Hydrocarbons for aviation

Abstract

The present invention relates to a kerosene base having particularly satisfactory cold properties and overall carbon yield. The present invention also relates to any composition comprising said kerosene base, the process for preparing same, and the use thereof as a fuel in the field of aviation.

Description

[0001] HYDROCARBONS FOR AVIATION

[0002] technical field

[0003] The present invention falls within the field of bio-based fuels and relates more particularly to a kerosene base, preferably renewable and meeting current specifications, notably those defined in ASTM D7566 and in particular in Annex 5. This kerosene base exhibits particularly satisfactory cold-weather properties and overall carbon efficiency. The present invention also relates to any composition comprising such a kerosene base.

[0004] Previous technique

[0005] Airlines have committed to carbon-neutral growth, particularly in commercial aviation, starting in 2021, and US airlines have set a target of reducing CO2 emissions by 50% by 2050 compared to 2005 levels. However, improvements in aircraft and engine efficiency are not proving sufficient to achieve carbon neutrality. Sustainable aviation fuels (SAFs) are therefore critical to reaching this goal.

[0006] It therefore seems necessary to develop kerosenes that are at least partly bio-based and have properties at least equivalent to those of fossil kerosenes.

[0007] Thus, US patent 8,373,012 proposes a method for preparing renewable fuel mixtures, including the conversion of fermentative isobutanol into synthetic paraffinic kerosene (or Synthesized Paraffinic Kerosene, SPK, according to Anglo-Saxon terminology) which meet the specifications of ASTM D7566-10a, Annex 1, and therefore have in particular a cold point of no more than -40°C.

[0008] Application WO13085980 discloses a renewable kerosene fuel derived at least in part from biomass, comprising between 5 and 20 wt% isoparaffins and between 15 and 95 wt% naphthenes. More specifically, document WO13085980 describes a renewable kerosene fuel derived from biomass with a cold point of approximately -39°C, -40°C, or -70°C, and in particular a density at 15°C (i.e., 60°F) of between 819 and 839 kg / m³. 3(between 0.8192 g / cc and 0.8393 g / cc). Said kerosene fuel is derived from a fuel composition predominantly n-paraffinic (more than 40% by weight), comprising approximately 7% by weight of C9 compounds, 12% by weight of C10 compounds, 8% by weight of C11 compounds, 9% by weight of C12 compounds and approximately 11% of C14+ compounds, which corresponds to a C9+ mixture comprising approximately 35% by weight of C9 to C12 compounds.

[0009] Application WO2018224730 discloses a renewable kerosene fuel compound, in particular obtained by a Fischer-Tropsch process, comprising predominantly isoparaffins and typically predominantly C15 to C18 paraffins, with C15- paraffins (i.e., those containing fewer than 15 carbon atoms) present at a content of less than 20% by weight, a distillation range in particular between 145°C and 280°C, and a cold point of approximately -51°C. WO18224730 also discloses compositions comprising such a renewable kerosene component blended with kerosene of fossil origin (i.e., derived from petroleum) and having a cold point of less than or equal to -40°C, in particular ranging between approximately -53°C and approximately -55°C.

[0010] Application WO2021 / 099343 describes a hydrocarbon composition that can be produced from a renewable source and has properties that allow it to be used as aviation fuel. In particular, this composition has the following characteristics: a high density, between 768.0 and 772.0 kg / m³ 3 , a low cold point, equal to or less than -40°C and an average number of hydrocarbon carbon atoms in this composition between 14.3 and 15.1.

[0011] Application W02022 / 008534 describes renewable fuel products composed mainly of isoparaffins (at least 86.7% by weight) and comprising between 35.4 and 69.8% by weight of paraffins (n- and iso-paraffins) in C9-C12, i.e. comprising between 9 and 12 carbon atoms, in other words in C9, C10, C11 and C12. More specifically, document W02022 / 008534 describes a renewable kerosene component comprising 86.7% by weight of isoparaffins and compounds containing 69.8% by weight of C9-C12 paraffins (n- and isoparaffins), of which 33.5% by weight are C9 and C12 paraffins, 19.5% by weight are C10 paraffins, and 16.8% by weight are C11 paraffins, with a cold point of -54°C and a density of 750.7 kg / m³ 3 .

