EP2235139A2

EP2235139A2 - Method of producing middle distillates by hydroisomerization and hydrocracking of feedstocks coming from the fischer-tropsch process

Info

Publication number: EP2235139A2
Application number: EP08872965A
Authority: EP
Inventors: Emmanuelle Guillon; Christophe Bouchy; Johan Martens
Original assignee: IFP Energies Nouvelles IFPEN; Eni SpA
Current assignee: IFP Energies Nouvelles IFPEN; Eni SpA
Priority date: 2008-01-04
Filing date: 2008-12-16
Publication date: 2010-10-06
Also published as: WO2009106705A2; FR2926085B1; FR2926085A1; ZA201004890B; WO2009106705A3

Abstract

The invention relates to a method of producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, employing a hydroisomerization/hydrocracking catalyst comprising at least one hydro-dehydrogenating metal chosen from the group formed by the metals of group VIB and group VIII of the Periodic Table and a support comprising at least one silica-alumina and at least one zeolite chosen from the group formed by TON, FER and MTT structural zeolites and ZBM-30, ZSM-48 and COK-7 zeolites taken individually or as a mixture, said method operating at a temperature between 270 and 400°C, with a pressure of between 1 and 9 MPa, a space velocity of between 0.5 and 5 h-1 and a hydrogen flow rate adjusted so as to obtain a ratio of 400 to 1500 normal litres of hydrogen per litre of feedstock.

Description

PROCESS FOR THE PRODUCTION OF MEDIUM DISTILLATES BY HYDROISOMERIZATION AND HYDROCRACKING OF CHARGES FROM THE RSCHER-TROPSCH PROCESS

The present invention relates to a process for producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, using a hydrocracking / hydroisomerization catalyst comprising at least at least one hydro-dehydrogenating metal chosen from the group formed. by metals of group VIB and group VIII of the Periodic Table and a support comprising at least one silica-alumina and at least one zeolite selected from the group consisting of zeolites of structural type TON, FER, MTT, zeolites ZBM- 30, ZSM-48 and COK-7, taken alone or in a mixture, said process operating at a temperature of between 270 and 400 ^° C., a pressure of between 1 and 9 MPa, a space velocity of between 0.5 and 5 h. 1, a flow rate of hydrogen adjusted to obtain a ratio of 400 to 1500 normal liters of hydrogen per liter of charge.

Prior art

In the Fischer-Tropsch process, the synthesis gas (CO + H ₂ ) is catalytically converted into oxygenates and substantially linear hydrocarbons in gaseous, liquid or solid form. These products are generally free of heteroatomic impurities such as, for example, sulfur, nitrogen or metals. They also contain practically little or no aromatics, naphthenes and more generally cycles especially in the case of cobalt catalysts. On the other hand, they may have a significant content of oxygenated products which, expressed by weight of oxygen, is generally less than about 5% by weight and also an unsaturated content (olefinic products in general) generally less than 10% by weight. However, these products, mainly made of normal paraffins, can not be used as such, in particular because of their cold-holding properties that are not very compatible with the usual uses of petroleum fractions. For example, the pour point of a linear hydrocarbon containing 20 carbon atoms per molecule (boiling point equal to about 340 ° C., that is often included in the middle distillate cut) is + 37 ^° C. about which makes its use impossible, the specification being -15 ° C for diesel. The hydrocarbons resulting from the Fischer-Tropsch process comprising mainly n-paraffins must be converted into more valuable products such as, for example, gas oil, kerosene, which are obtained, for example, after catalytic reactions of hydroisomerization.

All catalysts currently used in hydroisomerization / hydrocracking are of the bifunctional type associating an acid function with a hydrogenating function. The acid function is provided by supports of large surfaces (150 to 800 m2.g-1 generally) having a superficial acidity, such as halogenated aluminas (chlorinated or fluorinated, in particular), phosphorus aluminas, combinations of boron and aluminum oxides, and silica-aluminas. The hydrogenating function is provided either by one or more metals of group VIII of the periodic table of the elements, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by a combination of at least one Group VI metal such as chromium, molybdenum and tungsten and at least one Group VIII metal.

The equilibrium between the two acid and hydrogenating functions is one of the parameters that govern the activity and the selectivity of the catalyst. A weak acidic function and a strong hydrogenating function give catalysts which are not very active and selective towards isomerization whereas a strong acid function and a low hydrogenating function give very active and cracking-selective catalysts. A third possibility is to use a strong acid function and a strong hydrogenating function to obtain a very active catalyst but also very selective towards isomerization. It is therefore possible, by judiciously choosing each of the functions to adjust the activity / selectivity couple of the catalyst.

Conventional catalysts for catalytic hydrocracking are for the most part constituted by weakly acidic supports, such as silica-aluminas, for example. These systems are more particularly used to produce middle distillates of very good quality. In low acid carriers, there is the family of silica-aluminas. Many of the hydrocracking market catalysts are based on Group VIII metal silica-alumina. These systems have a very good selectivity in middle distillates, and the products formed are of good quality (US6733657). The disadvantage of all these silica-alumina catalyst systems is, as mentioned, their low activity. .

On the other hand, catalytic systems based on zeolite (in particular zeolite USY or beta) are very active for the hydrocracking reaction but are not very selective.

By attempting to develop catalysts that are both active in hydrocracking and selective in middle distillates, the applicant has discovered that the use of specific hydrocracking catalysts based on silica-alumina and comprising at least one particular zeolite chosen from the group formed by the zeolites of structural type TON, FER, MTT, zeolites ZBM-30, ZSM-48, and COK-7, taken alone or as a mixture, gives improved catalytic performances in the hydrocracking and paraffin hydroisomerization processes. from a Fischer-Tropsch synthesis process, in particular an improved middle distillate yield with respect to silica-alumina catalysts.

OBJECT OF THE INVENTION The present invention thus relates to a process for the production of middle distillates. This process makes it possible to increase the amount of average distillates available by hydrocracking the heavier paraffinic compounds present in the outlet effluent of the Fischer-Tropsch unit, and which have boiling points higher than those of the kerosene cuts. and diesel, for example the fraction 370 ⁰ C ⁺ .

More specifically, the invention relates to a method for producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis using a particular catalyst as defined in the description which follows.

The present invention relates to a method for producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, using a hydrocracking / hydroisomerization catalyst comprising at least at least one hydro-dehydrogenating metal chosen from the group formed. by metals of group VIB and group VIII of the Periodic Table and a support comprising at least one silica-alumina and at least one zeolite selected from the group consisting of zeolites of structural type TON, FER, MTT, zeolites ZBM- 30, ZSM-48 and COK-7, taken alone or in a mixture, said process operating at a temperature of between 270 and 400 ^° C., a pressure of between 1 and 9 MPa, a space velocity of between 0.5 and 5 h. 1, a flow rate of hydrogen adjusted to obtain a ratio of 400 to 1500 normal liters of hydrogen per liter of charge.

The present invention makes it possible to improve the performance of the middle distillate production process by optimizing the operating conditions used in the process according to the invention. Thus, the selection of particular operating conditions and specific catalysts makes it possible to obtain high average distillate yields.

Detailed description of the invention

The present invention relates to a method for producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, using a hydrocracking / hydroisomerization catalyst comprising at least at least one hydro-dehydrogenating metal chosen from the group formed. by Group VIB and Group metals VIII of the Periodic Table and a support comprising at least one silica-alumina and at least one zeolite selected from the group consisting of zeolites of structural type TON, FER, MTT, zeolites ZBM-30, ZSM-48 and COK-7 , taken alone or as a mixture, said process operating at a temperature of between 270 and 400 ^° C. and preferably between 300 and 390 ^° C., a pressure of between 1 and 9 MPa and preferably between 2 and 8 MPa, a speed of between 0.5 and 5 h -1 and preferably between 0.8 and 3 h -1, a flow rate of hydrogen adjusted to obtain a ratio of 400 to 1500 normal liters of hydrogen per liter of feedstock and preferably a ratio of 600 and 1300 normal liters of hydrogen per liter of filler.

Preferably, said hydrocracking / hydroisomerization catalyst comprises,

0.1 to 60%, preferably 0.1 to 50% and even more preferably 0.1 to 40% of at least one hydro-dehydrogenating metal selected from the group consisting of Group VIB metals and Group VIII, and preferably from 40 to 99.9% of a support comprising: 0 to 99% and preferably 2 to 98%, preferably 5 to 95% of at least one amorphous porous inorganic binder or poorly crystallized oxide type (excluding silica-alumina)

0.1 to 40%, preferably 0.2 to 38%, preferably 0.5 to 35% and most preferably 1 to 30% of at least one zeolite selected from the group formed by the zeolites of structural type TON, FER, MTT, zeolites ZBM-30, ZSM-48 and COK-7, taken alone or as a mixture,

from 60 to 95% of silica -alumina, preferably from 70 to 95% and very preferably from 80 to 95%, the percentages being expressed as a percentage by weight relative to the total mass of the catalyst.

Advantageously, said catalyst also contains:

at least one doping element chosen from the group formed by phosphorus, boron and silicon. The boron, silicon and phosphorus mass contents are between 0.1 and 15%, preferably between 0.1 and 10%, and still more advantageously between 0.1 and 5% by weight relative to the total mass of the catalyst. . The term "doping element" means an element introduced after the preparation of the zeolite / silica-alumina / binder support.

According to the invention, the catalyst comprises at least one hydrodehydrogenating metal selected from the group consisting of Group VII metals and Group VIB metals, taken alone or in admixture. Preferably, the group VIII elements are chosen from iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium or platinum, taken alone or as a mixture.

In the case where the elements of group VIII are chosen from the noble metals of group VII, the elements of group VIII are advantageously chosen from platinum and palladium.

In the case where the elements of group VIlI are chosen from non-noble metals of group VIlI, the elements of group VIII are advantageously chosen from iron, cobalt and nickel. Preferably, the group VIB elements of the catalyst according to the present invention are selected from tungsten and molybdenum.

In the case where the hydrogenating function comprises a group VIII element and a group VIB element, the following metal combinations are preferred: nickel-molybdenum, cobalt-molybdenum, iron-molybdenum, iron-tungsten, nickel-tungsten, cobalt- tungsten, and very preferably: nickel-molybdenum, cobalt-molybdenum, nickel-tungsten. It is also possible to use combinations of three metals such as for example nickel-cobalt-molybdenum.

The content of the hydro-dehydrogenating element of said catalyst according to the present invention chosen from the group formed by the metals of group VIB and of group VIII is between 0.1 and 60% by weight relative to the total mass of said catalyst, preferably between 0 , 1 to 50% by weight and very preferably between 0.1 to 40% by weight. When the hydro-dehydrogenating element is a noble metal of group VIII, the catalyst preferably contains a noble metal content of between 0.05 and 10% by weight, even more preferably from 0.1 to 5% by weight relative to to the total mass of said catalyst.

Zeolites

According to the invention, the support of the catalyst according to the present invention comprises at least one zeolite chosen from the group formed by zeolites of structural type TON, FER, MTT, zeolites ZBM-30, ZSM-48 and COK-7, taken alone or as a mixture,

Preferably, said support comprises zeolite ZBM-30 or zeolite COK-7 and very preferably, said support comprises zeolite ZBM-30.

Zeolite ZBM-30 is described in patent EP-A-46 504, and zeolite COK-7 is described in patent applications EP 1 702 888 A1 or FR 2 882 744 A1. Preferably, the COK-7 zeolite used in the catalyst according to the present invention is synthesized in the presence of the organic triethylenetetramine structurant. In a preferred manner, the ZBM-30 zeolite used in the catalyst according to the present invention is synthesized in the presence of the organic triethylenetetramine structurant.

More preferably, the support of the catalyst according to the present invention comprises the COK-7 zeolite, synthesized in the presence of the organic triethylenetetramine structurant, in a mixture with zeolite ZBM-30 synthesized in the presence of the organic triethylenetetramine structurant.

Zeolites of TON structural type are described in "Atlas of Zeolite Structure Types", W. M. Meier, D.H. Oison and Ch. Baerlocher, 5th Revised Edition, 2001, Elsevier. The zeolite of structural type TON which can also be used in the composition of the support of the catalyst according to the present invention is advantageously chosen from the group formed by the zeolites Theta-1, ISI-1, NU-10, KZ-2 and ZSM-22 described. in the "Atlas of Zeolite Structure Types", cited above, and in the case of zeolite ZSM-22, in US Pat. Nos. 4,566,477 and 4,902,406, and in the case of zeolite NU-10, in EP-65400 and EP-77624.

