Method for producing middle distillates, in particular kerosene, from alcohol feedstock

Abstract

The invention relates to a process for the production of a hydrocarbyl feedstock of the middle distillate type from an alcoholic feedstock, said process comprising the following stages: a) dehydration of the alcoholic feedstock and producing at least a dehydrated effluent comprising:-at least 80% by weight, relative to the total weight of the effluent, of ethylene on a dry basis,-a compound having at least 3 carbon atoms; the process is carried out in the presence of an acidic amorphous catalyst or an acidic zeolite catalyst; b) separating the dehydrated effluent obtained in stage a) and producing at least: a fraction substantially comprising ethylene, a fraction substantially comprising compounds having at least 3 carbon atoms; c) oligomerization of at least a portion of the fraction essentially comprising ethylene obtained from stage b) and producing at least an olefinic effluent comprising at least 80% by weight, relative to the total weight of olefins contained in the olefinic effluent, of olefins having a number of carbon atoms greater than or equal to 4, carried out in the presence of a homogeneous catalyst; d) oligomerization of at least the following:-a portion of the effluent from stage c),-a portion of the fraction from stage b) essentially containing compounds having at least 3 carbon atoms, and producing an effluent of the middle distillate type, which is carried out in the presence of an amorphous or zeolitic heterogeneous catalyst; e) fractionation of the effluent of the middle distillate type obtained from stage d).

Description

Technical Field

[0001] The present invention relates to a method for converting alcohol feedstocks, and more particularly ethanol feedstocks, preferably bioethanol, into middle distillate oils, especially into gas oils and / or kerosene fuel bases by means of a feedstock dehydration stage and two successive oligomerization stages. Existing technology

[0002] The demand for using biomass to at least partially replace petroleum resources in fuel synthesis will continue to grow. Therefore, the use of bioethanol as a synthetic fuel base is receiving increasing attention.

[0003] Bioethanol is agricultural ethanol, meaning it is produced from renewable sources derived from biomass, such as living plant material.

[0004] Currently, most bioethanol is produced through the fermentation of sugars contained in plant-derived starting materials. Starting with sugar-producing plants, the first stage of this conversion involves obtaining a sugar solution through hot water extraction (for sugar beets) or through grinding and pressing (for sugarcane). After possible concentration, these liquids or syrups are introduced into fermentation tanks, where the bioconversion of sugars to ethanol and the co-production of CO2 occur under the action of microorganisms (yeast). The resulting alcohol contains approximately 10% alcohol in water. A distillation stage allows for the acquisition of an azeotropic composition of an ethanol / water binary mixture (8% water). To achieve complete dehydration, it must pass through molecular sieves. In cereal plants (corn, wheat), the sugars that can ferment to produce ethanol exist in the form of polymers called starch; to release them, a pre-hydrolysis stage catalyzed by enzymes is required.

[0005] Recently, technologies have become available for converting lignocellulosic biomass (wood, grass, straw, and other agricultural waste) into bioethanol. These technologies make it possible to use resources that do not compete with feeding humans or animals (in the sense of livestock farming).

[0006] There are also technologies that can produce ethanol from waste gases from the steel industry or from municipal solid waste incineration—using the gasification of these wastes, followed by microbial fermentation with CO and a portion of CO2 from the gas, as well as nutrients from microorganisms.

[0007] The use of ethanol is primarily intended for the production of gasoline, not for the production of gas oil and kerosene. Another very promising route is the use of ethanol as a biofuel in diesel engines. Biofuel E-Diesel is a mixture consisting of 85% to 95% diesel fuel, anhydrous (water-free) ethanol, and a suite of additives specifically produced for the stability of the mixture, overcoming some of the disadvantages of bioethanol, such as its low cetane number or its poor lubricity.

[0008] Blending conventional diesel with ethanol and additives improves combustion performance and slightly increases fuel volatility. The primary result is a reduction in emissions of regulated pollutants such as particulate matter (PM10) and soot. This reduction is attributed to the oxygen content of biofuels, which limits particulate formation during combustion. This is because these oxygen-containing molecules are able to significantly improve combustion quality by having an oxidant present at the same site where the oxidation reaction occurs. Blending bioethanol with diesel also has the major consequence of lowering the flash point, but this also has its drawbacks.

[0009] Mixing conventional jet engine fuel (referred to as Jet A1 in the context of customs regulations) with ethanol is not accepted by component manufacturers under current commercial standards (ASTM D7566), primarily due to issues with flammability (flash point), stability, water absorption, and energy content per liter. These drawbacks suggest that while it may be possible to use ethanol in small aircraft, it is not simply feasible to use it on the existing fleet.

[0010] Converting ethanol into hydrocarbons is therefore a favorable route for upgrading renewable resources towards fuels.

[0011] There is a wealth of literature on the conversion of alcohols (such as methanol-type alcohols) into olefins or aromatic compounds on acidic catalysts (usually zeolite catalysts) to produce gasoline fractions.

[0012] The production of ethylene from ethanol is a known process that has been developed on an industrial scale in several plants. Therefore, in the 1970s, following the oil crisis, a plant was built in Brazil to dehydrate ethanol to obtain ethylene. Ethanol is catalytically converted to ethylene starting at 300°C. The catalysts used can have different properties: activated alumina, silica-alumina, etc.

[0013] Scientific Design has developed its own technology for dehydrating ethanol to ethylene and published a paper ("Ethylene from Ethanol", NKKochar, R. Merims and AS Padia, CEP, June 1981) after developing a new catalyst for industrial applications. Patents US 4,232,179, US 4,396,789, US 4,234,752, US 4,396,789, and US 4,698,452 can also be cited.

[0014] IFPEN documents FR 2 959 750 and FR 2 959 752 disclose methods for producing middle distillate oil-type hydrocarbon feedstocks from ethanol feedstocks, including an ethanol dehydration stage followed by two oligomerization stages, one in a homogeneous phase and the other in a heterogeneous phase. Patent US 9 840 676 discloses a method for converting ethanol into diesel and / or kerosene through dehydration, conversion of the resulting ethylene to hexene, and then dimerization or trimerization to obtain a mixture containing C12 hydrocarbon compounds. These documents do not disclose a stage for upgrading the dehydrated effluent containing compounds with three or more carbon atoms (C3+ compounds), which are considered undesirable compounds.

[0015] Therefore, one object of the present invention is to provide a method for producing, in higher yields than prior art, middle distillate hydrocarbon feedstocks (gas oil and / or kerosene) and preferably kerosene feedstocks from alcohol feedstocks (preferably ethanol feedstocks) produced from renewable sources derived from biomass (also known as bioethanol).

