Compositions and methods and uses relating thereto

Abstract

A method of improving the lubricity of a diesel fuel composition, the method comprising admixing into the composition: (a) at least one nitrogen containing detergent; and (b) at least one small, functionalised aromatic compound.

Description

[0001] Compositions and methods and uses relating thereto

[0002] The present invention relates to fuel compositions and to methods and uses relating thereto. In particular the present invention relates to additive combinations for improving the lubricity of diesel fuels.

[0003] Natural untreated mineral diesel fuel comprises sulfur containing compounds and polyaromatic compounds which impart lubricity to the fuel. However hydrodesulfurisation of these fuels for environmental reasons reduces the amount of sulfur, polyaromatic compounds and other polar species present in the fuel. Fuels treated in this way therefore have low lubricity and thus are unable to adequately lubricate and protect parts of the fuel injection system leading to increased wear. It is therefore common practice to add lubricity improving additives to such fuels.

[0004] In recent years there has been an increased demand to find alternatives to mineral diesel fuels.

[0005] Biodiesel fuels comprising fatty acid esters have been known for some time. These fuels have a level of natural lubricity. However this is not always sufficient to prevent wear in an engine, especially when biodiesel is blended with other fuels.

[0006] More recent developments have led to the introduction of renewable fuels obtained by the hydrotreatment of triglyceride oils, for example vegetable oils. These materials consist primarily of saturated hydrocarbons and do not contain significant levels of aromatic or polar species. Consequently such fuels (commonly referred to as hydrotreated vegetable oils or HVO) have very low natural lubricity.

[0007] Other fuels comprising high levels of paraffinic species also have poor lubricity. Such fuels include, for example, synthetic fuels made via Fischer Tropsch synthesis, also known as gas to-liquid fuels.

[0008] Although it is known to add lubricity improvers to fuels to protect engine parts which come into contact with the fuel from wear, achieving acceptable lubricity performance can be challenging, especially for highly paraffinic fuels which contain few or no components that provide natural lubricity.

[0009] The industry standard test method for evaluating lubricity improving additives measures the wear between two metals components in a high frequency reciprocating rig (HFRR). The present inventors have surprisingly found that the addition of certain aromatic compounds in combination with nitrogen containing detergents can significantly improve the lubricity of diesel fuel compositions, including highly paraffinic diesel fuel compositions.

[0010] According to a first aspect of the present invention there is provided a method of improving the lubricity of a diesel fuel composition, the method comprising admixing into the composition: (a) at least one nitrogen containing detergent; and (b) at least one small, functionalised aromatic compound.

[0011] According to a second aspect of the present invention there is provided the use of the combination of: (a) at least one nitrogen containing detergent and (b) at least one small, functionalised aromatic compound to improve the lubricity of a diesel fuel composition.

[0012] According to a third aspect of the present invention there is provided a diesel fuel composition comprising a major proportion of a diesel fuel and:

[0013] (a) at least one nitrogen containing detergent; and

[0014] (b) at least one small, functionalised aromatic compound.

[0015] According to a fourth aspect of the present invention there is provided a method of preparing a diesel fuel composition, the method comprising dosing into a diesel fuel:

[0016] (a) at least one nitrogen containing detergent; and

[0017] (b) at least one small, functionalised aromatic compound.

[0018] Preferred features of the first, second, third and fourth aspects of the invention will now be described.

[0019] The methods and use of the first, second and fourth aspects preferably provide a fuel composition of the third aspect.

[0020] The diesel fuel composition provided by the present invention comprises a major proportion of a diesel fuel.

[0021] By diesel fuel we mean 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, railway diesel, heavy fuel oil, industrial fuel oil, etc.

[0022] 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.

[0023] 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).

[0024] In some embodiments the diesel fuel comprises mineral diesel.

[0025] In some embodiments the diesel fuel comprises biodiesel.

[0026] In some embodiments the diesel fuel comprises renewable diesel.

[0027] In some preferred embodiments the diesel fuel comprises mineral diesel and one or more further components selected from biodiesel, renewable diesel and mixtures thereof.

[0028] In some embodiments the diesel fuel comprises mineral diesel and biodiesel.

[0029] In some embodiments the diesel fuel comprises mineral diesel and renewable diesel.

[0030] In some embodiments the diesel fuel comprises mineral diesel, biodiesel and renewable diesel.

[0031] In some embodiments the diesel fuel comprises biodiesel and renewable diesel.

[0032] By mineral fuels herein we mean fuels derived wholly from mineral (i.e. petroleum) sources.

[0033] In this specification by biodiesel we mean to refer to esters of fatty acids. Such fuels are commonly referred to as first generation biodiesel. Biodiesel as defined herein contains esters of, for example, vegetable oils, animal fats and used cooking fats. This form of biodiesel may be obtained by transesterification of oils, with an alcohol, usually a monoalcohol, usually in the presence of a catalyst. The fatty acids used to produce the fuel may originate from a wide variety of natural sources including, but not limited to, vegetable oil, canola oil, safflower oil, sunflower oil, nasturtium seed oil, mustard seed oil, olive oil, sesame oil, soybean oil, com oil, peanut oil, cottonseed oil, rice bran oil, babassu nut oil, castor oil, palm oil, rapeseed oil, low erucic acid rapeseed oil, palm kernel oil, lupin oil, jatropha oil, coconut oil, flaxseed oil, evening primrose oil, jojoba oil, camelina oil, tallow, beef tallow, butter, chicken fat, lard, dairy butterfat, shea butter, used frying oil, oil miscella, used cooking oil, yellow trap grease, hydrogenated oils, derivatives of the oils, fractions of the oils, conjugated derivatives of the oils, and mixtures of any thereof.

[0034] The diesel fuel composition may comprise renewable diesel, obtained by the hydrodeoxygenation of fats and oils.

[0035] In some embodiments the diesel fuel composition may comprise a pyrolysis fuel oil, i.e. a middle distillate fraction obtained from distillation of a pyrolysis oil.

[0036] The pyrolysis oil may be obtained from the pyrolysis of any type of waste, and the components and properties of the pyrolysis oil and the distillate fraction obtained therefrom will depend on the types of waste that was pyrolysed and the pyrolysis conditions. The pyrolysis oil may, for example, be obtained from the pyrolysis of plastic waste, agricultural waste, forestry waste, waste cooking oils, algae waste, used tyres and rubber waste.

[0037] Preferred pyrolysis oils are plastic pyrolysis oils. These may be obtained from the pyrolysis of any type of plastic. However preferred plastic pyrolysis oils are obtained from the pyrolysis of one or polymers selected from low density polyethylene, high density polyethylene, ultra high density polyethylene, polypropylene, PET, polyacrylate, polynitrile and mixtures thereof.

[0038] Middle distillate fuel oils obtained from pyrolysis oils may optionally be hydrotreated and / or treated using a cracking process. However, due to the typically low aromatic and sulfur content of middle distillate fuel oils obtained from pyrolysis oils it is possible to use straight run distillates.

[0039] The diesel fuel composition used in the present invention may contain blends of any or all of the above diesel fuel compositions.

[0040] In some embodiments the diesel fuel composition may be a blended diesel fuel comprising biodiesel. In such blends the biodiesel may be present in an amount of (by volume), 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%, or up to 30%.

[0041] A fuel which comprises 100% biodiesel is denoted as B100, a fuel which comprises 90% mineral diesel and 10% biodiesel (by volume) is known as B10; fuel comprising 50% mineral diesel and 50% biodiesel (by volume) is known as B50; and so on.

[0042] Preferred diesel fuel compositions for use herein comprise less than 10% biodiesel, preferably less than 5% (by volume). In some embodiments the diesel fuel composition may be a blended diesel fuel comprising renewable diesel. In such blends the renewable diesel may be present in an amount of (by volume), 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%.

[0043] In some embodiments the fuel composition may comprise neat renewable diesel.

[0044] A fuel which comprises 100% renewable diesel is denoted as R100, a fuel which comprises 90% mineral diesel and 10% renewable diesel (by volume) is known as R10; fuel comprising 50% mineral diesel and 50% renewable diesel (by volume) is known as R50; and so on.

[0045] In some embodiments the diesel fuel comprises mineral diesel and one or more further components selected from biodiesel, renewable diesel and mixtures thereof.

[0046] In some embodiments the diesel fuel comprises mineral diesel and at least 5 vol% of a fuel selected from biodiesel, renewable diesel and mixtures thereof.

[0047] In some embodiments the diesel fuel comprises mineral diesel and at least 5 vol% biodiesel.

[0048] In some embodiments the diesel fuel comprises mineral diesel and at least 5 vol% renewable diesel.

[0049] In some embodiments the diesel fuel comprises mineral diesel and from 1 to 30 vol%, preferably from 1 to 20 vol%, more preferably from 1 to 10 vol% of a fuel selected from biodiesel, renewable diesel and mixtures thereof.

[0050] In some embodiments the diesel fuel comprises mineral diesel and from 1 to 30 vol%, preferably from 1 to 20 vol%, more preferably from 1 to 10 vol% biodiesel.

[0051] In some embodiments the diesel fuel comprises mineral diesel and from 1 to 30 vol%, preferably from 1 to 20 vol%, more preferably from 1 to 10 vol% renewable diesel.

[0052] In some embodiments the diesel fuel comprises mineral diesel; from 1 to 30 vol%, preferably from 1 to 20 vol%, more preferably from 1 to 10 vol% biodiesel; and from 1 to 30 vol%, preferably from 1 to 20 vol%, more preferably from 1 to 10 vol% renewable diesel. The present invention is particularly useful for improving the lubricity of fuels having very low natural lubricity.

[0053] In some embodiments the diesel fuel composition comprises a paraffinic fuel.

[0054] In some embodiments the diesel fuel composition may be a blended fuel comprising a paraffinic fuel and a further fuel component, for example a mineral diesel or biodiesel component.

[0055] In some preferred embodiments the paraffinic fuel provides at least 90 vol%, preferably at least 99 vol% of all fuel present in the fuel composition.

[0056] By a paraffinic fuel we mean to refer to a fuel that is highly paraffinic in nature. Paraffinic fuels typically comprise predominantly paraffin compounds. By paraffin compounds we mean to refer to saturated hydrocarbon compounds, commonly known as alkanes.

[0057] Preferably the paraffinic fuel comprises less than 5 wt% non-paraffinic compounds, preferably less than 3 wt%, more preferably less than 1 wt%, suitably less than 0.5 wt%, for example less than 0.1 wt% or less than 0.01 wt%

[0058] Preferably the paraffinic fuel comprises less than 10 wt% aromatic compounds, preferably less than 5 wt% more preferably less than 1 wt%, suitably less than 0.5 wt%.

[0059] Preferably the paraffinic fuel comprises less than 10000 ppm aromatic compounds, preferably less than 5000 ppm, suitably less than 2500 ppm.

[0060] In some embodiments the paraffinic fuel comprises less than 1000 ppm aromatic compounds, for example less than 500 ppm or less than 350 ppm.

[0061] In this specification, unless otherwise specified ppm refers to parts per million by weight.

[0062] Aromatic content may be measured by any suitable method. Such methods will be known to the person skilled in the art.

[0063] Preferably aromatic content is measured according to the standard method described in IP 391.

[0064] Preferably the paraffinic fuel has a sulfur content of less than 100 ppm, preferably less than 50 ppm, more preferably less than 10 ppm, for example less than 5 ppm. Preferably the paraffinic fuel comprises less than 5 wt% oxygenated compounds, preferably less than 3 wt%, more preferably less than 1 wt%, suitably less than 0.5 wt%, for example less than 0.1 wt% or less than 0.01 wt%.

[0065] By oxygenated compounds we mean to refer to compounds including an oxygen-containing functional group, for example esters, ethers and alcohols.

[0066] Preferably the paraffinic fuel comprises less than 5 wt% unsaturated compounds, preferably less than 3 wt%, more preferably less than 1 wt%, suitably less than 0.5 wt%, for example less than 0.1 wt% or less than 0.01 wt%.

[0067] One class of suitable paraffinic fuels are synthetic fuels. These fuels include Fischer-Tropsch fuels such as those described as GTL (gas-to-liquid) fuels, CTL (coal-to-liquid) fuels and OTL (oil sands-to-liquid).

[0068] In a preferred embodiment the paraffinic fuel comprises hydrotreated triglyceride oil. This fuel is sometimes referred to as renewable diesel fuel.

[0069] By hydrotreated triglyceride oil or renewable diesel we mean to refer to diesel fuel obtained by the hydrodeoxygenation of fats and oils. Such fuels are also often referred to as second generation biodiesel and are derived from renewable resources such as vegetable oils, fish oils and animal oils. These oils are processed, often in the refinery, using, for example, hydroprocessing. Hydroprocessing processes include the H-Bio process developed by Petrobras. Especially preferred hydrotreated triglyceride oils are hydrotreated vegetable oils or HVO fuel. HVO fuel is marketed by ConocoPhillips as Renewable Diesel and by Neste as NExBTL.

[0070] The paraffinic fuel used in the present invention may comprise fuel commonly known as 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 or hydrotreated triglyceride oil fuels, but aims to exploit the whole plant (biomass) and thereby widens the feedstock base.

[0071] The paraffinic fuel is preferably produced from raw materials of biological origin. These may suitably be selected from vegetable oils, animal fats, fish oils and mixtures thereof. Examples include rapeseed oil, canola oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, carinata oil, palm oil, palm kernel oil, peanut oil, castor oil, coconut oil, animal fats such as tallow or recycled food fats, raw materials resulting from genetic engineering, and biological raw materials produced from microorganisms such as algae and bacteria.

[0072] Preferably, the paraffinic fuel is provided by a process involving hydrodeoxygenation (HDO) and optionally isomerization steps. The hydrodeoxygenation (HDO) step results in the decomposition of the structures of the biological esters or of the triglyceride constituents, in the elimination of the oxygen-bearing, phosphorus-bearing and sulfur-bearing compounds and in the hydrogenation of olefinic bonds. The product resulting from the hydrodeoxygenation reaction may then be isomerized. A fractionation step may optionally follow the hydrodeoxygenation and isomerization steps.

[0073] Preferably the paraffinic fuel has a cetane number of between 50 and 90, preferably between 55 and 90, more preferably between 60 and 85. Cetane number is suitably measured by the standard test method set out in IP 498.

[0074] Preferably the paraffinic fuel has a cloud point of less than 25°C, more preferably less than 10°C. Suitably the paraffinic fuel has a cloud point of less than -5°C, for example less than - 10°C. Cloud point may suitably be measured using the standard test method described in IP 219.

[0075] Preferably the paraffinic fuel has a kinematic viscosity at 40°C of 1 to 20 mm2s-1, preferably from 2 to 15 mm2s-1, more preferably from 2 to 10 mm2s1, most preferably from 2 to 4.5 mm2s_1. Kinematic viscosity may be measured according to ASTM D445.

[0076] Preferably the paraffinic fuel has an initial boiling point (IBP) and a final boiling point (FBP) within the range 135 to 380°C, such as 265 to 380°C, more preferably within the range 275 to 380°C and most preferably within the range 290 to 375°C.

[0077] Preferably the paraffinic fuel has a boiling range final boiling point - initial boiling point) of less than 180°C, suitably less than 120°C, such as less than 80°C, preferably less than 70°C, suitably less than 60°C, for example from 30 to 60°C. Boiling range is used to refer to the difference between the final boiling point and the initial boiling point.

[0078] The initial boiling point, final boiling point and boiling range can be determined according to the method set out in IP 123.

[0079] The paraffinic fuel used suitably consists essentially of paraffinic compounds. Preferably the fuel may comprise n-paraffins (or straight chain alkanes), isoparaffins (i-paraffins or branched alkanes) or mixtures thereof. In some embodiments the paraffinic fuel may further comprise cycloalkanes (also known as naphthenes). Examples of paraffinic fuels comprising cycloalkanes are described, for example in W02021 / 250115.