The zeolite of structural type FER which can also enter the composition of the support of the catalyst according to the present invention is advantageously chosen from the group formed by zeolites ZSM-35, ferrierite, FU-9 and ISI-6, described in the book " Atlas of Zeolite Structure Types ", cited above. The MTT structural type zeolite which can also be used in the composition of the catalyst support according to the present invention is advantageously chosen from the group formed by zeolites ZSM-23, EU-13, ISI-4 and KZ-1 described in the book. "Atlas of Zeolite Structure Types", cited above, as well as in US Pat. No. 4,076,842 for zeolite ZSM-23. Among the zeolites of structural type TON which can also be used in the composition of the catalyst support according to the present invention, zeolites ZSM-22 and NU-10 are preferred.

Among the zeolites of FER structural type that can also be included in the composition of the catalyst support according to the present invention, zeolites ZSM-35 and ferrierite are preferred.

Among the zeolites of MTT structural type which can also be used in the composition of the support of the catalyst according to the present invention zeolite ZSM-23 is preferred. Preferably, the support of the catalyst according to the invention contains a mixture of two zeolites and, preferably, a mixture of the COK-7 zeolite with the zeolite ZSM-22 or the zeolite NU-10, or a mixture of the zeolite ZBM-30 with zeolite ZSM-22 or zeolite NlM 0. The proportion of each of the zeolites in the mixture of the two zeolites is advantageously between 20 and 80% by weight relative to the total weight of the mixture of the two zeolites, and preferably the proportion of each of the zeolites in the mixture of the two zeolites is 50% by weight relative to the total weight of the mixture of the two zeolites. The zeolites present in the support of the catalyst according to the invention advantageously comprise silicon and at least one element T chosen from the group formed by aluminum, iron, gallium, phosphorus and boron, and preferably said element T is aluminum

The overall Si / Al ratio of the zeolites used in the composition of the catalyst support according to the invention as well as the chemical composition of the samples are determined by X-ray fluorescence and atomic absorption.

The Si / Al ratios of the zeolites described above are advantageously those obtained in the synthesis according to the procedures described in the various documents cited or obtained after post-synthesis dealumination treatments well known to those skilled in the art. such as and not limited to hydrothermal treatments followed or not acid attacks or even direct acid attacks by solutions of mineral or organic acids.

The zeolites used in the composition of the support of the catalyst according to the invention are advantageously calcined and exchanged by at least one treatment with a solution of at least one ammonium salt so as to obtain the ammonium form of the zeolites which, once calcined, leads to to the hydrogen form of said zeolites.

The zeolites used in the composition of the support of the catalyst according to the invention are advantageously at least partly, preferably almost completely, in acid form, that is to say in acid form (H +). The atomic ratio Na / T is generally advantageously less than 0.1 and preferably less than 0.05 and even more preferably less than 0.01. Silica-alumina

According to the invention, the support of the catalyst according to the invention also comprises at least one silica-alumina.

Any silica-alumina known to those skilled in the art is suitable for the invention.

The silica-alumina contained in the catalyst according to the invention is a non-zeolitic support with a silica mass (SiO ₂ ) content greater than 5% by weight and less than or equal to 95% by weight,

According to a preferred embodiment, the silica-alumina is homogeneous on a micrometer scale and contains an amount greater than 5% by weight and less than or equal to 95% by weight of silica (SiO ₂ ), preferably between 10 and 80 % weight, preferably a silica content greater than 20% by weight and less than 80% by weight and even more preferably greater than 25% by weight and less than 75% by weight, the silica content is advantageously between 10 and 50 weight, said silica - alumina having the following characteristics:

a mean pore diameter, measured by mercury porosimetry, of between 20 and 140 Å,

a total pore volume, measured by mercury porosimetry, of between 0.1 ml / g and 0.5 ml / g, a total pore volume, measured by nitrogen porosimetry, of between 0.1 ml / g and 0, 5 ml / g,

a BET specific surface area of between 100 and 550 m ² / g,

a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 140 Λ less than 0.1 ml / g, a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 160; Less than 0.1 ml / g,

a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 200 Λ, less than 0.1 ml / g,

a porous volume, measured by mercury porosimetry, included in pores with diameters greater than 500 Λ less than 0.1 ml / g.

an X-ray diffraction diagram which contains at least the principal characteristic lines of at least one of the transition aluminas included in the group composed of alpha, rho, chi, eta, gamma, kappa, theta and delta aluminas.

Preferably, said silica-alumina contains: a content of cationic impurities (for example Na ⁺ ) of less than 0.1% by weight, preferably less than 0.05% by weight and even more preferably less than 0.025% by weight. The content of cationic impurities means the total content of alkali and alkaline earth.

- an anionic impurities content (e.g. SO ₄ ^{2- ",} ^Cl") of less than 1% by weight, preferably less than 0.5% by weight and even more preferably less than 0.1% weight.

Preparation processes

The catalysts used in the process according to the invention can advantageously be prepared according to all the methods well known to those skilled in the art, starting from the support based on silico-aluminum matrix and based on at least one selected zeolite. in the group formed by the zeolites of structural type TON, FER, MTT, zeolites ZBM-30, ZSM-48 and COK-7, taken alone or as a mixture.

a) Preparation of the silica-alumina

Any method of silica-alumina synthesis known to those skilled in the art leading to a homogeneous silica-alumina at the micrometer scale and in which the cationic impurities (for example Na ⁺ ) can advantageously be reduced to less than 0.1 %, preferably at a content of less than 0.05% by weight and even more preferably less than 0.025% by weight and in which the anionic impurities (for example SO ₄ ^{2 "} , CI ^" ) can advantageously be reduced to less than 1% and more preferably less than 0.05% by weight is suitable for preparing the supports that can be used in the process according to the invention.

The silicoaluminum matrices obtained from a mixture at any stage of a partially soluble acid alumina compound with a fully soluble silica compound or with a fully soluble combination of hydrated alumina and silica Shaping, followed by hydrothermal or thermal treatment to homogenize it at the micrometric scale, or even at the nanoscale, made it possible to obtain a particularly active catalyst. By partially soluble in acidic medium, the applicant understands that bringing the alumina compound into contact before any addition of the totally soluble silica compound or the combination with an acidic solution, for example of nitric acid or sulfuric acid, causes them to react. partial dissolution. Silica sources

The silica compounds used according to the invention may advantageously have been chosen from the group formed by silicic acid, silicic acid sols, water-soluble alkali silicates, cationic silicon salts, for example sodium metasilicate hydrate, Ludox® in ammoniacal form or in alkaline form, quaternary ammonium silicates. The silica sol can be prepared according to one of the methods known to those skilled in the art. Preferably, a solution of decationized orthosilicic acid is prepared from a water-soluble alkali silicate by ion exchange on a resin. Totally soluble silica-alumina sources

The totally soluble hydrous silica-aluminas advantageously used according to the invention can be prepared by true coprecipitation under controlled stationary operating conditions (pH, concentration, temperature, average residence time) by reaction of a basic solution containing the silicon, for example under sodium silicate form, optionally aluminum, for example in the form of sodium aluminate with an acid solution containing at least one aluminum salt, for example aluminum sulphate. At least one carbonate or CO ₂ may optionally be added to the reaction medium.

By true coprecipitation, the applicant intends a process by which at least one fully soluble aluminum compound in basic or acid medium as described below, at least one silicon compound as described below are contacted, simultaneously or sequentially in the presence of at least one precipitant and / or coprecipitant compound so as to obtain a mixed phase consisting essentially of silica-hydrated alumina which is optionally homogenized by intense stirring, shearing, colloid milling or by combination of these unit operations.

Sources of alumina

The alumina compounds advantageously used according to the invention are partially soluble in acid medium. They are selected in whole or in part from the group of alumina compounds of general formula AI ₂ O ₃ , nH ₂ O. In particular hydrated alumina compounds may be used such as: hydrargillite, gibbsite, bayerite , boehmite, pseudo-boehmite and amorphous or essentially amorphous alumina gels. It is also advantageous to use the dehydrated forms of these compounds which consist of transition aluminas and which comprise at least one of the phases taken from the group: rho, chi, eta, gamma, kappa, theta, and delta, which are essentially differentiated by the organization of their crystalline structure. The alpha alumina commonly called corundum can advantageously be incorporated in a small proportion in the support according to the invention.

Aluminum hydrate AI ₂ O ₃ , nH ₂ O used more preferably is advantageously boehmite, pseudo-boehmite and amorphous or essentially amorphous alumina gels. A mixture of these products under any combination may be used as well. Boehmite is generally described as an aluminum monohydrate of formula AI ₂ O ₃ , nH ₂ O which in fact encompasses a wide continuum of materials of variable degree of hydration and organization with more or less well defined boundaries: most hydrated gelatinous boehmite, with n being greater than 2, pseudo-boehmite or microcrystalline boehmite with n between 1 and 2, then crystalline boehmite and finally well crystallized boehmite in large crystals with n close to 1 The morphology of aluminum monohydrate can advantageously vary within wide limits between these two acicular or prismatic extreme forms. A whole set of variable shapes can be used between these two forms: chain, boats, interwoven plates. Relatively pure aluminum hydrates can advantageously be used in powder form, amorphous or crystallized or crystallized containing an amorphous part. The aluminum hydrate can also advantageously be introduced in the form of aqueous suspensions or dispersions. The aqueous suspensions or dispersions of aluminum hydrate used according to the invention may advantageously be gelable or coagulable. The aqueous dispersions or suspensions may also advantageously be obtained as is well known to those skilled in the art by peptization in water or acidulated water of aluminum hydrates.

The aluminum hydrate dispersion may advantageously be carried out by any method known to those skilled in the art: in a "batch" reactor, a continuous mixer, a kneader, a colloid mill. Such a mixture may advantageously also be carried out in a plug flow reactor and, in particular, in a static mixer. Lightnin reactors can be mentioned.

In addition, it is also advantageous to use as a source of alumina an alumina which has been previously subjected to a treatment that is susceptible to to improve its degree of dispersion. By way of example, it will be possible to improve the dispersion of the alumina source by a preliminary homogenization treatment. By homogenization, it is advantageous to use at least one of the homogenization treatments described in the text that follows. The aqueous dispersions or suspensions of alumina which may be used include aqueous suspensions or dispersions of fine or ultra-fine boehmites which are composed of particles advantageously having dimensions in the colloidal domain.

The fine or ultra-fine boehmites advantageously used according to the present invention may in particular have been obtained according to the French patent FR-B-

1 261 182 and FR-B-1 381 282 or in the European patent application EP-A-15 196.

It is also advantageous to use aqueous suspensions or dispersions obtained from pseudo-boehmite, amorphous alumina gels, aluminum hydroxide gels or ultra-fine hydrargillite. Aluminum monohydrate can advantageously be purchased from a variety of commercial sources of alumina such as in particular PURAL®, CATAPAL®, DISPERAL®, DISPAL® sold by the company SASOL or HIQ® marketed by ALCOA, or according to the methods Known to those skilled in the art: it can advantageously be prepared by partial dehydration of aluminum trihydrate by conventional methods or it can advantageously be prepared by precipitation. When these aluminas are in the form of a gel, they are advantageously peptized with water or an acidulated solution. In precipitation, the acid source may advantageously be for example chosen from at least one of the following compounds: aluminum chloride, aluminum sulphate, aluminum nitrate. The basic aluminum source may be selected from basic aluminum salts such as sodium aluminate and potassium aluminate.

b) Preparation of the zeolite

The zeolites used in the catalyst according to the invention are advantageously commercial zeolites or zeolites synthesized according to the procedures described in the patents mentioned above. The zeolites used in the composition of the catalyst according to the invention are advantageously at least partly, preferably almost completely, in acid form, that is to say in hydrogen (H ⁺ ) form. c) Preparation of the zeolite-silica-alumina matrix

The matrix according to the invention may advantageously be prepared according to all methods well known to those skilled in the art from the supports prepared as described above.

The zeolite can advantageously be introduced according to any method known to those skilled in the art and at any stage of the preparation of the support or catalyst.

A preferred process for preparing the catalyst according to the present invention advantageously comprises the following steps:

According to a preferred method of preparation, the zeolite may advantageously be introduced during the synthesis of the precursors of the silica-alumina. The zeolite may be, without limitation, for example in the form of powder, ground powder, suspension, suspension having undergone deagglomeration treatment. Thus, for example, the zeolite can advantageously be slurried acidulated or not at a concentration adjusted to the final zeolite content referred to the support. This suspension, commonly known as a slurry, is then mixed with the precursors of the silica-alumina at any stage of its synthesis as described above.

