Process for producing aviation fuel comprising conversion into olefins by oligomerisation steps

Abstract

The present invention relates to a process for producing aviation fuel from a predominantly ethylene feedstock, the process comprising the following steps: a) a first step of oligomerising the feedstock and obtaining at least one first effluent comprising olefins having a number of carbon atoms that is greater than or equal to 4 (C4+), the first oligomerisation step being carried out in the presence of an oligomerisation catalyst; b) a second step of oligomerising at least some of the first effluent resulting from step a) and obtaining a second effluent comprising olefins having a number of carbon atoms that is greater than or equal to 9 (C9+), the second oligomerisation step being carried out in the presence of a heterogeneous catalyst, c) a step of hydrogenating at least some of the second effluent resulting from step b) to obtain a third effluent comprising at least 90% by weight of paraffins relative to the total weight of the hydrocarbon compounds of the third effluent.

Description

[0001] PROCESS FOR PRODUCING AVIATION FUEL COMPRISING CONVERSION INTO OLEFINS BY OLIGOMERIZATION STEPS

[0002] TECHNICAL FIELD

[0003] The present invention relates to a method for manufacturing fuel, in particular aviation fuel, comprising the conversion of light olefins into heavier olefins by oligomerization technologies.

[0004] PREVIOUS TECHNIQUE

[0005] Demand for Sustainable Aviation Fuels (SAF) is crucial for meeting aviation decarbonization commitments. To achieve the International Civil Aviation Organization's (ICAO) goal of carbon-neutral aviation growth by 2020, it is necessary to replace fossil-based kerosene with liquid fuels made from bio-based carbon. Global SAF production needs by 2050 are estimated at approximately 500 million tons per year.

[0006] In order to achieve this objective, it is necessary to mobilize different types of resources and therefore to develop different technological transformation solutions.

[0007] One known transformation route involves the conversion of alcohols derived from biomass. Documents FR2959750 and FR2959752 disclose processes for producing middle distillate-type hydrocarbon bases from an ethanol feedstock, including ethanol dehydration steps followed by two oligomerization steps. Patent US9840676, for its part, discloses a process for converting ethanol into diesel and / or kerosene by dehydration, conversion of the resulting ethylene to 1-hexene, and then di- or trimerization to obtain a mixture containing C12 hydrocarbon compounds.

[0008] More generally, there are many ways to produce light olefins. Controlled oligomerization of these light olefins allows the production of longer carbon chains that can then be used in the composition of naphtha, gasoline, kerosene, or diesel fuel.

[0009] Patent application WO2023194337A1 describes a process for preparing middle distillates from an olefinic feedstock, comprising: a) an oligomerization step fed with the olefinic feedstock, a first recycle and a second recycle, and operated in the presence of at least one oligomerization catalyst, to produce a reaction effluent comprising dimers, trimers and oligomers; b) a step of fractionating the reaction effluent into: - a light fraction comprising at least a portion of the unconverted olefinic feedstock; - an intermediate fraction comprising at least a portion of the dimers and trimers; and - a heavy fraction comprising the oligomers; c) a recycle step, comprising the preparation of a first recycle comprising at least a portion of the light fraction, and a second recycle comprising at least a portion of the intermediate fraction; and the transfer of the first recycle and the second recycle to step a);d) a hydrogenation step of at least part of the heavy fraction;

[0010] The applicant has demonstrated, in a surprising manner, that sending a feedstock consisting mainly of ethylene to a first oligomerization step (a), by controlling the operating conditions of said first oligomerization step, to enable the conversion of said feedstock into a stream of heavier olefins, in particular having a number of carbon atoms greater than or equal to 4 (C4 +), according to a particular ratio between olefins having 6 carbon atoms and olefins having 4 carbon atoms, then sending this heavier olefin stream to a second oligomerization stage b), makes it possible to increase the formation of olefinic compounds having 10 carbon atoms (C10) and to improve the production of aviation fuel and kerosene selectivity meeting current specifications and in particular the specifications of ASTM D7566 Annex 5, while maintaining a satisfactory, or even high, overall conversion of the starting olefinic charge.

[0011] Thus, feeding a second oligomerization stage, carried out in a heterogeneous phase, with an effluent including C4 and C6 olefins in a particular ratio between olefins with 6 carbon atoms and olefins with 4 carbon atoms, makes it possible to maximize the yields of olefins suitable for hydrogenation in order to increase the production of aviation fuel at the end of the process.

[0012] The objective of the present invention is therefore to improve existing processes for producing aviation fuel from a predominantly ethylenic feedstock, by optimizing selectivity towards the kerosene cut while maximizing kerosene yield.

[0013] SUMMARY OF THE INVENTION

[0014] The present invention relates to a process for producing aviation fuel from a feed comprising at least 90% by weight of ethylene relative to the total weight of the feed, said process comprising the following steps: a) a first oligomerization step of said feed and obtaining at least a first effluent comprising olefins having a number of carbon atoms greater than or equal to 4 (C4 +), wherein: said at least one first effluent comprises at least olefins having 4 carbon atoms and olefins having e carbon atoms, the weight ratio, expressed as a percentage, between olefins having 6 carbon atoms (C6) and the sum of olefins having 4 carbon atoms and olefins having 6 carbon atoms (C4 + C6) of said at least one first effluent is greater than 22.0%, olefins having a number of carbon atoms greater than or equal to 4 (C4+) of said at least one first effluent representing at least 90% by weight relative to the total weight of olefins contained in said at least one first effluent, said first oligomerization step being carried out in the presence of an oligomerization catalyst;b) a second oligomerization step of at least a portion of said at least a first effluent from step a) and obtaining a second effluent comprising compounds having a number of carbon atoms greater than or equal to 9 (C9+) and comprising at least 50% by weight of olefins having a number of carbon atoms greater than or equal to 9 (C9+) relative to the total weight of said effluent, said oligomerization step implementing an oligomerization phase in the presence of a heterogeneous catalyst comprising an amorphous or zeolitic support; c) a step c) of hydrogenation of at least a portion of the second effluent from step b) to obtain a third effluent comprising at least 90% by weight of paraffins relative to the total weight of hydrocarbon compounds of the third effluent.

[0015] Optionally, the process according to the invention may also include a step d) of fractionating the third effluent from step c) of hydrogenation to obtain at least one aviation fuel type cut.