[0080] In preferred embodiments the paraffinic fuel comprises predominately straight chain alkanes and branched alkanes.

[0081] Preferably the paraffinic fuel comprises less than 20 wt% cycloalkanes, preferably less than 10 wt%, suitably less than 5 wt%, preferably less than 1 wt%, for example less than 0.1 wt%.

[0082] For the avoidance of doubt by the term cycloalkane or napthene is used to refer to any saturated hydrocarbon compound which includes a non-aromatic cyclic moiety.

[0083] Preferably the weight of ratio n-paraffins to i-paraffins present in the paraffinic fuel is from 99:1 to 1 :99, more preferably from 90:10 to 10:90, preferably from 75:25 to 25:75. Techniques for determining the ratio of n-paraffins to i-paraffins are known to the person skilled in the art and include gas chromatography.

[0084] In some preferred embodiments the weight of ratio n-paraffins to i-paraffins present in the paraffinic fuel is from 1 :99 to 20:80.

[0085] Ratios of n-paraffins and i-paraffins present in a fuel typically depend on the hydrotreatment method used to prepare the fuel, which may also include an isomerisation step.

[0086] The paraffinic fuel used may comprise greater than 4 wt%, preferably greater than 5 wt%, of C14 to C16 n-alkanes.

[0087] The paraffinic fuel may comprise greater than 5 wt%, preferably greater than 7 wt%, more preferably greater than 10 wt%, of C14 to C18 n-alkanes.

[0088] The paraffinic fuel may comprise less than 8 wt%, preferably less than 6 wt%, of C14 to C16 n- alkanes.

[0089] The paraffinic fuel may comprise less than 20 wt%, preferably less than 18 wt%, more preferably less than 16 wt%, of C14 to C18 n-alkanes.

[0090] The paraffinic fuel may comprise greaterthan 4 wt%, preferably greater than 5 wt%, of C14 to C16 n-alkanes and less than 8 wt%, preferably less than 6 wt%, of C14 to C16 n-alkanes. The paraffinic fuel may comprise greater than 5 wt%, preferably greater than 7 wt%, more preferably greater than 10 wt%, of C14 to C18 n-alkanes and less than 20 wt%, preferably less than 18 wt%, more preferably less than 16 wt%, of C14 to C18 n-alkanes.

[0091] The paraffinic fuel may comprise from 4 to 8 wt%, preferably from 5 to 6 wt%, of C14 to C16 n- alkanes.

[0092] The paraffinic fuel may comprise from 5 to 20 wt%, preferably from 7 to 18 wt%, more preferably from 10 to 16 wt%, of C14 to C18 n-alkanes.

[0093] The paraffinic fuel may comprise from 3 to 30 wt% of C6 to C24 n-alkanes (i.e. n-paraffin).

[0094] Suitably the paraffinic fuel complies with the standard specification set out in EN15940.

[0095] In preferred embodiments the paraffinic fuel is a hydrotreated triglyceride oil, for example a hydrotreated vegetable oil.

[0096] Preferably the paraffinic fuel is a hydrotreated triglyceride oil having an aromatic content of less than 2500 ppm, preferably less than 500 ppm; and a sulfur content of less than 50 ppm.

[0097] Preferably the paraffinic fuel is a hydrotreated triglyceride oil fuel having a cetane number of between 50 and 90, preferably between 55 and 90 (according to IP 498); a cloud point of less than 10°C, preferably less than -5°C (according to IP 219); and a kinematic viscosity at 40°C of from 1 to 20 mm2s-1, preferably from 2 to 10 mm2s-1(according to ASTM 445).

[0098] Preferably the paraffinic fuel is a hydrotreated triglyceride oil having an initial boiling point and a final boiling point within the range 135 to 380°C, such as 265 to 380°C, preferably 290 to 375°C and a boiling range (final boiling point - initial boiling point) of less than 180°C, suitably less than 120°C, such as less than 80°C, preferably 30 to 60°C.

[0099] In the present invention (a) at least one nitrogen containing detergent and (b) at least one small, functionalised aromatic compound are added to a diesel fuel.

[0100] The present invention involves the use of at least one nitrogen containing detergent as an additive. By this we mean that the invention may include the use of one nitrogen containing detergent as an additive or the use of multiple nitrogen containing detergents as multiple additives. For the avoidance of doubt each additive used in the present invention may comprise a mixture of compounds and references to an additive or the additive include mixtures, unless otherwise stated. In particular mixtures of isomers and mixtures of homologues are within the scope of the invention. The skilled person will appreciate that commercial sources of some of the additive compounds described herein may comprise mixtures of isomers and / or mixtures of homologues.

[0101] Any suitable nitrogen containing detergent may be used as component (a).

[0102] Preferably the or each nitrogen containing detergent is selected from:

[0103] (A) a quaternary ammonium salt additive;

[0104] (B) the reaction product of a carboxylic acid-derived acylating agent and an amine;

[0105] (C) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol;

[0106] (D) the reaction product of a carboxylic acid-derived acylating agent and hydrazine;

[0107] (E) a salt formed by the reaction of a carboxylic acid with a C1 to C10 alkyl amine such as di-n-butylamine or tri-n-butylamine;

[0108] (F) 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; and

[0109] (G) a compound of formula (I):

[0110] A— L— R1

[0111] (I) wherein:

[0112] A is a nitrogen-containing group;

[0113] L is either a bond or a linker group; and

[0114] R1is an optionally substituted hydrocarbyl group; and wherein the compound has a nitrogen content of at least 4% by mass.

[0115] The or each more nitrogen containing detergent is preferably selected from:

[0116] (A) quaternary ammonium salt additives; (B) the reaction product of a carboxylic acid-derived acylating agent and an amine; and

[0117] (C) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol.

[0118] In some embodiments component (a) may comprise (A) a quaternary ammonium salt additive.

[0119] The term “quaternary ammonium compounds” is used herein interchangeably with “quaternary ammonium salt additive” and “quaternary ammonium salt”.

[0120] The or each quaternary ammonium compound is suitably the reaction product of a nitrogencontaining species having at least one tertiary amine group and a quaternising agent.

[0121] The nitrogen-containing species having at least one tertiary amine group may be selected from any compound including a tertiary amine functional group.

[0122] Suitably the nitrogen-containing species having at least one tertiary amine group may be selected from:

[0123] (i) the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group;

[0124] (ii) a Mannich reaction product comprising a tertiary amine group;

[0125] (iii) a polyalkylene substituted amine having at least one tertiary amine group;

[0126] (iv) a tertiary amine of formula R5R6R7N, wherein each of R5, R6and R7is independently an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group;

[0127] (v) a cyclic tertiary amine; and

[0128] (vi) a polyetheramine compound.

[0129] The nitrogen-containing species having at least one tertiary amine group is reacted with a quaternising agent. Any suitable quaternising agent may be used.

[0130] In some embodiments the nitrogen-containing species having at least one tertiary amine group is (i) 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.

[0131] Suitable hydrocarbyl substituted acylating agents for use herein include fatty acids, i.e. compounds of formula RCOOH in which R is an alkyl or alkenyl group having 6 to 36 carbon atoms, preferably 8 to 30 carbon atoms or 12 to 24 carbon atoms. One preferred fatty acid is oleic acid.

[0132] The hydrocarbyl substituted acylating agent may be based on a hydrocarbyl substituted mono- di- or polycarboxylic acid or a reactive equivalent thereof. In some preferred embodiments the hydrocarbyl substituted acylating agent is a hydrocarbyl substituted succinic acid compound, for example a hydrocarbyl substituted succinic acid or succinic anhydride.

[0133] The hydrocarbyl substituent preferably comprises at least 10, more preferably at least 12, for example 30 or 50 carbon atoms. It may comprise up to about 200 carbon atoms. Preferably the hydrocarbyl substituent has a number average molecular weight (Mn) of between 170 to 2800, for example from 250 to 1500, preferably from 450 to 1500 and more preferably 450 to 1100. An Mn of 700 to 1300 is especially preferred.

[0134] The hydrocarbyl based substituents may be made from homo- or interpolymers (e.g. copolymers, terpolymers) of mono- and di-olefins having 2 to 10 carbon atoms, for example ethylene, propylene, but-1-ene, isobutene, butadiene, isoprene, 1 -hexene, 1 -octene, etc. Preferably these olefins are 1 -monoolefins. The hydrocarbyl substituent may also be derived from the halogenated (e.g. chlorinated or brominated) analogs of such homo- or interpolymers. Alternatively the substituent may be made from other sources, for example monomeric high molecular weight alkenes (e.g. 1-tetra-contene) and chlorinated analogs and hydrochlorinated analogs thereof, aliphatic petroleum fractions, for example paraffin waxes and cracked and chlorinated analogs and hydrochlorinated analogs thereof, white oils, synthetic alkenes for example produced by the Ziegler-Natta process (e.g. poly(ethylene) greases) and other sources known to those skilled in the art. Any unsaturation in the substituent may if desired be reduced or eliminated by hydrogenation according to procedures known in the art.

[0135] In some preferred embodiments component (i) comprises the reaction product of a hydrocarbyl-substituted succinic acid derivative and an alcohol or amine also including a tertiary amine group.

[0136] 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:

[0137] (1) 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-, 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);

[0138] (2) 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);

[0139] (3) 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.

[0140] In this specification, unless otherwise stated references to optionally substituted alkyl groups may include aryl-substituted alkyl groups and references to optionally-substituted aryl groups may include alkyl-substituted or alkenyl-substituted aryl groups.

[0141] Preferred hydrocarbyl-based substituents are poly-(isobutene)s. Such compounds are known in the art. Thus in some especially preferred embodiments the hydrocarbyl substituted acylating agent is a polyisobutenyl substituted succinic acid or succinic anhydride.

[0142] Polyisobutenyl substituted succinic anhydrides are especially preferred acylating agents.

[0143] The preparation of polyisobutenyl substituted succinic anhydrides (PIBSA) is documented in the art. Suitable processes include thermally reacting polyisobutenes with maleic anhydride (see for example US-A-3,361 ,673 and US-A-3, 018,250), or reacting a halogenated, in particular a chlorinated, polyisobutene (PIB) with maleic anhydride (see for example US-A- 3,172,892). Alternatively, the polyisobutenyl succinic anhydride can be prepared by mixing the polyolefin with maleic anhydride and passing chlorine through the mixture (see for example GB-A-949,981). Conventional polyisobutenes and so-called "highly-reactive" polyisobutenes are suitable for use in the invention. Highly reactive polyisobutenes in this context are defined as polyisobutenes wherein at least 50%, preferably 70% or more, of the terminal olefinic double bonds are of the vinylidene type as described in EP0565285. Particularly preferred polyisobutenes are those having more than 80 mol% and up to 100% of terminal vinylidene groups such as those described in EP1344785.

[0144] The person skilled in the art will appreciate that in the preparation of PIBSAs from the reaction of PIB with maleic acid (MA), a mixture of products will result. Typically reaction mixtures include some unreacted PIB, some PIBSA from the reaction of PIB with one MA (monomaleated PIBSA) and some PIBSA from the reaction of PIB with two MA (bismaleated PIBSA). The fraction of bismaleated product as a proportion of the total PIBSA product may be referred to as the bismaleation level (BML). Suitable PIBSAs for use in preparing additive (i) may have a BML of up to 90%, suitably up to 70%, for example 1 to 50% or 2 to 30%.

[0145] Other preferred hydrocarbyl groups include those having an internal olefin for example as described in the applicant’s published application W02007 / 015080.

[0146] An internal olefin as used herein means any olefin containing predominantly a non-alpha double bond, that is a beta or higher olefin. Preferably such materials are substantially completely beta or higher olefins, for example containing less than 10% by weight alpha olefin, more preferably less than 5% by weight or less than 2% by weight. Typical internal olefins include Neodene 1518 IO available from Shell.

[0147] Internal olefins are sometimes known as isomerised olefins and can be prepared from alpha olefins by a process of isomerisation known in the art, or are available from other sources. The fact that they are also known as internal olefins reflects that they do not necessarily have to be prepared by isomerisation.

[0148] In some preferred embodiments the additive of the present invention comprises the quaternised reaction product of an alcohol or amine including a tertiary amino group and an optionally substituted succinic acid or anhydride thereof of formula (A1) or (A2): wherein R1is an optionally substituted hydrocarbyl group. Preferably R1is an optionally substituted alkyl or alkenyl group.

[0149] R1may 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.

[0150] Preferably R1is an unsubstituted alkyl or alkenyl group. The substituted succinic acid or anhydrides may suitably be prepared by reacting maleic anhydride with an alkene.

[0151] In some preferred embodiments R1has a number average molecular weight of from 100 to 5000, preferably from 300 to 4000, suitably from 450 to 2500, for example from 450 to 2000 or from 450 to 1500.

[0152] In especially preferred embodiments the additive of the present invention comprises a quaternary ammonium compound prepared from the reaction product of a hydrocarbyl substituted succinic acid or an anhydride thereof substituted with a polyisobutenyl group having a number average molecular weight of 450 to 1500 and an alcohol or amine which further includes a tertiary amino group.

[0153] In some embodiments the substituted succinic acid or anhydride thereof may comprise a mixture of compounds including groups R1of different lengths. In such embodiments any reference to the molecular weight of the group R1relates to the number average molecular weight of all of that group for all compounds in the composition.

[0154] In preferred embodiments R1is a polyisobutenyl group, preferably having a number average molecular weight of from 100 to 5000, preferably from 200 to 2400, suitably from 450 to 1500.

[0155] In some embodiments R1is an optionally substituted Ci to C50 alkyl or alkenyl group, for example a Cs to C40 alkyl or alkenyl group, suitably C to C36 alkyl or alkenyl group. In some embodiments the additive of the present invention comprises a quaternary ammonium compound prepared from the reaction product of a succinic acid or anhydride having a C10 to C30, preferably a C20 to C24 alkyl or alkenyl group and an amine or alcohol which further includes a tertiary amino group.

[0156] Preferred hydrocarbyl substituted acylating agents for use herein are polyisobutenyl substituted succinic anhydrides or PIBSAs. Preferably the succinic acid or anhydride thereof is substituted with a polyisobutenyl group having a number average molecular weight of from 170 to 2800, preferably 450 to 1500. 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.

[0157] 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. This initial product is a monomaleated PIBSA.

[0158] The monomaleated PIBSA may have the structure (A) or (B):

[0159] The double bond in the monomaleated product can react with a further molecule of maleic anhydride to form a bismaleated PIBSA having the structure (C) or (D):

[0160] Thus it is possible to provide a hydrocarbyl group which is substituted with more than one succinic acid moiety.

[0161] The skilled person will appreciate that the hydrocarbyl substituted succinic acid derived acylating agents used in the invention typically comprise mixtures of compounds, for example mixtures of monomaleated and bismaleated PIBSAs. The PIBSAs may be defined in terms of their level of bismaleation.

[0162] One way in which this may be determined is by calculating the average number of succinic acid moieties per molecule of acylating agent.

[0163] A monomaleated PIBSA has one succinic acid moiety per module.

[0164] A bismaleated PIBSA has two succinic acid moieties per molecule.

[0165] 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.

[0166] The average number of succinic acid moieties per molecule of acylating agent is sometimes referred to in the art as the “P value”.

[0167] Suitably the or each quaternary ammonium compound is prepared from a hydrocarbyl substituted succinic acid derived acylating agent comprising on average from 1 to 2 succinic acid moieties per molecule.

[0168] In some preferred embodiments the present invention may involve the use of quaternary ammonium compounds 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] By succinic acid moiety we mean to include residues of succinic acid present in diacid or anhydride form.

[0174] The hydrocarbyl substituted 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.

