Improved method for producing kerosene from synthetic hydrocarbons in series with recycle gas management

Abstract

The present invention aims to provide a method for producing kerosene from a paraffinic feedstock produced by Fischer-Tropsch synthesis, the method comprising at least one hydrocracking step and at least one hydroisomerization step arranged in series, the operating conditions and the catalysts used in the steps being specifically selected to selectively produce a kerosene fraction while minimizing the production of light fractions such as C1-C4 light gases and naphtha, by virtue of specific management of the recycle gases, and also making it possible to carry out hydroisomerization step e) and / or hydrocracking step c) at a pressure lower than hydrotreating step a).

Description

[0001] Description

[0002] Title of the invention: Improved process for producing kerosene from synthetic hydrocarbons in series with recycle gas management

[0003] Scope of the invention

[0004] The Fischer-Tropsch process makes it possible to produce synthetic hydrocarbons from a gaseous feedstock composed mainly of hydrogen and carbon monoxide, also called synthesis gas (CO+H2).

[0005] In particular, in the low-temperature Fischer-Tropsch process, synthesis gas is catalytically converted into water, oxygenated products, olefins, and predominantly linear paraffins, also known as n-paraffins, in gaseous, liquid, or solid form under standard conditions. After water separation, the resulting synthetic hydrocarbons are mainly composed of predominantly linear paraffins but also contain olefins and oxygenated products.

[0006] The effluent from the Fischer-Tropsch process, at the outlet of the Fischer-Tropsch synthesis unit, can be divided into two fractions, a light fraction, called cold condensate, and a heavy fraction, called waxes.

[0007] These synthetic hydrocarbons produced cannot be directly incorporated into conventional fuel pools or used as lubricants. For example, the melting point of a normal 14-carbon paraffin with a boiling point of 254°C is approximately 6°C, making its direct incorporation into the kerosene fraction impossible given the required specification of -40°C for the disappearance point of crystals for kerosene prepared from paraffins produced by Fischer-Tropsch synthesis according to ASTM D7566. A hydroisomerization step is necessary to lower the pour points of the various hydrocarbon compounds. Furthermore, processing steps are required to remove olefmic and oxygenated compounds, increase the yield of middle distillates, and improve the properties of the produced fractions to meet their specifications.To perform the hydroconversion of Fischer-Tropsch synthesis products, so-called bifunctional catalysts are generally used. These are characterized by the combination of an acidic and a hydrogenating functional group. For the heavy fraction, that is, the fraction with an initial boiling point exceeding the maximum temperature specified for kerosene use, the cracking activity of the aforementioned catalysts is sought in order to convert the molecules into shorter-chain molecules, and therefore molecules with lower boiling points, until the products formed fall within the desired distillation range. For the light fraction, that is, covering a distillation range suitable for the target product, only the isomerizing activity of the aforementioned catalysts is used.To do this, one can then choose to play on the formulation of bifunctional catalysts in order to make them more or less selective towards cracking or towards isomerization, but this may prove insufficient with a propensity of so-called isomerizing catalysts to overcrack the products to the point of forming compounds that are too light (gas or gasoline) which are then no longer usable according to the objective sought, i.e. kerosene.

[0008] To illustrate the problem, we will cite below some results from prior art which allow us to evaluate it.

[0009] First, patent application FR3084082 describes a process for producing middle distillates, i.e., diesel and kerosene, from a paraffinic feedstock produced by Fischer-Tropsch synthesis. This process involves treating two fractions: a light fraction, called cold condensate, and a heavy fraction, called waxes. In this process, fractionation of the heavy waxes fraction yields two other cuts of varying weights. The lighter of the two is then mixed with the cold condensate cut before this mixture is hydrotreated and isomerized. Simultaneously, the heavy waxes fraction is hydrocracking to form an effluent, which is then fractionated with the effluent from the hydroisomerized fraction to obtain at least one gasoline fraction and at least one middle distillate fraction.Although the scheme implements a specific hydroisomerizing catalyst based on at least one IZM-2 zeolite, it appears that approximately 22% by weight of the Fischer-Tropsch synthesis effluent is in the form of naphtha, and it can also be assumed that by specifically seeking to produce kerosene without diesel, the quantity of naphtha would be even higher, which does not allow the problem of maximizing kerosene yield to the desired specifications to be met.

[0010] Patent application WO15063213 discloses a process for converting a paraffinic feed, which may be a feed from the Fischer-Tropsch synthesis, in which the feed is transformed in a step a) to obtain a feed at least partially isomerized on a chain of two catalysts in series, a first catalyst 1 and a second catalyst 2 in which catalyst 2 is more isomerizing and less cracking than catalyst 1, then a step of separating the isomerized effluent into one or more middle distillate fractions and a residual fraction.

[0011] The description specifies that the feed transformation step can be carried out in one or more reactors. The description then describes a fractionation step that can yield a diesel fraction, a kerosene fraction, and a residual fraction boiling above the middle distillates. Catalysts 1 and 2 are preferably composed of an amorphous acid support, preferably of the platinum / silica-alumina type, for the first, and a molecular sieve, preferably of the platinum / zeolite ZSM-12 type with a silicic binder, for the second.

[0012] An optional vacuum distillation step of the residual fraction can be implemented to obtain a base oil distillate fraction and a second residual fraction boiling between 450 and 550°C. Part of this second residual fraction can be recycled to the hydrocracking and hydroisomerization reaction step. The base oil distillate fraction can be sent to a catalytic dewaxing step. Note that if step a) is implemented in two reactors in series, the entire feed from the first reactor is sent to the second reactor. The use of silica binder for the preparation of the more isomerizing catalyst 2 is presented as essential for achieving selectivity for diesel and / or kerosene.However, the examples show that despite the partial conversion (approximately 20% by weight of base oil is not recycled), 10% by weight of gas is formed, and only 67 to 71% of average distillates are produced, with no distinction made between diesel and kerosene. It therefore appears to us that the proposed solution does not address the problem of maximizing kerosene yield to the required specifications.

[0013] Patent application W005001006 also describes a process for treating a hydrocarbon wax, which can be derived from Fischer-Tropsch synthesis, in which this feedstock is successively subjected to hydrocracking and then hydroisomerization before fractionation, allowing the separation of the middle distillate from the heavy fraction. The latter is also separated into a base oil with a high viscosity index. The examples described, based on a preferred catalytic system using a first nickel-tungsten sulfide catalyst supported on silica-alumina, followed by a platinum noble metal catalyst supported on SAPO-11, reveal rather low yields of middle distillates, with the objective of maximizing base oil production. Here again, the implementation does not address the problem of maximizing kerosene yield to the required specifications.

[0014] Patent application WO14001546 again covers a process for producing diesel fuel, heavy distillate, and residual base oil from a feed derived from the Fischer-Tropsch synthesis. This process includes a hydroconversion / hydroisomerization step to obtain a feed that is at least partially isomerized, followed by a step to separate the isomerized feed into diesel fuel, heavy distillate, and a residual fraction with a T10 temperature between 200 and 540°C. In the disclosed process, part of the residual fraction is recycled back into the hydroconversion / hydroisomerization step, while the remainder undergoes a dewaxing step to obtain base oil. The examples show that with such a process, distillate production, in this case diesel fuel, remains low, as a significant proportion of the feed, nearly 50% by weight, is not converted into a lighter cut and is reserved for base oil production.

[0015] This is also the case with patent application W005003067, which describes a process for producing base oil from a feedstock produced by Fischer-Tropsch synthesis. This process first involves separating the feedstock into a boiling cut in the middle distillate range and below, a heavy cut, and an intermediate cut. Subsequently, the intermediate fraction is treated in a hydroisomerization step to produce base oils, preferably over a catalyst that may be based on ZSM-12. In parallel, the heavy fraction is sent to a hydroconversion step to produce lighter compounds, while the fraction not converted in this step is treated in a hydroisomerization step to produce base oils.Here again, the examples highlight the significant proportion of heavy fraction, base oil, produced by the process, approximately 20% by weight, but also the light part, naphtha or gas, also approximately 20% by weight, which does not allow us to meet the problem posed of maximizing the yield of kerosene to the desired specifications.

[0016] Patent application WO14001552 also describes a process for transforming the effluents from a Fischer-Tropsch synthesis to yield three fractions: the first two are middle distillates, and the third is a base oil. To achieve this, the aforementioned synthesis effluent is separated into a light fraction and a heavy fraction. The heavy fraction is then hydrocracking to form a distillate, a heavy distillate, and a heavy residual fraction. Subsequently, the distillate and heavy distillate fractions undergo dewaxing, but the heavy residual fraction also undergoes dewaxing, as it forms a base oil. This process does not address the stated problem of maximizing kerosene yield to the required specifications.

[0017] Finally, application W009041478 discloses a process for producing diesel fuel comprising, firstly, a fractionation step of the effluent from the Fischer-Tropsch synthesis into two fractions: an intermediate fraction and a heavier wax fraction. This is followed by a hydroisomerization step of the intermediate fraction and a hydrocracking step of the wax fraction. The described process further includes another fractionation step applied to the mixture of the hydroisomerized intermediate fraction and the hydrocracking heavy wax fraction into two fractions, each containing a kerosene fraction and a diesel fuel fraction. These fractions are then combined in proportions adjusted to obtain target properties. This process ensures the achievement of precise specifications, but it does not maximize yield, as a fraction of kerosene or diesel fuel must necessarily be discarded.

[0018] The research work carried out by the applicant led him to discover that in order to selectively produce a kerosene cut with properties conforming to the specifications in force, in particular for the cut points and cold properties such as the disappearance point of the crystals, it is necessary to judiciously combine at least two hydrocracking and hydroisomerization steps arranged in series while ensuring that operating conditions are maintained such that in these two steps the hydrocracking and hydroisomerization are carried out with minimal selectivity towards the gas and naphtha cuts.

[0019] An objective of the present invention is therefore to provide a process for the production of kerosene from a paraffinic feedstock produced by Fischer-Tropsch synthesis comprising at least one hydrocracking step and at least one hydroisomerization step arranged in series, the operating conditions and the catalysts used in said steps being chosen in a very specific way, to selectively produce a kerosene cut, while minimizing the production of light cuts such as light C1-C4 gases, naphtha and also allowing the hydroisomerization step e) and / or the hydrocracking step c) to be carried out at a pressure level lower than the hydrotreating step a).

[0020] This lower-pressure operation in the aforementioned hydroisomerization step e) improves the selectivity of the hydroisomerizing activity against unwanted overcracking, thus increasing kerosene yield and kerosene / naphtha selectivity. This is achieved without requiring a dedicated compressor for step e), nor a pressure-reducing valve at the inlet of the gas from compression step i) to step e).

[0021] Furthermore, the impact of the process according to this invention is negligible in terms of cost, power consumed and the footprint of the recycle compressor.

