuels. However, some fuels may be particularly prone to cause fouling or fouling may occur more quickly when these fuels are used. For example, fuels containing biodiesel and those containing metallic species may lead to increased deposits.

When injectors become blocked or partially blocked, the delivery of fuel is less efficient and there is poor mixing of the fuel with the air. Over time this leads to a loss in power of the engine and increased exhaust emissions and poor fuel economy.

Deposits are known to occur in the spray channels of the injector, leading to reduced flow and power loss. As the size of the injector nozzle hole is reduced, the relative impact of deposit build up becomes more significant. Deposits are also known to occur at the injector tip. Here they affect the fuel spray pattern and cause less effective combustion and associated higher emissions and increased fuel consumption.

In addition to these “external” injector deposits in the nozzle hole and at the injector tip which lead to reduced flow and power loss, deposits may occur within the injector body causing further problems. These deposits may be referred to as internal diesel injector deposits (or IDIDs). IDIDs occur further up inside the injector on the critical moving parts. They can hinder the movement of these parts affecting the timing and quantity of fuel injection. Since modern diesel engines operate under very precise conditions these deposits can have a significant impact on performance.

IDIDs cause a number of problems, including power loss and reduced fuel economy due to less than optimal fuel metering and combustion. Initially the engine may experience cold start problems and/or rough engine running. These deposits can lead to more serious injector sticking. This occurs when the deposits stop parts of the injector from moving and thus the injector stops working. When several or all of the injectors stick the engine may fail completely.

IDIDs are recognised as a serious problem by those working in the field and a new engine test has been developed by the industry based organisation, the Coordinating European Council (CEC). The IDID DW10C test was developed to be able to discriminate between a fuel that produces no measurable deposits and one which produces deposits that cause unacceptable startability issues. The objective of the test is to discriminate between fuels that differ in their ability to produce IDIDs in direct injection common rail diesel engines. Internal diesel injector deposits are known to contain a number of components. As well as carbonaceous deposits the presence of lacquers and/or carboxylate residues can lead to injector sticking.

Lacquers are varnish-like deposits which are insoluble in fuel and common organic solvents. Some occurrences of lacquers have been found by analysis to contain amide functionality and it has been suggested that they form due to the presence of low molecular weight amide containing species in the fuel.

Carboxylate residues may be present from a number of sources. By carboxylate residues we mean to refer to salts of carboxylic acids. These may be short chain carboxylic acids but more commonly long chain fatty acid residues are present. The carboxylic residues may be present as ammonium and/or metal salts. Both carboxylic acids and metals may be present in diesel fuel from a number of sources. Carboxylic acids may occur due to oxidation of the fuel, may form during the combustion process and are commonly added into fuel as lubricity additives and/or corrosion inhibitors. Residual fatty acids may be present in the fatty acid methyl esters included as biodiesel and they may also be present as byproducts in other additives. Derivatives of fatty acids may also be present and these may react or decompose to form carboxylic acids.

Various metals may be present in fuel compositions. This may be due to contamination of the fuel during manufacture, storage, transport or use or due to contamination of fuel additives. Metal species may also be added to fuels deliberately. For example, transition metals are sometimes added as fuel borne catalysts to improve the performance of diesel particulate filters.

The present inventors believe that one of the many causes of injector sticking occurs when metal or ammonium species react with carboxylic acid species in the fuel. One example of injector sticking has arisen due to sodium contamination of the fuel. Sodium contamination may occur for a number of reasons. For example, sodium hydroxide may be used in a washing step in the hydrodesulfurisation process and could lead to contamination. Sodium may also be present due to the use of sodium-containing corrosion inhibitors in pipelines. Another example can arise from the presence of calcium from, for example, interaction with or contamination with a lubricant or from calcium chloride used in salt drying processes in refineries. Other metal contamination may occur for example during transportation due to water bottoms. Metal contamination of diesel fuel and the resultant formation of carboxylate salts is believed to be a significant cause of injector sticking. The formation of lacquers is yet another major cause of injector sticking.

One approach to combatting IDIDs and injector sticking resulting from carboxylate salts is to try to eliminate the source of metal contamination and/or carboxylic acids or to try to ensure that particularly problematic carboxylic acids are eliminated. This has not been entirely successful and there is a need for additives to provide control of IDIDs.

Deposit control additives are often included in fuel to combat deposits in the injector nozzle or at the injector tip. These may be referred to herein as “external injector deposits”. Additives are also used to control deposits on vehicle fuel filters. However additives which have been found to be useful to control “external deposits” and fuel filter deposits are not always effective at controlling IDIDs. A challenge for the additive formulator is to provide more effective detergents.

It is an aim of the present invention to provide methods and uses which improve the performance of a diesel engine, especially a diesel engine having a high pressure fuel system. This may be achieved for example by preventing or reducing the formation of IDIDs and/or by reducing or removing existing IDIDs. The invention provides methods and uses which control “external injector deposits” and/or fuel filter deposits.

A further aim of the present invention is to provide an additive suitable for use in gasoline compositions which reduces the formation of deposits in spark ignition engines, especially direct injection spark ignition (or DISI) engines. These are also known as direct injection gasoline (DIG) or gasoline direct injection (GDI) engines. These engines include injection systems where the fuel is injected directly into the combustion chamber. Whilst such a system facilitates reliable combustion, this injection strategy means that the fuel injector is subjected to high temperatures and pressures, increasing the likelihood of forming deposits from the high temperature degradation of the fuel. The fact that the injector is in the combustion chamber also exposes the injector to combustion gases which may contain partially oxidised fuel and or soot particles which may accumulate, increasing the level of deposits. The ability to provide good atomisation of fuel and precise control of fuel flow rates and injection duration are critical to the optimum performance of these engines. Control of deposits in this area is therefore very important.

Reducing or preventing the formation of deposits may be regarded as providing “keep clean’ performance. Reducing or removing existing deposits may be regarded as providing “clean up’ performance. It is an aim of the present invention to provide “keep clean” and/or “clean up” performance.

Many different types of compounds are known in the art for use as detergent additives in fuel oil compositions, for the control of deposits in engines. Examples of common detergents include hydrocarbyl-substituted amines; hydrocarbyl substituted succinimides; Mannich reaction products and quaternary ammonium salts. All of these known detergents are nitrogen-containing compounds.

The present invention relates in particular to polymeric detergent compounds for diesel or gasoline fuel that do not contain nitrogen. Such compounds are much less commonly used as detergents.

According to a first aspect of the present invention there is provided a fuel composition comprising as an additive a polymer of formula (I): wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

According to a second aspect of the present invention there is provided a method of improving the performance of an engine, the method comprising combusting in the engine a fuel composition comprising as an additive a polymer of formula (I): wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

According to a third aspect of the present invention there is provided the use of a polymer of formula (I): as an additive for a fuel composition to improve the performance of an engine combusting said fuel composition; wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

The method of the second aspect preferably involves combusting in the engine a composition of the first aspect. Preferred features of the first, second and third aspects of the invention will now be described. Any feature of any aspect may be combined with any feature of any other aspect as appropriate.

The present invention relates to a composition, a method and a use involving a polymeric fuel additive. This polymeric additive may be referred to herein as “the additive of the present invention”.

The additive of the present invention may be prepared by polymerising a dicarboxylic acid of formula (II): or an anhydride thereof and then esterifying the polymerised diacid. In preferred embodiments polymer additive of the present invention is prepared by polymerising the reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof and an alcohol. Thus the additive of the present invention is preferably prepared by forming an ester of a dicarboxylic acid of formula (II) and an alcohol formula ROH; and then polymerising the ester.

Polymerisation is preferably carried out by a free radical initiated process.

The dicarboxylic acid compound of formula (II) includes free carboxylic acid groups and/or anhydride groups.

When the compound of formula (II) includes anhydride groups these may be an internal cyclic anhydride in which two carboxylic acid groups within the structure of formula (II) are reacted together to form an anhydride, for example as shown in formula (III):

Such a cyclic anhydride group may be regarded as equivalent to two free carboxylic acid groups.

In some embodiments the anhydride may be a non-cyclic anhydride.

When an anhydride is used the polymer may optionally be hydrolysed to provide acid residues. Suitable hydrolysis conditions will be known to the person skilled in the art.

The additive of the present invention is a polymer of formula (I): n is at least 4. Preferably n is at least 6, more preferably at least 8, for example at least 10. Suitably n is from 10 to 200, preferably from 15 to 80, more preferably from 20 to 60, for example from 25 to 50. x may be from 0 to 10, for example from 0 to 6, from 0 to 4 or from 0 to 2. y may be from 0 to 10, for example from 0 to 6, from 0 to 4 or from 0 to 2. Preferably x+y is at least 1. Preferably x+y is less than 20, preferably less than 15, more preferably less than 10. Preferably x+y is less than 8, preferably less than 6.

Preferably x+y is from 1 to 10, more preferably from 1 to 6, for example from 1 to 4.

Preferably x is 0 and y is at least 1 . Preferably y is from 1 to 10, preferably from 1 to 6.

In some preferred embodiments, x is 0 and y is from 1 to 4, preferably from 1 to 3.

Most preferably x + y = 1 .

For the avoidance of doubt, the definitions of x and y apply to structures shown in formula (I), in formula (II) and in formula (III).

Some preferred dicarboxylic acid compounds for use in preparing the additives of the present invention are itaconic acid, itaconic anhydride, 2-methylene glutaric acid, 2-methylene glutaric anhydride, 2-methylene adipic acid, 2-methylene adipic anhydride and isomers and/or mixtures thereof.

One especially preferred dicarboxylic acid compound for use herein is itaconic acid, which has the formula (IV):

One preferred anhydride is itaconic anhydride, which has the formula (V): (V)

The additives of the present invention are preferably the polymerised reaction product of a dicarboxylic acid or anhydride thereof and an alcohol.

Suitably the alcohol has 1 to 60 carbon atoms. Preferably the alcohol has at least 4 carbon atoms.

Any suitable alcohol, preferably having at least 4 carbon atoms may be used to prepare the additives of the present invention.

The alcohol may be a monohydric alcohol or a polyhydric alcohol. Monohydric alcohols are preferred.

Preferably the alcohol is a compound of formula H-(OR ² ) _m -OR ¹ , wherein R ² is an optionally substituted alkylene or arylene group; R ¹ is hydrogen or an optionally substituted hydrocarbyl group; and m is 0 or a positive integer; provided that m is not 0 when R ¹ is hydrogen.

In the polymeric additives of the present invention of formula (I), each group R is suitably hydrogen or a group of formula (OR ² ) _m OR ¹ .

As used herein, the term "hydrocarbyl substituent" or "hydrocarbyl group" is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

(i) hydrocarbon groups, that is, aliphatic (which may be saturated or unsaturated, linear or branched, e.g., alkyl or alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl) substituents, and aromatic (including aliphatic- and alicyclic-substituted aromatic) substituents, as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g., two substituents together form a ring);

(ii) substituted hydrocarbon groups, that is, substituents containing non-hydrocarbon groups which, in the context of this invention, do not alter the predominantly hydrocarbon nature of the substituent (e.g., halo (e.g. chloro, fluoro or bromo), hydroxy, alkoxy (e.g. Ci to C4 alkoxy), keto, acyl, cyano, mercapto, amino, amido, nitro, nitroso, sulfoxy, nitryl and carboxy); (iii) hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulphur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

In some embodiments m is 0 and the additive of the present invention may be formed from an alcohol of formula R ¹ OH. In such embodiments R ¹ is an optionally substituted hydrocarbyl group. Preferably R ¹ is an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group.

In some preferred embodiments R ¹ is an optionally substituted hydrocarbyl group having at least 4 carbon atoms. Preferably R ¹ is an optionally substituted hydrocarbyl group having 5 to 200 carbon atoms, suitably 6 to 50 carbon atoms, preferably 8 to 30 carbon atoms.

R ¹ may be an optionally substituted alkyl, alkenyl or aryl group having at least 5 carbon atoms.

In some embodiments R ¹ is an optionally substituted Cs to C200 alkyl or alkenyl group, preferably a Ce to C50 alkyl or alkenyl group, preferably a Cs to C30 alkyl or alkenyl group.

R ¹ may be substituted with one or more groups selected from halo (e.g. chloro, fluoro or bromo), nitro, hydroxy, mercapto, sulfoxy, amino, nitryl, acyl, carboxy, alkyl (e.g. Ci to C4 alkyl), alkoxyl (e.g. Ci to C4 alkoxy), amido, keto, sulfoxy and cyano.

In some embodiments R ¹ has at least 6 carbon atoms. R ¹ may have more than 8 carbon atoms. In some embodiments R ¹ may have more than 10 carbon atoms, for example more than 12 carbon atoms, more than 14 carbon atoms or more than 16 carbon atoms.

In some embodiments R ¹ has less than 30 carbon atoms, preferably less than 28 carbon atoms, suitably less than 26 carbon atoms.

In some preferred embodiments R ¹ is an alkyl or alkenyl group having 6 to 50 carbon atoms, preferably 8 to 30 carbon atoms.

Preferably R ¹ is an unsubstituted alkyl or alkenyl group. In some preferred embodiments R ¹ is an unsubstituted alkenyl group. R ¹ may be straight chained or branched. In some embodiments R ¹ is an unsubstituted straight chained or branched alkyl or alkenyl group, having 4 to 50 carbon atoms, preferably 6 to 30 carbon atoms.

In some embodiments R ¹ is an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group having less than 20 carbon atoms, suitably less than 16 carbon atoms.

In some embodiments R ¹ is an alkyl, alkenyl, aryl, alkaryl or aralkyl group having 6 to 16 carbon atoms.

In some embodiments R ¹ is an unsubstituted alkyl, aryl, alkaryl or aralkyl group having less than 16 carbon atoms.

In some embodiments R ¹ is an unsubstituted alkyl, aryl, alkaryl or aralkyl group having less than 12 carbons, suitably less than 10 carbon atoms.

In some embodiments R ¹ is an alkaryl group.

In one embodiment R ¹ is benzyl.

In some embodiments R ¹ is an alkyl group, preferably an unsubstituted alkyl group having 6 to 50, preferably 8 to 30 carbon atoms, for example 12 to 24 carbon atoms.

In some embodiments R ¹ is a group CH3(CH2)x wherein x is from 4 to 23, preferably from 9 to 19.

In some preferred embodiments, R ¹ is a C12 to C alkyl group.

R ¹ may be a straight chain, branched or cyclic alkyl group.

