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 fatty acid methyl and ethyl esters and a combination of two particular additives.

[0002] The present invention also relates to the use of such a combination of additives to improve 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. PREVIOUS STATE OF THE ART

[0003] Combating climate change requires developing new fuel formulations with a low environmental impact. A promising solution is to replace traditionally used fossil fuel bases with renewable ones, particularly bio-based bases such as vegetable or animal oil esters (including used cooking oils) transformed by a chemical process called transesterification. This process involves reacting these oils with an alcohol to obtain fatty acid esters (FAEs). With methanol and ethanol, this process yields fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs), respectively. These bases are commonly used in fuel formulations, albeit at moderate levels, on the order of a few percent.

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

[0005] In particular, French government decree No. 2022-08 of January 5, 2022, mandates, as of July 1, 2022, a minimum environmental performance level for all heating or domestic hot water production equipment installed in residential or commercial buildings, including when replacing existing equipment: the equipment's greenhouse gas emissions must be less than 300 gCO2eq / kWh LHV. The greenhouse gas emissions considered for the application of these provisions include direct combustion as well as upstream fuel production.

[0006] These provisions effectively make it impossible to use traditional fuel compositions based on fossil fuel oil 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 composed of fatty acid esters (FAEs).

[0007] However, formulating such compositions containing significant amounts of EAGs has proven to present a number of difficulties, particularly regarding oxidation stability. Specifically, the Applicant has observed that these compositions tend to oxidize and therefore degrade rapidly. This oxidation instability of the fuel can lead to deposits in storage tanks, fouling of filters, and clogging of 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 extended periods, which can be several weeks or even several months, before being used. These compositions must therefore exhibit excellent long-term storage stability, which implies perfect oxidation stability at temperatures ranging from -20°C, particularly in winter, to 40°C in summer. WO 2008 / 065015 A1 concerns the oxidation and storage stability of biodiesel through the combined presence of a substituted phenolic antioxidant and a triazole derivative.

[0009] The Applicant has now discovered that incorporating a combination of at least two specific additives into the fuel composition makes it possible to resolve the aforementioned 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 selected from methyl esters and ethyl esters of fatty acids; c) at least one first additive A1 selected from alkyl-phenols comprising a phenolic ring substituted by several alkyl groups comprising from 1 to 4 carbon atoms in a total content of 5 to 200 ppm by mass, relative to the total mass of the composition; and d) at least one second additive A2 selected from amines substituted by one or more groups comprising a triazole motif in a total content of 2 to 100 ppm by mass, relative to the total mass of the composition.

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

[0012] Oxidation and degradation 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 significant periods of time up to several months, in wide temperature ranges including low temperatures (below 0°C and down to about -20°C), ambient temperature (20°C) and temperatures above ambient temperature (up to about 40°C), without degradation of the latter or of its physico-chemical properties.

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

[0015] The composition according to the invention has also been shown to exhibit good cold stability. In particular, it remains fluid and homogeneous, without the formation of crystals, at low temperatures.

[0016] This property ensures 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, including in very cold weather.

[0017] The fuel composition according to the invention is in particular intended to power 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 hot water production), domestic or industrial.

[0018] The present invention also relates to the use of a combination of additives comprising at least a first additive A1 selected from alkyl-phenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 atoms of and at least a second additive A2 selected from amines substituted by one or more groups comprising a triazole motif, 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 selected from methyl esters and ethyl esters of fatty acids.

[0019] The product described is also an additive concentrate comprising the aforementioned first and second additives A1 and A2 in specific proportions. This specific additive concentrate leads to excellent performance, particularly 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 selected from among methyl esters and ethyl esters of fatty acids.

[0020] This concentrated additive package includes: at least one first additive A1 chosen from alkylphenols 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 motif, 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, features, aspects and advantages of the invention will become even clearer upon reading the description that follows.

[0022] In what follows, and unless otherwise indicated, the boundaries of a range of values ​​are included in that range, 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 to".

[0024] Finally, in a manner known in itself, a compound or group in CN is designated as a compound or group containing in its chemical structure N carbon atoms. DETAILED DESCRIPTION Base A

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

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

[0027] The 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 according to the method described in standard NF EN ISO 14596.

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

[0030] These middle distillates can, for example, be chosen from distillates obtained by direct distillation of crude oils, vacuum distillates, hydrotreated distillates, distillates from catalytic cracking and / or hydrocracking of vacuum distillates, distillates resulting from ARDS type conversion processes (by desulfurization of atmospheric residue).