[0022] Object of the invention

[0023] The present invention relates to a process for producing kerosene from a paraffinic feedstock produced by Fischer-Tropsch synthesis, comprising at least the following steps and preferably consisting of:

[0024] Step a): Hydrotreating at least part, and preferably all, of the paraffinic feed produced by Fischer-Tropsch synthesis in the presence of a hydrotreating catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2.5 and 15 MPa, with a hydrogen flow rate adjusted to obtain a ratio between 100 and 3000 normal liters of hydrogen per liter of feed, and at a volumetric rate per hour between 0.1 and 40 h 1 , Step b'): the separation of the effluent from step a) into at least an aqueous fraction consisting of at least part of the water formed during said step a) and preferably all of the water formed, a hydrotreated hydrocarbon liquid fraction and a gaseous fraction,

[0025] Step b): the fractionation in one or more steps of the hydrotreated hydrocarbon liquid fraction from step b') into at least a gaseous fraction, a naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 100 and 160°C, at least a kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a heavy fraction having an initial boiling point above 250°C,

[0026] Step c): Hydrocracking of all of said heavy fraction having an initial boiling point above 250°C from step b) to produce a hydrocraced effluent, in the presence of a hydrocracking catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2 and 15 MPa, at a space velocity between 0.1 and 10 h 1and at a hydrogen flow rate adjusted to obtain a ratio of between 100 and 2000 normal liters of hydrogen per liter of feed, said hydrocracking catalyst comprising at least one noble metal of Group VIII of the periodic table and a support comprising at least one acidic solid, said operating conditions of said step c) being adjusted so that the conversion by passing into products having boiling points greater than or equal to a temperature Tx into products having boiling points below that same temperature Tx is less than 0.5, preferably less than 0.4 and preferably less than 0.3 and preferably less than 0.2, Tx being between 250 and 350°C, preferably between 270 and 340°C and most preferably between 280 and 330°C,

[0027] Step d'): the separation of the effluent from step c) into at least one hydrocracked hydrocarbon liquid fraction and one gaseous fraction, said steps b') and d') of separation advantageously being carried out in the same separation unit or in separate separation units,

[0028] Step d): the fractionation in one or more steps of at least all or part of the hydrocracked hydrocarbon liquid fraction from step d'), into at least a gaseous fraction, a naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 100 and 160°C, at least a kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a residual heavy fraction having an initial boiling point above 250°C, said fractionation steps b) and d) advantageously being carried out in the same fractionation unit or in separate fractionation units,

[0029] Step e): the hydroisomerization of at least a portion of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C from fractionation step b) and of all or part of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C from fractionation step d) in the case where said fractionation steps b) and d) are separate, in the presence of a hydroisomerization catalyst operating at a temperature between 200 and 450°C, a total pressure between 1 and 15 MPa and a total pressure at least 0.3 MPa lower than the total pressure used in hydrotreating step a) or step c) hydrocracking, a spatial velocity between 0.1 and 10 h 1, a hydrogen flow rate adjusted to obtain a ratio between 100 and 2000 normal liters of hydrogen per liter of feed, to produce a hydroisomerized effluent,

[0030] Step f): Recycling of all or part of the residual heavy fraction having an initial boiling point above 250°C in step c) of hydrocracking,

[0031] Step g): possibly purging part of the hydrocracked effluent from step c) of hydrocracking,

[0032] Step h'): the separation of the effluent from step e) into at least a hydroisomerized hydrocarbon liquid fraction and a gaseous fraction,

[0033] Step h): the fractionation of all or part of the hydroisomerized hydrocarbon liquid fraction from step h'), into at least one gaseous fraction, one naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 120 and 160°C, and at least one kerosene fraction having an initial boiling point between 120 and 160°C, Step i): the compression in a single compression section of the gaseous fraction from step h'),the gaseous effluent from step i) being recycled to step a) and / or c) and / or e) and at least part and preferably all of the gaseous fraction from step b') being sent to step c) hydrocracking and / or step e) hydroisomerization without passing through said step i) compression and / or at least part and preferably all of the gaseous fraction from d') being sent to step e) hydroisomerization without passing through said step i) compression.

[0034] The process according to the invention also applies to a situation in which the Fischer-Tropsch synthesis effluent has previously been divided into two fractions, a light fraction, called cold condensate, and a heavy fraction, called waxes, and where these two fractions should be combined beforehand prior to their simultaneous hydrotreatment.

[0035] In general, the said process applies to all or part of the effluent from the Fischer Tropsch synthesis.

[0036] An advantage of the present invention is therefore to provide a process for the production of kerosene from a paraffinic effluent produced by the Fischer-Tropsch synthesis which allows both the maximization of kerosene production and the limitation of the production of light cracked products which cannot be incorporated into a kerosene pool while reducing investments and allowing the obtaining of improved activity, in particular of the catalyst used in the hydroisomerization step compared to the processes known to Man of the prior art.

[0037] In the embodiment where the separation steps b') and d') and the fractionation steps b) and d) are carried out in separate separation and fractionation units, an advantage of the present invention is to allow operation in the hydrotreating step a) at a higher total pressure than in the hydrocracking step c), itself higher than in the hydroisomerization step e), which makes it possible to ensure good performance of the catalyst in the hydrotreating unit of oxygenated products and olefmes while avoiding penalizing the performance of the catalyst in the hydroisomerization unit whose activity is favored at low pressure.

[0038] In the following text, and unless otherwise specified, the term "heavy fraction" refers to a hydrocarbon effluent obtained at the end of the hydrotreatment and fractionation step(s) after said hydrotreatment step, said hydrocarbon effluent having an initial boiling point above 250°C, advantageously between 250 and 320°C, preferably between 270 and 310°C and preferably between 280 and 300°C. In the following text, and unless otherwise specified, the term "residual heavy fraction" corresponds to a hydrocarbon effluent obtained at the end of the hydrocracking and fractionation step(s) after said hydrocracking step, said hydrocarbon effluent having an initial boiling temperature above 250°C, advantageously between 250 and 320°C, preferably between 270 and 310°C and preferably between 280 and 300°C.

[0039] Recycling at least part of the residual heavy fraction to the hydrocracking stage allows for the cracking of all or part of said residual heavy fraction and its recovery, notably into a kerosene fraction with an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C. Thus, the non-recycled residual heavy fraction is reduced to the bare minimum, preferably to zero, and failing that, it represents a purge.

[0040] In the following text, the groups of chemical elements are given according to the CAS classification (CRC Handbook of Chemistry and Physics, publisher CRC press, editor-in-chief DR Lide, 81 ème edition, 2000-2001). For example, group VIII according to the CAS classification corresponds to the metals of columns 8, 9 and 10 according to the new IUPAC classification, and group VIB to the metals of column 6.

[0041] In the following text, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included within the described range of values. If this were not the case and the limit values ​​were not included within the described range, this clarification will be provided by the present invention.

[0042] In this description, the expression "greater than..." is understood as strictly greater, and symbolized by the sign ">", and the expression "less than" as strictly less, and symbolized by the sign "<".

[0043] detailed description of the invention

[0044] According to the invention, the present invention relates to a process for producing kerosene from a paraffin feedstock produced by Fischer-Tropsch synthesis.

[0045] The Fischer-Tropsch process, well known to those skilled in the art, allows the production of synthetic hydrocarbons from a gaseous feedstock composed mainly of hydrogen and carbon monoxide, also called synthesis gas (CO+H2).

[0046] The synthesis gas used to feed the Fischer-Tropsch process can advantageously be produced from natural gas, coal, biomass, any source of hydrocarbon compounds, or a mixture of these sources. It can also be produced from any existing process that provides CO2, such as carbon capture processes applied to industrial flue gases or biogenic CO2 combined with a CO2 conversion step. Furthermore, hydrogen can also be produced from any existing process known to those skilled in the art. Examples include reforming and water electrolysis processes. Hydrogen can also be produced by other methods such as steam reforming of light hydrocarbons or by the partial oxidation of various hydrocarbons, such as heavy residues.Other hydrogen sources can also be used, such as hydrogen from catalytic cracking gases, which contains significant amounts of CO and CO2. The hydrogen used can also come from the outlet gas of a hydrotreating unit; in this case, the hydrogen may undergo more or less extensive purification steps to remove impurities such as ammonia (NH3) or hydrogen sulfide (H2S).

[0047] In particular, in the low-temperature Fischer-Tropsch process, synthesis gas is catalytically converted into water, oxygenated products, olefins, and essentially linear paraffins, also known as n-paraffins, in gaseous, liquid, or solid form under standard conditions. After water separation, the resulting synthetic hydrocarbons consist mainly of paraffins but also contain olefins and oxygenated products. Preferably, after water separation, the paraffinic effluent from the Fischer-Tropsch process comprises an n-paraffin content exceeding 70% by weight, and even more preferably exceeding 80% by weight, relative to the total mass of said effluent.

[0048] Preferably, the paraffinic effluent from the Fischer-Tropsch process is free from heteroatomic impurities other than oxygen, such as, for example, sulfur, nitrogen or metals.

[0049] Generally, the paraffinic effluent from the Fischer-Tropsch process is, upon exiting the Fischer-Tropsch synthesis unit, divided into two fractions: a light fraction, called cold condensate, and a heavy fraction, called waxes. However, in the case of the present invention, this separation is not mandatory. The process can therefore be applied either to a single effluent containing both the cold condensate and the waxes, or to a portion of each of these effluents, or to a reconstituted fraction of both.

[0050] The light fraction called cold condensate corresponds to hydrocarbons in the gaseous state under the conditions of the Fischer-Tropsch reaction and the heavy fraction called waxes corresponds to hydrocarbons in the liquid state under the conditions of the Fischer-Tropsch reaction.

[0051] The light fraction of cold condensates has an initial boiling point T1 between 15 and 40°C and preferably between 20 and 35°C and a final boiling point T2 between 350 and 400°C and preferably between 360 and 380°C and preferably less than 370°C.

[0052] The heavy wax fraction advantageously has an initial boiling point T3 between 100 and 300°C, and preferably between 125 and 200°C. Preferably, said heavy fraction contains paraffins with a carbon atom count greater than 8.

[0053] This heavy fraction has the particularity, due to its composition, namely essentially n-paraffins with a high number of carbon atoms, which can go up to more than 150, of being solid at room temperature.

[0054] In the light fraction, the paraffin content is greater than 70% by weight, the olefin content is less than 20% by weight, and the oxygenated compound content is less than 10% by weight, these contents being expressed as a percentage by weight relative to the total mass of said light fraction. In the heavy fraction, the paraffin content is greater than 80% by weight, the olefin content is less than 15% by weight, and the oxygenated compound content is less than 5% by weight, these contents being expressed as a percentage by weight relative to the total mass of said heavy fraction.

[0055] According to the invention, the process comprises a) a hydrotreating step of at least a portion and preferably all of the effluent from the Fischer-Tropsch synthesis in the presence of a hydrotreating catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2.5 and 15 MPa, a hydrogen flow rate adjusted to obtain a ratio between 100 and 3000 normal liters of hydrogen per liter of feed, and at an hourly volumetric rate between 0.1 and 40 h -1 .

[0056] Preferably, said hydrotreating step a) operates at a temperature between 280 and 420°C and preferably between 330 and 390°C, at a total pressure between 2.5 and 10 MPa, a hydrogen flow rate adjusted to obtain a ratio between 250 and 2000 normal liters of hydrogen per liter of feed and preferably between 500 and 1500 normal liters of hydrogen per liter of feed, and at an hourly volumetric velocity between 0.25 and 20 rpm 1 and preferably between 0.5 and 10 a.m. 1 . This hydrotreatment step reduces the content of olefmic and unsaturated compounds and decomposes oxygenated compounds present in the effluent from the Fischer-Tropsch synthesis.

