PROCESS FOR PRODUCING MIDDLE DISTILLATES, IN PARTICULAR KEROSENE, FROM AN ALCOHOL CHARGE

Abstract

The present invention relates to a process for producing hydrocarbon bases of the middle distillate type from an alcoholic feedstock, said process comprising the following steps: a) dehydration of the alcoholic feedstock, and obtaining at least one dehydration effluent comprising: - at least 80% by weight of ethylene, relative to the total weight of the effluent considered dry, - compounds having at least 3 carbon atoms, carried out in the presence of an amorphous acid catalyst or zeolitic acid; b) separation of the dehydration effluent obtained in step a) and obtaining at least: - a fraction comprising essentially ethylene, - a fraction comprising essentially compounds having at least 3 carbon atoms;c) oligomerization of at least a portion of the fraction consisting essentially of ethylene from step b) and obtaining at least one olefinic effluent comprising at least 80% by weight of olefins having a number of carbon atoms greater than or equal to 4, relative to the total mass of olefins contained in said olefinic effluent, carried out in the presence of a homogeneous catalyst; d) oligomerization of at least: - a portion of the effluent from step c), - a portion of the fraction consisting essentially of compounds having at least 3 carbon atoms from step b), and obtaining a middle distillate type effluent, carried out in the presence of a heterogeneous amorphous or zeolitic catalyst; e) fractionation of the middle distillate type effluent from step d).;

Description

Title of the invention: METHOD FOR PRODUCING MIDDLE DISTILLATES, IN PARTICULAR KEROSENE, FROM AN ALCOHOL CHARGE technical field

[0001] The present invention relates to the transformation of an alcoholic feedstock, and more particularly an ethanol feedstock, preferably bioethanol, into middle distillates, in particular into diesel and / or kerosene fuel bases, using a process comprising a feedstock dehydration step and two successive oligomerization steps. Prior art

[0002] Demand for the use of biomass as at least a partial replacement for petroleum resources in fuel synthesis is increasing. Thus, the use of bioethanol for the synthesis of fuel bases is receiving growing interest.

[0003] Bioethanol is ethanol of agricultural origin, that is to say that it is produced from a renewable source derived from biomass such as, for example, living plant matter.

[0004] Most bioethanol is produced today by fermenting the sugars contained in plant-based raw materials. From sugar plants, the first step in the transformation process consists of obtaining a sugary juice by hot water extraction for sugar beets or by crushing and pressing for sugar cane. After possible concentration, these juices or syrups are introduced into fermenters where the biological transformation of sugars into ethanol takes place, with the co-production of CO2 under the action of microorganisms (yeast). The resulting wines contain approximately 10% alcohol in water. A distillation step allows the azeotropic composition of the ethanol / water binary (8% water) to be achieved. In order to obtain complete dehydration, passage through a molecular sieve is necessary.In cereal plants (maize, wheat), fermentable sugars that can be converted into ethanol are present in the form of a polymer called starch; to release them, a prior step of enzyme-catalyzed hydrolysis is necessary.

[0005] Technologies enabling the transformation of lignocellulosic biomass (wood, grass, straw and other agricultural waste, etc.) into bioethanol have also recently become available. These technologies allow the use of resources that do not compete with human or animal food (in the sense of livestock farming).

[0006] There are also technologies for obtaining ethanol from waste gases from steelmaking or municipal solid waste incineration, using a gasei processing of this waste followed by microbial fermentation using CO and some of the CO2 from the gas, and nutrients for microorganisms.

[0007] The use of ethanol is primarily intended for the production of gasoline, and not for the production of diesel and kerosene. Another very promising avenue is the use of ethanol as a biofuel in diesel engines. E-Diesel biofuel is a mixture consisting of diesel between 85% and 95%, anhydrous (water-free) ethanol, and an additive package specifically designed to stabilize the mixture and overcome some of the drawbacks of bioethanol, such as its low cetane number and poor lubricating properties.

[0008] Blending conventional diesel with ethanol and the additive improves combustion efficiency and slightly increases fuel volatility. The main result is a reduction in emissions of regulated pollutants such as particulate matter (PM10) and smoke. This reduction is due to the oxygen content of the biofuel, which limits particulate formation during fuel combustion. These oxygenated molecules significantly improve combustion quality by providing an oxidant at the precise site of the oxidation reaction. The main drawback of blending bioethanol with diesel is that it lowers the flash point.

[0009] Mixing conventional jet fuel (called Jet Al in the customs specification) with ethanol is not accepted by equipment manufacturers in the current commercial specification (ASTM D7566), primarily due to issues of flammability (flash point), stability, water absorption, and energy content per liter. These drawbacks suggest that even if it is possible to fly small aircraft on ethanol, its use in existing fleets would not be straightforward.

[0010] The transformation of ethanol into hydrocarbons is therefore an interesting way to valorize renewable resources towards fuels.

[0011] There is a very rich literature on the transformation of alcohols, for example of the methanol type, into olefins or aromatics to produce a gasoline cut on acid catalysts, often zeolitic.

[0012] The production of ethylene from ethanol is a known process, which has been developed on an industrial scale in a few units. For example, ethanol-to-ethylene dehydration units were built in Brazil during the 1970s, following the oil crisis. Ethanol is catalytically converted into ethylene starting at 300°C. The catalysts used can be of different types: activated alumina, silica alumina, etc.

[0013] Scientific Design has developed its own technology for dehydrating ethanol into ethylene and following the development of a new catalyst, introduced on an industrial unit published an article ("Ethylene from Ethanol", NK Kochar, R. Merims, and AS Padia, CEP, June 1981). US patents 4,232,179, US 4,396,789, US 4,234,752, US 4,396,789, US 4,698,452 may also be cited.

[0014] Documents FR2959750 and FR2959752, in the name of IFPEN, disclose processes for producing middle distillate hydrocarbon bases from an ethanol feedstock, comprising ethanol dehydration steps followed by two oligomerization steps, respectively in homogeneous and heterogeneous phases. Patent US9840676, for its part, discloses a process for converting ethanol into diesel and / or kerosene by dehydration, conversion of the resulting ethylene to hexene, and then di- or tri-merization, to obtain a mixture comprising C12 hydrocarbon compounds. These documents do not disclose any step for recovering value from compounds having three or more carbon atoms (C3+) in the dehydration effluent, which are considered undesirable.

[0015] An objective of the present invention is therefore to provide a process for producing middle distillate hydrocarbon bases (diesel and / or kerosene) and preferably kerosene bases incorporable into the fuel pool, from an alcoholic feedstock, preferably ethanol, produced from a renewable source from biomass also called bioethanol, with a yield superior to prior art processes.