[0016] The applicant company has surprisingly demonstrated that by upgrading the C3+ compounds formed during the dehydration stage of alcohol feedstocks to a heterogeneous oligomerization stage, the yield of favorable olefins for the production of middle distillate oils, and more particularly kerosene (approximately 0.5 to 10% of the converted carbon yield) is increased. The advantage of upgrading compounds that are initially undesirable upon exiting dehydration is primarily economic. Invention Overview This invention relates to a method for producing a hydrocarbon feedstock of the middle distillate oil type, preferably a kerosene hydrocarbon feedstock, from an alcohol feedstock comprising at least one monool, and preferably ethanol, the method comprising: a) A dehydration stage comprising at least one monool, preferably ethanol, of an alcohol feedstock, and producing at least a dehydrated effluent comprising: - On a dry basis, relative to the total weight of the effluent, at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of ethylene. - Compounds having at least 3 carbon atoms (C3+ compounds), preferably having 3 to 9 carbon atoms, and preferably having 3 to 6 carbon atoms. The dehydration stage is carried out in the presence of an acidic amorphous catalyst or an acidic zeolite catalyst; b) The stage of separating the dehydrated effluent obtained in stage a), and producing at least: - Essentially contains the fraction of ethylene. - A fraction that essentially contains compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and more preferably 3 to 6 carbon atoms; c) First oligomerization stage: which oligomerizes at least a portion of the fraction obtained from stage b) which substantially contains ethylene, and produces at least an olefin effluent containing at least 80% by weight of an olefin having a carbon number greater than or equal to 4 relative to the total weight of the olefins contained in the olefin effluent, wherein the first oligomerization stage is carried out in the presence of a homogeneous catalyst. d) Second oligomerization stage: which causes at least the following oligomerizations: - A portion of the effluent obtained from stage c). - A portion of a fraction obtained from stage b) that substantially contains compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, and produces an effluent of the middle distillate oil type. The second oligomerization stage is carried out in the presence of an amorphous or zeolite heterogeneous catalyst; e) The fractionation stage of the effluent of the middle distillate type obtained from stage d).

[0018] "Dry calculation" is understood to refer to the effluent ideally separated from the water produced during the dehydration reaction and / or any solvents that may be added before the dehydration stage, excluding alcohol feedstocks. Invention Details According to the present invention, the expressions "between... and..." and "...to..." are equivalent and refer to the fact that the limit value of the interval is included within the described numerical range. If this is not the case and if the limit value is not included within the described range, the present invention provides such details.

[0020] Within the scope of this invention, various ranges of parameters for a given stage, such as pressure ranges and temperature ranges, can be used individually or in combination. For example, within the scope of this invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0021] Specific embodiments of the invention may be described below. They may be implemented individually or in combination, and there is no limitation on the combination where technically feasible.

[0022] raw material According to the present invention, the raw material processed in the method according to the present invention is an alcoholic raw material (or alcoholic raw material) containing at least one monool. Preferably, the monool is ethanol.

[0023] Advantageously, the alcohol feedstock according to the method of the invention comprises at least 35% by weight of the monool, preferably from 35% by weight to 99.9% by weight. The alcohol feedstock may also contain 0% to 65% water. The alcohol feedstock may also contain inorganic impurities (such as Na, Ca, P, Al, Si, K, SO4) or organic impurities, such as monools other than the target monool, for example methanol or n-butanol in ethanol feedstocks, aldehydes, ketones, and corresponding acids, such as furanyl acid, acetic acid, or isobutyric acid. The alcohol feedstock may also particularly contain inorganic nitrogen- and / or sulfur-containing compounds, such as ammonia, or organic, preferably basic, nitrogen- and / or sulfur-containing compounds, such as amines, amides, imines, and sulfur-containing compounds (thiols, thiophenes, mercaptans, sulfides, disulfides, etc.). The organic and inorganic nitrogen and sulfur contents in the alcohol feedstock are preferably each less than or equal to 0.5% by weight, preferably less than or equal to 0.2% by weight, and the weight percentages are expressed relative to the total weight of the alcohol feedstock. According to the invention, "nitrogen content" and "sulfur content" should be understood as referring to the content of elemental nitrogen and elemental sulfur, respectively, provided by nitrogen-containing and sulfur-containing impurities present in the considered feedstock, particularly in the alcohol feedstock of the method of the invention. Preferably, the elemental nitrogen content is advantageously determined by combustion and chemiluminescence detection, and the elemental sulfur content is determined by combustion and UV fluorescence detection.

[0024] Advantageously, the alcohol feedstock can be derived from non-fossil resources. Preferably, the alcohol feedstock processed in the method according to the invention is produced from renewable resources derived from biomass, preferably through the fermentation of sugars derived from, for example, sugar-producing crops such as sugarcane (sucrose, glucose, fructose) or sugar beets, or also from starch plants (starch), or from lignocellulosic biomass, or from hydrolyzed cellulose (primarily glucose, as well as xylose and galactose), containing varying amounts of water. A more complete description of conventional fermentation processes can be found in the publication "Les Biocarburants, État des lieux,perspectives et enjeux du développement [Biofuels, Current State, Prospects and Developmental Challenges]", Daniel Ballerini, published by Technip.

[0025] The alcohol feedstock can also be advantageously obtained from syngas.

[0026] The alcohol feedstocks processed in the method according to the invention can also optionally be obtained by synthesizing alcohols from fossil resources, such as coal, natural gas or carbon-based waste.

[0027] The alcohol feedstocks according to the method of the invention can also be obtained by hydrogenation of the corresponding acid or ester. In this case, acetic acid or acetate esters are advantageously hydrogenated with hydrogen to obtain ethanol. Acetic acid can be obtained, for example, by carbonylation of methanol or by fermentation of carbohydrates.

[0028] Very preferably, the alcohol feedstock processed in the method according to the invention is an alcohol feedstock produced from renewable resources derived from biomass, more particularly bioethanol.

[0029] In one implementation, alcohol feedstocks may be subjected to a pretreatment stage to produce pretreated alcohol feedstocks.

[0030] The pretreatment stage is advantageously carried out on at least one acidic solid. The acidic solid can be selected from all solids known to those skilled in the art. Therefore, the acidic solid can be selected from: acidic clays, zeolites, zirconia sulfate, acidic resins, etc. For example, the acidic solid can be selected from commercially available acidic solids, such as clays (e.g., montmorillonite) treated with acid to make them acidic, and preferably zeolites having a silica / alumina molar ratio of 2.5 to 100 in the crystal lattice.

[0031] Preferably, the acidic solid is an acidic resin, particularly an ion exchange resin, preferably a cation exchange resin, especially having at least 0.1 mmol H₂. + The exchange capacity (or acid strength) in equivalents per gram, which is quantitatively determined (preferably by conductivity measurement) in relation to Na+. + H+ released by the acidic resin after ion exchange + Ions (specifically refer to ASTM D4266) are used for determination. For example, this acidic solid is a commercial acidic resin sold by Axens under the designation TA801.

[0032] Advantageously, the pretreatment stage enables the capture and thus removal of cationic impurities and possible anionic impurities, basic impurities, complexed or chelated impurities, inorganic or organic impurities, especially metal salts (such as K, Na, Ca, Fe, Cu, P, Cl salts) and nitrogen- and / or sulfur-containing impurities, such as basic nitrogen-containing compounds present in the raw material, for example in the form of ammonia and / or in the form of basic organic entities, such as amines, amides, imines or nitriles.

[0033] Advantageously, the alcohol feedstock is pretreated in accordance with the teachings of application FR 3 090 393.

[0034] Operating conditions and catalyst Dehydration stage a) The method according to the invention includes a dehydration stage a) of an alcohol feedstock containing at least one monool, preferably ethanol, and at least produces a dehydrated effluent comprising: - On a dry basis, relative to the total weight of the effluent, at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of ethylene. - A compound having at least 3 carbon atoms (C3+ compound), preferably having 3 to 9 carbon atoms, and preferably having 3 to 6 carbon atoms, wherein the dehydration stage is carried out in the presence of an acidic amorphous catalyst or an acidic zeolite catalyst. Non-limiting examples of compounds having three or more carbon atoms are alkenes, such as propylene, straight-chain butene, isobutene, methylbutene, and methylpentene; aromatic compounds, such as toluene and xylene; and alkanes, such as propane, butane, pentane, and hexane.