[0057] The hydrotreating catalyst used in step a) is a conventional hydrotreating catalyst. This catalyst comprises at least one metal from Group VIII and / or Group VI of the periodic table of elements. Preferably, the catalyst comprises at least one metal from the group of metals formed by nickel, molybdenum, tungsten, cobalt, ruthenium, indium, palladium, and platinum, alone or in mixtures, and comprises at least one support selected from aluminas, boron oxides, magnesia, zirconia, titanium oxides, and clays, or a combination thereof; preferably, this support is alumina. These catalysts may advantageously be prepared by any method known to those skilled in the art or may be acquired from companies specializing in the manufacture and sale of catalysts.The shape of the supports and catalysts involved in step a) can be spherical, or extruded in the form of cylinders, trilobed or even quadrilobed.

[0058] When using non-noble metals from Group VIII, a combination of at least one metal from Group VI, preferably molybdenum or tungsten, and at least one metal from Group VIII, preferably cobalt or nickel, is advantageously employed. The concentration of the non-noble Group VIII metal, when used, is advantageously 0.01% to 15% by weight of oxide equivalent relative to the finished catalyst, and that of the Group VI metal is advantageously 5% to 40% by weight of oxide equivalent relative to the finished catalyst. When a combination of Group VI and Group VIII metals is used, the catalyst is then preferably used in a reduced or sulfide form.

[0059] Under these conditions, the content of unsaturated and oxygenated molecules in the effluent from said step a) is reduced to less than 0.5% by weight and to approximately less than 0.1% by weight in general. The hydrotreatment step is carried out under conditions such that the conversion of products having boiling points above or equal to 300°C to products having boiling points below 300°C is limited to 20% by weight, preferably less than 10% by weight, and even more preferably less than 5% by weight.

[0060] The effluent from step a) can advantageously be sent to a stage for the removal of at least some of the water formed during said step a) and preferably all of the water formed before being sent to step b) of fractionation according to the invention.

[0061] This step of removing at least some of the water can advantageously be carried out by any methods and techniques known to those skilled in the art, for example by drying, passing through a desiccant, flash drying or decantation. Step b')

[0062] The process according to the invention includes a step of separating the effluent from step a) into at least an aqueous fraction consisting of at least a part of the water formed during said step a) and preferably of all the water formed, a hydrotreated hydrocarbon liquid fraction and a gaseous fraction.

[0063] Said separation step b'), can advantageously be carried out according to all methods and techniques known to those skilled in the art. Preferably, said separation step b') is carried out in one or more separating vessels advantageously operating at a pressure as close as possible to the outlet pressure of hydrotreating step a), and at a temperature advantageously between the outlet temperature of the hydrotreating catalyst of step a) and 30°C.

[0064] Preferably, said gaseous fraction separated in said step b') advantageously comprises light C1-C4 gases, as well as hydrogen.

[0065] The process according to the invention comprises a step b) of fractionating in one or more steps the hydrotreated hydrocarbon liquid fraction from step b') into at least one gaseous fraction advantageously comprising the light gases C1-C47, a naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 100 and 160°C, at least one kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a heavy fraction having an initial boiling point greater than 250°C.

[0066] This fractionation step can advantageously be carried out by atmospheric distillation and in some cases by combining atmospheric distillation and vacuum distillation.

[0067] Another way of carrying out this fractionation step is to strip the effluent from step b') prior to atmospheric fractionation in order to purge the gaseous fractions at the inlet of said atmospheric fractionation column.

[0068] According to the invention, the process comprises a step c) of hydrocracking at least a part and preferably all of the heavy fraction from step b) of fractionation to produce a hydrocraced effluent, in the presence of a hydrocracking catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2 and 15 MPa, at a spatial velocity between 0.1 and 10 h 1and with a hydrogen flow rate adjusted to obtain a ratio of between 100 and 2000 normal liters of hydrogen per liter of feed, said hydrocracking catalyst comprising at least one noble metal of group VIII and a support comprising an acidic solid, said operating conditions of said step c) being adjusted so that the conversion by passing into products having boiling points greater than or equal to a temperature Tx into products having boiling points less than that same temperature Tx is less than 0.5, preferably less than 0.4, preferably less than or equal to 0.3 and preferably less than 0.2, Tx being between 250 and 350°C, preferably between 270 and 340°C and most preferably between 280 and 330°C.

[0069] Preferably, step c) operates at a temperature between 280 and 450°C, and even more preferably between 320 and 420°C, at a total pressure between 2.5 and 10 MPa, more preferably between 1 and 9 MPa, at a space velocity between 0.2 and 7 h 1 , and preferably between 0.5 and 5 hours 1 , and with a hydrogen flow rate adjusted to achieve a ratio between 150 and 1500 normal liters of hydrogen per liter of charge and more preferably between 300 and 1500 normal liters of hydrogen per liter of charge.

[0070] Preferably, step c) operates at a total pressure 0.2 to 0.5 MPa lower than that of step a). The charge in step c) advantageously has an initial boiling point above 250°C, preferably between 250 and 350°C, preferably between 270 and 340°C, and most preferably between 280 and 330°C.

[0071] According to the invention, the hydrocracking catalyst implemented in step c) comprises at least one noble hydro-dehydrogenating metal from group VIII of the periodic table and a support comprising at least one acid solid and preferably a Brønsted acid solid, and optionally a binder.

[0072] Preferably, said hydrocracking catalyst comprises at least one noble metal from group VIII selected from platinum and palladium, taken alone or in mixture, preferably active in their reduced form.

[0073] The noble metal content of said catalyst is advantageously between 0.01 and 5% by weight relative to the finished catalyst, preferably between 0.02 and 4% by weight, most preferably between 0.03 and 3% by weight, even more preferably between 0.05 and 2% by weight and most preferably between 0.05 and 1% by weight.

[0074] The metallic function is advantageously introduced into the catalyst by any method known to those skilled in the art, such as co-mixing, dry impregnation or exchange impregnation.

[0075] Advantageously, the Brønsted acid solid comprises and preferably consists of silica alumina and / or zeolite.

[0076] In the case where the Brønsted acid solid comprises a zeolite, the zeolite is preferably a zeolite of structural type FAU, *BEA, ISV, IWR, IWW, MEI, or UWY, taken alone or in mixtures, and preferably selected from zeolites of structural type FAU and *BEA, taken alone or in mixtures. In a preferred embodiment, the zeolite is selected from zeolite Y and beta zeolite taken alone or in mixtures, and preferably the zeolite is zeolite Y, and most preferably dealuminated zeolite USY.

[0077] Preferably, the Brønsted acid solid comprises and is preferably made of silica-alumina.

[0078] Optionally, the hydrocracking catalyst support may also include a binder. Preferably, the support includes a binder when it comprises a zeolite. The binder is advantageously selected from silica (SiO2), alumina (Al2O3), clays, titanium dioxide (TiO2), boron dioxide (B2O3), and zirconia (ZrCh), either alone or in mixtures. Preferably, the binder is selected from silica and alumina, and even more preferably, the binder is alumina in all its forms known to those skilled in the art, such as gamma alumina.

[0079] A preferred hydrocracking catalyst according to the invention advantageously comprises at least one noble metal, said noble metal being platinum, and a silica-alumina as a Brønsted acid solid, without any other binder.

[0080] The silica content of the silica-alumina, expressed as a percentage by weight, is advantageously between 1% and 95%, advantageously between 5% and 95%, preferably between 10% and 80%, highly preferred between 20% and 70%, and even more preferably between 22% and 45%. This silica content is accurately measured using X-ray fluorescence.

[0081] A preferred hydrocracking catalyst used in the process according to the invention comprises a particular silica-alumina. Preferably, said catalyst comprises 0.05% to 10% by weight, preferably between 0.1% and 5% by weight, of at least one noble metal from Group VIII, preferably selected from platinum and palladium (preferably platinum), deposited on a silica-alumina support, without any other binder, containing an amount of silica (SiO2) of between 1% and 95%, expressed as a percentage by weight, preferably between 5% and 95%, preferably between 10% and 80%, and most preferably between 20% and 70%, and even more preferably between 22% and 45%, said catalyst having:

[0082] - a specific BET surface area of ​​100 to 500 m² 2 / g, preferably between 200 and 450 m 2 / g and preferably between 200 and 300 m 2 / g,

[0083] - an average mesopore diameter measured by mercury porosimetry between 4 and 12 nm, preferably between 4 and 11 nm and most preferably between 5 and 11 nm,

[0084] - a total pore volume measured by mercury porosimetry of between 0.2 and 1.2 ml / g, preferably between 0.3 and 1.0 ml / g and most preferably between 0.3 and 0.9 ml / g,

[0085] - a macropore volume measured by mercury porosimetry, with a diameter greater than 50 nm, less than 0.02 ml / g. an alkali or alkaline-earth compound content of less than 300 ppm wt and preferably less than 200 ppm wt.

[0086] The average mesopore diameter is defined as the diameter corresponding to the cancellation of the curve derived from the mercury intrusion volume obtained by mercury porosimetry for pore diameters between 3.7 and 50 nm.

[0087] Preferably, the dispersion of the metal in said preferred catalyst is advantageously between 5% and 100%, preferably between 5% and 90%, and most preferably between 10% and 90%. The dispersion, representing the fraction of metal accessible to the reagent relative to the total amount of metal in the catalyst, is advantageously measured, for example, by H2 / O2 titration or by transmission electron microscopy.

[0088] Preferably, the noble metal distribution coefficient of the preferred catalyst is greater than 0.1, preferably greater than 0.2, and most preferably greater than 0.4. The noble metal distribution represents the distribution of the metal within the catalyst grain, and the metal may be well or poorly dispersed. Thus, it is possible to obtain platinum that is poorly distributed (for example, detected in a ring whose thickness is significantly less than the radius of the grain) but well dispersed, meaning that all the platinum atoms located in the ring will be accessible to the reactants. The noble metal distribution coefficient can be measured using a Castaing microprobe.

[0089] The noble metal salt is advantageously introduced by one of the usual methods used to deposit the metal on the surface of a solid. One preferred method is dry impregnation, which consists of introducing the metal salt into a volume of solution equal to the pore volume of the mass of solid to be impregnated. Before the reduction operation, the catalyst can advantageously undergo calcination, for example, by treatment under dry air at a temperature of 300 to 750°C, and preferably at 450°C, for 0.25 to 10 hours, and preferably for 2 hours.

[0090] During this step c) the feed entering the reactor undergoes, in contact with the catalyst and in the presence of hydrogen, essentially hydrocracking reactions which, accompanied by hydroisomerization reactions of n-paraffins, will improve the quality of the products formed and more particularly the cold properties of kerosene, and also to selectively produce kerosene compared to naphtha which requires maintaining low conversion rates per pass.

[0091] According to the invention, the operating conditions of said step c) are adjusted so that the conversion by passing into products having boiling points greater than or equal to a temperature Tx into products having boiling points less than this same temperature Tx is less than 0.5, preferably less than 0.4, preferably less than 0.3 and preferably less than 0.2, Tx being between 250 and 350°C, preferably between 270 and 340°C and most preferably between 280 and 330°C.

[0092] The temperature Tx, and the resulting conversion rate, is (are) preferably chosen so as to maximize the kerosene yield of the process according to the invention while respecting the specifications of aviation kerosene.

[0093] The expected effect of the applied operating conditions and the pass conversion they generate is to limit overcracking into light products such as gas or naphtha, the latter being undesirable.