[0016] The applicant has demonstrated, surprisingly, that by utilizing the C3+ compounds formed during the dehydration step of the alcoholic feedstock, by sending them to the heterogeneous phase oligomerization step, the yield of olefins of interest is increased (by approximately 0.5 to 10% of the carbon yield of the transformation) for obtaining middle distillates and, more specifically, kerosene. The advantages are primarily economic, by utilizing compounds that were initially undesirable at the end of the dehydration process. Summary of the invention

[0017] The present invention relates to a process for producing hydrocarbon bases of the middle distillate type, preferably kerosene-based, from an alcoholic feedstock comprising at least one mono-alcohol, preferably comprising ethanol, said process comprising:

[0018] a) a dehydration step of the alcoholic load comprising at least one mono-alcohol, preferably comprising ethanol, and obtaining at least one dehydration effluent comprising:

[0019] - at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight of ethylene, relative to the total weight of the effluent considered dry,

[0020] - compounds having at least 3 carbon atoms (C3+), preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms,

[0021] said dehydration step being carried out in the presence of an amorphous acid catalyst or a zeolitic acid catalyst;

[0022] b) a step of separating the dewatering effluent obtained in step a) and obtaining at least:

[0023] - a fraction comprising essentially ethylene,

[0024] - a fraction comprising essentially compounds having at least 3 atoms of carbon, preferably having between 3 and 9 carbon atoms, preferably between 3 and 6 carbon atoms;

[0025] c) a first oligomerization step of at least a part of the fraction consisting essentially of ethylene from step b) and obtaining at least one olefinic effluent comprising at least 80% by weight of olefins having a number of carbon atoms greater than or equal to 4, relative to the total mass of olefins contained in said olefinic effluent, said first oligomerization step being carried out in the presence of a homogeneous catalyst;

[0026] d) a second oligomerization step of at least:

[0027] - part of the effluent from step c),

[0028] - a portion of the fraction comprising essentially compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably between 3 and 6 carbon atoms, from step b), and obtaining a middle distillate type effluent,

[0029] said second oligomerization step being carried out in the presence of a heterogeneous amorphous or zeolitic catalyst;

[0030] e) a fractionation step of the middle distillate type effluent from step d).

[0031] The term "considered dry" means the effluent ideally separated from the water produced during the dehydration reaction and / or from any solvents added in addition to the alcohol load before the dehydration step. DETAILED DESCRIPTION OF THE INVENTION

[0032] 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 in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such clarification will be provided by the present invention.

[0033] 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.

[0034] In the following, particular embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation of combinations where technically feasible. Charge

[0035] According to the invention, the feed treated in the process according to the invention is an alcoholic feed (or an alcohol feed), containing at least one mono-alcohol. Preferably, said mono-alcohol is ethanol.

[0036] Advantageously, said alcohol feed of the process according to the invention comprises at least 35% by weight of said mono-alcohol, preferably from 35% by weight to 99.9% by weight of said mono-alcohol. Said alcohol feed may also comprise between 0 and 65% water. Said alcohol feed may further comprise mineral impurities (such as Na, Ca, P, Al, Si, K, SO4), organic impurities such as a mono-alcohol other than the mono-alcohol of interest, for example methanol or n-butanol in an ethanolic feed, aldehydes, ketones, and the corresponding acids, for example furanic, acetic, isobutyric acid. The said alcoholic load may also include, in particular, inorganic nitrogenous and / or sulfurous compounds, such as ammonia, or organic nitrogenous and / or sulfurous compounds, preferably basic, such as amines, amides, imines and sulfurous compounds (thiol, thiophenes, mercaptans, thioethers, sulfides, disulfides, etc.).The nitrogen and sulfur content, of organic and mineral origin, of said alcoholic feedstock are preferably each less than or equal to 0.5% by weight, preferably less than or equal to 0.2% by weight, the weight percentages being expressed relative to the total weight of said alcoholic feedstock. According to the invention, nitrogen content and sulfur content refer to the elemental nitrogen and elemental sulfur content respectively contributed by the nitrogen and sulfur impurities present in the streams considered, particularly in said alcoholic feedstock of the process of the invention. Preferably, the elemental nitrogen content is advantageously determined by combustion and detection by chemiluminescence, and the elemental sulfur content is determined by combustion and detection by UV fluorescence.

[0037] Advantageously, said alcoholic feedstock can be derived from non-fossil resources. Preferably, the alcoholic feedstock treated in the process according to the invention is produced from renewable resources derived from biomass, preferably by fermentation of sugars from, for example, sugar crops such as sugarcane (sucrose, glucose, fructose, and sucrose), beets, or starchy plants (starch), or from lignocellulosic biomass or hydrolyzed cellulose (predominantly glucose and xylose, galactose), containing variable amounts water. For a more complete description of classic fermentation processes, see the book 'Biofuels, Current state, perspectives and challenges of development, Daniel Ballerini, Editions Technip'.

[0038] Said alcoholic charge can also advantageously be obtained from synthesis gas.

[0039] The alcohol charge treated in the process according to the invention can also optionally be obtained by a process of synthesizing alcohol from fossil resources such as, for example, from coal, natural gas or carbonaceous waste.

[0040] The alcoholic charge of the process according to the invention can also be obtained by hydrogenation of the corresponding acids or esters. In this case, the acetic acid or acetic esters are advantageously hydrogenated using hydrogen in ethanol. Acetic acid can, for example, be obtained by carbonylation of methanol or by fermentation of carbohydrates.

[0041] Preferably, the alcohol feed treated in the process according to the invention is an alcohol feed produced from renewable resources derived from biomass, more particularly from bioethanol.

[0042] In one embodiment, the alcohol load may undergo a pretreatment step so as to produce a pretreated alcohol load.

[0043] This pretreatment step is advantageously carried out on at least one acidic solid. This acidic solid can be chosen from among all solids known to those skilled in the art. It can thus be selected from the group consisting of: acidic clays, zeolites, sulfated zirconias, acidic resins, etc. For example, this acidic solid can be chosen from commercially available acidic solids, such as clays treated with acids to make them acidic (such as montmorillonite) and preferably zeolites having a silica-to-alumina molar ratio in the crystal lattice of 2.5 to 100.

[0044] Preferably, said acidic solid is an acidic resin, in particular an ion-exchange resin, preferably a cation-exchange resin, in particular one having an exchange capacity (or acid strength) of at least 0.1 mmol H+ equivalent per gram, the exchange capacity (or acid strength) being determined by titration, preferably by conductimetry, of the H+ ions released by the acidic resin after exchange with Na+ ions (see in particular ASTM D4266). For example, the acidic solid is a commercial acidic resin sold under the reference TA801 by the company Axens.