[0035] Advantageously, on a dry basis, the dehydrated effluent contains at least 1% by weight, preferably at least 5% by weight, and preferably at least 8% by weight, of a compound having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, relative to the total weight of the effluent. Very advantageously, on a dry basis, the dehydrated effluent exhibits less than 20% by weight, preferably less than 15% by weight, and preferably less than 10% by weight, of the aforementioned compound having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, relative to the total weight of the effluent.

[0036] Advantageously, compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, contain olefins, preferably at least 50% by weight, preferably at least 60% by weight, and most preferably at least 70% by weight, relative to the total weight of compounds having at least 3 carbon atoms.

[0037] In one embodiment, the dehydration effluent contains aromatic compounds in addition to olefins, preferably 1% to 10% by weight of aromatic compounds relative to the total weight of compounds having at least 3 carbon atoms.

[0038] When the catalyst used in the dehydration stage a) is a zeolite catalyst, the catalyst comprises at least one zeolite selected from zeolites having at least 8, 10, or 12 oxygen atoms in the pore openings (8 MR, 10 MR, or 12 MR). This is because it is known that the pore size of a zeolite is defined by the number of oxygen atoms (referred to as "membered rings" or MR) in the annular cross-section forming the zeolite channels. Preferably, the zeolite dehydration catalyst comprises at least one zeolite exhibiting a structural type selected from MFI, FAU, MOR, FER, SAPO, TON, CHA, EUO, MEL, and BEA. Preferably, the zeolite dehydration catalyst comprises an MFI structural type zeolite, and preferably ZSM-5 zeolite.

[0039] The zeolite can be advantageously modified by dealuminization or desiliconization according to any dealuminization or desiliconization method known to those skilled in the art.

[0040] The zeolite can be advantageously modified with reagents that reduce its total acidity and improve its hydrothermal resistance. Preferably, the zeolite or the catalyst advantageously contains phosphorus, preferably added in the form of H3PO4, followed by steam treatment after neutralizing excess acid with a basic precursor, such as calcium (Ca). Preferably, the zeolite contains 1% to 4.5% by weight, preferably 1.5% to 3.1% by weight, of phosphorus relative to the total weight of the catalyst.

[0041] In the case where the catalyst used in the dehydration stage a) is an acidic amorphous catalyst, the catalyst comprises at least one porous refractory oxide selected from alumina, alumina activated by inorganic acid deposition, and silica-alumina.

[0042] The amorphous or zeolite dehydration catalyst used in stage a) of the method according to the invention may also advantageously comprise at least one oxide-type matrix, also known as a binder. The matrix is ​​understood to refer to, according to the invention, an amorphous or weakly crystalline matrix.

[0043] The matrix is ​​advantageously selected from clay (e.g., natural clay such as kaolin or bentonite), magnesium oxide, aluminum oxide, silica, silica-alumina, aluminates, titanium oxide, boron oxide, zirconium oxide, aluminum phosphate, titanium phosphate, zirconium phosphate, and charcoal. Preferably, the matrix is ​​selected from alumina, silica, and clay.

[0044] The dehydration catalyst used in stage a) of the method according to the invention is advantageously shaped into particles of various shapes and sizes. It is advantageously used as a straight or twisted cylindrical extrusion or a multi-lobed extrusion, such as a bilobed, trilobed, or multi-lobed extrusion, but can optionally be manufactured and used in the form of crushed powder, ingots, rings, beads, wheels, spheres, or stars. Preferably, the catalyst is in the form of an extrusion or beads.

[0045] The dehydration stage of the method according to the invention (a) is advantageously performed at a temperature between 250°C and 600°C, preferably between 300°C and 600°C, and more preferably between 300°C and 500°C, at an absolute pressure between 0.1 and 5 MPa, preferably between 0.1 and 2.5 MPa, and more preferably between 0.1 and 1 MPa, and preferably for 0.1 to 50 h. -1 Between, and preferably in the manner of 0.5 to 15 h -1 It operates at the time-space velocity between these speeds.

[0046] Weight hourly space velocity is defined as the ratio of the weight flow rate of the feedstock to the weight of the catalyst entering stage a).

[0047] In stage a), the conversion rate of alcohol feedstock is advantageously greater than 90%, preferably 95%, and even more preferably greater than 98%.

[0048] The conversion rate of alcohol feedstock is understood as the ratio of the difference between the weight flow rate of alcohol feedstock at the inlet of stage a) and the weight flow rate of alcohol feedstock at the outlet of stage a) to the weight flow rate of alcohol feedstock at the inlet, the ratio being expressed as a percentage.

[0049] Advantageously, prior to separation stage b), the water present in the dehydrated effluent is separated by any method known to those skilled in the art.

[0050] The dehydration stage a) can be advantageously conducted in accordance with the teachings of applications WO 2014083260 and WO 2014083261.

[0051] An example of a dehydration method for alcohol feedstocks is Atol, sold by Axens. ® method.

[0052] Separation phase b) The method according to the invention includes a stage b) of separating the dehydrated effluent obtained in stage a), and at least produces: - Essentially contains the fraction of ethylene. - A fraction that essentially contains compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and more preferably 3 to 6 carbon atoms.

[0053] "Substantially" is understood to mean, relative to the total weight of the fraction under consideration, that it contains at least 95% by weight, preferably at least 97% by weight, and in a preferred manner at least 99% by weight of the desired compound.

[0054] Advantageously, compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, contain olefins, preferably at least 50% by weight, preferably at least 60% by weight, and most preferably at least 70% by weight, relative to the total weight of compounds having at least 3 carbon atoms.

[0055] In one particular embodiment of the invention, a fraction comprising substantially a compound having at least three carbon atoms is subjected to an additional separation stage to obtain at least: - Essentially an olefin fraction containing olefins with 3 to 6 carbon atoms. - Heavy fraction, which contains aromatic compounds, preferably having 6 to 9 carbon atoms.

[0056] In this particular embodiment, the olefin fraction, which substantially comprises olefins having 3 to 6 carbon atoms, is fed to the second oligomerization stage d). The heavy fraction, containing aromatic compounds (preferably having 6 to 9 carbon atoms), may also contain unsaturated alkenes or dienes (preferably having 6 to 9 carbon atoms). Advantageously, the heavy fraction is subjected to a selective hydrogenation stage of the unsaturated alkenes or dienes contained in the fraction, and the resulting effluent is then fed to the fractionation stage e). The selective hydrogenation stage of the heavy fraction allows for purification of this fraction to improve its oxidative stability. This is because the presence of heavy olefins makes the heavy fraction sensitive to peroxidation, ultimately leading to gum deposits in the final fuel.

[0057] Separation stage b) can be carried out by any method known to those skilled in the art, such as distillation, particularly continuous distillation, successive distillation, or continuous or batch multi-fraction distillation, optionally removing the side stream to extract the intermediate boiling fraction. This separation can also be performed using a column with an inner wall, thus reducing energy consumption. Molecular sieves or separation membranes can also be used as a supplement to or alternative to the distillation method.