[0012] Application WO2023 / 194338 discloses kerosenes with good cold-weather properties. In particular, this document describes a kerosene base, preferably renewable, comprising at least 80% by weight of isoparaffins and having a very low cold point, less than or equal to -60°C. This kerosene base comprises at least 60.0% by weight of a mixture of C3n hydrocarbons and C4n hydrocarbons, where n is a natural number chosen between 3 and 4, and meets the specifications of ASTM D7566, Annex 5.

[0013] It is always worthwhile to offer products, especially kerosene-based products, with improved properties, particularly in terms of cold-weather performance and overall carbon efficiency.

[0014] Thus, the objective of the invention is to propose a kerosene base, at least partly bio-based, meeting the specifications in force, and in particular exhibiting excellent cold properties, notably with a cold point at least as low as or even below that of prior art kerosenes, and a good overall carbon yield at least as good as or even better than that of prior art kerosenes, while maintaining a high density, preferably conforming to the specifications.

[0015] Summary of the invention

[0016] Thus, the present invention relates to a kerosene base having:

[0017] - a cut-off temperature T10 (°C) between 155 and 180 °C, a cut-off temperature T90 (°C) between 220 and 260 °C and a final boiling point below 300 °C,

[0018] - a cold point below -50°C, preferably below -60°C and most preferably below -70°C

[0019] - a density at 15°C between 768.0 and 780.0 kg / m³ 3 , And

[0020] - an average number of carbon atoms between 10.3 and 14.0.

[0021] The kerosene base according to the invention has the advantage of meeting the specifications of ASTM D7566, Annex 5, and in particular of exhibiting very good cold-weather properties, namely a cold point below -50°C, preferably below -60°C and most preferably below -70°C, and relatively low boiling points T10 and T90, while maintaining a density at 15°C between 768.0 and 780.0 kg / m³ 3 .

[0022] The present invention also has the advantage of helping airlines reduce their carbon footprint, resulting in better overall carbon efficiency and a reduction in CO2 emissions. Indeed, the kerosene base, characterized by a low average number of carbon atoms, in particular between 10.3 and 14.0, is advantageously at least partially bio-based.

[0023] The present invention also relates to a composition comprising a kerosene base according to the invention, its preparation process which includes mixing a kerosene base according to the invention with at least one kerosene product other than said kerosene base, and its use as fuel for aviation engines.

[0024] Description of the implementation methods

[0025] According to the present invention, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included within the described range of values. If this is not the case and the limit values ​​are not included within the described range, such clarification will be provided by the present invention.

[0026] In the sense of the present invention, the different parameter ranges given for the various characteristics can be used alone or in combination.

[0027] In the following, specific embodiments of the invention may be described. They may be implemented separately or in combination, without limitation as to the number of combinations, when technically feasible. The term "bio-based" means that the product / compound it describes is an organic product / compound whose carbon originates from CO2 present in the atmosphere, recently fixed (on a human timescale) through solar energy (photosynthesis). On land, this CO2 is captured or fixed by plant life (for example, agricultural crops or forest materials). In the oceans, CO2 is captured or fixed by photosynthetic bacteria or phytoplankton. For example, a bio-based material has an isotopic ratio 14 C / 12 C greater than 0. Conversely, a material of fossil origin has an isotopic ratio 14 C / 12C of approximately 0. The terms "renewable" or "derived from renewables" can also be used. To determine whether a product / compound is bio-based or derived from renewables, its modern carbon content (or percent modern carbon, pMC) is measured according to ASTM D 6866-21 ("Determination of Bio-based Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis"). The method in this standard measures the isotope ratio. 14 C / 12 C in a sample and compares it to the isotopic ratio 14 C / 12The bio-based content of a standard bio-based reference material is used to determine the percentage of bio-based content in the sample. This reference material provides a radiocarbon content approximately equivalent to the atmospheric radiocarbon fraction in 1950. The calculation of bio-based carbon content based on the bio-based reference material (pMC) is given in ASTM 6866-24 ("Determination of Bio-based Content of Solid, Liquid, and Gaseous Samples by Radiocarbon Analysis"). Thus, the bio-based carbon content of the standard bio-based reference material is 100%. The bio-based carbon content of a fossil-based material is approximately 0%. The bio-based carbon content of a bio-based material is strictly greater than 0%, for example, greater than or equal to 1%. A current bio-based material may therefore potentially have a bio-based carbon content of 100%.