[0045] Advantageously, said pretreatment step makes it possible to trap and thus eliminate cationic and possibly anionic impurities, basic, complexing, chelating impurities, inorganic or organic impurities, in particular metallic salts (such as salts of K, Na, Ca, Fe, Cu, P, Cl) and nitrogenous and / or impurities sulfur compounds, such as basic nitrogen compounds present in the charge, for example in the form of ammonia and / or in the form of organic and basic species, for example in the form of amine, amide, imine or nitrile.

[0046] Advantageously, the alcohol load is pre-treated according to the teachings of application FR3090393. Operating conditions and catalysts

[0047] Step a) of dehydration

[0048] The process according to the invention comprises a step a) of dehydrating the alcoholic feed containing at least one mono-alcohol, preferably containing ethanol, and obtaining at least one dehydration effluent comprising:

[0049] - at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight of ethylene, relative to the total weight of the effluent considered dry.

[0050] - compounds having at least 3 carbon atoms (C3+), preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, said dehydration step being carried out in the presence of an amorphous acid catalyst or a zeolitic acid catalyst.

[0051] Non-limiting examples of compounds having 3 or more carbon atoms are olefins, for example: propylene, linear butene, isobutene, methyl butene and methyl pentene; aromatics such as: toluene and xylene, and paraffins for example: propane, butane, pentane, hexane.

[0052] Advantageously, the dewatering effluent comprises at least 1% by weight, preferably at least 5% by weight, preferably at least 8% by weight of compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, relative to the total weight of the dry effluent. Very advantageously, the dewatering effluent has a content of said compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, of less than 20% by weight, preferably less than 15% by weight, preferably less than 10% by weight relative to the total weight of the dry effluent.

[0053] Advantageously, compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, comprise olefins, preferably at least 50% by weight, preferably at least 60%, preferably at least 70% by weight of olefins relative to the total weight of compounds having at least 3 carbon atoms.

[0054] In one embodiment, the dewatering effluent comprises, in addition to olefins, aromatic compounds, preferably between 1 and 10% by weight of aromatic compounds relative to the total weight of compounds having at least 3 carbon atoms.

[0055] In the case where the catalyst used in dehydration step a) is a zeolite catalyst, said catalyst comprises at least one zeolite selected from among zeolites having at least pore openings containing 8, 10, or 12 oxygen atoms (8 MR, 10 MR, or 12 MR). It is known to define the pore size of zeolites by the number of oxygen atoms forming the annular cross-section of the zeolite channels, called "member ring" or MR. Preferably, said zeolite dehydration catalyst comprises at least one zeolite having a structural type selected from among the structural types MFI, FAU, MOR, FER, SAPO, TON, CHA, EUO, MEL, and BEA. Preferably, said zeolite dehydration catalyst comprises a structural MFI type zeolite and preferably a ZSM-5 zeolite.

[0056] Said zeolite can advantageously be modified by desalumination or desilication according to any desalumination or desilication method known to a person skilled in the art.

[0057] Said zeolite can advantageously be modified by an agent capable of attenuating its total acidity and improving its hydrothermal resistance properties. Preferably, said zeolite or said catalyst advantageously comprises phosphorus, preferably added in the form of H3PO4 followed by steam treatment after neutralization of excess acid by a basic precursor such as, for example, calcium (Ca). Preferably, said zeolite comprises a phosphorus content of between 1 and 4.5 wt%, preferably between 1.5 and 3.1 wt% relative to the total weight of the catalyst.

[0058] In the case where the catalyst used in step a) of dehydration is an amorphous acid catalyst, said catalyst comprises at least one porous refractory oxide selected from alumina, alumina activated by a mineral acid deposition and silica alumina.

[0059] The amorphous or zeolitic dehydration catalyst used in step a) of the process according to the invention may advantageously also comprise at least one oxide-type matrix, also called a binder. A matrix according to the invention is understood to be an amorphous or poorly crystallized matrix.

[0060] Said 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 said matrix is ​​chosen from among the elements of the group formed by aluminas, silicas, and clays.

[0061] The dehydration catalyst used in step a) of the process according to the invention is advantageously shaped into grains of various shapes and sizes. It is advantageously used in the form of cylindrical or multilobed extrudates such as bilobed, trilobed, or multilobed, straight or twisted, but can optionally be manufactured and used in the form of crushed powder, tablets, rings, balls, wheels, spheres, or stars. Preferably, said catalyst is in the form of extrudates or balls.

[0062] Step a) of dehydration of the process according to the invention advantageously operates at a temperature between 250 and 600°C, preferably between 300 and 600°C and preferably between 300 and 500°C, at an absolute pressure between 0.1 and 5 MPa, preferably between 0.1 and 2.5 MPa and preferably between 0.1 and 1 MPa, and preferably at an hourly weight rate between 0.1 and 50 h⁻¹ and preferably between 0.5 and 15 h⁻¹

[0063] The hourly weight velocity is defined as the ratio of the mass flow rate of the feed entering at step a) to the mass of catalyst.

[0064] The conversion of the alcohol load in step a) is advantageously greater than 90%, preferably 95% and preferably greater than 98%.

[0065] The conversion of the alcohol load means the ratio of the difference between the mass flow rate of the alcohol load at the inlet and the mass flow rate of the alcohol load at the outlet of step a) to the mass flow rate of the alcohol load at the inlet, said ratio being expressed as a percentage.

[0066] Advantageously, prior to step b) of separation, the water present in the dehydration effluent is separated by any method known to a person skilled in the art.

[0067] Step a) of dehydration can advantageously be implemented according to the teachings of applications WO2014083260 or WO2014083261.

[0068] An example of a process for dehydrating an alcoholic load is the Atol® process marketed by the company Axens.

[0069] Step b) of separation

[0070] The process according to the invention comprises a step b) of separating the dewatering effluent obtained in step a) and obtaining at least:

[0071] - a fraction comprising essentially ethylene,

[0072] - a fraction comprising essentially compounds having at least 3 atoms of carbon, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms.

[0073] The term "essentially" means comprising at least 95% by weight, preferably at least 97% by weight, preferably at least 99% by weight of desired compounds relative to the total weight of the fraction considered.

[0074] Advantageously, compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, comprise olefins, preferably at least 50% by weight, preferably at least 60%, preferably at least 70% by weight of olefins relative to the total weight of compounds having at least 3 carbon atoms.

[0075] In a particular embodiment of the invention, the fraction comprising essentially compounds having at least 3 carbon atoms undergoes an additional separation step to obtain at least:

[0076] - an olefinic fraction comprising essentially olefins having between 3 and 6 carbon atoms,

[0077] - a heavy fraction comprising aromatics, preferably having between 6 and 9 carbon atoms.

