Fuel composition comprising fatty acid esters and an additive combination

Abstract

The present invention relates to a fuel composition comprising: a) at least one hydrocarbon base A; b) at least 30% by volume of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; c) at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms in a content ranging from 5 to 200 ppm by mass, and d) at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit in a content ranging from 2 to 100 ppm by mass. The invention also relates to the use of the two additives A1 and A2 to improve the oxidation stability of a fuel composition comprising at least 30% by volume of at least one base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

Description

[0001] The present invention relates to a fuel composition comprising a substantial amount of fatty acid esters selected from methyl and ethyl esters of fatty acids and a combination of two particular additives.

[0002] The present invention also relates to the use of such a combination of additives for improving the oxidation stability of a fuel composition comprising a substantial amount of at least one base consisting of methyl and / or ethyl esters of fatty acids STATE OF THE PRIOR ART

[0003] The fight against global warming requires the development of new fuel formulas with low environmental impact. One promising solution is to replace the fossil fuel bases traditionally used with renewable ones, particularly those of biological origin such as esters of vegetable or animal oils (including used cooking oils) transformed by a chemical process called transesterification, which consists of reacting these oils with an alcohol to obtain fatty acid esters (FAEs). With methanol and ethanol, fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEs), respectively, are obtained. These bases are commonly used in the formulation of fuel compositions, at contents that nevertheless remain moderate, around a few percent.

[0004] The trend is to increase the proportions of these renewable bases in fuel compositions as much as possible compared to conventional petroleum-based bases. In particular, for environmental reasons, resource availability and / or energy independence from fossil-based resources, increasing quantities of renewable bases must now be introduced into fuel compositions.

[0005] In particular, Decree No. 2022-08 of the French government dated January 5, 2022, has imposed since July 1, 2022 a minimum environmental performance result for all heating or domestic hot water production equipment installed in a building for residential or professional use, including as a replacement for existing equipment: the level of greenhouse gas emissions from the equipment must be less than 300 gCO2eq / kWh PCI. The greenhouse gas emissions to be considered for the application of these provisions include direct combustion as well as upstream production of fuels.

[0006] These provisions make it practically impossible to use traditional fuel compositions consisting of fossil fuel oils (FOO) in new heating and hot water production equipment. To achieve the required environmental performance, fuel compositions must contain significant quantities, at least 30% by volume, of bases consisting of fatty acid esters (FAEs).

[0007] However, the formulation of such compositions containing significant quantities of EAGs has proven to pose a number of difficulties, in particular oxidation stability. In particular, the Applicant has found that these compositions have a tendency to oxidize and therefore to degrade rapidly. This instability to fuel oxidation can lead to deposits in storage tanks, fouling of filters and fuel pumping and injection systems in equipment.

[0008] This degradation phenomenon is all the more significant when the composition must be stored. However, fuel compositions are sometimes, for various reasons, stored in tanks for long periods, which can be several weeks or even several months, before being consumed. These compositions must therefore have excellent long-term storage stability, which implies perfect stability to oxidation, at temperatures ranging from -20°C, particularly in winter, to 40°C in summer.

[0009] The Applicant has now discovered that the incorporation into the fuel composition of a combination of at least two particular additives makes it possible to solve the above-mentioned problems and to improve the oxidation stability of fuel compositions comprising significant proportions of fatty acid esters. SUBJECT OF THE INVENTION

[0010] The present invention thus relates to a fuel composition comprising: a) at least one hydrocarbon base A; b) at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; c) at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms in a total content ranging from 5 to 200 ppm by mass, relative to the total mass of the composition; and d) at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit in a total content ranging from 2 to 100 ppm by mass, relative to the total mass of the composition.

[0011] The Applicant has discovered that the combination of the two particular additives A1 and A2 defined above makes it possible to significantly improve the oxidation stability of fuel compositions containing substantial quantities of fatty acid esters, greater than or equal to 30% by volume.

[0012] Oxidation and degradation phenomena of the composition are significantly reduced, even when the composition is stored at room temperature or at temperatures below or above room temperature. The storage stability of the composition is therefore also improved.

[0013] The compositions according to the invention can thus be stored (for example in tanks, boiler storage tanks, etc.) for long periods of up to several months, in wide temperature ranges including low temperatures (below 0°C and down to approximately -20°C), room temperature (20°C) and temperatures above room temperature (up to approximately 40°C), without degradation of the latter or of its physicochemical properties.