Suitable alcohols R ¹ OH for use herein include hexanol, octanol, nonanol, decanol, dodecanol, tetradecanol, cetyl alcohol, stearyl alcohol, 2-ethyl-1 -butanol, 2-ethyl-1 -hexanol, 2-ethyl-1- heptanol, 2-propylheptanol, 2-ethyl-1 -decanol, 2-hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl-1- dodecanol, 2-octyl-1 -dodecanol, 2-decyl-1 -tetradecanol, isotridecanol, cyclohexanol, cyclooctanol, and benzyl alcohol.

In some embodiments R ¹ is an alkenyl group, preferably an unsubstituted alkenyl group having 5 to 36 carbon atoms, more preferably 10 to 30 carbon atoms, suitably 10 to 24 carbon atoms. R ¹ may be a straight chain, branched or cyclic alkenyl group. Suitable alkenyl alcohols include citronellol, oleyl alcohol, 9-decen-1-ol, cis-3-hexen-1-ol, trans-2-hexen-1-ol, 5-hexen-1-ol, 6- methyl-5-hepten-2-ol, 1-octen-3-ol, trans-2-octen-1-ol and 10-undecen-1-ol.

In some embodiments, the alkenyl alcohol is obtainable from a naturally occurring fatty acid, for example by chemical reduction. Such materials may comprise mixtures of alkenyl alcohols. Examples include oleyl alcohol, linoleyl alcohol, and fatty alcohols derived from fatty acids, for example tall oil, coconut oil or palm kernel oil fatty acids.

In some embodiments, the alkenyl alcohol may be derived from terpenes. Examples of such alkenyl alcohols include linalool, fenchyl alcohol, terpineol, borneol, isoborneol, citrol, geraniol, citronellol, phytol and nerol.

In some preferred embodiments, the alcohol is a C alcohol, for example stearyl alcohol or oleyl alcohol.

In some embodiments oleyl alcohol is especially preferred.

In some preferred embodiments, R ¹ is a branched, saturated alkyl group, such as a branched, saturated Cs to C24 alkyl group.

Suitable branched alcohols for use herein include 2-ethyl-1 -butanol, 2-ethyl-1 -hexanol, 2-ethyl- 1 -heptanol, 2-propylheptanol, 2-ethyl-1 -decanol, 2-hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl- 1 -dodecanol, 2-octyl-1 -dodecanol, 2-decyl-1 -tetradecanol and isotridecanol.

In some embodiments 2-ethyl hexanol is especially preferred.

In some embodiments R ¹ is a short chain hydrocarbyl group, for example a Ci to C3 alkyl group. In such embodiments the alcohol may be selected from methanol, ethanol, propanol and isopropanol.

In some embodiments a mixture of alcohols may be used. In some embodiments a mixture of alcohols including at least one short chain alcohol having 1 to 3 carbon atoms and at least one alcohol having 4 or more carbon atoms may be used, for example at least one alcohol having 1 to 3 carbon atoms and at least one alcohol having 6 to 50 or 8 to 30 carbon atoms. In one preferred embodiment a mixture of isopropanol and 2-ethyl hexanol is used. Preferably the molar ratio of isopropanol to 2-ethyl hexanol is from 4:1 to 1 :4.

The skilled person will appreciate that commercial sources of alcohols of formula R ¹ OH will often contain mixtures of compounds, for example mixtures of isomers and/or mixtures of homologues.

Some suitable alcohols for use herein include mixed C to Cw monounsaturated alcohols, known as cetostearyl alcohol.

In some embodiments m is not 0 and the additive of the present invention may suitably be formed from an alcohol of formula H-(OR ² ) _m -OR ¹ .

In such embodiments R ¹ is hydrogen or an optionally substituted hydrocarbyl group. R ¹ may be as defined above.

R ² is an optionally substituted arylene or alkylene group. Preferably R ² is an optionally substituted alkylene group.

Preferably R ² is an unsubstituted alkylene group.

Preferably R ² is an optionally substituted alkylene group having 1 to 50 carbon atoms, preferably 1 to 40 carbon atoms, preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, suitably 1 to 10 carbon atoms, for example 2 to 6 or 2 to 4 carbon atoms.

Preferably R ² is an unsubstituted alkylene group having 1 to 50 carbon atoms, preferably 1 to 20, more preferably 1 to 10, suitably 2 to 6, for example 2 to 4 carbon atoms. R may be straight chained or branched.

Suitably R ² may be an ethylene, propylene, butylene, pentylene, or hexylene group. When R ² has more than 2 carbon atoms any isomer may be present. Preferably R ² is an ethylene or a propylene group, most preferably a propylene group.

R ² may comprise a mixture of isomers. For example when R ² is propylene, the polyhydric alcohol may include moieties -CH2CH(CH3)- and -CH(CH3)CH2- in any order within the chain.

R ² may comprise a mixture of different groups for example ethylene, propylene or butylene units. Block copolymer units are preferred in such embodiments. R ² is preferably an ethylene, propylene or butylene group. R may be an n-propylene or n- butylene group or an isopropylene or isobutylene group. For example R ² may be -CH2CH2-, - CH ₂ CH(CH ₃ )-, -CH ₂ C(CH ₃ ) ₂ , -CH(CH ₃ )CH(CH ₃ )- or -CH ₂ CH(CH ₂ CH ₃ )-.

Preferably R ² is ethylene or propylene. More preferably R ² is -CH2CH2- or -CH(CH ₃ )CH2-. Most preferably R ² is -CH(CH ₃ )CH ₂ -.

In some embodiments m is at least 1. Preferably n is from 1 to 200, preferably from 1 to 50, more preferably from 1 to 30, more preferably from 1 to 24, preferably from 1 to 20, suitably from 1 to 16.

In some preferred embodiments m is from 8 to 20.

The skilled person will appreciate that commercial sources of alcohols of formula H-(OR ² ) _m - OR ¹ often contain mixtures of compounds, for example in which m may be between 10 and 20.

In some preferred embodiments in which m is not 0, R ¹ is an optionally substituted alkyl, alkenyl or aryl group, suitably an optionally substituted alkyl or alkenyl group. Preferably R ¹ has from 4 to 50 carbon atoms, preferably 4 to 40 carbon atoms, more preferably from 10 to 30 carbon atoms. R ¹ may be straight chain or branched. Preferably R ¹ is straight chain.

In some embodiments R ¹ is a substituted alkyl or alkenyl group, suitably a substituted alkyl group. Suitable substituents are hydroxy and ester groups. In some embodiments R ¹ is a 2- hydroxy alkyl, alkenyl or aryl group.

Suitably R ¹ is an unsubstituted alkyl or alkenyl group. Preferably R ¹ is an alkyl group, preferably an unsubstituted alkyl group.

Suitably R ¹ is selected from an alkyl group having from 1 to 40, preferably 6 to 30, more preferably 10 to 20 carbon atoms.

In some embodiments R ¹ is a C4 to C30 alkyl or alkenyl group, m is not 0 and the additive of the present invention is prepared from an alkyl or alkenyl ether of a polyhydric alcohol, for example an ether of a polyethylene glycol, a polypropylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol or tripropylene glycol. Some especially preferred alcohols for use in preparing the additive of the present invention are of the formula CH3(CH2)aO(CH2CH(CH3)O)bH or an isomer thereof wherein a is from 4 to 30, preferably from 8 to 20, more preferably from 10 to 15, and b is from 1 to 30, preferably from 5 to 25, more preferably from 10 to 20. In one preferred embodiment a is 13 and b is 15.

In some embodiments m is 1 , R ¹ is hydrogen and R ² is selected from ethylene, propylene and 2-hydroxypropylene. Thus the alcohol may be a short chain polyol having 2 or 3 carbon atoms, preferably selected from ethylene glycol, propylene glycol and glycerol.

The alcohol of formula H-(OR ² ) _m -OR ¹ may be selected from:

Short chain alcohols having 1 to 3 carbon atoms;

Short chain polyols having 2 or 3 carbon attorns; alkanols of formula CH3(CH2)aOH or an isomer thereof wherein a is from 4 to 23; branched or cyclic alkyl alcohols in which m is 0 and R ¹ has 6 to 24 carbon atoms; alkenyl alcohols in which n is 0 and R ¹ has 6 to 24 carbon atoms; glycol ethers in which m is not 0; and mixtures thereof.

The alcohol of formula H-(OR ² ) _m -OR ¹ may be selected from: alkanols of formula CH3(CH2)aOH or an isomer thereof wherein a is from 4 to 23; branched or cyclic alkyl alcohols in which m is 0 and R ¹ has 6 to 24 carbon atoms; alkenyl alcohols in which n is 0 and R ¹ has 6 to 24 carbon atoms; and glycol ethers in which m is not 0.

Preferred alkanols of formula CH3(CH2)aOH include stearyl alcohol, tetradecanol, cetyl alcohol, octanol, hexanol, nonanol, decanol, dodecanol.

Preferred branched or cyclic alkyl alcohols in which m is 0 include cyclohexanol, cyclooctanol, 2-propylheptanol, 2-ethyl-1 -hexanol, 2-ethyl-1 -heptanol, 2-propylheptanol, 2-ethyl-1 -decanol, 2-ethyl-1 -butanol, 2-hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl-1 -dodecanol, 2-octyl-1- dodecanol, 2-decyl-1 -tetradecanol and isotridecanol.

Preferred alkenyl alcohols in which m is 0 include citronellol, oleyl alcohol, 9-decen-1-ol, cis-3- hexen-1-ol, trans-2-hexen-1-ol, 5-hexen-1-ol, 6-methyl-5-hepten-2-ol, 1-octen-3-ol, trans-2- octen-1-ol and 10-undecen-1-ol. Preferred glycol ethers in which m is not 0 include compounds of formula CH3(CH2)aO(CH2CH(CH3)O)bH or an isomer thereof wherein a is from 10 to 15, and b is from 10 to 20.

The additive of the present invention may be prepared by polymerising a dicarboxylic acid and then esterifying some or all of the acid groups on the polymeric acid.

Preferably the additive of the present invention is prepared by reacting a dicarboxylic acid compound and an alcohol and then polymerising the resultant ester. In some embodiments the dicarboxylic acid and alcohol are preferably reacted in a molar ratio of from 15:1 to 1 :15, suitably from 10:1 to 1 :10, preferably from 5:1 to 1 :5, more preferably from 2:1 to 1 :2, for example from 1.5:1 to 1 :1.5 or from 1.2:1 to 1 :1.2. For the avoidance of doubt, reference to molar ratios are to the number of moles of each molecule reacted, not the number of functional groups reacted. Thus a 1 :1 molar ratio refers to one mole of dicarboxylic acid compound reacting with one mole of alcohol, regardless of the number of acid/hydroxy groups present in each compound.

In some especially preferred embodiments the dicarboxylic acid compound and the alcohol are reacted in an approximately 1 :1 molar ratio. By “approximately” unless otherwise stated herein we mean within 10% of the values specified.

In some preferred embodiments the dicarboxylic acid compound and the alcohol are reacted in a molar ratio of at least 1 :1.5, preferably at least 1 :1.6, more preferably at least 1 :1.7, suitably at least 1 :1 .8, for example at least 1 :1 .9. The dicarboxylic acid compound and the alcohol may be reacted in a ratio of from 1 :1 .5 to 1 :2.5, for example from 1 :1 .8 to 1 :2.2.

In some preferred embodiments the dicarboxylic acid compound and the alcohol are reacted in approximately 1 :2 ratio. In such embodiments substantially all of the acid groups are esterified.

The dicarboxylic acid compound and the alcohol react to form an ester. In some preferred embodiments the dicarboxylic acid and the alcohol are reacted in an approximately 1 :1 molar ratio. The reaction product of the dicarboxylic acid and the alcohol may comprise a mixture of compounds. Preferably the reaction product comprises predominantly monoesters. However some diester may also be present, along with unreacted diacid. When x y, two different monoesters can be formed even when a single alcohol is used. Mixtures of alcohols can also be used leading to further mixtures in the product. The reaction product obtained following reaction of the dicarboxylic acid and the alcohol is then polymerised.

According a fourth aspect of the present invention there is provided a method of preparing an additive of formula (I):

(i); the method comprising the steps of:

(i) reacting dicarboxylic acid of formula (II): or an anhydride thereof with an alcohol; and

(ii) polymerising the reaction product obtained in step (i); wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

According to a fifth aspect of the present invention there is provided a method of preparing a fuel composition, the method comprising dosing into a fuel a polymeric additive of formula (I):

(i); wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

Preferably the method of the fifth aspect involves the steps of: (i) reacting a dicarboxylic acid of formula (II): or anhydride thereof with an alcohol;

(ii) polymerising the reaction product defined in step (ii) to provide an additive of formula (I); (I); and

(iii) dosing the additive into a fuel; wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen.

Preferred features of the fourth and fifth aspects are as defined in relation to the first, second and third aspects.

Furthermore preferred features of the invention will now be described.

In the polymeric additive of the present invention of formula (I), at least 10% of all R groups are not hydrogen. Thus at least 10% of all acid residues in the molecule are esterified. For the avoidance of doubt, references to the number of groups which are esterified is a molar ratio rather than a weight ratio.

Preferably at least 15% of all R groups in the additive of formula (I) are not hydrogen, more preferably at least 20%, suitably at least 25%, more preferably at least 30%, for example at least 35% or at least 40% of all R groups in the additive of formula (I) are not hydrogen.

Up to 100% of all R groups may not be hydrogen, for example up to 95%, suitably up to 90%, preferably up to 80%, more preferably up to 75%, for example up to 70%, up to 65% or up to 60% of all R groups in the additive of formula (I) are not hydrogen.

R groups that are not hydrogen are an optionally substituted hydrocarbyl group as previously defined herein.

In some preferred embodiments from 30 to 70% of all R groups in the additive of formula (I) are not hydrogen, preferably from 40 to 60%, more preferably from 45 to 55%.

In such preferred embodiments approximately half of all R groups in the additive of formula (I) are not hydrogen. Thus approximately half of the acid groups present in the additive of formula (I) are esterified.

In such preferred embodiments in which the additive of formula (I) is prepared by polymerising the reaction product of a dicarboxylic acid and an alcohol, the additive is prepared by polymerising predominantly monoesters. In such embodiments in the structure shown in formula (I), in each monomer unit preferably one R group is hydrogen and the other is an optionally substituted hydrocarbyl group.

In some preferred embodiments at least 90% of all R groups in the additive of formula (I) are not hydrogen, preferably at least 95%, more preferably at least 99%.

In such preferred embodiments substantially all R groups in the additive of formula (I) are not hydrogen. Thus substantially of the acid groups present in the additive of formula (I) are esterified.

