Use of a fuel composition comprising three additives for cleaning the internal parts of petrol engines

Abstract

The present invention relates to the use, for reducing deposits in the internal parts of a spark ignition engine, of a fuel composition comprising at least three additives: a quaternary ammonium salt, a non-quaternary polyisobutylene succinimide and a Mannich base which is different from the other additives. The composition is such that the mass ratio of the quantity of the first additive to the quantity of the second additive is in the range from 0.2: 1 to 2.5: 1.

Description

[0001] The present invention relates to the use, for reducing and / or preventing deposits present in the internal parts of a spark-ignition engine, of a fuel composition which comprises at least three additives: a quaternary ammonium salt, a non-quaternary polyisobutylene succinimide, and a Mannich base, different from the other two additives. The composition is such that the mass ratio of the quantity of the first additive to the quantity of the second additive is in the range from 0.2:1 to 2.5:1.

[0002] The invention also relates to the use, for improving the detergency properties of a gasoline fuel, of a fuel concentrate comprising at least said three additives, mixed with an organic liquid inert with respect to said additives.

[0003] The composition is also used to maintain cleanliness (keep-clean effect) and / or clean (clean-up effect) deposits in the engine, as well as to reduce the fuel consumption of the engine (“Fuel Eco” action) and / or minimize the loss of power of said engine, and / or reduce pollutant emissions, in particular, particulate emissions from the combustion engine, and / or to reduce the fouling of the pistons of the engine, preferably in gasoline direct injection (or IDE). STATE OF THE PRIOR ART

[0004] Liquid fuels for internal combustion engines contain components that can degrade during engine operation. The problem of deposits in the internal parts of combustion engines is well known to engine manufacturers. The formation of these deposits has been shown to have consequences for engine performance, particularly negative impacts on fuel consumption and particulate emissions (Gueit, J. et al., "Injector Fouling in Direct Injection Spark Ignition Engines - A New Test Procedure for the Evaluation of Gasoline Additives," SAE Technical Paper 2017-01-2294). Advances in fuel additive technology have made it possible to address this problem.So-called detergent additives used in fuels have already been proposed to maintain engine cleanliness by limiting deposits (the "keep-clean" effect) or by reducing deposits already present in the internal parts of the combustion engine (the "clean-up" effect). An example of this is document US4171959, which describes a detergent additive for gasoline fuel containing a quaternary ammonium function.

[0005] However, engine technology is constantly evolving and fuel requirements must evolve to accommodate these technological advances in combustion engines.

[0006] In particular, new gasoline direct injection systems expose the injectors to more severe pressure and temperature conditions, which promote the formation of deposits.

[0007] In addition, these new injection systems feature more complex geometries to optimize spraying, including more holes with smaller diameters, but which, on the other hand, induce greater sensitivity to deposits. The presence of deposits can impair combustion performance, particularly increasing pollutant and particulate emissions.

[0008] Other consequences of excessive deposits have been reported in the literature, such as increased fuel consumption, and therefore particulate emissions, and driveability issues.

[0009] Preventing and reducing deposits in these new engines is essential for the optimal operation of today's engines. There is therefore a need to offer detergent fuel additives that promote optimal operation of combustion engines, particularly for new engine technologies but also for older / conventional engine technologies.

[0010] In the case of spark-ignition engines (or petrol engines) with indirect injection, a particular problem arises, linked to the formation of deposits on the external parts of the engine and in particular on the stems of the intake valves of the air and fuel mixture upstream of the combustion chamber, which results in a phenomenon of valve sticking.

[0011] This phenomenon, well known to specialists under the English term "valve sticking", is described in a reference publication by Seppo Mikkonen, Reino Karlsson and Jouni Kivi entitled "Intake Valve Stiking in Some Carburetor Engines", SAE Technical Paper Series n°881643, International Fuels and Lubricants Meeting and Exposition, Portland, Oregon, October 10-13, 1988.

[0012] This phenomenon is caused, during engine operation at low temperatures (in cold weather for example), by a build-up of deposits with high viscosity at the interface between the inlet valve stem and the valve guide, in indirect injection spark ignition engines. The accumulation of such deposits on the valve stems hinders the valve movements, the stems stick to the valve guides, which causes poor valve closing, leads to sealing problems in the combustion chamber, and can significantly affect the operation of the engine, and in particular can prevent it from starting in cold weather.

[0013] Generally speaking, there are different types of deposits on the intake valves of indirect injection spark ignition engines. These types of deposits are well known to engine manufacturers, and the appearance of some depends on the treatment solutions for others.

[0014] On the one hand, a first type of deposit consists of those which form at high temperature on the intake valves of indirect injection spark ignition engines when using a fuel not containing a detergent additive. These deposits consist in particular of carbon residues linked to the coking phenomenon and can also include soap and / or lacquer type deposits (in English "lacquering"). These deposits are generally treated by the use of detergent additive added to the fuel (additive fuel).

[0015] On the other hand, a second type of deposit consists of the viscous deposits, mentioned above, which form at low temperature and appear on the intake valves of indirect injection spark ignition engines when using additive fuels, thus causing the valve sticking phenomenon described above.

[0016] Thus, fuel additives for the treatment and prevention of deposits that form at high temperatures can cause the appearance of viscous deposits at low temperatures.

[0017] As explained in the aforementioned publication (SAE Technical Paper Series No. 881643), the composition of gasoline and the additives it contains have a very significant influence on valve sticking phenomena. In particular, the detergent additives conventionally incorporated into gasolines to keep the valves clean have paradoxically been found to promote valve sticking phenomena. As is known per se, the problem of valve sticking does not occur or occurs very little when using a fuel without detergent additives. In addition, the aforementioned publication shows that polymeric additives, which may be used in gasolines and / or engine oils, are known to be agents that promote valve sticking.

[0018] WO2006135881 describes a detergent additive containing a quaternary ammonium salt used to reduce or clean deposits particularly on intake valves.

[0019] WO 2015 / 183908 describes an additive for fuel or lubricant compositions, consisting of a hydrocarbyl-substituted imide quaternary ammonium salt having an average molecular weight in the range of 300 to 750.

[0020] The examples illustrate the synthesis of different low molecular weight quaternary ammonium salts of polyisobutylene succinimides and their detergency performance in fuels intended for diesel engines (tests XUD9 and DW10B) not in spark ignition or gasoline engines.

[0021] The solutions proposed in the prior art are not entirely satisfactory. There is therefore a need to propose fuel additives that promote optimal operation of spark-ignition engines and that are effective in preventing all types of deposits, including on intake valves.

[0022] There is also a need for a universal detergent additive capable of acting on deposits regardless of engine technology (direct or indirect injection) and / or fuel properties, while minimizing the treatment rate, i.e. the quantities of additive(s) used. SUBJECT OF THE INVENTION

[0023] The applicant has discovered that the use of a fuel composition comprising at least three additives, as described below, has remarkable and unexpected detergent properties for internal combustion engines, preferably gasoline, known as spark-ignition engines. This combination of additives makes it possible to guarantee and improve the detergent power of fuels intended for internal combustion engines. It also produces an unexpected synergistic effect.