[0014] The composition remains stable during storage, including when in contact with parts or pieces containing metals, such as copper or zinc.

[0015] The composition according to the invention has also proven to have good cold resistance. In particular, it remains fluid and homogeneous, without the appearance of crystals, at low temperatures.

[0016] This property guarantees good pumpability of the fuel composition, without risk of solid deposits or clogging of parts in contact with the composition such as transfer lines, filters, injectors, even in very cold weather.

[0017] The fuel composition according to the invention is in particular intended to supply an energy production device, preferably an electrical or thermal energy production device and more preferably a thermal energy production device such as a boiler (intended for heating and / or the production of hot water), domestic or industrial.

[0018] The present invention also relates to the use of a combination of additives comprising at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 atoms and at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit, to improve the oxidation stability of a fuel composition comprising at least one hydrocarbon base A and at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0019] The present invention also relates to an additive concentrate comprising said first and second additives A1 and A2 in particular proportions. This specific additive concentrate leads to excellent performance, in particular in terms of oxidation stability, when incorporated into a fuel composition comprising a hydrocarbon base and at least 30% by volume of a base consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0020] This additive concentrate includes: at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms; and at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit, with a weight ratio of the total quantity of the first additive(s) A1 to the total quantity of the second additive(s) A2 greater than or equal to 1.5 and strictly less than 3.

[0021] Other objects, characteristics, aspects and advantages of the invention will appear even more clearly on reading the following description.

[0022] In what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, in particular in the expressions "between" and "ranging from ... to ...".

[0023] 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".

[0024] 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 Base A

[0025] The composition according to the invention comprises at least one hydrocarbon base A.

[0026] A hydrocarbon base is a mixture consisting essentially of hydrocarbons, defined as compounds consisting solely of carbon and hydrogen. By "consisting essentially" is meant that the mixture contains at least 95% by mass, preferably at least 99% by mass and more preferably at least 99.5% by mass, of hydrocarbons.

[0027] Hydrocarbon base A may also contain, in small quantities (less than 1% by mass), compounds other than hydrocarbons, such as sulfur compounds and nitrogen compounds.

[0028] The sulfur content of base A is generally less than 0.3 by mass. The sulfur content of base A can be measured in accordance with the method described in standard NF EN ISO 14596.

[0029] According to one embodiment, the base A consists of liquid hydrocarbons of petroleum origin. It may in particular be chosen from middle distillates whose distillation interval at atmospheric pressure is in the range from 100 to 500°C, preferably from 150 to 450°C, preferably from 190 to 400°C, preferably from 210 to 350°C. In a manner known per se, the distillation intervals are expressed with reference to the ADTM D86 standard.

[0030] These middle distillates may, for example, be chosen from distillates obtained by direct distillation of crude oils, 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).

[0031] The composition may thus comprise at least one liquid hydrocarbon base A chosen from petroleum-based bases such as diesel, domestic fuel oil (DFO) and heavy fuel oil, preferably domestic fuel oil-type bases.

[0032] Preferably, the composition according to the invention comprises the base(s) A in a total content of at least 50% by volume, relative to the total volume of the composition.

[0033] More preferably, the total content of the base(s) A is in the range from 50 to 70% by volume, preferably from 55 to 60% by volume, relative to the total volume of the composition. Base B

[0034] The composition according to the invention comprises at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids, in a content of at least 30% by volume.

[0035] Such a composition may be referred to as "Fx", with X being a number greater than or equal to 30 and strictly less than 100, designating the total percentage by volume of methyl and ethyl esters of fatty acids relative to the total volume of bases contained in the composition (i.e. without taking into account the volume of additives). For example, a FOD type fuel called F30 is formulated from a mixture of bases consisting of 30% by volume of fatty acid esters (FAE) and 70% by volume of middle distillates of fossil origin (mineral source), a fuel called F40 is formulated from a mixture of bases consisting of 40% by volume of FAE and 60% by volume of middle distillates of fossil origin, etc.

[0036] By fatty acid is meant a monocarboxylic acid comprising a saturated or unsaturated hydrocarbon chain having from 6 to 30 carbon atoms, preferably from 7 to 24 carbon atoms, and more preferably from 8 to 20 carbon atoms.