[0016] The present invention proposes to carry out step a) of oligomerization, by controlling the operating conditions, so that the predominantly ethylenic charge is converted into an effluent comprising olefins having a number of carbon atoms greater than or equal to 4 (C4 + ), according to a weight ratio between olefins with 6 carbon atoms (C6) and the sum of olefins with 4 carbon atoms and olefins with 6 carbon atoms (C4 + C6) greater than 22.0%, thus optimizes selectivity towards kerosene cutting, while improving the kerosene yield of the process.

[0017] The present invention also relates to a kerosene base obtained by the process according to the invention, a composition comprising a kerosene base according to the invention, preferably comprising at least 5% by weight of a kerosene base according to the invention, relative to the total weight of said composition.

[0018] The present invention also relates to the use of a composition according to the invention as fuel for aircraft engines. LIST OF FIGURES

[0019] Figure 1 represents a particular embodiment of the process according to the invention. A feed 10 comprising at least 90% by weight of bio-based ethylene is sent to a first oligomerization step a) to produce an effluent 11 comprising a content of at least 90% by weight of compounds having a number of carbon atoms greater than or equal to 4 (C4+) relative to the total weight of olefins in this effluent. Effluent 11 comprises C4 and O6 olefins with a weight ratio, expressed as a percentage, between 6-carbon olefins (O6) and the sum of 4-carbon olefins and 6-carbon olefins (O4 + O6) greater than 22.0%, preferably greater than or equal to 24.0%, preferably greater than or equal to 28.0%, and preferably less than or equal to 50.0%, preferably less than or equal to 37.0% and very preferably less than or equal to 34.0%.

[0020] Optionally, this effluent is then fractionated (F a ) to obtain at least a fraction 12 comprising a content of at least 90% by weight of compounds having 2 or 3 carbon atoms relative to the total weight of olefins in that fraction, which is recycled upstream of the first oligomerization step a) (stream 12) and a fraction 13 comprising a content of at least 90% by weight of compounds having a number of carbon atoms greater than or equal to 4 (C4+) relative to the total weight of olefins in that fraction (stream 13).

[0021] Flow 11 (or optionally flow 13 in case of F splitting) a), is sent to a second heterogeneous oligomerization step b) to produce an effluent 14 comprising a maximum of 40% by weight of olefins having a carbon number greater than or equal to 9 (C9+), relative to the total weight of olefins contained in said effluent 14. Advantageously, the effluent 14 undergoes a fractionation step (F b ) to obtain at least:

[0022] - a fraction 15 comprising a content of at least 90% by weight of compounds having a number of carbon atoms less than or equal to 8 (C8-), relative to the total weight of said fraction, and

[0023] - a fraction 16 comprising compounds having a number of carbon atoms greater than or equal to 09 (09+) and comprising at least 50% by weight of olefins having a number of carbon atoms greater than or equal to 9 (09+) relative to the total weight of this fraction and constituting said second effluent.

[0024] At least part of fraction 15 is recycled at the input of the second oligomerization step b).

[0025] Effluent 16 from the fractionation step F b is sent to a step c) of olefin hydrogenation to produce an effluent 17 comprising a paraffin content of at least 90% by weight relative to the total weight of hydrocarbon compounds in that effluent and a purge 18 comprising unreacted hydrogen and lighter gases. The effluent 17 can be sent to a step d) of fractionation to produce a gas purge 19, a naphtha-type cut 20, an aviation fuel-type cut 21, and a diesel-type cut 22.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] 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.

[0028] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0029] In this description, "Cx" refers to hydrocarbon compounds containing x carbon atoms. "Cx+" refers to hydrocarbon compounds containing at least x carbon atoms. "Cx-" refers to hydrocarbon compounds containing at most x carbon atoms. "Cx to Cy" refers to hydrocarbon compounds having between x and y carbon atoms.

[0030] Throughout this text, chemical element groups are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIIIB according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification, and group IB according to the CAS classification corresponds to the metals in column 11 according to the new IUPAC classification.

[0031] In the following, specific embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation as to the number of combinations where technically feasible.

[0032] In this application, the term "include" is synonymous with (means the same as) "include" and "contain," and is inclusive or open-ended and does not exclude other unstated elements. It is understood that the term "include" includes the exclusive and closed term "consist."

[0033] In this application, the term "tonne / hr" means tonne per hour.

[0034] In this application, the term "residence time" means the average time required for a component to pass through the reaction system. In this application, the expression "predominantly ethylenic charge" means that the charge comprises at least 90% by weight, preferably at least 95% by weight, and preferably at least 98% by weight of ethylene relative to the total weight of the charge.

[0035] According to the present invention, the selectivity towards the kerosene cut is defined as the ratio between the weight quantity of kerosene produced and all the products from the process such as diesel.

[0036] According to the present invention, the kerosene process yield is defined as the ratio between the weight quantity of kerosene produced and the quantity of feed entering the process.

[0037] According to the description, the first oligomerization step, step a), can also be called the first oligomerization step; and thus the oligomerization of step a) can be called the first oligomerization. Similarly, according to the present description, the second oligomerization step, step b), can also be called the "second oligomerization step," and the oligomerization of step b) can be called the "second oligomerization."

[0038] The invention relates to a process for producing aviation fuel from a predominantly ethylenic feedstock, said process exhibiting improved selectivity compared to prior art processes. In particular, the applicant has shown that controlling the operating conditions in the first step a) of oligomerization, preferably in a homogeneous phase, can influence the selectivity towards the kerosene fraction.The applicant then demonstrated in a surprising manner that a weight ratio, expressed as a percentage, between olefins with 6 carbon atoms (C6) and the sum of olefins with 4 carbon atoms and olefins with 6 carbon atoms (C4 + C6) greater than 22.0%, preferably greater than or equal to 24.0%, preferably greater than or equal to 28.0%, and preferably less than or equal to 50.0%, preferably less than or equal to 37.0% and very preferably less than or equal to 34.0% in the effluent from said step a) of oligomerization, i.e. in the first effluent, made it possible to optimize the selectivity towards the kerosene cut, while preserving or even improving the kerosene yield of the aviation fuel production process.

[0039] Charge

[0040] According to the invention, the charge implemented in the process of the invention comprises at least 90%, preferably at least 95% and preferably at least 98% weight of ethylene relative to the total weight of the charge.

[0041] Advantageously, the charge comprises less than 5%, preferably less than 3% and preferably less than 2% by weight of hydrocarbon compounds, preferably olefinic compounds, having a number of carbon atoms greater than or equal to 3, relative to the total weight of hydrocarbon compounds present in the charge.

[0042] The charge may possibly include other compounds.