[0078] In this particular embodiment, it is the olefinic fraction, consisting essentially of olefins having between 3 and 6 carbon atoms, that is sent to step d) of second oligomerization. The heavy fraction, comprising aromatics, preferably having between 6 and 9 carbon atoms, may also include unsaturated olefinic or diolefinic compounds, preferably having between 6 and 9 carbon atoms. This heavy fraction advantageously undergoes a step of selective hydrogenation of the unsaturated olefinic or diolefinic compounds contained therein, and the resulting effluent is then sent to step e) of fractionation. The selective hydrogenation step of the heavy fraction allows for its purification in order to improve its oxidation stability. Indeed, the presence of heavy olefins makes the heavy fraction susceptible to peroxidation, ultimately leading to the presence of gums in the final fuel.

[0079] Step b) of separation can be carried out by any method known to those skilled in the art, for example by distillation, in particular continuous distillation, successive distillations, or continuous or batch multi-cut distillations, possibly with lateral drawing off to extract the intermediate boiling cut. Columns with internal walls can also be used to carry out this separation while reducing energy consumption. Molecular sieves or separation membranes can also be used as a complement to or replacement for distillation methods.

[0080] Preferably, the dewatering effluent from step a) undergoes at least one purification step prior to the separation step b). This purification step makes it possible to remove impurities harmful to the oligomerization catalysts used for the implementation of steps c) and d) placed downstream and in particular makes it possible to remove oxygenated compounds present in said dewatering effluent.

[0081] The optional purification step may advantageously be carried out using any method known to those skilled in the art, such as, for example, the successive combination of treatment in a water scrubbing column, followed by passage through an absorption column with MDEA (methyldiethylamine) or another amine, and then through a sodium hydroxide scrubbing column, or any other method known to those skilled in the art. Dryers may advantageously be used to achieve a water content compatible with the oligomerization catalysts used downstream in oligomerization steps d) and e). The water content of the fraction sent to the first oligomerization step c) is advantageously between 0 and 500 ppm, and preferably less than 100 ppm, most preferably less than 1 ppm.

[0082] Step c) of first oligomerization

[0083] The process according to the invention comprises a first step c) of oligomerizing at least a portion of the fraction consisting essentially of ethylene from step b) and obtaining at least one olefinic effluent comprising at least 80% by weight, preferably 90% by weight of olefins having a number of carbon atoms greater than or equal to 4 (C4+), relative to the total mass of olefins contained in said olefinic effluent, said first oligomerization step being carried out in the presence of a homogeneous catalyst.

[0084] Advantageously, at least a part, i.e. at least 50% by weight, preferably at least 90% by weight of the fraction comprising essentially ethylene from step b) and preferably the whole of said fraction is subjected to said first oligomerization step.

[0085] Advantageously, said olefinic effluent from said first oligomerization step c) comprises less than 20% by weight, preferably less than 10% by weight of ethylene not having reacted during the first oligomerization step c), the percentages being expressed as percentages by weight relative to the total mass of olefins contained in said olefinic effluent produced.

[0086] In a particular embodiment, said olefinic effluent is rich in olefinic hydrocarbons having a number of carbon atoms between 4 and 8 and also comprises olefinic hydrocarbons having at least 10 carbon atoms (C10+). More particularly, said olefinic effluent produced during the first oligomerization step c), advantageously comprises at least 80% by weight, preferably at least 90% by weight, of olefinic compounds having predominantly a number of carbon atoms between 4 and 8 and less than 20% by weight, and preferably less than 10% by weight, of olefinic compounds having predominantly a number of carbon atoms greater than or equal to 10, the weight percentages being expressed relative to the total mass of olefins contained in said olefinic effluent produced.

[0087] According to step c) of the process according to the invention, the catalyst used in the first oligomerization step c) is a homogeneous catalyst, that is to say that the catalyst is soluble in the liquid phase composed of dissolved ethylene and its oligomerization products.

[0088] Advantageously, the homogeneous catalyst used in step c) of oligomerization of the process according to the invention comprises:

[0089] - at least one nickel precursor with oxidation state (+11),

[0090] - and at least one activating agent chosen from the group formed by the compounds Chlorinated and brominated hydrocarbonaluminum, taken alone or in mixtures.

[0091] Optionally, the homogeneous catalyst used in step c) 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 PR1R2R3 in which the RI, R2 and R3 groups, identical or different from each other, are linked or not to each other.

[0092] Nickel compounds with an oxidation state of (+11) are preferably compounds soluble at more than one gram per liter in hydrocarbon medium, and more particularly in the reactants and reaction medium, and preferably nickel carboxylates of the general formula (RCOO)2Ni 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 radical R 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 radicals R 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.

[0093] The activating agent is selected from the group formed by chlorinated and brominated hydrocarbylaluminum compounds corresponding to the formula A1RX2, in which R is a hydrocarbyl radical and X is a halogen selected from chlorine and bromine alone or in mixtures. The hydrocarbylaluminum halides are advantageously selected from dichloroethylaluminum, dichloroisobutylaluminum, and dibromoethylaluminum. These hydrocarbylaluminum dihalides can advantageously be enriched with aluminum trihalides (A1X3) such as aluminum trichloride.

[0094] Brønsted organic acid compounds preferably correspond to the formula HY, where Y is an organic anion, for example carboxylic, sulfonic, or phenolic. These compounds preferably have a pKa at 20°C of no more than 3. and are preferably chosen from the group formed by halocarboxylic acids of formula RCOOH, in which R is a halogenated alkyl radical, and preferably a halogenated alkyl radical containing at least one halogen atom alpha to the -COOH group, with a total of 2 to 10 carbon atoms. Preferably, a haloacetic acid of formula CXpH3-p-COOH is used, in which X is fluorine, chlorine, bromine, or iodine, with p being an integer from 1 to 3. Examples include trifluoroacetic, difluoroacetic, fluoroacetic, trichloroacetic, dichoroacetic, and chloroacetic acids. These examples are not exhaustive, and arylsulfonic, alkylsulfonic, fluoroalkylsulfonic, picric acid, and nitroacetic acid may also be used.

[0095] The catalyst used in the first oligomerization step (c) may also contain at least one carboxylic acid anhydride of formula (RCO)2O, 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.

[0096] Finally, the catalyst used in the first oligomerization step c) may also contain a phosphine ligand of formula PR1R2R3 in which the RI, R2, and R3 groups, identical or different from each other, are bonded or not. The hydrocarbyl groups RI, R2, and R3 of the phosphine ligand PR1R2R3 advantageously comprise 1 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and preferably between 3 and 10 carbon atoms. Preferably, the hydrocarbyl groups RI, R2, and R3 of the phosphine ligand PR1R2R3 are selected from the group formed by the methyl, ethyl, propyl, isopropyl, n-butyl, tert-butyl, cyclopentyl, cyclohexyl, benzyl, and adamantyl groups.

