Fuel composition comprising a renewable base and a compound containing a TEMPO group

Abstract

The present invention relates to a fuel composition comprising at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins and obtained from a hydrotreating process of fatty acids and / or fatty acid esters, a Fischer-Tropsch process, or a process for producing fuel bases from alcohols, and at least 0.05% by mass of one or more compounds comprising in their structure a 2,2,6,6-tetramethylpiperidinyl-1-oxyl group (TEMPO group). This composition is useful for powering any internal combustion engine of a land, marine, aerial, or space vehicle, and in particular an aircraft or rocket engine.

Description

Title of the invention: Fuel composition comprising a renewable base and a compound containing a TEMPO group

[0001] The present invention relates to a fuel composition usable inter alia in air transport, and which comprises one or more renewable paraffinic bases in association with at least one compound comprising a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group (or TEMPO group).

[0002] The present invention also relates to the use of such a composition to power a heat engine, such as, in particular but not limited to, an aircraft or rocket engine. PREVIOUS STATE OF THE ART

[0003] Fuels used in aeronautics and space propulsion are subject to very strict regulations which aim to guarantee a high level of safety during their use.

[0004] Thus, turbine engines (turbojets and turboprops) which equip the majority of airplanes and helicopters (civilian or military) use specific fuels called jet fuels, which are traditionally formulated from hydrocarbon cuts called kerosene cuts from the distillation of crude oils.

[0005] The reference jet fuel for civil aviation and the most widely used is Jet Al. Its properties are defined in the international standard ASTM D1655. The physical characteristics of this fuel meet the efficiency and safety criteria required in the field of air transport, whether for ground operations or flight phases. The main properties are: - A high calorific value, of at least 42.8 MJ / kg. This represents the amount of energy released per unit mass of fuel during its combustion. This value is directly related to the aircraft's range for a constant mass of fuel carried. - A very low freezing point, which must be below -47°C, which allows the fuel to remain in a liquid state when the aircraft is in cruise flight, in a very low temperature environment. - A flash point (or temperature above which fuel vapors can ignite in the presence of a flame), which must be above 38°C, in order to ensure safe handling of fuel on the ground.

[0006] Other properties such as sulfur content, acidity or fuel density are also defined in ASTM DI655.

[0007] The fight against climate change now requires air transport to reduce its fossil fuel carbon dioxide emissions by adopting fuels with a low environmental impact, also known as sustainable aviation fuels or SAFs. A promising solution is to replace fossil fuel-based kerosene with renewable bases, such as bases derived from the hydroprocessing of natural esters and fatty acids (HEFAs); bases from the Fischer-Tropsch process; or bases from a fuel base production process using alcohols. Indeed, fuels formulated from these bases have characteristics relatively close to Jet Al jet fuel, making HEFAs excellent candidates for the aeronautical industry.

[0008] However, these renewable bases are essentially made up of linear and branched paraffins (alkanes). Their chemical composition, devoid of aromatic and naphthenic hydrocarbons, gives them a significantly lower auto-ignition temperature than traditional jet fuels based on fossil-derived kerosene, which leads to significant safety problems, particularly fire risks when using the fuel in the hot parts of aircraft and rocket engines.

[0009] It is therefore desirable to increase the auto-ignition temperature of this type of biofuel, in particular to enable their use in the aeronautical and aerospace industries.

[0010] One solution to this problem is to add one or more fuel bases rich in aromatic and / or naphthenic hydrocarbons to the renewable paraffinic bases. However, the available aromatic and / or naphthenic fuel bases most often come from fossil sources, which are not renewable. Furthermore, these bases are available in small quantities, are expensive, and require high incorporation rates to have a significant effect on the auto-ignition temperature.

[0011] Furthermore, due to their different chemical composition compared to fossil-based kerosene, renewable fuel bases also present compatibility issues with certain materials used in the components with which the fuel comes into contact. This stems from the fact that these bases are primarily composed of paraffins. They thus pose problems for their use in current aircraft, particularly related to their poor compatibility with the materials used in the seals employed in fuel systems. One possible solution to this problem is to add an aromatic base to the paraffinic base. (Article - Kramer S, Andac G, Heyne J, Ellsworth J, Herzig P and Lewis KC (2022) Perspectives on Fully) Synthesized Sustainable Aviation Fuels: Direction and Opportunities. Front. Energy Res. 9:782823. doi:10.3389 / fenrg.2021.782823 - thus presents the likely production pathways for so-called "100% drop-in" SAFs, by blending paraffinic and aromatic bases. However, even if aromatic compounds improve the fuel's compatibility with aircraft seals, they can have a negative impact on combustion emissions, for example, on the formation of fine particles and the presence of contrails.