[0058] Preferably, the dehydrated effluent obtained from stage a) undergoes at least a purification stage before separation stage b). This purification stage enables the removal of impurities that are detrimental to the oligomerization catalyst used in downstream stages c) and d), and in particular, the removal of oxygen-containing compounds present in the dehydrated effluent.

[0059] Optional purification stages can advantageously be carried out according to any method known to those skilled in the art, for example, treatment in a water washing tower, followed by an absorption tower with MDEA (methyldiethylamine) or other amines and a washing tower with sodium hydroxide, or any other means known to those skilled in the art in succession. Advantageously, a dryer can be used to achieve a water content compatible with the oligomerizing catalyst used in the downstream oligomerization stages d) and e). The water content of the fraction sent to the first oligomerization stage c) is advantageously between 0 and 500 ppm, preferably less than 100 ppm, and very preferably less than 1 ppm.

[0060] First oligomerization stage c) The method according to the invention includes a first oligomerization stage c): which oligomerizes at least a portion of the fraction obtained from stage b) which substantially contains ethylene, and produces at least an olefinic effluent containing at least 80% by weight, preferably 90% by weight, of an olefin having a carbon number greater than or equal to 4, relative to the total weight of the olefins contained in the olefinic effluent, of an olefin (C4+ compound), the first oligomerization stage being carried out in the presence of a homogeneous catalyst.

[0061] Advantageously, at least a portion of the fraction that substantially contains ethylene obtained from stage b), i.e., at least 50% by weight, preferably at least 90% by weight, preferably all of the fraction, undergoes the first oligomerization stage.

[0062] Advantageously, the olefin effluent obtained from the first oligomerization stage c) contains less than 20% by weight, preferably less than 10% by weight, of ethylene, particularly ethylene that was not converted during the first oligomerization stage c), the percentage being expressed as a weight percentage relative to the total weight of the olefins contained in the generated olefin effluent.

[0063] In one particular embodiment, the olefin effluent is rich in olefins having 4 to 8 carbon atoms and also contains olefins having at least 10 carbon atoms (C10+ compounds). More particularly, the olefin effluent produced during the first oligomerization stage c) advantageously contains at least 80% by weight, preferably at least 90% by weight, of a predominantly olefin compound having 4 to 8 carbon atoms, and less than 20% by weight, and preferably less than 10% by weight, of a predominantly olefin compound having 10 or more carbon atoms, the weight percentages being expressed relative to the total weight of the olefins contained in the produced olefin effluent.

[0064] According to the method of the present invention, in stage c), the catalyst used in the first oligomerization stage c) is a homogeneous catalyst, that is, the catalyst is soluble in a liquid phase consisting of dissolved ethylene and its oligomerization products.

[0065] Advantageously, the homogeneous catalyst used in the oligomerization stage c) of the method according to the invention comprises: - At least one nickel precursor in the (+II) oxidation state, - and at least one activator selected from chlorinated and brominated hydrocarbon aluminum compounds used alone or in mixtures.

[0066] Optionally, the homogeneous catalyst used in the oligomerization stage c) of the method according to the invention further comprises at least one organic Brønsted acid, or at least one carboxylic anhydride, or at least one phosphine ligand of the formula PR1R2R3, wherein groups R1, R2 and R3 may be the same as or different from each other, or may be connected to or not connected to each other.

[0067] The (+II) oxidized nickel compound is preferably a compound soluble in a hydrocarbon medium, more particularly in the reactants and the reaction medium, to a concentration greater than 1 g / L, preferably nickel carboxylate of the general formula (RCOO)2Ni, wherein R is a hydrocarbon group, such as an alkyl, cycloalkyl, alkenyl, aryl, aralkyl, or alkylaryl group containing up to 20 carbon atoms, preferably a hydrocarbon residue with 5 to 20 carbon atoms. The R group can be substituted by one or more halogen atoms, one or more hydroxyl, ketone, nitro, or cyano groups or other groups that do not hinder the reaction. Two R groups can also constitute an alkylene residue with 6 to 18 carbon atoms. The divalent nickel compound is advantageously selected from the following divalent nickel salts: octanoate, 2-ethylhexanoate, decanoate, stearate, oleate, salicylate, and hydroxydecanoate, used alone or in mixtures, and preferably, the divalent nickel compound is nickel 2-ethylhexanoate.

[0068] The activator is selected from chlorinated and brominated alkyl aluminum compounds corresponding to the formula AlRX2, where R is a hydrocarbon group and X is a halogen selected from chlorine and bromine, used alone or as a mixture. Alkyl aluminum halides are advantageously selected from dichloroethylaluminum, dichloroisobutylaluminum, and dibromoethylaluminum. These alkyl aluminum dihalides can advantageously enrich aluminum trihalides (AlX3), such as aluminum trichloride.

[0069] Brønsted organic acid compounds preferably correspond to the formula HY, where Y is an organic anion, such as a carboxylic acid, sulfonic acid, or phenolic anion. The compound preferably has a pKa of at most 3 at 20°C, and is preferably selected from halocarboxylic acids of the formula RCOOH, where R is a haloalkyl group, preferably a haloalkyl group having a total of 2 to 10 carbon atoms, containing at least one halogen atom at the α position relative to the -COOH group. The formula CX is preferred. p H 3-p-COOH haloacetic acids, where X is fluorine, chlorine, bromine, or iodine, and p is an integer from 1 to 3. Examples may include trifluoroacetic acid, difluoroacetic acid, fluoroacetic acid, trichloroacetic acid, dichloroacetic acid, or chloroacetic acid. These examples are not limiting, and aryl sulfonic acids, alkyl sulfonic acids, fluoroalkyl sulfonic acids, picric acid, and nitroacetic acid may also be used.

[0070] The catalyst used in the first oligomerization stage c) may also contain at least one carboxylic anhydride of the formula (RCO)₂O, wherein R is a hydrocarbon group and may advantageously contain one or more halogen atoms. The carboxylic anhydride is advantageously selected from octanoic anhydride, 2-ethylhexanoic anhydride, decanoic anhydride, stearic anhydride, oleic anhydride, trifluoroacetic anhydride, monofluoroacetic anhydride, trichloroacetic anhydride, pentafluoropropionic anhydride, or heptafluorobutyric anhydride, used alone or in mixtures. Preferably, the carboxylic anhydride is trifluoroacetic anhydride.

[0071] Finally, the catalyst used in the first oligomerization stage c) may also contain a phosphine ligand of formula PR1R2R3, wherein the R1, R2, and R3 groups may be the same as or different from each other, and may be connected to or not connected to each other. The hydrocarbon groups R1, R2, and R3 of the phosphine ligand PR1R2R3 advantageously comprise 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and more preferably 3 to 10 carbon atoms. Preferably, the hydrocarbon groups R1, R2, and R3 of the phosphine ligand PR1R2R3 are selected from methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, cyclopentyl, cyclohexyl, benzyl, and adamantyl.

[0072] Preconditioning of the catalyst can be carried out before contacting the catalyst with ethylene. Preconditioning of the catalyst composition involves mixing three components for 1 minute to 5 hours, preferably 5 minutes to 1 hour, at a controlled temperature between 0°C and 80°C, preferably between 10°C and 60°C, under stirring and in an inert atmosphere, such as nitrogen or argon, in a hydrocarbon solvent, for example in alkanes or aromatics, or halogenated hydrocarbons, or preferably in olefins produced in oligomerization reactions. The resulting solution is then transferred to an oligomerization reactor under an inert atmosphere.