According to another preferred method of preparation, the zeolite can advantageously also be introduced during the shaping of the support with the elements which constitute the matrix with possibly at least one binder. The zeolite may advantageously be, without being limited to, in the form of a powder, ground powder, suspension or suspension having undergone deagglomeration treatment.

The preparation and treatment (s) and the shaping of the zeolite can thus advantageously constitute a step in the preparation of these catalysts. Advantageously, the zeolite / silica-alumina matrix is obtained by mixing the silica-alumina and the zeolite, and the mixture is then shaped.

Formatting supports and catalysts

The zeolite / silica-alumina matrix may advantageously be shaped by any technique known to those skilled in the art. The shaping can advantageously be carried out for example by extrusion, by pelletization, by the method of drop coagulation ("oil-drop"), by rotating plate granulation or by any other method well known to those skilled in the art. . The shaping can advantageously also be carried out in the presence of the various constituents of the catalyst and extrusion of the obtained mineral paste, by pelletizing, shaped into beads at the rotating bezel or drum, drop coagulation, "oil-drop" , "oil-up", or any other known method of agglomeration of a powder containing alumina and optionally other ingredients selected from those mentioned above.

The catalysts used in the process according to the invention are in the form of spheres or extrudates. It is however advantageous that the catalyst is in the form of extrudates with a diameter of between 0.5 and 5 mm and more particularly between 0.7 and 2.5 mm. The shapes are cylindrical (which can be hollow or not), cylindrical twisted, multilobed (2, 3, 4 or 5 lobes for example), rings. The cylindrical shape is preferably used in a preferred manner, but any other form may advantageously be used. Furthermore, these supports implemented according to the present invention may advantageously have been treated as is well known to those skilled in the art by additives to facilitate the shaping and / or improve the final mechanical properties of the supports to base of silico-aluminum matrices. By way of example of additives, there may be mentioned in particular cellulose, carboxymethylcellulose, carboxy-ethylcellulose, tall oil, xanthan gums, surfactants, flocculating agents such as polyacrylamides, carbon black, starches, stearic acid, polyacrylic alcohol, polyvinyl alcohol, biopolymers, glucose, polyethylene glycols, etc.

The shaping may advantageously be carried out using the catalyst shaping techniques known to those skilled in the art, such as, for example: extrusion, coating, spray drying or tabletting. Water may be advantageously added or removed to adjust the viscosity of the paste to be extruded. This step can be performed at any stage of the kneading step.

In order to adjust the solid content of the paste to be extruded to make it extrudable, it is also advantageous to add a predominantly solid compound and preferably an oxide or a hydrate. A hydrate is preferably used and even more preferably an aluminum hydrate. The loss on ignition of this hydrate is advantageously greater than 15%.

The acid content added to the kneading before shaping is less than 30%, preferably between 0.5 and 20% by weight of the anhydrous mass of silica and alumina involved in the synthesis. Extrusion can advantageously be performed by any conventional tool, commercially available. The paste resulting from the mixing is advantageously extruded through a die, for example by means of a piston or a single screw or twin extrusion screw. This extrusion step may advantageously be carried out by any method known to those skilled in the art.

The support extrusions according to the invention advantageously have generally a crush strength of at least 70 N / cm and preferably greater than or equal to 100 N / cm.

Calcination of zeolite / silica-alumina support

Drying is advantageously carried out by any technique known to those skilled in the art.

To obtain the support of the present invention, it is preferable to calcine preferably in the presence of molecular oxygen, for example by conducting a sweep of air, at a temperature of less than or equal to 1100 ^° C. At least one calcination can advantageously be performed after any of the steps of the preparation. This treatment, for example, can be carried out in crossed bed, in a licked bed or in a static atmosphere. For example, the furnace used may advantageously be a rotating rotary kiln or be a vertical kiln with radial traversed layers. The calcination conditions: temperature and time depend mainly on the maximum temperature of use of the catalyst. The preferred calcining conditions are advantageously between more than one hour at 200 ^° C. and less than one hour at 1100 ^° C. The calcination can advantageously be carried out in the presence of water vapor. The final calcination may optionally be carried out in the presence of an acidic or basic vapor. For example, the calcination can advantageously be carried out under partial pressure of ammonia.

Post-Synthesis Treatments Post-synthesis treatments can be advantageously carried out so as to improve the properties of the catalyst.

According to the invention, the zeolite / silica-alumina support can thus be optionally subjected to a hydrothermal treatment in a confined atmosphere. By hydrothermal treatment in a confined atmosphere is meant a treatment by autoclaving in the presence of water at a temperature above room temperature. During this hydrothermal treatment, the support can advantageously be treated. Thus, the support can advantageously be impregnated, prior to its autoclaving, the autoclaving being done either in the vapor phase or in the liquid phase, this vapor or liquid phase of the autoclave possibly being acidic or not. This impregnation, prior to autoclaving, may advantageously be acidic or not. This impregnation, prior to autoclaving may advantageously be carried out dry or by immersion of the support in an acidic aqueous solution. Dry impregnation means contacting the support with a solution volume less than or equal to the total pore volume of the support. Preferably, the impregnation is carried out dry. The autoclave is preferably a rotary basket autoclave such as that defined in patent application EP-A-0 387 109.

The temperature during autoclaving can be between 100 and 250 ⁰ C for a period of time between 30 minutes and 3 hours.

d) Deposit of metals

The hydro-dehydrogenating element may advantageously be introduced at any stage of the preparation, very preferably after forming the zeolite / silica-alumina support. The shaping is advantageously followed by calcination, the hydrogenating element can also advantageously be introduced before or after this calcination. The preparation generally ends with a calcination at a temperature of 250 to 600 ^° C. Another of the preferred methods according to the present invention advantageously consists in shaping the zeolite / silica-alumina support after mixing the latter, then the dough thus obtained through a die to form extrudates with a diameter of between 0.4 and 4 mm. The hydrogenating function can advantageously be then introduced in part only or in full, at the time of mixing. It can also advantageously be introduced by one or more ion exchange operations on the calcined support constituted by at least one silica-alumina, at least one zeolite chosen from the group formed by the zeolites of structural type TON, FER, MTT, Zeolites ZBM-30, ZSM-48 and COK-7, taken alone or as a mixture, and optionally shaped with a binder, using solutions containing the precursor salts of the chosen metals.

In a preferred manner, the support is impregnated with an aqueous solution. The impregnation of the support is preferably carried out by the so-called impregnation method. The impregnation may advantageously be carried out in a single step by a solution containing all the constitutive elements of the final catalyst.

The hydrogenating function may advantageously be introduced by one or more impregnation operations of the shaped and calcined support, with a solution containing at least one precursor of at least one oxide of at least one metal chosen from the group formed by the Group VIII metals and Group VIB metals, the precursor (s) of at least one oxide of at least one Group VIII metal being preferably introduced after those of group VIB or at the same time the latter, if the catalyst contains at least one Group VIB metal and at least one Group VIII metal.

In the case where the catalyst advantageously contains at least one element of group VIB, for example molybdenum, it is for example possible to impregnate the catalyst with a solution containing at least one element of group VIB, to dry, to calcine. The impregnation of molybdenum may advantageously be facilitated by the addition of phosphoric acid in the ammonium paramolybdate solutions, which also makes it possible to introduce the phosphorus so as to promote the catalytic activity.

The following elements: boron and / or silicon and / or phosphorus can be introduced into the catalyst at any level of the preparation and according to any technique known to those skilled in the art.

A preferred method according to the invention consists in depositing the selected promoter element or elements, for example the boron-silicon pair, on the calcined or non calcined zeolite / silica-alumina support, preferably calcined. For this purpose, an aqueous solution of at least one boron salt, such as ammonium biborate or ammonium pentaborate, is prepared in an alkaline medium and in the presence of hydrogen peroxide, and a so-called dry impregnation is carried out in which the pore volume of the precursor is filled with the solution containing, for example, boron. In the case where, for example, silicon is also deposited, for example a solution of a silicon-type silicon compound or a silicone oil emulsion is used.

The element (s) promoters) chosen (s) in the group formed by silicon, boron and phosphorus can advantageously be introduced by one or more impregnation operations with excess solution on the calcined precursor. The boron source may advantageously be boric acid, preferably orthoboric acid H3BO3, ammonium biborate or pentaborate, boron oxide, boric esters. Boron may for example be introduced in the form of a mixture of boric acid, hydrogen peroxide and a basic organic compound containing nitrogen such as ammonia, primary and secondary amines, cyclic amines, compounds of the family of pyridine and quinolines and compounds of the pyrrole family. Boron may be introduced for example by a boric acid solution in a water / alcohol mixture.

The preferred phosphorus source is orthophosphoric acid H 3 PO 4, but its salts and esters such as ammonium phosphates are also suitable. The phosphorus may for example be introduced in the form of a mixture of phosphoric acid and a basic organic compound containing nitrogen such as ammonia, primary and secondary amines, cyclic amines, compounds of the family of pyridine and quinolines and compounds of the pyrrole family.

Many sources of silicon can advantageously be employed. Thus, it is possible to use ethyl orthosilicate Si (OEt) 4, siloxanes, polysiloxanes, silicones, silicone emulsions, halide silicates, such as ammonium fluorosilicate (NH4) 2SiF6 or fluorosilicate. sodium Na2SiF6. Silicomolybdic acid and its salts, silicotungstic acid and its salts can also be advantageously employed. Silicon may advantageously be added for example by impregnation of ethyl silicate in solution in a water / alcohol mixture. Silicon can be added, for example, by impregnating a silicon-type silicon compound or silicic acid suspended in water.

The noble group VIII metals of the catalyst of the present invention may advantageously be present in whole or in part in metallic and / or oxide form.

The noble element sources of group VIII which can advantageously be used are well known to those skilled in the art. For the noble metals halides are used, for example chlorides, nitrates, acids such as chloroplatinic acid, hydroxides, oxychlorides such as ruthenium ammoniacal oxychloride. It is also advantageous to use cationic complexes such as ammonium salts when it is desired to deposit the platinum on the zeolite by cation exchange.

Embodiment 1 According to a preferred embodiment of the invention, the process comprises the following steps from a feed resulting from FT synthesis: a) separation of a single so-called heavy fraction with an initial boiling point of between 120-200 ⁰ C ₁ b) hydrotreatment of at least a part of said heavy fraction, c) fractionation into at least 3 fractions:

- at least one intermediate fraction having an initial boiling point T1 comprised between 120 and 200 ⁰ C and a final boiling point T2 greater than 300 ⁰ C and less than 410 ⁰ C ₁ - at least one light fraction boiling below the intermediate fraction,

at least one heavy fraction boiling above the intermediate fraction. d) passing at least part of said intermediate fraction over a hydroisomerizing catalyst, e) passing at least a portion of said heavy fraction in the process according to the invention f) distillation of the hydrocracked / hydroisomerized fractions to obtain distillates means, and recycling the residual fraction boiling above said middle distillates in step (e) on the catalyst according to the invention treating the heavy fraction.

The description of this embodiment will be made with reference to Figure 1 without Figure 1 limiting the interpretation.

Step (a)

The effluent from the Fischer-Tropsch synthesis unit arriving via line 1 is fractionated (for example by distillation) in a separation means (2) into at least two fractions: at least a light fraction and a heavy fraction at least initial boiling point equal to a temperature between 120 and 200 ° C and preferably between 130 and 180 ^° C and even more preferably at a temperature of about 15O ⁰ C, in other words the cutting point is located between 120 and 200 ⁰ C. The light fraction of Figure 1 out through the pipe (3) and the heavy fraction through the pipe (4). This fractionation can be carried out by methods well known to those skilled in the art such as flash, distillation, etc. As a non-limiting example, the effluent from the Fischer-Tropsch synthesis unit will be flashed. , decantation to remove water and distillation to obtain at least the 2 fractions described above.

The light fraction is not treated according to the process of the invention but may for example constitute a good load for petrochemicals and more particularly for a steam cracking unit (5). The heavy fraction previously described is treated according to the process of the invention.

Step (b)

At least a portion of said heavy fraction (step a) is allowed in the presence of hydrogen (line 6) in a zone (7) containing a hydrotreatment catalyst which aims to reduce the content of olefinic and unsaturated compounds and that possibly to decompose the oxygenated compounds present in the fraction, as well as possibly to break down any traces of sulfur and nitrogen compounds present in the heavy fraction. This hydrotreating step is non-converting, i.e. the conversion of the fraction 370 ⁰ C. ⁺ fraction 370 ° C ^"is preferably less than 20% by weight, preferably less than 10% by weight and very preferably less than 5% by weight.