[0012] The present invention aims to remedy the problems described above.

[0013] The present invention thus aims to propose new jet fuel compositions formulated from renewable bases, exhibiting improved combustion quality compared to existing jet fuel compositions, while preserving, or even improving at least one of their properties chosen from among their auto-ignition temperature, their compatibility with materials, in particular those constituting aeronautical seals, and their environmental impact.

[0014] The present invention aims in particular to propose a fuel composition comprising such renewable bases, which has an increased auto-ignition temperature without resorting to bases rich in aromatic and / or naphthenic hydrocarbons in large quantities.

[0015] The Applicant has now discovered that the addition, to a renewable paraffinic fuel base, of one or more compounds chosen from 2,2,6,6-tetramethylpiperidinyl-l-oxyl and its derivatives as defined below, in a minimum content of 0.05% by mass, made it possible to significantly increase the auto-ignition temperature of the mixture while exhibiting good compatibility with the materials used in parts in contact with jet fuels, and thus to formulate a sustainable fuel suitable for use in the aeronautical and aerospace industries.

[0016] The present invention thus relates to a fuel composition comprising: a) at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and obtained from a process of hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process of producing fuel bases from alcohols; and b) at least 0.05% by mass, relative to the total mass of the composition, of one or more compounds comprising in their structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group (TEMPO group).

[0017] The composition according to the invention has an auto-ignition temperature, measured in accordance with ASTM E659, significantly higher than a composition comprising the same bases except for compound(s) (b) comprising a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group.

[0018] Thus, said compounds can be used to increase the auto-ignition temperature of a fuel composition, in particular a fuel composition for powering aircraft and rocket engines.

[0019] This increase in the auto-ignition temperature results in a reduction of the risk of fire when using the composition as fuel, including at high temperatures such as those found in aircraft and rocket engines. This reduction in fire risk advantageously increases the safety of the internal combustion engine, particularly the safety of aircraft and rocket engines.

[0020] While the auto-ignition temperature measured according to ASTM E659 for a fuel composition consisting solely of renewable paraffinic bases is sometimes less than 200°C, the auto-ignition temperature (measured according to the same standard) of the composition according to the invention is at least 200°C. Preferably, the auto-ignition temperature of the composition according to the invention is greater than or equal to 210°C and more preferably greater than or equal to 220°C.

[0021] This temperature is reached without having to add significant quantities of fuel bases rich in aromatic and / or naphthenic hydrocarbons.

[0022] Thus, according to a preferred embodiment, the aromatic hydrocarbon content of the composition according to the invention is less than 5% by mass, preferably less than 2% by mass, more preferably less than 1% by mass, relative to the total mass of the composition.

[0023] According to an also preferred embodiment, the naphthenic hydrocarbon (i.e. cycloalkane) content of the composition according to the invention is less than 5% by mass, relative to the total mass of the composition.

[0024] According to a particularly preferred embodiment, the total content of naphthenic hydrocarbons and aromatic hydrocarbons of the composition according to the invention is less than 5% by mass, preferably less than 4% by mass, relative to the total mass of the composition.

[0025] The composition according to the invention also exhibits excellent compatibility with the materials used in aircraft parts, and in particular with the constituent materials of sealing gaskets such as, for example, elastomers.

[0026] The base(s) a) used in the composition according to the invention are renewable bases that can advantageously be derived from biological matter. Thus, said composition comprises a majority of bio-based materials. It It therefore has a high eco-material content. The mass content of eco-material in the composition is defined by the following equation: Eco-material content in % = 100 - (percentage of non-bio-based, non-biodegradable, non-recycled materials).

[0027] According to an advantageous embodiment, the composition according to the invention has an eco-material content of at least 70% by mass, preferably at least 80% by mass, preferably at least 90% by mass, and more preferably at least 95% by mass, relative to the total mass of the composition.

[0028] The composition according to the invention also exhibits good properties in terms of calorific value, freezing point, flash point and cetane number.

[0029] It is perfectly suited for use as fuel to power aircraft and rocket engines, but also and more generally for powering any internal combustion engine used in propulsion, whether on land, sea, air or space.