[0175] Examples of suitable compounds able to react with the hydrocarbyl substituted succinic acid derived acylating agent and which include a tertiary amine group can include but are not limited to: N,N-dimethylaminopropylamine, N,N-diethylaminopropylamine, N,N-dimethylamino ethylamine. The nitrogen or oxygen containing compounds capable of condensing with the acylating agent and further having a tertiary amino group can further include amino alkyl substituted heterocyclic compounds such as 1-(3-aminopropyl)imidazole and 4-(3- aminopropyl)morpholine, 1-(2-aminoethyl)piperidine, 3,3-diamino-N-methyldipropylamine, and 3'3-aminobis(N,N-dimethylpropylamine). Other types of nitrogen or oxygen containing compounds capable of condensing with the acylating agent and having a tertiary amino group include alkanolamines including but not limited to triethanolamine, trimethanolamine, N,N- dimethylaminopropanol, N,N-dimethylaminoethanol, N,N-diethylaminopropanol, N,N- diethylaminoethanol, N,N-diethylaminobutanol, N,N,N-tris(hydroxyethyl)amine, N,N,N- tris(hydroxymethyl)amine, N,N,N-tris(aminoethyl)amine, N,N-dibutylaminopropylamine and 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, N,N,N'-trimethylaminoethylethanolamine and 3-(2-(dimethylamino)ethoxy) propylamine.

[0176] Preferred nitrogen-containing species having at least one tertiary amino group of type (i) are formed by the reaction of a hydrocarbyl-substituted acylating agent and an amine of formula (B1) or (B2):

[0177] R2R2

[0178] N - X - NHR4N - X - [O(CR42)m]nOH

[0179] R3R3

[0180] (B1) wherein R2and R3are the same or different alkyl groups having from 1 to 36 carbon atoms; X is an alkylene group having from 1 to 20 carbon atoms; n is from 0 to 20; m is from 1 to 5; and R4is hydrogen or a Ci to C36 alkyl group.

[0181] To form the quaternary ammonium salt additives of the present invention a quaternising agent may be reacted with a compound formed by the reaction of a hydrocarbyl substituted acylating agent and an amine of formula (B1) or (B2).

[0182] When a compound of formula (B1) is used, R4is 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 R4is alkyl it may be straight chained or branched. It may be substituted for example with a hydroxy or alkoxy substituent. Preferably R4is not a substituted alkyl group. More preferably R4is selected from hydrogen, methyl, ethyl, propyl, butyl and isomers thereof. Most preferably R4is hydrogen.

[0183] When a compound of formula (B2) is used, each R4is preferably hydrogen or a Ci to Ce alkyl group. More preferably each R4is selected from hydrogen, methyl, ethyl, propyl, butyl and isomers thereof. Most preferably each R4is hydrogen or methyl.

[0184] When a compound of formula (B2) 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 (B2) is an alcohol. In some preferred embodiments the hydrocarbyl substituted acylating agent is reacted with a diamine compound of formula (B1).

[0185] R2and R3are the same or different alkyl, alkenyl or aryl groups having from 1 to 22 carbon atoms. In some embodiments R2and R3may be joined together to form a ring structure, for example a piperidine or imidazole moiety. R2and R3may be branched alkyl or alkenyl groups. Each may be substituted, for example with a hydroxy or alkoxy substituent.

[0186] R2and R3may each independently be a Ci to C alkyl group, preferably a Ci to C10 alkyl group. R2and R3may independently be methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, or an isomer of any of these. Preferably R2and R3is each independently Ci to C4 alkyl. Preferably R2is methyl. Preferably R3is methyl.

[0187] X is a bond or alkylene group having from 1 to 20 carbon atoms. In preferred embodiments when X is an alkylene group this group may be straight chained or branched. The alkylene group may include a cyclic structure therein. It may be optionally substituted, for example with a hydroxy or alkoxy substituent. In some embodiments the alkylene group may be optionally interrupted with one or more heteroatoms, for example O, NH or N-alkyl.

[0188] X is preferably an alkylene group having 1 to 16 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, for example 2 to 6 carbon atoms or 2 to 5 carbon atoms. Most preferably X is an ethylene, propylene or butylene group, especially a propylene group.

[0189] Examples of compounds of formula (B1) suitable for use herein include 1-aminopiperidine, 1- (2-aminoethyl)piperidine, 1- (3-aminopropyl)-2-pipecoline, 1-methyl-(4-methylamino)piperidine, 4-(1-pyrrolidinyl)piperidine, 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-1 ,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-dimethylpropy lamine), N'-(3-(dimethylamino)propyl)-N,N-dimethyl 1 ,3-propanediamine, 3-(2- (dimethylamino)ethoxy)propylamine or combinations thereof. In some preferred embodiments the compound of formula (B1) 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, or combinations thereof.

[0190] An especially preferred compound of formula (B1) is dimethylaminopropylamine.

[0191] Examples of compounds of formula (B2) 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 aminoethanol, 2-dimethylamino-2-methyl-1 -propanol; trimethanolamine, N,N,N- tris(hydroxymethyl)amine, N,N,N-tris(aminoethyl)amine, N,N-bis(3-dimethylaminopropyl)-N- isopropanolamine and N-(3-dimethylaminopropyl)-N,N-diisopropanolamine.

[0192] In some preferred embodiments the compound of formula (B2) is selected from N,N- dimethylaminopropanol, 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.

[0193] One preferred compound of formula (B2) is dimethylaminopropanol.

[0194] An especially preferred compound of formula (B2) is N,N-dimethyl-1 ,3-diaminopropane (dimethylaminopropylamine).

[0195] Some preferred acylating agents for use in the preparation of the quaternary ammonium salt additives of the present invention are polyisobutene-substituted succinic acids or succinic anhydrides. When a compound of formula (B2) 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 (B1) in which R4is hydrogen the resulting product may be a succinimide or a succinamide. When a succinic acylating agent is reacted with a compound of formula (B1) in which R4is not hydrogen the resulting product is an amide.

[0196] Thus in some embodiments component (i) may be the reaction product of a succinic acid derivative and an amine or alcohol which is an ester or an amide and which also includes a further unreacted carboxylic acid group. This further carboxylic acid functional group can react with another amine or alcohol when an excess is used to form a diester or the diamide. For the avoidance of doubt, succinic esters include the monoester compounds having the general formula (C1) and the diester compounds having the general formula (C2); succinimides have the general formula (C3); and succinamides include the monoamide compounds having the general formula (C4) and the diamide compounds having have the general formula (C5):

[0197] It will be appreciated isomers of (C1) and (C4) may be formed in which the other carboxylic acid group is esterified / amidated.

[0198] The groups R shown in formulae (C1) to (C5) include a tertiary amino group. This group may be quaternised by reaction with a quaternising agent. For compounds of formula (C2) or (C5) which include two tertiary amino groups, each of these may be reacted with a quaternising agent to provide a diquaternary ammonium compound including two cationic moieties. Compounds of this type to provide a diquaternary ammonium compound including two cationic moieties. Compounds of this type are described (for use as diesel detergents) in US9365787.

[0199] In some embodiments mixtures of compounds having formula (C1) and (C2) or mixtures containing compounds (C3) and / or (C4) and / or (C5) may be used.

[0200] Also within the scope of the invention are compounds in which a monoamide and monoester are formed within the same succinic acid group.

[0201] In preferred embodiments a succinic acid derivative is reacted with an amine (also including a tertiary amine group) under conditions to form a succinimide.

[0202] In some embodiments the acid / anhydride and the alcohol / amine are reacted in a molar ratio of 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. Preferably the acid / anhydride and the alcohol / amine are reacted in an approximately 1 :1 molar ratio, for example from 1 .2:1 to1 :1 .2.

[0203] Suitably the quaternary ammonium salt additive of the present invention comprises a compound prepared from the reaction product of an optionally substituted succinic acid or anhydride thereof, preferably a hydrocarbyl substituted succinic acid or anhydride thereof, and an alcohol or amine selected from dimethylaminopropanol, dimethylaminopropylamine, N,N- diethyl-1 ,3- diaminopropane, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N- dibutylethylenediamine, 3-(2-(dimethylamino)ethoxy)propylamine or combinations thereof.

[0204] In some especially preferred embodiments the quaternary ammonium salt additives of the present invention comprise quaternary ammonium compounds prepared from tertiary amines (i) wherein the tertiary amine is prepared from an amine which includes a tertiary amino group (for example dimethylamino propylamine) and a polyisobutylene-substituted succinic anhydride. The number average molecular weight of the polyisobutylene substituent is preferably from 450 to 1300, more preferably from 900 to 1100.

[0205] The quaternary ammonium salt additives of the present invention comprising compounds derived from tertiary amines (i) may be prepared by any suitable method. Such methods will be known to the person skilled in the art and are exemplified herein. Typically the quaternary ammonium compounds will be prepared by heating the quaternising agent and a compound prepared by the reaction of a hydrocarbyl substituted acylating agent with an amine of formula (B1) or (B2) in an approximate 1 :1 molar ratio, optionally in the presence of a solvent. The resulting crude reaction mixture may be added directly to a diesel fuel, optionally following removal of solvent. Any by-products or residual starting materials still present in the mixture have not been found to cause any detriment to the performance of the additive. Thus the present invention may provide a diesel fuel composition comprising the reaction product of a quaternising agent and the reaction product of a hydrocarbyl substituted acylating agent and an amine formula (B1) or (B2).

[0206] In some embodiments the quaternary ammonium compounds for use in the present invention are the quaternised reaction product of a fatty acid (for example oleic acid) and a compound of formula (B1) or (B2) (for example dimethylaminopropyl amine).

[0207] In some embodiments the nitrogen-containing species having at least one tertiary amine group may be (ii) a Mannich reaction product including a tertiary amine. The preparation of quaternary ammonium salts formed from nitrogen-containing species including component (ii) is described in US2008 / 0052985. The Mannich reaction product having a tertiary amine group is prepared from the reaction of a hydrocarbyl-substituted phenol, an aldehyde and an amine.

[0208] The hydrocarbyl substituent of the hydrocarbyl substituted phenol can have 6 to 400 carbon atoms, suitably 30 to 180 carbon atoms, for example 10 or 40 to 110 carbon atoms. This hydrocarbyl substituent can be derived from an olefin or a polyolefin. Useful olefins include alpha-olefins, such as 1 -decene, which are commercially available.

[0209] The polyolefins which can form the hydrocarbyl substituent can be prepared by polymerizing olefin monomers by well known polymerization methods and are also commercially available.

[0210] Some preferred polyolefins include polyisobutylenes having a number average molecular weight of 400 to 3000, in another instance of 400 to 2500, and in a further instance of 400 or 450 to 1500.

[0211] The hydrocarbyl-substituted phenol can be prepared by alkylating a phenol with an olefin or polyolefin described above, such as, a polyisobutylene or polypropylene, using well-known alkylation methods.

[0212] In some embodiments the phenol may include a lower molecular weight alkyl substituent for example a phenol which carries one or more alkyl chains having a total of less 28 carbon atoms, preferably less than 24 carbon atoms, more preferably less than 20 carbon atoms, preferably less than 18 carbon atoms, preferably less than 16 carbon atoms and most preferably less than 14 carbon atoms.

[0213] A monoalkyl phenol may be preferred, suitably having from 4 to 20 carbons atoms, preferably 6 to 18, more preferably 8 to 16, especially 10 to 14 carbon atoms, for example a phenol having a C12 alkyl substituent.

[0214] The aldehyde used to form the Mannich detergent can have 1 to 10 carbon atoms, and is generally formaldehyde or a reactive equivalent thereof such as formalin or paraformaldehyde.

[0215] The amine used to form the Mannich detergent can be a monoamine or a polyamine.

[0216] Examples of monoamines include but are not limited to ethylamine, dimethylamine, diethylamine, n-butylamine, dibutylamine, allylamine, isobutylamine, cocoamine, stearylamine, laurylamine, methyllaurylamine, oleylamine, N-methyl-octylamine, dodecylamine, diethanolamine, morpholine, and octadecylamine. Suitable polyamines may be selected from any compound including two or more amine groups. Suitable polyamines include polyalkylene polyamines, for example in which the alkylene component has 1 to 6, preferably 1 to 4, most preferably 2 to 3 carbon atoms. Preferred polyamines are polyethylene polyamines.

[0217] The polyamine has 2 to 15 nitrogen atoms, preferably 2 to 10 nitrogen atoms, more preferably 2 to 8 nitrogen atoms.

[0218] In especially preferred embodiments the amine used to form the Mannich detergent comprises a diamine. Suitably it includes a primary or secondary amine which takes part in the Mannich reaction and in addition a tertiary amine.

[0219] In preferred embodiments component (ii) comprises the product directly obtained from a Mannich reaction and comprising a tertiary amine. For example the amine may comprise a single primary or secondary amine which when reacted in the Mannich reaction forms a tertiary amine which is capable of being quaternised. Alternatively the amine may comprise a primary or secondary amine capable of taking part in the Mannich reaction and also a tertiary amine capable of being quaternised. However component (ii) may comprise a compound which has been obtained from a Mannich reaction and subsequently reacted to form a tertiary amine, for example a Mannich reaction may yield a secondary amine which is then alkylated to a tertiary amine.

[0220] In some embodiments the nitrogen-containing species comprising at least one tertiary amine group is (iii) a polyalkylene substituted amine having at least one tertiary amine group.

[0221] The preparation of quaternary ammonium salt additives in which the nitrogen-containing species includes component (iii) is described for example in US2008 / 0113890.

[0222] The polyalkene-substituted amines having at least one tertiary amino group of the present invention may be derived from an olefin polymer and an amine, for example ammonia, momoamines, polyamines or mixtures thereof. They may be prepared by a variety of methods such as those described and referred to in US2008 / 0113890.

[0223] Suitable preparation methods include, but are not limited to: reacting a halogenated olefin polymer with an amine; reacting a hydroformylated olefin with a polyamine and hydrogenating the reaction product; converting a polyalkene into the corresponding epoxide and converting the epoxide into the polyalkene substituted amine by reductive amination; and hydrogenation of a p-aminonitrile. The olefin monomers from which the olefin polymers are derived include polymerizable olefin monomers characterised by the presence of one or more ethylenically unsaturated groups for example ethylene, propylene, 1 -butene, isobutene, 1 -octene, 1 ,3-butadiene and isoprene.

[0224] The olefin monomers are usually polymerizable terminal olefins. However, polymerizable internal olefin monomers can also be used to form the polyalkenes.

[0225] Examples of terminal and internal olefin monomers, which can be used to prepare the polyalkenes according to conventional, well-known polymerization techniques include: ethylene; propylene; butenes, including 1 -butene, 2-butene and isobutylene; 1 -pentene; 1- hexene; 1 -heptene; 1 -octene; 1 -nonene; 1 -decene; 2-pentene; propylene-tetramer; diisobutylene; isobutylene trimer; 1 ,2-butadiene; 1 ,3-butadiene; 1 ,2-pentadiene; 1 ,3- pentadiene; 1 ,4-pentadiene; isoprene; 1 ,5-hexadiene; 2-methyl-5-propyl-1 -hexene; 3-pentene; 4-octene; and 3, 3-dimethyl-1 -pentene.

[0226] Suitably the polyalkene substituent of the polyalkene-substituted amine is derived from a polyisobutylene.

[0227] The amines that can be used to make the polyalkene-substituted amine include ammonia, monoamines, polyamines, or mixtures thereof, including mixtures of different monoamines, mixtures of different polyamines, and mixtures of monoamines and polyamines (which include diamines). The amines include aliphatic, aromatic, heterocyclic and carbocylic amines.

[0228] The monomers and polyamines suitably include at least one primary or secondary amine group.

[0229] Suitable monoamines are generally substituted with a hydrocarbyl group having 1 to about 50 carbon atoms, preferably 1 to 30 carbon atoms. Saturated aliphatic hydrocarbon radicals are particularly preferred.