The catalysts used in this step (b) are hydrotreating catalysts that are non-crunchy or slightly cracking and comprise at least one metal of group VIII and / or group VI of the periodic table of elements. Preferably, the catalyst comprises at least one metal of the metal group formed by nickel, molybdenum, tungsten, cobalt, ruthenium, indium, palladium and platinum and comprising at least one support.

It is possible to use a combination of at least one Group VI metal (especially molybdenum or tungsten) and at least one Group VIIl metal (especially cobalt and nickel) of the periodic table of elements. The metal concentration of the non-noble group VIII, when it is used, is from 0.01 to 15% by weight of equivalent with respect to the finished catalyst and that of the metal of the group VI (in particular molybdenum or tungsten) is 5% to 30% 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 sulfurous form. Advantageously, at least one element selected from P, B, Si is deposited on the support. This catalyst may advantageously contain phosphorus; indeed, this compound provides two advantages to hydrotreatment catalysts: an ease of preparation, particularly in the impregnation of nickel and molybdenum solutions, and a better hydrogenation activity.

In a preferred catalyst, the total concentration of metals of VI group and VIII ₁ expressed as the metal oxides, is between 5 and 40% by weight and preferably between 7 and 30% by weight and the weight expressed as metal oxide to (or metals) of group VI on metal (or metals) of group VIII is between 1, 25 and 20 and preferably between 2 and 10. Advantageously, if there is phosphorus, the concentration of phosphorus oxide P ₂ O ₅ is less than 15% by weight and preferably less than 10% by weight.

It is also possible to use a catalyst containing boron and phosphorus. Advantageously, boron and phosphorus are promoter elements deposited on the support, and for example the catalyst according to patent EP297949. The sum of the amounts of boron and phosphorus, expressed respectively by weight of boron trioxide and phosphorus pentoxide, relative to the weight of support, is about 5 to 15% and the atomic ratio boron on phosphorus is about 1 1 to 2: 1 and at least 40% of the total pore volume of the finished catalyst is contained in pores with an average diameter greater than 13 nanometers. Preferably, the amount of Group VI metal such as molybdenum or tungsten, is such that the atomic phosphorus to metal ratio of Group VIB is about 0.5: 1 to 1.5: 1; the quantities of metal and Group VIB metal of group VIII ₁ such as nickel or cobalt, are such that the atomic ratio of the group VIII metal of group VIB is about 0.3: 1 to 0.7: 1. The amounts of Group VIB metal expressed in weight of metal relative to the weight of finished catalyst is about 2 to 30% and the amount of Group VIII metal expressed as weight of metal relative to the weight of finished catalyst is about 0.01 to 15%.

Another particularly advantageous catalyst contains promoter silicon deposited on the support. An interesting catalyst contains BSi or PSi.

Ni-sulfide catalysts on alumina, NiMo on alumina, NiMo on alumina doped with boron and phosphorus and NiMo on silica-alumina are also preferred. Advantageously, eta or gamma alumina will be chosen as support. In the case of the use of noble metals (platinum and / or palladium) preferably, the metal content is between 0.05 and 3% by weight relative to the finished catalyst and preferably between 0.1 and 2% by weight of the finished catalyst. The noble metal is preferably used in its reduced and non-sulphurized form. It is also possible to use a reduced, non-sulfurized nickel catalyst. In this case the metal content in its oxide form is between 0.5 and 25% by weight relative to the finished catalyst. Preferably, the catalyst also contains a group IB metal such as copper, in proportions such that the mass ratio of the group IB metal and nickel on the catalyst is between 1 and 1:30.

These metals are deposited on a support which is preferably an alumina, but which may also be boron oxide, magnesia, zirconia, titanium oxide, a clay or a combination of these oxides. These catalysts can be prepared by any method known to those skilled in the art or can be acquired from companies specializing in the manufacture and sale of catalysts.

In the hydrotreatment reactor (7), the feedstock is brought into contact in the presence of hydrogen and the catalyst at operating temperatures and pressures which make it possible to hydrogenate the olefins present in the feedstock. Preferably, the catalyst and the operating conditions chosen will also make it possible to carry out the hydrodeoxygenation, that is to say the decomposition of the oxygenated compounds (mainly alcohols) and / or the hydrodesulphurisation or hydrodéazotation of the possible traces of sulfur compounds and / or or nitrogen present in the charge. The reaction temperatures used in the hydrotreating reactor are between 100 and 400 ^° C., preferably between 150 and 35 ^° C., more preferably between 150 and 300 ^° C. The total pressure range used varies from 5 to 150 bar, preferably between 10 and 100 bar and even more preferably between 10 and 90 bar. The hydrogen which feeds the hydrotreatment reactor is introduced at a rate such that the volume ratio hydrogen / hydrocarbons is between 50 to 3000 normal liters per liter, preferably between 100 and 2000 normal liters per liter and even more preferably between 150 and 1500 normal liters per liter. The charge rate is such that the hourly volume velocity is between 0.1 and 10 h ^-1 , preferably between 0.2 and 5 h ^-1 and even more preferably between 0.2 and 3 h ^-1 . Under these conditions, the content of unsaturated and oxygenated molecules is reduced to less than 0.5% by weight and to less than 0.1% by weight in general.The hydrotreating step is conducted under conditions such that the conversion to products having boiling points greater than or equal to 370 ^° C. in products having boiling points below 370 ^° C. is limited to 20% by weight, of Preferably, it is less than 10% by weight and even more preferably less than 5% by weight.

Step (c)

The effluent from the hydrotreatment reactor is fed via a pipe (8) into a fractionation zone (9) where it is fractionated into at least three fractions:

- at least one light fraction (leaving via line 10), the constituent compounds have boiling points below a temperature T1 between 120 and 200 ⁰ C, preferably between 130 and 180 ^c C, and still more preferred at a temperature of about 150 ^° C. In other words the cutting point is between 120 and 200 ^° C.

at least one intermediate fraction (line 11) comprising the compounds whose boiling points are between the cutting point T1, previously defined, and a temperature T2 greater than 300 ^° C., still more preferably greater than 35 ^° C. C and less than 410 ⁰ C or better at 370 ° C.

at least one so-called heavy fraction (line 12) comprising the compounds having boiling points higher than the previously defined cutting point T2.

Step (d)

At least a portion of said intermediate fraction is then introduced (line 11), as well as possibly a stream of hydrogen (line 13) into the zone (14) containing a hydroisomerization catalyst.

The operating conditions in which this step (d) is carried out are:

The pressure is maintained between 2 and 150 bar and preferably between 5 and 100 bar and preferably from 10 to 90 bar, the space velocity is between 0.1 hr ^"1 to 10 ^{h" 1,} and preferably between 0.2 and 7 h ^-1 is advantageously between 0.5 and 5.0 h ^-1 . The hydrogen flow rate is adjusted to obtain a ratio of 100 to 2000 normal liters of hydrogen per liter of feedstock and preferably between 150 and 1500 liters of hydrogen per liter of feedstock. The temperature used in this step is between 200 and 450 ^° C. and preferably from 250 ^° C. to 450 ^° C., advantageously from 300 to 45 ^° C., and even more advantageously above 320 ° C. or for example between 320 and 420 ^° C. 5

The hydroisomerization step (d) is advantageously carried out under conditions such that the pass conversion into products with boiling points greater than or equal to 150 ^° C. into products having boiling points below 150 ^° C. the lowest possible, preferably less than 50%, more preferably less than 30%, and most preferably less than 15% by weight, and allows to obtain middle distillates (gas oil and kerosene) having cold properties (pour point and freezing point) sufficiently good to meet the specifications in force for this type of fuel. Thus, in this step (d), it is sought to promote hydroisomerization rather than hydrocracking. The catalysts used are of the bifunctional type, that is to say that they have a hydro / dehydrogenating function and a hydroisomerizing function. The hydro / dehydrogenating function is generally provided either by noble metals (Pt and / or Pd) active in their reduced form or by non-noble metals of group VI (especially molybdenum and tugnstene) in combination with non-noble metals Group VIII (particularly nickel and cobalt), preferably used in their sulfurized form. The hydroisomerizing function is provided by acidic solids, such as zeolites, halogenated alumina, agile with a pillar, heteropolyacids or sulphated zirconia. An alumina binder may also be used during the catalyst shaping step.

The metal function can be introduced onto the catalyst by any method known to those skilled in the art, such as, for example, comalaxing, dry impregnation, exchange impregnation.

In the case where the hydroisomerization catalyst comprises at least one noble metal of group VIII _1, the noble metal content of the first hydroisomerization catalyst used in step b) of the process according to the invention is advantageously between 0.degree. , 01 and 5% by weight relative to the finished catalyst, preferably between 0.1 and 4% by weight and very preferably between 0.2 and 2% by weight.

In the case where the hydroisomerization catalyst comprises at least one group VI metal

In combination with at least one non-noble group VIlI metal, the group VI metal content of the hydroisomerization catalyst is advantageously included, in equivalent oxide, between 5 and 40% by weight relative to the finished catalyst, preferably between 10 and 35% by weight and very preferably between 15 and 30% by weight and the group VIII metal content of said catalyst is advantageously included , in oxide equivalent, between 0.5 and 10% by weight relative to the finished catalyst, preferably between 1 and 8% by weight and very preferably between 1, 5 and 6% by weight.

The hydro / dehydrogenating metal function can advantageously be introduced on said catalyst by any method known to those skilled in the art, such as, for example, comalaxing, dry impregnation, exchange impregnation.

According to step d) of hydroisomerization of the process according to the invention, the hydroisomerisation catalyst comprises at least one molecular sieve, preferably at least one zeolite molecular sieve and more preferably at least one zeolite molecular sieve. One-dimensional MR as a hydroisomerizing function.

The zeolite molecular sieves are defined in the "Atlas of Zeolite Structure Types" classification, W. M Meier, DH Oison and Ch. Baerlocher, 5th revised edition, 2001, Elsevier also referred to herein. Zeolites are classified according to the size of their pore openings or channels. One-dimensional 10 MR zeolite molecular sieves have pores or channels whose opening is defined by a ring of 10 oxygen atoms (10MR aperture). The zeolite molecular sieve channels having a 10 MR aperture are advantageously unidirectional one-dimensional channels that open directly to the outside of said zeolite. The one-dimensional 10 MR zeolite molecular sieves present in said hydroisomerization catalyst advantageously comprise silicon and at least one element T selected from the group formed by aluminum, iron, gallium, phosphorus and boron, preferably aluminum. The Si / Al ratios of the zeolites described above are advantageously those obtained in the synthesis or else obtained after post-synthesis dealumination treatments well known to those skilled in the art, such as and not limited to hydrothermal treatments. followed or not by acid attacks or even direct acid attacks by solutions of mineral or organic acids. They are preferably substantially completely in acid form, that is to say that the atomic ratio between the monovalent compensation cation (for example sodium) and the element T inserted in the network. The crystalline solid is preferably less than 0.1, preferably less than 0.05, and most preferably less than 0.01. Thus, the zeolites used in the composition of said selective hydroisomerization catalyst are advantageously calcined and exchanged by at least one treatment with a solution of at least one ammonium salt so as to obtain the ammonium form of the zeolites which, once calcined, lead to to the acid form of said zeolites.

The said one-dimensional 10MR zeolite molecular sieve of said hydroisomerization catalyst is advantageously chosen from zeolite molecular sieves of structure type TON (chosen from ZSM-22 and NU-10, taken alone or as a mixture), FER (chosen from ZSM-2). And ferrierite, alone or in admixture), EUO (selected from EU-1 and ZSM-50, alone or in admixture), SAPO-11 or zeolitic molecular sieves ZBM-30 or ZSM 48, taken alone or in mixture. Preferably, said one-dimensional 10MR zeolite molecular sieve is chosen from zeolitic molecular sieves ZBM-30, NU-10 and ZSM-22, taken alone or as a mixture. Very preferably, said one-dimensional 10MR zeolite molecular sieve is ZBM-30 synthesized with the organic template triethylenetetramine. Indeed, the use of said ZBM 30 produces much better results in terms of yield and activity than the other zeolites and in particular that the ZSM 48.

The one-dimensional 10MR zeolite molecular sieve content is advantageously between 5 and 95% by weight, preferably between 10 and 90% by weight, more preferably between 15 and 85% by weight and very preferably between 20 and 80% by weight relative to to the finished catalyst. The catalysts obtained are shaped in the form of grains of different shapes and sizes. They are generally used in the form of cylindrical or multi-lobed extrusions such as bilobed, trilobed, straight-lobed or twisted, but may optionally be manufactured and used in the form of crushed powders, tablets, rings, beads. , wheels. The shaping can be carried out with other matrices than alumina, such as, for example, magnesia, amorphous silica-aluminas, natural clays (kaolin, bentonite, sepiolite, attapulgite), silica, titanium, boron oxide, zirconia, aluminum phosphates, titanium phosphates, zirconium phosphates, coal and mixtures thereof. It is preferred to use matrices containing alumina, in all its forms known to those skilled in the art, and even more preferably aluminas, for example alumina. gamma. Other techniques than extrusion, such as pelletizing or coating, can be used.