[0030] Thus, the present invention also relates to the use of the composition according to the invention to power an internal combustion engine of a land, sea, air or space propulsion vehicle, and preferably an aircraft or rocket engine.

[0031] Other objects, features, aspects and advantages of the invention will become even clearer upon reading the description and examples that follow.

[0032] In what follows, and unless otherwise indicated, the bounds of a range of values ​​are included in that range, in particular in the expressions "between" and "ranging from ... to ...". 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". 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

[0033] The paraffinic hydrocarbon base (a) The fuel composition comprises at least 50% by mass, relative to the total mass of the composition, of one or more paraffinic hydrocarbon bases (a), also referred to hereinafter as bases (a), which are characterized in that: - they comprise at least 90% by mass of paraffins relative to the mass of said base; and - they are produced by a hydrotreating process of fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process for producing fuel bases from alcohols.

[0034] The paraffinic base(s) (a) used in the invention are advantageously derived from the transformation of raw materials of non-petroleum origin (i.e. non-fossil), and in particular from biological raw materials.

[0035] According to a first embodiment, the composition comprises at least one base (a) obtained from a hydrotreating process of fatty acids and / or fatty acid esters. In this embodiment, the base(s) (a), also referred to as the "HEFA" base, are selected from among the hydrotreated fatty acids and / or fatty acid esters.

[0036] As is known per se, the term HEFA (from the English Hydroprocessed Esters and Fatty Acids) designates a base obtained by hydrotreating fatty acids and / or fatty acid esters. The corresponding hydrotreating processes are well known and allow the transformation of fatty acids and fatty acid esters into paraffins by hydrogenation and hydrodeoxygenation. HEFA bases are thus essentially composed of linear and branched paraffins (alkanes).

[0037] By fatty acid, we mean a carboxylic acid comprising a 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.

[0038] By fatty acid ester, we mean both monoesters and polyesters (in particular di- and tri-esters) of the above fatty acids with an alcohol which may be a monoalcohol or a polyol.

[0039] Fatty acids and fatty acid esters can come from many sources, including vegetable oils and fats, animal oils and fats, recycled oils (e.g., edible oils, cooking oils).

[0040] HEFA-type bases (a) can in particular be produced from naturally sourced oil(s) by a process comprising hydrogenation and deoxygenation of fatty acid esters and free fatty acids, optionally followed by one or more subsequent treatments such as, for example, hydrocracking, hydroisomerization, isomerization, and possibly including other conventional processing steps. In other words, renewable HEFA paraffinic bases are produced by processes including hydrotreating esters and fatty acids contained in naturally sourced oil.

[0041] A naturally sourced oil is defined as an oil of biomass origin and containing no mineral oil. In this description, the expression "naturally sourced oil(s)" refers indiscriminately to oils, fats, and mixtures thereof. The naturally sourced oil(s) may contain one or more oils selected from among vegetable oils, animal fats, and preferably oils highly saturated inedible oils, used oils, by-products of refining vegetable or animal oil(s) containing free fatty acids, tall oil and oils produced by bacteria, yeasts, algae, prokaryotes or eukaryotes.

[0042] Suitable vegetable oils include, for example, palm oil, palm kernel oil, soybean oil, rapeseed (canola) oil, sunflower oil, linseed oil, bran oil, rice oil, corn oil, olive oil, castor oil, sesame oil, pine oil, peanut oil, mustard oil, carinata oil, hemp oil, coconut oil, babassu oil, cottonseed oil, linola oil, and jatropha oil. Animal fats include tallow, lard, fat (yellow and brown), fish oil / fat, fat, and milk fats.

[0043] By-products of vegetable or animal oil refining are by-products containing free fatty acids that are removed from crude fats and oils by neutralization or vacuum or steam distillation. A typical example is known as PF AD (from the English "Palm Fatty Acid Distillate").

[0044] Used oils include used cooking oils (used food oils) and oils recovered from wastewater, such as grease / drain oil, gutter oil, sewage oil, for example from wastewater treatment plants, and used grease from the food industry.

[0045] Tall oil, including crude tall oil, distilled tall oil (DTO), and tall oil fatty acids (TOFA), preferably DTO and TOFA, can also be used in the present invention. Tall oil, also known as tallol, is a liquid by-product of the Kraft wood processing method, used to isolate wood pulp, which is useful in the paper industry. Tall oil is essentially obtained when conifers are used in the Kraft process. After treating the wood chips with sodium sulfide in aqueous solution, the isolated tall oil is alkaline. This is then acidified with sulfuric acid to produce crude tall oil.