[0230] Examples of suitable monoamines include methylamine, ethylamine, diethylamine, 2- ethylhexylamine, di-(2-ethylhexyl)amine, n-butylamine, di-n-butylamine, allylamine, isobutylamine, cocoamine, stearylamine, laurylamine, methyllaurylamine and oleylamine.

[0231] Aromatic monoamines include those monoamines wherein a carbon atom of the aromatic ring structure is attached directly to the amine nitrogen. Examples of aromatic monoamines include aniline, di(para-methylphenyl)amine, naphthylamine, and N-(n-butyl)aniline. Examples of aliphatic substituted, cycloaliphatic-substituted, and heterocyclic-substituted aromatic monoamines include: para-dodecylaniline, cyclohexyl-substituted naphthylamine, and thienyl-substituted aniline respectively.

[0232] Hydroxy amines are also included in the class of useful monoamines. Examples of hydroxylsubstituted monoamines include ethanolamine, di-3-propanolamine, 4-hydroxybutylamine; diethanolamine, and N-methyl-2-hydroxypropylamine.

[0233] The amine of the polyalkene-substituted amine can be a polyamine. The polyamine may be aliphatic, cycloaliphatic, heterocyclic or aromatic.

[0234] Examples of suitable polyamines include alkylene polyamines, hydroxy containing polyamines, arylpolyamines, and heterocyclic polyamines.

[0235] Ethylene polyamines, are especially useful for reasons of cost and effectiveness. Suitable ethylene polyamines are described in relation to the first aspect.

[0236] Suitable hydroxy containing polyamines include hydroxyalkyl alkylene polyamines having one or more hydroxyalkyl substituents on the nitrogen atoms and can be prepared by reacting alkylenepolyamines with one or more alkylene oxides. Examples of suitable hydroxyalkylsubstituted polyamines include: N-(2-hydroxyethyl)ethylene diamine, N,N-bis(2- hydroxyethyl)ethylene diamine, 1-(2-hydroxyethyl) piperazine, monohydroxypropyl-substituted diethylene triamine, dihydroxypropyl-substituted tetraethylene pentamine, propyl and N-(3- hydroxybutyl)tetramethylene diamine.

[0237] Suitable arylpolyamines are analogous to the aromatic monoamines mentioned above except for the presence within their structure of another amino nitrogen. Some examples of arylpolyamines include N,N’-di-n-butyl-para-phenylene diamine and bis-(para- aminophenyl)methane.

[0238] Suitable heterocyclic mono- and polyamines will be known to the person skilled in the art. Specific examples of such heterocyclic amines include N-aminopropylmorpholine, N- aminoethylpiperazine, and N,N’-diaminoethylpiperazine. Hydroxy heterocyclic polyamines may also be used for example N-(2-hydroxyethyl)cyclohexylamine, 3- hydroxycyclopentylamine, parahydroxy-aniline and N-hydroxyethylpiperazine.

[0239] Examples of polyalkene-substituted amines can include: poly(propylene)amine, poly(butene)amine, N,N-dimethylpolyisobutyleneamine; N-polybutenemorpholine, N- poly(butene)ethylenediamine, N-poly(propylene) trimethylenediamine, N- poly(butene)diethylenetriamine, N’,N’-poly(butene)tetraethylenepentamine, and N,N-dimethyl- N’poly(propylene)-1 ,3 propylenediamine.

[0240] The number average molecular weight of the polyalkene-substituted amines can range from 500 to 5000, or from 500 to 3000, for example from 1000 to 1500.

[0241] In some embodiments the nitrogen-containing species having at least one tertiary amine group is (iv) a tertiary amine of formula R5R6R7N, wherein each of R5, R6and R7is independently an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group.

[0242] In some embodiments of the present invention the tertiary amine of formula R5R6R7N may be a small compound of low complexity and low molecular weight. In some embodiments the tertiary amine may be a complex molecule and / or a molecule of high molecular weight which includes a tertiary amine group.

[0243] The tertiary amine compounds of formula R5R6R7N preferably do not include any primary or secondary amine groups. In some embodiments they may be derived from compounds including these groups but preferably these have been subsequently reacted to form additional tertiary amine species. The tertiary amine compound formula R5R6R7N may contain more than one tertiary amine group. However tertiary amine compounds including primary or secondary amine groups are within the scope of the invention provided these groups do not prevent quaternisation of the tertiary amine species.

[0244] Tertiary amines (iv) for use herein are preferably compounds of formula R5R6R7N, wherein each of R5, R6and R7is independently an optionally substituted alkyl, alkenyl, aryl, aralkyl or alkaryl group.

[0245] R5, R6and R7may be the same or different. In some preferred embodiments R5and R6are the same and R7is different.

[0246] Preferably each of R5and R6is independently an optionally substituted alkyl, alkenyl, aryl, aralkyl or alkaryl group having from 1 to 50 carbon atoms, preferably from 1 to 40 carbon atoms, more preferably from 1 to 30 carbon atoms.

[0247] Each of R5and R6may be optionally substituted with one or more groups selected from halo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano, mercapto, alkylmercapto, dialkylamino, nitro, nitroso, and sulphoxy. The alkyl groups of these substituents may be further substituted. Preferably each of R5and R6is independently an optionally substituted alkyl or alkenyl group. Preferably each of R5and R6is independently an optionally substituted alkyl group. In some embodiments each of R5and R6is independently an optionally substituted alkyl or alkenyl group having from 1 to 50 carbon atoms, preferably from 1 to 40 carbon atoms, more preferably from 1 to 30 carbon atoms, suitably from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 10 carbon atoms, suitably from 1 to 8 carbon atoms, for example from 1 to 6 carbon atoms.

[0248] In some preferred embodiments R5is an optionally substituted alkyl or alkenyl group, preferably having from 1 to 10, preferably from 1 to 4 carbon atoms. Preferably R5is an alkyl group. It may be a substituted alkyl group, for example a hydroxy substituted alkyl group. Preferably R5is an unsubstituted alkyl group. The alkyl chain may be straight-chained or branched. Preferably R5is selected from methyl, ethyl, propyl and butyl, including isomers thereof. Most preferably R5is methyl.

[0249] In some preferred embodiments R6is an optionally substituted alkyl or alkenyl group, preferably having from 1 to 10, preferably from 1 to 4 carbon atoms. Preferably R6is an alkyl group. It may be a substituted alkyl group, for example a hydroxy substituted alkyl group. Preferably R6is an unsubstituted alkyl group. The alkyl chain may be straight-chained or branched. Preferably R6is selected from methyl, ethyl, propyl and butyl, including isomers thereof. Most preferably R6is methyl.

[0250] In some embodiments R7is an optionally substituted alkyl or alkenyl group having from 1 to 50 carbon atoms, preferably from 1 to 40 carbon atoms, more preferably from 1 to 30 carbon atoms, suitably from 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, more preferably from 1 to 10 carbon atoms, suitably from 1 to 8 carbon atoms, for example from 1 to 6 carbon atoms. Suitable substituents include halo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano, mercapto, alkylmercapto, amino, alkylamino, nitro, nitroso, sulphoxy, amido, alkyamido, imido and alkylimido. The alkyl groups of these substituents may be further substituted.

[0251] In some embodiments R7is an optionally substituted alkyl or alkenyl group, preferably having from 1 to 10, preferably from 1 to 4 carbon atoms. Suitably R7is an optionally substituted alkyl group. Preferably R7is a substituted alkyl group. Preferred substituents include alkoxy and hydroxyl groups.

[0252] In some preferred embodiments R7is a hydroxyl-substituted alkyl group. The alkyl chain may be straight-chained or branched. Most preferably R7is a hydroxyethyl group. Suitable tertiary amine compounds of formula R5R6R7N include simple alkylamino and hydroxyalkylamino compounds; trialkylamino compounds having a high molecular weight substituent; Mannich reaction products including a tertiary amine and substituted acylated amines or alcohols including a tertiary amine.

[0253] Simple alkylamino and hydroxyalkyl amino compounds are preferably compounds of formula R5R6R7N, wherein each of R5, R6and R7is an alkyl group or a hydroxyalkyl group. Each of R5, R6and R7may be the same or different. In some embodiments each of R5, R6and R7is independently selected from an alkyl or hydroxyalkyl group having 1 to 10, preferably 1 to 6 carbon atoms, for example 1 to 4 carbon atoms. Each of R5, R6and R7may be independently selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl and hydroxyhexyl. The amine of formula R5R6R7N may be a trialkylamine, a dialkylhydroxyalkylamine, a dihydroxyalkylalkylamine or a trihydroxyalkylamine. There are many different compounds of this type and these will be known to the person skilled in the art.

[0254] In some embodiments one or two of the groups R5, R6and R7is a short chain alkyl group having 1 to 6, preferably 1 to 4 carbon atoms and the other one or two groups is a longer chain alkyl or group having 6 to 30, preferably 10 to 24 carbon atoms.

[0255] In some embodiments each of R5and R6is Ci to C4 alkyl, preferably methyl and R7is an alkyl or alkenyl group having 6 to 36, preferably 10 to 30, for example 12 to 24 carbon atoms.

[0256] Compounds of this type include, for example, dimethyloctadecylamine and hexadecyl dimethyl amine.

[0257] In order to provide a quaternary ammonium compound, the hexadecyl dimethyl amine may be quaternised by reaction with propylene oxide (for example 1 to 3 molar equivalent of propylene oxide) and polyisobutylene succinic acid (for example 1 molar equivalent of polyisobutylene succinic acid).

[0258] For example in some embodiments R5is Ci to C4 alkyl, preferably methyl and each R6and R7is an alkyl or alkenyl having 6 to 36, preferably 8 to 30, for example 10 to 24 carbon atoms.

[0259] Compounds of this type include, for example, hexadecyl dimethyl amine, N-methyl N-N- ditallowamine and dicocomethyl amine.

[0260] Especially preferred tertiary amine compounds of formula R5R6R7N include N,N-dimethyl ethanolamine, dimethyloctadecylamine and N-methyl-N,N-ditallowamine. In some embodiments the nitrogen-containing species having at least one tertiary amine group is (v) a cyclic tertiary amine.

[0261] Suitable cyclic amines have the formula (D1): wherein R6an optionally substituted alkyl, alkenyl, aryl, aralkyl or alkaryl group, and R9together with N forms a heterocycle.

[0262] Preferably heterocycle has less than 12 carbon atoms. Preferably R6has less than 8 carbon atoms.

[0263] Preferably R6is an optionally substituted alkyl, alkenyl or aryl group having from 1 to 7 carbon atoms, preferably from 1 to 5 carbon atoms, more preferably from 1 to 4 carbon atoms.

[0264] R6may be optionally substituted with one or more groups selected from halo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano, mercapto, alkylmercapto, dialkylamino, nitro, nitroso, and sulphoxy. The alkyl groups of these substituents may be further substituted.

[0265] Preferably R6is an optionally substituted alkyl or alkenyl group. Preferably R6is an optionally substituted alkyl group. Preferably R6is an optionally substituted alkyl or alkenyl group having from 1 to 7 carbon atoms, preferably from 1 to 6 carbon atoms, more preferably from 1 to 5 carbon atoms, suitably from 1 to 4 carbon atoms, preferably from 1 to 3 carbon atoms, more preferably from 1 to 2 carbon atoms.

[0266] Preferably R6is an optionally substituted alkyl or alkenyl group, preferably having from 1 to 6, preferably from 1 to 4 carbon atoms. Preferably R6is an alkyl group. It may be a substituted alkyl group, for example a hydroxy substituted alkyl group. Preferably R6is an unsubstituted alkyl group or a hydroxy alkyl group. More preferably R6is an unsubstituted alkyl group. The alkyl chain may be straight-chained or branched. Preferably R6is selected from methyl, ethyl, propyl and butyl, including isomers thereof. Most preferably R6is methyl. In some embodiments R10, R11and N together form an aromatic ring and the cyclic amine may have the structure (D2):

[0267] In such embodiments the total number of carbon atoms in groups R10and R11is preferably less than 19.

[0268] R9together with N may form an aliphatic heterocyclic group or an aromatic heterocyclic group. Thus they form a heterocyclic ring. There may be one or more further heteroatoms in the ring. Suitably the ring may include one or more further atoms selected from N, O and S.

[0269] The heterocyclic group formed by R9and N may be substituted or unsubstituted; i.e. there may be one or more substituents bonded to atoms that form the ring. Suitable substituents include halo (especially chloro and fluro); hydroxy, alkoxy, keto, acyl, cyano, mercapto, alkylmercapto, alkyl, alkenyl, aryl, dialkylamino, alkylamino, nitro, nitroso, and sulphoxy. The alkyl, alkenyl and aryl groups of these substituents may be further substituted.

[0270] The heterocyclic group may be substituted with a further cyclic group i.e. it may be part of a bicyclic heterocyclic group.

[0271] In some preferred embodiments the heterocyclic group formed by N and R9is not substituted.

[0272] Preferably the group formed by R9and N is a heterocyclic group having from 3 to 12 atoms in the ring. The atoms in the ring include carbon atoms and other atoms. Preferably the heterocyclic ring includes 3 to 10 atoms, preferably 4 to 8, more preferably 5 to 7 atoms.

[0273] In some preferred embodiments the heterocyclic group contains only carbon and nitrogen atoms within the ring.

[0274] The heterocyclic group formed by R9and N may be aliphatic or aromatic.

[0275] In some preferred embodiments R9and N together form an aliphatic or aromatic heterocycle having 5 to 7 atoms in the ring. Suitable aliphatic heterocyclic groups include those based on pyrrolidine, piperidine, morpholine and piperazine.

[0276] Suitable aliphatic heterocyclic groups include unsaturated heterocycles that are not aromatic, i.e. they may contain one or more double bonds, for example those based on dihydropyrrole.

[0277] Suitable aromatic heterocyclic groups including those based on pyrrole, pyrazole, pyridine, imidazole, pyrimidine, isoxzole, quinolone, oxazole, and pyrazole.

[0278] In especially preferred embodiments R9and N together form an imidazole moiety or a pyrrolidine moiety.

[0279] Suitably R9contains 3 to 11 carbon atoms (and optional heteroatoms with the ring), preferably 3 to 10 carbon atoms, preferably 3 to 9 carbon atoms, suitably 3 to 8 carbon atoms, preferably 3 to 7 carbon atoms, more preferably 3 to 6 carbon atoms, for example 3 to 5 or 3 to 4 carbon atoms.

[0280] Preferably R9contains less than 8 carbon atoms.

[0281] The compound of formula (D1) or (D2) is a cyclic tertiary amine. By this we mean to refer to an amine group in which the nitrogen atom is part of a heterocyclic ring and is preferably further bonded to another group.

[0282] Suitably the compound of formula (D1) or (D2) is a cyclic tertiary amine having less than 18 carbon atoms. Preferably it has less than 16 carbon atoms, suitably less than 14 carbon atoms, preferably less than 12 carbon atoms, for example less than 10 carbon atoms, less than 8 carbon atoms or less than 6 carbon atoms.

[0283] Suitably the cyclic amine compound is a compound of formula (D1) and is an N-substituted heterocyclic amine. Preferably it is an N-alkyl heterocyclic amine having 5 to 7 atoms in the heterocyclic ring.

[0284] In some preferred embodiments the tertiary amine is an N-methyl cyclic amine wherein the heterocyclic ring moiety may include one or more further heteroatoms such as O, N or S and may be aliphatic or non-aromatic.

[0285] There are many different compounds of this type and these will be known to the person skilled in the art. Some suitable cyclic amines for use herein are based on N-alkyl heterocycles, for example N- methyl heterocycles, selected from pyrazole, pyrrolidine, piperidine, morpholine, piperazine, pyrrole, imidazole and dihydropyrrole.