In such embodiments in the structure shown in formula (I), in each monomer unit each R groups is an optionally substituted hydrocarbyl group.

Suitable conditions for carrying out the esterification reaction of step (i) of the method of the fourth aspect will be known to those skilled in the art. In some preferred embodiments an acid catalyst is used.

Step (ii) of the method of the fourth aspect and a preferred embodiment of the fifth aspect involves polymerising the reaction product obtained in step (i).

Polymerisation is suitably achieved by the addition of a radical initiator. Suitably radical initiators will be known to those skilled in the art and include: azo compounds, for example azobisisobutyronitrile (AIBN); hydroperoxides, for example cumene hydroperoxides, tertiary butyl hydroperoxide, methyl ethyl ketone hydroperoxides; peroxides, for example di-tertiary butyl peroxide, tert-Butyl peroxypivalate, di cumyl peroxide, benzoyl peroxide 1 ,1 ' azobis(cyclohexanecarbonitrile) (ABCN); and persulfates, for example ammonium persulfate, sodium persulfate or potassium persulfate.

Suitable amounts of radical initiator and reaction conditions will be known to the person skilled in the art.

The additives of the invention are preferably the polymerised reaction product of a carboxylic acid and an alcohol.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof; and an alcohol of formula R ¹ OH wherein R ¹ is an optionally substituted hydrocarbyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof; and an alcohol of formula R ¹ OH wherein R ¹ is a (preferably branched) alkyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof; and an alcohol of formula R ¹ OH wherein R ¹ is an optionally substituted alkyl or alkenyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) (preferably wherein x+y is less than 6) or an anhydride thereof; and an alcohol of formula R ¹ OH wherein R ¹ is an alkenyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof; and an alcohol of formula H-(OR ² ) _m -OR ¹ wherein n is from 1 to 24, R ² is ethylene, propylene or isopropylene, and R ¹ is an unsubstituted alkyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) (preferably wherein x+y is less than 6) or an anhydride thereof; and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl group having 1 to 3 carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of a dicarboxylic acid compound of formula (II) or an anhydride thereof; and an alcohol of formula H-(OR ² ) _m -OR ¹ wherein n is 1 , R ² is ethylene, propylene or 2-hydroxypropylene, and R ¹ is hydrogen.

In some embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof; and an alcohol selected from 2-ethyl-1 -butanol, 2- ethyl-1 -hexanol, 2-ethyl-1 -heptanol, 2-propylheptanol, 2-ethyl-1 -decanol, 2-hexyl-1 -decanol, 2- octyl-1 -decanol, 2-hexyl-1 -dodecanol, 2-octyl-1 -dodecanol, 2-decyl-1 -tetradecanol and isotridecanol. In some embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof; and an alcohol of formula H-(OR ² ) _m -OR ¹ wherein m is from 1 to 24, R is ethylene, propylene or isopropylene, and R ¹ is an unsubstituted alkyl group having 6 to 30, preferably 6 to 24, carbon atoms.

In some embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof; and an alkenyl alcohol selected from citronellol, oleyl alcohol, 9-decen-1-ol, cis-3-hexen-1-ol, trans-2-hexen-1-ol, 5-hexen-1-ol, 6-methyl-5-hepten-2- ol, 1-octen-3-ol, trans-2-octen-1-ol and 10-undecen-1-ol.

In some embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof; and an alkenyl alcohol selected from methanol, ethanol, propanol, isopropanol, ethylene glycol, propylene glycol and glycerol.

In some embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof; and citronellol or oleyl alcohol (preferably oleyl alcohol).

In some especially preferred embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof and 2-ethylhexanol.

In some especially preferred embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof and a mixture of isopropanol and 2-ethylhexanol.

In preferred embodiments the additive of the present invention is the polymerised reaction product of itaconic acid or an anhydride thereof and 2-ethylhexanol wherein the polymer has a weight average molecular weight of from 2000 to 50000, preferably from 4000 to 30000, more preferably from 5000 to 20000, for example from 6000 to 15000, suitably from 8000 to 12000.

Weight average molecular weight may be measured by gel permeation chromatography.

Suitably the polymeric additive of the present invention is present in the diesel fuel composition in an amount of at least 0.1 ppm, preferably at least 1 ppm, more preferably at least 5 ppm, suitably at least 10 ppm, preferably at least 15 ppm. Suitably the polymeric additive of the present invention is present in the fuel composition in an amount of less than 10000 ppm, preferably less than 1000 ppm, preferably less than 500 ppm, preferably less than 300 ppm, for example less than 250 ppm or less than 200 ppm, or less than 150 ppm.

Suitably the polymeric additive is present in the fuel composition in an amount of from 1 to 10000 ppm, preferably 5 to 1000 ppm, more preferably 10 to 500 ppm or 10 to 200 ppm.

In this specification any reference to ppm is to parts per million by weight. The values given in parts per million (ppm) for treat rates denote the amount of active agent present in the composition and do not include any diluent, carriers or other materials that may be present.

The diesel fuel compositions of the present invention may comprise a mixture of two or more polymeric additives as defined herein. In such embodiments the above amounts refer to the total amounts of all such additives present in the composition.

The polymeric additive compounds may be prepared from a mixture of monomers including mixtures formed by reacting a mixture of different alcohols with a dicarboxylic acid compound and/or mixtures formed by reacting an alcohol with a mixture of dicarboxylic acid compounds and/or compounds formed by reacting a mixture of alcohols with a mixture of dicarboxylic acid compounds.

The skilled person will appreciate that even when prepared from a single acid and a single alcohol, polymers will contain a mixture of compounds.

The use of mixtures may arise due to the availability of starting materials or a particular mixture may be deliberately selected to use in order to achieve a benefit. For example, a particular mixture may lead to improvements in handling, a general improvement in performance or a synergistic improvement in performance.

In this specification any reference to “an additive” or “the additive” of the present invention includes embodiments in which mixtures of compounds are present. In embodiments in which two or more compounds are present the mixtures may be present due to a mixture of starting materials being used to prepare the additive compounds. Alternatively and/or additionally two or more pre-formed polymeric additive compounds may be mixed into a fuel composition.

The fuel composition of the first aspect of the present invention may be a diesel fuel composition or a gasoline fuel composition. The additives may be added to the fuel at any convenient place in the supply chain. For example, the additives may be added to fuel at the refinery, at a distribution terminal or after the fuel has left the distribution terminal. If the additive is added to the fuel after it has left the distribution terminal, this is termed an aftermarket application. Aftermarket applications include such circumstances as adding the additive to the fuel in the delivery tanker, directly to a customer’s bulk storage tank, or directly to the end user’s vehicle tank. Aftermarket applications may include supplying the fuel additive in small bottles suitable for direct addition to fuel storage tanks or vehicle tanks.

In some preferred embodiments the fuel composition is a diesel fuel composition.

By diesel fuel we include any fuel suitable for use in a diesel engine either for road use or nonroad use. This includes but is not limited to fuels described as diesel, marine diesel, heavy fuel oil, industrial fuel oil, etc.

The diesel fuel composition used in the present invention may comprise a petroleum-based fuel oil, especially a middle distillate fuel oil. Such distillate fuel oils generally boil within the range of from 110°C to 500°C, e.g. 150°C to 400°C. The diesel fuel may comprise atmospheric distillate or vacuum distillate, cracked gas oil, or a blend in any proportion of straight run and refinery streams such as thermally and/or catalytically cracked and hydro-cracked distillates.

The diesel fuel composition may comprise non-renewable Fischer-Tropsch fuels such as those described as GTL (gas-to-liquid) fuels, CTL (coal-to-liquid) fuels and OTL (oil sands-to-liquid).

The diesel fuel composition may comprise a renewable fuel such as a biofuel composition or biodiesel composition.

The diesel fuel composition may comprise 1st generation biodiesel. First generation biodiesel contains esters of, for example, vegetable oils, animal fats and used cooking fats. This form of biodiesel may be obtained by transesterification of oils, for example rapeseed oil, soybean oil, canola oil, safflower oil, palm oil, corn oil, peanut oil, cotton seed oil, tallow, coconut oil, physic nut oil (Jatropha), sunflower seed oil, used cooking oils, hydrogenated vegetable oils or any mixture thereof, with an alcohol, usually a monoalcohol, usually in the presence of a catalyst.

The diesel fuel composition may comprise second generation biodiesel. Second generation biodiesel is derived from renewable resources such as vegetable oils and animal fats and processed, often in the refinery, using, for example, hydroprocessing such as the H-Bio process developed by Petrobras. Second generation biodiesel may be similar in properties and quality to petroleum based fuel oil streams, for example renewable diesel produced from vegetable oils, animal fats etc. and marketed by ConocoPhillips as Renewable Diesel and by Neste as NExBTL.

The diesel fuel composition may comprise third generation biodiesel. Third generation biodiesel utilises gasification and Fischer-Tropsch technology including those described as BTL (biomass-to-liquid) fuels. Third generation biodiesel does not differ widely from some second generation biodiesel, but aims to exploit the whole plant (biomass) and thereby widens the feedstock base.

The diesel fuel composition may contain blends of any or all of the above diesel fuel compositions.

In some embodiments the diesel fuel composition may be a blended diesel fuel comprising bio-diesel. In such blends the bio-diesel may be present in an amount of, for example up to 0.5%, up to 1 %, up to 2%, up to 3%, up to 4%, up to 5%, up to 10%, up to 20%, up to 30%, up to 40%, up to 50%, up to 60%, up to 70%, up to 80%, up to 90%, up to 95% or up to 99%.

In some embodiments the fuel composition may comprise neat biodiesel.

In some preferred embodiments the fuel composition comprises at least 5 wt% biodiesel.

In some embodiments the fuel composition may comprise a neat GTL fuel.

In some embodiments the fuel composition may comprise a blend of a first generation biodiesel and a second generation biodiesel (or renewable diesel), for example a blend comprising 80 vol% of a first generation biodiesel and 20 vol% of a second generation biodiesel.

In some embodiments the diesel fuel composition may comprise a secondary fuel, for example ethanol. Preferably however the diesel fuel composition does not contain ethanol.

The diesel fuel composition used in the present invention may contain a relatively high sulphur content, for example greater than 0.05% by weight, such as 0.1% or 0.2%.

However, in preferred embodiments the diesel fuel composition has a sulphur content of at most 0.05% by weight, more preferably of at most 0.035% by weight, especially of at most 0.015%. Fuels with even lower levels of sulphur are also suitable such as, fuels with less than 50 ppm sulphur by weight, preferably less than 20 ppm, for example 10 ppm or less.

The diesel fuel composition of the present invention preferably comprises at least 5 wt% biodiesel and less than 50 ppm sulphur.

The diesel fuel composition of the present invention may include one or more further additives such as those which are commonly found in diesel fuels. These include, for example, antioxidants, dispersants, detergents, metal deactivating compounds, wax anti-settling agents, cold flow improvers, cetane improvers, dehazers, stabilisers, demulsifiers, antifoams, corrosion inhibitors, lubricity improvers, dyes, markers, combustion improvers, metal deactivators, odour masks, drag reducers and conductivity improvers. Examples of suitable amounts of each of these types of additives will be known to the person skilled in the art.

In some embodiments the diesel fuel composition of the present invention comprises a corrosion inhibitor. Suitable corrosion inhibitors are commercially available and known to the person skilled in the art.

In some embodiments the diesel fuel composition of the present invention comprises a lubricity improver. Suitable lubricity improvers are commercially available and known to the person skilled in the art. Preferred lubricity improvers for use herein include tall oil fatty acids and ester compounds. Examples of suitable ester compounds include glycerol monooleate and the reaction product of ethylene glycol and an alkenyl substituted succinic anhydride.

In some embodiments the diesel fuel composition of the present invention comprises an antifoam additive. Suitable antifoam additives are commercially available and known to the person skilled in the art.

In some preferred embodiments the diesel fuel composition of the present invention comprises one or more further detergents. Nitrogen-containing detergents are preferred.

The one or more further detergents may be added to the fuel separately to the polymeric additive of formula (I). In some embodiments the one or more further detergents may be dosed into the fuel with the polymeric additive of formula (I) as part of an additive composition.

According to a sixth aspect of the present invention there is provided an additive composition comprising: a polymer of formula (I): wherein n is at least 4, x may be 0 or a positive integer, y may be 0 or a positive integer and each R is independently hydrogen or an optionally substituted hydrocarbyl group provided that at least 10% of all R groups are not hydrogen; one or more further detergents, preferably one or more further nitrogen containing detergents; and a diluent or carrier.

Preferred features of the invention as described in relation to the first to fifth aspects apply as appropriate to the sixth aspects. Further preferred features of all aspects of the invention will now be described.

The one or more further detergents may be selected from:

(i) a quaternary ammonium salt additive;

(ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol;

(iii) the reaction product of a carboxylic acid-derived acylating agent and an amine;

(iv) the reaction product of a carboxylic acid-derived acylating agent and hydrazine;

(v) a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-n- butylamine; (vi) the reaction product of a hydrocarbyl-substituted dicarboxylic acid or anhydride and an amine compound or salt which product comprises at least one amino triazole group;

(vii) a substituted polyaromatic detergent additive; and

(viii) partial esters of substituted succinic acids.

Preferably one or more further detergents are selected from one or more of:

(i) a quaternary ammonium salt additive;

(ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol; and

(iii) the reaction product of a carboxylic acid-derived acylating agent and an amine.

The weight ratio of the additive of the present invention to the nitrogen containing detergent is suitably from 10:1 to 1 :10, preferably 5:1 to 1 :5, preferably from 2:1 to 1 :2.

In some embodiments the diesel fuel composition further comprises (i) a quaternary ammonium salt additive.

The quaternary ammonium salt additive is suitably the reaction product of a nitrogencontaining species having at least one tertiary amine group and a quaternising agent.

The nitrogen containing species may be selected from:

(7) the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group; (y) a Mannich reaction product comprising a tertiary amine group; and

(z) a polyalkylene substituted amine having at least one tertiary amine group.

Examples of quaternary ammonium salt and methods for preparing the same are described in the following patents, which are hereby incorporated by reference, US2008/0307698, US2008/0052985, US2008/0113890 and US2013/031827.

The preparation of some suitable quaternary ammonium salt additives in which the nitrogencontaining species includes component (x) is described in WO 2006/135881 and WO2011/095819.

Component (y) is a Mannich reaction product having a tertiary amine. The preparation of quaternary ammonium salts formed from nitrogen-containing species including component (y) is described in US 2008/0052985.

The preparation of quaternary ammonium salt additives in which the nitrogen-containing species includes component (z) is described for example in US 2008/0113890.