[0046] The oil(s) of natural origin also include oils produced by microorganisms, whether natural or genetically modified, such as bacteria, yeasts, algae, prokaryotes, or eukaryotes. In particular, such oils can be recovered by well-known mechanical or chemical extraction methods.

[0047] In said first embodiment, the base(s) (a) may advantageously include one or more bases selected from hydrotreated vegetable oils, also known as HVOs (from the English "hydrotreated vegetable oils"). These are oils of vegetable origin that have undergone successive treatments including hydrotreatment and possible isomerization. The processes for preparing such hydrotreated vegetable oils are also known.

[0048] Non-limiting examples of preferred vegetable raw materials include rapeseed oil, canola oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, castor oil, coconut oil.

[0049] According to a second embodiment, the composition comprises at least one base (a) from a Fischer-Tropsch process, which is a well-known process for the synthesis of hydrocarbons from synthesis gas containing carbon monoxide (CO) and hydrogen (H2).

[0050] In this embodiment, the base (a) is advantageously produced from solid biomass. The thermochemical conversion of biomass (gasification and Fisher-Tropsch synthesis), also called BtL (Biomass to Liquid), comprises the following steps: conditioning of the biomass (preparation, crushing, torrefaction), gasification of the biomass (obtaining a synthesis gas), purification of the synthesis gas, Fisher-Tropsch synthesis to transform the gas into synthetic biofuel.

[0051] According to a third embodiment, the composition comprises at least one base (a) obtained from a process for producing fuel bases from alcohols. Such a process is also well known.

[0052] The starting alcohol(s) can be chosen from monoalcohols containing from 1 to 6 carbon atoms.

[0053] The production process includes a dehydration step of the alcohol(s) to produce the corresponding olefins, then an oligomerization step of the olefins to obtain unsaturated hydrocarbons, and finally a hydrogenation step of the unsaturated hydrocarbons to produce the paraffinic base.

[0054] The first embodiment is preferred.

[0055] Regardless of the embodiment, the paraffinic hydrocarbon base (a) may also have undergone an isomerization step and / or a distillation step before its incorporation into the composition according to the invention.

[0056] Generally, the paraffinic hydrocarbon base(s) (a) have a distillation range at atmospheric pressure advantageously within the range of 60 to 350°C, preferably 100 to 300°C, more preferably 120 to 290°C, and even better 140 to 280°C. The distillation range of said cut is determined in accordance with standard NF EN ISO 3405.

[0057] The paraffinic hydrocarbon base(s) (a) contain paraffins in a significant amount. Their paraffin content is greater than or equal to 90% by mass, preferably greater than or equal to 95% by mass, relative to the total mass of the base(s) (a).

[0058] By "paraffins" is meant, in a manner known per se, branched alkanes (also called iso-paraffins or iso-alkanes) and unbranched alkanes (also called n-paraffins or n-alkanes).

[0059] The paraffins present in the base(s) (a) according to the invention advantageously comprise from 6 to 18 carbon atoms, preferably from 8 to 18 carbon atoms. Preferably, the paraffinic hydrocarbon base(s) (a) are composed of at least 80% by mass, more preferably at least 90% by mass, and even better at least 95% by mass, of paraffins comprising from 8 to 18 carbon atoms.

[0060] According to a preferred embodiment, the paraffinic hydrocarbon base(s) (a) used in the composition according to the invention contain at least 60% by mass, preferably at least 70% by mass, of isoparaffins, relative to the total mass of the cut(s) (a). According to a particularly preferred embodiment, they contain at least 80% by mass of isoparaffins.

[0061] The paraffinic hydrocarbon base(s) (a) have an aromatic compound content preferably less than or equal to 10000 ppm by mass, more preferably less than or equal to 1500 ppm by mass, even more preferably less than or equal to 1000 ppm by mass.

[0062] Their naphthenic compound content is preferably less than or equal to 50000 ppm by mass.

[0063] Their sulfur content is advantageously less than or equal to 10 ppm by mass, preferably less than or equal to 5 ppm by mass. Particularly preferred, the paraffinic hydrocarbon base(s) (a) are totally sulfur-free.

[0064] The composition according to the invention preferably comprises at least 75% by mass of one or more paraffinic hydrocarbon bases (a) as described above. Preferably, it contains at least 85% by mass of one or more bases (a), more preferably at least 90% by mass and even better at least 95% by mass, relative to the total mass of the composition.