[0028] In this description, the terms "T90" or "T90 temperature" are interchangeable and refer to the temperature at which 90% by weight of the product has evaporated. It is determined according to the ASTM D86 standard method. Similarly, "T10" or "T10 temperature" is the temperature at which 10% by weight of the product has evaporated, determined according to the same ASTM D86 standard method. Likewise, "T50" or "T50 temperature" refers to the temperature at which 50% by weight of the product has evaporated. This temperature is also determined according to the ASTM D86 standard method.

[0029] In this description, "Cx" refers to compounds containing x carbon atoms. For example, a C3 chemical compound contains 3 carbon atoms. "Cx+" refers to compounds with at least x carbon atoms. For example, C9+ compounds are compounds containing at least 9 carbon atoms (that is, 9 or more carbon atoms). "Cx-" refers to compounds with at most x carbon atoms.

[0030] According to the present invention, the terms "branched" and "branched" are synonymous and used interchangeably to characterize the hydrocarbon chain.

[0031] According to the present invention, the terms "olefin" and "mono-olefin" are used interchangeably and refer to hydrocarbons comprising a single double bond.

[0032] The freezing point of a substance defines a temperature at which the liquid and solid states of the substance can coexist in equilibrium (ASTM D5972 and / or D7153).

[0033] The flash point of a substance defines the temperature at which the vapors emitted by the substance ignite in the presence of an ignition source such as a flame. It is determined using a standardized apparatus according to ASTM D56 and / or D3828.

[0034] There is a relationship between overall carbon efficiency and the carbon chain length of the kerosene base. A low average number of carbon atoms indicates a high overall carbon efficiency. A high overall carbon efficiency of a kerosene base indicates that, when using that base, carbon is used efficiently and CO2 and co-product emissions are minimized.

[0035] Advantageously, the kerosene base comprises predominantly aliphatic hydrocarbon compounds, preferably predominantly non-cyclic and non-aromatic hydrocarbon compounds. Preferably, the kerosene base comprises at least 90% by weight, preferably at least 95% by weight, and preferably at least 99% by weight of aliphatic hydrocarbons, preferably linear and / or branched, and preferably non-cyclic, relative to the total weight of the kerosene base. Preferably, the kerosene base comprises less than 10% by weight, preferably less than 5% by weight, preferably less than 1.0% by weight, and very preferably less than 0.5% by weight of cyclic and / or aromatic hydrocarbon compounds, such as naphthenic, benzene, and / or naphthalene compounds, relative to the total weight of the kerosene base, and very preferably, the kerosene base is free of cyclic compounds.Preferably, the kerosene base comprises strictly less than 10% by weight of naphthenic compounds (also called cycloparaffins), preferably less than 5% by weight, preferably less than 1.0% by weight, most preferably less than 0.5% by weight relative to the total weight of the kerosene base, and most preferably is free of naphthenic compounds. This is because naphthenic compounds increase the density of the kerosene produced and have a higher carbon-to-hydrogen ratio (C / H) than paraffins.

[0036] Very advantageously, the kerosene base consists mainly of olefins and / or paraffins, that is to say at least 90% weight of olefins and / or paraffins relative to the total weight of the kerosene base.

[0037] Preferably, the kerosene base comprises predominantly hydrogenated aliphatic hydrocarbons, preferably linear and / or branched, called alkanes or paraffins, that is to say that the kerosene base preferably comprises at least 90% by weight, preferably at least 95% by weight, preferably at least 99% by weight of paraffins, that is to say of linear (or n-paraffins) and branched (or isoparaffins) paraffins relative to the total weight of the kerosene base.

[0038] The kerosene base may comprise at least 90% by weight of paraffins relative to the total weight of said kerosene base and may optionally comprise olefins, preferably at a weight content of less than 5% by weight, preferably less than 1.0% by weight, most preferably less than 0.5% by weight relative to the total weight of the kerosene base.

[0039] Preferably, the kerosene base according to the invention comprises at least 90%, preferably at least 95% by weight, preferably at least 97% by weight, and preferably at least 99% by weight of branched paraffins, relative to the total weight of paraffins in said kerosene base. Advantageously, the kerosene base comprises at least 20% by weight, preferably at least 25% by weight, and preferably at least 30% by weight of C10 isoparaffins, relative to the total weight of paraffins in said kerosene base.