[0037] Said esters are therefore chosen from esters of methyl alcohol and / or ethyl alcohol and one or more C6 to C30 fatty acids, preferably C7 to C24 and more preferably C8 to C20.

[0038] These esters are products known per se. They can be advantageously obtained by reacting at least one oil chosen from vegetable oils, animal oils and used oils with methanol or ethanol, so as to obtain the corresponding esters by a chemical process called transesterification.

[0039] When the alcohol is methanol, we obtain a mixture of fatty acid methyl esters also called EMAG.

[0040] When the alcohol is ethanol, we obtain a mixture of fatty acid ethyl esters also called EEAG.

[0041] According to a preferred embodiment, the ester(s) are chosen from fatty acid methyl esters. Preferably, base B consists of a mixture of fatty acid methyl esters (FAME).

[0042] The composition according to the invention comprises the base(s) B in a minimum content of 30% by volume.

[0043] More preferably, the total content of the base(s) B is in the range from 30 to 60% by volume, preferably from 40 to 50% by volume, relative to the total volume of the composition.

[0044] In other words, the composition according to the invention may be a fuel of type Fx with X a number in the range from 30 to 60 and designating the total percentage by volume of methyl and ethyl esters of fatty acids relative to the total volume of bases contained in the composition, i.e. without taking into account the volume of additives, which in the context of the present invention remains negligible. In particular, the composition according to the invention is advantageously a composition corresponding to the designation F30, F35, F40, F45 or F50.

[0045] According to a preferred embodiment, the composition according to the invention comprises a mixture of fatty acid methyl esters (FAME) in a minimum content of 30% by volume, preferably a content in the range from 30 to 60% by volume, more preferably from 40 to 50% by volume, relative to the total volume of the composition.

[0046] In this embodiment, the composition is a fuel of type Fx with X a number in the range from 30 to 60 and designating the percentage by volume of fatty acid methyl esters relative to the total volume of bases contained in the composition, i.e. without taking into account the volume of additives, which in the context of the present invention remains negligible. In particular, the composition according to the invention may be a fuel corresponding to the designation F30, F35, F40, F45 or F50. The first A1 additive

[0047] Said first additive A1 is chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms. The C 1 to C 4 alkyl groups are more preferably chosen from methyl, ethyl and t-butyl (or tert-butyl) groups.

[0048] The additive(s) A1 are more preferably chosen from methyl-t-butyl phenols, dimethyl-t-butyl phenols, ethyl-t-butyl phenols, t-butyl phenols, di-t-butyl phenols, tri-t-butyl phenols, di-t-butyl-methyl phenols, di-t-butyl-di-methyl phenols, trimethyl phenols, and mixtures thereof.

[0049] Preferred compounds are selected from 2,6-di-t-butyl-4-methylphenol (BHT), 4,6-di-tert-butyl-2-methylphenol, 2,6 and 2,4 di-t-butyl phenol, 2,4-dimethyl-6-t-butyl phenol, 2,5-dimethyl-4-t-butyl phenol, 2,4,6-tri-t-butyl phenol, 2,3,6-trimethyl phenol, 2,4,6-trimethyl phenol, and mixtures thereof.

[0050] More preferred compounds are 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, and mixtures thereof.

[0051] Particularly preferably, the composition according to the invention contains 2,6-di-t-butyl-4-methyl phenol (BHT).

[0052] According to a preferred embodiment, the composition comprises a mixture of at least two different additives A1 as described above, and more preferably of at least two different additives chosen from 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol and 2,4,6-tri-t-butyl phenol.

[0053] According to a particular embodiment, the composition comprises a mixture of three different additives A1 as described above, and more preferably a mixture of 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol and 2,4,6-tri-t-butyl phenol.

[0054] The composition according to the invention comprises the additive(s) A1 as described above in a total content ranging from 5 to 200 ppm, preferably from 10 to 100 ppm, and better still from 20 to 60 ppm by mass, relative to the total mass of the composition. The second additive A2

[0055] Said second additive A2 is chosen from triazole derivatives.

[0056] As is known per se, the term "triazole derivatives" refers to all compounds comprising at least one triazole unit, i.e. a 5-membered aromatic ring unit, comprising two double bonds and 3 nitrogen atoms. Depending on the position of the nitrogen atoms, a distinction is made between 1,2,3-triazole units (called V-triazoles) and 1,2,4-triazole units (called S-triazoles).