[0043] The olefin feedstock treated in the process according to the invention may advantageously undergo a pretreatment step before being sent to step a) of first oligomerization. Such a pretreatment step makes it possible to remove any compound that could cause poisoning of the oligomerization catalysts, in particular water, sulfur derivatives, basic nitrogen derivatives, and oxygenated compounds, using purification processes dedicated to the different impurities and well known to those skilled in the art.

[0044] In one particular embodiment, the feedstock used in the process of the invention, comprising at least 90% by weight of ethylene, may originate from a catalytic alcohol decomposition unit, preferably an ethanol catalytic decomposition unit. According to a preferred embodiment, the feedstock originates from an ethanol dehydration unit. Among ethanol dehydration processes, several technologies exist, such as the ETE route (Ethanol To Ethylene route).

[0045] Operating conditions and catalysts

[0046] Step a) of first oligomerization

[0047] The process according to the invention comprises a first oligomerization step of said predominantly ethylenic feedstock and obtaining at least one first effluent comprising at least 90% by weight of olefins having a number of carbon atoms greater than or equal to 4 (C4+), relative to the total weight of olefins contained in said first effluent. More particularly, said at least one first effluent comprises at least olefins having 4 carbon atoms and olefins having 6 carbon atoms.The weight ratio, expressed as a percentage, between 6-carbon olefins (C6) and the sum of 4-carbon and 6-carbon olefins (C4 + C6) present in said at least one first effluent is greater than 22.0%, preferably greater than or equal to 24.0%, preferably greater than or equal to 28.0%, and preferably less than or equal to 50.0%, preferably less than or equal to 37.0%, and most preferably less than or equal to 34.0%. This first oligomerization step (a) is carried out in the presence of an oligomerization catalyst.

[0048] Optionally, first oligomerization step a) includes a fractionation step into at least one fraction comprising a content of at least 90% by weight of compounds having 2 or 3 carbon atoms relative to the total weight of olefins in that fraction, said fraction being recycled to the input of first oligomerization step a).

[0049] In one embodiment, the first effluent from the first oligomerization step a) undergoes a fractionation step to obtain at least one fraction comprising a content of at least 95% by weight, preferably at least 98% by weight, preferably at least 99% by weight of compounds having 4 or more carbon atoms (C4+) relative to the total weight of this fraction, which is sent to the second oligomerization step b), and a fraction comprising a content of at least 90% by weight, preferably at least 95% by weight, preferably at least 98% by weight of compounds having between 2 and 3 carbon atoms relative to the total weight of this fraction, which is recycled upstream of the first oligomerization step a).

[0050] According to a particular embodiment of the invention, at least one first effluent from the first oligomerization step (a) is sent to step (b) without undergoing a fractionation step. This first effluent is then directly introduced into the second oligomerization step (b), without a prior separation step. This embodiment has the advantage of minimizing the number of process steps and reducing the number of equipment required and the cost of implementing the process.

[0051] Advantageously, said at least one first effluent from the first oligomerization step a) comprises less than 10% by weight, preferably less than 5% by weight, preferably less than 1% by weight, preferably less than 0.1% by weight of ethylene not having reacted in the first oligomerization step a), relative to the total weight of olefins contained in said first effluent.

[0052] Advantageously, the first oligomerization step (a) leads to the production of a first effluent comprising at least 90% by weight, preferably at least 95% by weight, and preferably at least 96% by weight, of olefins having a carbon number greater than or equal to 4 (C4+), relative to the total weight of olefins contained in said olefinic effluent. In particular, said first effluent is rich in olefinic hydrocarbons having a carbon number between 4 and 6, and in particular having 4 or 6 carbon atoms; in particular, it comprises at least 50% by weight, preferably at least 70% by weight, of olefins having a carbon number between 4 and 6, preferably C4 and C6 olefins, relative to the total weight of olefins contained in said first effluent. The said first effluent may include, preferably includes, also olefinic hydrocarbons having 8 or more carbon atoms (C8+).Advantageously, said first effluent comprises at least 90% by weight of olefins having a number of carbon atoms greater than or equal to 4 (C4+), relative to the total weight of olefins contained in said first effluent, excluding unconverted ethylene and propylene.

[0053] Optionally, the olefinic effluent from the first oligomerization step a) is separated into at least one olefinic hydrocarbon effluent comprising at least 95% by weight of compounds having a carbon number greater than or equal to 4 (C4+) relative to the total weight of this effluent and into at least one light olefinic hydrocarbon effluent comprising at least 90% by weight of compounds having a carbon number between 2 and 3 (light C2-C3 effluent) relative to the total weight of this effluent. Preferably, the light C2-C3 effluent from said optional separation is advantageously recycled upstream of the first oligomerization step a).

[0054] In addition to the majority presence of olefins having a number of carbon atoms greater than or equal to 4 (C4+), the olefinic effluent produced during the first oligomerization step a) also advantageously comprises 5% by weight or less, preferably 3% by weight or less, preferably 1% by weight or less, and, most preferably, 0.1% by weight or less, of C2 and C3 olefinic compounds, the percentages being expressed as percentages by weight relative to the total mass of olefins contained in the effluent produced.

[0055] The oligomerization catalyst used in step a) can be any oligomerization catalyst known to those skilled in the art. It can be in homogeneous form, i.e., the catalyst is soluble in the liquid phase composed of dissolved ethylene and its oligomerization products, or in heterogeneous, insoluble form arranged in a fixed-bed reactor.

[0056] According to a first embodiment, said first step a) of oligomerization of the process according to the invention is carried out in a fixed bed with a heterogeneous catalyst.

[0057] In this embodiment, the heterogeneous catalyst comprises at least one element from group VIII and at least one support.

[0058] The Group VIII element is preferably chosen from nickel, cobalt, iron, platinum, and palladium, and preferably, said Group VIII element is nickel. Nickel precursors may be nickel carbonate, nickel nitrate or nickel sulfate, nickel chloride, or nickel fluorosilicate. The heterogeneous catalyst may also include one or more additional elements chosen from Groups VI, IA, and HA. For example, the Group VI element is chosen from chromium, molybdenum, and tungsten. The Group IA element is chosen from lithium, sodium, or potassium, and the Group HA element includes magnesium, calcium, and strontium.The support is a porous refractory oxide support, preferably selected from alumina, silica, silica-alumina, zirconia, titanium oxide, magnesia, clays, alone or in mixtures, or a support comprising a zeolite, preferably aluminosilicate zeolites. Preferably, the porous refractory oxide support is alumina, silica, or silica-alumina. The support may, in particular, be an amorphous silica-alumina comprising between 70 and 99.5% by weight of SiC>2, with the remainder being alumina.