[0040] Branched paraffins are paraffins containing at least one side chain, such as a methyl, ethyl, or propyl substituent. The average number of carbon atoms in a branched paraffin does not vary with the number and type of side chains.

[0041] Advantageously, branched paraffins, also called isoparaffins, are preferably multi-branched. Thus, preferably, the kerosene base comprises at least 40% by weight, preferably at least 50% by weight, and preferably at least 70% by weight of multi-branched paraffins relative to the total weight of said kerosene base. The term "multi-branched paraffins" means that said paraffins have a branching index greater than or equal to 2, and preferably less than or equal to 9, and most preferably less than or equal to 6.

[0042] Advantageously, the kerosene base comprises at most 10% by weight of linear paraffins, also called n-paraffins, preferably at most 5% by weight of linear paraffins, preferably at most 3% by weight of linear paraffins, and preferably at most 1% by weight of linear paraffins, relative to the total weight of said kerosene base. The kerosene base is advantageously at least partially, preferably entirely, bio-based. Preferably, the kerosene base according to the invention has a bio-based carbon content greater than or equal to 1%, preferably greater than or equal to 50%, preferably greater than or equal to 75%, preferably greater than or equal to 90%, or even equal to 100%. Preferably, the pMC is greater than or equal to 1, preferably greater than or equal to 50, preferably greater than or equal to 75, preferably greater than or equal to 90, or even equal to 100.

[0043] Preferably, the kerosene base described above is obtained by a process comprising an oligomerization step of olefins in C3 (containing 3 carbon atoms) to C8 (containing 8 carbon atoms), i.e. olefins comprising 3, 4, 5, 6 and / or 8 carbon atoms, preferably olefins in C3, C4 and / or C6, in the presence of an oligomerization catalyst, preferably heterogeneous, which may be followed by a hydrogenation step and optionally a separation (or fractionation) step to obtain said kerosene base.

[0044] The aforementioned C3, C4, C5, C6, and / or C8 olefins may advantageously be obtained from a process comprising the dehydration of at least one alcohol, in particular a monoalcohol from C1 to C6, preferably from C1, C2, and / or C3. These alcohols are preferably bio-based, for example, produced by the fermentation of sugars derived from sugar crops such as sugarcane, beets, or starchy plants, from lignocellulosic biomass, or from hydrolyzed cellulose, containing varying amounts of water. Alternatively, the alcohols may be obtained from synthesis gas. This dehydration may be followed by a first dimerization and / or trimerization step of the light olefins formed to obtain C3 to C6 olefins, which are then sent to the oligomerization step and possibly hydrogenation.A person skilled in the art will know how to adjust the temperature, pressure and feed flow rates, particularly according to the olefinic load and the nature of the oligomerization catalyst used. For example, the oligomerization step can be carried out in the presence of silica-alumina, used as an oligomerization catalyst, at a temperature between 20°C and 300°C, preferably between 25 and 220°C, preferably between 30°C and 200°C, a pressure between 1.5 and 6.5 MPa, preferably between 2.0 and 4.0 MPa, and a WH (volumetric flow rate per hour, corresponding to the volumetric flow rate of the olefinic load relative to the volume of catalyst in operation) between 0.1 and 0.5 h'. 1 preferably between 0.2 and 0.3 hours -1The person skilled in the art will also know how to adjust the operating conditions of the hydrogenation stage, for example at a temperature between 50 and 300°C, preferably between 60 and 200°C, a pressure between 0.5 and 5.0 MPa, preferably between 1.0 and 5.0 MPa, and preferably in the presence of hydrogen, preferably at a content between 0.5 and 3% weight relative to the weight of the effluent feeding the hydrogenation stage.

[0045] Furthermore, the kerosene base has an average number of carbon atoms between 10.3 and 14.0, preferably between 11.3 and 13.3, preferably between 11.3 and 12.8, and preferably between 11.3 and 12.4. The average number of carbon atoms in the kerosene base can be measured by any method known to those skilled in the art, such as a gas chromatography method (for example, flame ionization detection gas chromatography, the conditions of which are listed in Table 1, and in which the PONA-type column used has a length of 50 m, an internal diameter of 0.20 mm, a film thickness of 0.5 pm, and the stationary phase contains 100% dimethyl polysiloxane (OV-1)). A mass-weighted average of the number of carbon atoms in each compound identified by gas chromatography is then calculated to determine the average number of carbon atoms.