Before use in the reaction, the metal contained in the catalyst must be reduced. One of the preferred methods for conducting the reduction of the metal is the treatment in hydrogen at a temperature of between 150 ^° C. and 650 ^° C. and a total pressure of between 1 and 250 bar. For example, a reduction consists of a stage at 150 ^° C. for two hours and then a rise in temperature up to 450 ^° C. at a rate of 1 ° C./min and then a two-hour stage at 45 ^° C.; throughout this reduction step, the hydrogen flow rate is 1000 normal liters of hydrogen / liter catalyst and the total pressure kept constant at 1 bar. Note also that any ex-situ reduction method is suitable.

Step

At least part of said heavy fraction is introduced via line (12) into a zone (15) where it is placed in the presence of hydrogen (25) in contact with a catalyst used in the process according to the present invention and under the operating conditions of the process of the present invention to produce a middle distillate cut (kerosene + gas oil) having good cold properties.

The catalyst used in the zone (15) of step (e) to carry out the hydrocracking and hydroisomerization reactions of the heavy fraction, defined according to the invention, is of the same type as that present in the reactor (14). ), i.e. a bifunctional catalyst as defined above in the first part of the patent application. It should be noted that the catalysts used in the reactors (14) and (15) may be strictly identical or different (for example, by varying the proportion of the zeolite in the catalyst, the nature of the binder or the quantity and nature of the hydrogenating phase).

During this step (e) the fraction 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 allow to improve the quality of the formed products and more particularly the cold properties of kerosene and diesel, and also to obtain very good distillate yields. Conversion to products with boiling points greater than or equal to 370 ° C in products with boiling points below 370 ⁰ C is greater than 80% by weight, often at least 85% and preferably greater than or equal to 88%.

Step ffî

The effluents leaving the reactors (14) and (15) are sent via the lines (16) and (17) to a distillation train, which incorporates an atmospheric distillation and optionally a vacuum distillation, and which is intended to separate on the one hand the light products inevitably formed during steps (d) and (e) for example gases (C ₁ -C ₄ ) (line 18) and a gasoline section (line 19), and distilling at least one section diesel (line 21) and kerosene (line 20). The gas oil and kerosene fractions can be recycled (line 23) partly, jointly or separately, at the top of the hydroisomerization / hydrocracking reactor (14) step (d).

It is also distilled a fraction (line 22) boiling over the diesel fuel, that is to say whose compounds which constitute it have boiling points higher than those of middle distillates (kerosene + diesel). This fraction, called the residual fraction, generally has an initial boiling point of at least 350 ^° C., preferably greater than 370 ° C. This fraction is advantageously recycled to the top of the reactor (15) via the hydroisomerization / hydrocracking line (22) of the heavy fraction (step e).

It may also be advantageous to recycle a portion of the kerosene and / or diesel in step (d), step (e) or both. Preferably, at least one of the kerosene and / or diesel fractions is partially recycled in step (d) (zone 14). It has been found that it is advantageous to recycle a portion of the kerosene to improve its cold properties.

Advantageously and at the same time, the non-hydrocracked fraction is partially recycled in step (e) (zone 15).

It goes without saying that the diesel and kerosene cuts are preferably recovered separately, but the cutting points are adjusted by the operator according to his needs.

In Figure 1, there is shown a distillation column (24), but two columns can be used to separately treat the sections from areas (14) and (15). In Figure 1, there is shown only the recycling of kerosene on the reactor catalyst (14). It goes without saying that one can also recycle a portion of the gas oil (separately or with kerosene) and preferably on the same catalyst as kerosene.

Embodiment 2

Another embodiment of the invention comprises the following steps: a) separation of at least a light fraction of the feedstock so as to obtain a single so-called heavy fraction with an initial boiling point of between 120-200 ^° C., b) optional hydrotreatment of said heavy fraction, optionally followed by a step c) removal of at least a portion of the water and optionally CO, CO ₂ , NH ₃ , H ₂ S, d) passing through the process according to the invention of at least a part of said optionally hydrotreated fraction, the conversion on the catalyst according to the invention above describes products with boiling points greater than or equal to 370 ⁰ C in products with boiling points less than 37O ⁰ C is greater than 40% by weight, e) distillation of the hydrocracked / hydroisomerized fraction to obtain middle distillates, and recycling in step d) of the residual fraction boiling above said middle distillates. The description of this embodiment will be made with reference to Figure 2 without Figure 2 limiting the interpretation.

Step (a)

The effluent from the Fischer-Tropsch synthesis unit arriving via line 1 is fractionated (for example by distillation) in a separation means (2) into at least two fractions: at least a light fraction and a heavy fraction at least initial boiling point equal to a temperature between 120 and 200 ⁰ C and preferably between 130 and 18O ⁰ C and even more preferably at a temperature of about 15O ⁰ C, in other words the point of cut is located between 120 and 200 ⁰ C. The light fraction of Figure 1 out through the pipe (3) and the heavy fraction through the pipe (4). This fractionation can be carried out by methods well known to those skilled in the art such as flash, distillation etc. As a non-limiting example, the effluent from the Fischer-Tropsch synthesis unit will be subject to flash, decantation to remove water and distillation to obtain at least the two fractions described above.

Step (b)

Optionally, this fraction is admitted in the presence of hydrogen (line 6) in a zone (7) containing a hydrotreatment catalyst which has the objective of reducing the content of olefinic and unsaturated compounds as well as possibly decomposing the oxygenated compounds ( mainly alcohols) present in the heavy fraction described above, as well as possibly breaking down any traces of sulfur and nitrogen compounds present in the heavy fraction. This hydrotreating step is non-converting, i.e. the conversion of the fraction 370 ⁰ C. ⁺ fraction 370 ⁰ C ^"is preferably less than 20% by weight, preferably less than 10% by weight and very preferably less than 5% by weight.

The catalysts used in this step (b) are hydrotreatment catalysts described in step b) of Embodiment 1.

In the hydrotreatment reactor (7), the feedstock is brought into contact in the presence of hydrogen and the catalyst at operating temperatures and pressures which make it possible to hydrogenate the olefins present in the feedstock. Preferably, the catalyst and the operating conditions chosen will also make it possible to carry out the hydrodeoxygenation, ie the decomposition of the oxygenated compounds (mainly alcohols) and / or the hydrodesulfurization or hydrodenitrogenation of the possible traces of sulfur compounds. and / or nitrogen present in the charge. The reaction temperatures used in the hydrotreatment reactor are between 100 and 400 ° C., preferably between 150 and 350 ° C., even more preferably between 150 and 300 ^° C. The total pressure range used varies from 5 to 150 bar, preferably between 10 and 100 bar and even more preferably between 10 and 90 bar. The hydrogen that feeds the hydrotreatment reactor is introduced at a rate such that the volume ratio hydrogen / hydrocarbons is between 50 to 3000 normal liters per liter, preferably between 100 and 2000 normal liters per liter and even more preferably between 150 and 1500 normal liters per liter. The charge rate is such that the hourly volume velocity is between 0.1 and 10 h ^-1 , preferably between 0.2 and 5 h ^-1 and even more preferably between 0.2 and 3 h ^-1 . Under these conditions, the content of unsaturated and oxygenated molecules is reduced to less than 0.5% by weight and to less than 0.1% by weight in general.The hydrotreating step is conducted under conditions such that the conversion to products having boiling points greater than or equal to 370 ^° C. in products having boiling points below 370 ^° C. is limited to 20% by weight, preferably less than 10% by weight, and so even more preferred is less than 5% by weight.

Step (c)

The effluent (line 8) from the hydrotreatment reactor (7) is optionally introduced into a water removal zone (9), the purpose of which is to eliminate at least partly the water produced during the reaction reactions. hydrotreating. This removal of water can be carried out with or without eliminating the C ₄ less gas fraction which is generally produced during the hydrotreating step. The elimination of water is understood to mean the elimination of the water produced by the oxygenation hydrodeoxygenation reactions, but it may also include the elimination at least partly of the water of saturation of the hydrocarbons. The elimination of water can be carried out by all the methods and techniques known to those skilled in the art, for example by drying, passage on a desiccant, flash, decantation ...

Step (d) The heavy fraction (optionally hydrotreated) thus dried is then introduced (line 10) as well as optionally a stream of hydrogen (line 11) into the zone (12) containing the catalyst used in the process according to the invention and under the operating conditions of the process of the present invention. Another possibility of the process also according to the invention consists in sending all the effluent leaving the hydrotreating reactor (without drying) into the reactor containing the catalyst according to the invention and preferably at the same time as a stream of 'hydrogen.

Before use in the reaction, if the hydrogenating phase of the catalyst consists of at least one noble metal, the metal contained in the catalyst must be reduced. One of the preferred methods for conducting the reduction of the metal is the treatment in hydrogen at a temperature of between 150 ° C. and 650 ^° C. and a total pressure of between 1 and 250 bar. For example, a reduction consists of a plateau at 150 ^° C. for 2 hours and then a rise in temperature up to 450 ^° C. at a rate of 1 ° C./min and then a plateau of 2 hours at 450 ^° C. throughout this reduction step, the hydrogen flow rate is 1000 normal liters hydrogen / liter catalyst. Note also that any ex-situ reduction method is suitable.

The operating conditions under which this step (d) is carried out are the operating conditions described according to the process according to the invention.

The hydroisomerization and hydrocracking step is carried out under conditions such that the pass conversion into products with boiling points greater than or equal to 370 ^° C. into products having boiling points below 370 ^° C. greater than 40% by weight, and even more preferably at least 50%, preferably greater than 60%, so as to obtain middle distillates (gas oil and kerosene) having sufficiently good cold properties (pour point , freezing point) to meet the applicable specifications for this type of fuel.

Step (e ^

The effluent (so-called hydrocracked / hydroisomerized fraction) at the outlet of the reactor (12), step (d), is sent to a distillation train (13), which incorporates atmospheric distillation and optionally vacuum distillation, the purpose of which is to separate the conversion products having a boiling point of less than 340 ° C. and preferably less than 370 ° C. and including especially those formed during step (d) in the reactor (12), and of separating the residual fraction whose initial boiling point is generally greater than at least 340 ^° C. and preferably greater than or equal to at least 37 ^° C. Among the conversion and hydroisomerized products, it is separated in addition to the light CrC ₄ gases (line 14). at least one gasoline fraction (line 15), and at least one middle distillates fraction kerosene (line 16) and diesel (line 17). The residual fraction whose initial boiling point is generally greater than at least 350 ^° C. and preferably greater than or equal to at least 370 ° C. is recycled (line 18) at the top of the hydroisomerisation reactor (12) and hydrocracking.

It may also be advantageous to recycle (line 19) in step (d) (reactor 12) part of the kerosene and / or diesel fuel thus obtained. Embodiment 3

Another embodiment of the invention comprises the following steps: a) Fractionation (step a) of the feedstock in at least 3 fractions: at least one intermediate fraction having an initial boiling point T1 between

120 and 200 ⁰ C ₁ and a final boiling point T2 greater than 300 ⁰ C and less than 410 ⁰ C,

at least one light fraction boiling below the intermediate fraction,

at least one heavy fraction boiling above the intermediate fraction. b) Hydrotreatment (step b) of at least a portion of said intermediate fraction, then passage (step d) in a process for treating at least a portion of the hydrotreated fraction on a hydroisomerizing catalyst c) disposal of at least a portion of the water produced during the hydrotreatment reactions and optionally CO, CO ₂ , NH ₃ , H ₂ S, f) Passage (step f) in the process according to the invention of at least part of said fraction heavy with a conversion of products 370 ⁰ C ⁺ 370 ^c in products less than 40% by weight. e) and g) Distillation (steps e and g) of at least a portion of the hydrocracked / hydroisomerized fractions to obtain middle distillates.

The description of this embodiment will be made with reference to FIG. 3 without limiting the interpretation.

Step (a)

The effluent from the Fischer-Tropsch synthesis unit comprises mainly paraffins, but also contains olefins and oxygenated compounds such as alcohols.