[0059] The heterogeneous catalyst is, for example, a catalyst such as that described in the journal "Chemical Reviews", Olivier-Bourbigou et al., 202, 120, 7919-7983, in particular a heterogeneous catalyst comprising:

[0060] - a nickel precursor such as nickel sulfate or nickel fluorosilicate deposited on alumina,

[0061] - a nickel precursor such as nickel carbonate or nickel nitrate, supported on silica,

[0062] - a nickel precursor such as nickel nitrate, supported by silica-alumina (SiO2,(Al(NC>3)3 or AhSCD. a nickel precursor such as nickel nitrate or nickel chloride and an aluminosilicate type zeolite.

[0063] In this first embodiment, said first step a) of oligomerization of the process, carried out in the presence of a heterogeneous catalyst, is advantageously performed at a temperature between 20 and 400°C, preferably between 30 and 250°C and preferably between 50 and 150°C, at an absolute pressure between 0.01 and 10 MPa, preferably between 1 and 10 MPa and preferably between 1 and 8 MPa, and at a weight hourly space velocity (WHSV), defined as the ratio between the total mass flow rate of the incoming feed and the total mass of catalyst, of between 0.1 and 10 h -1 and preferably between 0.4 and 5 hours -1 .

[0064] According to a second embodiment, the catalyst used in the first oligomerization step a) is a homogeneous oligomerization catalyst.

[0065] Advantageously, the homogeneous catalyst used in step a) of oligomerization of the process according to the invention comprises:

[0066] - at least one nickel precursor with oxidation state (+II),

[0067] - and at least one activating agent chosen from the group formed by chlorinated and brominated hydrocarbylaluminium compounds, taken alone or in mixture.

[0068] Optionally, the homogeneous catalyst used in step a) of oligomerization of the process according to the invention further comprises at least one Brønsted organic acid, or at least one carboxylic acid anhydride, or at least one phosphine ligand of formula PR 1 R 2 R 3 in which the R groups 1 , R 2 and R 3 , identical or different from each other, linked or not to each other, as explained further down in this description.

[0069] Nickel compounds with an oxidation state of (+II) are preferably soluble in hydrocarbons, and more particularly in the reactants and reaction medium. Preferably, they are nickel carboxylates of the general formula (RCOO^Ni), where R is a hydrocarbyl radical, for example, alkyl, cycloalkyl, alkenyl, aryl, aralkyl, or alkaryl, containing up to 20 carbon atoms, preferably a hydrocarbyl residue of 5 to 20 carbon atoms. The R radical may be substituted by one or more halogen atoms, by one or more hydroxyl, ketone, nitro, cyano groups, or other groups that do not interfere with the reaction. The two R radicals may also constitute an alkylene residue of 6 to 18 carbon atoms.The divalent nickel compounds are advantageously chosen from the following divalent nickel salts: octoate, ethyl-2-hexanoate, decanoate, stearate, oleate, salicylate and hydroxydecanoate, taken alone or in mixtures and preferably the divalent nickel compound is nickel ethyl-2-hexanoate.

[0070] The activating agent is chosen from the group of chlorinated and brominated hydrocarbylaluminum compounds conforming to the formula AIRX2, where R is a hydrocarbyl radical and X is a halogen chosen from chlorine and bromine alone or in mixtures. The hydrocarbylaluminum halides are advantageously chosen from dichloroethylaluminum, dichloroisobutylaluminum, and dibromoethylaluminum. These hydrocarbylaluminum dihalides can be advantageously enriched with aluminum trihalides (AIX3) such as aluminum trichloride.

[0071] Brønsted organic acid compounds preferably correspond to the formula HY, where Y is an organic anion, for example, carboxylic or sulfonic. These compounds are preferably chosen from the group formed by halocarboxylic acids of the formula RCOOH, in which R is a halogenated alkyl radical, and preferably a halogenated alkyl radical containing at least one halogen atom located on the alpha carbon of the -COOH group, with a total of 2 to 10 carbon atoms. A haloacetic acid of the formula CX is preferably used. P H(3- P )-COOH in which X is fluorine, chlorine, bromine, or iodine, with p an integer from 1 to 3. Examples include trifluoroacetic, difluoroacetic, fluoroacetic, trichloroacetic, dichloroacetic, and chloroacetic acids. These examples are not exhaustive, and arylsulfonic, alkylsulfonic, fluoroalkylsulfonic, picric acid, and nitroacetic acid can also be used.

[0072] The catalyst used in the first oligomerization step (a) may also contain at least one carboxylic acid anhydride of formula (RCO)2U, in which R is a hydrocarbyl radical that may advantageously contain one or more halogen atoms. The carboxylic acid anhydrides are advantageously selected from octoic, 2-ethylhexanoic, decanoic, stearic, oleic, trifluoroacetic, monofluoroacetic, trichloroacetic, monochloroacetic, pentafluoropropionic, or heptafluorobutyric anhydrides, taken alone or in mixtures. Preferably, the carboxylic acid anhydride is trifluoroacetic acid anhydride.

[0073] Finally, the catalyst used in the first step a) of oligomerization may also contain a phosphine ligand of formula PR 1 R 2 R 3 in which the R groups 1 , R 2 and R 3'identical or different from each other, linked or not to each other. The hydrocarbyl groups R 1 , R 2 and R 3 of the phosphine ligand PR 1 R 2 R 3 advantageously comprise 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, preferably between 3 and 10 carbon atoms. Preferably, the hydrocarbyl groups R 1 , R 2 and R 3 of the phosphine ligand PR 1 R 2 R 3 are chosen from the group formed by the methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, cyclopentyl, cyclohexyl, benzyl, adamantyl groups.

[0074] The catalyst can be preconditioned before contacting it with ethylene. Preconditioning the catalytic composition involves mixing the components in a hydrocarbon solvent, such as an alkane, an aromatic hydrocarbon, a halogenated hydrocarbon, or preferably the olefins produced in the oligomerization reaction. This mixing is carried out under stirring and in an inert atmosphere, such as nitrogen or argon, at a controlled temperature between 0 and 80 °C, preferably between 10 and 60 °C, for a duration of 1 minute to 5 hours, preferably 5 minutes to 1 hour. The resulting solution is then transferred under an inert atmosphere to the oligomerization reactor.

[0075] This preconditioning of the catalyst increases the activity of the homogeneous catalyst in the oligomerization of ethylene.