[0057] The triazole derivative(s) used in the invention are chosen from amines substituted by one or more groups comprising a triazole unit, as defined above.

[0058] Preferred compounds are N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine (CAS 91273-04-0) and N,N'-bis-(2 ethylhexyl)-4-methyl-1H-benzotriazole amine (CAS 80584-90-3), and mixtures thereof.

[0059] Particularly preferably, the composition according to the invention contains N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, which is a triazole derivative of the following structural formula:

[0060] The composition according to the invention comprises the additive(s) A2 as described above in a total content ranging from 2 to 100 ppm, preferably from 2 to 50 ppm, more preferably from 5 to 20 ppm by mass, relative to the total mass of the composition.

[0061] According to a preferred embodiment, the composition according to the invention comprises N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine in a content ranging from 2 to 100 ppm, preferably from 2 to 50 ppm, more preferably from 5 to 20 ppm by mass, relative to the total mass of the composition.

[0062] Preferably, the weight ratio between the content of said first additive A1 and the content of said second additive A2 in the composition is greater than or equal to 1.5 and strictly less than 3, more preferably within the range from 2 to 2.9 and better still from 2.5 to 2.8. Other optional additives:

[0063] The composition according to the invention may also comprise one or more additional additives, different from alkyl phenols (additives A1) and triazole derivatives (additives A2) as described above.

[0064] Preferably, the composition according to the invention further comprises one or more cold resistance additives, or pour point lowering additives.

[0065] These additives may advantageously be chosen from copolymers comprising units derived from ethylene and vinyl acetate such as in particular ethylene / vinyl acetate (EVA) and / or ethylene / vinyl propionate (EVP) copolymers, ethylene / vinyl acetate / vinyl versatate (EA / AA / EOVA) terpolymers; ethylene / vinyl acetate / alkyl acrylate terpolymers and in particular ethylene / vinyl acetate / 2-ethylhexyl acrylate terpolymers; as well as EVA copolymers modified by grafting.

[0066] Mention may also be made of polyacrylates; acrylate / vinyl acetate / maleic anhydride terpolymers; amidated maleic anhydride / alkyl(meth)acrylate copolymers capable of being obtained by reaction of a maleic anhydride / alkyl(meth)acrylate copolymer and an alkylamine or polyalkylamine having a hydrocarbon chain of 4 to 30 carbon atoms, preferably of 12 to 24 carbon atoms; amidated alpha-olefin / maleic anhydride copolymers obtainable by reaction of an alpha-olefin / maleic anhydride copolymer and an alkylamine or polyalkylamine, the alpha-olefin being able to be chosen from C10-C50 alpha-olefins, preferably C16-C20, and the alkylamine or polyalkylamine advantageously having a hydrocarbon chain of 4 to 30 carbon atoms, preferably 12 to 24 carbon atoms.Examples of terpolymers include those described in EP01692196, WO2009106743, WO2009106744, US4758365 and US4178951.

[0067] According to a preferred embodiment, the composition according to the invention comprises at least one cold resistance additive chosen from ethylene / vinyl acetate / alkyl acrylate terpolymers and more preferably from ethylene / vinyl acetate / 2-ethylhexyl acrylate terpolymers.

[0068] The cold-holding additive(s) are preferably present in a total content ranging from 10 to 500 ppm, preferably from 20 to 300 ppm, more preferably from 50 to 200 ppm, by mass, relative to the total mass of the composition.

[0069] According to a preferred embodiment, when the composition comprises one or more cold-holding additives as described above, it also contains a mixture of at least two different additives A1 as described above, and more preferably of at least two different additives chosen from 2,6-di-t-butyl-4-methylphenol (BHT), 2,6 di-t-butylphenol and 2,4,6-tri-t-butylphenol.

[0070] According to a variant of this embodiment, the composition comprises a mixture of three different additives A1 as described above, and more preferably a mixture of 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol and 2,4,6-tri-t-butyl phenol.

[0071] The composition according to the invention may also further comprise one or more cetane index improving additives, also known as procetane additives or cetane booster additives.

[0072] These additives can be chosen in particular from alkyl nitrates and aryl or alkyl peroxides.

[0073] Aryl peroxides include benzyl peroxide. Alkyl peroxides include tert-butyl peroxide.