[0286] Other suitable amines include those based on the above in which the heterocyclic ring includes one or more further alkyl, alkenyl or aryl substituents, provided the total number of carbon atoms in the tertiary amine is less than 19. For example compounds which include one, two or three methyl groups bonded to carbon atoms within the heterocyclic ring are within the scope of the invention.

[0287] Some suitable cyclic amines for use herein include those based on heterocycles in which R10, R11and N together form an aromatic ring, for example those based on piperidine, pyrimidine, isoxazole and oxazole.

[0288] Other suitable amines include those based on the above in which the heterocyclic ring includes one or more further alkyl, alkenyl or aryl substituents, provided the total number of carbon atoms in the tertiary amine is less than 19.

[0289] Tertiary amine compounds including primary or secondary amine groups are within the scope of the invention provided these groups do not prevent quaternisation of the tertiary amine species.

[0290] The cyclic tertiary amine compounds preferably do not include any free primary or secondary amine groups. The tertiary amine compound of formula R9==NR6may contain more than one tertiary amine group.

[0291] Some preferred cyclic amine compounds include 1-methyl pyrrolidine, 1 -methylimidazole, 1 ,2- dimethyl-1 H-imidazole, pyridine and mixtures and isomers thereof. 8-hydroxyquinoline could also be used.

[0292] Especially preferred tertiary amine compounds include methyl pyrrolidine and methyl imidazole.

[0293] In some embodiments the nitrogen-containing species having at least one tertiary amine group is (vi) a polyetheramine compound.

[0294] Some preferred polyetheramine compounds are polyoxyalkylene amines. In some preferred embodiments the polyetheramine compound has the general formula (D3): wherein R12is H or a hydrocarbyl group having from 1 to 30 carbon atoms; R13and R14are each independently hydrogen or lower alkyl having from about 1 to about 6 carbon atoms and each R13and R14is independently selected in each --O — CHR13-CHR14-- unit; and x is an integer of from 1 to 100, preferably 5 to 50; A is NR15R16, NR17NR15R16, OR17NR15R16, OCONR15R16or a polyamine moiety having about 2 to about 12 nitrogen atoms, about 4 to about 40 carbon atoms and including at least one tertiary amine group; wherein each of R15and R16is independently an alkyl group having about 1 to about 20 carbon atoms in each alkyl group, and R17is an alkylene group having 1 to 20 carbon atoms.

[0295] In a preferred embodiment R12is H or a C1-C30 alkyl preferably a C4-C20 alkyl.

[0296] In another preferred embodiment R12is an alkylphenyl group, wherein the alkyl group has from about 1 to about 24 carbon atoms.

[0297] Preferably, one of R13and R14is lower alkyl of 1 to 4 carbon atoms, and the other is hydrogen. More preferably, one of R13and R14is methyl or ethyl, and the other is hydrogen.

[0298] Preferably each of R15and R16is an alkyl group having from about 1 to about 20 carbon atoms in each alkyl group, preferably about 1 to about 6 carbon atoms, more preferably about 1 to about 4 carbon atoms. Suitably R17is an alkyl group having from about 1 to about 20 carbon atoms in each alkyl group, preferably about 1 to about 6 carbon atoms, more preferably about 1 to about 4 carbon atoms.

[0299] In some embodiments A is a polyamine moiety comprising a tertiary amine group and having from about 2 to about 12 nitrogen atoms and from about 4 to about 40 carbon atoms.

[0300] In some embodiments, the compound of formula (D3) may be derived by alkoxylation of an N,N dialkyl hydroxyalkylamine such as N,N-dimethylaminoethanol or N,N- dimethylaminopropanol. In other embodiments the compound of formula D4 may be derived by alkoxylation of a C1-C30 alcohol preferably a C4-C20 alcohol followed by amination with ammonia further followed by alkylation of the amine. Such processes are described in US2013225463.

[0301] Other preferred features of the polyetheramine compound are also described in US2013225463.

[0302] In some preferred embodiments, the quaternary ammonium salt additive comprises compounds prepared by the reaction of a quaternising agent and (i) 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.

[0303] The quaternary ammonium salt additives (A) are prepared by the reaction of a nitrogencontaining species having at least one tertiary amine group and a quaternising agent.

[0304] Any compound capable of reacting with the tertiary amine group to form a quaternary ammonium cation may be used as the quaternising agent.

[0305] In some embodiments following reaction with a quaternising agent an ion exchange reaction may be carried out to provide a quaternary ammonium compound having a different anion.

[0306] The quaternary ammonium compounds used in the present invention may be prepared by reaction of a tertiary amine with a quaternising agent selected from an ester of a carboxylic acid, epoxides optionally in combination with an acid, dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, alkyl halides, alkyl sulfonates, sulfones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, alkyl nitrites, alkyl nitrates, hydroxides, N-oxides or mixtures thereof.

[0307] In fuel applications it is often desirable to reduce the levels of halogen-, sulfur-, and phosphorus-containing species. Thus if a quaternising agent containing such an element is used it may be advantageous to carry out a subsequent reaction to exchange the counterion. For example a quaternary ammonium salt formed by reaction with an alkyl halide could be subsequently reacted with sodium hydroxide and the sodium halide salt removed by filtration.

[0308] The quaternising agent can include halides, such as chloride, iodide or bromide; hydroxides; sulphonates; bisulphites, alkyl sulphates, such as dimethyl sulphate; sulphones; phosphates; C1-12 alkylphosphates; di C1-12 alkylphosphates; borates; C1-12 alkylborates; nitrites; nitrates; carbonates; bicarbonates; alkanoates; O,O-di C1-12 alkyldithiophosphates; or mixtures thereof. Preferably the quaternising agent is selected from 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.

[0309] In one embodiment the quaternising agent may be derived from dialkyl sulphates such as dimethyl sulphate, N-oxides, sulphones such as propane and butane sulphone; alkyl, acyl or aralkyl halides such as methyl and ethyl chloride, bromide or iodide or benzyl chloride, and a hydrocarbyl (or alkyl) substituted carbonates. If the quaternising agent is benzyl chloride, the aromatic ring is optionally further substituted with alkyl or alkenyl groups. The hydrocarbyl (or alkyl) groups of the hydrocarbyl substituted carbonates may contain 1 to 50, 1 to 20, 1 to 10 or 1 to 5 carbon atoms per group. In one embodiment the hydrocarbyl substituted carbonates contain two hydrocarbyl groups that may be the same or different. Examples of suitable hydrocarbyl substituted carbonates include dimethyl or diethyl carbonate.

[0310] Preferred quaternising agents for use herein are esters of a carboxylic acid or an epoxide, optionally in combination with an acid.

[0311] In one preferred embodiment the quaternising agent is an ester of formula R18COOR19.

[0312] In such embodiments R19is a Ci to C7 alkyl group and R18COO is preferably the residue of a carboxylic acid selected from a substituted aromatic carboxylic acid, an a-hydroxycarboxylic acid and a polycarboxylic acid.

[0313] Preferred ester quaternising agents are compounds of formula (E): in which R18is an optionally substituted alkyl, alkenyl, aryl or alkylaryl group which may comprise a further carboxy derived functional group; and R19is a Ci to C22 alkyl, aryl or alkylaryl group.

[0314] The compound of formula (E) is suitably an ester of a carboxylic acid capable of reacting with a tertiary amine to form a quaternary ammonium compound. Suitable quaternising agents include esters of carboxylic acids having a pKa of 3.5 or less.

[0315] The compound of formula (E) is preferably an ester of a carboxylic acid selected from a substituted aromatic carboxylic acid, an a-hydroxycarboxylic acid and a polycarboxylic acid.

[0316] In some preferred embodiments the compound of formula (E) is an ester of a substituted aromatic carboxylic acid and thus R18is a substituted aryl group.

[0317] In such embodiments R18is suitably a substituted aryl group having 6 to 10 carbon atoms, preferably a phenyl or naphthyl group, most preferably a phenyl group. R18is suitably substituted with one or more groups selected from carboalkoxy, nitro, cyano, hydroxy, SR20or NR21R22. Each of R21and R22may be hydrogen or optionally substituted alkyl, alkenyl, aryl or carboalkoxy groups. Preferably each of R21and R22is hydrogen or an optionally substituted Ci to C22 alkyl group, preferably hydrogen or a Ci to C alkyl group, preferably hydrogen or a Ci to Cw alkyl group, more preferably hydrogen or a Ci to C4 alkyl group. Preferably R21is hydrogen and R22is hydrogen or a Ci to C4 alkyl group. Most preferably R21and R22are both hydrogen. Preferably R18is an aryl group substituted with one or more groups selected from hydroxyl, carboalkoxy, nitro, cyano and NH2. R18may be a poly-substituted aryl group, for example trihydroxyphenyl. Preferably R18is a mono-substituted aryl group. Preferably R18is an ortho substituted aryl group. Suitably R18is substituted with a group selected from OH, NH2, NO2 or COOMe. Preferably R18is substituted with an OH or NO2 group. Suitably R18is a hydroxy substituted aryl group. Most preferably R18is a 2-hydroxyphenyl group.

[0318] Preferably R19is an alkyl or alkaryl group. R19may be a Ci to Cw alkyl group, preferably a Ci to Cw alkyl group, suitably a Ci to Cs alkyl group. R19may be Ci to Cw alkaryl group, preferably a Ci to Cw alkaryl group, suitably a Ci to Cs alkaryl group. R19may be methyl, ethyl, propyl, butyl, pentyl, benzyl or an isomer thereof. Preferably R19is benzyl or methyl. Most preferably R19is methyl.

[0319] Some especially preferred compounds of formula (E) are esters of salicylic acid such as benzyl salicylate, methyl salicylate, ethyl salicylate, n and / -propyl salicylate, and butyl salicylate.

[0320] An especially preferred compound of formula (E) is methyl salicylate.

[0321] In some embodiments the compound of formula (E) is an ester of an a-hydroxycarboxylic acid.

[0322] In such embodiments R18is R23CR24OH and the compound of formula (E) has the structure: wherein R23and R24are 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 EP1254889.

[0323] Examples of compounds of formula (E) in which R18COO is the residue of an a- hydroxycarboxylic acid include methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl-, and allyl esters of 2-hydroxyisobutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl-, and allyl esters of 2-hydroxy-2-methylbutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl-, and allyl esters of 2-hydroxy-2-ethylbutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl-, and allyl esters of lactic acid; and methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, allyl-, benzyl-, and phenyl esters of glycolic acid. Of the above, a preferred compound is methyl 2-hydroxyisobutyrate.

[0324] In some embodiments the compound of formula (E) 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.

[0325] In such embodiments R18includes a carboxy derived functional group. This is preferably present in the form of an ester, that is the one or more further acid groups present in the group R18are in esterified form. Preferred esters are Ci to C4 alkyl esters.

[0326] Compound (E) 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 (E) is dimethyl oxalate.

[0327] In preferred embodiments the compound of formula (E) is an ester of a carboxylic acid having a pKaof 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.

[0328] Compound (E) 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. Suitably the compound of formula (E) may be selected from dimethyl oxalate, methyl 2- nitrobenzoate, dimethylphthalate, dimethyltartrate and methyl salicylate

[0329] Preferred compounds of formula (E) include dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

[0330] Most preferred ester quaternising agents are dimethyl oxalate and methyl salicylate.

[0331] In some preferred embodiments the quaternising agent is an epoxide, optionally in combination with an acid.

[0332] Any suitable epoxide compound may be used. Suitable epoxide compounds are those of formula: wherein each of R25, R26, R27, R28is independently selected from hydrogen or an optionally substituted alkyl, alkenyl or aryl group, provided at least one of R25, R26, R27and R28is hydrogen.

[0333] Preferably at least two of R25, R26, R27and R28are hydrogen. Most preferably three of R25, R26, R27and R28are hydrogen. R25, R26, R27and R28may be all hydrogen.

[0334] In the structure above and the definitions which follow R25and R26are interchangeable and thus when these groups are different either enantiomer or diastereomer may be used as component (b).

[0335] In the structure above and the definitions which follow R27and R28are interchangeable and thus when these groups are different either enantiomer or diastereomer may be used as component (b).

[0336] Preferably R25is hydrogen or an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group. R25may suitably be selected from hydrogen and phenyl. Most preferably R25is hydrogen.

[0337] Preferably R26is hydrogen or an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group. Most preferably R26is hydrogen. Preferably R27is hydrogen or an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group. Most preferably R27is hydrogen.

[0338] Preferably R28is hydrogen or an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group.

[0339] In some preferred embodiments R28is an optionally substituted aryl group. For example R28may be phenyl.

[0340] In some preferred embodiments R28is an optionally substituted alkyl or alkenyl group. R28may be an alkyl group, for example an unsubstituted alkyl group. R28may be an alkyl group having 1 to 50 carbon atoms, preferably from 1 to 30 carbon atoms, suitably 1 to 20 carbon atoms, preferably from 1 to 12 carbon atoms, for example from 1 to 8 or from 1 to 4 carbon atoms.

[0341] In some embodiments R28is hydrogen.

[0342] In some embodiments R28is the moiety CH2OR29or CH2OCOR30wherein each of R29and R30may be an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group.

[0343] Preferably R25, R26and R27are hydrogen and R28is selected from phenyl, an optionally substituted alkyl or alkenyl group having 1 to 20 carbon atoms, hydrogen, CH2OR29or CH2OCOR30wherein each of R29and R30is an optionally substituted alkyl or aryl group having from 1 to 20 carbon atoms.

[0344] R29is preferably an optionally substituted alkyl or aryl group, preferably having from 1 to 30 carbon atoms, preferably from 1 to 20 carbon atoms, suitably from 1 to 12 carbon atoms. When R29is an alkyl group it may be straight-chained or branched. In some embodiments it is branched. R29may be an optionally substituted phenyl group.

[0345] In one embodiment R29is a 2-methyl phenyl group. In another embodiment R29is CH2C(CH2CH3)CH2CH2CH2CH3.

[0346] R30may be an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group.

[0347] R30is preferably an optionally substituted alkyl or aryl group, preferably having from 1 to 30 carbon atoms, preferably from 1 to 20 carbon atoms, suitably from 1 to 12 carbon atoms. When R30is an alkyl group it may be straight-chained or branched. In some preferred embodiments it is branched. R30may be an optionally substituted phenyl group. In one embodiment R30is C(CH3)R2 wherein each R is an alkyl group. The R groups may be the same or different.

[0348] Preferably R30is an alkyl group having 1 to 5 carbon atoms. In some embodiments R30may include an oxygen atom in the carbon chain, i.e. R30may include an ether functional group.

[0349] Suitable epoxide compounds for use herein as quaternising agents include ethylene oxide, propylene oxide, butylene oxide, pentylene oxide, hexylene oxide, heptylene oxide, dodecylene oxide, alkyl glycidyl ethers, for example 2-ethylhexyl glycidyl ether or isopropyl glycidyl ether, alkyl glycidyl esters styrene oxide, stilbene oxide and other C2 to C30 hydrocarbyl groups.

[0350] Some preferred epoxide compounds for use herein as quaternising agents include styrene oxide, ethylene oxide, propylene oxide, butylene oxide, stilbene oxide, dodecylene oxide 2- ethylhexyl glycidyl ether and isopropyl glycidyl ether. Styrene oxide, butylene oxide, 2- ethylhexyl glycidyl ether and propylene oxide are especially preferred.

[0351] Typically epoxide quaternising agents are used in combination with an acid. However in embodiments in which the nitrogen-containing species having at least one tertiary amine group includes (i) the reaction product of a substituted succinic acid which is an ester or an amide and which also includes a further unreacted carboxylic acid group, an additional acid may be omitted and the hydrocarbyl epoxide may be used alone as the quaternising agent. It is believed that formation of the quaternary ammonium salt is promoted by protonation by the carboxylic acid group also present in the molecule.