[0024] Additional advantages of the fuel additive composition used according to the invention are: protection of pumps, injection systems, piston area, rings, liners and all moving parts with which this additive comes into contact in an engine, optimal engine operation, reduced fuel consumption, savings due to less engine maintenance and lower consumption, reduced particulate emissions, efficiency in direct injection and indirect gasoline injection.

[0025] The present invention thus relates to the use, for reducing and / or preventing deposits in the internal parts of a spark-ignition engine, of a fuel composition comprising: (1) at least one first additive consisting of a quaternary ammonium salt obtained by reaction with a quaternization agent of a nitrogen compound comprising a tertiary amine function, this compound being the product of the reaction of a polyisobutenyl succinic anhydride and a compound comprising at least one tertiary amine group chosen from the amines of the following formula (I): in which R6 and R7 are the same or different and represent, independently of each other, an alkyl group having from 1 to 5 carbon atoms; X is an alkylene group having from 1 to 5 carbon atoms; and R8 is a hydrogen atom, (2) at least one second additive consisting of a non-quaternary polyisobutylene succinimide, (3) at least one third additive, different from additives (1) and (2), consisting of a Mannich base, and in which the mass ratio of the quantity of the first additive to the quantity of the second additive is in the range from 0.2:1 to 2.5:1.

[0026] Preferably, the mass ratio of the amount of the first additive to the amount of the second additive in the composition is in the range from 1:1 to 2:1, and preferably from 1.25:1 to 1.5:1.

[0027] The invention also relates to the use of the composition, for maintaining cleanliness (keep-clean effect) and / or cleaning (clean-up effect) deposits in the internal parts of a spark-ignition engine, chosen from the following: the combustion chamber and the fuel injection system, and preferably the fuel injection system.

[0028] The invention also relates to the use, for improving the detergency properties of a gasoline fuel, of a fuel concentrate comprising at least the three additives above, mixed with an organic liquid, said organic liquid being inert with respect to the first, second and third additives, and miscible with said fuel.

[0029] The invention also relates to a method for maintaining the cleanliness and / or cleaning at least one of the internal parts of a spark-ignition engine (or internal combustion gasoline engine), comprising at least the following steps: the preparation of a fuel composition by adding at least the three additives defined above to a fuel, or a concentrate comprising them, then the combustion of said fuel composition in said spark-ignition engine.

[0030] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the following description.

[0031] In the following, and unless otherwise indicated, the limits of a domain of values are included in this domain, in particular in the expressions "between" and "ranging / goes / extends from ... to ...".

[0032] Furthermore, the expressions "at least one" and "at least" used in this description are respectively equivalent to the expressions "one or more" and "greater than or equal".

[0033] Finally, in a manner known per se, a CN compound or group is a compound or group containing N carbon atoms in its chemical structure. DETAILED DESCRIPTION The first additive: quaternary ammonium

[0034] The composition according to the invention comprises a first additive consisting of a quaternary ammonium salt, obtained by reaction with a quaternization agent of a nitrogen compound comprising a tertiary amine function, this nitrogen compound being the product of the reaction of an acylating agent substituted by a hydrocarbon group and of a compound comprising at least one tertiary amine group chosen from the amines of formula (I).

[0035] The acylating agent is succinic anhydride.

[0036] According to the invention, the hydrocarbon substituent of the acylating agent is a polyisobutene group also called polyisobutylene (PIB). Particularly preferred are so-called highly reactive polyisobutenes (PIB). Highly reactive polyisobutenes (PIB) are understood to mean polyisobutenes (PIB) in which at least 50 mol%, preferably at least 70 mol% or more, of the terminal olefinic double bonds are of the vinylidene type as described in document EP0565285. In particular, preferred PIBs are those having more than 80 mol% and up to 100 mol% of vinylidene terminal groups as described in document EP1344785.

[0037] According to the invention, the acylating agent substituted by a hydrocarbon group is a polyisobutenyl succinic anhydride (PIBSA).

[0038] The preparation of polyisobutenyl succinic anhydrides is known per se and is widely described in the literature. Examples include the processes comprising the reaction between polyisobutenes (PIB) and maleic anhydride described in US3361673 and US3018250 or the process comprising the reaction of a halogenated, in particular chlorinated, polyisobutene (PIB) with maleic anhydride (US3172892).

[0039] Alternatively, polyisobutenyl succinic anhydride can be prepared by blending a polyolefin with maleic anhydride and then passing chlorine through the blend (GB949981).

[0040] The compound of formula (I) may, for example, be chosen from the group consisting of: dimethylaminopropylamine, N,N-diethylaminopropylamine, N,N-dimethylaminoethylamine, and preferably N,N-dimethylaminopropylamine.

[0041] According to a preferred embodiment: R6 and R7 represent, independently of one another, a methyl, ethyl, propyl, butyl, pentyl group, or their isomers, preferably a methyl group; X represents an alkylene group having from 2 to 5 carbon atoms. X particularly preferably represents an ethylene, propylene or butylene group, in particular a propylene group.

[0042] According to the invention, the nitrogen compound is the reaction product of a polyisobutenyl succinic anhydride and a compound of formula (I).

[0043] Polyisobutenyl succinic anhydride reacts with amine also comprising a tertiary amine group under certain conditions to form a succinimide (closed form). The reaction of the succinic acid derivative and the amine can also result under certain conditions in a succinamide, i.e., a compound comprising an amide group and a carboxylic acid group (open form).

[0044] The quaternary ammonium salt forming the first additive according to the present invention is directly obtained by reaction between the nitrogen compound described above comprising a tertiary amine function and a quaternization agent.

[0045] According to a particular embodiment, the quaternizing agent is chosen from the group consisting of dialkyl sulfates, carboxylic acid esters, alkyl halides, benzyl halides, hydrocarbon carbonates, and hydrocarbon epoxides optionally mixed with an acid, alone or as a mixture, preferably carboxylic acid esters.

[0046] In fuel compositions, it is often desirable to reduce the content of halogen, sulfur and phosphorus-containing compounds.

[0047] Thus, if a quaternizing 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 can then be reacted with sodium hydroxide and the sodium halide salt removed by filtration.

[0048] The quaternizing agent may comprise halides such as chloride, iodide or bromide; hydroxides; sulfonates; bisulfites; alkyl sulfates such as dimethyl sulfate; sulfones; phosphates; C1-C12 alkylphosphates; C1-C12 dialkylphosphates; borates; C1-C12 alkylborates; nitrites; nitrates; carbonates; bicarbonates; alkanoates; C1-C12 O,O-dialkyldithiophosphates, alone or in mixture.