[0097] The catalyst can be preconditioned before contacting it with ethylene. Preconditioning the catalytic composition consists of mixing the three components in a hydrocarbon solvent, for example an alkane or an aromatic hydrocarbon, or a halogenated hydrocarbon, or preferably the olefins produced in the oligomerization reaction, under stirring and in an inert atmosphere, for example nitrogen or argon, at a controlled temperature between 0 and 80 °C, preferably between 10 and 60 °C, for a period 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.

[0098] This preconditioning of the catalyst makes it possible to increase the activity of the catalyst in the oligomerization of ethylene.

[0099] The catalyst present in said unit performing the oligomerization step c) is in liquid form. Depending on the chemical composition of said catalyst, the weight proportions of each of the catalyst components are to be controlled during catalyst synthesis. The molar ratio of the hydrocarbylaluminum halide to the nickel compound, expressed as the Al / Ni ratio, is advantageously from 2:1 to 50:1, and preferably from 2:1 to 20:1.

[0100] The molar ratio of Brønsted acid to nickel compound is advantageously 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 between 0.001:1 and 1:1, most advantageously between 0.01:1 and 0.5:1. If the catalyst comprises a phosphine-type ligand, the molar ratio of the phosphine-type ligand to nickel compound is advantageously between 2 and 25, preferably between 5 and 20, and more preferably between 5 and 15.

[0101] In one embodiment, said homogeneous catalyst is the catalyst described in document WO2017017087.

[0102] The first oligomerization step c) implemented by homogeneous catalysis is advantageously carried out continuously: the catalytic solution is injected into the unit operating the oligomerization step and ethylene is injected therein continuously. The unit operating said ethylene oligomerization step 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.

[0103] The first oligomerization step c) 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.

[0104] The operating conditions in the reactor(s) carrying out step c) of oligomerization by homogeneous catalysis 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 0.5 and 8 MPa.

[0105] At the exit of the first step c) of oligomerization, the homogeneous catalytic system is found mixed with the olefinic effluent produced during step c) and the ethylene which has not reacted.

[0106] Advantageously, said olefinic effluent produced during the first step c) of oligomerization preferably undergoes at least one step c') of treatment / separation of the homogeneous catalytic system of said effluent before being sent to the second step d) of oligomerization.

[0107] The 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 (c). The treatment / separation step (c') of the homogeneous catalytic system may employ various methods suitable for this treatment and known to those skilled in the art. By way of non-limiting example, the following three methods may be cited:

[0108] 1) either by using a capture mass,

[0109] 2) either by treatment with a base and / or an acid, of the olefinic effluent from the first step c) of oligomerization, neutralized or not by a base,

[0110] 3) either by separating said olefinic effluent from the first step c) of oligomerization, neutralized or not by a base, into a first effluent comprising at least part of the C10+ olefinic compounds and also the homogeneous catalytic system and into a second olefinic effluent free of the catalytic system, said separation being followed by the treatment of the effluent comprising at least part of the C10+ compounds and the homogeneous catalytic system by acid and / or basic washing or by the use of capture mass.

[0111] Reference may be made to the description of patent FR2959752 for more details on this treatment / separation step of the homogeneous catalytic system.

[0112] Advantageously, the olefinic effluent, having optionally undergone a treatment / separation step c') of the homogeneous catalytic system, is sent to an optional separation step c”), this step allows the separation of said olefinic effluent from the first oligomerization step c) or from the treatment / separation step c') of the homogeneous catalytic system, into at least one olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 4 (C4+) and into at least one light olefinic effluent C2.

[0113] Said separation step c”) can advantageously be implemented by any method known to the person skilled in the art such as, for example, the combination of one or more high and / or low pressure and high and / or low temperature separating flasks, and / or distillation steps comprising one or more distillation columns.

[0114] Light olefinic effluent C2 is understood to mean an effluent advantageously comprising a content of at least 50% by weight and preferably at least 65% by weight of olefinic compounds having a number of carbon atoms less than 4.

[0115] Advantageously, a part, preferably all of said light olefinic effluent C2 is recycled in the first oligomerization step c).

[0116] An olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 4 (or C4+ olefinic effluent) is defined as an effluent advantageously comprising a content of at least 80% by weight, preferably at least 90% by weight, of olefinic compounds having a number of carbon atoms between 4 and 8 (C4-C8). The C4+ olefinic effluent may also comprise olefinic compounds having a number of carbon atoms greater than or equal to 10 (C10+ compounds).

[0117] According to a first variant, in the case where the olefinic effluent from said step c) or c') undergoes said optional separation step c"), the entire C4+ olefinic effluent from said optional separation step c"), comprising the C4-C8 olefinic compounds and possibly the C10+ olefinic compounds, is advantageously sent to the second oligomerization step d).

[0118] According to a second embodiment, again in the case where the olefinic effluent from step c) or c') undergoes said optional separation step c'), the C4+ olefinic effluent is advantageously separated in a second optional separation step c'' into at least one olefinic effluent comprising compounds having a number of carbon atoms between 4 and 8 (C4-C8) and at least one olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 10 (C10+ compounds). In this case, said C4-C8 olefinic effluent is advantageously sent to the second oligomerization step d) and said C10+ olefinic effluent is advantageously optionally hydrogenated and sent to the fractionation step e).

[0119] Said C4-C8 olefinic effluent is defined as an effluent comprising olefinic compounds distributed according to the following distribution: at least 50% by weight and preferably at least 70% by weight of olefinic 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 olefinic compounds, the weight percentages being expressed in relation to the total mass of olefins present in the C4-C8 olefinic effluent.

[0120] Similarly, said olefinic effluent C10+ is defined as an effluent comprising olefinic compounds distributed according to the following distribution: at least 50% by weight and preferably at least 70% by weight, of olefinic 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 in relation to the total mass of olefins present in the olefinic effluent C10+.

[0121] Thus, the input charge of the second oligomerization step d) advantageously comprises at least in part:

[0122] - the entirety of the olefinic effluent from the first oligomerization step c) in the case where no step c') of homogeneous catalytic system treatment / separation and / or c") of optional separation is implemented between the first and second oligomerization steps, or

[0123] - the entire C4+ olefinic effluent (i.e., a portion of the effluent olefinic from the first oligomerization step c), and separated from the light olefinic effluent (C2-C4), in the case where at least one homogeneous catalytic system treatment / separation step c') and one optional separation step c") are implemented between the first and second oligomerization steps, or

[0124] - the entirety of said C4-C8 olefinic effluent, in the case where at least one step c') of treatment / separation of the homogeneous catalytic system and two successive optional separation steps c”) and c”’) are implemented between the first and second oligomerization steps.