To form the quaternary ammonium salt additive (i) the nitrogen-containing species having a tertiary amine group is reacted with a quaternising agent.

The quaternising agent may suitably be selected from esters and non-esters.

Preferred quaternising agents for use herein include dimethyl oxalate, methyl 2-nitrobenzoate, methyl salicylate and styrene oxide or propylene oxide optionally in combination with an additional acid.

An especially preferred 30dditional quaternary ammonium salt for use”he“ein i” formed by reacting methyl salicylate or dimethyl oxalate with the reaction product of a polyisobutylenesubstituted succinic anhydride having a PIB number average molecular weight of 700 to 1300 and dimethylaminopropylamine.

Other suitable quaternary ammonium salts include quaternised terpolymers, for example as described in US2011/0258917; quaternised copolymers, for example as described in US2011/0315107; and the acid-free quaternised nitrogen compounds disclosed in US2012/0010112. Further suitable quaternary ammonium compounds for use in the present invention include the quaternary ammonium compounds described in the applicants copending applications WO2011095819, WO2013/017889, WO2015/011506, WO2015/011507, WO2016/016641 and PCT/GB2016/052312.

In some especially preferred embodiments the diesel fuel composition comprises a quaternary ammonium salt additive (ia) which is the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group; wherein each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes on average at least 1 .2 succinic acid moieties.

Preferred hydrocarbyl-based substituents are polyisobutenes. Such compounds are known to the person skilled in the art.

Preferred hydrocarbyl substituted succinic acid derived acylating agents for use in preparing additive (ia) are polyisobutenyl substituted succinic anhydrides or PIBSAs. Especially preferred PIBSAs are those having a PIB molecular weight (Mn) of from 300 to 2800, preferably from 450 to 2300, more preferably from 500 to 1300.

The hydrocarbyl substituted succinic acid derived acylating agent is suitably prepared by reacting maleic anhydride with an alkene, for example a polyisobutene. The product obtained (such as a PIBSA) still includes a double bond. The maleic anhydride is present in the resultant molecule as a succinic acid moiety.

The monomaleated PIBSA may have the structure (A) or (B):

(7) (B) The double bond in the monomaleated product can react with a further molecule of maleic anhydride to form a bismaleated PIBSA having the structure I or (D):

Thus it is possible to provide a hydrocarbyl group which is substituted with more than one succinic acid moiety. In such embodiments each molecule of the hydrocarbyl substituted succinic acid derived acylating agent includes more than one succinic acid moiety.

The skilled person will appreciate that the additives typically comprise mixtures of compounds and will be prepared from a mixture of monomaleated and bismaleated PIBSAs. The PIBSAs may be defined in terms of their level of bismaleation.

One way in which this may be determined is by calculating the average number of succinic acid moieties per molecule of acylating agent.

A monomaleated PIBSA has one succinic acid moiety per module.

A bismaleated PIBSA has two succinic acid moieties per molecule.

A mixture comprising monomaleated PIBSA and bismaleated PIBSA in a 1 :1 molar ratio would comprise an average of 1 .5 succinic acid moieties per molecule of PIBSA.

The present invention relates in particular to the use of quaternary ammonium salts derived from hydrocarbyl substituted acylating agents which include an average of at least 1 .2 succinic acid moieties per molecule.

As the skilled person will appreciate, a single molecule cannot have 1 .2 succinic acid moieties. What is meant by at least 1 .2 succinic acid moieties is the mean number of succinic acid moieties per molecule of acylating agent as the sum of all the succinic acid moieties present in a sample divided by the total number of molecules of acylating agent having one or more succinic acid moieties present in the sample.

Preferably the hydrocarbyl substituted succinic acid derived acylating agent comprises on average at least 1.21 succinic acid moieties per molecule, more preferably at least 1.22 succinic acid moieties per molecule.

In some embodiments the hydrocarbyl substituted succinic acid derived acylating agent may comprise at least 1 .23 or at least 1 .24 succinic acid moieties per molecule.

In some embodiments the hydrocarbyl substituted succinic acid derived acylating agent may comprise at least 1 .25, at least 1 .26 or at least 1 .27 succinic acid moieties per molecule.

In some embodiments the hydrocarbyl substituted succinic acid derived acylating agent may comprise at least 1 .28, at least 1 .29 or at least 1 .30 succinic acid moieties per molecule.

By succinic acid moiety we mean to include residues of succinic acid present in diacid or anhydride form.

In some embodiments the quaternary ammonium compounds are the quaternised reaction product of a fatty acid (for example oleic acid) and dimethylaminoproyl amine.

The hydrocarbyl substituted succinic acid derived acylating agent is reacted with a compound able to react with said acylating agent and which includes a tertiary amine group. The tertiary amine group is quaternised to provide the quaternary ammonium salt additive.

Preferably the compound able to react with hydrocarbyl substituted succinic acid derived acylating agent and which includes a tertiary amine group is an amine of formula I or (D):

R ² R ²

N - X - NHR ⁴ N - X - [O(CH ₂ ) _m ] _n OH

R ³ R ³

(C) (D) wherein R ² and R ³ are the same or different alkyl, alkenyl, aryl, alkaryl or aralkyl groups having from 1 to 22 carbon atoms; X is a bond or an optionally substituted alkylene group having from 1 to 20 carbon atoms; n is from 0 to 20; m is from 1 to 5; and R ⁴ is hydrogen or a Ci to C22 alkyl group.

When a compound of formula I is used, R ⁴ is preferably hydrogen or a Ci to Cw alkyl group, preferably a Ci to Cw alkyl group, more preferably a Ci to Ce alkyl group. When R ⁴ is alkyl it may be straight chained or branched. It may be substituted for example with a hydroxy or alkoxy substituent. Preferably R ⁴ is not a substituted alkyl group. More preferably R ⁴ is selected from hydrogen, methyl, ethyl, propyl, butyl and isomers thereof. Most preferably R ⁴ is hydrogen.

When a compound of formula (D) is used, m is preferably 2 or 3, most preferably 2; n is preferably from 0 to 15, preferably 0 to 10, more preferably from 0 to 5. Most preferably n is 0 and the compound of formula (D) is an alcohol.

Preferably the hydrocarbyl substituted acylating agent is reacted with a diamine compound of formula I.

Examples of compounds of formula I suitable for use herein include 1-aminopiperidine, 1-(2- aminoethyl)piperidine, 1- (3-aminopropyl)-2-pipecoline, 1-methyl-(4-methylamino)piperidine, 4- (1 -py rro lid iny I) pi pe rid i n e , 1 -(2-aminoethyl)pyrrolidine, 2-(2-aminoethyl)-1 - methylpyrrolidine, N,N-diethylethylenediamine, N,N-dimethylethylenediamine, N,N-dibutylethylenediamine, N,N- diethyl-l,3-diaminopropane, N,N-dimethyl-1 ,3-diaminopropane, N,N,N’- trimethylethylenediamine, N,N-dimethyl-N’-ethylethylenediamine, N,N-diethyl-N’- methylethylenediamine, N,N,N’- triethylethylenediamine, 3-dimethylaminopropylamine, 3- diethylaminopropylamine, 3-dibutylaminopropylamine, N,N,N’-trimethyl- 1 ,3- propanediamine, N,N,2,2-tetramethyl-l,3-propanediamine, 2-amino-5-diethylaminopentane, N,N,N’,N’- tetraethyldiethylenetriamine, 3,3’-diamino-N-methyldipropylamine, 3,3’-iminobis(N,N- dimethylpropylamine), 1-(3-aminopropyl)imidazole and 4-(3-aminopropyl)morpholine, 1-(2- aminoethyl)piperidine, 3,3-diamino-N-methyldipropylamine, 3,3-aminobis(N,N- dimethylpropylamine), 3-(2-(dimethylamino)ethoxy) propylamine, or combinations thereof.

In some preferred embodiments the compound of formula I is selected from from N,N- dimethyl-1 ,3-diaminopropane, N,N-diethyl-1 ,3- diaminopropane, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dibutylethylenediamine, 3-(2-(dimethylamino)ethoxy) propylamine, or combinations thereof. Examples of compounds of formula (D) suitable for use herein include alkanolamines including but not limited to triethanolamine, N,N-dimethylaminopropanol, N,N-diethylaminopropanol, N,N-diethylaminobutanol, triisopropanolamine, 1-[2-hydroxyethyl]piperidine, 2-[2- (dimethylamine)ethoxy]-ethanol, N-ethyldiethanolamine, N-methyldiethanolamine, N- butyldiethanolamine, N,N-diethylaminoethanol, N,N-dimethyl amino- ethanol, 2-dimethylamino- 2-methyl-1 -propanol, N,N,N’-trimethyl-N’-hydroxyethyl-bisaminoethylether; N,N-bis(3- dimethylaminopropyl)-N-isopropanolamine ; N-(3-dimethylaminopropyl)-N,N- diisopropanolamine ; N’-(3-(dimethylamino)propyl)-N,N-dimethyl 1 ,3-propanediamine ; 2-(2- dimethylaminoethoxy)ethanol, and N,N,N’-trimethylaminoethylethanolamine.

In some preferred embodiments the compound of formula (D) is selected from Triisopropanolamine, 1-[2-hydroxyethyl]piperidine, 2-[2-(dimethylamine)ethoxy]-ethanol, N- ethyldiethanolamine, N-methyldiethanolamine, N-butyldiethanolamine, N,N- diethylaminoethanol, N,N-dimethylaminoethanol, 2-dimethylamino-2-methyl-1 -propanol, or combinations thereof.

An especially preferred compound of formula (C) is N,N-dimethyl-1 ,3-diaminopropane (dimethylaminopropylamine) .

When a compound of formula (D) is reacted with a succinic acylating agent the resulting product is a succinic ester. When a succinic acylating agent is reacted with a compound of formula I in which R ⁴ is hydrogen the resulting product may be a succinimide or a succinamide. When a succinic acylating agent is reacted with a compound of formula I in which R ⁴ is not hydrogen the resulting product is an amide.

To form the quaternary ammonium salt additive (ai) the hydrocarbyl substituted succinic acid derived acylating agent is reacted with a compound able to react with said acylating agent and which includes a tertiary amine group. This reaction product is then quaternised by reaction with a quaternising agent.

The reaction product of the acylating agent and compound which includes a tertiary amine group is preferably reacted with at least one molar equivalent of quaternising agent per mole of tertiary amine group present in the reaction product.

Preferably the reaction product of the acylating agent and compound which includes a tertiary amine group is reacted with more than one molar equivalent of quaternising agent per mole of tertiary amine group present in the reaction product, preferably at least 1.2 molar equivalents of quaternising agent per mole of tertiary amine group, more preferably at least 1 .5 molar equivalents of quaternising agent, suitably at least 1.7 molar equivalents of quaternising agent, for example at least 1.9 molar equivalents of quaternising agent.

Preferably the reaction product of the acylating agent and compound which includes a tertiary amine group is reacted with two or more molar equivalents of quaternising agent per mole of tertiary amine group present in the reaction product, preferably at least 2.1 molar equivalents of quaternising agent.

In some embodiments the reaction product of the acylating agent and compound which includes a tertiary amine group is reacted with more than 2.2 molar equivalents of quaternising agent per mole of tertiary amine group present in the reaction product, for example from 2.3 to 4 molar equivalents, from 2.3 to 3 molar equivalents, or from 2.3 to 2.7 or from 2.5 to 3 molar equivalents.

Any suitable quaternising agent may be used. The quaternising agent may suitably be selected from esters and non-esters.

Suitable quaternising agents include esters of a carboxylic acid, dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, hydrocarbyl substituted epoxides optionally in combination with an acid, alkyl halides, alkyl sulfonates, sulfones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, alkyl nitrites, alkyl nitrates, hydroxides, N-oxides, chloroacetic acid or salts thereof, or mixtures thereof.

In some preferred embodiments, quaternising agents used to form the quaternary ammonium salt additives of the present invention are esters.

Preferred ester quaternising agents are compounds of formula I: in which R is an optionally substituted alkyl, alkenyl, aryl or alkylaryl group and R1 is a C1 to C22 alkyl, aryl or alkylaryl group. The compound of formula I is suitably an ester of a carboxylic acid capable of reacting with a tertiary amine to form a quaternary ammonium salt. Suitable quaternising agents include esters of carboxylic acids having a pKa of 3.5 or less.

The compound of formula I is preferably an ester of a carboxylic acid selected from a substituted aromatic carboxylic acid, an a-hydroxycarboxylic acid and a polycarboxylic acid.

In some preferred embodiments the compound of formula I is an ester of a substituted aromatic carboxylic acid and thus R is a substituted aryl group.

Preferably R is a mono-substituted aryl group. Preferably R is an ortho substituted aryl group. Suitably R is substituted with a group selected from OH, NH2, NO2 or COOMe. Preferably R is substituted with an OH or NH2 group. Suitably R is a hydroxy substituted aryl group. Most preferably R is a 2-hydroxyphenyl group.

Preferably R ¹ is an alkyl, aralkyl or alkaryl group. R ¹ may be a C1 to C16 alkyl group, preferably a C1 to C10 alkyl group, suitably a C1 to C8 alkyl group. R ¹ may be C7 to C16 aralkyl or alkaryl group, preferably a C7 to C10 aralkyl or alkaryl group. R ¹ may be methyl, ethyl, propyl, butyl, pentyl, benzyl or an isomer thereof. Preferably R ¹ is benzyl or methyl. Most preferably R ¹ is methyl.

Especially preferred compounds of formula (III) are lower alkyl esters of salicylic acid such as methyl salicylate, ethyl salicylate, n and I propyl salicylate, and butyl salicylate, preferably methyl salicylate.

In some embodiments the compound of formula I is an ester of an a-hydroxycarboxylic acid. In such embodiments the compound has the structure: wherein R7 and R8 are the same or different and each is selected from hydrogen, alkyl, alkenyl, aralkyl or aryl. Compounds of this type suitable for use herein are described in EP 1254889.

In some embodiments the compound of formula I is an ester of a polycarboxylic acid. In this definition we mean to include dicarboxylic acids and carboxylic acids having more than 2 acidic moieties. In such embodiments RCOO is preferably present in the form of an ester, that is the one or more further acid groups present in the group R are in esterified form. However embodiments in which not all acid groups are esterified are within the invention. Mixed esters of polycarboxylic acids may also be used. Preferred esters are C1 to C4 alkyl esters.

The ester quaternising agent may be selected from the diester of oxalic acid, the diester of phthalic acid, the diester of maleic acid, the diester of malonic acid or the diester of citric acid. One especially preferred compound of formula (III) is dimethyl oxalate.