[0065] According to a preferred embodiment, the composition according to the invention contains at least 95% by mass, preferably at least 98% by mass, and even better at least 99% by mass of one or more bases (a) as described above.

[0066] Compounds £ b) comprising a TEMPO group The composition according to the invention comprises one or more compounds comprising in their structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group.

[0067] 2,2,6,6-tetramethylpiperidinyl-l-oxyl is a known compound, also referred to as 2,2,6,6-tetramethylpiperidin-l-yl)oxy or (2,2,6,6-tetramethylpiperidin-l-yl)oxyl or TEMPO.

[0068] This compound has the following structural formula: H3cJ^^CH3 h3c 'nt xh3 ô*

[0069] This is a stable radical at room temperature, which can be prepared in a manner also known by oxidation of 2,2,6,6-tetramethylpiperidine.

[0070] Preferably, compound(s) (b) are chosen from the compounds of formula (I) below: in which the groups Rb R2 and R3, identical or different, independently designate a hydrogen atom; an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms; a group of formula -ORa or -OCORa with Ra designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms; or a group of formula -NRbRc with Rb and Rc, identical or different, designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms.

[0071] Preferably, in formula (I) the groups RB R2 and R3, identical or different, independently designate a hydrogen atom; an alkyl group, linear or branched, comprising from 1 to 8 carbon atoms; a group of formula -ORa or -OCORa with Ra designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 8 carbon atoms; or a group of formula -NRbRc with Rb and Rc, identical or different, independently designate a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 8 carbon atoms.

[0072] Preferably, in formula (I), the groups Rb R2 and R3, identical or different, independently designate a hydrogen atom; an alkyl group, linear or branched, comprising from 1 to 4 carbon atoms; a group of formula -ORa or -OCORa with Ra designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 4 carbon atoms; or a group of formula -NRbRc with Rb and Rc, identical or different, independently designating from each other a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 4 carbon atoms.

[0073] Preferably, in formula (I) the Riet R3 groups, identical or different, denote: - a hydrogen atom; or - an alkyl group, linear or branched, comprising from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, more preferably from 1 to 4 carbon atoms, and even better an alkyl group selected from the methyl and ethyl groups.

[0074] Preferably, in formula (I) the group R2 designates: - a hydrogen atom; or - a group of formula -ORa or -OCORa with Ra denoting a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms, preferably 1 to 12 carbon atoms; more preferably from 1 to 8 carbon atoms, better still from 1 to 4 carbon atoms, and better still a methyl or ethyl group; or - a group of formula -NRbRc with Rb and Rc, identical or different, designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms, preferably 1 to 12 carbon atoms; more preferably from 1 to 8 carbon atoms, better still from 1 to 4 carbon atoms and better still a methyl or ethyl group.

[0075] According to a preferred embodiment, R2 designates a hydrogen atom, a hydroxyl group -OH or an amino group -NH2.

[0076] Particularly preferred compounds are 2,2,6,6-tetramethylpiperidinyl-l-oxyl (TEMPO) and 4-amino-2,2,6,6-tetramethylpiperidinyl-l-oxyl (4-amino-TEMPO), which have the following respective structural formulas: TEMPO 4-amino-TEMPO.

[0077] 4-amino-2,2,6,6-tetramethylpiperidinyl-l-oxyl (4-amino-TEMPO) is particularly preferred.

[0078] The composition according to the invention advantageously comprises the compound or compounds (b) comprising in their structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group in a total content of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, more preferably 0.3 to 3% by mass, better 0.5 to 2% by mass and better still 0.5 to 1% by mass or 1 to 2% by mass, relative to the total mass of the composition.

[0079] According to a preferred embodiment, the composition according to the invention comprises at least one compound of formula (I) as described above, preferably at least one compound selected from TEMPO and 4-amino-TEMPO, in a total content of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, more preferably 0.3 to 3% by mass, better 0.5 to 2% by mass and better still 0.5 to 1% by mass or 1 to 2% by mass, relative to the total mass of the composition.

[0080] According to a particularly preferred embodiment, the composition according to the invention comprises 4-amino-TEMPO in a content ranging from 0.05 to 10% by mass, preferably from 0.1 to 5% by mass, more preferably from 0.3 to 3% by mass, better from 0.5 to 2% by mass and better still from 0.5 to 1% by mass, relative to the total mass of the composition.