[0094] When the temperature increase required to maintain the target pass conversion becomes too great and the selectivity for light products, gas and / or gasoline increases, the catalytic cycle may be interrupted and the catalyst is discharged and then replaced with a new fresh catalyst with which the desired effect will again be found.

[0095] Pass-through conversion is defined as:

[0096] Conversion of Tx + in Tx- = [(% mass of Tx- effluent) - (% mass of Tx- load)] / [100 - (% mass of Tx- load)], with:

[0097] - % mass of Tx- effluent: mass percentage of compounds with boiling points lower than Tx in the hydrocracking effluent,

[0098] - % mass of Tx- charge: mass percentage of compounds having boiling points lower than Tx in the hydrocracking feed.

[0099] It is advantageously noted that the fraction of compounds having a boiling point in the naphtha range, therefore lower than those incorporable into the kerosene product, which is found in the hydrocracked effluent from step c) is then greatly reduced by limiting the conversion of the heavy fraction corresponding to the compounds with boiling points above Tx to levels below 0.5, preferably below 0.4, preferably less than or equal to 0.3 and preferably less than 0.2.

[0100] Step d)

[0101] The process according to the invention includes a step of separating d') the effluent from step c) into at least a hydrocracked hydrocarbon liquid fraction and a gaseous fraction.

[0102] This separation step (d') can advantageously be carried out using any methods and techniques known to those skilled in the art. Preferably, this separation step (d') is carried out in one or more separator vessels operating advantageously at a pressure as close as possible to the outlet pressure of hydrocracking step c), and at a temperature advantageously between the outlet temperature of the hydrocracking catalyst of step c) and 30°C.

[0103] Preferably, said gaseous fraction separated in said step d') advantageously comprises light C1-C4 gases, as well as hydrogen.

[0104] According to the invention, said separation steps b') and d') can advantageously be carried out in the same separation unit or in separate separation units, and preferably in the same separation unit.

[0105] In the preferred embodiment where steps b') and d') of separation are carried out in the same separation unit, all or part of the effluent from step a) and all or part of the effluent from step c) are treated together in said same separation unit.

[0106] The process according to the invention includes a step d) of fractionation in one or more steps of at least all or part of the hydrocracked hydrocarbon liquid fraction from step d').

[0107] Preferably, the entire hydrocracked hydrocarbon liquid fraction from step d') is fractionated in step d).

[0108] In another embodiment, part of the hydrocracked hydrocarbon liquid fraction from step d') is purged while the other part is fractionated in step d).

[0109] Step d) allows the fractionation of said hydrocracked hydrocarbon liquid fraction into at least one gaseous fraction advantageously comprising light C1-C4 gases, at least one gasoline or naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 100 and 160°C, at least one kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a residual heavy fraction having an initial boiling point above 250°C, said fractionation steps b) and d) advantageously being carried out in the same fractionation unit or in separate units.

[0110] This fractionation step can advantageously be carried out by atmospheric distillation and in some cases by combining atmospheric distillation and vacuum distillation.

[0111] Another embodiment of this fractionation step involves stripping the effluent from step d') prior to atmospheric fractionation in order to purge the gaseous fractions at the inlet of said atmospheric fractionation column. These fractionation steps b) and d) may advantageously be carried out in the same fractionation unit or in separate units. Preferably, fractionation steps b) and d) are carried out in the same unit.

[0112] In the preferred embodiment where fractionation steps b) and d) are carried out in the same fractionation unit, all or part of the hydrotreated hydrocarbon liquid fraction from step b') and all or part of the hydrocracked hydrocarbon liquid fraction from step d') are treated jointly in said same fractionation unit.

[0113] In a preferred embodiment in which fractionation steps b) and d) are carried out in the same unit, part of the hydrocracked hydrocarbon liquid fraction from step d') is purged while the other part is fractionated.

[0114] In a much preferred embodiment, the separation steps b') and d') are carried out in the same separation unit and the fractionation steps b) and d) are carried out in the same fractionation unit.

[0115] According to the invention, the process comprises a step e) of hydroisomerizing at least a part of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C from the fractionation step b) and of all or part of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C from the fractionation step d) in the case where said fractionation steps b) and d) are distinct. Step e) is carried out in the presence of a hydroisomerization catalyst operating at a temperature between 200 and 450°C, a total pressure between 1 and 15 MPa, and a total pressure at least 0.3 MPa lower than the total pressure used in hydrotreating step a) or hydrocracking step c), and a spatial velocity between 0.1 and 10 h 1, a hydrogen flow rate adjusted to obtain a ratio of between 100 and 2000 normal liters of hydrogen per liter of feed to produce a hydroisomerized effluent.

[0116] Preferably, said hydroisomerization step e) operates at a temperature between 250 and 450°C and preferably between 280 and 430°C, a total pressure between 1 and 10 MPa and preferably between 1 and 9 MPa, and a space velocity between 0.2 and 7 h -1 and preferably between 0.5 and 5 hours 1 , a hydrogen flow rate adjusted to obtain a ratio between 150 and 2000 normal liters of hydrogen per liter of charge and preferably between 150 and 1500 normal liters of hydrogen per liter of charge.

[0117] Preferably, said step e) operates at a total pressure at least 0.8 MPa lower than the total pressure implemented in hydrotreating step a) or hydrocracking step c), and preferably 0.8 to 2 MPa lower, and preferably 0.9 to 1.5 MPa lower, than the total pressure implemented in hydrotreating step a) or hydrocracking step c). The catalyst used in hydroisomerization step e) according to the invention is advantageously of the bifunctional type, that is, it has a hydro / dehydrogenating function and a hydroisomerizing function.

[0118] Preferably, said hydroisomerization catalyst comprises at least one noble metal from Group VIII of the periodic table and a support comprising at least one binder and at least one zeolite selected from the structural type zeolites TON, FER, EUO, AEL, *MRE, MTW, MOR, *BEA and ZEOLITH IZM-2, taken alone or in mixture.

[0119] The hydro / dehydrogenating function

[0120] Preferably the noble metal of group VIII of the catalyst used in step e) is chosen from palladium and platinum and is preferably platinum.

[0121] Advantageously, the hydro / dehydrogenating (metallic) element, preferably platinum, can be introduced onto the catalyst support by any method known to those skilled in the art, such as co-mixing, dry impregnation, or exchange impregnation.

[0122] According to one or more embodiments, the content of Group VIII noble metal, and preferably the platinum content, in the catalyst used in step e) is between 0.01% and 4% by weight, preferably between 0.05% and 2% by weight, relative to the total weight of said catalyst.

[0123] The catalyst used in step e) may also advantageously comprise at least one additional metal selected from the group formed by the metals of groups I1 IA, IVA and VII B of the periodic table of elements, and preferably selected from gallium, indium, tin and rhenium. This additional metal is preferably selected from indium, tin and rhenium.

[0124] Preferably, the content of at least one additional metal in the catalyst used in step e) is between 0.01% and 2% by weight, preferably between 0.05% and 1% by weight, relative to the total weight of said catalyst.

[0125] In one embodiment, the sulfur content in the hydroisomerization catalyst is such that the ratio of the number of moles of sulfur to the number of moles of at least one metal from Group VII IB is between 0.3 and 3. In one or more embodiments, the presence of sulfur in the catalyst originates from an optional sulfidation step of the hydroisomerization catalyst. In one or more embodiments, the presence of sulfur in the catalyst originates from potentially present impurities, such as, for example, in the alumina binder. In another embodiment, the catalyst does not contain sulfur.

[0126] The hydroisomerizing function.

[0127] Preferably, the catalyst contains at least one zeolite of the following structural types: TON (e.g., chosen from ZSM-22 and NU-10, alone or in mixtures) and / or FER (e.g., chosen from ZSM-35 and ferrierite, alone or in mixtures) and / or EUO (e.g., chosen from EU-1 and ZSM-50, alone or in mixtures) and / or AEL (e.g., SAPO-11) and / or *MRE (e.g., chosen from ZSM-48, ZBM-30, EU-2, and EU-11, alone or in mixtures) and / or MTW (e.g., chosen from ZSM-12, TPZ-12, Theta-3, NU-13, CZH-5, alone or in mixtures) and / or MOR (e.g., chosen from mordenite or LZ-211, alone or in mixtures) and / or *BEA (e.g., chosen from Beta or Tschernichite). The structural codes are defined in the International Zeolite Association (IZA: http: / / www.iza-structure.org / databases / ) classification. The zeolite may also be IZM-2, whose structural code is unknown.

[0128] Preferably, the catalyst contains at least one zeolite selected from IZM-2 zeolite and one MTW structural type zeolite preferably selected from ZSM-12, TPZ-12, Theta-3, NU-13, CZH-5, taken alone or in mixture.

[0129] Preferably, the catalyst contains at least one zeolite selected from IZM-2 and ZSM-12, taken alone or in mixture.

[0130] The zeolites are preferably in their predominantly acidic form, meaning that the atomic ratio between the monovalent compensating cation (e.g., sodium) and the aluminum inserted into the crystal lattice of the solid is advantageously less than 0.1, preferably less than 0.05, and most preferably less than 0.01. In one or more embodiments, the zeolites used in the hydroisomerization catalyst are advantageously calcined. In one or more embodiments, the zeolites are exchanged by at least one treatment with a solution of at least one ammonium salt to obtain the ammonium form of the zeolites, which, upon calcination, leads to the acidic form of the zeolites.

[0131] According to a preferred embodiment, the catalyst comprises a support comprising either IZM-2 zeolite alone or a support comprising ZSM-12 zeolite alone.

[0132] IZM-2 zeolite is a crystalline microporous solid whose crystal structure and preparation process are described in patent application FR2918050A1. The structural code of IZM-2 zeolite is not yet known. ZSM-12 zeolite is a crystalline microporous solid whose crystal structure is described on the website of the International Zeolyst Association (http: / / www.iza-structure.org / ). It is a one-dimensional zeolite with 12 MRs, and its structural code is MTW. A preparation process for this zeolite is described, for example, in the article "Synthesis of zeolite ZSM-12 in the system (MTEA)2O-Na2O-SiO2-Al2O3-H2O" by S. Ernst et al. (Zeolites, 7, 5, 458-462, DOI10.1016 / 0144-2449(87)90015-7).

[0133] Preferably, the catalyst used in step e) comprises a zeolite content of between 1% and 90% by weight, preferably between 3% and 80% by weight, and more preferably between 4% and 60% by weight, preferably between 4% and 30% by weight, and even more preferably between 4% and 20% by weight relative to the total weight of said catalyst. The binder.

[0134] Preferably, the binder in the catalyst support of step e) is amorphous or crystalline. Preferably, the binder used in the catalyst support of step e) is advantageously chosen from the group consisting of alumina, silica, silica-alumina, clays, titanium dioxide, boron dioxide, zirconia, and aluminates, alone or in mixtures. Preferably, the binder is alumina. Preferably, said binder may contain alumina in all its forms known to those skilled in the art, such as, for example, alpha, gamma, eta, and delta aluminas.

[0135] Preferably, the catalyst used in step e) comprises a binder content of between 10% and 99% by weight, relative to or total weight of said catalyst i.e., so as to ensure the complement to 100% by weight of the elements constituting the catalyst used in step e).

[0136] According to the invention, the catalyst support comprises zeolite mixed with a binder. The shaping of the support in the form of a mixture is preferably carried out by co-mixing, extrusion, and then heat treatment of the zeolite with the binder or a binder precursor, such as boehmite, which, upon heat treatment, is transformed into alumina.