[0352] In such embodiments in which a further acid is not used, the quaternary ammonium compound is suitably prepared in a protic solvent. Suitable protic solvents include water, alcohols (including polyhydric alcohols) and mixtures thereof. Preferred protic solvents have a dielectric constant of greater than 9.

[0353] In preferred embodiments the epoxide quaternising agent is used in combination with an acid. Any suitable acid may be used. In preferred embodiments the acid is an organic acid, preferably a carboxylic acid. Suitable carboxylic acids include monocarboxylic acids and polycarboxylic acids. Preferably the acid is a monocarboxylic acid or a dicarboxylic acid.

[0354] For the avoidance of doubt the acid suitably activates the epoxide and forms the anionic counterion of the quaternary ammonium compound. In some embodiments a subsequent ion exchange reaction may be carried out but this is not preferred. Any compound which includes a carboxylic acid functional group may be used. In some embodiments the acid may be a very small simple molecule. Examples of suitable small simple acids include formic acid, acetic acid, propionic acid and butyric acid.

[0355] In some embodiments the acid may be a simple fatty acid compound. However the acid may also be a more complex molecule including additional acid functional groups.

[0356] Suitable fatty acids include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, linoleic acid, linoelaidic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, undecylenic acid and docosahexenoic acid.

[0357] Suitable complex acids include optionally substituted phthalic acids and succinic acid derivatives.

[0358] Some preferred species of this type are hydrocarbyl substituted phthalic acid or succinic acid derivatives. Hydrocarbyl substituted succinic acid derivatives are especially preferred.

[0359] In one embodiment the hydrocarbyl group is preferably a polyisobutenyl group, preferably having a molecular weight of from 100 to 5000, preferably from 300 to 4000, suitably from 450 to 2500, for example from 450 to 2000 or from 450 to 1500.

[0360] In one embodiment the hydrocarbyl group is an alkyl or alkenyl group having 6 to 30 carbon atoms, preferably 10 to 26 carbon atoms, more preferably 12 to 24 carbon atoms, suitably 16 to 20 carbon atoms, for example 18 carbon atoms.

[0361] In one embodiment the hydrocarbyl group is an alkyl or alkenyl group having 6 to 50 carbon atoms, preferably 12 to 40 carbon atoms, more preferably 18 to 36 carbon atoms, suitably 24 to 36 carbon atoms, for example 30 carbon atoms.

[0362] The succinic acid derivative may be polyisobutylene succinic acid (for example which may be used with an epoxide quaternising agent such as propylene oxide). The polyisobutylene succinic acid may form a salt via one or both of its acid groups. When only one of its acid groups is used to form a salt it may maintain a free acid group.

[0363] In embodiments in which the acid has more than one acid functional group the further groups may be present as the free acid or the ester. Where there is more than one free acid group there may be an equivalent number of cations. For example in some embodiments the quaternary ammonium compound may comprise a dicarboxylate dianion and two quaternary ammonium ions. Compounds of this type are described in EP3024913.

[0364] Some preferred epoxide quaternising agents for use herein include styrene oxide, butylene oxide, propylene oxide or 2-ethylhexyl glycidyl ether in combination with a monocarboxylic acid, suitably acetic acid.

[0365] Some preferred epoxide quaternising agents for use herein include styrene oxide, butylene oxide, propylene oxide or 2-ethylhexyl glycidyl ether in combination with a polycarboxylic acid, suitably a polyisobutenyl substituted succinic acid.

[0366] In some preferred embodiments the quaternising agent is selected from an ester of a carboxylic acid, an epoxide optionally in combination with an acid and chloroacetic acid or a salt thereof.

[0367] In some preferred embodiments the quaternary ammonium compound is the reaction product of a tertiary amine of a tertiary amine of formula R5R6R7N, wherein each of R5, R6and R7is independently an optionally substituted alkyl or alkenyl group having 1 to 40 carbon atoms; an epoxide; and a monocarboxylic acid or a dicarboxylic acid.

[0368] In some embodiments the quaternary ammonium compound is the reaction product of a tertiary amine of a tertiary amine of formula R5R6R7N, wherein each of R5, R6and R7is an alkyl group or a hydroxyalkyl group having 1 to 10 carbon atoms; an epoxide; and a monocarboxylic acid or a dicarboxylic acid.

[0369] In some embodiments the quaternary ammonium compound is the reaction product of a tertiary amine of a tertiary amine of formula R5R6R7N, wherein one or two of the groups R5, R6and R7is a short chain alkyl group having 1 to 6, preferably 1 to 4 carbon atoms and the other one or two groups is a longer chain alkyl or group having 6 to 30, preferably 10 to 24 carbon atoms; an epoxide; and a monocarboxylic acid or a dicarboxylic acid.

[0370] In some embodiments the quaternary ammonium compound is the reaction product of a tertiary amine; an epoxide, preferably propylene oxide; and an optionally substituted succinic acid, preferably a polyisobutenyl substituted succinic acid wherein the tertiary amine has the formula R5R6R7N, wherein one or two of the groups R5, R6and R7is a short chain alkyl group having 1 to 6, preferably 1 to 4 carbon atoms and the other one or two groups is a longer chain alkyl or group having 6 to 30, preferably 10 to 24 carbon atoms. Preferred quaternary ammonium salt additives for use in the present invention include at least one reaction product of:

[0371] (x) the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group; and

[0372] (y) a quaternising agent selected from: an ester of a carboxylic acid; and an epoxide, optionally in combination with an acid.

[0373] Preferred quaternary ammonium salt additives for use in the present invention include at least one reaction product of:

[0374] (x) the reaction product of a hydrocarbyl-substituted succinic acid derived acylating agent including an average of at least 1.2 succinic acid moieties per molecule and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group; and

[0375] (y) a quaternising agent selected from: an ester of a carboxylic acid; and an epoxide, optionally in combination with an acid.

[0376] More preferred quaternary ammonium salt additives of the present invention include at least one reaction product of:

[0377] (x) a polyisobutenyl substituted succinic acid or anhydride thereof and an amine or alcohol which further includes a tertiary amine group; and

[0378] (y) a quaternising agent 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; and an epoxide selected from one or more of ethylene oxide, propylene oxide, butylene oxide, pentylene oxide, hexylene oxide, heptylene oxide, isopropyl glycidyl ether, styrene oxide, stilbene oxide and other C2 to C30 hydrocarbyl groups, optionally in combination with an acid.

[0379] Some especially preferred quaternary ammonium salt additives of the present invention include at least one reaction product of:

[0380] (x) a polyisobutenyl substituted succinic acid or anhydride thereof having a PIB molecular weight of 170 to 2800, preferably 450 to 1500 and an amine or alcohol selected from dimethylaminopropanol, dimethylaminopropylamine, N,N-diethyl-1 ,3-diaminopropane, N,N- dimethylethylenediamine, N,N-diethylethylenediamine, N,N-dibutylethylenediamine, or combinations thereof; and

[0381] (y) a quaternising agent selected from dimethyl oxalate, methyl 2-nitrobenzoate, dimethylphthalate, dimethyltartrate, methyl salicylate; and an epoxide selected from styrene oxide, 2-ethylhexyl glycidyl ether, ethylene oxide, propylene oxide, butylene oxide, 2-ethylhexyl glycidyl ether, stilbene oxide and isopropyl glycidyl ether, in combination with an acid. Some especially preferred quaternary ammonium salt additives of the present invention include at least one reaction product of:

[0382] (x) a polyisobutenyl substituted succinic acid or anhydride thereof having a PIB molecular weight of 170 to 2800, preferably 450 to 1500 and an amine or alcohol selected from dimethylaminopropanol and dimethylaminopropylamine; and

[0383] (y) a quaternising agent selected from dimethyl oxalate; methyl salicylate; and an epoxide selected from styrene oxide, propylene oxide and butylene oxide, in combination with an acid.

[0384] Some especially preferred quaternary ammonium salt additives of the present invention include at least one reaction product of:

[0385] (x) a polyisobutenyl substituted succinic acid or anhydride thereof having a PIB molecular weight of 170 to 2800, preferably 450 to 1500 and including an average of at least 1 .2 succinic acid moieties per molecule, and an amine or alcohol selected from dimethylaminopropanol and dimethylaminopropylamine; and

[0386] (y) a quaternising agent selected from dimethyl oxalate; methyl salicylate; and an epoxide selected from styrene oxide, propylene oxide and butylene oxide, in combination with an acid.

[0387] In some embodiments the quaternary ammonium salt additives for use in the present invention are the quaternised reaction product of a fatty acid (for example oleic acid) and an amine of formula (B1) or (B2), for example dimethylaminopropyl amine.

[0388] In such embodiments, suitable quaternising agents for reaction with the reaction product described above are dialkyl sulfates, benzyl halides, hydrocarbyl substituted carbonates, hydrocarbyl substituted epoxides in combination with an acid, alkyl halides, alkyl sulfonates, sulfones, hydrocarbyl substituted phosphates, hydrocarbyl substituted borates, N-oxides, chloroacetic acid or salts thereof, or mixtures thereof. Preferably the quaternising agent is chloroacetic acid or salts thereof, for example sodium chloroacetate.

[0389] In one preferred embodiment, the quaternary ammonium salt additive is the quaternised reaction product of oleic acid and dimethylaminopropyl amine, wherein the reaction product has been quaternised with chloroacetic acid or a salt thereof.

[0390] Other preferred quaternary ammonium compounds include dimethyl dialkyl nitrite compounds in which the alkyl groups have from 6 to 36, preferably 8 to 24, for example 10 to 20 carbon atoms.

[0391] In some embodiments component (a) may comprise (B) the reaction product of a carboxylic acid-derived acylating agent and an amine. These compounds may also be referred to herein in general as acylated nitrogen-containing compounds.

[0392] 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.

[0393] 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.

[0394] Conventional polyisobutenes and so-called "highly-reactive" polyisobutenes are suitable for use in the invention. These are suitably as previously described herein in relation to the preparation of some preferred quaternary ammonium detergents.

[0395] 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.

[0396] 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.

[0397] 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.

[0398] 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 a preferred embodiment the reaction product of a carboxylic acid-derived acylating agent and an amine (ii) comprises the reaction product of a polyisobutene-substituted succinic acid or succinic anhydride and a polyethylene polyamine selected from ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethylene-heptamine and mixtures and isomers thereof; wherein polyisobutene substituent has a number average molecular weight of between 500 and 2000, preferably between 600 and 1200.

[0399] In some embodiments component (a) may comprise (C) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol.

[0400] Preferably component (C) comprises the product of a Mannich reaction between:

[0401] (x) an aldehyde;

[0402] (y) an amine; and

[0403] (z) an optionally substituted phenol.

[0404] 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.

[0405] Suitable amines for use in preparing the Mannich additive include monoamines and polyamines. One suitable monoamine is butylamine.

[0406] 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. The polyamine may, for example, be selected from ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, heptaethyleneoctamine, propane-1 ,2-diamine, 2(2-amino-ethylamino)ethanol, and N1,N1-bis (2-aminoethyl) ethylenediamine (N(CH2CH2NH2)3). Most preferably the polyamine comprises tetraethylenepentamine or especially ethylenediamine.

[0407] 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.

[0408] Preferred Mannich reaction products used in the present invention are typically formed by reacting components (x), (y) and (z) in a molar ratio of 1 .1 to 5 parts (x) to 1 part (y) to 1 .1 to 2 parts (z).

[0409] Suitable Mannich reaction products and methods of preparing such additives will be known to the person skilled in the art and include the compounds described, for example, in the applicant’s publications W02009040582 and WO2013017887.

[0410] Preferred Mannich reaction product additives are the reaction product of formaldehyde, polyethylene polyamine; and a para-substituted monoalkyl phenol.

[0411] An especially preferred Mannich reaction product additive for use herein is the reaction product of dodecyl phenol, formaldehyde and ethylene diamine.

[0412] In some embodiments component (a) may comprise (D) the reaction product of a carboxylic acid-derived acylating agent and hydrazine.

[0413] Suitably the additive comprises the reaction product between a hydrocarbyl-substituted succinic acid or anhydride and hydrazine.

[0414] 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.

[0415] Hydrazine has the formula NH2-NH2 Hydrazine may be hydrated or non-hydrated. Hydrazine monohydrate is preferred.

[0416] 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.

[0417] In some embodiments component (a) may comprise (E) a salt formed by the reaction of a carboxylic acid with di-n-butylamine or tri-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.

[0418] In a preferred embodiment, the carboxylic acid comprises tall oil fatty acid (TOFA).

[0419] Further preferred features of additives of this type are described in EP1900795.

[0420] In some embodiments component (a) may comprise (F) 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.

[0421] Further preferred features of additive compounds of this type are as defined in US2009 / 0282731 .

[0422] In some embodiments component (a) may comprise (G) a compound of formula (I):

[0423] A— L— R1

[0424] (I) wherein:

[0425] A is a nitrogen-containing group;

[0426] L is either a bond or a linker group; and

[0427] R1is an optionally substituted hydrocarbyl group; and wherein the compound has a nitrogen content of at least 4% by mass.

[0428] The nitrogen-containing group A may be a nitrogen-containing heterocycle, for example an optionally substituted piperazine, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, quinazoline, a five-membered heterocyclic ring such as pyrazole or imidazole or a benzo-fused five-membered heterocyclic ring such as benzimidazole.

[0429] The nitrogen-containing group A may be a non-cyclic nitrogen-containing group having the formula (II): wherein n is from 1 to 10.

[0430] L is suitably a bond, an amide, a succinimide, a succinic acid or an amide of a succinic acid. Compounds of this type are further described in W02023 / 209370 and WO2023 / 209369.

[0431] Preferably component (a) is selected from:

[0432] (A) a quaternary ammonium salt additive; and

[0433] (C) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol.

[0434] More preferably component (a) is selected from:

[0435] (A) a quaternary ammonium salt additive formed by the reaction of a quaternising agent and the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group; and

[0436] (B) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol.

[0437] Most preferably component (a) is selected from:

[0438] (A) a quaternary ammonium salt additive formed by the reaction of a quaternising agent selected from an ester of a carboxylic acid, an epoxide optionally in combination with an acid and chloroacetic acid or a salt thereof, and the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group; and

[0439] (B) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol.

[0440] The fuel composition provided by the present invention further comprises (b) at least one small, functionalised aromatic compound.

[0441] The fuel composition may comprise one small, functionalised aromatic compound or two or more small, functionalised aromatic compounds.

[0442] References herein to “a” small, functionalised aromatic compound or “the” small functionalised aromatic compound include embodiments in which two or more such compounds are present, unless otherwise stated. Component (b) is different to component (a). Suitably component (a) and component (b) do not form part of the same molecule.

[0443] By small, functionalised aromatic compound we mean to refer to a compound which includes at least one functional group and which is suitably not polymeric.

[0444] The small functionalised aromatic compounds include at least one functional group. By functional group we mean to refer to a substituent which is not a single carbon-carbon bond or a single carbon-hydrogen bond.

[0445] Suitable functional groups include alkenes, alkynes, hydroxy, alkoxy, esters, amides, imides, halo, amino, aldehyde, keto, nitro, nitrile, cyano substituted amino, carboxy, mercapto and sulfonic acid.

[0446] In preferred embodiments the small, aromatic compounds do not comprise any halo or sulfur containing groups.

[0447] Preferred functional groups contain one or more hetero atoms, especially nitrogen and / or oxygen atoms. Preferred functional groups include electron withdrawing groups. Other functional groups may also be present. In some preferred embodiments the small, functionalised aromatic compound includes at least one electron withdrawing group and optionally one or more further functional groups.

[0448] In some preferred embodiments the small, functionalised aromatic compound includes one or more electron withdrawing groups selected from aldehydes, esters, amides, ketones and nitro groups and optionally one or more further functional groups. The one or more further functional groups are preferably hydroxy or hydroxyalkyl.