[0049] According to a particular embodiment, the quaternizing agent may be chosen from derivatives of dialkyl sulfates such as dimethyl sulfate, of N-oxides, of sulfones such as propane- and butane-sulfone, of alkyl, acyl or aralkyl halides such as methyl and ethyl chloride, bromide, iodide or benzyl chloride, and hydrocarbon carbonates (or alkyl carbonates).

[0050] If the acyl halide is benzyl chloride, the aromatic ring is optionally substituted by one or more alkyl or alkenyl groups.

[0051] The hydrocarbon (alkyl) groups of the hydrocarbon carbonates may contain from 1 to 50, from 1 to 20, from 1 to 10 or 1 to 5 carbon atoms per group. According to one embodiment, the hydrocarbon carbonates contain two hydrocarbon groups which may be identical or different. Examples of hydrocarbon carbonates include dimethyl or diethyl carbonate.

[0052] According to a preferred embodiment, the quaternizing agent is chosen from hydrocarbon epoxides represented by the following formula (III): in which R9, R10, R11 and R12 may be the same or different and independently of one another represent a hydrogen atom or a C 1 to C 50 hydrocarbon group. By way of non-limiting example, mention may be made of styrene oxide, ethylene oxide, propylene oxide, butylene oxide, stilbene oxide and C 1 to C 50 epoxides. Styrene oxide and propylene oxide are particularly preferred, and even better the quaternizing agent is propylene oxide.

[0053] Such hydrocarbon epoxides can be used as a quaternizing agent in combination with an acid, for example with acetic acid. Hydrocarbon epoxides can also be used alone as a quaternizing agent, especially without additional acid.

[0054] Without being bound by this hypothesis, it would appear that the presence of the carboxylic acid function in the molecule promotes the formation of the quaternary ammonium salt. In such an embodiment not using an additional acid, a protic solvent is used for the preparation of the quaternary ammonium salt. For example, protic solvents such as water, alcohols (including polyhydric alcohols) can be used alone or in mixtures. Preferred protic solvents have a dielectric constant greater than 9.

[0055] Corresponding quaternary ammonium salts prepared from amides or esters and succinic acid derivatives are described in WO2010 / 132259 or in EP1896555.

[0056] According to another embodiment, the quaternizing agent is chosen from the compounds of formula (IV): wherein R13 is an optionally substituted alkyl, alkenyl, aryl or aralkyl group, and R14 is a C1-C22 alkyl, aryl or alkylaryl group.

[0057] The compound of formula (IV) is a carboxylic acid ester capable of reacting with a tertiary amine to form a quaternary ammonium salt. Compounds of formula (IV) are selected, for example, from carboxylic acid esters having a pKa of 3.5 or less. The compound of formula (IV) is preferably selected from substituted aromatic carboxylic acid, alpha-hydroxycarboxylic acid and polycarboxylic acid esters.

[0058] According to one embodiment, the ester is a substituted aromatic carboxylic acid ester of formula (IV) in which R13 is a substituted aryl group. Preferably, R13 is a substituted aryl group having 6 to 10 carbon atoms, preferably a phenyl or naphthyl group, more preferably a phenyl group. R13 is advantageously substituted by one or more groups chosen from carboalkoxy, nitro, cyano, hydroxy, SR 15 and NR 15 R 16 radicals. Each of the groups R 15 and R 16 may be a hydrogen atom or an optionally substituted alkyl, alkenyl, aryl or carboalkoxy group.Each of the groups R 15 and R 16 advantageously represents a hydrogen atom or an optionally substituted C1 to C22 alkyl group, preferably a hydrogen atom or a C1 to C16 alkyl group, more preferably a hydrogen atom or a C1 to C10 alkyl group, even more preferably a hydrogen atom or a C1 to C4 alkyl group. R 15 is preferably a hydrogen atom and R 16 a hydrogen atom or a C1 to C4 group. Advantageously, R 15 and R 16 are both a hydrogen atom.

[0059] According to one embodiment, R13 is an aryl group substituted by one or more groups chosen from hydroxyl, carboalkoxy, nitro, cyano and NH 2 radicals. R13 may be a polysubstituted aryl group, for example trihydroxyphenyl. Advantageously, R13 is a monosubstituted aryl group, preferably substituted in ortho. R13 is, for example, substituted by a group chosen from OH, NH 2 , NO 2 or COOMe radicals, preferably OH or NH 2 . R13 is, preferably, a hydroxy-aryl group, in particular 2-hydroxyphenyl.

[0060] According to a particular embodiment, R14 is an alkyl or alkylaryl group. R14 may be a C1 to C16, preferably C1 to C10, advantageously C1 to C8 alkyl group. R14 may be a C1 to C16, preferably C1 to C10, advantageously C1 to C8 alkylaryl group. R14 may for example be chosen from methyl, ethyl, propyl, butyl, pentyl, benzyl groups or their isomers. Preferably, R14 is a benzyl or methyl group, more preferably methyl.

[0061] A particularly preferred compound is methyl salicylate.

[0062] According to a particular embodiment, the compound of formula (IV) is an ester of an alpha-hydroxycarboxylic acid corresponding to the following formula (V): wherein R17 and R18 are the same or different and are independently selected from the group consisting of hydrogen, alkyl, alkenyl, aryl or aralkyl groups. Such compounds are for example described in document EP 1254889.

[0063] Examples of compounds of formula (IV) in which R13COO is the residue of an alpha-hydroxycarboxylic acid include methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, phenyl-, benzyl- or allyl-esters of 2-hydroxyisobutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl- or allyl-esters of 2-hydroxy-2-methylbutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl- or allyl-esters of 2-hydroxy-2-ethylbutyric acid; methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, benzyl-, phenyl- or allyl-esters of lactic acid and methyl-, ethyl-, propyl-, butyl-, pentyl-, hexyl-, allyl-, benzyl- or phenyl-esters of glycolic acid. Of the above, the preferred compound is methyl-2-hydroxyisobutyrate.

[0064] According to a particular embodiment, the compound of formula (IV) is an ester of a polycarboxylic acid chosen from dicarboxylic acids and carboxylic acids having more than two acid functions. The carboxylic functions are preferably all in esterified form. The preferred esters are C1 to C4 alkyl esters.

[0065] The compound of formula (IV) may be selected from oxalic acid diesters, phthalic acid diesters, maleic acid diesters, malonic acid diesters or citric acid diesters. Preferably, the compound of formula (IV) is dimethyl oxalate.

[0066] According to a preferred variant, the compound of formula (IV) is a carboxylic acid ester having a pKa of less than 3.5. For cases where the compound comprises more than one acid group, reference will be made to the first dissociation constant.

[0067] The compound of formula (IV) may be selected from one or more carboxylic acid esters selected from oxalic acid, phthalic acid, salicylic acid, maleic acid, malonic acid, citric acid, nitrobenzoic acid, aminobenzoic acid and 2,4,6-trihydroxybenzoic acid. Preferred compounds of formula (IV) are dimethyl oxalate, methyl 2-nitrobenzoate and methyl salicylate.