[0137] A preferred catalyst for step e) comprises and is preferably made of platinum, and a support comprising and preferably made of ZSM-12 zeolite and an alumina binder.

[0138] Another preferred catalyst for step e) comprises and is preferably made of platinum, and a support comprising and preferably made of an IZM-2 zeolite and an alumina binder.

[0139] According to a preferred embodiment, the catalyst used in step e) more particularly comprises, and preferably consists of:

[0140] - from 1% to 90% by weight, preferably from 3% to 80% by weight and even more preferably from 4% to 60% by weight of zeolite;

[0141] - from 0.01% to 4% by weight, preferably from 0.05% to 2% by weight of at least one metal from group VIIIB, preferably platinum;

[0142] - possibly from 0.01% to 2% by weight, preferably from 0.05% to 1% by weight of at least one additional metal chosen from the group formed by the metals of groups 111 A, IVA and VI IB;

[0143] - possibly a sulfur content, preferably such that the ratio of the number of moles of sulfur to the number of moles of group VIIIB metal(s) is between 0.3 and 3; and

[0144] - possibly at least one binder, preferably alumina, ensuring the complement to 100% in the catalyst, relative to the total weight of the catalyst in step e).

[0145] Preferably, the catalyst used in step e) is shaped into cylindrical or multilobed extrudates such as bilobed, trilobed, or multilobed straight or twisted shapes. According to one or more embodiments, the catalyst used in step e) is shaped into crushed powders, tablets, rings, beads, or wheels. Other techniques besides extrusion, such as pelletizing or coating, may advantageously be used. The shaping may also advantageously be carried out in the presence of the various catalyst constituents, and the resulting mineral paste is extruded by pelletizing, shaping into beads using a rotary dripper or drum, drop coagulation, oil-drop, oil-up, or any other known process for agglomerating a powder containing alumina and possibly other ingredients selected from those mentioned above.

[0146] Furthermore, the substrates used in the process according to the present invention may advantageously have been treated, as is well known to those skilled in the art, with additives to facilitate shaping and / or improve the final mechanical properties of the substrates. Examples of such additives include cellulose, carboxymethyl cellulose, carboxyethyl cellulose, tall oil, xanthan gums, surfactants, flocculating agents such as polyacrylamides, carbon black, starches, stearic acid, polyacrylic alcohol, polyvinyl alcohol, biopolymers, glucose, polyethylene glycols, etc.

[0147] Extrusion can advantageously be carried out using any commercially available conventional tool. The dough resulting from the mixing process is advantageously extruded through a die, for example, using a piston or a single or double screw extrusion die. This extrusion step can advantageously be carried out by any method known to those skilled in the art.

[0148] The catalyst support implemented in step e) according to the present invention is then advantageously subjected to a drying step carried out according to any technique known to a person skilled in the art.

[0149] Preferably, drying is carried out under an airflow. This drying can also advantageously be carried out under a flow of any oxidizing, reducing, or inert gas. Preferably, drying is advantageously carried out between 50 and 180°C, most preferably between 60 and 150°C, and most preferably between 80 and 130°C.

[0150] The said support, possibly dried, then preferably undergoes a calcination stage.

[0151] The calcination step is advantageously carried out in the presence of molecular oxygen, for example by performing an air purge, at a temperature advantageously above 200°C and less than or equal to 1100°C. The calcination step can advantageously be carried out in a flow bed, a lick bed, or in a static atmosphere. For example, the kiln used can be a rotary kiln or a vertical kiln with radial flow beds. Preferably, the calcination step is carried out for more than one hour at 200°C and less than one hour at 1100°C. Calcination can advantageously be carried out in the presence of steam and / or in the presence of acidic or basic vapor. For example, calcination can be carried out under partial pressure of ammonia. Post-calcination treatments can optionally be carried out to improve the properties of the substrate, for example, its texture.

[0152] Preferably, the noble metal contained in the catalyst used in step e) can advantageously be reduced. One preferred method for conducting the metal reduction is treatment at a temperature between 150 and 650°C and a total pressure between 0.1 and 25 MPa. For example, a reduction might consist of a two-hour hold at 150°C, followed by a temperature ramp up to 450°C at a rate of 1°C / min, and then another two-hour hold at 450°C; during the reduction step, the hydrogen flow rate might be 1000 normal m³. 3 hydrogen / m 3 catalyst and the total pressure can be maintained constant at 0.1 MPa. Any reduction method can advantageously be considered, either in situ (the reduction of the catalyst is carried out in the same unit where the catalytic reaction is carried out), or ex situ (the reduction is carried out outside the unit where the catalytic reaction is carried out, before loading the catalyst into the unit).

[0153] The operating conditions implemented in step e) allow obtaining an isomerized effluent containing little or no olefinic compounds and oxygenated compounds.

[0154] The isomerized effluent from step e) is then sent to the separation step h').

[0155] According to the invention, the process includes recycling all or part of the residual heavy fraction having an initial boiling point above 250°C in step c) of hydrocracking. In the variant where steps b) and d) are carried out in a single fractionation unit, the hydrocraced effluent from step d'), optionally purged, is advantageously recycled in said common fractionation unit mixed with all or part of the effluent from step b') of hydrotreatment.

[0156] In this case, the said common fractionation unit makes it possible to obtain at least one heavy fraction which includes the heavy fraction of the hydrotreated effluent and the residual heavy fraction of the hydrocracked effluent.

[0157] In said variant, said heavy fraction which is sent to the hydrocracking step c) comprises the heavy fraction of the hydrotreated effluent and the residual heavy fraction of the hydrocracking effluent.

[0158] In the variant where steps b) and d) are carried out in separate fractionation units, only the hydrocracked effluent from step d'), possibly part of which is purged, is fractionated in said fractionation step d) to obtain at least one residual heavy fraction having an initial boiling point above 250°C.

[0159] Preferably, all or part of said residual heavy fraction, possibly including a portion that is purged, is advantageously recycled directly in said hydrocracking step c). Recycling the residual heavy fraction is a key step of the invention because this recycling step allows at least part of the residual heavy fraction to be converted into at least a kerosene fraction. This increases the kerosene yield of the process. Furthermore, it is more advantageous to operate with low conversion per pass and with recycling than to attempt to convert more of the heavy fraction in a single step without recycling, since the latter would lead to overcracking the product and thus forming a significant quantity of gas and / or gasoline.

[0160] The said recycle is advantageously operated with a rate corresponding to 1 to 19 times the mass flow rate of fresh feed from the hydrotreatment step a) and separated in step b). Preferably, the recycle rate is between 2 and 9 and even more preferably, the recycle rate is operated between 3 and 6.

[0161] The recycle rate is defined as the ratio of the mass flow rate of feedstock entering the hydrocracking stage (c), i.e., the cumulative flow rate of the heavy fraction and the residual heavy fraction to the flow rate of the heavy fraction. It can be directly calculated from the per-pass conversion previously defined according to the following formula:

[0162] Recycle Tx = 1 / (Conversion of Tx + (in Tx)

[0163] The recycle rate is then advantageously between 2 and 20, preferably it is between 3 and 10 and even more preferably it is between 4 and 6.

[0164] An optional purging of a portion of the hydrocracked effluent from step c) may be carried out. The purging constitutes a fraction that will not be recycled in any step of the process according to the invention, and in particular neither to the hydrocracking step c) nor to the hydroisomerization step e).

[0165] Generally, it is a part of the residual heavy fraction and advantageously the heaviest fraction of said residual heavy fraction.

[0166] The implementation of purging makes it possible to maximize the amount of residual heavy fraction recycled to the hydrocracking step c) while maintaining process performance, as any heavy compounds refractory to hydrocracking that may accumulate during the recycle steps can be eliminated by purging.

[0167] This purging can advantageously be carried out upstream or downstream of the fractionation step and preferably downstream of the fractionation step d) when steps b) and d) are carried out in separate fractionation units.

[0168] In another embodiment, purging is carried out during, upstream, or downstream of the fractionation step, and preferably downstream of the fractionation step when steps b) and d) are carried out in the same fractionation unit. Preferably, the purging corresponds to less than 10% by weight of the total feed entering hydrotreating step a), most preferably less than 7% by weight, most preferably less than 5% by weight, and even more preferably less than 3% by weight.

[0169] The purging can be carried out by all methods known to a person skilled in the art and may, for example, consist of a draw-off or a simple flash, the separation temperature then being chosen as high as possible, preferably above 300°C, preferably above 370°C, very preferably above 450°C and even more preferably above 540°C.

[0170] The effluent from step c), purge deducted is then separated and fractionated.

[0171] Step h')

[0172] The process according to the invention includes a separation step h') of the effluent from step e) into at least a hydrocracked hydrocarbon liquid fraction and a gaseous fraction.

[0173] Said separation step h'), can advantageously be carried out according to all methods and techniques known to those skilled in the art. Preferably, said separation step h') is carried out in one or more separating vessels advantageously operating at a pressure as close as possible to the outlet pressure of the hydroisomerization step e), and at a temperature advantageously between the outlet temperature of the hydroisomerization catalyst of step e) and 30°C.

[0174] Preferably, said gaseous fraction separated in said step h') advantageously comprises light C1-C4 gases, as well as hydrogen.

[0175] Said separation step h') is advantageously carried out in a separation unit distinct from the separation units of steps b') and d').

[0176] The process according to the invention includes a step h) of fractionating all or part of the hydroisomerized hydrocarbon liquid fraction from step h') to obtain at least one gaseous fraction advantageously comprising light C1-C4 gases, at least one naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 120 and 160°C, and at least one kerosene fraction having an initial boiling point between 120 and 160°C.

[0177] At the end of this fractionation step h), the resulting kerosene meets all the specifications required for use as aviation fuel according to current standards. In the preferred embodiment, fractionation steps b) and d) are carried out in separate fractionation units, and where light kerosene fraction(s) is / are obtained from said fractionation steps b) and / or d), said light kerosene fraction(s) is / are blended with the kerosene fraction obtained from the final fractionation step h).

[0178] The process according to the invention makes it possible to obtain a final kerosene cut, consisting of the kerosene fraction from the fractionation step h) only or possibly consisting of said kerosene fraction from the fractionation step h) mixed with a light kerosene fraction according to the preferred embodiments described above.

[0179] A mass balance analysis demonstrates excellent selectivity of the process towards the final kerosene fraction, with unwanted fractions produced in reduced proportions compared to other implementations described in the literature, to our knowledge. In particular, the yield of fractions with a boiling point higher than the target endpoint of kerosene has been minimized, as required by the invention, with purging being less than 10% by weight of the incoming feed mass in step a). Furthermore, the yield of light fractions from cracking during any of steps a), c), or e) is also extremely low due to the serial treatment of the heavy fraction of the incoming feed, first with a hydrocracking catalyst with a low conversion rate per pass, and then with a hydroisomerization catalyst that is selective towards isomerization at the expense of cracking.

[0180] The process according to the invention comprises a step i) of compression in a single compression section of the gaseous fraction from step h'), the gaseous effluent from step i) being recycled to step a) and / or c) and / or e) and at least part and preferably all of the gaseous fractions from steps b') being sent to step c) of hydrocracking and / or to step e) of hydroisomerization without passing through said step i) of compression and / or at least part and preferably all of the gaseous fraction from d') being sent to step e) of hydroisomerization without passing through said step i) of compression.