[0081] The compounds (b) comprising a TEMPO group are present in the composition according to the invention in radical form, as described above. This form can be obtained by using, to prepare the composition, either compound (b) in radical form or a precursor of compound (b), that is to say, a compound which in the composition can be dissociated so as to release the radical form.

[0082] Non-limiting examples of such precursors of compounds (b) comprising a TEMPO group are the compounds with the following structural formula (II): in which the Rb groups R2 and R3 are as defined for formula (I) above.

[0083] In a manner known per se, the dissociation of the compounds of formula (II) into compounds of formula (I) can be carried out according to the following synthetic reaction scheme:

[0084] Any possible additives The composition according to the invention may further comprise one or more additives, different from the compounds (b) described above.

[0085] This additive or these additives may be chosen, for example, but not limited to, antioxidants, antifreeze, antistatic, corrosion inhibitors, lubricants, cold-weather additives, detergents, and tracer additives. Antioxidant additives are particularly preferred.

[0086] These additives can be incorporated at levels, for each one, ranging from a few ppm to 1000 ppm by mass.

[0087] The use of the composition The composition according to the invention is useful as fuel to power any internal combustion engine of a propulsion device, in particular for land, sea, air or space propulsion.

[0088] The composition according to the invention can in particular be used to power any internal combustion engine in one of the following vehicles: road vehicles including light vehicles (in particular automobiles) and heavy goods vehicles (trucks of different loads known as "medium duty" and "heavy duty", garbage trucks, buses, coaches...) and non-road vehicles (construction or public works equipment, tractors, trains, boats).

[0089] According to a preferred embodiment, the composition according to the invention is used to power an aircraft or rocket engine.

[0090] According to a particularly preferred embodiment, the composition according to the invention is used to power a turbojet or turboprop in an aircraft, preferably chosen from an airplane and a helicopter (civilian or military), and more preferably an airplane.

[0091] The composition according to the invention can also be used to improve the eco-performance of an internal combustion engine of a land, marine, air or space propulsion vehicle, in particular an aircraft engine or a rocket engine.

[0092] For example, the eco-performance of the internal combustion engine can be the reduction of the environmental impact of the internal combustion engine.

[0093] Indeed, the quantity of compounds of biological origin in the composition according to the invention is significant. As explained above, the quantity of fuel bases rich in aromatic and / or naphthenic hydrocarbons of fossil origin and the quantity of compound (b) comprising a TEMPO group in the composition according to the invention can be low. Thus, the environmental impact of the composition according to the invention is lower than the environmental impact of a fuel composition of fossil origin. The environmental impact of the internal combustion engine powered by the composition according to the invention is therefore reduced.

[0094] The use of compound ç (b) comprising a TEMPO group The present invention also relates to the use of at least one compound (b) comprising in its structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group or a precursor of such a compound to increase the auto-ignition temperature of a fuel composition comprising at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins (relative to the mass of said base) and obtained from a process of hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process of producing fuel bases from alcohols.

[0095] The auto-ignition temperature is measured in accordance with the method defined in ASTM E659.

[0096] The present invention also relates to the use of at least one compound (b) comprising in its structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group or a precursor of such a compound to increase the compatibility with elastomers of a fuel composition comprising at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins (relative to the mass of said base) and obtained from a process of hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process of producing fuel bases from alcohols.

[0097] By precursor of a compound (b) is meant any compound capable of releasing the radical form 2,2,6,6-tetramethylpiperidinyl-l-oxyl (TEMPO form).

[0098] Said compounds (b), said bases (a) and the fuel composition are as described above.

[0099] In particular, the compounds (b) are advantageously chosen from the compounds of formula (I) described above and their precursors from the compounds of formula (II) described above.

[0100] The compound(s) (b) and their precursors are advantageously used in a content ranging from 0.05 to 10% by mass, preferably from 0.1 to 5% by mass, plus preferably from 0.3 to 3% by mass, better from 0.5 to 2% by mass and better still from 0.5 to 1% by mass or from 1 to 2% by mass, relative to the total mass of the composition.

[0101] The method The present invention also relates to a method of propulsion of a land, sea, air or space vehicle equipped with at least one internal combustion engine, consisting of supplying said engine with a fuel composition as described above.

[0102] Preferably, said engine is an aircraft or rocket engine, more preferably a turbojet or turboprop engine equipping an airplane or a helicopter and more preferably an airplane.