[0046] Table 1: Characteristics of the gas chromatography method with flame ionization detection

[0047] The average number of carbon atoms in the kerosene base according to the invention is low, thus improving the overall carbon yield of said kerosene base. A higher average number of carbon atoms, for example above 14, means that the overall carbon yield is low, with longer carbon chains and a lower volumetric yield.

[0048] Advantageously, the kerosene base comprises C10 hydrocarbons, preferably at least 30% by weight, preferably at least 40% by weight of C10 hydrocarbons relative to the total weight of said kerosene base.

[0049] Advantageously, the kerosene base according to the invention meets the specifications in force for kerosenes, particularly for aviation, and more particularly the specifications of ASTM D7566 and especially those defined in Annex 5 of ASTM D7566. And advantageously, the kerosene base exhibits excellent cold properties.

[0050] In particular, the kerosene base has a cut-off temperature T10 (°C) between 155 and 180°C, preferably between 160 and 175°C, and preferably between 160 and 165°C, and a cut-off temperature T90 (°C) between 220 and 260°C, preferably between 230 and 250°C, and preferably between 235 and 245°C. Preferably, the kerosene base has a cut-off temperature T50 (°C) between 170 and 195°C, preferably between 175 and 190°C.

[0051] Advantageously, the kerosene base according to the invention has an initial boiling point greater than or equal to 134°C.

[0052] The kerosene base has a final boiling point below 300°C.

[0053] Furthermore, the kerosene base according to the invention has a cold point below -50°C, preferably less than or equal to -60°C, and most preferably less than or equal to -70°C. The cold point is most advantageously less than or equal to -80°C.

[0054] Furthermore, the kerosene base has a density at 15°C of between 768.0 and 780.0 kg / m³ 3 , preferably between 768.0 and 775.0 kg / m 3 and preferably between 769.0 and 770.0 kg / m 3 The density of the kerosene base can be measured by any standardized method known to a person skilled in the art, such as ASTM D4052.

[0055] Furthermore, the kerosene base according to the invention has a flash point advantageously greater than 38°C and meets the specifications of ASTM D7566, Annex 5.

[0056] The kerosene base according to the invention, with in particular a low cold point and a low average number of carbon atoms, exhibits very good cold properties and a very satisfactory overall carbon yield.

[0057] The present invention also relates to any composition comprising the kerosene base described above, preferably a composition comprising at least 5% by weight of said kerosene base, preferably at least 10% by weight of the kerosene base, preferably at least 30% by weight of the kerosene base, most preferably at least 50% by weight of the kerosene base, and possibly preferably less than 90% by weight, preferably less than 60% by weight of the kerosene base, relative to the total weight of said composition. The said composition comprises, in addition to the kerosene base, one or more bio-based kerosene products different from the kerosene base according to the invention and / or one or more kerosene products of fossil origin (also called fossil kerosene product(s) or non-renewable kerosene product(s)), for example aromatic kerosene products.

[0058] The present invention also relates to a method for preparing such a composition, comprising mixing the kerosene base according to the invention with at least one kerosene product other than said kerosene base, in particular with a bio-based and / or fossil kerosene product, preferably in a proportion of the kerosene base of at least 5% by weight, preferably at least 10% by weight, most preferably at least 30% by weight, and most preferably at least 50% by weight, relative to the total weight of the composition. Advantageously, said method for preparing the composition also comprises all the steps for preparing the kerosene base according to the invention as described above, prior to mixing said kerosene base with said at least one kerosene product other than said kerosene base.

[0059] Such compositions and their preparation processes offer the advantage of being able to improve, in a simple and advantageous manner, the cold-weather properties of kerosene fuels, particularly those intended for aviation applications, while maintaining the other characteristics and properties of the kerosene within current specifications. Another advantage of these compositions lies in the fact that they have an average number of carbon atoms between 10.3 and 14.0, preferably between 11.3 and 13.3, preferably between 11.3 and 12.8, and preferably between 11.3 and 12.4, as well as a percentage of modern carbon (pMC) greater than or equal to 1, preferably greater than or equal to 10, preferably greater than or equal to 25, and in particular greater than or equal to 50.Thus, the prepared compositions, which include the kerosene base according to the invention, will be able to help airlines reduce their carbon footprint, achieving better overall carbon efficiency and the set CO2 emission reduction targets, in particular a 50% reduction in CO2 emissions by 2050 compared to 2005 levels, and thus achieving carbon neutrality.