It also contains water, CO ₂ , CO and unreacted hydrogen as well as light hydrocarbon compounds Ci to C ₄ in the form of gas, or possibly sulfur or nitrogen impurities. The effluent from the Fischer-Tropsch synthesis unit arriving via line (1) is fractionated in a fractionation zone (2) in at least three fractions: at least one light fraction (leaving via line 3), the constituent compounds of which have boiling points below a temperature T1 of between 120 and 200 ^° C., and preferably between 130 and 180 ^° C., and even more preferred at a temperature of about 150 ^° C. In other words the cutting point is between 120 and 200 ^° C.

at least one intermediate fraction (line 4) comprising compounds whose boiling points are between the cut point T1, previously defined, and a temperature T2 greater than 300 ^° C., more preferably still greater than 350 ^° C. and less than 410 ° C or better at 370 ° C.

at least one so-called heavy fraction (line 5) comprising compounds having boiling points above the previously defined cutting point T2.

Cutting at 37O ⁰ C makes it possible to separate at least 90% by weight of oxygenates and olefins, and most often at least 95% by weight. The heavy cut to be treated is then purified and removal of the heteroatoms or unsaturated by hydrotreating is then not necessary.

Fractionation is obtained here by distillation, but it can be carried out in one or more steps and by other means than distillation.

This fractionation can be carried out by methods well known to those skilled in the art such as flash, distillation etc. As a non-limiting example, the effluent from the Fischer-Tropsch synthesis unit will be subject to flash, decantation to remove water and distillation to obtain at least the two fractions described above.

The light fraction is not treated according to the process of the invention but may for example constitute a good load for a petrochemical unit and more particularly for a steam cracker (steam cracking unit 6).

The heavier fractions previously described are treated according to the process of the invention. Step (b)

Said intermediate fraction is admitted via line (4), in the presence of hydrogen supplied by the pipe (7), into a hydrotreatment zone (8) containing a hydrotreatment catalyst, which aims to reduce the olefinic and unsaturated compounds as well as possibly decompose the oxygenated compounds (mainly alcohols) present in the heavy fraction described above, as well as possibly decompose any traces of sulfur and nitrogen compounds present in the heavy fraction. This hydrotreating step is non-converting, that is to say that the conversion of the 150 ⁰ C ⁺ fraction to 150 ⁰ C ^" fraction is preferably less than 20% by weight, preferably less than 10% by weight and very preferably less than 5% by weight.

The catalysts used in this step (b) are hydrotreatment catalysts described in step b) of Embodiment 1,

In the hydrotreatment reactor (8), the feedstock is brought into contact in the presence of hydrogen and the catalyst at operating temperatures and pressures which make it possible to hydrogenate the olefins present in the feedstock. Preferably, the catalyst and the operating conditions chosen will also make it possible to carry out the hydrodeoxygenation, ie the decomposition of the oxygenated compounds (mainly alcohols) and / or the hydrodesulfurization or hydrodenitrogenation of the possible traces of sulfur compounds. and / or nitrogen present in the charge. The reaction temperatures used in the hydrotreatment reactor are between 100 and 400 ^° C., preferably between 150 and 350 ^° C., more preferably between 150 and 300 ° C. The total pressure range used varies from 5 to 150 bar, preferably from 10 to 100 bar and even more preferably from 10 to 90 bar. The hydrogen which feeds the hydrotreatment reactor is introduced at a rate such that the volume ratio hydrogen / hydrocarbons is between 50 to 3000 normal liters per liter, preferably between 100 and 2000 normal liters per liter and even more preferably between 150 and 1500 normal liters per liter. The charge rate is such that the hourly volume velocity is between 0.1 and 10 h ^-1 , preferably between 0.2 and 5 h ^-1 and even more preferably between 0.2 and 3 h ^-1 . Under these conditions, the content of unsaturated and oxygenated molecules is reduced to less than 0.5% by weight and to less than 0.1% by weight in general. The hydrotreating step is carried out under conditions such that the conversion to products having boiling points greater than or equal to 150 ° C. to products having boiling points below 150 ^° C. is limited to 20% by weight. pds, of Preferably, it is less than 10% by weight and even more preferably less than 5% by weight.

Step (c)

The effluent from the hydrotreatment reactor is optionally introduced into a zone (9) of water removal which aims to remove at least a portion of the water produced during the hydrotreatment reactions. This removal of water can be performed with or without removal of the gaseous fraction C ₄ less which is generally produced during the hydrotreatment step. The elimination of water is understood to mean the elimination of the water produced by the oxygenation hydrodeoxygenation reactions, but it may also include the elimination at least partly of the saturation water of the hydrocarbons. The removal of water can be carried out by all the methods and techniques known to those skilled in the art, for example by drying, passage on a desiccant, flash, decantation ....

Step f d)

The fraction thus possibly dried is then introduced (line 10), as well as possibly a stream of hydrogen (line 11) into the zone (12) containing a hydroisomerizing catalyst. Another possibility of the process also according to the invention consists in sending all of the effluent leaving the hydrotreating reactor (without drying) into the reactor containing the hydroisomerizing catalyst and preferably at the same time as a stream of hydrogen.

The hydroisomerizing catalysts are as described in step d) of Embodiment 1). The operating conditions in which this step (d) is carried out are:

The pressure is maintained between 2 and 150 bar and preferably between 5 and 100 bar and advantageously from 10 to 90 bar, the space velocity is between 0.1 h ^-1 and 10 h ^-1 and preferably between 0.2 and 7h ^"1 is advantageously between 0.5 and 5, Oh ^{" 1} . The hydrogen flow rate is adjusted to obtain a ratio of 100 to 2000 normal liters of hydrogen per liter of feedstock and preferably between 150 and 1500 liters of hydrogen per liter of feedstock.

The temperature used in this step is between 200 and 45O ⁰ C and preferably from 250 ^° C. to 450 ^° C., advantageously from 300 to 450 ^° C., and even more advantageously above 320 ° C. or for example between 320 and 420 ^° C.

The hydroisomerization and hydrocracking step (d) is advantageously carried out under conditions such that the pass conversion into products with boiling points greater than or equal to 150 ^° C. in products having boiling points below 150 ° C is the lowest possible, preferably less than 50%, even more preferably less than

30%, and allows to obtain middle distillates (diesel and kerosene) with cold properties (pour point and freezing) sufficiently good to meet the specifications in force for this type of fuel.

Thus, in this step (d), it is sought to promote hydroisomerization rather than hydrocracking.

Step ffî

Said heavy fraction whose boiling points are higher than the previously defined cutting point T2, is introduced via line (5) into a zone (13) where it is placed, in the presence of hydrogen (26), in contact with a catalyst according to the invention and under the operating conditions of the process of the present invention to produce a cut middle distillates (kerosene + gas oil) with good properties cold.

The catalyst used in the zone (13) of step (f) to carry out the hydrocracking and hydroisomerization reactions of the heavy fraction, defined according to the invention, is of the same type as that present in the reactor (12). ), that is to say as defined above in the first part of the patent application. It should be noted that the catalysts used in the reactors (12) and (13) may be strictly identical or different (for example, by varying the proportion of the zeolite in the catalyst, the nature of the binder or the quantity and nature of the hydrogenating phase as well as the nature of the acidic solid).

During this step (f) the fraction 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 allow to improve the quality of the formed products and more particularly the cold properties of kerosene and diesel, and also to obtain very good yields of middle distillates. Conversion to products having boiling points greater than or equal to 370 ^° C. in point products boiling below 37O ⁰ C is greater than 40% by weight, often at least 50% and preferably greater than or equal to 60%.

In this step (f), it will therefore seek to promote hydrocracking, but preferably by limiting the cracking of diesel fuel.

The choice of operating conditions makes it possible to finely adjust the quality of products (diesel, kerosene) and in particular the cold properties of kerosene, while maintaining a good yield of diesel and / or kerosene. The method according to the invention makes it quite interesting to produce both kerosene and diesel fuel, which are of good quality while minimizing the production of lighter, unwanted cuts (naphtha, LPG).

Step (α ^

The effluent at the outlet of the reactor (12), step (d), is sent to a distillation train, which incorporates an atmospheric distillation and optionally a vacuum distillation, and whose purpose is to separate, on the one hand, the light products inevitably formed during step (d), for example the gases (C _r C ₄ ) (line 14) and a petrol section (line 19), and distilling at least one gasoil section (line 17) and kerosene (line 16) . The gas oil and kerosene fractions can be recycled (line 25) partly, jointly or separately, at the top of the hydroisomerization reactor (12) of step (d).

The effluent leaving step (f) is subjected to a separation step in a distillation train so as to separate, on the one hand, the light products inevitably formed during step (f), for example the gases (C ₁ -C ₄ ) (line 18) and a petrol cut (line 19), to distil a diesel cut (line 21) and kerosene (line 20) and to distil the fraction (line 22) boiling over diesel fuel that is, the compounds which constitute it have boiling points higher than those of middle distillates (kerosene + gas oil). This fraction, called the residual fraction, generally has an initial boiling point of at least 350 ^° C., preferably greater than 37 ^° C. This non-hydrocracked fraction is advantageously recycled to the top of the hydroisomerization / hydrocracking reactor (13). step (f).

It may also be advantageous to recycle a portion of the kerosene and / or diesel in step (d), step (f) or both. Preferably, at least one of the kerosene and / or diesel fractions is recycled in part (line 25) in step (d) (zone 12). We could note that it is advantageous to recycle a portion of kerosene to improve its properties cold.

Advantageously and at the same time, the non-hydrocracked fraction is partially recycled in step (f) (zone 13).

In Figure 3, there are shown two columns (23) and (24) of distillation, but only one can be used to treat all the sections from areas (12) and (13).

In Figure 3, there is shown only the recycling of kerosene on the reactor catalyst (12). It goes without saying that one can also recycle a portion of the gas oil (separately or with kerosene) and preferably on the same catalyst as kerosene. It is also possible to recycle some of the kerosene and / or diesel fuel produced in the lines (20) (21).

Embodiment 4 Another embodiment of the invention comprises the following steps:

a) optionally fractionation of the feedstock into at least one heavy fraction with initial boiling point of between 120 and 200 ^° C., and at least one light fraction boiling below said heavy fraction, b) optional hydrotreatment of a part at least one of the feed or of the heavy fraction, optionally followed (step c) of removing at least part of the water, d) passing of at least a portion of the effluent or the fraction possibly hydrotreated in the process according to the invention on a first catalyst according to the invention e) distillation of the hydroisomerized / hydrocracked effluent to obtain middle distillates (kerosene, gas oil) and a residual fraction boiling over middle distillates, f) passage at least a portion of said residual heavy fraction and / or a part of said middle distillates in the process according to the invention on a second catalyst according to the invention, and distillation of the resulting effluent to obtain middle distillates.

The description of this embodiment will be made with reference to FIGS. 4 and 5, without these figures limiting the interpretation. Step a)

When this step is carried out, the effluent from the Fischer-Tropsch synthesis unit is fractionated (for example by distillation) into at least two fractions: at least one light fraction and at least one heavy fraction with initial boiling point. equal to a temperature between 120 and 200 ⁰ C and preferably between 130 and 180 ⁰ C and even more preferably at a temperature of about 15O ⁰ C, in other words the cutting point is between 120 and 200 ⁰ C.

The heavy fraction generally has paraffin contents of at least 50% by weight.

The light fraction is not treated according to the process of the invention but may for example constitute a good load for petrochemicals and more particularly for a steam cracking unit. At least one heavy fraction previously described is treated according to the method of the invention.

Step b)

Optionally, this fraction or at least part of the initial charge is admitted via line (1) in the presence of hydrogen (supplied via line (2)) to an area (3) containing a hydrotreatment catalyst which has for the purpose of reducing the content of olefinic and unsaturated compounds as well as possibly decomposing the oxygenated compounds (mainly alcohols) present in the heavy fraction described above, as well as possibly decomposing possible traces of sulfur and nitrogen compounds present in the heavy fraction. This hydrotreating step is non-converting, i.e. the conversion of the fraction 370 ⁰ C. ⁺ fraction 370 ⁰ C ^"is preferably less than 20% by weight, preferably less than 10% by weight and very preferably less than 5% by weight.