[0103] The following examples are given as an illustration of the invention, and should not be interpreted in such a way as to limit its scope.

[0104] EXAMPLES The following examples were prepared from a paraffinic hydrocarbon fraction designated fraction A, consisting of hydrotreated esters and fatty acids (HEFA). More specifically, fraction A consists of a hydrotreated vegetable oil (HVO) whose characteristics are detailed in Table I below:

[0105] Compounds Mass Concentration (%) C8-C16 N-paraffins 14.56 C8-C17 Isoparaffins 80.50 Naphthenes 4.76 Aromatics 0.00

[0106] Comparative Examples 1 Fuel compositions were prepared by adding an aromatic compound (mesitylene) or a naphthenic compound (methylcyclohexane) to cut A, in the contents detailed in Table II below.

[0107] The auto-ignition temperature (hereinafter referred to as AIT) of each of these compositions was measured, in accordance with the method defined in ASTM E659. The parameter A AIT corresponds to the difference between the auto-ignition temperature of each composition and that of the reference composition ECO.

[0108] The results obtained are also detailed in Table II below.

[0109] Compositions ECO EC1 EC2 EC3 Content in cup A (% by mass) 100 89 90 99.5 Mesitylene content - 11 - - (% by mass) Methylcyclohexane content (% by mass) - - 10 0.5 TAI (°C) 196 212 215 200 A TAI (°C) 0 16 19 4

[0110] These results show that to significantly increase the auto-ignition temperature of cup A, the aromatic compound and the naphthenic compound must be added in high quantities, as is the case in the comparative compositions EC1 and EC2. In contrast, the addition of 0.5% naphthenic compound (composition EC3) provides a very moderate increase in the auto-ignition temperature. Examples 2 according to the invention [YES] 2.1. First series

[0112] Fuel compositions were prepared by adding 2,2,6,6-tetramethylpiperidinyl-l-oxyl (TEMPO) to cut A, in the contents detailed in Table III below.

[0113] The auto-ignition temperature of each of these compositions was measured, in accordance with the method defined in ASTM E659. The results obtained are also detailed in Table III. Compositions ECO Cl C2 C3 C4 Content in cut A (% by mass) 100 99.90 99.64 99.16 98.34 Content in TEMPO (% by mass) - 0.1 0.36 0.84 1.66 TAI (°C) 196 205 215 215 220 A TAI (°C) 0 9 19 19 24

[0115] The ECO composition is comparative (consisting entirely of the A cut), while the Cl to C4 compositions conform to the invention.

[0116] These results show that adding the compound according to the invention to section A in small quantities increases the auto-ignition temperature. The auto-ignition temperature increases significantly with the TEMPO content.

[0117] Compared to the addition of aromatic and naphthenic compounds according to comparative examples EC1 and EC2, the addition of compound TEMPO according to the invention allows for better results or equivalent results at much lower concentrations.

[0118] Compared to the addition of the naphthenic compound according to comparative example EC3, said compound in the same concentrations makes it possible to obtain a very significant increase in the auto-ignition temperature of the fuel composition.

[0119] 2.2. Second series

[0120] Fuel compositions C'1 and C'2 according to the invention were prepared by adding 4-amino-2,2,6,6-tetramethylpiperidinyl-l-oxyl (4-amino-TEMPO) to cut A, in the contents detailed in Table IV below.

[0121] The auto-ignition temperature of each of these compositions was measured, in accordance with the method defined in ASTM E659. The results obtained are also detailed in Table III. Compositions ECO C'1 C'2 Content in cup A (% by mass) 100 99.60 99.18 Content of 4-amino-TE MPO (% by mass) - 0.4 0.82 TAI (°C) 196 220 225 A TAI (°C) 0 24 29

[0123] These results show that adding the compound according to the invention to cut A increases the auto-ignition temperature compared to the reference ECO composition. The auto-ignition temperature increases significantly with the 4-amino-TEMPO content, and excellent results are obtained at concentrations of 0.4 and 0.82% by mass (compositions C'1 and C'2).

[0124] Compared to the addition of aromatic and naphthenic compounds according to comparative examples EC1 and EC2, the addition of the compound according to the invention makes it possible to obtain better results or equivalent results at much lower levels.

[0125] Compared to the addition of the naphthenic compound according to comparative example EC3, said compound in the same concentrations makes it possible to obtain a very significant increase in the auto-ignition temperature of the fuel composition.