[0074] The procetane additives are preferably chosen from alkyl nitrates, and more preferably those of formula R-NO 3 with R an alkyl radical comprising from 2 to 12 carbon atoms, preferably from 4 to 8 carbon atoms. A particularly preferred additive is 2-ethylhexyl nitrate.

[0075] The procetane additive(s) may be present in a total content ranging from 10 to 500 ppm, preferably from 20 to 300 ppm, more preferably from 50 to 200 ppm, by mass, relative to the total mass of the composition.

[0076] The composition according to the invention may also comprise one or more other additives commonly used in fuels, different from the additives described previously.

[0077] The composition may thus include one or more other additives chosen from, but not limited to: anti-corrosion agents, friction modifiers, reodorants, tracers, biocides.

[0078] These other additives are generally added in amounts ranging from 1 to 500 ppm each. The use

[0079] The present invention also relates to the use of a combination of additives comprising at least one first additive A1 as described above and at least one second additive A2 as described above, to improve the oxidation stability of a fuel composition comprising at least one hydrocarbon base A and at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids.

[0080] The fuel composition is as described above. In particular, the description of base A, base B and said first additive A1 and second additive A2 applies to the use, including the preferred embodiments.

[0081] As indicated above, the fuel composition preferably comprises the base(s) B in a content in the range from 30 to 60% by volume, more preferably from 40 to 50% by volume, relative to the total volume of the composition.

[0082] Said first additive A1 is used in the fuel composition in a content in the range from 5 to 200 ppm, preferably from 10 to 100 ppm, and better still from 20 to 60 ppm by mass, relative to the total mass of the composition.

[0083] Said second additive A2 is used in the fuel composition in a content in the range from 2 to 100 ppm, preferably from 2 to 50 ppm, more preferably from 5 to 20 ppm by mass, relative to the total mass of the composition.

[0084] Preferably, the weight ratio between the content of said first additive A1 and the content of said second additive A2 in the composition is greater than or equal to 1.5 and strictly less than 3, more preferably within the range from 2 to 2.9 and better still from 2.5 to 2.8.

[0085] The oxidation stability of the composition can be evaluated in accordance with the method defined in ASTM D7545-14.

[0086] This oxidation stability of the composition persists over time. In other words, the composition is stable during storage, this storage stability being determined by monitoring the oxidation stability of the composition after storage for a specific period.

[0087] Preferably, the composition according to the invention is stable during storage, after a storage period of at least three months (90 days) at room temperature (20°C) and at atmospheric pressure (1,013.10 5< Pa).

[0088] More preferably, the composition is also stable during storage, after a storage period of at least three months (90 days) at a temperature of 30°C and at atmospheric pressure (1,013.10 5< Pa).

[0089] Even more preferably, the composition is also stable during storage, after a storage period of at least three months (90 days) at a temperature of 40°C and at atmospheric pressure (1,013.10 5< Pa). The method:

[0090] The present invention also relates to a method for improving the oxidation stability of a fuel composition comprising at least one hydrocarbon base A and at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids, consisting of adding to said composition a combination of additives comprising at least one first additive A1 and at least one second additive A2 as described above. The additive concentrate

[0091] The additive concentrate useful for implementing the present invention comprises: at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms; and at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit, with a weight ratio of the total quantity of the first additive(s) A1 to the total quantity of the second additive(s) A2 greater than or equal to 1.5 and strictly less than 3, preferably within the range from 2 to 2.9 and more preferably from 2.5 to 2.8.

[0092] The additive concentrate advantageously comprises said additives A1 and A2 in a content of at least 4% by mass, relative to the total mass of said concentrate, and preferably in a content ranging from 5 to 10% by mass, relative to the total mass of said concentrate.

[0093] Said first additive A1 and second additive A2 are as described above.

[0094] According to a preferred embodiment, the additive concentrate comprises: at least one first additive A1 chosen from 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, and mixtures thereof; and at least one second additive A2 chosen from N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, N,N'-bis-(2 ethylhexyl)-4-methyl-1H-benzotriazole amine (CAS 80584-90-3), and mixtures thereof; preferably N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine; with a weight ratio of the total quantity of the first additive(s) A1 to the total quantity of the second additive(s) A2 greater than or equal to to 1.5 and strictly less than 3, preferably within the range from 2 to 2.9 and more preferably from 2.5 to 2.8.