[0068] According to a particularly preferred embodiment, the quaternary ammonium salt used in the invention is formed by reaction of a hydrocarbon epoxide, preferably chosen from those of formula (III) above and more preferably propylene oxide, with the product of the reaction of a polyisobutenyl succinic anhydride whose polyisobutylene (PIB) group has a number-average molecular mass (Mn) of between 700 and 1000 and dimethylaminopropylamine.

[0069] According to a particularly preferred embodiment, the additive (1) is chosen from polyisobutylene succinimides functionalized by a quaternary ammonium group.

[0070] The composition according to the invention comprises the first additive(s) as described above at a preferential content ranging from 5 to 10,000 ppm by weight, preferably from 5 to 1,000 ppm by weight, more preferentially from 10 to 500 ppm by weight, more preferentially from 15 to 200 ppm by weight, and better still from 20 to 150 ppm by weight, relative to the total weight of the fuel composition. The second additive: polyisobutylene succinimide

[0071] The composition according to the invention comprises a second additive (2) consisting of a non-quaternary polyisobutylene succinimide, that is to say that it does not contain a quaternary ammonium group.

[0072] According to a preferred embodiment, said second additive results from the condensation: of a compound A consisting of a dicarboxylic acid substituted by a polyisobutylene group or of an anhydride of such a diacid, with a compound B consisting of a primary polyamine of general formula (VI) below: H 2 N-[-(CHR1-(CH 2 ) p -CHR2) n -NH] m -H (VI) in which R1 and R2, identical or different, represent hydrogen or a hydrocarbon group comprising from 1 to 4 carbon atoms, n is an integer varying from 1 to 3, m is an integer varying from 1 to 10, preferably from 1 to 4; and p is an integer equal to 0 or 1.

[0073] In a preferred embodiment, said additive (2) is obtained by condensation of compound A with compound B, used in amounts such that the molar ratio A / B is in the range from 1:1 to 1:3.

[0074] Preferably, the molar ratio A / B is in the range from 1:1.1 to 1:2, even more preferably the molar ratio A / B is in the range from 1:1.1 to 1:1.5.

[0075] Said additive (2) can in particular be obtained by condensation of 60 to 90% by weight of compound A, and of 10 to 30% by weight of compound B.

[0076] The average molar mass of the compounds A according to the present invention varies from 200 to 3000, preferably from 200 to 2000 g / mol, preferably from 200 to 1500 g / mol, even more preferably from 900 to 1300 g / mol. These compounds are well known from the prior art.

[0077] Among the primary polyamines according to formula (VI), polyamines of the group consisting of diethylene triamine, dipropylene triamine, triethylene tetramine, tetraethylene pentamine and their substituted derivatives, or their mixtures, are preferred.

[0078] The mixture of these compounds A and B can be done indifferently in the order detailed below, or in a different order.

[0079] In a preferred embodiment, compound B, i.e. the primary polyamine of formula (VI) is added to compound A, i.e. the carboxylic acid or anhydride hydrocarbon(s).

[0080] Polyamine B is added gradually in an organic solvent, then to the solution of the mixture of carboxylic hydrocarbons at room temperature, the mixture is then heated between 65 and 250°C, and preferably between 80 and 220°C, for 5 to 30 hours.

[0081] The organic solvent required for solubilizing the primary polyamine is chosen with a boiling point of between 65 and 250°C, and preferably between 80 and 220°C, and its capacity to remove the water formed by condensation of the polyamine on compound A by azeotropic distillation of the water / solvent mixture. The solvent is chosen from the group consisting of benzene, toluene, xylenes, ethylbenzene and commercial hydrocarbon cuts, for example those distilling from 190 to 209°C and containing 99% by weight of aromatic compounds.

[0082] According to another embodiment of the invention, a mixture of solvents can be used and in particular a mixture of xylenes, or a xylene / alcohol mixture, preferably the alcohol is ethyl-2-hexanol to, on the one hand, facilitate the homogeneity of the medium and, on the other hand, promote the kinetics of the reaction.

[0083] After the addition of primary polyamine B is complete, heating is maintained under reflux until the water is completely removed, for 0.5 to 7 hours, preferably 1 to 5 hours.

[0084] In one embodiment, the composition according to the invention comprises the second additive(s) as described above at a preferential content ranging from 5 to 10,000 ppm by weight, preferably from 5 to 1,000 ppm by weight, more preferentially from 10 to 500 ppm by weight, more preferentially from 15 to 200 ppm by weight, and better still from 20 to 150 ppm by weight, relative to the total weight of the fuel composition. The third additive: Mannich base

[0085] The fuel composition according to the invention comprises a third additive (3), different from additives (1) and (2), consisting of a Mannich base. The preparation of Mannich bases is known per se, and for example described in documents US2008 / 0052985, or US8016898.

[0086] The third additive is advantageously prepared by reaction of a phenol substituted by a hydrocarbon group, an aldehyde and an amine.

[0087] The hydrocarbon substituent of said phenol may contain from 6 to 400 carbon atoms, advantageously from 30 to 180 carbon atoms, preferably from 10 to 110, better still from 40 to 110 carbon atoms.

[0088] The hydrocarbon substituent of said phenol may be derived from an olefin or a polyolefin. For example, alpha-olefins such as n-1-decene may be mentioned. Preferably, the hydrocarbon substituent of said phenol is a polyisobutylene group.

[0089] Polyolefins forming the hydrocarbon substituent of phenol can be prepared by polymerization of olefin monomers by any known polymerization method.

[0090] Advantageously, the polyolefins are chosen from polyisobutylenes having a number-average molar mass (Mn) of between 400 and 3000, preferably between 400 and 2500, more preferably between 400 and 1500, between 500 to 1500 or between 500 and 1000.

[0091] Polyisobutylene is preferably highly reactive, which differs from less reactive polyisobutylenes by their low amount of terminal ethylenic double bonds. The reactive polyisobutylenes according to the invention are composed of at least 85% by weight, preferably at least 90% by weight, preferably at least 95% by weight of isobutene units.

[0092] Preferably, the polyisobutylenes, preferably highly reactive, have a polydispersity of less than 1.9, preferably less than 1.7 and even more preferably less than 1.5, the polydispersity being the quotient of the mass average molar mass Mw and the number average molar mass Mn.

[0093] The hydrocarbon-substituted phenol may be prepared by alkylation of phenol with an olefin or polyolefin described above, such as a polyisobutylene or polypropylene, preferably a polyisobutylene, using conventional alkylation methods.

[0094] According to a variant, the phenol may be substituted by one or more low molecular weight alkyl groups, for example a phenol carrying one or more alkyl chains of less than 28 carbon atoms, preferably less than 24 carbon atoms, more preferably less than 20 carbon atoms, even more preferably less than 18 carbon atoms, even more preferably 16 carbon atoms and even more preferably 14 carbon atoms.