In preferred embodiments the compound of formula I is an ester of a carboxylic acid having a pKa of less than 3.5. In such embodiments in which the compound includes more than one acid group, we mean to refer to the first dissociation constant.

The ester quaternising agent may be selected from an ester of a carboxylic acid selected from one or more of oxalic acid, phthalic acid, salicylic acid, maleic acid, malonic acid, citric acid, nitrobenzoic acid, aminobenzoic acid and 2, 4, 6-trihydroxybenzoic acid.

Preferred ester quaternising agents include dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

In some preferred embodiments, quaternising agents used to form the quaternary ammonium salt additives of the present invention are esters selected from dimethyl oxalate, methyl 2- nitrobenzoate and methyl salicylate, preferably dimethyl oxalate and methyl salicylate.

Suitable non-ester quaternising agents include dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, hydrocarbyl substituted epoxides optionally in combination with an acid, alkyl halides, alkyl sulfonates, sulfones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, alkyl nitrites, alkyl nitrates, hydroxides, N-oxides, chloroacetic acid or salts thereof, or mixtures thereof.

Suitable hydrocarbyl substituted epoxides have the formula: wherein each of R1 , R2, R3 and R4 is independently hydrogen or a hydrocarbyl group having 1 to 50 carbon atoms. Examples of suitable epoxides include ethylene oxide, propylene oxide, butylene oxide, styrene oxide and stilbene oxide. The hydrocarbyl epoxides are used as quaternising agents optionally in combination with an acid.

The hydrocarbyl substituted succinic acylating agent includes two acyl groups. In some embodiments only one of these groups reacts with the compound of formula (I) or formula (II) to form a compound having an ester or an amide functional group and a free carboxylic acid. In these embodiments if an epoxide is used as the quaternising agent, a separate acid does not need to be added. However in other embodiments an acid for example acetic acid may be used.

Especially preferred epoxide quaternising agents are propylene oxide and styrene oxide, optionally in combination with an additional acid.

Preferred quaternising agents for use herein include dimethyl oxalate, methyl 2-nitrobenzoate, methyl salicylate, chloroacetic acid or a salt thereof, and styrene oxide or propylene oxide optionally in combination with an additional acid.

In some embodiments mixtures of two or more quaternising agents may be used.

To form some preferred quaternary ammonium salt additives (ia) for use in the present invention a compound of formula I is reacted with a compound formed by the reaction of a hydrocarbyl substituted succinic acid acylating agent and an amine of formula I or (D).

Suitably approximately one equivalent of amine is added per succinic acid moiety present in the acylating agent. The ratio of amine used will thus typically depend on the average number of succinic acid moieties present in each molecule of the acylating agent.

An especially preferred quaternary ammonium salt (ia) for use herein is formed by reacting methyl salicylate or dimethyl oxalate with the reaction product of a polyisobutylene-substituted succinic anhydride having a PIB molecular weight of 700 to 1300 and dimethylaminopropylamine; wherein the polyisobutylene-substituted succinic anhydride includes on average at least 1 .2 succinic acid moieties per molecule.

In some embodiments the diesel fuel composition used in the present invention comprises from 1 to 500 ppm, preferably 5 to 250 ppm of the additive of the present invention and from 1 to 500 ppm, preferably 5 to 250ppm of a quaternary ammonium additive (i), preferably a quaternary ammonium additive (ia). In some embodiments the diesel fuel composition comprises further (ii) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol. This Mannich reaction product is suitably not a quaternary ammonium salt.

Preferably the aldehyde component used to prepare the Mannich additive is an aliphatic aldehyde. Preferably the aldehyde has 1 to 10 carbon atoms. Most preferably the aldehyde is formaldehyde.

Suitable amines for use in preparing the Mannich additive include monoamines and polyamines. One suitable monoamine is butylamine.

The amine used to prepare the Mannich additive is preferably a polyamine. This may be selected from any compound including two or more amine groups. Preferably the polyamine is a polyalkylene polyamine, preferably a polyethylene polyamine. Most preferably the polyamine comprises tetraethylenepentamine or ethylenediamine.

The optionally substituted phenol component used to prepare the Mannich additive may be substituted with 0 to 4 groups on the aromatic ring (in addition to the phenol OH). For example it may be a hydrocarbyl-substituted cresol. Most preferably the phenol component is a monosubstituted phenol. Preferably it is a hydrocarbyl substituted phenol. Preferred hydrocarbyl substituents are alkyl substituents having 4 to 28 carbon atoms, especially 10 to 14 carbon atoms. Other preferred hydrocarbyl substituents are polyalkenyl substituents. Such polyisobutenyl substituents having a number average molecular weight of from 400 to 2500, for example from 500 to 1500.

In some embodiments the diesel fuel composition of the present invention comprises from 1 to 500 ppm, preferably 5 to 250ppm of the additive of the present invention and from 1 to 500 ppm, preferably 5 to 250ppm of a Mannich additive (ii).

In some embodiments the diesel fuel composition further comprises (iii) the reaction product of a carboxylic acid-derived acylating agent and an amine.

These may also be referred to herein in general as acylated nitrogen-containing compounds.

Suitable acylated nitrogen-containing compounds may be made by reacting a carboxylic acid acylating agent with an amine and are known to those skilled in the art. Preferred hydrocarbyl substituted acylating agents are polyisobutenyl succinic anhydrides. These compounds are commonly referred to as “PIBSAs” and are known to the person skilled in the art.

Conventional polyisobutenes and so-called “highly-reactive” polyisobutenes are suitable for use in the invention.

Especially preferred PIBSAs are those having a PIB molecular weight (Mn) of from 300 to 2800, preferably from 450 to 2300, more preferably from 500 to 1300.

In preferred embodiments the reaction product of the carboxylic acid derived acylating agent and an amine includes at least one primary or secondary amine group.

A preferred acylated nitrogen-containing compound for use herein is prepared by reacting a poly(isobutene)-substituted succinic acid-derived acylating agent (e.g., anhydride, acid, ester, etc.) wherein the poly(isobutene) substituent has a number average molecular weight (Mn) of between 170 to 2800 with a mixture of ethylene polyamines having 2 to about 9 amino nitrogen atoms, preferably about 2 to about 8 nitrogen atoms, per ethylene polyamine and about 1 to about 8 ethylene groups. These acylated nitrogen compounds are suitably formed by the reaction of a molar ratio of acylating agent:amino compound of from 10:1 to 1 :10, preferably from 5:1 to 1 :5, more preferably from 2:1 to 1 :2 and most preferably from 2:1 to 1 :1 . In especially preferred embodiments, the acylated nitrogen compounds are formed by the reaction of acylating agent to amino compound in a molar ratio of from 1.8:1 to 1 :1.2, preferably from 1.6:1 to 1 :1.2, more preferably from 1.4:1 to 1 :1.1 and most preferably from 1.2:1 to 1 :1. Acylated amino compounds of this type and their preparation are well known to those skilled in the art and are described in for example EP0565285 and US5925151.

In some preferred embodiments the composition comprises a detergent of the type formed by the reaction of a polyisobutene-substituted succinic acid-derived acylating agent and a polyethylene polyamine. Suitable compounds are, for example, described in W02009/040583.

In some embodiments the diesel fuel composition of the present invention comprises from 1 to 500 ppm, preferably 5 to 250ppm of the additive of the present invention and from 1 to 500 ppm, preferably 5 to 250ppm of an additive which is the reaction product of an acylating agents and an amine (iii).

In some embodiments the diesel fuel composition comprises (iv) the reaction product of a carboxylic acid-derived acylating agent and hydrazine. Suitably the additive comprises the reaction product between a hydrocarbyl-substituted succinic acid or anhydride and hydrazine.

Preferably, the hydrocarbyl group of the hydrocarbyl-substituted succinic acid or anhydride comprises a CS-CSB group, preferably a Cs-Cis group. Alternatively, the hydrocarbyl group may be a polyisobutylene group with a number average molecular weight of between 200 and 2500, preferably between 800 and 1200.

Hydrazine has the formula NH2-NH2 Hydrazine may be hydrated or non-hydrated. Hydrazine monohydrate is preferred.

The reaction between the hydrocarbyl-substituted succinic acid or anhydride and hydrazine produces a variety of products, such as is disclosed in US 2008/0060259.

In some embodiments the diesel fuel composition further comprises (v) a salt formed by the reaction of a carboxylic acid with di-n-butylamine ortri-n-butylamine. Exemplary compounds of this type are described in US 2008/0060608.

Such additives may suitably be the di-n-butylamine or tri-n-butylamine salt of a fatty acid of the formula [R’(COOH)x]y', where each R’ is a independently a hydrocarbon group of between 2 and 45 carbon atoms, and x is an integer between 1 and 4.

In a preferred embodiment, the carboxylic acid comprises tall oil fatty acid (TOFA).

Further preferred features of additives of this type are described in EP1900795.

In some embodiments the diesel fuel composition further comprises (vi) the reaction product of a hydrocarbyl-substituted dicarboxylic acid or anhydride and an amine compound or salt which product comprises at least one amino triazole group.

Further preferred features of additive compounds of this type are as defined in US2009/0282731 .

In some embodiments the diesel fuel composition further comprises (vii) a substituted polyaromatic detergent additive. One preferred compound of this type is the reaction product of an ethoxylated naphthol and paraformaldehyde which is then reacted with a hydrocarbyl substituted acylating agent.

Further preferred features of these detergents are described in EP1884556.

In some embodiments the diesel fuel composition further comprises (viii) a partial ester of a substituted succinic acid.

Preferred compounds of this type are ester compounds which are the reaction product of a hydrocarbyl substituted succinic acid or a hydrocarbyl substituted succinic anhydride. and an alcohol or formula H-(OR) _n -OR ¹ , wherein R is an optionally substituted alkylene group; R ¹ is hydrogen or an optionally substituted hydrocarbyl group, and n is 0 or a positive integer; wherein n is not 0 when R ¹ is hydrogen.

Further preferred features of these detergents are described in the applicant’s copending applications WO2018/178680, WO2018/178678, WO2018/178695 and WO2018/178674.

The additive composition of the sixth aspect of the invention comprises a diluent or carrier. Suitable diluents and carriers will be known to the person skilled in the art. Aromatic diluents are preferred.

The additive composition of the sixth aspect of the invention may include one or more further additives.

In some embodiments additive composition of the sixth aspect comprises a corrosion inhibitor.

In some embodiments additive composition of the sixth aspect comprises a lubricity improver.

In some embodiments additive composition of the sixth aspect comprises an antifoam additive.

In some preferred embodiments the additive composition of the sixth aspect comprises a polymeric additive of formula (I) and a further nitrogen containing detergent additive selected from (i) a quaternary ammonium salt additive; (iii) the reaction product of a carboxylic acid- derived acylating agent and an amine; and mixtures thereof.

In some especially preferred embodiments the first aspect of the present invention relates to a diesel fuel composition comprising an additive of the present invention and a quaternary ammonium salt additive. Preferred quaternary ammonium salt additives are the reaction product of a nitrogen-containing species having at least one tertiary amine group and a quaternising agent wherein the nitrogen containing species is the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group. Preferably the quaternising agent is an ester quaternising agent.

In some especially preferred embodiments the second aspect of the present invention relates to a method of improving the performance of an engine comprising combusting in the engine a diesel fuel composition comprising an additive of the present invention and a quaternary ammonium salt additive. Preferred quaternary ammonium salt additives are the reaction product of a nitrogen-containing species having at least one tertiary amine group and a quaternising agent wherein the nitrogen containing species is the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group. Preferably the quaternising agent is an ester quaternising agent.

In some especially preferred embodiments the third aspect of the present invention relates to the use of the combination of an additive of the present invention and a quaternary ammonium salt additive in a fuel composition to improve the performance of an engine combusting said fuel composition. Preferred quaternary ammonium salt additives are the reaction product of a nitrogen-containing species having at least one tertiary amine group and a quaternising agent wherein the nitrogen containing species is the reaction product of a hydrocarbyl-substituted acylating agent and a compound comprising at least one tertiary amine group and a primary amine, secondary amine or alcohol group. Preferably the quaternising agent is an ester quaternising agent.

In some embodiments the fuel composition is a gasoline composition.

Thus the first aspect of the present invention may relate to a gasoline fuel composition.

By the term “gasoline”, it is meant a liquid fuel for use with spark ignition engines (typically or preferably containing primarily or only C4-C12 hydrocarbons) and satisfying international gasoline specifications, such as ASTM D-439 and EN228. The term includes blends of distillate hydrocarbon fuels with oxygenated components such as alcohols or ethers for example methanol, ethanol, butanol, methyl t-butyl ether (MTBE), ethyl t-butyl ether (ETBE), as well as the distillate fuels themselves. In some embodiments the gasoline fuel composition of the present invention may comprise one or more further gasoline detergents. Additional gasoline detergents may be selected from:

(p) hydrocarbyl - substituted polyoxyalkylene amines or polyetheramines;

(q) acylated nitrogen compounds which are the reaction product of a carboxylic acid-derived acylating agent and an amine;

I hydrocarbyl-substituted amines wherein the hydrocarbyl substituent is substantially aliphatic and contains at least 8 carbon atoms;

(s) Mannich base additives comprising nitrogen-containing condensates of a phenol, aldehyde and primary or secondary amine;

(t) aromatic esters of a polyalkylphenoxyalkanol;

(u) an additional quaternary ammonium salt additive; and

(v) tertiary hydrocarbyl amines having a maximum of 30 carbon atoms.

Suitable hydrocarbyl-substituted polyoxyalkylene amines or polyetheramines (p) are described in US 6217624 and US 4288612. Other suitable polyetheramines are those taught in US 5089029 and US 5112364.

The gasoline composition of the present invention may comprise as an additive acylated nitrogen compounds (q) which are the reaction product of a carboxylic acid-derived acylating agent and an amine. Such compounds are preferably as previously defined herein in relation to component (iii) of the additives which may be added to the diesel fuel compositions of the present invention.

Hydrocarbyl-substituted amines I suitable for use in the gasoline fuel compositions of the present invention are well known to those skilled in the art and are described in a number of patents. Among these are U.S. Pat. Nos. 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,755,433 and 3,822,209. These patents describe suitable hydrocarbyl amines for use in the present invention including their method of preparation.

The Mannich additives (s) comprise nitrogen-containing condensates of a phenol, aldehyde and primary or secondary amine, and are suitably as defined in relation to component (ii) of the additives suitable for use in diesel fuel compositions.