[0060] The present invention also relates to the use of a composition as described above, as fuel for aviation engines, in particular as aviation fuel according to the Jet A1 standard. The following examples illustrate the invention, in particular specific embodiments of the invention, without limiting its scope.

[0061] Example of a kerosene base according to the invention: A bio-based kerosene base was produced by oligomerization of a bio-based olefin feedstock, followed by hydrogenation. The resulting hydrogenation effluent is then sent to a distillation fractionation section. At the end of this distillation fractionation section, a kerosene fraction is obtained.

[0062] The kerosene base is analyzed: its characteristics are presented in Table 2. The kerosene base comprises 95% by weight of branched paraffins relative to the total weight of paraffins in the kerosene base.

[0063] Table 2: Characteristics of the Kerosene Base. The kerosene base described above therefore meets the applicable specifications, particularly those defined in ASTM D7566-24 and specifically in Annex 5. In particular, it exhibits very good cold-weather properties, namely a cold point of -70°C, relatively low boiling points T10 and T90, while maintaining a density at 15°C of 770.0 kg / m³. 3 .

[0064] Furthermore, the average number of carbon atoms, at 11.52, is low. Therefore, the kerosene base exhibits excellent cold-weather properties and good overall carbon yield, while maintaining a density that meets specifications.

Claims

Demands 1. Kerosene base exhibiting: a cut-off temperature T10 (°C) between 155 and 180 °C, a cut-off temperature T90 (°C) between 220 and 260 °C, a final boiling point below 300 °C, a cold point below -50 °C, and a density at 15 °C between 768.0 and 780.0 kg / m³ 3 , and an average number of carbon atoms between 10.3 and 14.

0.

2. Kerosene base according to claim 1, having a cold point below -60°C, preferably less than or equal to -70°C.

3. Kerosene base according to claim 1 or 2, having a cutoff temperature T10 (°C) between 160 and 175 °C.

4. Kerosene base according to any one of the preceding claims, having a cutoff temperature T90 (°C) between 230 and 250°C.

5. Kerosene base according to any one of the preceding claims having an average number of carbon atoms between 11.3 and 13.3, preferably between 11.3 and 12.

8.

6. Kerosene base according to any one of the preceding claims comprising C10 hydrocarbons, preferably at least 30% by weight, preferably at least 40% by weight of C10 hydrocarbons relative to the total weight of said kerosene base.

7. Kerosene base according to any one of the preceding claims comprising at least 90% by weight of paraffins relative to the total weight of said kerosene base.

8. Kerosene base according to any one of the preceding claims, comprising at least 95% by weight, preferably at least 97% by weight, and preferably at least 99% by weight of branched paraffins, relative to the total weight of paraffins of said kerosene base.

9. Kerosene base according to any one of the preceding claims, comprising at least 40% by weight, preferably at least 50% by weight, preferably at least 70% by weight of multi-branch paraffins relative to the total weight of said kerosene base.

10. Kerosene base according to any one of the preceding claims, having a bio-based carbon content greater than or equal to 1%, preferably greater than or equal to 50%, preferably greater than or equal to 75%, preferably greater than or equal to 90%.

11. Kerosene base according to any one of the preceding claims, obtained by a process comprising a step of oligomerization of C3 to C8 olefins.

12. Composition comprising a kerosene base according to one of the preceding claims, preferably comprising at least 5% by weight of a kerosene base according to one of the preceding claims, relative to the total weight of said composition.

13. Composition according to the preceding claim, further comprising at least one bio-based kerosene product different from the kerosene base according to any one of claims 1 to 11 and / or at least one fossil kerosene product.

14. A method for preparing a composition according to any one of claims 12 and 13, comprising mixing a kerosene base according to any one of claims 1 to 11 with at least one kerosene product other than said kerosene base.

15. Use of a composition according to any one of claims 12 and 13, as fuel for aviation engines.

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