[0073] This pre-conditioning of the catalyst can improve its activity in ethylene oligomerization.

[0074] The catalyst present in the unit undergoing oligomerization stage c) is provided in liquid form. The weight ratios of the components of the catalyst should be controlled during its synthesis, depending on its chemical composition. The molar ratio of the halogenated hydrocarbon aluminum to the nickel compound, expressed as an Al / Ni ratio, is advantageously from 2 / 1 to 50 / 1, and more preferably from 2 / 1 to 20 / 1.

[0075] The molar ratio of Brønsted acid to nickel compound is advantageously between 0.25 / 1 and 10 / 1, and more preferably between 0.25 / 1 and 5 / 1. If the catalyst comprises a carboxylic anhydride, the molar ratio of carboxylic anhydride to nickel compound is advantageously between 0.001 / 1 and 1 / 1, and very advantageously between 0.01 / 1 and 0.5 / 1. If the catalyst comprises a phosphine ligand, the molar ratio of phosphine ligand to nickel compound is advantageously between 2 and 25, preferably between 5 and 20, and more preferably between 5 and 15.

[0076] In one embodiment, the homogeneous catalyst is the catalyst described in document WO2017017087.

[0077] The first oligomerization stage c) carried out by homogeneous catalysis is advantageously continuous: a catalytic solution is injected into the unit carrying out the oligomerization stage, and ethylene is continuously injected therein. The unit carrying out the ethylene oligomerization stage by homogeneous catalysis comprises one or more fully stirred reactors in series, wherein at least a portion of the reactor effluent is recycled back into the reactor, and this recycling is advantageously cooled.

[0078] The first oligomerization stage c) can advantageously be carried out in a reactor having one or more reaction stages in series, by continuously introducing a feedstock, which is mainly olefinic, and / or a pre-conditioned catalyst composition into the first stage, or into the first stage and any other stage.

[0079] The operating conditions in the reactor for the oligomerization stage c) via homogeneous catalysis are such that the temperature is between -20°C and +80°C, and the pressure is sufficient to allow the presence of a liquid phase in the reactor. Preferably, the total absolute pressure in the reactor is between 0.5 and 8 MPa.

[0080] At the outlet of the first oligomerization stage c), the homogeneous catalytic system is mixed with the olefin effluent and unreacted ethylene produced during stage c).

[0081] Advantageously, the olefinic effluent generated during the first oligomerization stage c) preferably undergoes at least one stage c' (treatment / separation of the homogeneous catalytic system and the effluent) before being sent to the second oligomerization stage d).

[0082] The stage of processing / separating the homogeneous catalytic system is understood to refer to the stage in which the catalytic system is deactivated and separated from the homogeneous reaction medium, particularly from the olefin effluent obtained from the first oligomerization stage c). Stage c') of processing / separating the homogeneous catalytic system can be performed using various methods suitable for such processing and known to those skilled in the art. As non-limiting examples, the following three methods may be mentioned: 1) By using a trapping mass. 2) Alternatively, the olefin effluent from the first oligomerization stage c) can be obtained by treating it with alkali and / or acid, with or without alkali neutralization. 3) Alternatively, the olefin effluent obtained from the first oligomerization stage c) may be separated into a first effluent containing at least a portion of C10+ olefin compounds and a homogeneous catalytic system, and a second olefin effluent containing no catalytic system, after which the effluent containing at least a portion of C10+ compounds and the homogeneous catalytic system may be treated by acidic and / or alkaline washing or by using a trapping system.

[0083] For more details on this stage of processing / separating homogeneous catalytic systems, please refer to the specification of patent FR 2 959752.

[0084] Advantageously, the olefin effluent that has been optionally processed / separated from the homogeneous catalytic system at stage c') is sent to an optional separation stage c''), which is capable of separating the olefin effluent obtained from the first oligomerization stage c) or from stage c') of the homogeneous catalytic system into an olefin effluent containing at least a compound having a carbon number greater than or equal to 4 (C4+) and at least a light C2 olefin effluent.

[0085] The separation stage c'') can be advantageously carried out by any method known to those skilled in the art, such as one or more high-pressure and / or low-pressure and high-temperature and / or low-temperature separation drums (knockout drums), and / or a combination of distillation stages comprising one or more distillation columns.

[0086] Light C2 olefin effluents are understood to refer to effluents that advantageously contain at least 50% by weight, preferably at least 65% by weight, of an olefin compound having fewer than 4 carbon atoms.

[0087] Advantageously, a portion, preferably all, of the light C2 olefin effluent is recycled to the first oligomerization stage c).

[0088] An olefinic effluent containing a compound having 4 or more carbon atoms (or a C4+ olefinic effluent) is understood to mean an effluent advantageously containing at least 80% by weight, preferably at least 90% by weight, an olefinic compound having between 4 and 8 carbon atoms (C4-C8). A C4+ olefinic effluent may also contain an olefinic compound having 10 or more carbon atoms (C10+ compound).

[0089] According to the first alternative, when the olefin effluent obtained from stage c) or c') is subjected to the optional separation stage c''), it is advantageous to send all of the C4+ olefin effluent obtained from the optional separation stage c'') containing C4-C8 olefins and optionally C10+ olefins to the second oligomerization stage d).

[0090] According to the second alternative, while still subjecting the olefin effluent obtained from stage c) or c') to the optional separation stage c''), the C4+ olefin effluent is advantageously separated in the second optional separation stage c''') into an olefin effluent containing at least compounds having a carbon number between 4 and 8 (C4-C8) and an olefin effluent containing at least compounds having a carbon number greater than or equal to 10 (C10+ compounds). In this case, the C4-C8 olefin effluent is advantageously fed to the second oligomerization stage d), and the C10+ olefin effluent is advantageously optionally hydrogenated and fed to the fractionation stage e). This embodiment makes it possible to limit the formation of heavy products (excluding kerosene fractions) and thus increase the yield of kerosene fractions. It also makes it possible to use a smaller reactor in the second oligomerization stage d).

[0091] The C4-C8 olefin effluent is defined as an effluent containing olefin compounds distributed according to the following distribution: at least 50% by weight, and preferably at least 70% by weight, of olefin compounds having a number of carbon atoms between 4 and 8, and less than 50% by weight, and preferably less than 30% by weight, of other olefin compounds, the weight percentages being expressed relative to the total weight of olefins present in the C4-C8 olefin effluent.

[0092] In the same manner, the C10+ olefin effluent is defined as an effluent comprising olefin compounds distributed according to the following distribution: at least 50% by weight, and preferably at least 70% by weight, of olefin compounds having a number of carbon atoms greater than or equal to 10, and also advantageously comprising less than 50% by weight, and preferably less than 30% by weight, of compounds having a number of carbon atoms less than 10, the weight percentages being expressed relative to the total weight of olefins present in the C10+ olefin effluent.