The gasoline compositions of the present invention may further comprise as additives (t) aromatic esters of a polyalkylphenoxyalkanol.

The aromatic ester component which may be employed additive composition is an aromatic ester of a polyalkylphenoxyalkanol and has the following general formula: or a fuel-soluble salt(s) thereof wherein R is hydroxy, nitro or -(CH2)X-NRSRB, wherein Rs and RB are independently hydrogen or lower alkyl having 1 to 6 carbon atoms and x is 0 or 1 ;

Ri is hydrogen, hydroxy, nitro or -NRyRs wherein R? and Rs are independently hydrogen or lower alkyl having 1 to 6 carbon atoms;

R2 and R3 are independently hydrogen or lower alkyl having 1 to 6 carbon atoms; and R4 is a polyalkyl group having an average molecular weight in the range of about 450 to 5,000.

Preferred features of these aromatic ester compounds are as described in WO2011141731 .

The additional quaternary ammonium salt additives (u) are suitably as defined in relation to component (i) of the additives suitable for use in diesel fuel compositions.

Tertiary hydrocarbyl amines (v) suitable for use in the gasoline fuel compositions of the present invention are tertiary amines of the formula R ¹ R ² R ³ N wherein R ¹ , R ² and R ³ are the same or different C1-C20 hydrocarbyl residues and the total number of carbon atoms is no more than 30. Suitable examples are N,N dimethyl n dodecylamine, 3-(N, N-dimethylamino) propanol and N, N-di(2-hydroxyethyl)-oleylamine. Preferred features of these tertiary hydrocarbyl amines are as described in US2014/0123547.

The gasoline composition may further comprise a carrier oil.

The carrier oil may have any suitable molecular weight. A preferred molecular weight is in the range 500 to 5000.

In one embodiment the carrier oil may comprise an oil of lubricating viscosity, including natural or synthetic oils of lubricating viscosity, oil derived from hydrocracking, hydrogenation, hydrofinishing, unrefined, refined and re-refined oils, or mixtures thereof. Natural oils include animal oils, vegetable oils, mineral oils or mixtures thereof. Synthetic oils may include hydrocarbon oils such as those produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes.

In another embodiment the carrier oil may comprise a polyether carrier oil. In a preferred embodiment the polyether carrier oil is a mono end-capped polyalkylene glycol, especially a mono end-capped polypropylene glycol. Carrier oils of this type will be known to the person skilled in the art.

The gasoline fuel compositions of the present invention may contain one or more further additives conventionally added to gasoline, for example other detergents, dispersants, antioxidants, anti-icing agents, metal deactivators, lubricity additives, friction modifiers, dehazers, corrosion inhibitors, dyes, markers, octane improvers, anti-valve-seat recession additives, stabilisers, demulsifiers, antifoams, odour masks, conductivity improvers and combustion improvers.

The second aspect of the present invention relates to a method of improving the performance of an engine.

The third aspect of the present invention relates to the use of an additive in a fuel composition to improve the performance of an engine combusting the fuel composition.

Preferred features of the additives used in the second and third aspects of the present invention are as defined in relation to the first aspect.

References herein to improving performance and/or combating deposits may apply to either the second and/or the third aspect of the present invention.

The second and third aspects of the present invention may improve the performance of a diesel engine and/or a gasoline engine.

Preferably the method and use of the present invention provide an improvement in the performance of a diesel engine. This improvement in performance is suitably selected from one or more of: a reduction in power loss of the engine; a reduction in external diesel injector deposits; a reduction in internal diesel injector deposits; an improvement in fuel economy; a reduction in fuel filter deposits; a reduction in emissions; and an increase in maintenance intervals.

The additives of the present invention may provide a further benefit in addition to those listed above. For example the additive may provide lubricity benefits and/or corrosion inhibition and/or cold flow improvement.

In some embodiments the combination of an additive of the present invention and a further additive may provide synergistic improvement in performance.

For example the use of an additive of the present invention in combination with a cold flow improver may provide an unexpected improvement in detergency and/or cold flow performance compared with the performance of the individual additives used alone.

In some embodiments the use of an additive of the present invention may enable a lower treat rate of cold flow improver to be used.

For example the use of an additive of the present invention in combination with a corrosion inhibitor may provide an unexpected improvement in detergency and/or corrosion inhibition compared with the performance of the individual additives used alone.

In some embodiments the use of an additive of the present invention may enable a lower treat rate of corrosion inhibitor to be used.

For example the use of an additive of the present invention in combination with a lubricity improver may provide an unexpected improvement in detergency and/or lubricity compared with the performance of the individual additives used alone.

In some embodiments the use of an additive of the present invention may enable a lower treat rate of lubricity improver to be used.

For example the use of an additive of the present invention in combination with an antifoam additive may provide an unexpected improvement in antifoam performance compared with the performance of the individual additives used alone. In some embodiments the use of an additive of the present invention may enable a lower treat rate of antifoam additive to be used.

In some embodiments the additive of the present invention may provide an “antifoam boost performance”. By this we mean that addition of the additive of the present invention to a composition comprising an antifoam additive increases the antifoam performance.

In some preferred embodiments the diesel fuel composition of the present invention comprises one or more further detergents. Nitrogen-containing detergents are preferred.

The one or more further detergents may provide a synergistic benefit such that an improved performance is observed when using the combination of an additive of the present invention and a nitrogen-containing detergent compared to the use of an equivalent amount of either additive alone.

The use of a combination of an additive of the present invention and a nitrogen-containing detergent may also combat deposits and improve performance in a traditional diesel engine.

In some embodiments the combination of an additive of the present invention and a nitrogencontaining detergent may provide an improvement in antifoam performance (an antifoam boost).

In some embodiments the combination of an additive of the present invention and a nitrogencontaining detergent may provide an improvement in lubricity.

In some embodiments the combination of an additive of the present invention and a nitrogencontaining detergent may provide an improvement in corrosion inhibition.

This improvement in performance of the second and third aspects of the present invention is preferably achieved by combatting deposits in the engine.

The additives used in the present invention have been found to be particularly effective in modern diesel engines having a high pressure fuel system. Some features of engines of this type have been previously described herein.

Suitably the present invention combats deposits and/or improves performance of a diesel engine having a high pressure fuel system. Suitably the diesel engine has a pressure in excess of 1350 bar (1 .35 x 10 ⁸ Pa). It may have a pressure of up to 2000 bar (2 x 10 ⁸ Pa) or more.

Two non-limiting examples of such high pressure fuel systems are: the common rail injection system, in which the fuel is compressed utilizing a high-pressure pump that supplies it to the fuel injection valves through a common rail; and the unit injection system which integrates the high-pressure pump and fuel injection valve in one assembly, achieving the highest possible injection pressures exceeding 2000 bar (2 x 10 ⁸ Pa). In both systems, in pressurising the fuel, the fuel gets hot, often to temperatures around 100°C, or above.

In common rail systems, the fuel is stored at high pressure in the central accumulator rail or separate accumulators prior to being delivered to the injectors. Often, some of the heated fuel is returned to the low pressure side of the fuel system or returned to the fuel tank. In unit injection systems the fuel is compressed within the injector in order to generate the high injection pressures. This in turn increases the temperature of the fuel.

In both systems, fuel is present in the injector body prior to injection where it is heated further due to heat from the combustion chamber. The temperature of the fuel at the tip of the injector can be as high as 250 - 350 °C.

Thus the fuel is stressed at pressures from 1350 bar (1 .35 x 10 ⁸ Pa) to over 2000 bar (2 x 10 ⁸ Pa) and temperatures from around 100°C to 350°C prior to injection, sometimes being recirculated back within the fuel system thus increasing the time for which the fuel experiences these conditions.

A common problem with diesel engines is fouling of the injector, particularly the injector body, and the injector nozzle. Fouling may also occur in the fuel filter. Injector nozzle fouling occurs when the nozzle becomes blocked with deposits from the diesel fuel. Fouling of fuel filters may be related to the recirculation of fuel back to the fuel tank. Deposits increase with degradation of the fuel. Deposits may take the form of carbonaceous coke-like residues, lacquers or sticky or gum-like residues. Diesel fuels become more and more unstable the more they are heated, particularly if heated under pressure. Thus diesel engines having high pressure fuel systems may cause increased fuel degradation. In recent years the need to reduce emissions has led to the continual redesign of injection systems to help meet lower targets. This has led to increasingly complex injectors and lower tolerance to deposits.

The problem of injector fouling may occur when using any type of diesel fuels. However, some fuels may be particularly prone to cause fouling or fouling may occur more quickly when these fuels are used. For example, fuels containing biodiesel and those containing metallic species may lead to increased deposits.

When injectors become blocked or partially blocked, the delivery of fuel is less efficient and there is poor mixing of the fuel with the air. Over time this leads to a loss in power of the engine, increased exhaust emissions and poor fuel economy.

Deposits are known to occur in the spray channels of the injector, leading to reduced flow and power loss. As the size of the injector nozzle hole is reduced, the relative impact of deposit build up becomes more significant. Deposits are also known to occur at the injector tip. Here, they affect the fuel spray pattern and cause less effective combustion and associated higher emissions and increased fuel consumption.

In addition to these “external” injector deposits in the nozzle hole and at the injector tip which lead to reduced flow and power loss, deposits may occur within the injector body causing further problems. These deposits may be referred to as internal diesel injector deposits (or IDIDs). IDIDs occur inside the injector on the critical moving parts. They can hinder the movement of these parts affecting the timing and quantity of fuel injection. Since modern diesel engines operate under very precise conditions these deposits can have a significant impact on performance.

IDIDs cause a number of problems, including power loss and reduced fuel economy due to less than optimal fuel metering and combustion. Initially the user may experience cold start problems and/or rough engine running. These deposits can lead to more serious injector sticking. This occurs when the deposits stop parts of the injector from moving and thus the injector stops working. When several or all of the injectors stick the engine may fail completely.

The CEC have recently introduced an Internal Diesel Injector Deposit Test, CEC F-110-16, to discriminate between fuels that differ in their ability to produce IDIDs in direct injection common rail diesel engines.

As mentioned above, the problem of injector fouling may be more likely to occur when using fuel compositions comprising metal species. Various metal species may be present in fuel compositions. This may be due to contamination of the fuel during manufacture, storage, transport or use or due to contamination of fuel additives. Metal species may also be added to fuels deliberately. For example, transition metals are sometimes added as fuel borne catalysts, for example to improve the performance of diesel particulate filters. Problems of injector sticking may occur when metal or ammonium species, particularly sodium species, react with carboxylic acid species in the fuel.

Sodium contamination of diesel fuel and the resultant formation of carboxylate salts is believed to be a major cause of injector sticking.

In some embodiments the diesel fuel compositions used in the present invention comprise sodium and/or calcium. Suitably they comprise sodium. The sodium and/or calcium is typically present in a total amount of from 0.01 to 50 ppm, preferably from 0.05 to 5 ppm preferably 0.1 to 2 ppm such as 0.1 to 1 ppm.

Other metal-containing species may also be present as a contaminant, for example through the corrosion of metal and metal oxide surfaces by acidic species present in the fuel or from lubricating oil. In use, fuels such as diesel fuels routinely come into contact with metal surfaces for example, in vehicle fuelling systems, fuel tanks, fuel transportation means etc. Typically, metal-containing contamination may comprise transition metals such as zinc, iron and copper; Group I or Group II metals and other metals such as lead.

The presence of metal containing species may give rise to fuel filter deposits and/or external injector deposits including injector tip deposits and/or nozzle deposits.

In addition to metal-containing contamination which may be present in diesel fuels there are circumstances where metal-containing species may deliberately be added to the fuel. For example, as is known in the art, metal-containing fuel-borne catalyst species may be added to aid with the regeneration of particulate traps. The presence of such catalysts may also give rise to injector deposits when the fuels are used in diesel engines having high pressure fuel systems.

Metal-containing contamination, depending on its source, may be in the form of insoluble particulates or soluble compounds or complexes. Metal-containing fuel-borne catalysts are often soluble compounds or complexes or colloidal species.

In some embodiments, the diesel fuel may comprise metal-containing species comprising a fuel-borne catalyst. Preferably, the fuel borne catalyst comprises one or more metals selected from iron, cerium, platinum, manganese, Group I and Group II metals e.g., calcium and strontium. Most preferably the fuel borne catalyst comprises a metal selected from iron and cerium. In some embodiments, the diesel fuel may comprise metal-containing species comprising zinc. Zinc may be present in an amount of from 0.01 to 50 ppm, preferably from 0.05 to 5 ppm, more preferably 0.1 to 1 .5 ppm.

Typically, the total amount of all metal-containing species in the diesel fuel, expressed in terms of the total weight of metal in the species, is between 0.1 and 50 ppm by weight, for example between 0.1 and 20 ppm, preferably between 0.1 and 10 ppm by weight, based on the weight of the diesel fuel.

It is advantageous to provide a diesel fuel composition which prevents or reduces the occurrence of deposits in a diesel engine. In some embodiments such deposits may include “external” injector deposits such as deposits in and around the nozzle hole and at the injector tip. In some preferred embodiments the deposits include “internal” injector deposits or IDIDs. Such fuel compositions may be considered to perform a “keep clean” function i.e. they prevent or inhibit fouling. It is also be desirable to provide a diesel fuel composition which would help clean up deposits of these types. Such a fuel composition which when combusted in a diesel engine removes deposits therefrom thus effecting the “clean up” of an already fouled engine.

As with “keep clean” properties, “clean up” of a fouled engine may provide significant advantages. For example, superior clean up may lead to an increase in power and/or an increase in fuel economy. In addition removal of deposits from an engine, in particular from injectors may lead to an increase in interval time before injector maintenance or replacement is necessary thus reducing maintenance costs.

Although for the reasons mentioned above deposits in injectors is a particular problem found in modern diesel engines with high pressure fuels systems, it is desirable to provide a diesel fuel composition which also provides effective detergency in older traditional diesel engines such that a single fuel supplied at the pumps can be used in engines of all types.

It is also desirable that fuel compositions reduce the fouling of vehicle fuel filters. It is useful to provide compositions that prevent or inhibit the occurrence of fuel filter deposits i.e. provide a “keep clean” function. It is useful to provide compositions that remove existing deposits from fuel filter deposits i.e. provide a “clean up” function. Compositions able to provide both of these functions are especially useful.

The method of the present invention is particularly effective at combatting deposits in a modern diesel engine having a high pressure fuel system. Such diesel engines may be characterised in a number of ways.

Such engines are typically equipped with fuel injection equipment meeting or exceeding “Euro 5” emissions legislation or equivalent legislation in the US or other countries.