[0125] An example of a first oligomerization step c) is the DimEne-B® process marketed by the company Axens.

[0126] Another example of a first oligomerization step c) is the Dimersol-E® process marketed by Axens.

[0127] Step d) of second oligomerization

[0128] The process according to the invention comprises a second step d) of oligomerization of at least:

[0129] - a portion of the olefinic effluent from step c),

[0130] - a portion of the fraction consisting essentially of compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms from step b).

[0131] The second step d) of oligomerisation allows obtaining an effluent of the middle distillate type.

[0132] Said second oligomerization step is carried out in the presence of a heterogeneous amorphous or zeolitic catalyst.

[0133] According to a preferred embodiment, the catalyst used in the second oligomerization step d) is an amorphous heterogeneous catalyst comprising, and preferably made up of, an amorphous mineral material selected from silica-aluminas and silicified aluminas.

[0134] According to another preferred embodiment of the invention, the second oligomerization step (d) is carried out in the presence of a heterogeneous zeolite catalyst, that is to say, a heterogeneous catalyst comprising at least one zeolite, preferably having at least pore openings containing 10 or 12 oxygen atoms (10MR or 12MR), and advantageously chosen from aluminosilicate type zeolites having an overall Si / Al molar ratio greater than 10.

[0135] In one embodiment, said catalyst used in the second oligomerization step d) comprises at least one zeolite selected from structural type zeolites MFI, MTW, MOR, TON, MEL, MFS, MTT, taken alone or in mixture.

[0136] In one embodiment, said catalyst used in the second oligomerization step d) comprises at least one zeolite selected from the zeolites 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, 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 synthesized in the presence of the triethylenetetramine structuring agent.

[0137] The zeolite used in the catalyst in step d) of the process according to the invention can advantageously undergo several post-treatments known to those skilled in the art, such as, for example, being modified by desalumination or desilication according to any desalumination method, external surface passivation or desilication known to those skilled in the art, in order to improve its activity and / or stability.

[0138] Said catalyst used in step d) of the process according to the invention also advantageously comprises at least one oxide-type matrix, also called a binder. A matrix according to the invention is understood to be an amorphous or poorly crystallized matrix.

[0139] Said matrix is ​​advantageously selected from 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, said matrix is ​​selected from the elements of the group formed by aluminas, clays, and silicas; more preferably, said matrix is ​​selected from aluminas; and even more preferably, said matrix is ​​gamma alumina.

[0140] The catalyst used in step d) of the process according to the invention is advantageously shaped into grains (or particles) 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.

[0141] The second oligomerization step d) is advantageously implemented in the minus one fixed-bed reactor.

[0142] In one embodiment, in the second oligomerization step d), at least a portion of the essence-type cut from the fractionation step e) is also oligomerized.

[0143] The second oligomerization step d) of the process according to the invention advantageously operates at a temperature between 50 and 400°C, preferably between 100 and 350°C and preferably between 100 and 300°C, at an absolute pressure between 2 and 15 MPa, preferably between 2 and 8 MPa and preferably between 3 and 8 MPa and at an hourly weight rate between 0.1 and 10 h-1 and preferably between 0.4 and 5 h-1.

[0144] The hourly weight velocity is defined here as the ratio of the mass flow rate of the "fresh" feed entering at step d) to the mass of catalyst without taking into account any recycles.

[0145] The middle distillate effluent produced by the second oligomerization step d) is an olefinic effluent comprising at least 80% by weight and preferably at least 90% by weight of olefins comprising more than 4 carbon atoms, and less than 20%, preferably less than 10%, of unreacted C4 olefins (C4 meaning comprising 4 carbon atoms), the weight percentages being expressed relative to the total weight of olefins contained in the middle distillate effluent produced.

[0146] The middle distillate effluent advantageously comprises at most 50% by weight and preferably at most 40% by weight of C4-C8 olefinic compounds, and at least 50% by weight and preferably at least 60% by weight of C10+ olefinic compounds (i.e. comprising 10 or more carbon atoms), the weight percentages being expressed in relation to the total mass of olefins present in said effluent.

[0147] The process according to the invention is a flexible process in that the operating conditions and the choice of catalyst in the second step d) 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.

[0148] In the case where the majority production of hydrocarbon base of the diesel type is more particularly sought, the second step d) of oligomerization operates advantageously in the presence of a catalyst comprising at least one zeolite chosen from among the aluminosilicate type zeolites having an overall Si / Al ratio greater than 10 and a pore structure of 10 or 12MR and at a temperature between 200 and 300°C, at a pressure between 3 and 7MPa and at a weight-hourly rate between 0.1 and 5 h1.

[0149] In the case where the majority production of basic hydrocarbon fuel of the kerosene type is The second oligomerization step d) is particularly sought after and operates advantageously in the presence of an amorphous catalyst, preferably comprising and preferably made up of silica alumina at a temperature between 100 and 300°C, at a pressure between 2 and 6 MPa and at a weight-hourly rate between 0.1 and 5 h1.

[0150] An example of a second oligomerization step d) is the Polynaphta® process marketed by the company Axens.

[0151] Step e) of splitting

[0152] The process according to the present invention includes a step e) of fractionating the middle distillate type effluent from step d).

[0153] Step e) 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:

[0154] - A petrol cut,

[0155] - A cut of middle distillates (diesel and / or kerosene).

[0156] A light effluent comprising C2-C4 compounds can also be separated for recovery either pure or in mixture.

[0157] A heavy fraction having an initial boiling point between 350 and 370 °C can also be advantageously separated.

[0158] The term "essence" cut means the cut comprising hydrocarbon compounds whose boiling point is between ambient temperature and 220°C.

[0159] The term "middle distillates" means the cut comprising hydrocarbon compounds with a boiling point between 140 and 360°C.

[0160] At least part of the essence cut from the fractionation step e) can advantageously be recycled in the second oligomerization step d) of the process according to the invention.

[0161] In one embodiment, the unreacted C4 olefins are separated from the effluent from step d) and then recycled into the input of step d) of second oligomerization.

[0162] One of the objectives of the present invention being to maximize the yield in base middle distillates and preferably in base kerosene, said light effluent (comprising C2-C4 compounds) and the gasoline cut (corresponding to C4-C8 compounds), undesired, are advantageously oligomerized again respectively in step c) and in step d) of the process according to the invention, allowing the increase of their molecular weight and thus the increase of their boiling point and their compatibility with the intended use.