[0076] The catalyst present in said unit carrying out the oligomerization step a) is in liquid form. Depending on the chemical composition of said catalyst, the weight proportions of each of the catalyst components must be controlled during catalyst synthesis. The molar ratio of the hydrocarbylaluminium halide to the nickel compound, expressed as the Al / Ni ratio, is from 2:1 to 50:1, and preferably from 2:1 to 20:1.

[0077] The molar ratio of Brønsted acid to nickel compound is from 0.25:1 to 10:1, and preferably from 0.25:1 to 5:1. If the catalyst comprises carboxylic acid anhydride, the molar ratio of carboxylic acid anhydride to nickel compound is advantageously from 0.001:1 to 1:1, most advantageously from 0.01:1 to 0.5:1. If the catalyst comprises a phosphine-type ligand, the molar ratio of the phosphine-type ligand to nickel compound is advantageously from 1 to 25, preferably from 2 to 20, and more preferably from 5 to 15. In one embodiment, said homogeneous catalyst is the catalyst described in document WO2017017087.

[0078] According to this second embodiment, the first oligomerization step (a) implemented by homogeneous catalysis is advantageously carried out continuously: the catalytic solution is injected into the unit performing the oligomerization step, and ethylene is injected therein continuously. The unit performing said oligomerization step of ethylene by homogeneous catalysis comprises one or more perfectly stirred reactors in series, with recycling at least a portion of the reactor effluent into the reactor, this recycling having advantageously been cooled.

[0079] The first oligomerization step a) implemented by homogeneous catalysis can advantageously be implemented in a reactor with one or more series reaction stages, the predominantly ethylenic charge and / or the previously pre-conditioned catalytic composition being introduced continuously, either in the first stage, or in the first and any other of the stages.

[0080] According to this second embodiment, the operating conditions in the reactor(s) carrying out the homogeneous catalytic oligomerization step are such that the temperature is between -20 °C and +80 °C and the pressure is sufficient to allow the existence of a liquid phase in the reactor(s). Preferably, the total absolute pressure in the reactor(s) is between 0.1 and 10.0 MPa, preferably between 0.2 and 8.0 MPa, and preferably between 0.5 and 6.0 MPa, with a residence time in the reactor of between 2.0 and 4.0 h, preferably between 2.5 and 3.5 h, and preferably with a residence time of 3.0 h.

[0081] In the context of the invention, and more particularly according to the second embodiment, the temperature and / or pressure of the first oligomerization step a) carried out by homogeneous catalysis (corresponding to the temperature and / or pressure of the reaction mixture) is controlled to ensure that the reaction mixture operates at the ethylene bubble point. According to the invention, the bubble point corresponds to the pressure and temperature conditions under which the first gas bubbles (C2H4) appear. Preferably, the pressure of the first oligomerization step a) is controlled to ensure that the reaction mixture operates at the ethylene bubble point.The pressure during the first oligomerization step (a) can be controlled either by varying the pressure of the oligomerization reactor by injecting fresh feedstock, or by adjusting the recycle of the C2-C3 olefinic effluent obtained by optionally separating the olefinic effluent from the first oligomerization step (a) to adjust the ethylene partial pressure. At the outlet of the first oligomerization step (a), the homogeneous catalytic system is mixed with the effluent produced in step (a), which includes C4+ olefins and unreacted ethylene.

[0082] Advantageously, the olefinic effluent produced in the first oligomerization step (a) implemented by homogeneous catalysis undergoes at least one treatment / separation step of the homogeneous catalytic system of said effluent before being sent to the second oligomerization step (b). A treatment / separation step of the homogeneous catalytic system is understood to be a step in which said catalytic system is deactivated and separated from the homogeneous reaction medium, and in particular from the olefinic effluent from the first oligomerization step (a).

[0083] An example of a first oligomerization step a) is the Dimersol-E™ process marketed by the company Axens.

[0084] Step b) of the second oligomerization

[0085] The process according to the invention comprises a second step b) of oligomerizing at least a part of said at least a first effluent from step a) to obtain a second effluent comprising compounds having a number of carbon atoms greater than or equal to 9 (C9+) and comprising at least 50% by weight, preferably at least 70% by weight and preferably at least 90% by weight of olefins having a number of carbon atoms greater than or equal to 9 (C9+) relative to the total weight of said effluent, said second oligomerization step being carried out in the presence of a heterogeneous catalyst comprising an amorphous support or a support comprising at least one zeolite.

[0086] In the context of the invention, the portion of the first effluent from step a) which is introduced and thus oligomerized in this step b) comprises a content of C4 and C6 olefins such that the weight ratio, expressed as a percentage, between the olefins having 6 carbon atoms (C6) and the sum of the olefins having 4 carbon atoms and the olefins having 6 carbon atoms (C4 + C6) is greater than 22.0%, preferably greater than or equal to 24.0%, preferably greater than or equal to 28.0%, and preferably less than or equal to 50.0%, preferably less than or equal to 37.0% and most preferably less than or equal to 34.0%.

[0087] This particular ratio between C6 olefins and C4 olefins in the first effluent allows for increased formation of olefinic compounds comprising 10 carbon atoms (C10), thus increasing the production of aviation fuel at the end of the process.

[0088] Said second oligomerization step b) is advantageously carried out in the presence of an amorphous or zeolitic heterogeneous catalyst. According to a first embodiment of the invention, the heterogeneous catalyst used in the second oligomerization step b) is a catalyst comprising an amorphous support. Advantageously, said amorphous catalyst comprises, and preferably consists of, an amorphous mineral material selected from silica-aluminas and silicified aluminas.

[0089] According to a second embodiment of the invention, the heterogeneous catalyst used in the second oligomerization step (b) is a catalyst comprising a support including at least one zeolite. Advantageously, said zeolite catalyst comprises, and preferably consists of, a zeolite, preferably having at least pore openings containing 10 or 12 oxygen atoms (10MR or 12MR), and preferably selected from aluminosilicate zeolites having an overall Si / Al ratio greater than 10.

[0090] According to this second embodiment, the zeolite catalyst preferentially comprises a zeolite chosen from among the structural type zeolites MFI, MTW, MOR, TON, MEL, MFS, MTT, taken alone or in mixture.

[0091] Preferably, the zeolite catalyst used in the second oligomerization step b) comprises a zeolite selected from the zeolites ZSM-5, ZSM-12, Nll-86, Mordenite, ZSM-22, NU-10, ZBM-30, ZSM-48, ZSM-11, ZSM-57, IZM-2, ITQ-6 and IM-5, taken alone or in mixture, preferably from the zeolites ZSM-5, NU-10 and ZBM-30, taken alone or in mixture, most preferably the zeolite is ZBM-30 and even more preferably the zeolite is ZBM-30 advantageously synthesized in the presence of the triethylenetetramine structuring agent.