[0181] The gaseous effluent from step i) is recycled to step a) and / or c) to provide the hydrogen flow rate described in these different steps. The same applies to sending the gaseous fractions from steps b') and d') to the hydroisomerization step e).

[0182] According to one embodiment of the invention, at least a portion, and preferably all, of the gaseous effluent from step b') is sent to hydrocracking step c) without passing through said compression step i), and at least a portion, and preferably all, of the gaseous fraction from d') is sent to hydroisomerization step e) without passing through said compression step i). According to another embodiment of the invention, at least a portion, and preferably all, of the gaseous effluent from step b') is sent to hydroisomerization step e) without passing through said compression step i), and at least a portion, and preferably all, of the gaseous fraction from d') is sent to hydroisomerization step e) without passing through said compression step i.

[0183] In all the variants described below, as well as in the diagram of the invention, it is possible to adjust the hydrogen flow rate at the different stages a), c) and e) by allowing the gas flow to partially bypass stages a), and / or c) and / or e).

[0184] Advantageously, hydrogen is added to compensate for the hydrogen consumption that occurs during steps a), c), and e). This hydrogen addition can be carried out at any of the catalytic steps mentioned. Preferably, it takes place at the hydroisomerization step.

[0185] List of figures

[0186] [Fig. 1]

[0187] Figure 1 illustrates an implementation of the process according to the prior art in which the gaseous fractions from the separation steps b'), d') and h') are directly sent to a compression step i) and the gaseous effluent from step i) is recycled in steps a), c) and e).

[0188] [Fig. 2]

[0189] Figure 2 illustrates the implementation of the process according to an embodiment of the invention where a) and c) are operated in series on the gas recycle: the gaseous fraction from b') is sent to the hydrocracking step c) without going through said compression step i) and the gaseous fraction from d') is sent to the hydroisomerization step e) without going through compression step i).

[0190] [Fig. 3]

[0191] Figure 3 illustrates the implementation of the process according to an embodiment of the invention where steps a) and c) are carried out in parallel on the gas recycle: the gaseous fraction from b') is sent to the hydroisomerization step e) without going through the compression step i) and the gaseous fraction from d') is sent to the hydroisomerization step e) without going through the compression step i).

[0192] [Fig. 4]

[0193] Figure 4 illustrates the implementation of the process according to an embodiment of the invention where the separation steps b') and d') are carried out in the same separation unit and the fractionation steps b) and d) are carried out in the same fractionation unit; in this case, the gaseous fraction from the merged steps b') / d') is sent directly to the hydroisomerization step e) without passing through said compression step i).

[0194] In Figure 1, the synthesis gas 1, composed mainly of carbon monoxide and hydrogen, is directed to a Fischer-Tropsch synthesis unit (A'). At the outlet of the unit (A'), the effluent is divided into two streams: the hydrocarbon fraction 2, which includes the cold condensate and the heavy fraction corresponding to the waxes and representing the paraffinic feed produced by Fischer-Tropsch synthesis, and the gaseous fraction 3, which is not cold condensable and can be treated directly or after possible reprocessing in the Fisher-Tropsch synthesis unit (recycle).Fraction 2 (paraffinic feedstock) is sent to the hydrotreating unit (A), from which the hydrocarbon effluent 4 is sent to the separation unit (B'). This unit separates water via pipe 5, a gaseous fraction 6 containing hydrogen, which is sent to the compression unit (I), and a hydrotreated hydrocarbon liquid fraction 7, which is fractionated in the fractionation unit (B / D) into a gas fraction 9, a naphtha fraction 10, a kerosene fraction 11, and a heavy fraction 8. The heavy fraction 8 is sent to a hydrocracking unit (C), where a partially converted effluent 12 is produced and separated into two streams in a separation unit (D'). The hydrogen-containing gaseous fraction 13 from D' is directed to the recompression unit (I) after being mixed with the gaseous fractions 6 and 17 from the separation units B' and H'.The hydrocracked hydrocarbon liquid fraction 14 from unit D' is then injected, together with the hydrotreated hydrocarbon liquid fraction 7 from separation unit B', into fractionation unit B / D, with fractions 7 and 14 forming fraction 15. The kerosene hydrocarbon fraction 11 produced by fractionation unit (B) is sent to a hydroisomerization unit E, and the effluent 16 from E is sent to a separation unit (H') and separated into two streams. The hydrogen-containing gaseous fraction 17 from separation unit H' is sent to the compressor (I) after mixing with the gaseous fractions 6 and 13 from units B' and D'. The hydroisomerized hydrocarbon liquid fraction 18 is then fractionated in a fractionation unit (H) at the end of which three fractions are produced: a fraction corresponding to the kerosene cut 19, a naphtha fraction 20 and finally a gaseous fraction 21.

[0195] The gaseous effluent from compression unit I is then divided into 3 fractions 22, 23 and 24, supplying units A, C and E respectively. Finally, a supply of fresh hydrogen, 25, is used to supply units A, C, E in addition to the recycled gas from compressor I.

[0196] Figure 2 is similar to Figure 1, with the following exceptions:

[0197] The gaseous fraction 6 from unit B' is not sent to compression unit I but to hydrocracking unit C

[0198] The gaseous fraction 13 from unit D' is not sent to the compression unit I but to the hydroisomerization unit E. The gaseous effluent from the compression unit I is not divided into several streams but only stream 22 is sent to the hydrotreatment unit A.

[0199] - Fresh hydrogen 25 is only sent to the hydroisomerization unit E.

[0200] Figure 3 is similar to Figure 1, with the following exceptions:

[0201] The gaseous fraction 6 from unit B' is not sent to compression unit I but to hydroisomerization unit E

[0202] The gaseous fraction 13 from unit D' is not sent to the compression unit I but to the hydroisomerization unit E. The gaseous effluent from the compression unit I is divided into two streams 22 and 23 which are sent respectively to the hydrotreatment unit A and the hydrocracking unit C, but not to unit E).

[0203] - Fresh hydrogen 25 is only sent to the hydroisomerization unit E.

[0204] Figure 4 is similar to Figure 1, with the following exceptions:

[0205] - there is only one common separation unit, called B7D', for the effluents from unit A of hydrotreatment (effluent 4) and from unit C of hydrocracking (effluent 12), this unit thus generates water (5), a gaseous fraction (6) and a liquid fraction (15)

[0206] - The gaseous fraction 6 from unit B7D' is not directed towards the compression unit I but towards the hydroisomerization unit E.

[0207] The output of the compression unit I is split into two streams 22 and 23 directed respectively towards the hydrotreating unit A and the hydrocracking unit C and.

[0208] - Fresh hydrogen 25 is only sent to the hydroisomerization unit E.

[0209] The examples illustrate the invention without limiting its scope.

[0210] Example 1: preparation of hydrotreating catalyst C1 (compliant).

[0211] The catalyst is an industrial nickel, molybdenum and phosphorus on alumina catalyst with molybdenum oxide MoOs content of 22% by weight, nickel oxide NiO content of 4% by weight and phosphorus oxide P2O5 content of 5% by weight relative to the total weight of the finished catalyst.

[0212] Example 2: Preparation of the C2 hydrocracking catalyst (compliant).

[0213] The silica-alumina powder is prepared according to the synthesis protocol described in patent EP1 415 712A. The quantities of orthosilicic acid and aluminum hydrate are chosen to obtain a composition of 70% by weight of alumina (Al₂O₃) and 30% by weight of silica (SiO₂) in the final solid. This mixture is rapidly homogenized in a commercial colloidal mill in the presence of nitric acid so that the nitric acid content of the suspension exiting the mill is 8% relative to the silica-alumina solid. The suspension is then conventionally dried in a spray dryer from 300°C to 60°C. The powder thus prepared is shaped in a Z-arm in the presence of 8% nitric acid relative to the anhydrous product. Extrusion is carried out by passing the paste through a die equipped with orifices of 1.4 mm diameter.The extrudates thus obtained are dried in an oven at 140°C then calcined under a flow of dry air at 550°C and then calcined at 850°C in the presence of water vapor.

[0214] The characteristics of the substrate thus prepared are as follows:

[0215] - an average mesopore diameter of 8.0 nm, measured by mercury porosimetry

[0216] - a total pore volume measured by mercury porosimetry of 0.49 ml / g,

[0217] - a mesoporous volume measured by mercury porosimetry of 0.48 ml / g,

[0218] - a macropore volume, with a diameter greater than 50 nm, less than 0.02 ml / g,

[0219] - a BET area of ​​235 m 2 / g.

[0220] The silica-alumina extrudates are then subjected to a dry impregnation step with an aqueous solution of platinum tetramine nitrate, left to mature in a water-cooled maturing tank for 24 hours at room temperature, and then calcined for two hours under dry air in a flow bed at 450°C (temperature ramp of 5°C / min). The platinum content by weight of the finished catalyst after calcination is 0.16%, its dispersion measured by H2 / O2 titration is 33%, and its distribution coefficient measured by Castaing microprobe is 0.96.

[0221] Example 3: Preparation of a C3 hydroisomerization catalyst (compliant).

[0222] Zeolite ZSM-12.

[0223] The ZSM-12 zeolite was supplied by the company Zeolyst. The solid was analyzed by X-ray diffraction and identified as being composed of ZSM-12 zeolite. Characterizations using NMR methods of the 27AI, X-ray fluorescence, and ICP allow access to the following results for ZSM-12:

[0224] - weight percentage of hexacoordinate aluminum atoms Al VI : 0%;

[0225] - ratio of the number of moles of silicon divided by the number of moles of aluminum lattice, in mole / mole, Si / Al: 43;

[0226] - ratio of the number of moles of sodium divided by the number of moles of aluminum lattice, in mole / mole, Na / Al: 0.009.

[0227] Preparation of the ZSM-12 / alumina support.

[0228] The ZSM-12 / alumina support is obtained by mixing and extruding ZSM-12 zeolite with Pural SB3 alumina gel. The mixed paste is extruded through a 1.8 mm diameter quadrilobe die. After drying overnight in an oven at 110°C, the extrudates are calcined at 500°C for two hours (temperature ramp of 5°C / min) in a flow bed under dry air (2 normal liters per hour per gram of solid). The weight content of ZSM-12 zeolite in the support after calcination is 6 wt%.

[0229] Platinum impregnation on the ZSM-12 / alumina support.

[0230] Platinum impregnation is carried out by dry impregnation of the support with an aqueous solution containing platinum tetramine nitrate Pt(NH3)4(NO3)2. After impregnation, the solid is left to mature for at least five hours in laboratory air and then dried overnight in an oven at 110°C. Finally, a calcination step is performed under a flow of dry air (2 normal liters per hour per gram of solid) in a tubular furnace under the following conditions:

[0231] - temperature rise from ambient to 450°C at 5°C / min;

[0232] - two-hour plateau at 450°C;

[0233] - descent to ambient temperature.

[0234] The Pt content measured by FX on the calcined C4 catalyst is 0.31% by weight, its dispersion measured by H2 / O2 titration is 38%, its distribution coefficient measured by Castaing microprobe is 0.87.

[0235] Example 4: Kerosene production process according to prior art.

[0236] Example 4 is illustrated in Figure 1. In particular, the recycle gas ensuring the hydrogen-to-charge ratio from compressor I) is separated into 3 streams supplying respectively the 3 catalytic units A, C and E, each operated at the same pressure of 6.5 MPa.

[0237] Step a) hydrotreating of the paraffinic feedstock (catalytic unit A).