Claims

Demands

1. Fuel composition comprising: (a) at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins relative to the mass of said base and obtained by hydrotreating fatty acids and / or fatty acid esters, by Fischer-Tropsch or by producing fuel bases from alcohols; and (b) at least 0.05% by mass, relative to the total mass of the composition, of one or more compounds comprising in their structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group (TEMPO group).

2. Composition according to the preceding claim, characterized in that the base(s) (a) are selected from hydrotreated fatty acids and / or fatty acid esters (HEFA).

3. Composition according to any one of the preceding claims, characterized in that the paraffin content of the base(s) (a) is greater than or equal to 95% by mass, relative to the total mass of the base(s) (a).

4. Composition according to the preceding claim, characterized in that the paraffins present in the base(s) (a) comprise from 6 to 18 carbon atoms, preferably from 8 to 18 carbon atoms.

5. Composition according to any one of the preceding claims, characterized in that it comprises at least 75% by mass of one or more bases (a), preferably at least 85% by mass, more preferably at least 90% by mass and better still at least 95% by mass, relative to the total mass of the composition.

6. Composition according to any one of the preceding claims, characterized in that the compound(s) (b) are selected from the compounds of formula (I) below: (I) in which the groups RB R2 and R3, identical or different, independently designate a hydrogen atom; an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms; a group of formula -ORa or -OCORa with Ra designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms; or a group of formula -NRbRc with Rb and Rc, identical or different, designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms.

7. Composition according to the preceding claim, characterized in that in formula (I), the Riet R3 groups, identical or different, denote: - a hydrogen atom; or - an alkyl group, linear or branched, comprising from 1 to 12 carbon atoms, preferably from 1 to 8 carbon atoms, more preferably from 1 to 4 carbon atoms, and even more preferably an alkyl group selected from the methyl and ethyl groups

8. Composition according to any one of claims 6 and 7, characterized in that in formula (I) the group R2 designates: - a hydrogen atom; or - a group of formula -ORa or -OCORa with Ra designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms, preferably from 1 to 12 carbon atoms; more preferably from 1 to 8 carbon atoms, better still from 1 to 4 carbon atoms and better still a methyl or ethyl group; or - a group of formula -NRbRc with Rb and Rc, identical or different, designating a hydrogen atom or an alkyl group, linear or branched, comprising from 1 to 16 carbon atoms, preferably from 1 to 12 carbon atoms; more preferably from 1 to 8 carbon atoms, better still from 1 to 4 carbon atoms and better still a methyl or ethyl group; and preferably, R2 designates a hydrogen atom, a hydroxyl group -OH or an amino group -NH2.

9. Composition according to any one of the preceding claims, characterized in that the compound(s) (b) are selected from the 2,2,6,6-tetramethylpiperidinyl-l-oxyl (TEMPO) and 4-amino-2,2,6,6-tetramethylpiperidinyl-1-oxyl (4-amino-TEMPO).

10. Composition according to any one of the preceding claims, characterized in that it comprises the compound(s) (b) in a total content of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, more preferably 0.3 to 3% by mass, better 0.5 to 2% by mass and better still 0.5 to 1% by mass or 1 to 2% by mass, relative to the total mass of the composition.

11. Composition according to any one of the preceding claims, characterized in that its aromatic hydrocarbon content is less than 5% by mass, preferably less than 2% by mass, more preferably less than 1% by mass, relative to the total mass of the composition.

12. Use of the composition as defined in any of the preceding claims to power an internal combustion engine of a land, sea, air or space propulsion vehicle.

13. Use according to the preceding claim, to power an aircraft or rocket engine, preferably a turbojet or turboprop in an aircraft selected from an airplane and a helicopter and more preferably an airplane.

14. Method of propulsion of a land, sea, air or space vehicle equipped with at least one internal combustion engine, consisting of supplying said engine with a fuel composition as defined in any one of claims 1 to 11.

15. Use of at least one compound (b) comprising in its structure a 2,2,6,6-tetramethylpiperidinyl-l-oxyl group as defined in any one of claims 1 and 6 to 9 or a precursor of such a compound for increasing the auto-ignition temperature of a fuel composition comprising at least 50% by mass, relative to the total mass of the composition, of at least one paraffinic hydrocarbon base comprising at least 90% by mass of paraffins and obtained from a process of hydrotreating fatty acids and / or fatty acid esters, a Fischer-Tropsch process or a process of producing fuel bases from alcohols.