Such engines are typically equipped with fuel injectors having a plurality of apertures, each aperture having an inlet and an outlet.

Such engines may be characterised by apertures which are tapered such that the inlet diameter of the spray-holes is greater than the outlet diameter.

Such modern engines may be characterised by apertures having an outlet diameter of less than 500pm, preferably less than 200pm, more preferably less than 150pm, preferably less than 100pm, most preferably less than 80pm or less.

Such modern diesel engines may be characterised by apertures where an inner edge of the inlet is rounded.

Such modern diesel engines may be characterised by the injector having more than one aperture, suitably more than 2 apertures, preferably more than 4 apertures, for example 6 or more apertures.

Such modern diesel engines may be characterised by an operating tip temperature in excess of 250°C.

Such modern diesel engines may be characterised by a fuel injection system which provides a fuel pressure of more than 1350 bar, preferably more than 1500 bar, more preferably more than 2000 bar. Preferably, the diesel engine has fuel injection system which comprises a common rail injection system.

The method of the present invention preferably combats deposits in an engine having one or more of the above-described characteristics.

The use of the present invention preferably improves the performance of an engine by reducing deposits in the engine.

The second aspect of the present invention preferably relates to a method of improving the performance of an engine by combating deposits in the engine. Combating deposits may involve reducing or the preventing of the formation of deposits in an engine compared to when running the engine using unadditised fuel. Such a method may be regarded as achieving “keep clean” performance.

Combating deposits may involve the removal of existing deposits in an engine. This may be regarded as achieving “clean up” performance.

In especially preferred embodiments the method of the second aspect and the use of the third aspect of the present invention may be used to provide “keep clean” and “clean up” performance.

As explained above deposits may occur at different places within a diesel engine, for example a modern diesel engine.

The present invention is particularly useful in the prevention or reduction or removal of internal deposits in injectors of engines operating at high pressures and temperatures in which fuel may be recirculated and which comprise a plurality of fine apertures through which the fuel is delivered to the engine. The present invention finds utility in engines for heavy duty vehicles and passenger vehicles. Passenger vehicles incorporating a high speed direct injection (or HSDI) engine may for example benefit from the present invention.

The present invention may also provide improved performance in modern diesel engines having a high pressure fuel system by controlling external injector deposits, for example those occurring in the injector nozzle and/or at the injector tip. The ability to provide control of internal injector deposits and external injector deposits is a useful advantage of the present invention.

Suitably the present invention may reduce or prevent the formation of external injector deposits. It may therefore provide “keep clean” performance in relation to external injector deposits.

Suitably the present invention may reduce or remove existing external injector deposits. It may therefore provide “clean up” performance in relation to external injector deposits.

Suitably the present invention may reduce or prevent the formation of internal diesel injector deposits. It may therefore provide “keep clean” performance in relation to internal diesel injector deposits. Suitably the present invention may reduce or remove existing internal diesel injector deposits. It may therefore provide “clean up” performance in relation to internal diesel injector deposits.

The present invention may also combat deposits on vehicle fuel filters. This may include reducing or preventing the formation of deposits (“keep clean” performance) or the reduction or removal of existing deposits (“clean up” performance).

One way in which the control of fuel filter deposits can be assessed is described in example 12.

The removal or reduction of IDIDs according to the present invention will lead to an improvement in performance of the engine.

The improvement in performance of the diesel engine system may be measured by a number of ways. Suitable methods will depend on the type of engine and whether “keep clean” and/or “clean up” performance is measured.

An improvement in “keep clean” performance may be measured by comparison with a base fuel. “Clean up” performance can be observed by an improvement in performance of an already fouled engine.

The effectiveness of fuel additives is often assessed using a controlled engine test.

In Europe the Co-ordinating European Council for the development of performance tests for transportation fuels, lubricants and other fluids (the industry body known as CEC), has developed a test for additives for modern diesel engines such as HSDI engines. The CEC F- 98-08 test is used to assess whether diesel fuel is suitable for use in engines meeting new European Union emissions regulations known as the “Euro 5” regulations. The test is based on a Peugeot DW10 engine using Euro 5 injectors, and is commonly referred to as the DW10B test. This test measures power loss in the engine due to deposits on the injectors, and is further described in example 4. Any reference to the DW10B test herein, unless otherwise stated, refers to the method described in example 4.

Preferably the use of the fuel composition of the present invention leads to reduced deposits in the DW10B test. For “keep clean” performance a reduction in the occurrence of deposits is preferably observed. For “clean up” performance removal of deposits is preferably observed. The DW10B test is used to measure the power loss in modern diesel engines having a high pressure fuel system.

Suitably the use of a fuel composition of the present invention may provide a “keep clean” performance in modern diesel engines, that is the formation of deposits in the injectors of these engines may be inhibited or prevented. Preferably this performance is such that a power loss of less than 5%, preferably less than 2% is observed after 32 hours as measured by the DWWB test.

Suitably the use of a fuel composition of the present invention may provide a “clean up” performance in modern diesel engines that is, deposits on the injectors of an already fouled engine may be removed. Preferably this performance is such that the power of a fouled engine may be returned to within 1 % of the level achieved when using clean injectors within 16 hours, preferably 12 hours, more preferably 8 hours as measured in the DW10B test.

In some preferred embodiments, clean up may also provide a power increase. Thus a fouled engine may be treated to remove the existing deposits and provide an additional power gain.

Clean injectors can include new injectors or injectors which have been removed and physically cleaned, for example in an ultrasound bath.

The combination of an additive of the present invention and a quaternary ammonium salt additive can be particularly effective for improving the performance of a modern diesel engine having a high pressure fuel system.

The CEC have also developed a new test, commonly known as the DW10C which assesses the ability of a fuel composition to prevent the formation of IDIDs that lead to injector sticking. This test is described in example 5. A modified version of this test adapted to measure clean up, is described in example 7. Any reference to the DW10C test herein, unless otherwise stated, refers to the method described in example 5.

The DW10C test procedure was developed by CEC as a “keep clean” procedure test and thus may be used to measure the “keep clean” performance of an engine. However it is often modified and used as a clean up procedure and thus can also be used to measure the “clean up” performance of an engine. In some embodiments the present invention provides a “keep clean” performance in relation to the formation of IDIDs. Such performance may be illustrated by achieving a merit score of at least 7 as measured by the DW10C test, preferably at least 8, more preferably at least 9.

In some embodiments a merit score of at least 9.3 may be achieved, for example at least 9.4, at least 9.5, at least 9.6 or at least 9.7.

Very surprisingly additives of the present invention have been found to perform exceptionally well in the DW10C test. In some instances a score in excess of 9.8 has been achieved for example in excess of 9.9. As is described in example 6, some additives of the present invention may achieve a score of 10 in the DW10C test.

In some embodiments the present invention provides a “clean up” performance in relation to IDIDs, whereby existing IDIDs may be removed. Such a performance is illustrated in the examples.

One of the parameters measured in the DW10C test is the temperature at the exhaust of each cylinder in the engine. Deviation of the exhaust temperature for a single cylinder, from its normal steady state temperature range when functioning correctly, is an indication of the formation of internal deposits in the corresponding fuel injector. Typically, the exhaust temperatures for the multiple cylinders of an engine will deviate from each other when IDIDs form, dependent on the relative position of each injector (that is to say, whether it is more open or closed) when injector sticking starts to occur. In the DW10C test, the exhaust temperature deviation may be defined as the temperature difference between the hottest and coldest cylinder exhaust as measured at any single time point during the 5 minute idle period following each cold start. The maximum exhaust temperature deviation may be defined as the largest value of exhaust temperature deviation that occurred during that same 5 minute idle period.

Preferably the method and use of the present invention lead to a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C. In some cases a maximum exhaust temperature deviation of less than 10°C may be achieved.

The additives of the present invention have been shown to be especially effective at combatting internal diesel injector deposits, even at low treat rates. Thus the invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive of the present invention (especially the reaction product of itaconic acid or an anhydride thereof and an alkyl or alkenyl alcohol having 4 to 24 carbon atoms) to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid or an anhydride thereof and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl or alkenyl group having 4 to 24 carbon atoms to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl or alkenyl group having 4 to 24 carbon atoms to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic anhydride and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl or alkenyl group having 4 to 24 carbon atoms to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid or an anhydride thereof and an alcohol selected from 2-ethyl hexanol, citronellol and oleyl alcohol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid and an alcohol selected from 2-ethyl hexanol, citronellol and oleyl alcohol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic anhydride and an alcohol selected from 2-ethyl hexanol, citronellol and oleyl alcohol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid or an anhydride thereof and an alcohol selected from 2-ethyl-1 -butanol, 2-ethyl-1 -hexanol, 2-ethyl-1 -heptanol, 2-ethyl-1 -decanol, 2-hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl-1 -dodecanol, 2-octyl-1- dodecanol and 2-decyl-1 -tetradecanol and isotridecanol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid and an alcohol selected from 2-ethyl-1 -butanol, 2-ethyl-1 -hexanol, 2-ethyl-1 -heptanol, 2-ethyl-1 -decanol, 2- hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl-1 -dodecanol, 2-octyl-1 -dodecanol and 2-decyl-1- tetradecanol and isotridecanol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic anhydride and an alcohol selected from 2-ethyl-1 -butanol, 2-ethyl-1 -hexanol, 2-ethyl-1 -heptanol, 2-ethyl-1- decanol, 2-hexyl-1 -decanol, 2-octyl-1 -decanol, 2-hexyl-1 -dodecanol, 2-octyl-1 -dodecanol and 2-decyl-1 -tetradecanol and isotridecanol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid or an anhydride thereof and an alcohol of formula H-(OR ² ) _m -OR ¹ wherein R ² is an optionally substituted alkylene group, R ¹ is a C4 to C30 alkyl or alkenyl group, m is not 0 and the additive of the present invention is prepared from an alkyl or alkenyl ether of a polyhydric alcohol, for example an ether of a polyethylene glycol, a polypropylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol or tripropylene glycol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C. The invention may further provide the use of less than 150 ppm, for example from 10 to 120 ppm, of an additive that is the polymerised reaction product of itaconic acid or an anhydride thereof and an alcohol selected from methanol, ethanol, propanol, isopropanol, ethylene glycol, propylene glycol and glycerol to combat IDIDs, as illustrated for example by a maximum exhaust temperature deviation of less than 30°C in the DW10C test, preferably less than 20°C, suitably less than 15°C.

The diesel fuel compositions of the present invention may also provide improved performance when used with traditional diesel engines. Preferably the improved performance is achieved when using the diesel fuel compositions in modern diesel engines having high pressure fuel systems and when using the compositions in traditional diesel engines. This is important because it allows a single fuel to be provided that can be used in new engines and older vehicles.

For older engines an improvement in performance may be measured using the XUD9 test. This test is described in relation to example 8.

Suitably the use of a fuel composition of the present invention may provide a “keep clean” performance in traditional diesel engines, that is the formation of deposits on the injectors of these engines may be inhibited or prevented. Preferably this performance is such that a flow loss of less than 50%, preferably less than 30% is observed after 10 hours as measured by the XUD-9 test.

Suitably the use of a fuel composition of the present invention may provide a “clean up” performance in traditional diesel engines, that is deposits on the injectors of an already fouled engine may be removed. Preferably this performance is such that the flow loss of a fouled engine may be reduced by 10% or more within 10 hours as measured in the XUD-9 test.

The benefits provided by the present invention mean that engines need to be serviced less frequently, leading to cost savings and an increase in maintenance intervals.

In a preferred embodiment the present invention provides the use of a combination of a polymeric additive of formula (I) and a quaternary ammonium salt additive to improve the performance of traditional diesel engines, suitably as measured in the XUD-9 test.

Preferably the invention provides the use of a combination of the polymerised reaction product of itaconic anhydride and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl or alkenyl group having 4 to 24 carbon atoms and a quaternary ammonium salt additive (ia) to improve the performance of traditional diesel engines, suitably as measured in the XUD-9 test, wherein the quaternary ammonium salt additive (ia) is the quaternised reaction product of a hydrocarbyl substituted succinic acid derived acylating agent and a compound able to react with said acylating agent and which includes a tertiary amine group.

In preferred embodiments the present invention may involve the combination of the polymerised reaction product of itaconic anhydride and an alcohol of formula R ¹ OH wherein R ¹ is an alkyl or alkenyl group having 4 to 24 carbon atoms, preferably wherein the polymer comprises from 6 to 150, preferably 8 to 120 monomer units and a quaternary ammonium salt additive (ia) which is formed by reacting methyl salicylate or dimethyl oxalate with the reaction product of a polyisobutylene-substituted succinic anhydride having a PIB molecular weight of 700 to 1300 and dimethylaminopropylamine.

The present invention may improve the performance of gasoline engines.

Gasoline compositions of the present invention suitably achieve good control of deposits in spark ignition gasoline engines. They may provide deposit control in port fuel injection (PFI) gasoline engines.

Good control of deposits may even be achieved in the demanding context of the direct injection spark ignition gasoline engine.

This control of deposits may lead to a significant reduction in maintenance costs and/or an increase in power and/or an improvement in fuel economy.

The second aspect of the present invention may provide a method of improving performance by controlling deposits in spark ignition engine. Preferably the engine is a direct injection spark ignition gasoline engine.

The improvement in performance of the second and third aspects of the present invention may involve improving the efficiency of a direct injection spark ignition gasoline engine.

The improvement in performance of the second and third aspects of the present invention in a direct injection spark ignition gasoline engine may provide one or more of:- improved fuel economy reduced maintenance less frequent overhaul or replacement of injectors improved driveability improved power improved acceleration

Any feature of the invention may be combined with any other feature as appropriate.

The invention will now be further described with reference to the following non-limiting examples. In the examples which follow the values given in parts per million (ppm) for treat rates denote active agent amount, not the amount of a formulation as added, and containing an active agent. All parts per million are by weight.

General Procedures

Acid values were determined by non-aqueous titration using lithium methoxide (LiOMe).