[0092] According to the second embodiment of the invention, the zeolite used in the catalyst in step b) of the process according to the invention can advantageously undergo several post-treatments known to those skilled in the art. For example, it can be modified by desalumination or desilication using any desalumination, external surface passivation, or desilication method known to those skilled in the art, in order to improve its activity and / or stability.

[0093] According to a very specific embodiment in which silica-alumina is used as a catalyst for the second oligomerization step, said silica-alumina enables the oligomerization of at least a portion of the first effluent from step a), with better control of olefin reactivity. This allows, in particular, for low-pass conversion and, very advantageously, optimizes selectivity for the desired olefins, compared to oligomerization in the presence of other catalysts, such as zeolites. Furthermore, coke formation is less significant and less rapid in the presence of silica-alumina than in the presence of zeolites. Thus, silica-alumina requires regeneration at a lower frequency than zeolites.

[0094] The heterogeneous catalyst used in step b) of the process according to the invention, in particular the zeolite catalyst, advantageously also comprises at least one oxide-type matrix, also called a binder. The term "matrix" according to the invention refers to an amorphous or poorly crystallized matrix.

[0095] The matrix is ​​advantageously chosen from among the elements of the group formed by clays (such as, for example, natural clays like kaolin or bentonite), magnesia, aluminas, silicas, silica-aluminas, aluminates, titanium oxide, boron oxide, zirconia, aluminum phosphates, titanium phosphates, zirconium phosphates, and coal. Preferably, the matrix is ​​chosen from among the elements of the group formed by aluminas, clays, and silicas; more preferably, the matrix is ​​chosen from among aluminas; and even more preferably, the matrix is ​​gamma alumina.

[0096] Advantageously, the catalysts used in step b) of the process according to the invention are shaped into grains, particularly of various shapes and sizes. They are advantageously used in the form of cylindrical or multilobed extrudates such as bilobed, trilobed, or multilobed, with a straight or twisted shape, but can optionally be manufactured and used in the form of crushed powder, tablets, rings, balls, wheels, or spheres. Preferably, said catalysts are in the form of extrudates with a size between 1 and 10 mm.

[0097] Advantageously, the second step b) of oligomerization is implemented in at least one reactor, in particular a fixed bed reactor.

[0098] Preferably, the second oligomerization step b) of the process according to the invention operates at a temperature between 20 and 500°C, preferably between 100 and 350°C and preferably between 100 and 300°C, at a pressure between 1.0 and 10.0 MPa, preferably between 2.0 and 8.0 MPa and preferably between 3.0 and 7.0 MPa and with a WH preferably between 0.1 and 10.0 h' 1 , preferably between 0.1 and 5.0 h' 1 and preferably between 0.2 and 0.3 h- 1 .

[0099] The WH (or hourly volumetric velocity) is, according to the invention, defined by the ratio between the volumetric flow rate of fresh olefinic feed in particular at 15°C and 1 atmosphere and the volume of oligomerization catalyst in particular in operation (also called in operation), not counting any recycles.

[0100] The process according to the invention is a flexible process in that the operating conditions and the choice of catalyst in the second step b) of oligomerization allow the reaction to be directed towards one or the other of the target products, namely in one case towards the major production of a hydrocarbon base of the diesel type and in the other of a hydrocarbon base of the kerosene type.

[0101] In cases where the primary goal is the production of a basic hydrocarbon fuel of the diesel type, the second step b) of oligomerization operates advantageously in the presence of a catalyst comprising at least one zeolite selected from aluminosilicate zeolites having an overall Si / Al ratio greater than 10 and a pore structure of 10 or 12MR, at a temperature between 200 and 300°C, at a pressure between 3 and 7 MPa and at a weight-per-hour rate between 0.1 and 5 h -1 .

[0102] In cases where the main production of kerosene-type hydrocarbon base is particularly desired, the second step b) of oligomerization advantageously operates in the presence of an amorphous catalyst, preferably comprising and preferably composed of silica alumina, at a temperature between 100 and 300°C, at a pressure between 2 and 6 MPa and at an hourly weight rate between 0.1 and 5 h' 1 .

[0103] An example of a second oligomerization step b) is the Polynaphtha™ process marketed by the company Axens.

[0104] Preferably, the effluent obtained at the end of the second oligomerization of step b) comprises a maximum of 40% by weight, preferably a maximum of 30% by weight of compounds having a number of carbon atoms greater than or equal to 9 (C9+), relative to the total weight of olefins contained in said effluent.

[0105] Advantageously, the effluent obtained after the second oligomerization of step b) is separated into at least one effluent comprising hydrocarbon compounds having a carbon number greater than or equal to 9 (C9+) and comprising at least 50% by weight, preferably at least 70% by weight, and preferably at least 90% by weight of olefins having a carbon number greater than or equal to 9 (C9+) relative to the total weight of this effluent, and constituting said second effluent, and into at least one hydrocarbon effluent comprising a content of at least 90% by weight of compounds having a carbon number less than or equal to 8 (C8-), relative to the total weight of this effluent. Thus, step b) may include a fractionation step, preferably downstream of the second oligomerization, i.e., downstream of the oligomerization reactors.Preferably, the hydrocarbon effluent comprising a content of at least 90% by weight of compounds having a number of carbon atoms less than or equal to 8 (C8-), relative to the total weight of this effluent, from said separation is advantageously recycled at the inlet of the second oligomerization step b). Thus, the compounds having a number of carbon atoms less than or equal to 8 (C8-), not converted during the second oligomerization step b) are separated from the second effluent from step b) and then recycled at the inlet of the second oligomerization step b).

[0106] Step c) of hydrogenation

[0107] The process according to the invention further includes a step c) of hydrogenating at least a part of the second effluent from step b) to obtain a third effluent comprising a content of at least 90% by weight of paraffins, the percentages being advantageously given by weight relative to the total weight of hydrocarbon compounds of the third effluent.

[0108] Advantageously, said third effluent comprises at least 90% by weight, preferably at least 95% by weight, preferably at least 98% by weight of paraffins, the percentages being advantageously given in weight relative to the total weight of hydrocarbon compounds in the third effluent.

[0109] Preferably, step c) of hydrogenation is carried out by contacting at least part and advantageously all of the second effluent with a hydrogen-rich gas, in the presence of a hydrogenation catalyst.