[0095] A monoalkyl phenol having from 4 to 20 carbon atoms, preferably from 6 to 18, more preferably from 8 to 16, even more preferably from 10 to 14 carbon atoms, for example a phenol substituted by a C12 alkyl group, will be preferred.

[0096] The aldehyde used to form the Mannich reaction product may comprise from 1 to 10 carbon atoms, and is generally formaldehyde or its reactive equivalents such as formalin (methyl alcohol and formaldehyde), trioxanes, or para-formaldehyde, and preferably, para-formaldehyde.

[0097] The amine used to form the Mannich reaction product can be a monoamine or a polyamine.

[0098] By way of non-limiting examples, monoamines that may be mentioned include ethylamine, dimethylamine, diethylamine, di-n-propylamine, di-isopropylamine, n-butylamine, dibutylamine, allylamine, isobutylamine, cocoamine, stearylamine, laurylamine, methyllaurylamine, oleylamine, N-methyloctylamine, dodecylamine, diethanolamine, morpholine, dimethylmorpholine, dicyclohexylamine, pyrrolidine, piperidine, diethylenetriamine, triethylenetetramine, N,N-diethylethylenediamine, N,N,N',N'-tetramethyldiethylenetriamine, polyethyleneimines and octadecylamine. The polyamines are chosen from compounds comprising two or more amine groups.

[0099] By way of non-limiting examples, polyamines that may be mentioned are polyalkylene polyamines in which the alkylene group has, for example, from 1 to 6, preferably from 1 to 4, more preferably from 2 to 3 carbon atoms. Preferred polyamines are polyethylene polyamines. The polyamine may comprise from 2 to 15 nitrogen atoms, preferably from 2 to 10 nitrogen atoms, preferably 2 to 8 nitrogen atoms. Examples of polyamines are: 3-(dimethylamino)-n-propylamine, di[3-(dimethylamino)-n-propyl]amine, di[3-(diethylamino)-n-propyl]amine, di[2-(dimethylamino)ethyl]amine, N-methylpiperazine,

[0100] Alternatively, the amine used to form the Mannich reaction product comprises a diamine, preferably one which comprises a primary or secondary amine function taking part in the Mannich reaction and a tertiary amine function.

[0101] According to another variant, the additive (3) can be obtained by a Mannich reaction and then subjected to a reaction making it possible to obtain a tertiary amine function; for example, a process using an intermediate compound comprising a secondary amine and obtained by Mannich reaction, which is then modified for example by alkylation to lead to a tertiary amine.

[0102] According to one embodiment, the content of the additive (3) ranges from 5 to 10,000 ppm by weight, preferably from 5 to 1,000 ppm by weight, more preferably from 50 to 500 ppm by weight, more preferably from 100 to 500 ppm by weight, and better still from 150 to 450 ppm by weight, relative to the total weight of the fuel composition. Fuel concentrate

[0103] The present invention also relates to the use, for improving the detergency properties of a gasoline fuel, of a fuel concentrate comprising at least the additives (1), (2) and (3), as defined above, in admixture with an organic liquid, said organic liquid being inert with respect to the first, second and third additives, and miscible with said fuel.

[0104] The organic liquid is advantageously miscible with liquid fuels, in particular those derived from one or more sources chosen from the group consisting of mineral sources, preferably petroleum, animal, vegetable and synthetic. Miscible means that the additives and the organic liquid form a solution or a dispersion so as to facilitate the mixing of the additives according to the invention in liquid fuels according to conventional fuel additivation processes.

[0105] The organic liquid is preferably chosen from aromatic hydrocarbon solvents such as the solvent sold under the name “SOLVESSO”, alcohols, ethers and other oxygenated compounds, and paraffinic solvents such as hexane, pentane or isoparaffins, alone or as a mixture. Fuel

[0106] The fuel according to the present invention contains a base derived from one or more sources selected from the group consisting of mineral, animal, vegetable and synthetic sources, and is preferably selected from hydrocarbon fuels, non-essentially hydrocarbon fuels and mixtures thereof.

[0107] Oil will preferably be chosen as a mineral source.

[0108] The fuel is advantageously chosen from hydrocarbon fuels and non-essentially hydrocarbon fuels, alone or in a mixture.

[0109] A hydrocarbon fuel is a fuel consisting of one or more compounds consisting solely of carbon and hydrogen. Gasoline is a hydrocarbon fuel.

[0110] A non-essentially hydrocarbon fuel is understood to mean a fuel consisting of one or more compounds consisting not essentially of carbon and hydrogen, i.e. which also contain other atoms, in particular oxygen atoms.

[0111] Hydrocarbon fuels include, in particular, light distillates having a boiling point in the gasoline range, preferably between 30 and 210°C.

[0112] These light distillates may, for example, be chosen from distillates obtained by direct distillation of crude hydrocarbons, vacuum distillates, hydrotreated distillates, distillates resulting from catalytic cracking and / or hydrocracking of vacuum distillates, distillates resulting from ARDS type conversion processes (by atmospheric residue desulfurization).

[0113] In other words, the hydrocarbon fuel is chosen from gasolines.

[0114] Gasoline includes, in particular, all commercially available spark-ignition engine fuel compositions. A representative example is gasoline meeting the NF EN 228 standard. Gasoline generally has octane numbers high enough to avoid knocking. Typically, gasoline-type fuels marketed in Europe, meeting the NF EN 228 standard, have a motor octane number (MON) greater than 85 and a research octane number (RON) of at least 95. Gasoline-type fuels generally have a RON ranging from 90 to 100 and a MON ranging from 80 to 90, with RON and MON being measured according to ASTM D 2699-86 or D 2700-86.

[0115] Non-primarily hydrocarbon fuels include oxygenates, for example, distillates resulting from the BTL (biomass to liquid) conversion of plant and / or animal biomass, taken alone or in combination; biofuels, for example, vegetable and / or animal oils and / or esters of oils; and bioethanols.

[0116] Mixtures of hydrocarbon fuel and non-primarily hydrocarbon fuel are typically Ex type gasolines.

[0117] Type Ex petrol for spark-ignition engines means a petrol fuel which contains x% (v / v) of oxygenates, generally ethanol, bioethanol and / or ethyl tert-butyl ether (ETBE).

[0118] The fuel composition may include only new distillate sources or be composed of a blend with conventional lighter petroleum distillates as a gasoline-type fuel base.

[0119] Preferably, the content of each additive (1) and (2) in the fuel composition according to the invention ranges from 5 to 10,000 ppm by weight, preferably from 5 to 1,000 ppm by weight, more preferably from 10 to 500 ppm by weight, more preferably from 15 to 200 ppm by weight, and better still from 20 to 150 ppm by weight, relative to the total weight of the fuel composition.