[0238] A paraffinic feed from the Fischer-Tropsch synthesis has the characteristics given in Table 1. This feed includes cold condensates and waxes.

[0239] Table 1: Characteristics of the charge from the Fischer-Tropsch synthesis [Table 1]

[0240] The total atomic oxygen content in said fraction is measured by the infrared absorption technique described in patent application US2009 / 0018374A1.

[0241] Oxygen content represents the concentration of molecules containing at least one oxygen atom present in the heavy fraction and is expressed as a weight percentage of atomic oxygen relative to the total pass of said fraction. Oxygen content is measured by gas chromatography.

[0242] The paraffin charge is treated in a flow bed on the C1 hydrotreating catalyst under operating conditions which allow the removal of olefinic and oxygenated compounds as well as traces of nitrogen.

[0243] The selected operating conditions are as follows: hourly volumetric rate WH (charge volume / catalyst volume / hour) = 2 h 1, total working pressure: 6.5 MPa, hydrogen / charge ratio: 700 normal liters / liter, o The hydrogen used here corresponds to a small top-up of fresh hydrogen corresponding to the hydrogen consumption during hydrotreating step a), the rest of the hydrogen comes from step I of recycling gas compression. temperature: 330°C.

[0244] Before testing, catalyst C1 undergoes a reduction stage under the following operating conditions: pure hydrogen flow rate: 1600 normal liters per hour per liter of catalyst, temperature rise from ambient to 120°C: 10°C / min, one-hour hold at 120°C, temperature rise from 120°C to 450°C at 5°C / min, two-hour hold at 450°C, total pressure: 6.5 MPa

[0245] Step b') separation of the hydrotreated paraffinic filler (separation unit B')

[0246] The hydrotreated effluent then undergoes a flash separation and settling step. Following this separation, carbon monoxide and / or carbon dioxide, water, ammonia, and a gaseous fraction comprising hydrocarbons with fewer than five atoms formed during hydrotreatment are separated. A hydrotreated hydrocarbon liquid fraction consisting of paraffins is also separated. Step b) Fractionation of the hydrotreated and separated paraffinic feedstock (fractionation unit B / D)

[0247] The hydrotreated paraffinic hydrocarbon liquid fraction, having undergone the flash and decantation step in step b'), is fractionated by atmospheric distillation into different hydrocarbon cuts, namely light gases from Ci to C4, a naphtha cut with an initial boiling point of 35°C and a final boiling point of 120°C, a kerosene cut with an initial boiling point of 120°C and a final boiling point of 300°C, and a heavy fraction with an initial boiling point greater than 300°C.

[0248] Step c) hydrocracking of the heavy fraction from step b), (catalytic unit C)

[0249] The heavy fraction from step b) mixed with the residual heavy fraction from step d) below constitutes the hydrocracking feed sent to the hydrocracking catalyst C2.

[0250] Before testing, the C2 catalyst undergoes a reduction stage under the following operating conditions: hydrogen flow rate: 1600 normal liters per hour per liter of catalyst, temperature rise from ambient to 120°C: 10°C / min, one-hour hold at 120°C, temperature rise from 120°C to 450°C at 5°C / min, two-hour hold at 450°C, pressure: 6.5 MPa

[0251] After reduction, the catalytic test is carried out under the following conditions: total pressure of 6.5 MPa, hydrogen-to-charge ratio of 800 normal liters / liter, the hydrogen used here consists of fresh hydrogen replenishment corresponding to the hydrogen consumption during the hydrocracking step c), and hydrogen from unit I of the recycle gas compression, volumetric velocity hour (VVH) equal to 1 h -1 .

[0252] The hydrocracking feedstock is treated in a flow bed. The conversion of the fraction to 300°C + is taken as equal to:

[0253] C(300°C+ ) = [ (% of 300°C - effluents ) - (% of 300°C - load) ] / [ 100 - (% of 300°C - load)] with

[0254] % of 300°C _ effluents = mass percentage of compounds with boiling points below 300°C in the effluents, and

[0255] % of 300°C' charge = mass percentage of compounds having boiling points below 300°C in the hydrocracking feed.

[0256] The reaction temperature is adjusted to 330°C in order to obtain a conversion level of the fraction at 300°C + equal to 0.2. This corresponds to a recycle rate of 5. Step d') separation of the hydrocracking effluent (separation unit D')

[0257] The hydrocracked effluent from step c) then undergoes a flash separation and settling step. Following this separation, carbon monoxide, carbon dioxide, water, ammonia, and a gaseous fraction comprising hydrocarbons with fewer than five atoms that may have formed during hydrotreatment are separated. A hydrocracked hydrocarbon liquid fraction is also separated.

[0258] Step d) Fractionation of the separated hydrocracking effluent (fractionation unit B / D)

[0259] The hydrocracked hydrocarbon liquid fraction obtained from step c) and having undergone the flash and settling steps in step d') is fractionated by atmospheric distillation into different hydrocarbon fractions, namely light gases from C1 to C4, a naphtha fraction with an initial boiling point of 35°C and a final boiling point of 120°C, a kerosene fraction with an initial boiling point of 120°C and a final boiling point of 300°C, and a residual heavy fraction with an initial boiling point above 300°C. This residual heavy fraction is then recycled to the hydrocracking step c). The fractionation of the hydrocracking effluent is carried out in the same distillation column as that used in step b). Therefore, there is a joint fractionation of the hydrocracking effluent and the hydrotreated and separated paraffinic hydrocarbon liquid fraction.

[0260] Step e) hydroisomerization of the kerosene fraction from step b), (catalytic unit E)

[0261] The kerosene fraction from step b) constitutes the hydroisomerization feed and is sent to the hydroisomerization catalyst C3. Before testing, the catalyst C3 undergoes a reduction step under the following operating conditions: hydrogen flow rate: 1600 normal liters per hour per liter of catalyst, temperature rise from ambient to 120°C: 10°C / min, one-hour hold at 120°C, rise from 120°C to 450°C at 5°C / min, two-hour hold at 450°C, pressure: 6.5 MPa.

[0262] The hydroisomerization charge is treated in a flow bed.

[0263] After reduction, the catalytic test is carried out under the following conditions: total pressure of 6.5 MPa, hydrogen-to-charge ratio of 800 normal liters / liter. The hydrogen used here consists of a small addition of fresh hydrogen corresponding to the hydrogen consumption during the hydroisomerization step e), and hydrogen from unit I of the recycle gas compression, with a volumetric flow rate per hour (WH) equal to 2 h 1 The temperature is adjusted to obtain a value of -40°C for the disappearance temperature of the crystals for the kerosene obtained after the fractionation step h).

[0264] Step h') Separation of the hydroisomerization effluent. (Separation unit H')

[0265] The hydroisomerized effluent then undergoes a flash separation and settling step. Following this separation, carbon monoxide and / or carbon dioxide, water, ammonia, and a gaseous fraction comprising hydrocarbons with fewer than five atoms formed during hydroisomerization are separated. A hydroisomerized hydrocarbon liquid fraction is also separated.

[0266] Step h) Fractionation of the separated hydroisomerization effluent (fractionation unit H). The hydroisomerized hydrocarbon liquid fraction obtained at the end of step h') is fractionated by atmospheric distillation into different hydrocarbon cuts, namely light gases from C1 to C4, a naphtha cut with an initial boiling point of 35°C and a final boiling point of 120°C, and a kerosene cut with an initial boiling point of 120°C and a final boiling point of 300°C. This fractionation is carried out in an atmospheric distillation unit H.

[0267] Material balances performed over 24 hours allow the calculation of yields in different cuts: light gas yield: mass of C4 Ci gas / mass of paraffinic feed * 100, naphtha cut yield: mass of liquid effluent with an initial boiling point of 35°C and a final boiling point of 120°C / mass of paraffinic feed * 100, kerosene cut yield: mass of liquid effluent with an initial boiling point of 120°C and a final boiling point of 300°C / mass of paraffinic feed * 100, or the mass of C4 Ci gas corresponds to the quantity of C4 Ci gas generated during 24 hours at the end of step a) of hydrotreating the paraffin feed from the Fischer-Tropsch synthesis,of steps b) and d) of joint fractionation of the hydrotreatment effluent and separation of the paraffin feed from the Fischer-Tropsch synthesis and the hydroconversion effluent and of step h) of fractionation of the hydroisomerization effluent; the mass of paraffin feed corresponds to the quantity of paraffin feed from the Fischer-Tropsch synthesis consumed during 24 hours,the mass of liquid effluent with an initial boiling point of 35°C and a final boiling point of 120°C corresponds to the quantity of liquid effluent with an initial boiling point of 35°C and a final boiling point of 120°C generated during 24 hours at the end of steps b) and d) of joint fractionation of the hydrotreating effluent and separation of the paraffinic feed from the Fischer-Tropsch synthesis and the hydrocracking effluent and of step h) of fractionation of the hydroisomerization effluent and the mass of liquid effluent with an initial boiling point of 120°C and a final boiling point of 300°C corresponds to the quantity of liquid effluent with an initial boiling point of 120°C and a final boiling point of 300°C generated during 24 hours at the end of step h) of fractionation of the hydroisomerization effluent. The disappearance point of the kerosene crystals is then measured according to ASTM D5972. Step i) compression of the recycled gas from steps b'), d') and h'),(Compression unit I) The gaseous fractions from steps b'), d') and h') are sent to a compression unit I.

[0268] The gaseous effluent from the compression unit I is then recycled to the hydrotreatment unit A, hydrocracking unit C and hydroisomerization unit E.

[0269] Table 2 reports the yields in different cuts as well as the properties of the kerosene cut obtained.

[0270] Example 5: Kerosene production process according to an embodiment of the invention

[0271] Example 5 is illustrated in Figure 2. In particular, the recycle gas ensuring the hydrogen-to-charge ratio from compressor I) feeds: firstly, the catalytic unit A, then the gaseous effluent collected in step b') feeds the catalytic unit C, operated at a lower pressure than the catalytic unit A, then the gaseous effluent collected in step d') feeds the catalytic unit E, operated at a lower pressure than the catalytic unit C, finally, the gaseous effluent collected in step h') returns to the recycle compressor I.

[0272] Step a) hydrotreating of the paraffinic feedstock, (catalytic unit A)

[0273] Identical to example 1, except that the total operating pressure is set at 7.2 MPa. The reaction temperature is adjusted to maintain the same level of performance as in example 1.

[0274] The hydrogen flow rate comes entirely from stage I of recycling gas compression.

[0275] With the same catalyst volume as in example 1, the temperature is adjusted to allow the elimination of olefmic and oxygenated compounds as well as traces of nitrogen identical to example 1.

[0276] Step b') separation of the hydrotreated paraffinic filler (separation unit B') Identical to example 1.

[0277] Step b) fractionation of the hydrotreated and separated paraffinic filler, (fractionation unit

[0278] B / D)

[0279] Identical to example 1. Step c) hydrocracking of the heavy fraction from step b), (catalytic unit C) Identical to example 1, in particular the operating pressure of 6.5 MPa remains unchanged. The hydrogen flow rate consists entirely of hydrogen from step b').

[0280] Step d') separation of the hydrocracking effluent (separation unit D') Identical to example 1.

[0281] Step d) fractionation of the separated hydrocracking effluent, (fractionation unit B / D) Identical to example 1.