[0163] At least a part, preferably all of the middle distillates cut (diesel and / or kerosene) from the fractionation step e) advantageously undergoes a step f) optional hydrogenation of olefins, to make them incorporable into the fuel pool. Preferably, at least part and preferably all of the middle distillate cut (diesel and / or kerosene) from the fractionation step e) is brought into contact with a hydrogen-rich gas in the presence of a catalyst comprising at least one metal from group VIII, advantageously chosen from palladium and nickel alone or in mixture, and a support advantageously chosen from alumina, silica or silica-alumina.

[0164] The catalyst implemented in the optional hydrogenation step f) 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 catalyst.

[0165] The optional hydrogenation step f) advantageously operates at a temperature between 100 and 250°C at the reactor inlet, at a pressure between 2 and 5 MPa and at an hourly weight rate between 0.05 and 8 h-l.

[0166] The performance of the hydrogenation is validated by a measurement of the number of bromine which is advantageously at most 5 g Br / lOOg, in the case where it is desired to saturate all the unsaturated compounds present in the cut to be hydrogenated.

[0167] The effluent from the optional hydrogenation step f) contains mainly valuable hydrocarbons that can be incorporated into the kerosene and / or diesel pool and preferably kerosene.

[0168] An optional final separation step (g) may advantageously be implemented after the optional hydrogenation step (f) to allow the fractionation of the effluent from step (f) into a kerosene cut and / or a diesel cut and / or a cut having a boiling point above 360°C.

[0169] The term "diesel blend" means the blend comprising hydrocarbon compounds with a boiling point between 220 and 360°C.

[0170] The term "kerosene cut" means the cut comprising hydrocarbon compounds whose boiling point is between 140 and 300°C.

[0171] According to one embodiment, at least a portion of said effluent from the optional hydrogenation step f) can advantageously be recycled in the first oligomerization step c) so as to constitute a diluent of the feed of said step c) and thus stabilize the catalyst.

[0172] When the desired fuel is kerosene, the olefin hydrogenation step is essential. EXAMPLES

[0173] Example: Process for producing middle distillates from an ethanol feedstock

[0174] Step a): Dehydration of the load

[0175] The feedstock is a bioethanol feedstock having the following characteristics:

[0176] Sugar cane ethanol, containing 92% by weight of ethanol, 500 ppm by weight of organic impurities (heavy alcohols, methanol, esters, acids), the remainder being water.

[0177] This charge is dehydrated in the presence of a PZSM-5 zeolite catalyst at a temperature of 400°C, at a pressure of 0.6 MPa, and at an hourly weight rate of 7h*.

[0178] The composition of the dewatering effluent is given in the following table:

[0179] [Tables] Mass balance (% by weight) Charge Effluent cases 1 and 2 Ethanol 100 0.3 Ethylene 54.5 C3+ cut 5.5 Oxygenated except ethanol 0.61 Water 39.1

[0180] The composition of the C3+ is 74.3% by weight of olefins (20.1% propylene, 45.4% butene, 8.8% C5-C6 olefins), 19.9% ​​by weight of paraffins (13.5% C3-C4 paraffins, 6.4% C5-C6 paraffins) and 5.9% aromatics.

[0181] Separation step b)

[0182] The effluent is introduced into a cryogenic distillation column after drying, compression, and removal of CO, CO2, and acetaldehyde by collection media and molecular sieves (Cu / ZN deoxo media, 3A and 13X sieves) at 2.28 MPa. This column uses structured packing for a height equivalent to 40 theoretical plates. At the top of the column, at -22°C, an ethylene-rich fraction is produced, containing traces of propylene. The bottom fraction is separated in a second distillation column (20 theoretical plates) at 0.7 MPa and 30°C at the top, producing a C3-C5-rich top fraction (and ethylene-free) and an aromatic-rich bottom fraction. The top fraction from this second column is sent to the oligomerization step d), while the bottom fraction is used as fuel in the process furnaces. The composition of the head cut is:

[0183] [Tables2] Compound(s) Percentage by weight of the compound relative to the total weight of the upper effluent from the second separation column Propylene 21.5 Butene 49.0 C5-C6 Olefins 9.3 Saturates 20.2

[0184] Step c) of first oligomerization

[0185] The ethylene-rich cut from separation step b) is sent to the first oligomerization step c) which operates in the presence of a homogeneous catalyst comprising a divalent nickel compound, with a dichloroethylaluminum co-catalyst (EADC), and at a temperature of 50°C, at a pressure of 1 MPa. The Al / Ni molar ratio is fixed at 15.

[0186] The C4+ compound composition of the olefinic effluent from step c) is given in the following table:

[0187] [Tables3] Material balance (% by weight) Charge Effluent cases 1 and 2 Ethylene 54.5 Fuel gas 0.55 C4 olefins 22.1 C6 olefins 18.9 C8 olefins 7.8 C10+ olefins 5.1

[0188] The selectivities of the different cuts are as follows:

[0189] - 41% by weight as C4 olefins

[0190] - 35% by weight of C6 olefins

[0191] - 14.5% by weight of C8 olefins

[0192] - 9.5% by weight as olefins Cl0+

[0193] The effluent exiting step c) is separated into 2 cuts:

[0194] - A cup containing C4, C6 and C8 olefins sent to step d)

[0195] - A cup containing the C10+ olefins sent to step f)

[0196] Step d) of second oligomerization

[0197] In case 1 (comparative according to the prior art) the cut containing the C4, C6 and C8 olefins from step c) of first oligomerization is sent to step d).

[0198] In case 2 (According to the invention), the cut containing the C4, C6 and C8 olefins from the first oligomerization step c) is sent to step d) together with the C3-C5 rich fraction from the separation step b).

[0199] Step d) of second oligomerization operates in the presence of a heterogeneous aluminosilicate catalyst at a temperature of 110°C, at an absolute pressure of 6.0 MPa and at an hourly volumetric rate of 0.2 h1.

[0200] The effluent from the second oligomerization is separated in a first column into two fractions:

[0201] - A recycled C4 cut at the input of step d) or output of the process in the form of purge

[0202] - A C6+ cut sent to a second column

[0203] The C6+ section from this first column is separated in a second column into two fractions:

[0204] - A C6-C8 cut recycled as input to step d) or output of the process in the form of purge

[0205] - An oligomerate sent to step e)

[0206] The recycling rate of the C6-C8 cut from the fractionation step e) relative to the feed entering step d) is 3.5.

[0207] The recycling rate of C4 not reacted in step d) and separated in step e) with respect to the feed entering in step d) is 1.5.