[0449] Preferably the or each small, functionalised aromatic compound includes less than 5 aromatic rings, preferably less than 4 aromatic rings. Preferably the or each small, functionalised aromatic compound includes one or two aromatic rings.

[0450] In some embodiments the or each small, functionalised aromatic compound includes a single aromatic ring. One or more functional groups may be present within the molecule.

[0451] In such embodiments the single aromatic ring may be entirely carbon based or it may be a heterocyclic aromatic ring. The aromatic ring may suitably comprise 5 to 7 carbon atoms. Preferably the aromatic ring comprises 6 carbon atoms. The aromatic ring may comprise one or more heteroatoms within the aromatic ring. Such heteroatoms are suitably selected from oxygen and / or nitrogen.

[0452] Preferred aromatic rings are based on benzene.

[0453] In some embodiments the small, functionalised aromatic compound is based on a benzene ring including an electron withdrawing group as a substituent and optionally one or more further substituents. Preferably in such embodiments the one or more further substituents are not ortho to the electron withdrawing group.

[0454] In some preferred embodiments component (b) comprises a compound of formula (F): wherein EWG is an electron withdrawing group and each of Ra, Rb, Rc, Rdand Reis independently selected from hydrogen, OH, alkyl, alkoxy, hydroxyalkyl, amino and alkenyl.

[0455] When any of Ra, Rb, Rc, Rdor Reis alkyl, alkenyl or alkoxy, such a group may contain from 1 to 30, preferably 2 to 10 carbon atoms.

[0456] In some embodiments an alkenyl substituent may be a polyisobutenyl group, for example having number average molecular weight of from 200 to 1000, for example around 260.

[0457] Preferred alkyl substituents are Ci to C20 alkyl groups, preferably C4 to C12 alkyl groups. These groups may be straight chain or branched. Preferred are straight chain alkyl groups.

[0458] Preferred alkenyl substituents are Ci to C20 alkenyl groups, preferably C4 to C12 alkenyl groups. These groups may be straight chain or branched. Preferred are straight chain alkenyl groups. Preferred alkoxy substituents are Ci to C20 alkoxy groups, preferably C4 to C12 alkoxy groups. These groups may be straight chain or branched. Preferred are straight chain alkoxy groups. For example R may be CH3(CH2)nO wherein n is from 0 to 20, preferably from 2 to 16, suitably from 6 to 12, for example 8.

[0459] Preferred hydroxyalkyl substituents are of the formula (CHR^yOH wherein y is at least 1 , each Rfis independently hydrogen or Ci to C4 alkyl, preferably methyl. Most preferably each Rfis hydrogen and y is from 1 to 10, preferably from 1 to 6, suitably from 1 to 4, for example 1 or 2.

[0460] Preferably Rais hydrogen.

[0461] Preferably Reis hydrogen.

[0462] Preferably Rais hydrogen and Reis hydrogen.

[0463] Preferably Rbis hydrogen or OH.

[0464] Preferably Rdis hydrogen or OH

[0465] Preferably Rcis hydrogen, NH2, hydroxyalkyl (especially HOCH2) or OH. In some preferred embodiments Rcis OH.

[0466] Preferably EWG is COR12or NO2 wherein R12is hydrogen, alkyl, NR13R14, or OR15wherein each of R13and R14is a hydrogen or an alkyl group and R15is an alkyl group.

[0467] Preferred alkyl groups for R12, R13, R14and R15are Ci to C20 alkyl groups, preferably Ci to C12 or Ci to Cw alkyl groups.

[0468] Preferably R13and R14are hydrogen.

[0469] Preferably R12is hydrogen, Ci to C4 alkyl, NH2 or OR15.

[0470] In some preferred embodiments Rbis hydrogen, Rdis hydrogen and Rcis OH.

[0471] In some embodiments Raand Reare hydrogen; Rcis hydrogen or OH; Rbis hydrogen, NH2, HO(CH2)yor OH; Rdis hydrogen or OH; and EWG is CO2R15, CONHR14, CHO, COR16or NO2wherein y is 1 to 6, preferably 1 or 2; R15is Ci to C20 alkyl, preferably Ci to C12 alkyl, preferably Ci to Cw alkyl; R14is hydrogen or Ci to C12 alkyl, preferably Ci to Cs alkyl, preferably Ci to C4 alkyl; and R16is Ci to Cs alkyl, preferably Ci to C4 alkyl. In some embodiments Raand Reare hydrogen, Rbis hydrogen or OH, Rdis hydrogen or OH, Rcis OH and EWG is CO2R15, CHO or NO2 wherein R15is Ci to C20 alkyl, preferably Ci to C12 alkyl, preferably Ci to Cs alkyl.

[0472] In some embodiments Ra, Rb, Rdand Reare all hydrogen, Rcis OH, NH2 or HOCH2 and EWG is selected from CHO, NO2, CONHR14, CO2R15and COR16wherein R15is Ci to C20 alkyl, suitably Ci to C10 alkyl; R14is Ci to C12 alkyl, preferably Ci to Ce alkyl and R15is Ci to C12 alkyl, preferably Ci to C4 alkyl.

[0473] In some embodiments Ra, Rb, Rdand Reare all hydrogen, Rcis OH and EWG is selected from CHO, NO2, CONH2 and CO2R15wherein R15is Ci to C20 alkyl, suitably Ci to C12 alkyl, preferably Ci to C10 alkyl.

[0474] In some embodiments Raand Reare hydrogen, Rb, Rcand Rdare all OH and EWG is CO2R15wherein R15is Ci to C12 alkyl, suitably Ci to Ce alkyl.

[0475] In some embodiments each of Ra, Rb, Rc, Rdand Reis hydrogen and EWG is CONH2.

[0476] Suitable compounds of formula (F) for use as component (b) include benzamide, 4-hydroxy benzaldehyde, Ci to C10 alkyl esters of 4-hydroxybenzoic acid, Ci to C4 alkyl esters of 3,4,5- (trihydroxy)benzoic acid, 4-nitro phenol, Ci to C4 alkyl esters of 4-aminobenzoic acid, 4- hydroxyacetophenone, Ci to C4 alkyl esters of 4-(hydroxyalkyl)benzoic acid and Ci to Ce alkyl or dialkyl amides of 4-hydroxybenzoic acid.

[0477] In some embodiments the small, functionalised aromatic compound may be a nitrogen containing aromatic compound.

[0478] Any suitable compound which includes at least one aromatic ring and at least one nitrogen atom may be used as component (b).

[0479] Suitable nitrogen containing aromatic compounds include compounds in which one or more nitrogen atoms are within the aromatic ring and compounds in which one or more nitrogen containing groups are substituents of an aromatic ring.

[0480] In preferred embodiments the nitrogen containing aromatic compound comprises an aromatic heterocyclic compound i.e. a compound including a nitrogen atom within the aromatic ring. Preferably the aromatic compound is a bicyclic aromatic heterocyclic compound. The bicyclic aromatic heterocyclic compound suitably includes two aromatic rings, which are preferably fused. The first aromatic ring suitably includes at least one nitrogen atom within the aromatic ring. The second aromatic ring may be entirely carbon based or it may be a heterocyclic aromatic ring. Each aromatic ring may suitably comprise 5 to 7 atoms.

[0481] In some preferred embodiments component (b) comprises a compound of formula (G): wherein m is from 0 to 4, n is 0 or 1 ; each X is CH, N, NH, CR or NR; and each R is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro.

[0482] The bicyclic aromatic ring of the compound of formula (G) may include one or more substituents R. When m is more than one each R may be the same or different.

[0483] When R is alkyl, alkenyl or alkoxy, it may contain from 1 to 30, preferably 2 to 10 carbon atoms. In preferred embodiments m is 0 to 2, preferably 0 or 1 .

[0484] Each X may be N, NH, NR, CH or CR.

[0485] Preferably each X is N, NH or CH.

[0486] The skilled person will appreciate that each X may be N or NH as appropriate to provide an aromatic system.

[0487] Preferably m is 0 or 1 .

[0488] Preferred alkyl substituents are Ci to C20 alkyl groups, preferably C4 to C12 alkyl groups. These groups may be straight chain or branched. Preferred are straight chain alkyl groups.

[0489] Preferred alkenyl substituents are Ci to C20 alkenyl groups, preferably C4 to C12 alkenyl groups. These groups may be straight chain or branched. Preferred are straight chain alkenyl groups. Preferred alkoxy substituents are Ci to C20 alkoxy groups, preferably C4 to C12 alkoxy groups. These groups may be straight chain or branched. Preferred are straight chain alkoxy groups. For example R may be CH3(CH2O)nO wherein n is from 0 to 20, preferably from 2 to 16, suitably from 6 to 12, for example 8.

[0490] In some preferred embodiments R is OH.

[0491] Preferred nitrogen containing aromatic compounds are based on benzotriazole or quinoline. These compounds may be optionally substituted.

[0492] Preferred compounds of formula (G) for use as component (b) include benzotriazole and 8 hydroxyquinoline.

[0493] Other compounds which may be used as component (b) include phthalimide compounds of formula (H): wherein x is from 0 to 4, n is 0 or 1 ; each R’ is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro; and R” is hydrogen, an alkyl group or an alkenyl group.

[0494] The phthalimide moiety of the compound of formula (H) may include one or more substituents R’. When x is more than one each R’ may be the same or different.

[0495] When R” is alkyl or alkenyl or alkoxy, it may contain from 1 to 30, preferably 2 to 10 carbon atoms. Preferably R” is hydrogen.

[0496] In preferred embodiments x is 0 to 2, preferably 0 or 1 .

[0497] Most preferably R” is hydrogen and x is 0.

[0498] Other nitrogen containing aromatic compounds may also be used. Preferably component (b) does not comprise a reaction product of an aromatic polyamine and an acylating agent.

[0499] Preferably component (b) does not comprise a compound including a quaternary ammonium functional group.

[0500] Preferably component (b) does not comprise the product of a Mannich reaction.

[0501] Preferred nitrogen containing aromatic compounds for use herein have a molecular weight of less than 500 gmol-1, for example less than 300 gmol-1, or less than 200 gmol-1, for example less than 180 gmol-1, preferably less than 160 gmol-1.

[0502] In some embodiments the small, functionalised aromatic compound may include a single carboxylic acid functional group.

[0503] Any suitable aromatic compound comprising a single carboxylic acid functional group may be used.

[0504] In some preferred embodiments component (b) comprises a compound including a single aromatic ring and a single COOH group. Other functional groups may also be present within the molecule.

[0505] In such embodiments component (b) may be provided as a free acid or as a salt thereof. Preferred salts are alkali metal salts.

[0506] Preferably component (b) is not provided as an ammonium or a substituted ammonium salt.

[0507] Most preferably component (b) is provided as a free acid.

[0508] The single aromatic ring may be entirely carbon based or it may be a heterocyclic aromatic ring. The aromatic ring may suitably comprise 5 to 7 carbon atoms. Preferably the aromatic ring comprises 6 carbon atoms. The aromatic ring may comprise one or more heteroatoms within the aromatic ring. Such heteroatoms are suitably selected from oxygen and / or nitrogen.

[0509] Preferred aromatic rings are based on benzene or pyridine.

[0510] In some preferred embodiments component (b) comprises a compound of formula (J): wherein m is from 0 to 5; X is C or N; L is a bond or linking group and each R is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro; or two groups R may together form a cyclic moiety.

[0511] The compound of formula (J) includes an aromatic ring which may include one or more substituents R. When m is more than one each R may be the same or different and / or two groups R could together form a cyclic moiety.

[0512] When R is alkyl, alkenyl or alkoxy, it may contain from 1 to 30, preferably 2 to 10 carbon atoms.

[0513] In some embodiments R may be a polyisobutenyl group, for example having number average molecular weight of from 200 to 1300, for example around 260.

[0514] In preferred embodiments m is 0 to 2, preferably 0 or 1. When m is 1 , the substituent R in the compound of formula (IX) is preferably at an ortho or para position relative to the carboxylic acid group COOH.

[0515] X may be N or C.

[0516] When X is N, the heteroatom is preferably at an ortho position relative to the COOH group.

[0517] Preferred alkyl substituents are Ci to C20 alkyl groups, preferably C4 to C12 alkyl groups. These groups may be straight chain or branched. Preferred are straight chain alkyl groups.

[0518] Preferred alkenyl substituents are Ci to C20 alkenyl groups, preferably C4 to C12 alkenyl groups. These groups may be straight chain or branched. Preferred are straight chain alkenyl groups.

[0519] Preferred alkoxy substituents are Ci to C20 alkoxy groups, preferably C4 to C12 alkoxy groups. These groups may be straight chain or branched. Preferred are straight chain alkoxy groups. For example R may be CH3(CH2)nO wherein n is from 0 to 20, preferably from 2 to 16, suitably from 6 to 12, for example 8.

[0520] In some embodiments two groups R together form a cyclic moiety. Such a cyclic moiety may be aliphatic or aromatic and may be optionally substituted.

[0521] In one preferred embodiments two groups R together form a further aromatic 6 membered ring which is fused to the first aromatic ring. In one such embodiment the compound of formula (IX) is 1-napthoic acid:

[0522] Other isomers of napthoic acid isomers are also within the scope of the invention.

[0523] L is a bond or a linking group.

[0524] In some embodiments L is a bond and the carboxylic acid group is directly bonded to the aromatic ring.

[0525] In some embodiments L is an optionally substituted alkylene or alkenylene group.

[0526] For example L may be (CH2)ywherein y is from 1 to 12, preferably from 1 to 6, suitably from 1 to 4. Preferred compounds of this type include phenyl acetic acid and phenyl butyric acid.

[0527] When L is an alkenylene group, the alkene moiety may be cis or trans. One preferred compound of this type is trans-cinnamic acid.

[0528] Suitable compounds of formula (J) for use as component (b) include benzoic acid, salicylic acid, 2-picolinic acid, nicotinic acid, 4-nonyloxy benzoic acid, phenyl acetic acid, phenyl butyric acid, 1-napthoic acid and trans-cinnamic acid.

[0529] Preferably component (b) is selected from one or more of: - a small, functionalised aromatic compound including one or more electron withdrawing groups selected from aldehydes, esters, amides and nitro groups and optionally one or more further functional groups;

[0530] - a nitrogen containing aromatic compound; and

[0531] - an aromatic compound including a single carboxylic acid functional group.

[0532] Preferably component (b) is selected from one or more of:

[0533] - a compound of formula (F);

[0534] - a compound of formula (G);

[0535] - a compound of formula (H); and

[0536] - a compound of formula (J).

[0537] Preferably component (b) is selected from benzamide, 4-hydroxy benzaldehyde, Ci to C10 alkyl esters of 4-hydroxybenzoic acid, Ci to C4 alkyl esters of 3,4,5-(trihydroxy)benzoic acid, 4-nitro phenol, Ci to C4 alkyl esters of 4-aminobenzoic acid, 4-hydroxyacetophenone, Ci to C4 alkyl esters of 4-(hydroxyalkyl)benzoic acid and Ci to Ce alkyl or dialkyl amides of 4-hydroxybenzoic acid, phthalimide, benzotriazole, 8-hydroxyquinoline, benzoic acid, salicylic acid, 2-picolinic acid, nicotinic acid, 4-nonyloxy benzoic acid, phenyl acetic acid, phenyl butyric acid, 1-napthoic acid, trans-cinnamic acid and mixtures thereof.

[0538] Component (a) is preferably present in the fuel composition in an amount of at least 1 ppm, preferably at least 10 ppm, more preferably at least 20 ppm, preferably at least 50 ppm, for example at least 70 ppm.

[0539] Component (a) may be present in the fuel composition in an amount of up to 5000 ppm, preferably up to 1000 ppm, more preferably up to 500 ppm, suitably up to 250 ppm, for example up to 150 ppm.