[0282] Step e) Hydroisomerization of the kerosene fraction from step b), (catalytic unit E) Identical to example 1, except that the total operating pressure is reduced to 5.8 MPa. The hydrogen used here corresponds to a small addition of fresh hydrogen corresponding to the hydrogen consumed during the hydrotreating steps a), hydrocracking c), and hydroisomerization e; the remainder of the hydrogen comes from step I, compression of the recycled gas.

[0283] With the same catalyst volume as in example 1, the temperature is adjusted to obtain a value of -40°C for the disappearance temperature of the crystals for the kerosene obtained after the fractionation step h).

[0284] Step h') Separation of the hydroisomerization effluent. (Separation unit H')

[0285] Identical to example 1

[0286] Step h) fractionation of the separated hydroisomerization effluent, (fractionation unit H) Identical to example 1.

[0287] Step i) of compression (compression unit I)

[0288] The gaseous fraction from step h') is sent to the recycle compressor I and the gaseous effluent from step i) is recycled to step a) of hydrotreatment.

[0289] Example 6: Kerosene production process according to an embodiment of the invention

[0290] Example 6 is illustrated in Figure 3. In particular, the recycle gas ensuring the hydrogen-to-charge ratio from compressor I) feeds: initially, in parallel, the catalytic units A and C, thus operating at the same pressure of 6.5 MPa; then the gaseous effluents collected in steps b') and d') feed the catalytic unit E, operating at a lower pressure than the catalytic units A and C; finally, the gaseous effluent collected in step h') returns to the recycle compressor I.

[0291] Step a) hydrotreating of the paraffinic feedstock, (catalytic unit A)

[0292] Identical to example 1, in particular the operating pressure of 6.5 MPa remains unchanged. The hydrogen used here corresponds to a small addition of fresh hydrogen; the rest of the hydrogen comes from step I of the recycled gas compression.

[0293] Step b') separation of the hydrotreated paraffinic filler (separation unit B')

[0294] Identical to example 1.

[0295] Step b) fractionation of the hydrotreated and separated paraffinic filler, (fractionation unit B / D)

[0296] Identical to example 1.

[0297] Step c) hydrocracking of the heavy fraction from step b), (catalytic unit C)

[0298] Identical to example 1, in particular the operating pressure of 6.5 MPa remains unchanged.

[0299] The hydrogen used here corresponds to a small addition of fresh hydrogen; the rest of the hydrogen comes from step I of the recycled gas compression. The addition of fresh hydrogen supplied in steps a) and c) corresponds to the hydrogen consumption of all steps a), c) and e).

[0300] Step d') Separation of the hydrocracking effluent (separation unit D')

[0301] Identical to example 1.

[0302] Step d) fractionation of the separated hydrocracking effluent, (fractionation unit B / D) Identical to example 1.

[0303] Step e) Hydroisomerization of the kerosene fraction from step b), (catalytic unit E) Identical to example 1, except that the total operating pressure is reduced to 5.8 MPa. The hydrogen flow rate consists entirely of hydrogen from the flash and settling units B' and D'.

[0304] With the same catalyst volume as in Example 1, the temperature is adjusted to obtain a value of -40°C for the crystal disappearance temperature of the kerosene obtained after fractionation step h). Step h') separation of the hydroisomerization effluent. (separation unit H')

[0305] Identical to example 1

[0306] Step h) fractionation of the separated hydroisomerization effluent, (fractionation unit H) Identical to example 1.

[0307] Step i) of compression (compression unit I)

[0308] The gaseous fraction from step h') is sent to the recycle compressor I and the gaseous effluent from step i) is recycled to step a) of hydrotreating and to step c) of hydrocracking.

[0309] Table 2: Yields in different cuts and properties of the kerosene cuts obtained for the different examples of the invention.

[0310] [Table 2]

[0311] The examples provided highlight the importance of carrying out the process according to the invention.

[0312] In particular, a comparison of prior art example 4 and example 5 demonstrates that the activity of catalyst C3 is favored at a lower operating pressure than that of catalysts C1 and C2. This results in either a lower operating temperature for the catalytic unit E (and therefore lower associated operating costs), or a lower catalytic volume required for the catalytic unit (and therefore lower associated capital costs). Conversely, the operation according to example 4 leads to a significant increase in the power required by the recycle compressor I in step i).

[0313] Example 5, according to one method of the invention, demonstrates the interest of the invention in improving the activity of the catalyst C3. This results in either a lower operating temperature for the catalytic unit E (and therefore lower associated operating costs), or a lower catalytic volume required for the catalytic unit (and therefore lower associated investment costs).

[0314] It should be noted that this particular implementation of the invention also allows for a reduction in the power of the recycle compressor compared to Example 4. Example 6, according to another operating mode of the invention, demonstrates the advantage of the invention in improving the activity of catalyst C3. This results in either a lower operating temperature for the catalytic unit E (and therefore lower associated operating costs), or a smaller catalytic volume required for the catalytic unit (and therefore lower associated capital costs).

Claims

DEMANDS 1. A process for producing kerosene from a paraffinic feedstock produced by Fischer-Tropsch synthesis, comprising at least the following steps and preferably consisting of: step a) hydrotreating at least a portion and preferably all of the paraffinic feedstock produced by Fischer-Tropsch synthesis in the presence of a hydrotreating catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2.5 and 15 MPa, with a hydrogen flow rate adjusted to obtain a ratio between 100 and 3000 normal liters of hydrogen per liter of feedstock, and at a volumetric rate per hour between 0.1 and 40 h 1, step b') the separation of the effluent from step a) into at least an aqueous fraction consisting of at least some of the water formed during said step a) and preferably all of the water formed, a hydrotreated hydrocarbon liquid fraction and a gaseous fraction, step b) the fractionation in one or more steps of the hydrotreated hydrocarbon liquid fraction from step b') into at least a gaseous fraction, a naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 100 and 160°C, at least a kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a heavy fraction having an initial boiling point above 250°C, step c) the hydrocracking of all of said heavy fraction having an initial boiling point above 250°C from step b) to produce a hydrocracked effluent,in the presence of a hydrocracking catalyst and operating at a temperature between 250 and 450°C, at a total pressure between 2 and 15 MPa, at a space velocity between 0.1 and 10 h, 1and at a hydrogen flow rate adjusted to obtain a ratio of between 100 and 2000 normal liters of hydrogen per liter of feed, said hydrocracking catalyst comprising at least one noble metal of Group VIII of the periodic table and a support comprising at least one acidic solid, said operating conditions of said step c) being adjusted so that the conversion by passing into products having boiling points greater than or equal to a temperature Tx into products having boiling points below that same temperature Tx is less than 0.5, preferably less than 0.4 and preferably less than 0.3 and preferably less than 0.2, Tx being between 250 and 350°C, preferably between 270 and 340°C and most preferably between 280 and 330°C, step d') the separation of the effluent from step c) into at least a hydrocracking hydrocarbon liquid fraction and a gaseous fraction,said separation steps b') and d') advantageously being carried out in the same separation unit or in separate separation units, step d) the fractionation in one or more steps of at least all or part of the hydrocracked hydrocarbon liquid fraction from step d'), into at least a gaseous fraction, a naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between, between 100 and 160°C, at least one kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C, and a residual heavy fraction having an initial boiling point above 250°C, said fractionation steps b) and d) advantageously being carried out in the same fractionation unit or in separate fractionation units, step e) the hydroisomerization of at least a portion of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C from fractionation step b) and of all or part of the kerosene fraction having an initial boiling point between 100 and 160°C and a final boiling point between 250 and 320°C resulting from the splitting step d) in the case where said splitting steps b) and d) are distinct,in the presence of a hydroisomerization catalyst operating at a temperature between 200 and 450°C, a total pressure between 1 and 15 MPa and a total pressure at least 0.3 MPa lower than the total pressure implemented in step a) of hydrotreating or step c) of hydrocracking, a spatial velocity between 0.1 and 10 h, 1, a hydrogen flow rate adjusted to obtain a ratio of between 100 and 2000 normal liters of hydrogen per liter of feed, to produce a hydroisomerized effluent, step f) recycle all or part of the residual heavy fraction having an initial boiling point above 250°C in hydrocracking step c, step g) optionally purging part of the hydrocracking effluent from hydrocracking step c, step h') separating the effluent from step e) into at least one hydroisomerized hydrocarbon liquid fraction and one gaseous fraction, step h) fractionating all or part of the hydroisomerized hydrocarbon liquid fraction from step h') into at least one gaseous fraction, one naphtha fraction having an initial boiling point between 30 and 60°C and a final boiling point between 120 and 160°C, and at least one fraction kerosene having an initial boiling point between 120 and 160°C,step i) the compression in a single compression section of the gaseous fraction from step h'), the gaseous effluent from step i) being recycled to step a) and / or c) and / or e) and at least part and preferably all of the gaseous fraction from step b') being sent to hydrocracking step c) and / or hydroisomerization step e) without passing through said compression step i) and / or at least part and preferably all of the gaseous fraction from d') being sent to hydroisomerization step e) without passing through said compression step i).

2. A method according to claim 1 in which said separation step b') is carried out in one or more separator balloons.

3. A method according to any one of claims 1 or 2 wherein step c) operates at a temperature between 280 and 450°C, and more preferably between 320 and 420°C, at a total pressure between 2.5 and 10 MPa, more preferably between 1 and 9 MPa, at a space velocity between 0.2 and 7 h-1, and more preferably between 0.5 and 5 h-1, and with a hydrogen flow rate adjusted to obtain a ratio between 150 and 1500 normal liters of hydrogen per liter of charge and more preferably between 300 and 1500 normal liters of hydrogen per liter of charge.

4. A method according to any one of the preceding claims wherein step c) operates at a total pressure lower than that of step a) by 0.2 to 0.5 MPa.

5. A process according to any one of claims 1 to 4, wherein said hydroisomerization catalyst used in step e) comprises at least one noble metal of Group VIII of the periodic table and a support comprising at least one binder and at least one zeolite selected from the structural-type zeolites TON, FER, EUO, AEL, *MRE, MTW, MOR, *BEA and ZEOLITH IZM-2, alone or in mixtures 6. A process according to claim 5 wherein the catalyst of step e) comprises and is preferably made of platinum, and a support comprising and preferably made of a ZSM-12 zeolite and an alumina binder.

7. A process according to claim 5 wherein the catalyst of step e) comprises and is preferably made of platinum, and a support comprising and preferably made of an IZM-2 zeolite and an alumina binder.

8. A process according to any one of claims 1 to 7 wherein said hydroisomerization step e) operates at a temperature between 250 and 450°C and preferably between 280 and 430°C, a total pressure between 1 and 10 MPa and preferably between 1 and 9 MPa, a space velocity between 0.2 and 7 h-1 and preferably between 0.5 and 5 h-1, a hydrogen flow rate adjusted to obtain a ratio between 150 and 2000 normal liters of hydrogen per liter of feed and preferably between 150 and 1500 normal liters of hydrogen per liter of feed.

9. A process according to any one of claims 1 to 8, wherein said step e) operates at a total pressure at least 0.8 MPa lower than the total pressure implemented in hydrotreating step a) or hydrocracking step c) and preferably 0.8 to 2 MPa lower and preferably 0.9 to 1.5 MPa lower than the total pressure implemented in hydrotreating step a) or hydrocracking step c) 10. A method according to any one of claims 1 to 9 in which said separation step d') is carried out in one or more separator balloons.

Images