[0093] Therefore, the feedstock at the inlet of the second oligomerization stage d) advantageously comprises at least a portion of: - Without processing / separating the homogeneous catalytic system between the first and second oligomerization stages (stage c') and / or optionally separating stage c''), the entire olefin effluent from the first oligomerization stage (c) is obtained, or - In cases where at least stage c') of the homogeneous catalytic system is treated / separated between the first and second oligomerization stages and / or optional separation stage c''), the entire C4+ olefin effluent separated from the light olefin effluent (C2-C4) (i.e., a portion of the olefin effluent obtained from the first oligomerization stage c), or - In the case where at least one stage c') of the homogeneous catalytic system is treated / separated between the first oligomerization stage and the second oligomerization stage, and / or two successive optional separation stages c'') and c'''), the entire C4-C8 olefin effluent is processed.

[0094] One example of the first oligomerization stage (c) is DimEne-B sold by Axens. ® method.

[0095] Another example of the first oligomerization stage (c) is Dimersol-E sold by Axens. ® method.

[0096] Second oligomerization stage d) The method according to the invention includes a second oligomerization stage d): which causes at least the following oligomers to oligomerize: - A portion of the olefin effluent obtained from stage c). - A fraction of a compound obtained from stage b) that substantially contains at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms.

[0097] The second oligomerization stage d) can produce effluent of the type of middle distillate oil.

[0098] The second oligomerization stage is carried out in the presence of an amorphous or zeolite heterogeneous catalyst.

[0099] According to a preferred embodiment, the catalyst used in the second oligomerization stage d) is an amorphous heterogeneous catalyst comprising an amorphous inorganic material selected from silica-alumina and silica-containing alumina, preferably composed of an amorphous inorganic material selected from silica-alumina and silica-containing alumina.

[0100] According to another preferred embodiment of the invention, the second oligomerization stage d) is carried out in the presence of a zeolite heterogeneous catalyst, i.e., a heterogeneous catalyst containing at least one zeolite, preferably having at least 10 or 12 oxygen atoms in pore openings (10MR or 12MR), and advantageously selected from aluminosilicate zeolites with a total Si / Al molar ratio greater than 10.

[0101] In one embodiment, the catalyst used in the second oligomerization stage d) comprises at least one zeolite selected from the structural types of MFI, MTW, MOR, TON, MEL, MFS, or MTT, used alone or as a mixture.

[0102] In a preferred embodiment, the catalyst used in the second oligomerization stage d) comprises zeolite selected from ZSM-5, ZSM-12, NU-86, mordenite, ZSM-22, NU-10, ZBM-30, ZSM-48, ZSM-11, ZSM-57, IZM-2, ITQ-6 and IM-5 zeolite, used alone or in mixtures, preferably at least one zeolite selected from ZSM-5, NU-10 and ZBM-30 zeolite used alone or in mixtures; very preferably, the zeolite is ZBM-30, and even more preferably, the zeolite is ZBM-30 synthesized in the presence of a triethylenetetramine structural agent.

[0103] The zeolite used in the catalyst used in stage d) of the method according to the invention may advantageously undergo several post-treatments known to those skilled in the art, such as modification by dealuminization or desiliconization according to any dealuminization, external surface passivation or desiliconization method known to those skilled in the art, with the aim of improving its activity and / or its stability.

[0104] According to a very specific embodiment in which silica-alumina is used as a catalyst for the second oligomerization stage d), compared to oligomerization in the presence of other catalysts (e.g., zeolite), the silica-alumina enables the oligomerization specifically of at least a portion of the effluent from stage c) and at least a portion of the fraction from stage b) which substantially contains compounds having at least three carbon atoms, while better controlling the reactivity of olefins, particularly enabling operation at low single-pass conversion levels, and very advantageously optimizing selectivity for the desired olefins. Furthermore, coke formation occurs at a lower amount and slower rate in the presence of silica-alumina compared to the presence of zeolite. Therefore, silica-alumina requires a lower regeneration frequency than zeolite.

[0105] The catalyst used in stage d) of the method according to the invention also advantageously comprises at least one oxide-type matrix, also known as a binder. The matrix is ​​understood to refer to, according to the invention, an amorphous or weakly crystalline matrix.

[0106] The matrix is ​​advantageously selected from clay (e.g., natural clay such as kaolin or bentonite), magnesium oxide, aluminum oxide, silica, silica-alumina, aluminates, titanium oxide, boron oxide, zirconium oxide, aluminum phosphate, titanium phosphate, zirconium phosphate, and charcoal. Preferably, the matrix is ​​selected from alumina, clay, and silica; more preferably, the matrix is ​​selected from alumina; and even more preferably, the matrix is ​​γ-alumina.

[0107] The catalyst used in stage d) of the method according to the invention is advantageously shaped into particles (or granules) of various shapes and sizes. They are advantageously used as cylindrical extrusions or multi-lobed extrusions, such as bilobed, trilobed, or multi-lobed extrusions, whether straight or twisted, but can optionally be manufactured and used as crushed powders, ingots, rings, beads, wheels, or spheres. Preferably, the catalyst is in the form of an extrusion with a size between 1 and 10 mm.

[0108] The second oligomerization stage d) is advantageously carried out in at least one fixed-bed reactor.

[0109] In one embodiment, during the second oligomerization stage d), at least a portion of the gasoline-type fraction obtained from the fractionation stage e) is further oligomerized.

[0110] The second oligomerization stage d) according to the method of the invention is advantageously performed at a temperature between 50°C and 400°C, preferably between 100°C and 350°C, and more preferably between 100°C and 300°C, at an absolute pressure between 2 and 15 MPa, preferably between 2 and 8 MPa, and more preferably between 3 and 8 MPa, and at a time of 0.1 to 10 h. -1 Between, and preferably 0.4 to 5 h -1 It operates at the time-space velocity between these speeds.

[0111] The weight hourly space velocity (WHSV) is defined in this paper as the ratio of the weight flow rate of the “fresh” feedstock entering stage d) to the weight of the catalyst, excluding possible recycling.

[0112] The middle distillate oil-type effluent produced by the second oligomerization stage d) is an olefinic effluent containing at least 80% by weight, and preferably at least 90% by weight, of olefins having more than 4 carbon atoms, and less than 20%, preferably less than 10% of C4 olefins, particularly unconverted C4 olefins (C4 means containing 4 carbon atoms) during the second oligomerization stage d), the weight percentages being expressed relative to the total weight of olefins contained in the resulting middle distillate oil-type effluent.

[0113] The effluent of the middle distillate type advantageously contains up to 50% by weight, and preferably up to 40% by weight, of C4-C8 olefins, and at least 50% by weight, and preferably at least 60% by weight, of C10+ olefins (i.e. containing 10 or more carbon atoms), the weight percentages being expressed relative to the total weight of olefins present in the effluent.

[0114] The method according to the invention is a flexible one because the operating conditions and catalyst selection in the second oligomerization stage d) enable the reaction to be directed toward one or another target product, i.e., in one case toward the production of a hydrocarbon base primarily of the gas oil type, and in another case toward a hydrocarbon base of the kerosene type.

[0115] In cases where a more specific goal is to produce hydrocarbon feedstocks primarily of the gas oil type, the second oligomerization stage d) is advantageously carried out in the presence of a catalyst comprising at least one aluminosilicate-type zeolite having a total Si / Al ratio greater than 10 and a 10 or 12 MR pore structure, at a temperature between 200°C and 300°C, at a pressure between 3 and 7 MPa, and for 0.1 to 5 h. -1 The process takes place at high spacetime speeds.