[0540] Component (a) is preferably present in the fuel composition in an amount from 5 to 300 ppm, preferably from 10 to 200 ppm, more preferably from 50 to 150 ppm.

[0541] Component (b) is preferably present in the fuel composition in an amount of at least 1 ppm, preferably at least 3 ppm, more preferably at least 5 ppm, preferably at least 10 ppm, for example at least 15 ppm.

[0542] Component (b) is preferably present in the fuel composition in an amount of up to 1000 ppm, preferably up to 200 ppm, more preferably up to 100 ppm, suitably up to 60 ppm, preferably up to 49 ppm, for example up to 40 ppm. Component (b) is preferably present in the fuel composition in an amount of less than 50 ppm.

[0543] Component (b) is preferably present in the fuel composition in an amount from 1 to 100 ppm, preferably from 5 to 50 ppm, more preferably from 10 to 40 ppm.

[0544] The weight ratio of component (a) to component (b) in the fuel composition is preferably from 100:1 to 1 :10, preferably from 10:1 to 1 :1 , more preferably from 6:1 to 2:1 .

[0545] Component (a) may comprise a mixture of compounds.

[0546] Component (b) may comprise a mixture of compounds.

[0547] For the avoidance of doubt in embodiments in which components (a) and / or (b) comprise a mixture of compounds the above amounts refer to the total amount of all such compounds present in the composition.

[0548] In some embodiments the present invention provides a diesel fuel composition comprising at least 50 ppm of component (a) and less than 50 ppm of component (b), for example from 60 to 200 ppm of component (a) and from 1 to 45 ppm of component (b).

[0549] The fourth aspect of the present invention relates to a method of preparing a diesel fuel composition by the addition of component (a) and component (b) to a diesel fuel.

[0550] Preferably component (a) and component (b) are provided as separate entities. They may be admixed prior to addition to the fuel, for example they may be provided as part of an additive composition.

[0551] In some embodiments the fourth aspect of the present invention may involve the addition to a diesel fuel composition of an additive combination comprising a mixture of (a) at least one nitrogen containing detergent; and (b) at least one small, functionalised aromatic compound.

[0552] The additive combination may suitably be provided as part of an additive composition further comprising a diluent or carrier and optionally one or more further additives.

[0553] The fuel composition provided by the present invention may further comprise one or more additional fuel additives. These may include dispersants, detergents, metal deactivating compounds, wax anti-settling agents, cold flow improvers, cetane improvers, dehazers, stabilisers, demulsifiers, antifoams, corrosion inhibitors, dyes, markers, combustion improvers, metal deactivators, odour masks, drag reducers and conductivity improvers. The fuel composition provided by the present invention has advantageous lubricity properties. Lubricity of a fuel may be measured according to the HFRR test. This is a standard test method that is known to the person skilled in the art and is described, for example, in ISO 12156-1 :2023.

[0554] Preferably the fuel composition provided by the present invention has a wear scar diameter as measured in the HFRR test of less than 420 pm, preferably less than 400 pm.

[0555] The addition of additives (a) and (b) enhances the lubricity properties of the fuel.

[0556] The method and use of the first and second aspects of the present invention involve the use of a combination of additives to improve the lubricity of a diesel fuel. Suitably the additive combination of additives (a) and (b) reduces the wear scar of a diesel fuel by at least 50 pm, preferably at least 70 pm, for example at least 100 pm compared with the wear scar of the base fuel without additive (a) or additive (b). The wear scar is suitably measured according to the HFRR test.

[0557] Preferably the method and use of the first and second aspect of the present invention reduce the wear scar by an amount greater than the sum of the reduction in wear scar when using each of additives (a) and (b) alone.

[0558] In another embodiment the present invention may involve improving the lubricity of a fuel composition which already contains a nitrogen containing detergent.

[0559] According to a fifth aspect of the present invention there is provided a method of improving the lubricity of a diesel fuel composition comprising (a) at least one nitrogen containing detergent; the method comprising adding to the diesel fuel composition (b) at least one small, functionalised aromatic compound.

[0560] According to a sixth aspect of the present invention there is provided the use of (b) at least one small, functionalised aromatic compound to improve the lubricity of a diesel fuel composition comprising (a) at least one nitrogen containing detergent.

[0561] Preferred features of the fifth and sixth aspects of the present invention are suitably as defined in relation to the first, second, third and fourth aspects. In the fifth and sixth aspects of the present invention, the diesel fuel, the nitrogen containing detergent and the small functionalised aromatic compounds are preferably as defined in relation to the first, second and third aspects.

[0562] Preferably the method and use of the fifth and sixth aspects reduce the wear scar of a diesel fuel composition comprising (a) at least one nitrogen containing detergent by at least 30 pm, preferably at least 60 pm, more preferably at least 80 pm.

[0563] The use of the sixth aspect may also reduce the treat rate of nitrogen containing detergent needed to achieve an equivalent lubricating performance compared with when the at least one small, functionalised aromatic compound is not present.

[0564] The invention will now be further described with reference to the following non-limiting examples.

[0565] Example 1

[0566] Additive A, a quaternary ammonium salt additive, was prepared as follows:

[0567] 700 g (0.7 mol) of polyisobutylene (Mn1000) 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.

[0568] This material was then 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 solvent to provide an overall solids content of 60 wt% prior to discharging from the reactor.

[0569] Example 2 Additive B, a Mannich reaction product additive, was prepared as follows:

[0570] A 1 L reactor was charged with dodecylphenol (170.6g, 0.65 mol), ethylenediamine (30.1 g, 0.5 and Caromax 20 (123.9g). The mixture was heated to 95 °C and formaldehyde solution, 37 wt% (73.8g, 0.9 mol) charged over 1 hour. The temperature was increased to 125 °C for 3 hours and water removed. In this example the molar ratio of aldehyde (a) : amine (b) : phenol (c) was approximately 1 .8:1 :1.3.

[0571] Example 3

[0572] Fuel compositions were prepared by adding 8-hydroxyquinoline and / or nitrogen containing detergents A and B to a hydrotreated vegetable oil (HVO) fuel, as detailed in table 1 .

[0573] The HVO fuel complied with the specification set out in EN15940 (2023). The cloud point of the fuel was - 23°C (measured according to IP 219) and the pour point was -38°C (measured according to IP 15).

[0574] Table 1

[0575] Example 4

[0576] The example fuel compositions of example 3 were tested according to the standard HFRR procedure set out in ISO 12156-1 :2023 (modified to 70 minutes run time rather than 75 minutes) as follows:

[0577] A steel ball is in contact with a steel disc with a normal load of 200 g. The contact is submerged in 2 ml of the test fuel composition and then heated to 60 °C. The ball slides in a reciprocating sliding motion over a length of 1 mm at a rate of 50 Hz. The ball is taken off after 70 mins and the wear scar is measured.

[0578] The results are given in Table 2:

[0579] Table 2

[0580] Example 5

[0581] Diesel fuel compositions were prepared by adding the components listed in table 3 into a hydrotreated vegetable oil (HVO) fuel having the properties described in example 1 . The wear scar of the resultant compositions was determined using the HFRR test method described in example 2.

[0582] Additive C is a polyisobutenyl succinimide obtained from the condensation reaction of a polyisobutenyl succinic anhydride derived from polyisobutene of Mn approximately 750 with a polyethylene polyamine mixture of average composition approximating to tetraethylene pentaamine.

[0583] Table 3

[0584] Example 6

[0585] Diesel fuel compositions were prepared by adding the components listed in table 4 into an EN590 compliant BO base fuel. The wear scar of the resultant compositions was determined using the HFRR test method described in example 2.

[0586] Table 4

Claims

Claims1. A method of improving the lubricity of a diesel fuel composition, the method comprising admixing into the composition: (a) at least one nitrogen containing detergent; and (b) at least one small, functionalised aromatic compound.

2. The use of the combination of: (a) at least one nitrogen containing detergent and (b) at least one small, functionalised aromatic compound to improve the lubricity of a diesel fuel composition.

3. A diesel fuel composition comprising a major proportion of a diesel fuel and:(a) at least one nitrogen containing detergent; and(b) at least one small, functionalised aromatic compound.

4. A method of preparing a diesel fuel composition comprising admixing diesel fuel with:(a) at least one nitrogen containing detergent; and(b) at least one small, functionalised aromatic compound.

5. A method of improving the lubricity of a diesel fuel composition comprising (a) at least one nitrogen containing detergent; the method comprising adding to the fuel composition (b) at least one small, functionalised aromatic compound.

6. The use of (b) at least one small, functionalised aromatic compound to improve the lubricity of a diesel fuel composition comprising (a) at least one nitrogen containing detergent.

7. A composition, method or use according to any preceding claim wherein the diesel fuel is selected from mineral diesel, biodiesel, renewable diesel and blends thereof.

8. A composition, method or use according to any preceding claim wherein the diesel fuel comprises a paraffinic fuel.

9. A composition, method or use according to claim 8 wherein the paraffinic fuel provides at least 90 vol%, preferably at least 99 vol% of all fuel present in the fuel composition.

10. A composition, method or use according to any preceding claim wherein component (a) is selected from one or more of:(A) a quaternary ammonium salt additive;(B) the reaction product of a carboxylic acid-derived acylating agent and an amine;(C) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol;(D) the reaction product of a carboxylic acid-derived acylating agent and hydrazine;(E) a salt formed by the reaction of a carboxylic acid with a C1 to C10 alkyl amine such as di-n-butylamine or tri-n-butylamine;(F) 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; and(G) a compound of formula (I):A— L— R1(I) wherein:A is a nitrogen-containing group;L is either a bond or a linker group; andR1is an optionally substituted hydrocarbyl group; and wherein the compound has a nitrogen content of at least 4% by mass.

11. A composition, method or use according to claim 10 wherein component (a) comprises (A) a quaternary ammonium salt additive; and / or (B) the product of a Mannich reaction between an aldehyde, an amine and an optionally substituted phenol;12. A composition, method or use according to claim 10 or claim 11 wherein component (a) comprises a quaternary ammonium salt which is the reaction product of a quaternising agent and a nitrogen-containing species having at least one tertiary amine group selected from:(i) the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group;(ii) a Mannich reaction product comprising a tertiary amine group;(iii) a polyalkylene substituted amine having at least one tertiary amine group;(iv) a tertiary amine of formula R5R6R7N, wherein each of R5, R6and R7is independently an optionally substituted alkyl, alkenyl, aryl, alkaryl or aralkyl group;(v) a cyclic tertiary amine; and(vi) a polyetheramine compound.

13. A composition, method or use according to claim 12 wherein nitrogen-containing species having at least one tertiary amine group is (i) the reaction product of a hydrocarbyl-substituted acylating agent and a compound having at least one tertiary amine group and a primary amine, secondary amine or alcohol group.

14. A composition, method or use according to claim 13 wherein the hydrocarbyl substituted acylating agent is a hydrocarbyl substituted succinic acid or a hydrocarbyl substituted succinic anhydride.

15. A composition, method or use according to claim 13 wherein hydrocarbyl substituted acylating agent is a fatty acid.

16. A composition, method or use according to any of claims 13 to 15 wherein the hydrocarbyl substituted acylating agent is reacted with an amine of formula (B1) or (B2):R2R\N - X - NHR4N - X - [O(CR42)m]nOHR3R3(B1)wherein R2and R3are the same or different alkyl groups having from 1 to 36 carbon atoms; X is an alkylene group having from 1 to 20 carbon atoms; n is from 0 to 20; m is from 1 to 5; and R4is hydrogen or a Ci to C36 alkyl group.

17. A composition, method or use according to claim 16 wherein the compound of formula(B1) or (B2) is selected from from N,N-dimethyl-1 ,3-diaminopropane, N, N-d iethy 1-1 ,3-diaminopropane, N,N-dimethylethylenediamine, N,N-diethylethylenediamine, N,N- dibutylethylenediamine, dimethylaminopropanol, N,N-dimethyl-1 ,3-diaminopropane (dimethylaminopropylamine) or combinations thereof.

18. A composition, method or use according to any of claims 12 to 17 wherein the quaternising agent is selected from an ester of a carboxylic acid, an epoxide optionally in combination with an acid and chloroacetic acid or a salt thereof.

19. A composition, method or use according to claim 11 wherein component (a) comprises the Mannich reaction product of formaldehyde, a polyethylene polyamine; and a parasubstituted monoalkyl phenol, preferably having an alkyl substituent having 4 to 28 carbon atoms, especially 10 to 14 carbon atoms.

20. A composition, method or use according to any preceding claim wherein component (b) comprises a small, functionalised aromatic compound including one or more electron withdrawing groups selected from aldehydes, esters, amides and nitro groups and optionally one or more further functional groups.

21. A composition, method or use according to any preceding claim wherein component (b) comprises a compound of formula (F):wherein EWG is an electron withdrawing group and each of Ra, Rb, Rc, Rdand Reis independently selected from hydrogen, OH, alkyl, alkoxy, hydroxyalkyl, amino and alkenyl.

22. A composition, method or use according to claim 21 wherein Raand Reare hydrogen; Rcis hydrogen or OH; Rbis hydrogen, NH2, HO(CH2)yor OH; Rdis hydrogen or OH; and EWG is CO2R15, CONHR14, CHO, COR16or NO2wherein y is 1 to 6; R15is Ci to C20 alkyl; R14is hydrogen or Ci to C12 alkyl; and R16is Ci to Cs alkyl.

23. A composition, method or use according to any preceding claim wherein component (b) comprises a bicyclic heteroaromatic compound.

24. A composition, method or use according to any preceding claim wherein component (b) comprises a compound of formula (G):wherein m is from 0 to 4, n is 0 or 1 ; each X is CH, N, NH, CR or NR; and each R is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro.

25. A composition, method or use according to any preceding claim wherein component (b) comprises a compound of formula (H):wherein x is from 0 to 4, n is 0 or 1 ; each R’ is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro; and R” is hydrogen, an alkyl group or an alkenyl group.

26. A composition, method or use according to any preceding claim wherein component (b) comprises a compound including a single aromatic ring and a single COOH group.

27. A composition, method or use according to any preceding claim wherein component (b) comprises a compound of formula (J):wherein m is from 0 to 5; X is C or N; L is a bond or linking group and each R is independently selected from OH, alkyl, alkoxy, amino, alkenyl and nitro; or two groups R may together form a cyclic moiety.

28. A composition, method or use according to any preceding claim wherein component (b) is selected from benzamide, 4-hydroxy benzaldehyde, Ci to C10 alkyl esters of 4- hydroxybenzoic acid, Ci to C4 alkyl esters of 3,4,5-(trihydroxy)benzoic acid, 4-nitro phenol, Ci to C4 alkyl esters of 4-aminobenzoic acid, 4-hydroxyacetophenone, Ci to C4 alkyl esters of 4-(hydroxyalkyl)benzoic acid and Ci to Ce alkyl or dialkyl amides of 4- hydroxybenzoic acid, phthalimide, benzotriazole, 8-hydroxyquinoline, benzoic acid, salicylic acid, 2-picolinic acid, nicotinic acid, 4-nonyloxy benzoic acid, phenyl acetic acid, phenyl butyric acid, 1-napthoic acid, trans-cinnamic acid and mixtures thereof.

29. A composition, method or use according to any preceding claim wherein the weight ratio of component (a) to component (b) in the fuel composition is from 10:1 to 1 :1.

30. A composition, method or use according to any preceding claim wherein component (a) is present in the fuel composition in an amount of from 5 to 300 ppm and component (b) is present in the fuel composition in an amount of from 1 to 100 ppm.

31. A composition, method or use according to any of claims 1 to 4 or 7 to 30 wherein the fuel composition comprising additive (a) and additive (b) has a wear scar at least 70pm lower than the wear scar of the same fuel composition without additive (a) and additive (b).

32. A method or use according to any of claims 5 to 30 wherein the addition of additive (b) reduces the wear scar by at least 50pm.

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