[0095] The additive concentrate advantageously further comprises at least one organic solvent, which may be chosen, for example, from aromatic hydrocarbon solvents, alcohols, ethers, esters, oils, paraffinic solvents such as hexane, pentane or isoparaffins, including hydrotreated vegetable oils known as HVO, alone or as a mixture.

[0096] According to a preferred embodiment, the additive concentrate comprises at least one aromatic hydrocarbon solvent, i.e. a solvent consisting of an aromatic hydrocarbon or a mixture of hydrocarbons essentially comprising aromatic hydrocarbons.

[0097] Examples of aromatic hydrocarbons include toluene, xylenes.

[0098] Solvents based on aromatic hydrocarbons are known, and for example marketed under the names SOLVESSO ®< , SOLVAREX ®< ,..

[0099] The additive concentrate preferably comprises one or more organic solvents in a total content of at least 40% by mass, preferably at least 50% by mass, relative to the total mass of said concentrate.

[0100] Preferably, the additive concentrate further comprises one or more cold-holding additives, advantageously chosen from copolymers comprising units derived from ethylene and acrylic or methacrylic acid, such as, for example, polymers of ethylene, acrylic acid and acetic acid.

[0101] The additive concentrate may further comprise one or more other additives chosen from, for example and in a non-limiting manner: procetane additives, anti-corrosion agents, friction modifiers, reodorants, tracers, biocides.

[0102] 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

[0103] A fuel composition of type F30 was prepared by mixing: a hydrocarbon base A consisting of a domestic fuel oil (DFO) type cut with a content of 70% by volume; with a base B consisting of fatty acid methyl esters with a content of 30% by volume.

[0104] This reference composition is called C0.

[0105] The characteristics of base A are detailed in Table I below: [Tableau I] Characteristic Method Value Density at 15°C ISO 12185 835.1 kg / m 3< Viscosity at 40°C ISO 3104 2.7 mm 2 < / s Cloud Point (CTP)° EN 23015 -2°C Filterability Limit Temperature (FLT) EN 116 -17°C Distillation profile ISO 3405 Initial point 158,2°C Point 5% vol. 178,0°C Point 10% vol. 188,9°C Point 20% vol. 211,0°C Point 30% vol. 233,9°C Point 40% vol. 256,8°C Point 50% vol. 274,4°C Point 60% vol. 290,3°C Point 70% vol. 306,6°C Point 80% vol. 324,6°C Point 90% vol. 346,9°C Point 95% vol. 362,1°C Full stop 372,1°C Residue 1.5% volume Losses 0.5% volume Sulfur content ISO 20846 0.06% mass Aromatic compound content EN 12916 25.8% mass

[0106] The characteristics of base B are detailed in Table II below: [Table II] Characteristic Method Value Density at 15°C ISO 12185 883.1 kg / m 3< Viscosity at 40°C ISO 3104 4.4 mm 2 < / s Filterability Limit Temperature (FLT) EN 116 -13°C Ester content EN 14103 96.8% by mass

[0107] A composition C3 according to the invention and two comparative compositions C1 and C2 were prepared by adding the following additives to composition C0: A1: Mixture of 2,6-di-t-butyl-4-methylphenol (BHT) and 2,4,6-tri-tertbutylphenol at a total content of 40 ppm by mass; A2: N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine at a content of 15 ppm by mass.

[0108] The weight ratio between the quantities of the respective additives A1 and A2 in composition C3 is 2.7.

[0109] The ingredients of the four tested compositions are detailed in Table III below: [Tableau III] Composition C0 C1 C2 C3 Base A (FOD) 70% vol 70% vol 70% vol 70% vol Base B (EMAG° 30% vol 30% vol 30% vol 30% vol Additive A1 - 40 ppm - 40 ppm Additive A2 - - 15 ppm 15 ppm

[0110] Each composition was subjected to accelerated aging by dipping a copper blade into it, in accordance with the conditions defined in standard NF EN 15751.

[0111] The oxidation stability of each composition was then evaluated according to the method defined in ASTM D7545-14, which allows the measurement under specific conditions of an induction period whose value is representative of the oxidation and storage stability of the tested sample. The longer the induction period, the more stable the composition.