The catalysts used in this step (b) are described in step b) of Embodiment 1. In the hydrotreating reactor (3), the feedstock is brought into contact in the presence of hydrogen and the catalyst at operating temperatures and pressures for carrying out the hydrogenation of the olefins present in the feedstock. Preferably, the catalyst and the operating conditions chosen will also make it possible to carry out the hydrodeoxygenation, ie the decomposition of the oxygenated compounds (mainly alcohols) and / or the hydrodesulfurization or hydrodenitrogenation of the possible traces of sulfur compounds. and / or nitrogen present in the charge. The reaction temperatures used in the hydrotreatment reactor are between 100 and 400 ° C., preferably between 150 and 350 ^° C., more preferably between 150 and 300 ^° C. The total pressure range used varies from 5 to 150 bar, preferably between 10 and 100 bar and even more preferably between 10 and 90 bar. The hydrogen which feeds the hydrotreatment reactor is introduced at a rate such that the volume ratio hydrogen / hydrocarbons is between 50 to 3000 normal liters per liter, preferably between 100 and 2000 normal liters per liter and even more preferably between 150 and 1500 normal liters per liter. The charge rate is such that the hourly volume velocity is between 0.1 and 10 h ^-1 , preferably between 0.2 and 5 h ^-1 and even more preferably between 0.2 and 3 h ^-1 . Under these conditions, the content of unsaturated and oxygenated molecules is reduced to less than 0.5% by weight and to less than 0.1% by weight in general.The hydrotreating step is conducted under conditions such that the conversion to products having boiling points greater than or equal to 37O ⁰ C in products having boiling points below 370 ° C is limited to 20% by weight, preferably less than 10% by weight and so even more preferred is less than 5% by weight.

Step c)

The effluent (line 4) from the hydrotreatment reactor (3) is optionally introduced into a zone (5) for removing water, the purpose of which is to eliminate at least part of the water produced during the reaction reactions. hydrotreating. This removal of water can be carried out with or without eliminating the C ₄ less gas fraction which is generally produced during the hydrotreating step. The elimination of water is understood to mean the elimination of the water produced by the oxygenated hydrodeoxygenation reactions, but it may also include the elimination of at least a part of the hydrocarbon saturation water. The removal of water can be carried out by all the methods and techniques known to those skilled in the art, for example by drying, passage on a desiccant, flash, decantation .... Step d)

At least part and preferably all of the hydrocarbon fraction (at least part of the feed or at least part of the heavy fraction of step a) or at least part of the hydrotreated fraction or feed and optionally dried) is then introduced (line 6) and optionally a stream of hydrogen (line 7) into the zone (8) containing the catalyst according to the invention. Another possibility of the process also according to the invention consists in sending part or all of the effluent flowing out of the hydrotreating reactor (without drying) into the reactor containing the catalyst according to the invention and preferably at the same time as a stream hydrogen.

Before use in the reaction, if the hydrogenating phase of the catalyst consists of at least one noble metal, the metal contained in the catalyst must be reduced. One of the preferred methods for conducting the reduction of the metal is the treatment in hydrogen at a temperature of between 150 ° C. and 650 ^° C. and a total pressure of between 1 and 250 bar. For example, a reduction consists of a plateau at 150 ^° C. for 2 hours and then a rise in temperature up to 450 ^° C. at the rate of 1 ° C./min and then a plateau of 2 hours at 450 ° C. during this whole stage of. reduction, the hydrogen flow rate is 1000 liters hydrogen / liter catalyst. Note also that any ex-situ reduction method is suitable.

Step e)

The hydroisomerized / hydrocracked effluent leaving the reactor (8), step (d), is sent to a distillation train (9) which incorporates an atmospheric distillation and optionally a vacuum distillation which is intended to separate the conversion products. of boiling point below 340 ⁰ C and preferably below 370 ⁰ C and including including those formed in step (d) in the reactor (8), and to separate the residual fraction whose initial point of boiling is generally greater than at least 34O ⁰ C and preferably greater than or equal to at least 37O ⁰ C. Among the conversion products and hydroisomerized it is separated, in addition to light gases Ci-C ₄ (line 10) at least a fraction gasoline (line 11), and at least one middle kerosene distillate fraction (line 12) and diesel (line 13).

Step fl The process according to the invention uses a second zone (16) containing a hydroisomerization / hydrocracking catalyst according to the invention. It passes on this catalyst, in the presence of hydrogen (line 15) an effluent selected from a portion of the product kerosene (line 12), a portion of the gas oil (line 13) and the residual fraction and preferably the residual fraction of which the initial boiling point is generally greater than at least 370 ^° C.

During this step, the fraction entering the reactor (16) undergoes, in the presence of hydrogen, hydroisomerization and / or hydrocracking reactions in the reactor, which will make it possible to improve the quality of the products formed and more particularly the properties cold kerosene and diesel, and obtain distillate yields improved over the prior art.

The choice of operating conditions makes it possible to finely adjust the quality of the products (middle distillates) and in particular the cold properties.

The operating conditions in which this step (f) is carried out are the operating conditions in accordance with the process according to the invention.

The operator will adjust the operating conditions on the first and second hydrocracking / hydroisomerization catalyst so as to obtain the desired product qualities and yields.

Thus, generally, on the first catalyst, the pass conversion to products with boiling points greater than or equal to 150 ° C. in products with boiling points below 150 ° C. is less than 50% by weight, preferably less than 30% by weight. These conditions allow the individual to adjust the ratio kerosene / diesel produced and the cold properties of middle distillates, and more particularly kerosene.

Also generally, on the second catalyst, when the residual fraction is treated, the conversion per pass to products with boiling points greater than or equal to 370 ^° C. in products with boiling points below 37 ^° C., is superior. at 40% by weight, preferably above 50% by weight, or better at 60% by weight. It can even be advantageous to have conversions of at least 80% weight.

When part of the kerosene and / or diesel fuel is treated on the second catalyst, the pass conversion to products with boiling points greater than or equal to 150 ^° C. in products with boiling points below 150 ^° C. is less than 50% by weight, preferably less than 30% by weight.

In general, the operating conditions applied in the reactors (8) and (16) may be different or identical. Preferably, the operating conditions used in the 2 hydroisomerization / hydrocracking reactors are chosen to be different in terms of operating pressure, temperature, contact time (vvh) and H ₂ / feed ratio. This embodiment allows the operator to adjust the qualities and / or yields of kerosene and diesel.

The effluent from the reactor (16) is then sent via line (17) in the distillation train so as to separate the conversion products, gasoline, kerosene and diesel.

In FIG. 4, there is shown an embodiment with the residual fraction (line 14) passing through the hydroisomerization / hydrocracking zone (16) (step f), the effluent obtained being sent (line 17) into the zone (9) separation.

Advantageously, at the same time, the kerosene and / or the diesel can be partly recycled (line 18) in the zone (8) of hydroisomerization / hydrocracking (step d) on the first catalyst.

In FIG. 5, a portion of the kerosene and / or diesel fuel produced passes into the hydroisomerization / hydrocracking zone (16) (step f), the effluent obtained being sent (line 17) to the separation zone (9). .

At the same time, the residual fraction (line 14) is recycled to the hydroisomerization / hydrocracking zone (8) (step d) on the first catalyst.

It has been found that it is advantageous to recycle part of the kerosene on a hydrocracking / hydroisomerization catalyst to improve its cold properties.

In the figures, only the recycling of kerosene has been shown. It goes without saying that one can also recycle a portion of the gas oil (separately or with kerosene) and preferably on the same catalyst as kerosene. The invention is not limited to these 4 embodiments.

The products obtained

The gas oil (s) obtained have a pour point of at most 0 ^° C., generally below -10 ^° C. and often below -15 ° C. The cetane number is greater than 60, generally greater than 65, often greater than 70.

The kerosene (s) obtained have a freezing point of not more than -35 ^° C., generally less than -40 ^° C. The smoke point is greater than 25 mm, generally greater than 30 mm. In this process, the production of gasoline (not sought) is as low as possible. The yield of gasoline will always be less than 50% by weight, preferably less than 40% by weight, advantageously less than 30% by weight, or even 20% by weight or even 15% by weight.

Example 1 Preparation of a catalyst not according to the invention (CD

A silica-alumina precursor SA1 is prepared in the following manner: An alumina hydrate is prepared according to the teachings of US-A-3,124,418. After filtration, the precipitate of freshly prepared P1 is mixed with a solution of silicic acid prepared by exchange on decationizing resin. The proportions of the two solutions are adjusted so as to reach a composition of 70% Al ₂ O ₃ - 30% SiO ₂ on the final support. This mixture is rapidly homogenized in a commercial colloid mill in the presence of nitric acid so that the nitric acid content of the suspension at the mill outlet is 8% based on the mixed silica-alumina solid. Then, the suspension (P2) is conventionally dried in an atomizer in a conventional manner from 300 ° C. to 60 ^° C. The powder thus prepared is shaped in a Z-shaped arm in the presence of 8% of nitric acid with respect to anhydrous product. The extrusion is carried out by passing the paste through a die provided with orifices of diameter 1, 4 mm. The extrudates S1 containing 100% silica-alumina thus obtained are dried at 150 ^° C. and then calcined at 550 ° C.

The catalyst C1 is obtained by dry impregnation of the support S1 (in the form of extrudates) with a hexachloroplatinic acid solution H ₂ PtCl ₆ dissolved in a volume of solution corresponding to the total pore volume to be impregnated. The impregnated extrudates are then calcined at 55 ^° C. under air for 4 hours. The platinum content is 0.48% by weight and its dispersion measured by H ₂ -O ₂ titration is 86% and its distribution is uniform in the extrudates. Example 2 Preparation of a Catalyst According to the Invention (C2)

The zeolite ZBM-30 is synthesized according to the patent BASF EP-A-46504 with the organic structuring triethylenetetramine. Then it is calcined at 550 ^° C. under a stream of dry air for 12 hours. The zeolite H-ZBM-30 (acid form) thus obtained has an Si / Al ratio of 45 and an Na / Al ratio of less than 0.001.

5 g of zeolite ZBM-30 and 15 g of the precursor of the silica-alumina P2 described in Example 1 are then mixed. This mixture is made before introduction into the extruder. The zeolite powder is first wetted and added to the matrix suspension in the presence of 66% nitric acid (7% by weight of acid per gram of dry gel) and then kneaded for 15 minutes. At the end of this mixing, the paste obtained is passed through a die having cylindrical orifices of diameter equal to 1.4 mm. The extrudates are then dried overnight at 120 ° C. in air and then calcined at 550 ^° C. under air. The extrudates S2 contain 20% by weight ZBM-30 zeolite and 80% silica-alumina.

The catalyst C2 is obtained by dry impregnation of the support S2 (in the form of extrudates) with a hexachloroplatinic acid solution H ₂ PtCl ₆ dissolved in a volume of solution corresponding to the total pore volume to be impregnated. The impregnated extrudates are then calcined at 550 ^° C. under air for 4 hours. The platinum content is 0.47% by weight and its dispersion measured by H ₂ -O ₂ titration is 88% and its distribution is uniform in the extrudates.

Example 3 Preparation of a Catalyst According to the Invention (C3)

The COK-7 zeolite is synthesized according to patent application FR 2 882 744. It is then subjected to calcination at 550 ^° C. under a stream of dry air for 12 hours. The zeolite H-COK-7 (acid form) thus obtained has an Si / Al ratio of 37 and an Na / Al ratio of less than 0.003.

5 g of zeolite COK-7 and 28 g of the precursor of the silica-alumina P2 described in Example 1 are then mixed. This mixture is made before introduction into the extruder. The zeolite powder is first wetted and added to the matrix suspension in the presence of 66% nitric acid (7% by weight of acid per gram of dry gel) and then kneaded for 15 minutes. At the end of this mixing, the paste obtained is passed through a die having cylindrical orifices of diameter equal to 1, 4 mm. The extrudates are then dried overnight at 120 ^° C. under air and then calcined at 550 ^° C. under air. The extrusions S3 contain 15% by weight of COK-7 zeolite and 85% by weight of silica-alumina.

The catalyst C3 is obtained by dry impregnation of the support S2 (in the form of extrudates) with a solution of hexachloroplatinic acid H ₂ PtCl ₆ dissolved in a volume of solution corresponding to the total pore volume to be impregnated. The impregnated extrudates are then calcined at 550 ^° C. under air for 4 hours. The platinum content is 0.47% by weight and its dispersion measured by H ₂ -O ₂ titration is 88% and its distribution is uniform in the extrudates.

EXAMPLE 4 Preparation of a Catalyst According to the Invention (C4) 2 g of COK-7 zeolite (Example 3 = 0.3 g of zeolite ZBM-30 (example 2) and 28 g of the precursor of silica-alumina are mixed together P2 is described in Example 1. This mixing is done before introduction into the extruder The zeolite powder is pre-wetted and added to the matrix suspension in the presence of 66% nitric acid (7% w / w). acid per gram of dry gel) then kneaded for 15 minutes At the end of this kneading, the paste obtained is passed through a die having cylindrical orifices with a diameter of 1.4 mm The extrudates are then dried overnight at 120 ^° C. under air and then calcined at 550 ^° C. under air The extrusions S4 contain 6% by weight of COK-7 zeolite, 9% by weight of ZBM-30 and 85% of silica-alumina

The catalyst C4 is obtained by dry impregnation of the support S4 (in the form of extrudates) with a hexachloroplatinic acid solution H ₂ PtCl ₆ dissolved in a volume of solution corresponding to the total pore volume to be impregnated. The impregnated extrudates are then calcined at 550 ° C. in air for 4 hours. The platinum content is 0.47% by weight and its dispersion measured by H ₂ -O ₂ titration is 88% and its distribution is uniform in the extrudates.