[0031] The composition may therefore include at least one liquid hydrocarbon base A chosen from petroleum-based bases such as diesel, domestic fuel oils (FFO) and heavy fuel oils, 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 base(s) A is in the range of 50 to 70% by volume, preferably 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 selected from methyl esters and ethyl esters of fatty acids, in a content of at least 30% by volume.

[0035] Such a composition can be designated as "FX," where X is a number greater than or equal to 30 and strictly less than 100, representing the total volume percentage of fatty acid methyl and ethyl esters relative to the total volume of bases in the composition (i.e., without taking into account the volume of additives). For example, a fuel of the FOD type designated 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 designated 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, and so on.

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

[0037] The said esters are therefore chosen from among the esters of methyl alcohol and / or ethyl alcohol and one or more fatty acids in C 6 to C 30, preferably in C 7 to C 24 and more preferably in C 8 to C 20.

[0038] These esters are known products in themselves. 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, a mixture of fatty acid methyl esters, also known as EMAG, is obtained.

[0040] When the alcohol is ethanol, a mixture of fatty acid ethyl esters, also known as EEAG, is obtained.

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

[0044] In other words, the composition according to the invention can be a type FX fuel, where X is a number in the range of 30 to 60, denoting the total volume percentage of fatty acid methyl and ethyl esters relative to the total volume of bases contained in the composition—that is, 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 of 30 to 60% by volume, more preferably 40 to 50% by volume, relative to the total volume of the composition.

[0046] In this embodiment, the composition is a type FX fuel, where X is a number in the range of 30 to 60, denoting the volume percentage 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] The first additive A1 is chosen from among alkylphenols comprising a phenolic nucleus substituted by several alkyl groups comprising from 1 to 4 carbon atoms. The alkyl groups at C1 to C4 are most preferentially chosen from among the methyl, ethyl and t-butyl (or tert-butyl) groups.

[0048] The A1 additive(s) are most preferably chosen from among 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] Preferred compounds include 2,6-di-t-butyl-4-methylphenol (BHT), 2,6-di-t-butylphenol, 2,4,6-tri-t-butylphenol, and mixtures thereof.

[0051] In a particularly preferred manner, the composition according to the invention contains 2,6-di-t-butyl-4-methylphenol (BHT).

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

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

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

[0055] The said second additive A2 is chosen from among the triazole derivatives.

[0056] The term "triazole derivatives" is well-known and refers to all compounds containing at least one triazole unit, that is, a 5-membered aromatic ring with two double bonds and three 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 among amines substituted by one or more groups comprising a triazole motif, 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] In a particularly preferred manner, 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 with the following structural formula:

[0060] The composition according to the invention comprises the additive(s) A2 as described above in a total content of 2 to 100 ppm, preferably 2 to 50 ppm, more preferably 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 of 2 to 2.9 and better from 2.5 to 2.8. Other optional additives:

[0063] The composition according to the invention may also include one or more additional additives, different from selected 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-hold additives, or pour point lowering additives.

[0065] These additives can advantageously be chosen from copolymers comprising motifs 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 graft-modified EVA copolymers.

[0066] We can also mention polyacrylates; acrylate / vinyl acetate / maleic anhydride terpolymers; amidated maleic anhydride / alkyl(meth)acrylate copolymers that can be obtained by reacting a maleic anhydride / alkyl(meth)acrylate copolymer with an alkylamine or polyalkylamine having a hydrocarbon chain of 4 and 30 carbon atoms, preferably of 12 to 24 carbon atoms; Amidified alpha-olefin / maleic anhydride copolymers that can be obtained by reacting an alpha-olefin / maleic anhydride copolymer with an alkylamine or polyalkylamine, the alpha-olefin being selectable from C10-C50 alpha-olefins, preferably C16-C20, and the alkylamine or polyalkylamine advantageously having a hydrocarbon chain of 4 and 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-hold additive selected 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 of 10 to 500 ppm, preferably 20 to 300 ppm, more preferably 50 to 200 ppm, by mass, relative to the total mass of the composition.

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

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

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

[0073] Among the aryl peroxides, benzyl peroxide is a notable example. Among the alkyl peroxides, tert-butyl peroxide is a notable example.