[0120] Preferably, the content of the additive (3) in the fuel composition according to the invention ranges from 5 to 10,000 ppm by weight, preferably from 5 to 1,000 ppm by weight, more preferably from 50 to 500 ppm by weight, more preferably from 100 to 500 ppm by weight, and better still from 150 to 450 ppm by weight, relative to the total weight of the fuel composition.

[0121] Preferably, the sulfur content in the fuel composition is less than or equal to 1500 ppm by weight, preferably less than or equal to 1000 ppm by weight, preferably less than or equal to 500 ppm by weight and preferably less than or equal to 50 ppm by weight, even more preferably less than or equal to 10 ppm by weight, relative to the total weight of the composition, and advantageously sulfur-free. Other Fuel Composition Additives

[0122] The fuel composition may also comprise one or more additional additive(s), different from said additives according to the invention.

[0123] This or these additional additive(s) may for example be chosen, in a non-limiting manner, from: detergent additives, anti-corrosion agents, antioxidants, carrier oils, dispersants, demulsifiers, tracers or markers, reodorants, friction modifiers, lubricity additives or smoothness additives, combustion aid agents (catalytic combustion and soot promoters), anti-sedimentation agents, anti-wear agents and conductivity modifying agents.

[0124] This or these additional additive(s) are more preferably chosen from: a) lubrication additives or anti-wear agents, in particular (but not limited to) chosen from the group consisting of fatty acids and their ester or amide derivatives, in particular glycerol monooleate, and mono- and polycyclic carboxylic acid derivatives. Examples of such additives are given in the following documents: EP680506, EP860494, WO98 / 04656, EP915944, FR2772783, FR2772784; b) detergent additives in particular (but not limited to) chosen from polyetheramines; c) friction or friction modifiers in particular (but not limited to) chosen from the group consisting of fatty acids or esters or mixtures of fatty acids or esters, for example oleic, linoleic, resinic, palmitic acids; or among fatty acid dimers, or mono- or di-propoxylated esters; sorbitan esters; sucrose stearates; or among glycerol and its derivatives; or pentaerythritol esters; or amines;and preferably chosen from glycerol or polyglycerol esters, or fatty acid acids or esters, or mixtures thereof; d) anti-corrosion additives, in particular (but not limited to) chosen from the group consisting of fatty acid acids or esters or mixtures of fatty acid acids or esters, or from fatty acid dimers; e) antioxidants, in particular (but not limited to) chosen from the group consisting of 2,6-di-t-butyl-4-methylphenol, t-butyl hydroquinone, 2,6 and 2,4 di-t-butylphenol, 2,4-dimethyl-6-t-butylphenol, pyrogallol, tocopherol, 4,4'-methylene bis (2,6-di-t-butylphenol), alone or as a mixture; f) carrier oils, in particular (but not limited to) chosen from the group consisting of polyoxyalkylenes such as, for example, poly-1-butene oxide or poly-propene oxide.;

[0125] These additional additives may be present in an amount ranging from 3 to 1,000 ppm (each) by weight, relative to the total weight of the fuel composition, preferably from 5 to 500 ppm. Uses

[0126] Another object of the invention is the use of the fuel composition for maintaining cleanliness (keep-clean effect) and / or cleaning (clean-up effect) deposits in the internal parts of an engine chosen from the following: the combustion chamber and the fuel injection system, and preferably the fuel injection system.

[0127] The composition according to the invention is effective in conventional engines; or more modern engines such as, IDE, BMW B48 engines, Renault H5FT and HR13DDT, PSA EB2DTS, Volkswagen EA111...; and in IIE the Mercedes M102E and M111E, PSA EW10A and EB2 engines...

[0128] Another object of the invention is the use of the fuel composition comprising at least one first additive, at least one second additive and at least one third additive defined above to prevent and / or reduce coking (i.e. coke deposits), in particular in direct gasoline injection (IDE), and / or lacquering (i.e. soap and / or varnish deposits) in particular in indirect gasoline injection (IIE), and in particular on the valves.

[0129] The invention thus makes it possible to prevent and / or reduce coke and / or soap deposits on the fuel intake valves in an indirect injection spark ignition engine. Another subject of the invention is the use of the fuel composition comprising at least one first additive, at least one second additive and at least one third additive defined above for preventing and / or reducing valve-sticking of the fuel intake valves in an engine, in particular a gasoline indirect injection spark ignition engine (IIE). In this embodiment, said composition advantageously further comprises a fourth additive which is a carrier oil.

[0130] In the case of use for combating valve sticking, the composition preferably further comprises a carrier oil. The carrier oil may be chosen from poly(oxyalkylene) type oils, for example poly(1-butene oxide) or poly(propene oxide). In one embodiment, the weight ratio of the amount of carrier oil to the amount of detergent additives is in the range from 0.1 to 2.5, preferably from 0.3 to 1.5, even more preferably from 0.5 to 1.

[0131] Another object of the invention is the use of said fuel composition for reducing the fuel consumption of the engine (“Fuel Eco” action) and / or minimizing the loss of power of said engine, and / or reducing pollutant emissions, in particular, particulate emissions from the combustion engine.

[0132] Another object of the invention is the use of said additive composition to reduce fouling of the area of the pistons, rings, and liners of the engine, preferably of a direct injection gasoline engine (or IDE).

[0133] The quaternary ammonium additive (1), as defined in the present invention, is particularly effective in combating piston fouling, in particular in IDE.

[0134] The combination of additives (1) and (2) is also very effective in combating piston fouling, particularly in IDE.

[0135] The fuel composition can be used in indirect gasoline injection (IEI) or in direct gasoline injection (IDE), preferably in IDE.

[0136] In one embodiment, the IDE is central, and in another embodiment, the IDE is lateral. The present invention is therefore effective and used in central and / or lateral IDE.

[0137] The fuel composition can also be used to combat corrosion in the engine. The additive (2) polyisobutylene succinimide, as defined in the present invention, is particularly effective in combating corrosion.

[0138] The use according to the invention is applicable to engines used in light vehicles (LV), heavy goods vehicles (HGV), stationary machinery, agricultural machinery, thermal vehicles or hybrid vehicles (rechargeable or not), dual-fuel petrol / gas engines, for example petrol / NGV (natural gas) or petrol / LPG; engines with concomitant petrol / NGV or petrol / LPG injection, etc.

[0139] The additive composition, fuel or concentrate can be used in "severe" or "easier to treat" gasolines. "Severe" gasolines are distinguished from easy to treat gasolines in that a severe gasoline requires a higher additive composition treatment rate to be effective than an "easy to treat" gasoline. "Severe" gasolines can be mentioned as gasolines similar to the CEC RF12-09 and CEC RF-83 reference gasolines. Process (or method) for preparing the fuel composition

[0140] The fuel composition according to the invention can be prepared according to any known method, by adding a liquid hydrocarbon cut as described above with at least the three additives as described above, and optionally one or more other additives different from the additives according to the invention, as described above. Method for improving engine cleanliness

[0141] The invention also relates to a method for maintaining the cleanliness and / or cleaning at least one of the internal parts of a spark-ignition engine, comprising at least the following steps: the preparation of a fuel composition by adding a fuel with at least the three additives as described above or with a concentrate comprising them, then the combustion of said fuel composition in said spark-ignition engine.