Example 5 Evaluation of Catalysts C1, C2, C3 C4 in hydrocracking of a paraffinic charge resulting from the Fischer-Tropsch synthesis

A feed from the Fischer Tropsch synthesis on a cobalt catalyst is separated into two fractions, the heaviest fraction having the following characteristics (Table 1).

This heavy fraction is treated in a hydrogen traversed bed lost on the above hydrotreatment catalyst under operating conditions that allow the elimination of olefinic and oxygen compounds and traces of nitrogen. The operating conditions selected are the following:

- WH (load volume / volume of catalyst / hour) = 2 h ^'1 total working pressure: 50 bar - hydrogen ratio / load: 200 normal liters / liter

- temperature: 270 ⁰ C Table 1: Characteristics of the heavy fraction

After this hydrotreatment, the contents of olefins, oxygenates and nitrogenous compounds of the effluent fall below the detection thresholds, whereas the conversion of the fraction 37O ⁰ C ⁺ fraction 370 ⁰ C ^" is negligible (less than 5% by weight or Table 2. The carbon monoxide and / or carbon dioxide and / or water and / or ammonia formed during the hydrotreatment are removed by a flash and decant step.

Table 2: Characteristics of the heavy fraction after hydrotreatment.

The hydrotreated effluent constitutes the hydrocracking feedstock sent onto the catalysts C1 (non-compliant) and C2, C3 and C4 (in accordance with the invention).

Before testing, each catalyst undergoes a reduction step under the following operating conditions:

Hydrogen flow rate: 1600 normal liters per hour and per liter of catalyst. Rise in ambient temperature 120 ^° C.: 10 ° C./min. One hour at 120 ° C. Increase from 120 ° to 450 ° C. at 5 ° C. min

Two-hour stage at 450 ° C Pressure: 1 bar After reduction, the catalytic test is carried out under the following conditions:

Total pressure of 50 bar, ratio H ₂ on load of 800 normal liters / liter

Space velocity (WH) equal to 2h-1

The conversion of the fraction is taken equal to:

CN 370 ⁰ C ^"= [(% 370 ⁰ ^C" _Ements) - (% of 370 ° C ^_"load)] / [100 - (% of 37o C ⁰ - _load)] with

% 370 ⁰ C ^_'eff iu _e nt _s = weight content of compounds having boiling points below 370 ⁰ C in the effluent, and

% 370 ⁰ C ^_"cha r _ge ⁼ weight content of compounds having boiling points below 370 ⁰ C in the feed.

The catalytic performances obtained are given in Tables 3 and 4 below. The temperature of the reactor is adjusted so as to obtain a conversion of the 370 ⁰ C ⁺ fraction of 70% by weight (Table 1). Chromatography analyzes gas provide yields of the fraction 150-370 ⁰ C in the hydrocracked effluent (Table 3).

Table 3: Temperature to reach a net conversion in 370 ⁰ C- about 70%

Table 4: Yields of the products formed:

These results show (Tables 3 and 4) that the use of the catalysts according to the invention and in a process according to the invention makes it possible, by hydrocracking of a paraffinic filler resulting from the Fischer-Tropsch synthesis process, to obtain better yields. in middle distillates, cuts 150-370 ^° C. with a catalyst of the prior art.

Comparative Example 6 Evaluation of Catalysts C1 in Combination with Hydrocracking C2 of a Paraffinic Filler Resulting from Fischer-Tropsch Synthesis

In this example, the hydrocracking step is composed of two reaction stages on two different catalysts C1 and C2.

The hydrotreated effluent of Example 5 (Table 2) is converted to the catalyst C1 and then to the catalyst according to the invention C2, based on ZBM-30. Both catalysts are placed in two reactors in series. Before testing, the catalysts undergo a reduction step identical to that of Example 5. The hydrotreated effluent is sent to the catalyst C1 (platinum / silica-alumina) under the following operating conditions:

- WH (volume of charge / volume of catalyst / hour) = 2 h -1

- total working pressure: 50 bar - hydrogen / feed ratio: 800 normal liters / liter

- temperature: 347 ° C

The temperature of the reactor is adjusted so as to obtain a conversion of the 37O ⁰ C + fraction of 70% by weight.

The effluent is brought into contact with the selective catalyst C2 (platinum / ZBM-30) under the operating conditions below:

- WH (volume of charge / volume of catalyst / hour) = 1 h-1

- total working pressure: 50 bar hydrogen / feed ratio: 1000 normal liters / liter The temperature is adjusted so as to have a conversion of the fraction 370 ° C + fraction 370 ⁰ C- less than 5% by weight when the hydroisomerization. The gas chromatographic analyzes make it possible to obtain the distribution of the different sections in the hydrocracked effluent and then hydroisomerized (Table 5).

Table 5:

Compared to Example 2 according to the invention, the successive conversion of the feedstock (see Table 2) on two catalysts C1 and then C2 leads, at close total conversion (around 72%), has a lower average distillate yield. to that obtained in Example 5, that is to say the use of a catalyst comprising zeolite ZBM-30 and silica-alumina.

Claims

1. Process for producing middle distillates from a paraffinic feedstock produced by Fischer-Tropsch synthesis, using a hydrocracking / hydroisomerization catalyst comprising at least at least one hydro-dehydrogenating metal selected from the group formed by metals group VIB and group VIII of the Periodic Table and a support comprising at least one silica-alumina and at least one zeolite selected from the group consisting of zeolites of structural type TON, FER, MTT, zeolites ZBM-30, 2SM -48 and COK-7, taken alone or in a mixture, said process operating at a temperature between 270 and 400 ° C, a pressure of between 1 and 9 MPa, a space velocity between 0.5 and 5 h-1, a flow rate of hydrogen adjusted to obtain a ratio of 400 to 1500 normal liters of hydrogen per liter of charge.

2. Method according to claim 1 wherein said process operates at a temperature between 300 and 390 ⁰ C, a pressure of between 2 and 8 MPa, a space velocity between 0.8 and 3 h-1, a flow rate of hydrogen adjusted to obtain a ratio of 600 and 1300 normal liters of hydrogen per liter of charge.

3. Method according to one of claims 1 or 2 wherein said hydrocracking / hydroisomerization catalyst comprises:

0.1 to 60% of at least one hydro-dehydrogenating metal selected from the group consisting of Group VIB and Group VIII metals, and a support comprising: 0 to 99% of at least one porous mineral binder amorphous or poorly crystallized oxide type (excluding silica-alumina)

0.1 to 40%, of at least one zeolite chosen from the group formed by the zeolites of the structural type TON, FER, MTT, the zeolites ZBM-30, ZSM-48 and COK-7, taken alone or as a mixture from 60 to 95% of silica -alumina, the percentages being expressed as a percentage by weight relative to the total mass of the catalyst.

4. Method according to one of claims 1 to 3 wherein said support of said hydrocracking / hydroisomerization catalyst is the COK-7 zeolite synthesized in the presence of the organic template triethylenetetramine.

5. Method according to one of claims 1 to 3 wherein said support of said hydrocracking / hydroisomerization catalyst is zeolite ZBM-30 synthesized in the presence of the organic template triethylenetetramine.

6. Method according to one of claims 1 to 3 wherein said support of said hydrocracking / hydroisomerization catalyst comprises zeolite COK-7, synthesized in the presence of the organic template triethylenetetramine, in a mixture with zeolite ZBM-30 synthesized in the presence of structuring organic triethylenetetramine.

7. Method according to one of claims 1 to 6 wherein said support of said catalyst comprises a homogeneous silica-alumina on a micrometer scale and contains an amount greater than 5% by weight and less than or equal to 95% by weight of silica, the silica content is advantageously between 10 and 50% by weight, said silica-alumina having the following characteristics: a mean pore diameter, measured by mercury porosimetry, of between 20 and 140 A, a total pore volume, measured by porosimetry at mercury, between 0.1 ml / g and 0.5 ml / g, a total pore volume, measured by nitrogen porosimetry, of between 0.1 ml / g and 0.5 ml / g, a BET specific surface area included between 100 and 550 m 2 / g, a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 140 A less than 0.1 ml / g, a pore volume, measured by mercury porosimetry, included in pore diameter greater than 160 A i less than 0.1 ml / g, a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 200 Å, less than 0.1 ml / g, a pore volume, measured by mercury porosimetry, included in pores with diameters greater than 500 A less than 0.1 ml / g. an X-ray diffraction pattern which contains at least the principal characteristic lines of at least one of the transition aluminas included in the group consisting of alpha, rho, chi, eta, gamma, kappa, theta and delta alumina.

8. Method according to one of claims 1 to 6 wherein said process comprises the following steps: a) separation of a single so-called heavy fraction with initial boiling point between

120-200 ⁰ C, b) hydrotreatment of at least a portion of said heavy fraction, c) fractionation into at least 3 fractions:

at least one intermediate fraction having an initial boiling point T1 of between 120 and 200 ^° C., and a final boiling point T 2 greater than 300 ^° C. and less than 410 ^° C.,

at least one light fraction boiling below the intermediate fraction, at least one heavy fraction boiling above the intermediate fraction. d) passing at least part of said intermediate fraction over a hydroisomerizing catalyst, e) passing at least part of said heavy fraction in the process according to the invention

f) distillation of the hydrocracked / hydroisomerized fractions to obtain middle distillates, and recycling of the residual fraction boiling above said middle distillates in step (e) on the catalyst according to the invention treating the heavy fraction.

9. Method according to one of claims 1 to 6 wherein said method comprises the following steps:

a) separation of at least a light fraction of the feedstock so as to obtain a single so-called heavy fraction with an initial boiling point of between 120-200 ^° C., b) hydrotreatment of said heavy fraction, optionally followed by step c) removal of at least a portion of the water and optionally CO, CO ₂ , NH ₃ , H ₂ S ₁ d) passing through the process according to the invention of at least part of said optionally hydrotreated fraction, conversion to the catalyst according to the invention described above products with boiling points greater than or equal to 37O ⁰ C in products with a boiling point of less than 370 ^° C. is greater than 40 wt.%, e) distillation of the hydrocracked / hydroisomerized fraction to obtain middle distillates, and recycling in step d) of the residual fraction boiling over said middle distillates.

10. Method according to one of claims 1 to 6 wherein said method comprises the following steps: a) Fractionation (step a) of the feedstock in at least 3 fractions:

at least one intermediate fraction having an initial boiling point T1 between 120 and 200 ^° C., and a final boiling point T 2 greater than 300 ° C. and less than 410 ° C.,

at least one light fraction boiling below the intermediate fraction, at least one heavy fraction boiling above the intermediate fraction. b) Hydrotreatment (step b) of at least a portion of said intermediate fraction, then passage (step d) in a process for treating at least a portion of the hydrotreated fraction on a hydroisomerizing catalyst c) disposal of at least a part of the water produced during the hydrotreatment reactions and optionally CO, CO ₂ , NH ₃ , H ₂ S, d) Passage (step f) in the process according to the invention of at least part of said fraction heavy with a product conversion 370 ⁰ C ⁺ products 37O ⁰ C less than 40% weight. e) and g) Distillation (steps e and g) of at least a portion of the hydrocracked / hydroisomerized fractions to obtain middle distillates.

11. Method according to one of claims 1 to 6 wherein said method comprises the following steps: a) any fractionation of the feedstock into at least one heavy fraction with an initial boiling point between 120 and 200 ^c C, and at least one light fraction boiling below said heavy fraction, b) optional hydrotreatment of a part at least one of the feedstock or the heavy fraction, optionally followed (step c) of removing at least part of the water, c) passing of at least a portion of the effluent or of the possibly hydrotreated fraction in the process according to the invention on a first catalyst according to the invention d) distillation of the hydroisomerized / hydrocracked effluent to obtain middle distillates (kerosene, gas oil) and a residual fraction boiling over middle distillates, e) passage at least a part of said residual heavy fraction and / or a part of said middle distillates, and distillation of the resulting effluent to obtain middle distillates in the process according to the invention on a second catalysis ur according to the invention.