Example 1

To a 1 L reactor charged with 2-ethylhexanol (250g, 1.918 moles) was added toluene (215.7g) and heated to 90°C. To the stirred liquid was added itaconic acid (250g, 1.921 moles) and p- toluenesulfonic acid (3.31g). The reaction was heated towards 120°C, whilst removing water by distillation over 7 hours. The products where cooled to room temperature and unreacted itaconic and p-toluenesulfonic acid removed by filtration and washing with water. The toluene was removed on a rotary evaporator to leave a yellow/orange liquid (2-ethylhexyl itaconate, 412.9g)

Example 2

Additive A, a polymeric additive of the invention was prepared as follows:

To a 250ml reactor was charged 2-ethylhexyl itaconate (120g) was added cyclohexane (51 ,43g) and the reactor contents sparged with Nitrogen for 1 hour whilst heating to 80°C. Trigonox 25-C75 (0.685g, 0.5wt, %, tert-Butyl peroxypivalate) was added and the reaction was mixed at 80°C for 1 hour before adding further Trigonox 25-C75 (0.685g) and heating for a further 3 hours at 80°C. The cyclohexane was removed on a rotary evaporator and Aromatic 150 (69.7g) added to leave a clear amber viscous liquid (184.4g, Mw 10932, acid value of 2.4 mmolH+/g).

Example 3 Additive B, a quaternary ammonium salt additive was prepared as follows:

700 g (0.7 mol) of polyisobutylene (M _n 1000) was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer. The starting material was heated to 120 °C with stirring and nitrogen inerting was repeated. The reaction temperature was increased to 190 °C and maleic anhydride (82.4g, 0.84 mol, 1.2 eq) was charged over 1 hour. After maintaining a temperature of 190 °C for a further 1 hour, the temperature was increased to 200 - 208 °C and held in this range for 8 hours. Vacuum (< 30 mbar) was then applied for 2.5 hrs, whilst maintaining the reaction temperature, which reduced the level of residual maleic anhydride to < 0.05 wt%. The reaction mass was cooled to < 80°C then discharged from the reactor.

The resulting PIBSA was charged to a nitrogen flushed, jacketed reactor fitted with an overhead stirrer and heated to 120 °C. 3-(dimethylamino)propylamine (DMAPA) (1eq relative to anhydride groups) was charged slowly, maintaining the reaction temperature between 120 - 130 °C. After stirring at 120 °C for a further 1 hr, the reaction temperature was increased to 140 °C and held for 3 hrs with concurrent distillation of water. Methyl salicylate (2.1 eq relative to anhydride groups) was added in a single portion and heating was continued at 140 °C for 10 hours. The reaction mass was diluted with Aromatic 150 prior to discharging from the reactor.

Example 4

Diesel fuel compositions were prepared by dosing additives to aliquots all drawn from a common batch of RF06 base fuel, and containing 1 ppm zinc (as zinc neodecanoate).

Table 1 below shows the specification for RF06 base fuel.

Table 1

Property Units Limits Method

Min Max

Cetane Number 52.0 54.0 EN ISO 5165

Density at 15°C kg/m ³ 833 837 EN ISO 3675

Distillation

50% v/v Point 245

95% v/v Point 345 350

FBP 370

Flash Point C 55 EN 22719

Cold Filter Plugging C -5 EN 116

Point Viscosity at 40°C mm ² /sec 2.3 3.3 EN ISO 3104

Polycyclic Aromatic % m/m 3.0 6.0 IP 391

Hydrocarbons

Sulphur Content mg/kg 10 ASTM D 5453

Copper Corrosion 1 EN ISO 2160

Conradson Carbon Residue on % m/m 0.2 EN ISO 10370 10% Dist. Residue

Ash Content % m/m 0.01 EN ISO 6245

Water Content % m/m 0.02 EN ISO 12937

Neutralisation (Strong Acid) mg KOH/g 0.02 ASTM D 974

Number

Oxidation Stability mg/mL 0.025 EN ISO 12205

HFRR (WSD1.4) pm 400 CEC F-06-A-96

Fatty Acid Methyl Ester prohibited

Compositions were prepared as detailed in table 2:

Table 2

Example 5

The performance of fuel compositions of the present invention in modern diesel engines having a high pressure fuel system was tested according to the CEC F-98-08 DW 10 method. This is referred to herein as the DW10B test.

The engine of the injector fouling test is the PSA DW10BTED4. In summary, the engine characteristics are: Design: Four cylinders in line, overhead camshaft, turbocharged with EGR

Capacity: 1998 cm ³ Combustion chamber: Four valves, bowl in piston, wall guided direct injection

Power: 100 kW at 4000 rpm

Torque: 320 Nm at 2000 rpm

Injection system: Common rail with piezo electronically controlled 6-hole injectors.

Max. pressure: 1600 bar (1 .6 x 10 ⁸ Pa). Proprietary design by SIEMENS VDO

Emissions control: Conforms with Euro IV limit values when combined with exhaust gas posttreatment system (DPF)

This engine was chosen as a design representative of the modern European high-speed direct injection diesel engine capable of conforming to present and future European emissions requirements. The common rail injection system uses a highly efficient nozzle design with rounded inlet edges and conical spray holes for optimal hydraulic flow. This type of nozzle, when combined with high fuel pressure has allowed advances to be achieved in combustion efficiency, reduced noise and reduced fuel consumption, but are sensitive to influences that can disturb the fuel flow, such as deposit formation in the spray holes. The presence of these deposits causes a significant loss of engine power and increased raw emissions.

The test is run with a future injector design representative of anticipated Euro V injector technology.

It is considered necessary to establish a reliable baseline of injector condition before beginning fouling tests, so a sixteen hour running-in schedule for the test injectors is specified, using non-fouling reference fuel.

Full details of the CEC F-98-08 test method can be obtained from the CEC. The coking cycle is summarised below.

7. A warm up cycle (12 minutes) according to the following regime:

2. 8 hrs of engine operation consisting of 8 repeats of the following cycle for expected range see CEC method CEC-F-98-08

3. Cool down to idle in 60 seconds and idle for 10 seconds 4. 4 hrs soak period

The standard CEC F-98-08 test method consists of 32 hours engine operation corresponding to 4 repeats of steps 1-3 above, and 3 repeats of step 4. le 56 hours total test time excluding warm ups and cool downs.

Table 3 shows the results when compositions 1 and 2 were tested according to the method above:

Table 3

Example 6 Diesel fuel composition 3 was tested according to the CEC F-98-08 DW10B test method described in example 5, modified to measure clean up performance as outlined below.

A first 32 hour cycle was run using new injectors and RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate). This resulted in a level of power loss of 5.1 % due to fouling of the injectors.

A second 32 hour cycle was then run as a ‘clean up’ phase. The dirty injectors from the first phase were kept in the engine and the fuel changed to RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate) and the test additive. This restored the power to a loss of 1.5% compared to the power obtained when using clean injectors.

Example 7

Diesel fuel composition 7 was tested according to the CEC F-98-08 DW10B test method described in example 5, modified to measure clean up performance as outlined below.

A first 32 hour cycle was run using new injectors and RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate). This resulted in a level of power loss of 5.8% due to fouling of the injectors.

A second 32 hour cycle was then run as a ‘clean up’ phase. The dirty injectors from the first phase were kept in the engine and the fuel changed to RF-06 base fuel having added thereto 1 ppm Zn (as neodecanoate) and the test additive. This restored the power to an increase of 0.3% compared to the power obtained when using clean injectors.

Example 8

The ability of additives of the invention to remove ‘Internal Diesel Injector Deposits’ (IDIDs) was measured according to the test method CEC F-110-16, available from the Co-ordinating European Council. The test uses the PSA DW10C engine.

The engine characteristics as follows:

The test fuel (RF06) is dosed with 0.5mg/kg Na in the form of Sodium Naphthenate + 10mg/kg Dodecyl Succinic Acid (DDSA).

The test procedure consists of main run cycles followed by soak periods, before cold starts are carried out.

The main running cycle consist of two speed and load set points, repeated for 6hrs, as seen below.

■ he ramp times of 30 seconds are indiide in die duration of each step.

During the main run, parameters including, Throttle pedal position, ECU fault codes, Injector balance coefficient and Engine stalls are observed and recorded.

The engine is then left to soak at ambient temperature for 8hrs.

After the soak period the engine is re-started. The starter is operated for 5 seconds; if the engine fails to start the engine is left for 60 seconds before a further attempt. A maximum of 5 attempts are allowed.

If the engine starts the engine is allowed to idle for 5 minutes. Individual exhaust temperatures are monitored and the maximum Temperature Delta is recorded. An increased variation in Cylinder-to-Cylinder exhaust temperatures is a good indication that injectors are suffering from I DID. Causing them to either open slowly or stay open to long.

An example below of all exhaust temperatures with <30°C deviation, indicating no sticking caused by IDID.

The complete test comprises of 6x Cold Starts, although the Zero hour Cold Start does not form part of the Merit Rating and 5x 6hr Main run cycles, giving a total of 30hrs engine running time.

The recorded data is inputted into the Merit Rating Chart. This allows a Rating to be produced for the test. Maximum rating of 10 shows no issues with the running or operability of the engine for the duration of the test.

An example below:

Compositions 1 and 2 were tested according to this method and the results are shown in table 4:

Table 4

Example 9

The ability of additives of the present invention to clean up IDIDs may be assessed according to a modification of the DW10C test described in example 7.

The In-House Clean Up Method developed starts by running the engine using reference diesel (RF06) dosed with 0.5mg/kg Na + 10mg/Kg DDSA until an exhaust temperature Delta of >50°C is observed on the Cold Start. This has repeatedly been seen on the 3 ^rd Cold Start which follows the second main run, 12hrs total engine run time.

Once the increased Exhaust temperature Delta is observed, the engine fuel supply is swapped to reference diesel, dosed with 0.5mg/kg Na (as sodium naphthenate) + 10mg/kg DDSA + the Candidate sample. The fuel is flushed through to the engine and allowed to commence with the next Main run.

The ability of the Candidate additive to prevent any further increase in deposits or to remove the deposits can then be determined as the test continues.

Composition 4 was tested according to this method. After the dirty up phase a merit rating of 8.4 was obtained. This was increased to 10 when using composition 4.

Example 10

The effectiveness of the additives of the present invention in older traditional diesel engine types maybe assessed using a standard industry test - CEC test method No. CEC F-23-A-01 .

This test measures injector nozzle coking using a Peugeot XUD9 A/L Engine and provides a means of discriminating between fuels of different injector nozzle coking propensity. Nozzle coking is the result of carbon deposits forming between the injector needle and the needle seat. Deposition of the carbon deposit is due to exposure of the injector needle and seat to combustion gases, potentially causing undesirable variations in engine performance.

The Peugeot XUD9 A/L engine is a 4 cylinder indirect injection Diesel engine of 1 .9 litre swept volume, obtained from Peugeot Citroen Motors specifically for the CEC PF023 method.

The test engine is fitted with cleaned injectors utilising unflatted injector needles. The airflow at various needle lift positions have been measured on a flow rig prior to test. The engine is operated for a period of 10 hours under cyclic conditions.

The propensity of the fuel to promote deposit formation on the fuel injectors is determined by measuring the injector nozzle airflow again at the end of test, and comparing these values to those before test. The results are expressed in terms of percentage airflow reduction at various needle lift positions for all nozzles. The average value of the airflow reduction at 0.1 mm needle lift of all four nozzles is deemed the level of injector coking for a given fuel.

Compositions 5 and 6 were tested and the results are shown in table 5:

Table 5

For composition 5 an apparent increase in flow of 0.1% was observed.

Example 11

The ability of composition 7 to remove deposits in an XUD-9 engine was measured by first running the test described in example 9 using base fuel and then adding composition 3 to the dirty engine and repeating the test. The flow loss was reduced from 72% following the dirty up phase to 35.5% following the additive of composition 7.

Example 12

The ability of the additives of the invention to reduce fuel filter deposits was assessed according to the following procedure:

Sodium dodecenylsuccinate was generated by heating a 2.5 wt% solution of sodium 2- ethylhexanoate and dodecenylsuccinic acid in RF06 fuel for 3 hours at 150°C. This was added to 650g of an RF06 reference fuel in an amount to provide the required concentration of sodium dodecenylsuccinate.

The inventive additive was dosed into the fuel sample at the desired treat rate. The sample was then heated at 50°C over night (~16 hours).

The fuel was filtered through a 10 micron fuel filter having a diameter of 25mm using 600 mbar vacuum to pull the fuel through the filter.

The flow rate through the filter was determined by measuring the mass of fuel remaining in the original sample vessel overtime.

Example 13

The flow rate through a 10 micron fuel filter was measured for the compositions of table 6 using the method described in example 12.

Table 6

The results are shown in table 7:

Table 7

Example 14

Additive C, a further additive of the invention was prepared as follows:

Step 1 - Esterification to 2-ethylhexyl Itaconate

A clean 1 L oil jacketed reactor with overhead stirrer, was purged with nitrogen and charged with 2-ethylhexanol (300.91g, 2.31 moles), aromatic 150 (236.32g) and stirred. Itaconic acid (250.51g, 1.925moles) and para-toluene sulphonic acid (1.54g, 0.2 wt.%) were added and the reaction heated to 120°C. Water was distilled from the reaction as an azeotrope with A150 for 4 hours.

The reaction mixture was heated to 80°C and washed with water (2 x 150ml) by stirring for 10 minutes and allowing to separate for 1 hour and draining the lower aqueous. The residual water was removed under vacuum at 80°C for 1 hour.

Step 2 - Polymerisation to Poly 2-Ethylhexyl Itaconate

The reaction mixture from step 1 was heated to 72°C and purged with nitrogen. Trigonox 25- C75 (6 x 2g) was added over 5 hours, with an addition each hour. The reaction was heated for a further 6 hours before diluting with further aromatic A150 (207.42g) to leave a pale amber, viscous clear liquid (836.29g).

Example 15

Additive compositions were prepared comprising the following components:

Table 8

Diesel fuel compositions were prepared as detailed in table 9 by addition of the additive compositions of table 8 into an R-06 BO Diesel base fuel. Table 9

Example 16

The compositions of table 9 were tested for antifoam performance using an in-house modification of the BNPe test procedure (Nf M 07-075). The results are shown in table 10:

Table 10

Example 17

Diesel fuel compositions were prepared as detailed in table 11 by dosing the additives into a Coryton B0 fuel. Additive D is a commercially available lubricity improver which is the reaction product of a C16 to C18 alkenyl substituted succinic acid with at least 2 molar equivalents of ethylene glycol.

Additive E is glycerol monoleate.

Table 11

The lubricity of compositions 18 to 20 was assessed using a high-frequency reciprocating rig (HFRR) following the standard procedure set out in IP 450.

The results are shown in table 12:

Table 12

Example 18

Diesel fuel compositions were prepared comprising the following components:

Table 13

Additive F is a multi-component additive package comprising a quaternary ammonium detergent, a Mannich detergent and an antifoam additive. It does not comprise a corrosion inhibitor.

The compositions of table 13 were tested for corrosion inhibition performance according to the standard test method ASTM D665. The results are shown in table 14:

Table 14