[0074] Procetane additives are preferably chosen from among the alkyl nitrates, and more preferably those of the formula R-NO3, where R is an alkyl radical comprising 2 to 12 carbon atoms, preferably 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 include one or more other additives commonly used in fuels, different from the additives described above.

[0077] The composition may therefore 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 quantities 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 a first additive A1 as described above and at least a 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 selected 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 preferred embodiments.

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

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

[0083] The said second additive A2 is used in the fuel composition at a content in the range of 2 to 100 ppm, preferably 2 to 50 ppm, more preferably 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 of 2 to 2.9 and better 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 specified period.

[0087] Preferably, the composition according to the invention is stable in storage, after a storage period of at least three months (90 days) at room temperature (20°C) and atmospheric pressure (1.013.10 5< Pa).

[0088] Preferably, the composition is also stable in 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 in 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] Described is also 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 selected 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 alkylphenols 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 motif, 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 of 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] The said first additive A1 and second additive A2 are as described above.

[0094] In a preferred embodiment, the additive concentrate comprises: at least one first additive A1 selected from 2,6-di-t-butyl-4-methylphenol (BHT), 2,6-di-t-butylphenol, 2,4,6-tri-t-butylphenol, and mixtures thereof; and at least one second additive A2 selected 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 at 1.5 and strictly less than 3, preferably within the range of 2 to 2.9 and more preferably from 2.5 to 2.8.

[0095] The additive concentrate advantageously also includes 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 in mixture.

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

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

[0098] Aromatic hydrocarbon-based solvents 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 also includes one or more cold-strength additives, advantageously chosen from copolymers comprising motifs 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 also include one or more other additives chosen from, for example and without limitation: procetane additives, anti-corrosion agents, friction modifiers, reodorants, tracers, biocides.

[0102] The examples below are given as an illustration of the invention, and should not be interpreted in such a way as to limit its scope. EXAMPLES

[0103] An F30 type fuel composition was prepared by mixing: a hydrocarbon base A consisting of a domestic fuel oil (DFO) cut at a content of 70% by volume; with a base B consisting of fatty acid methyl esters at 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 / m³ Viscosity at 40°C ISO 3104 2.7 mm² / s Trouble Point (PTR) EN 23015 -2°C Filterability limit temperature (FLT) EN 116 -17°C Distillation profile ISO 3405 Starting 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% by volume Losses 0.5% by volume Sulfur content ISO 20846 0.06% by 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 / m³ Viscosity at 40°C ISO 3104 4.4 mm² / 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-tert-butylphenol 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 immersing a copper strip in it, in accordance with the conditions defined in the NF EN 15751 standard.

[0111] The oxidation stability of each composition was then evaluated according to the method defined in ASTM D7545-14, which allows for the measurement, under specified 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 exhibits significantly greater stability than the comparative compositions C0, C1, and C2. In composition C3 according to the invention, a synergistic result is observed due to 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 fatty acid methyl esters and fatty acid ethyl esters; c) at least one first additive A1 chosen from alkylphenols comprising a phenolic ring substituted by a plurality of 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 that the base A consists of liquid hydrocarbons of petroleum origin, preferably chosen from middle distillates having a distillation range at atmospheric pressure which is within the range extending from 100°C to 500°C, preferably from 150°C to 450°C, more preferentially from 190°C to 400°C, and even more preferentially from 210°C to 350°C.

3. Composition according to either one of the preceding claims, characterized in that the 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 within the range extending 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 that the additive(s) A1 is (are) chosen from methyl-t-butylphenols, dimethyl-t-butylphenols, ethyl-t-butylphenols, t-butylphenols, dit-butylphenols, tri-t-butylphenols, di-t-butylmethylphenols, di-t-butyldimethylphenols, trimethylphenols, and mixtures thereof.

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

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

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 is (are) chosen from N,N-bis(2-ethylhexyl)-[(1,2,4-triazol-1-yl)methyl]amine, N,N'-bis(2-ethylhexyl)aminomethyl-4-methyl-1H-benzotriazole 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 that it 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 also comprises one or more cold flow improvers, preferably chosen from copolymers comprising units derived from ethylene and vinyl acetate, more preferentially from ethylene / vinyl acetate / alkyl acrylate terpolymers and even more preferentially 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 either one of Claims 1 and 9, 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 fatty acid methyl esters and fatty acid ethyl esters; 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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