[0110] The hydrogenation catalyst used in step c) can be any hydrogenation catalyst known to those skilled in the art. Preferably, it comprises at least one metal from group VIII, preferably chosen from palladium and nickel alone or in a mixture, and a support preferably chosen from alumina, silica, or silica-alumina.

[0111] Preferably, the hydrogenation catalyst implemented in step c) of hydrogenation comprises a palladium content advantageously between 0.1 and 10 wt%, and / or a nickel content advantageously between 1 and 60 wt%, relative to the total mass of the hydrogenation catalyst.

[0112] Step c) of hydrogenation is advantageously carried out at a temperature between 100 and 250°C at the reactor inlet, at a pressure between 2.0 and 5.0 MPa and at an hourly weight rate between 0.05 and 8.0 h -1 .

[0113] The performance of the hydrogenation in step c) is advantageously controlled by a measurement of the bromine number which is advantageously not more than 5 g Br / 100 g according to ASTM D1159, in the case where all the unsaturated compounds present in the cut to be hydrogenated are saturated.

[0114] Preferably, the third effluent, comprising at least 90% by weight, preferably at least 95% by weight, and preferably at least 98% by weight of paraffins relative to the total weight of hydrocarbon compounds in this third effluent, obtained after hydrogenation step c), may be sent to an optional fractionation step d). According to one embodiment, at least a portion of said effluent from hydrogenation step c may advantageously be recycled into the first oligomerization step a) and / or the second oligomerization step b) so as to constitute a diluent for the feedstock of said step a) and thus stabilize the catalyst.

[0115] When the desired fuel is kerosene, the hydrogenation step of olefins is essential.

[0116] Step d) of splitting, optional

[0117] The process according to the present invention may include a step d) of fractionating the third effluent from step c) to obtain at least one aviation fuel type cut.

[0118] Step d) of fractionation is advantageously carried out in at least one distillation column so as to separate said middle distillate effluent into at least two cuts:

[0119] - A petrol cut,

[0120] - A middle distillates cut (diesel cut and / or kerosene cut).

[0121] A light effluent containing C2-C4 compounds can also be separated for valorization either pure or in mixture.

[0122] A heavy fraction having an initial boiling point between 350 and 370 °C can also be advantageously separated.

[0123] The term "gasoline" cut refers to the cut comprising hydrocarbon compounds whose boiling point is between ambient temperature and 220°C.

[0124] The term "middle distillates" refers to the cut comprising hydrocarbon compounds with a boiling point between 110 and 360°C.

[0125] The term "diesel blend" refers to the blend comprising hydrocarbon compounds with a boiling point between 220 and 360°C.

[0126] The term "kerosene cut" refers to the cut comprising hydrocarbon compounds with a boiling point between 110 and 300°C.

[0127] In a particular embodiment of the invention, step d) of fractionation uses at least one distillation column, so as to separate said third effluent into at least 3 cuts:

[0128] - A naphtha-type cup,

[0129] - A blend of aviation fuel type, - A blend of diesel type.

[0130] The term "aviation fuel blend" refers to the blend comprising hydrocarbon compounds with a boiling point between 110°C and 300°C. This blend may also be called the "kerosene blend".

[0131] The term "naphtha" refers to the cut comprising hydrocarbon compounds whose boiling point is between ambient temperature and 220°C.

[0132] In a particular embodiment, step d) of fractionation also allows a gas cut to be separated which is advantageously purged.

[0133] EXAMPLES

[0134] Example 1: Process for producing aviation fuel according to an embodiment of the prior art:

[0135] The feedstock in question is a bio-based olefinic fraction obtained from the dehydration of ethanol, having the following composition (values ​​in weight percentage):

[0136] Table 1

[0137] First oligomerization step a)

[0138] The catalyst is the homogeneous nickel-based catalyst marketed by Axens under the name LC1251. The co-catalyst is dichloroethylaluminum (EADC). It is used in solution in n-hexane. The molar ratio between the catalyst and the co-catalyst is fixed to achieve an Al / Ni molar ratio of 15.

[0139] The reactor is operated under the operating conditions shown in Table 2.

[0140] Table 2 The C4+ compound composition of the olefinic effluent from step a) is given in the following table.

[0141] Table 3

[0142] The conversion of ethylene per pass is 87.4%.

[0143] The selectivity of the different cuts is as follows:

[0144] - 72.9% by weight of C4 olefins

[0145] - 20.4% by weight of C6 olefins

[0146] - 6.7% by weight in C8+ olefins.

[0147] The effluent from the first oligomerization step a) comprises a weight ratio, expressed as a percentage, between olefins having 6 carbon atoms (C6) and the sum of olefins having 4 carbon atoms and olefins having 6 carbon atoms (C4+C6) of: 20.2 / (72.2+20.2) = 21.9%.

[0148] Second oligomerization step b)

[0149] The effluent from the first oligomerization step a) is sent directly to the second oligomerization step b).

[0150] The second oligomerization step is carried out in the presence of the silica-alumina catalyst marketed under the brand name IP811 by Axens. The operating conditions for step b) are a temperature of 110°C, a pressure of 6 MPa at the reactor inlet, and a total hourly volumetric velocity in the reactors of 0.2 h -1 (excluding recycling).

[0151] The recycling rate of the C8- fraction relative to the feed entering the oligomerization step (b) is 4.3. The composition of the effluent from the second oligomerization step is described in the following table:

[0152] Table 4 Step c) Hydrogenation of olefins

[0153] The feedstock entering the olefin hydrogenation stage consists of the effluent from the second oligomerization stage b).

[0154] Step c) of olefin hydrogenation operates with a nickel-on-alumina catalyst marketed under the name AX 746 by Axens. This step operates at a temperature of 180°C and a pressure of 1.5 MPa at the reactor inlet. The hourly volumetric velocity in the reaction section is 0.5 h' 1 .

[0155] The hydrogenated effluent is then sent to a fractionation column (fractionation step d)) where a kerosene cut and a diesel cut are recovered.

[0156] The fuel yield of the effluent from the hydrogenation step c) and fractionation step d) is described in the following table:

[0157] Table 5

[0158] The selectivity of the different cuts is as follows:

[0159] - 92% by weight in kerosene - 8% by weight in diesel.

[0160] The overall process yield is described in the following table:

[0161] Table 6

[0162] The overall yield of the prior art process is 88.4% for the production of bio-based kerosene.

[0163] Example 2: Process for producing aviation fuel according to the invention:

[0164] The load considered is the same as that in example 1.

[0165] First oligomerization step a) The catalyst used is the same as that of example 1.