[0142] All characteristics of additives, fuel or use are applicable to the process.

[0143] According to a variant, the step of preparing a fuel composition above is preceded by a prior step of determining the content of each of the three additives to be incorporated into said fuel composition to achieve a given specification relating to the detergency properties of the fuel composition.

[0144] This preliminary step is part of current practice in the field of fuel additivation and involves defining at least one characteristic representative of the detergency properties of the fuel composition as well as a target value.

[0145] Methods for evaluating the detergent properties of fuels have been widely described in the literature and are within the general knowledge of those skilled in the art. Mention may be made, by way of non-limiting example, of the following standardized or professionally recognized tests or methods described in the literature, for indirect injection spark ignition engines: Mercedes Benz method M102E, CEC standard test method F-05-A-93, and Mercedes Benz method M111E, CEC standard test method F-20-A-98.

[0146] These methods measure inlet valve deposits (IVD), with tests typically performed on Eurosuper petrol meeting the EN228 standard.

[0147] For direct injection spark ignition engines: the method described by the applicant in the article “Evaluating Injector Fouling in Direct Injection Spark Ignition Engines”, Mathieu Arondel, Philippe China, Julien Gueit; Conventional and future energy for automobiles; 10th international colloquium; January 20-22, 2015, p.375-386 (Technische Akademie Esslingen by Techn. Akad. Esslingen, Ostfildern), for the evaluation of coking-type deposits on the injector, the method described in US20130104826, for the evaluation of coking-type deposits on the injector, the VW EA111 method under development within the framework of CEC TDG-F-113 based on the VW EA111 engine (Glawar, A., et al., "Development of a Fuel System Cleanliness Test Method in a Euro 4 Direct-Injection Gasoline Engine (VW 1.4 L TSI 90 kW)," SAE Int. J. Fuels Lubr. 10(3):2017, doi: 10.4271 / 2017-01-2296).

[0148] We can also cite the CEC L111-16 method which makes it possible to evaluate the fouling of the piston, ring and liner areas of a direct injection gasoline engine.

[0149] The following examples are given as illustrations of the invention, and should not be interpreted in such a way as to limit its scope. EXAMPLES

[0150] The following examples were made from an E-species, the characteristics of which are detailed in Table 1 below. Table 1 : characteristics of E gasoline Characteristic Method Value Density at 15°C ISO 12185 748.3 kg / m 3< Distillation profile ISO 3405 Initial point 36,2°C Point at 5% vol. 51,2°C Point at 10% vol. 54,6°C Point at 20% vol. 59,6°C Point at 30% vol. 63,9°C Point at 40% vol. 68,0°C Point at 50% vol. 92,1°C Point at 60% vol. 102,2°C Point at 70% vol. 109,2°C Point at 80% vol. 116,5°C Point at 90% vol. 138,1°C Point at 95% vol. 163,5°C Full stop 183,5°C E70 (% distilled at 70°C) 42.5% by volume E100 (% distilled at 100°C) 55.5% by volume E150 (% distilled at 150°C) 92.3% by volume Sulfur content ISO 20846 8.8 mg / kg Current unwashed gum content ISO 6246 <0.5 mg / 100mL Current washed gum content <0.5 mg / 100mL Octane rating research ISO 5164 96,2 Engine octane rating ISO 5163 86,2 Oxidation stability ISO 7536 >360 min Composition by GC ASTM D6730 n-paraffins 6.12% by weight Iso-paraffins 32.16% by weight Naphthenes 8.09% by weight Aromatics 33.63% by weight olefins 9.58% by weight ethanol 10.01% by weight Other compounds 0.41% by weight Carbon content ASTM D5291 85.5% by weight Hydrogen content ASTM D5291 13.7% by weight Calculated lower calorific value ASTM D240 41.955 MJ / kg Water content ISO 12937 260 mg / kg REID DVPE Equivalent Vapor Pressure EN 13016-1 55.6 kPa Total oxygen content MO238LA2008 0.5% by weight

[0151] Fuel compositions were prepared by adding the following additives A1, A2 and A3 to gasoline E: A1: quaternary ammonium salt, formed by reaction of propylene oxide with the condensation product of a polyisobutenyl succinic anhydride whose polyisobutylene (PIB) group has a number-average molecular mass (Mn) of 1000 g / mol and dimethylaminopropylamine; A2: polyisobutylene succinimide, obtained by condensation of a polyisobutenyl succinic anhydride whose polyisobutylene (PIB) group has a number-average molecular mass (Mn) of 1000 g / mol and tetraethylenepentamine; A3: Mannich base, obtained by reaction of a phenol substituted by a polyisobutylene (PIB) group having a number-average molecular mass (Mn) of 1000 g / mol, with formaldehyde and dimethylaminopropylamine.

[0152] The amount of additive added to each composition is detailed in Table 2 below, in which the content of each additive is indicated in ppm by weight relative to the total weight of the final composition: Table 2 : fuel compositions from E gasoline Additives added Composition E1 Composition E2 Composition E3 Composition E4 A1 50 120 0 0 A2 70 0 120 0 A3 313 313 313 313

[0153] Composition E1 is in accordance with the invention. Compositions E2, E3 and E4 are comparative. The additivation rate is identical between the three compositions E1, E2 and E3 (433 ppm).

[0154] The detergency performance of each of the above fuel compositions E1 to E4 as well as the unadditive reference fuel E were evaluated using a test to determine the level of fouling of the injectors of a gasoline direct injection (DI) engine.

[0155] The engine used is a PSA EB2DTS engine, which is a 3-cylinder 1199 cc turbocharged direct injection petrol engine with centrally positioned injectors.

[0156] Before carrying out the test, the injector flow rate is determined using an EFS IFR 600 injector flow rate measuring bench, which enables the mass fuel flow rate of the injectors to be measured in a manner known per se.

[0157] The principle of the test consists of running the engine for 5 hours at 4300 rpm and 11 bars of effective mean pressure (hereinafter referred to as PME), feeding it with the tested gasoline at an injection pressure of 70 bars, after a warm-up period of 20 minutes, and a stabilization period of 10 minutes.

[0158] The test determines the average flow loss, defined as the average restriction of the fuel flow emitted by the engine injectors at the end of the test. The higher the average flow loss, the more the fuel fouls the engine injectors and the lower its detergent performance.

[0159] The steps of the test are as follows: A heating step; A stabilization step; A fouling step; A step for determining the flow loss of the injectors.