[0116] In cases where the primary goal is to produce kerosene-type hydrocarbon feedstocks, the second oligomerization stage d) is advantageously carried out in the presence of an amorphous catalyst preferably comprising, and preferably composed of, silica-alumina, at a temperature between 100°C and 300°C, at a pressure between 2 and 6 MPa, and for 0.1 to 5 h. -1 The process takes place at high spacetime speeds.

[0117] An example of the second oligomerization stage d) is Polynaphta sold by Axens. ® method.

[0118] Fractionation stage e) The method according to the invention includes a fractionation stage e) of an effluent of the middle distillate type obtained from stage d).

[0119] The fractionation stage e) is advantageously carried out in at least one distillation column to separate the effluent of the middle distillate oil type into at least two fractions: - Gasoline fraction, - Middle distillate oil fractions (gas oil and / or kerosene).

[0120] It can also separate light effluents containing C2-C4 compounds, thereby upgrading them either in pure form or as a mixture.

[0121] It can also advantageously separate heavy fractions with an initial boiling point between 350°C and 370°C.

[0122] "Gasoline fraction" is understood to refer to fractions containing hydrocarbon compounds with boiling points between room temperature and 220°C.

[0123] "Middle distillate" is understood to refer to distillates containing hydrocarbon compounds with boiling points between 140°C and 360°C.

[0124] At least a portion of the gasoline fraction obtained from fractionation stage e) can be advantageously recycled to the second oligomerization stage d) according to the method of the invention.

[0125] In one embodiment, unconverted C4 olefins from the second oligomerization stage d) are separated from the effluent obtained from stage d) and then recycled to the inlet of the second oligomerization stage d).

[0126] Since one of the objectives of the present invention is to maximize the yield of middle distillate oil base, preferably kerosene base, the unwanted light effluents (containing C2-C4 compounds) and gasoline fractions (corresponding to C4-C8 compounds) are advantageously oligomerized again in stages c) and d) of the method according to the invention, respectively, so as to increase their molecular weight and thus their boiling point and their compatibility with the desired use.

[0127] Advantageously, at least a portion, preferably all, of the middle distillate oil fractions (gas oil and / or kerosene) obtained from fractionation stage e) are subjected to an optional olefin hydrogenation stage f) so that they can be incorporated into the fuel pool. Preferably, at least a portion, preferably all, of the middle distillate oil fractions (gas oil and / or kerosene) obtained from fractionation stage e) are contacted with a hydrogen-rich gas in the presence of a catalyst comprising at least one Group VIII metal (advantageously selected from palladium and nickel, used alone or in a mixture) and a support (advantageously selected from alumina, silica, or silica-alumina).

[0128] The catalyst used in the optional hydrogenation stage f) comprises a palladium content that is advantageously between 0.1% and 10% by weight relative to the total weight of the catalyst and / or a nickel content that is advantageously between 1% and 60% by weight.

[0129] The optional hydrogenation stage f) is advantageously carried out at the reactor inlet at a temperature between 100°C and 250°C, a pressure between 2 and 5 MPa, and for 0.05 to 8 h. -1 The process takes place at high spacetime speeds.

[0130] Hydrogenation performance is confirmed by measuring the bromine value, which is advantageously up to 5 g Br / 100 g when it is desirable to saturate all unsaturated compounds present in the fraction to be hydrogenated.

[0131] The effluent obtained from the optional hydrogenation stage f) mainly contains hydrocarbons that can be upgraded and incorporated into the kerosene pool and / or gas oil pool, preferably from the kerosene pool.

[0132] The optional final separation stage g) can advantageously be carried out after the optional hydrogenation stage f) to fractionate the effluent from stage f) into kerosene fractions and / or gas oil fractions and / or fractions with boiling points above 360°C.

[0133] "Gas oil" fraction is understood to refer to fractions containing hydrocarbon compounds with boiling points between 220°C and 360°C.

[0134] The term "kerosene" fraction is understood to refer to fractions containing hydrocarbon compounds with boiling points between 140°C and 300°C.

[0135] According to one embodiment, at least a portion of the effluent obtained from an optional hydrogenation stage f) can be advantageously recycled to a first oligomerization stage c) to form a diluent for the feedstock of stage c) and thereby stabilize the catalyst.

[0136] When the required fuel is kerosene, the olefin hydrogenation stage is necessary. Example

[0137] Example: Method for producing middle distillate oil from ethanol feedstock: Stage a): Dehydration of raw materials The raw material is bioethanol with the following characteristics: Sugarcane ethanol contains 92% by weight ethanol, 500 ppm by weight organic impurities (heavy alcohols, methanol, esters, acids), and the remainder is water.

[0138] This raw material was subjected to zeolite catalyst PZSM-5 at a temperature of 400°C, a pressure of 0.6 MPa, and a temperature of 7 h. -1 Dehydration at heavy hourly space velocity.

[0139] The composition of the dehydrated effluent is given in the table below: Table 1 .

[0140] The C3+ compounds consist of 74.3% by weight of olefins (20.1% propylene, 45.4% butene, and 8.8% C5-C6 olefins), 19.9% ​​by weight of alkanes (13.5% C3-C4 alkanes and 6.4% C5-C6 alkanes), and 5.9% of aromatic compounds.

[0141] Separation phase b) The effluent, after drying, compression, and removal of CO, CO2, and acetaldehyde using a trap and molecular sieves (mass deoxo with Cu / Zn, 3A, and 13X sieves), was introduced into a cryogenic distillation column at 2.28 MPa. This column used structured packing with a height equal to 40 theoretical plates. At the top of the column, at -22°C, an ethylene-rich fraction was produced, containing trace amounts of propylene. The bottom fraction was separated in a second distillation column (20 theoretical plates) at 0.7 MPa and a top temperature of 30°C to produce a top fraction rich in C3-C5 compounds (and ethylene-free) and a bottom fraction rich in aromatic compounds. The top fraction from the second column was sent to the oligomerization stage (d); the bottom fraction, in our case, was used as fuel in the furnace of this method. The composition of the top fraction was as follows: Table 2 .

[0142] First oligomerization stage c) The ethylene-rich fraction obtained from separation stage b) is fed to the first oligomerization stage c), which is operated at 50°C and 1 MPa in the presence of a homogeneous catalyst containing divalent nickel compounds and an ethylaluminum dichlorocatalyst (EADC). The Al / Ni molar ratio is set to 15.

[0143] The following table shows the composition of C4+ compounds from the olefinic effluent obtained from stage c): Table 3 .

[0144] The selectivity of different fractions is as follows: - 41% by weight of C4 olefins - 35% by weight of C6 olefins - 14.5% by weight of C8 olefins - 9.5% by weight of C10+ olefins.

[0145] The effluent at the outlet of stage c) is separated into two fractions: - Fractions containing C4, C6, and C8 olefins are sent to stage d); - The fraction containing C10+ olefins is sent to stage f).

[0146] Second oligomerization stage d) In case 1 (a comparative example based on the prior art), the fraction containing C4, C6 and C8 olefins obtained from the first oligomerization stage c) is sent to stage d).

[0147] In case 2 (according to the invention), the fraction containing C4, C6 and C8 olefins obtained from the first oligomerization stage c) is sent together with the fraction rich in C3-C5 compounds obtained from the separation stage b) to stage d).