[0112] The results obtained are shown in Table III below. [Table IV] Composition C0 C1 C2 C3 Induction period (min) 14,4 12,0 39,1 71

[0113] These results show that composition C3 according to the invention has a stability that is significantly higher than that of the comparative compositions C0, C1 and C2. In composition C3 according to the invention, a synergistic result is observed, provided by the combination of additives A1 and A2.

Claims

1. Fuel composition comprising: a) at least one hydrocarbon base A; b) at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; c) at least one first additive A1 chosen from alkyl phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms in a total content ranging from 5 to 200 ppm by mass, relative to the total mass of the composition; and d) at least one second additive A2 chosen from amines substituted by one or more groups comprising a triazole unit in a total content ranging from 2 to 100 ppm by mass, relative to the total mass of the composition.

2. Composition according to the preceding claim, characterized in thatbase A consists of liquid hydrocarbons of petroleum origin, preferably chosen from middle distillates whose distillation interval at atmospheric pressure is in the range from 100 to 500°C, preferably from 150 to 450°C, more preferably from 190 to 400°C, and even more preferably from 210 to 350°C.

3. Composition according to any one of the preceding claims, characterized in that Base B consists of a mixture of fatty acid methyl esters.

4. Composition according to any one of the preceding claims, characterized in that it comprises the base(s) B in a total content in the range from 30 to 60% by volume, preferably from 40 to 50% by volume, relative to the total volume of the composition.

5. Composition according to any one of the preceding claims, characterized in thatthe additive(s) A1 are chosen from methyl-t-butyl phenols, dimethyl-t-butyl phenols, ethyl-t-butyl phenols, t-butyl phenols, di-t-butyl phenols, tri-t-butyl phenols, di-t-butyl-methyl phenols, di-t-butyl-di-methyl phenols, trimethyl phenols, and mixtures thereof.

6. Composition according to any one of the preceding claims, characterized in that the additive(s) A1 are chosen from 2,6-di-t-butyl-4-methylphenol (BHT), 4,6-di-tert-butyl-2-methylphenol, 2,6 and 2,4 di-t-butyl phenol, 2,4-dimethyl-6-t-butyl phenol, 2,5-dimethyl-4-t-butyl phenol, 2,4,6-tri-t-butyl phenol, 2,3,6-trimethyl phenol, 2,4,6-trimethyl phenol, and mixtures thereof, and preferably from 2,6-di-t-butyl-4-methylphenol (BHT), 2,6 di-t-butyl phenol, 2,4,6-tri-t-butyl phenol, and mixtures thereof.

7. Composition according to any one of the preceding claims, characterized in thatit comprises a mixture of at least two different additives A1, preferably chosen from 2,6-di-t-butyl-4-methyl phenol (BHT), 2,6 di-t-butyl phenol and 2,4,6-tri-t-butyl phenol.

8. Composition according to any one of the preceding claims, characterized in that it comprises the additive(s) A1 in a total content ranging from 10 to 100 ppm, preferably from 20 to 60 ppm by mass, relative to the total mass of the composition.

9. Composition according to any one of the preceding claims, characterized in that the additive(s) A2 are chosen from N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, N,N'-bis-(2 ethylhexyl)-4-methyl-1H-benzotriazole amine and mixtures thereof; and preferably the composition contains N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine.

10. Composition according to any one of the preceding claims, characterized in thatit comprises the additive(s) A2 in a total content ranging from 2 to 50 ppm, preferably from 5 to 20 ppm by mass, relative to the total mass of the composition.

11. Composition according to any one of the preceding claims, characterized in that it further comprises one or more cold resistance additives, preferably chosen from copolymers comprising units derived from ethylene and vinyl acetate, more preferably from ethylene / vinyl acetate / alkyl acrylate terpolymers and even more preferably from ethylene / vinyl acetate / 2-ethylhexyl acrylate terpolymers.

12. Use of a combination of additives comprising at least one first additive A1 as defined in any one of claims 1 and 5 to 7 and at least one second additive A2 as defined in any one of claims 1 and 9, for improving the oxidation stability of a fuel composition comprising at least one hydrocarbon base A and at least 30% by volume, relative to the total volume of the composition, of at least one base B consisting of one or more esters chosen from methyl esters and ethyl esters of fatty acids; said first additive A1 being used in a total content ranging from 5 to 200 ppm by mass, relative to the total mass of the composition and said second additive A2 being used in a total content ranging from 2 to 100 ppm by mass, relative to the total mass of the composition.

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