[0166] The reactor is operated under the operating conditions shown in Table 7.

[0167] Table 7 The C4+ compound composition of the olefinic effluent from step a) is given in the following table.

[0168] Table 8

[0169] The ethylene conversion per pass is 97.1%. The selectivities of the different cuts are as follows:

[0170] - 61.5% by weight of C4 olefins

[0171] - 28.5% by weight of C6 olefins

[0172] - 10.0% by weight of C8+ olefins.

[0173] The effluent from the first oligomerization step a) comprises a weight ratio, expressed as a percentage, between olefins with 6 carbon atoms (C6) and the sum of olefins with 4 carbon atoms and olefins with 6 carbon atoms (C4+C6) of: 28.2 / (60.9+28.2) = 31.6%. Second oligomerization step b)

[0174] The effluent from the first oligomerization step a) is sent directly to the second oligomerization step b).

[0175] The second oligomerization step is carried out in the presence of the same catalyst as that used for step b) of example 1. The operating conditions of step b) are the same as those of example 1.

[0176] The recycling rate of the C8- fraction relative to the feed entering the oligomerization step (b) is 4.3.

[0177] The composition of the effluent from the second oligomerization stage is described in the following table:

[0178] Table 9

[0179] Step c) Hydrogenation of olefins

[0180] The feedstock entering the olefin hydrogenation stage consists of the effluent from the second oligomerization stage b).

[0181] Step c) of olefin hydrogenation operates with the same catalyst as that used for step c) of example 1. This step operates under the same conditions as those of example 1.

[0182] The hydrogenated effluent is then sent to a fractionation column (fractionation step d)) where a kerosene cut and a diesel cut are recovered.

[0183] The fuel yield of the effluent from the hydrogenation step (c) and fractionation step (d) is described in the following table: Table 10

[0184] The selectivity of the different cuts is as follows:

[0185] - 99% by weight kerosene - 1% by weight diesel.

[0186] The overall process yield is described in the following table:

[0187] Table 11

[0188] The overall yield of the process according to the invention is 95.1% for the production of bio-based kerosene.

[0189] When the effluent 11 from the first oligomerization a) comprises a weight ratio, expressed as a percentage, between olefins having 6 carbon atoms (C6) and the sum of olefins having 4 carbon atoms and olefins having 6 carbon atoms greater than 22.0%, the selectivity towards the kerosene cut is optimized and the kerosene yield of the process is maximized, compared to the prior art process.

Claims

DEMANDS 1. A process for producing aviation fuel from a feedstock comprising at least 90% by weight of ethylene relative to the total weight of the feedstock, said process comprising the following steps: a) a first oligomerization step of said feedstock and obtaining at least a first effluent comprising olefins having a number of carbon atoms greater than or equal to 4 (C4 +), wherein: said at least one first effluent comprises at least olefins having 4 carbon atoms and olefins having 6 carbon atoms, the weight ratio, expressed as a percentage, between the olefins having 6 carbon atoms (C6) and the sum of the olefins having 4 carbon atoms and the olefins having 6 carbon atoms (C4 + C6) of said at least one first effluent is greater than 22.0%, the olefins having a number of carbon atoms greater than or equal to 4 (C4+) of said at least one first effluent representing at least 90% by weight relative to the total weight of the olefins contained in said at least one first effluent, said first oligomerization step being carried out in the presence of an oligomerization catalyst;b) a second oligomerization step of at least a portion of said at least a first effluent from step a) and obtaining a second effluent comprising compounds having a number of carbon atoms greater than or equal to 9 (C9+) and comprising at least 50% by weight of olefins having a number of carbon atoms greater than or equal to 9 (C9+) relative to the total weight of said effluent, said second oligomerization step implementing an oligomerization phase in the presence of a heterogeneous catalyst comprising an amorphous or zeolitic support, c) a hydrogenation step of at least a portion of the second effluent from step b) to obtain a third effluent comprising at least 90% by weight of paraffins relative to the total weight of hydrocarbon compounds of the third effluent.; 2. A process according to claim 1, wherein the weight ratio, expressed as a percentage, between 6-carbon olefins (C6) and the sum of 4-carbon olefins and 6-carbon olefins (C4 + C6) in said at least a first effluent from step a) is greater than or equal to 24.0%, and preferably less than or equal to 50.0%, preferably less than or equal to 37.0%.

3. A process according to any one of the preceding claims, further comprising a step d) of fractionating the third effluent from step c) to obtain at least one aviation fuel type cut.

4. A method according to any one of the preceding claims, wherein step a) is carried out by homogeneous catalysis, at a pressure between 0.1 and 10.0 MPa, preferably between 0.2 and 8.0 MPa, preferably between 0.5 and 6.0 MPa and with a residence time in the reactor between 2.0 and 4.0 h, preferably between 2.5 and 3.5 h and preferably with a residence time of 3.0 h.

5. A process according to any one of the preceding claims, wherein the oligomerization catalyst used in the first oligomerization step (a) is a homogeneous catalyst, preferably said homogeneous catalyst comprising - at least one nickel precursor with oxidation state (+II), - and at least one activating agent chosen from the group formed by chlorinated and brominated hydrocarbylaluminium compounds, taken alone or in mixture.

6. A process according to any one of claims 1 to 3, wherein the oligomerization catalyst used in the first oligomerization step a) is a heterogeneous catalyst, preferably said heterogeneous catalyst comprising at least one element of Group VIII and at least one support.

7. A process according to any one of the preceding claims, wherein said at least one first effluent from the first oligomerization step a) comprises less than 5% by weight of ethylene not having reacted during the first oligomerization step a), relative to the total weight of olefins contained in said first effluent.

8. A process according to any one of the preceding claims, wherein the oligomerization catalyst used in the second oligomerization step b) is a heterogeneous catalyst comprising an amorphous support or a support comprising at least one zeolite having at least pore openings containing 10 or 12 oxygen atoms.

9. A process according to any one of the preceding claims, wherein the second effluent from step b) comprises compounds having a number of carbon atoms less than or equal to 8 (C8-), not converted during the second oligomerization step b), said compounds having a number of carbon atoms less than or equal to 8 being separated from the second effluent from step b) and then recycled at the inlet of the second oligomerization step b).

10. A process according to any one of the preceding claims, wherein said at least a first effluent from the first oligomerization step a) is sent to step b) without undergoing a fractionation step.

11. Kerosene base obtained by the process according to any one of claims 1 to 10.

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

13. Use of a composition according to the preceding claim, as fuel for aviation engines.

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