[0160] The test conditions are as follows: Temperatures: Water at engine outlet: 90 ± 2°C Oil: 110 ± 5°C Air in intake manifold: 40 ± 2°C Low pressure fuel loop: 50 ± 2°C Fuel injection pressure: 70 bars

[0161] For the warm-up phase, the engine is subjected to a gradual increase in speed, for a period of 20 minutes, until reaching a speed of 4000 rpm and a PME of 8 bar.

[0162] For the stabilization phase, the engine is maintained at the test operating conditions, at a speed of 4300 rpm, at a PME of 11 bar and a fuel injection pressure of 70 bar, for a period of 10 minutes.

[0163] For the fouling phase, the engine then runs for 5 hours at 4300 rpm and 11 bars of PME with a fuel injection pressure of 70 bars.

[0164] At the end of the test, the injectors are removed for evaluation using the EFS IFR 600 injector flow measurement bench, which measures the injector mass fuel flow rate after the test. By comparing it with the injector mass fuel flow rate measured before the test, the average injector flow loss is calculated.

[0165] The results obtained are detailed in Table 3 below. Table 3: results Composition E1 E2 E3 E4 E Average flow loss 5,2% 6,7% 14,3% 16,2% 17,5%

[0166] The above results show that composition E1 according to the invention containing the combination of the three additives A1, A2 and A3 leads to very good results in terms of reducing injector fouling ("keep clean" effect). With an otherwise identical total additive content (433 ppm), these results are significantly better than those obtained with comparative compositions E2 and E3 containing only two of the three additives. The results obtained with composition E4 containing only one of the three additives, and with reference fuel E, are even less good.

[0167] These results illustrate the synergistic effects provided by the combination of the two additives according to the present invention.

Claims

1. Use, for reducing and / or preventing deposits in the internal parts of a spark ignition engine, of a fuel composition comprising: (1) at least one first additive consisting of a quaternary ammonium salt obtained by reacting, with a quaternisation agent, a nitrogen compound comprising a tertiary amine function, this compound being the product of the reaction of a polyisobutenyl succinic anhydride and of a compound comprising at least one tertiary amine group selected from amines of following formula (I) wherein: R6 and R7 are identical or different and represent, independently of each other, an alkyl group having from 1 to 5 carbon atoms; X is an alkylene group having from 1 to 5 carbon atoms; and R8 is a hydrogen atom, (2) at least one second additive consisting of a non-quaternary polyisobutylene succinimide, (3) at least one third additive different from the additives (1) and (2), consisting of a Mannich base, and wherein the weight ratio of the amount of the first additive to the amount of the second additive is in the range from 0.2:1 to 2.5:1.

2. The use according to claim 1, wherein the weight ratio of the amount of the first additive to the amount of the second additive is in the range from 1:1 to 2:1, and preferably from 1.25:1 to 1.5:1.

3. The use according to anyone of the preceding claims, wherein the quaternisation agent is selected from the group consisting of dialkyl sulphates, carboxylic acid esters; alkyl halides, benzyl halides, hydrocarbon carbonates, and hydrocarbon epoxides optionally in mixture with an acid, alone or in mixture , preferably from hydrocarbon epoxides or carboxylic acid esters, more preferably from styrene oxide and propylene oxide and most preferably the quaternising agent is propylene oxide.

4. The use according to any of the preceding claims, wherein the additive (2) consisting of a non-quaternary polyisobutylene succinimide results from the condensation: - of a compound A consisting of a carboxylic diacid substituted with a polyisobutylene group or of an anhydride of such a diacid; - with a compound B consisting of a primary polyamine of general formula (VI) hereafter:         H2N-[-(CHR1-(CH2)p-CHR2)n-NH]m-H     (VI) wherein R1 and R2, which are identical or different, represent hydrogen or a hydrocarbon group comprising from 1 to 4 carbon atoms, n is an integer ranging from 1 to 3, m is an integer ranging from 1 to 10, preferably from 1 to 4; and p is an integer equal to 0 or 1.

5. The use according to claim 4, wherein said additive (2) is obtained by condensation of compound A with compound B used in such amounts that the molar ratio A / B is in the range from 1:1 to 1:3, preferably 1:1.1 to 1:2, even more preferably 1:1.1 to 1:1.5.

6. The use according to any of the preceding claims, wherein the additive (3) consisting of a Mannich base is obtained by reacting a phenol substituted with a hydrocarbon group, an aldehyde and an amine, the hydrocarbon substituent of said phenol comprising from 6 to 400 carbon atoms, advantageously from 30 to 180 carbon atoms, preferably from 10 to 110, more preferably from 40 to 110 carbon atoms, and preferably being a polyisobutylene group.

7. The use according to any of the preceding claims, wherein the fuel contains a base from one or more sources selected from the group consisting of mineral, animal, vegetable and synthetic sources, and is preferably selected from hydrocarbon fuels, non-essentially hydrocarbon fuels and mixtures thereof.

8. The use according to any of the preceding claims, wherein the content of each additive (1) and (2) ranges from 5 to 10,000 ppm by weight, preferably from 5 to 1000 ppm by weight, more preferably from 10 to 500 ppm by weight, more preferably from 15 to 200 ppm by weight, and most preferably from 20 to 150 ppm by weight, based on the total weight of the fuel composition.

9. The use according to any of the preceding claims, wherein the content of the additive (3) ranges from 5 to 10,000 ppm by weight, preferably from 5 to 1000 ppm by weight, more preferably from 50 to 500 ppm by weight, more preferably from 100 to 500 ppm by weight, and most preferably from 150 to 450 ppm by weight, based on the total weight of the fuel composition.

10. The use according to any one of claims 1 to 9, for keeping clean (keep-clean effect) and / or cleaning up (clean-up effect) deposits in the internal parts of a spark ignition engine selected from the following: the combustion chamber, and the fuel injection system, and preferably the fuel injection system.

11. The use according to any one of claims 1 to 9, for preventing and / or reducing coke and / or soap deposits on the fuel intake valves in an indirect injection spark ignition engine.

12. The use according to any one of claims 1 to 9, for preventing and / or reducing valve-sticking of fuel intake valves in an indirect injection spark ignition engine.

13. The use according to any one of claims 1 to 9, wherein the additive composition is used in the fuel to reduce fuel consumption of the engine ("Fuel Eco" action) and / or minimise power loss of said engine, and / or reduce pollutant emissions, in particular particulate emissions of the combustion engine.

14. The use according to any one of claims 1 to 9, for reducing fouling of the zone of pistons, rings and liners of the engine, preferably of a gasoline direct injection (or GDI) engine.

15. A process for keeping clean and / or cleaning up at least one of the internal parts of a spark ignition engine (or gasoline internal combustion engine), comprising at least the following steps: - preparing a fuel composition by additivating a fuel with at least the additives (1), (2) and (3), as defined in any of claims 1 to 6, 8 and 9, and then - combusting said fuel composition in said spark ignition engine.

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