[0148] The second oligomerization stage d) was carried out in the presence of an aluminosilicate heterogeneous catalyst at a temperature of 110 °C, an absolute pressure of 6.0 MPa, and a time of 0.2 h. -1 It operates at a spacetime speed.

[0149] The effluent from the second oligomer was separated into two fractions in the first column: - The C4 fraction is recycled to the inlet of stage d) or leaves the method as a bleed. - The C6+ fraction is sent to the second column. The C6+ fraction obtained from the first column is separated into two fractions in the second column: - The C6-C8 fraction is recycled to the inlet of stage d) or leaves the method as a bleed. - Oligomers, which are then sent to stage e) The recycling ratio of the C6-C8 fraction from fractionation stage e) to the feedstock entering stage d) is 3.5.

[0150] The recycling ratio of C4 that was not converted in stage d) and separated in stage e) to the feedstock entering stage d) is 1.5.

[0151] The composition of the effluent obtained from the second oligomerization stage is described in the table below: Table 4 .

[0152] Hydrogenation and fractionation (e): The oligomer obtained in stage d) is hydrogenated together with the fraction containing C10+ olefins obtained from the first oligomerization stage c). This stage is carried out at a temperature of 180 °C, a pressure of 1.5 MPa, and a time of 0.5 h. -1 The process was carried out using a Ni-alumina catalyst at a space velocity of [value missing].

[0153] The hydrogenated effluent is sent to a fractionation tower where kerosene and gas oil fractions are recovered.

[0154] The fuel yields from the effluent obtained from the dehydrogenation and fractionation stage (e) are described in the table below: Table 5 .

[0155] The overall yield of this method is described in the table below: Table 6 .

[0156] Therefore, it was observed that the method according to the invention, including sending the C3+ compound obtained from the dehydration stage a) to the second oligomerization stage d), could achieve better kerosene yield (+3.8% = 54.3% - 50.5% by weight of the input feedstock of the method) and, to a lesser extent, better gas oil yield (+0.2% = 2.6% - 2.4% by weight of the input feedstock of the method).

Claims

1. A method for producing a hydrocarbon feedstock of the middle distillate oil type, and preferably a kerosene hydrocarbon feedstock, from an alcohol feedstock comprising at least one monool, preferably ethanol, the method comprising: a) A dehydration stage comprising at least one monool, preferably ethanol, of an alcohol feedstock, and producing at least a dehydrated effluent comprising: - On a dry basis, relative to the total weight of the effluent, at least 80% by weight, preferably at least 85% by weight, and preferably at least 90% by weight, of ethylene. - Compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms. The dehydration stage is carried out in the presence of an acidic amorphous catalyst or an acidic zeolite catalyst; b) The stage of separating the dehydrated effluent obtained in stage a), and producing at least: - Essentially contains the fraction of ethylene. - A fraction that essentially contains compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and more preferably 3 to 6 carbon atoms; c) First oligomerization stage: which oligomerizes at least a portion of the fraction obtained from stage b) which substantially contains ethylene, and produces at least an olefin effluent containing at least 80% by weight of an olefin having a carbon number greater than or equal to 4 relative to the total weight of the olefins contained in the olefin effluent, wherein the first oligomerization stage is carried out in the presence of a homogeneous catalyst. d) Second oligomerization stage: which causes at least the following oligomerizations: - A portion of the effluent obtained from stage c). - A portion of a fraction obtained from stage b) that substantially contains compounds having at least 3 carbon atoms, preferably 3 to 9 carbon atoms, and preferably 3 to 6 carbon atoms, and produces an effluent of the middle distillate oil type. The second oligomerization stage is carried out in the presence of an amorphous or zeolite heterogeneous catalyst; e) The fractionation stage of the effluent of the middle distillate type obtained from stage d).

2. The method of claim 1, wherein, on a dry basis, the dehydrated effluent contains at least 1% by weight, preferably at least 5% by weight, and preferably at least 8% by weight, of a compound having at least 3 carbon atoms, preferably having 3 to 9 carbon atoms, and preferably having 3 to 6 carbon atoms, relative to the total weight of the effluent.

3. The method according to any one of the preceding claims, wherein the compound having at least 3 carbon atoms, preferably having 3 to 9 carbon atoms, and preferably having 3 to 6 carbon atoms comprises an olefin, preferably at least 50% by weight, preferably at least 60% by weight, and most preferably at least 70% by weight of the olefin relative to the total weight of the compound having at least 3 carbon atoms.

4. The method according to any one of the preceding claims, wherein the fraction obtained from stage b) which substantially comprises a compound having at least 3 carbon atoms is subjected to an additional separation stage to obtain at least: - Essentially an olefin fraction containing olefins with 3 to 6 carbon atoms. - Heavy fraction, which contains aromatic compounds, preferably having 6 to 9 carbon atoms.

5. The method according to claim 4, wherein the heavy fraction is advantageously subjected to a selective hydrogenation stage of the unsaturated olefins or dienes contained in the fraction, and the resulting effluent is then sent to the fractionation stage e).

6. The method according to any one of the preceding claims, wherein the olefin effluent obtained from the first oligomerization stage c) contains less than 20% by weight, preferably less than 10% by weight, of ethylene, the percentage being expressed as a weight percentage relative to the total weight of the olefins contained in the generated olefin effluent.

7. The method according to any one of the preceding claims, wherein the homogeneous catalyst used in the oligomerization stage c) comprises: - At least one nickel precursor in the (+II) oxidation state, - and at least one activator selected from chlorinated and brominated hydrocarbon aluminum compounds used alone or in mixtures.

8. The method according to any one of the preceding claims, wherein the olefin effluent obtained from stage c) is sent to separation stage c''), which is capable of separating the olefin effluent obtained from the first oligomerization stage c) into an olefin effluent comprising at least a compound having a carbon number greater than or equal to 4 and at least a light C2 olefin effluent.

9. The method of claim 8, wherein a portion, preferably all, of the light C2 olefin effluent is recycled to the first oligomerization stage c).

10. The method according to claim 8 or 9, wherein the olefinic effluent containing a compound having a carbon number greater than or equal to 4 is separated in a second separation stage (c''') into an olefinic effluent containing at least a compound having a carbon number between 4 and 8 and an olefinic effluent containing at least a compound having a carbon number greater than or equal to 10.

11. The method of claim 10, wherein the olefinic effluent comprising a compound having a carbon number greater than or equal to 10 is hydrogenated and sent to fractionation stage e).

12. The method according to any one of the preceding claims, wherein the effluent of the middle distillate type produced by the second oligomerization stage d) is an olefinic effluent containing at least 80% by weight, and preferably at least 90% by weight, of olefins having more than 4 carbon atoms, and less than 20%, preferably less than 10%, of C4 olefins, the weight percentages being expressed relative to the total weight of olefins contained in the produced middle distillate type effluent.

13. The method according to any one of the preceding claims, wherein the fractionation stage e) is carried out in at least one distillation column to separate the effluent of the middle distillate oil type obtained from stage d) into at least two fractions: - Gasoline fraction, - Middle distillate oil fraction.

14. The method of claim 13, wherein at least a portion, preferably all of, of the middle distillate fraction obtained from said fractionation stage e) undergoes olefin hydrogenation stage f).

15. The method according to any one of the preceding claims, wherein unconverted C4 olefins during the second oligomerization stage d) are separated from the effluent obtained from stage d) and then recycled to the inlet of the second oligomerization stage d).