[0208] The composition of the effluent from the second oligomerization step is described in the following table:

[0209] [Tables4] Mass balance (% by weight) Charge Effluent Case 1 Case 2 Case 1 Case 2 C4 Olefins 22.1 22.1 C6 Olefins 18.9 18.9 C8 Olefins 7.8 7.8 C3-C6 Cut 4.0 C4-C8 Purge 1.0 1.1 Oligomerate 47.9 51.8

[0210] Step e) of hydrogenation and fractionation:

[0211] The oligomerate obtained in step d) is hydrogenated jointly with the fraction containing the C10+ olefins from step c) of first oligomerization after separation. This step is carried out with a Ni catalyst on alumina, at a temperature of 180°C, at a pressure of 1.5 MPa and at a volumetric rate of 0.5 h1.

[0212] The hydrogenated effluent is sent to a fractionation column where a kerosene cut and a diesel cut are recovered.

[0213] The fuel yield of the effluent from the dehydrogenation and fractionation step e) is described in the following table:

[0214] [Tables5] Material balance (% wt) Load Effluent Case 1 Case 2 Case 1 Case 2 Olefins C10+ 5.1 5.1 Oligomerate 47.9 51.8 Kerosene 50.5 54.3 Diesel 2.4 2.6

[0215] The overall yield of the process is described in the following table:

[0216] [Tableauxô] Percentage by weight relative to the total weight of the load entering at step a) Case 1 (comparative) Case 2 (according to the invention) Gasoline 7.6 3.1 Kerosene 50.5 54.3 Diesel 2.4 2.6 Water 39.1 39.1 Ethanol 0.3 0.3

[0217] It is therefore observed that the process according to the invention comprising sending the C3+ compounds from the dehydration step a) to the second oligomerization step d) allows obtaining a better yield of Kerosene (+3.8% = 54.3% - 50.5%, compared to the weight of the incoming feed of the process) and to a lesser extent a better yield of Diesel (+0.2% = 2.6% - 2.4%) compared to the weight of the incoming feed of the process).

Claims

1. Claims Process for the production of hydrocarbon bases of the middle distillate type and preferably kerosene hydrocarbon base from an alcoholic feedstock, comprising at least one mono-alcohol, preferably comprising ethanol, said process comprising: a) a step of dehydration of the alcoholic feedstock comprising at least one mono-alcohol, preferably comprising ethanol, and obtaining at least one dehydration effluent comprising: - at least 80% by weight, preferably at least 85% by weight, preferably at least 90% by weight of ethylene, relative to the total weight of the effluent considered dry, - compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably having between 3 and 6 carbon atoms, said dehydration step being carried out in the presence of an amorphous acid catalyst or a zeolitic acid catalyst; b) a step of separating the dehydration effluent obtained in step a) and obtaining at least: - a fraction comprising essentially ethylene, - a fraction essentially comprising compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably between 3 and 6 carbon atoms; c) a first step of oligomerization of at least part of the fraction essentially comprising ethylene from step b) and obtaining at least one olefinic effluent comprising at least 80% by weight of olefins having a number of carbon atoms greater than or equal to 4, relative to the total mass of olefins contained in said olefinic effluent, said first oligomerization step being carried out in the presence of a homogeneous catalyst; d) a second oligomerization step of at least: - part of the effluent from step c), - a part of the fraction essentially comprising compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, preferably between 3 and 6 carbon atoms, resulting from step b), and obtaining an effluent of the middle distillate type, said second oligomerization step being carried out in the presence of an amorphous or zeolitic heterogeneous catalyst; e) a stage of fractionation of the middle distillate type effluent from stage d).

2. Process according to claim 1 in which the dehydration effluent comprises at least 1% by weight, preferably at least 5% by weight, more preferably at least 8% by weight of compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, more preferably having between 3 and 6 carbon atoms, relative to the total weight of the effluent considered dry.

3. Process according to any one of the preceding claims wherein the compounds having at least 3 carbon atoms, preferably having between 3 and 9 carbon atoms, more preferably having between 3 and 6 carbon atoms comprise olefins, preferably at least 50% by weight, more preferably at least 60%, more preferably at least 70% by weight of olefins relative to the total weight of the compounds having at least 3 carbon atoms.

4. Process according to any one of the preceding claims, in which the fraction essentially comprising compounds having at least 3 carbon atoms from step b) undergoes an additional separation step to obtain at least: - an olefinic fraction essentially comprising olefins having between 3 and 6 carbon atoms, - a heavy fraction comprising aromatics, preferably having between 6 and 9 carbon atoms.

5. Process according to claim 4 in which the heavy fraction advantageously undergoes a step of selective hydrogenation of the unsaturated olefinic or diolefinic compounds contained therein and then the effluent obtained is sent to the fractionation step e).

6. Process according to any one of the preceding claims, in which the olefinic effluent from the first oligomerization step c) comprises less than 20% by weight, preferably less than 10% by weight of ethylene which has not reacted during the first oligomerization step c), the percentages being expressed as percentages by weight relative to the total mass of olefins contained in said olefinic effluent produced.

7. Process according to any one of the preceding claims, in which the homogeneous catalyst used in step c) of oligomerization comprises: - at least one nickel precursor of oxidation degree (+11), - and at least one activating agent chosen from the group formed by chlorinated and brominated hydrocarbylaluminium compounds, taken alone or as a mixture.

8. Process according to any one of the preceding claims, in which the olefinic effluent from step c) is sent to a separation step c”), this step allowing the separation of said olefinic effluent from the first oligomerization step c), into at least one olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 4 and into at least one light olefinic effluent C2.

9. Process according to claim 8 in which a part, preferably all of the light olefinic effluent C2 is recycled in the first oligomerization step c).

10. Process according to claim 8 or 9 in which the olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 4 is separated in a second separation step c”), into at least one olefinic effluent comprising compounds having a number of carbon atoms between 4 and 8 and at least one olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 10.

11. Process according to claim 10 in which the olefinic effluent comprising compounds having a number of carbon atoms greater than or equal to 10 is hydrogenated and sent to the fractionation step e).

12. Process according to any one of the preceding claims, in which the middle distillate effluent produced by the second oligomerization step d) is an olefinic effluent comprising at least 80% by weight and preferably at least 90% by weight of olefins comprising a number of carbon atoms greater than 4, and less than 20%, preferably less than 10% of unreacted C4 olefins, the weight percentages being expressed relative to the total weight of the olefins contained in the middle distillate effluent produced.

13. Process according to any one of the preceding claims, in which the fractionation step e) is carried out in at least one distillation column so as to separate the middle distillate type effluent from step d) into at least two cuts: - A gasoline cut, - A middle distillate cut.

14. Process according to claim 13 in which at least a portion, preferably all of the middle distillate cut from fractionation step e) undergoes a step f) of hydrogenation of the olefins.

15. Process according to any one of the preceding claims, in which the unreacted C4 olefins are separated from the effluent from step d) and then recycled to the inlet of step d) of the second oligomerization.