FR2851569A1 - Two stage process of hydro-cracking, for producing gas-oil and middle distillates, involves using amorphous catalyst based on platinum and palladium - Google Patents

Abstract

The hydrocracking process involves a hydrorefining stage, using a hydrorefining catalyst, followed by separation of converted from non-converted products, then a hydrocracking stage in which non-converted products are contacted with hydrogen in the presence of an amorphous catalyst. A hydrocracking process for the conversion of a hydrocarbon charge involves (1) a hydrorefining stage in which a charge is contacted with hydrogen in the presence of a hydrorefining catalyst at a temperature T1 and an effluent is recovered containing converted and non-converted products; (2) optionally a separation stage in which the converted products are separated from the non-converted products; (3) hydrocracking stage in which the non-converted products are contacted with hydrogen in the presence of an amorphous catalyst comprising a support, palladium and platinum, at a temperature T2 less than T1, the difference being 5 - 50[deg]C.

Description

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 The present invention relates to the field of the hydrocracking of hydrocarbon feeds in order to produce middle distillates, and more particularly gas oil.

 Hydrocracking of heavy oil cuts is a very important refining process that makes it possible to produce lighter fractions from excessively heavy and unrecognizable heavy feedstocks. In some cases, these processes can also produce a highly purified residue that can provide excellent bases for oils.

 Some hydrocracking processes, often referred to as "once-through" processes, include a preliminary hydrotreatment step with a limited conversion into light fractions and making it possible to transform the nitrogenous and sulfur-containing organic compounds. These types of processes generally do not include an intermediate separation between hydrotreatment and hydrocracking.

 Other hydrocracking processes include a hydrorefining prior stage to convert between 20 and 60% of the feedstock, a separation step to recover unconverted products and a hydrocracking step.

These processes are often referred to as two-step processes.

 International patent application WO 99/47625 describes a process for converting a hydrocarbon feed into a product having a lower average molecular weight. This process comprises a hydrocracking step carried out using a catalyst based on a cracking component and a hydrogenation component, the latter comprising palladium and platinum in a varying molar ratio. between 10: 1 and 1:10.

 The implementation of such a process generally involves the use of a hydrocracking catalyst comprising a zeolite, which makes it possible to produce gases, gasolines and middle distillates with high conversion levels, but this in part. despite poor selectivity in middle distillates.

 A process for the production of middle distillates has been found which makes it possible to reconcile a strong conversion with a high level of selectivity to middle distillates, and this under favorable operating conditions to increase the catalyst cycle time and to produce gas oil and kerosene of excellent quality.

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By gas oil of excellent quality is meant a gas oil having: a sulfur content of less than 50 ppm, preferably less than 30 ppm, and more preferably less than 10 ppm, a cetane number greater than 51, preferably greater than 55, a content of polyaromatic compounds of less than 11% by weight, preferably less than 5% by weight, and more preferably less than
2% by weight, and - an aromatic compound content of less than 15% by weight, preferably less than 10% by weight.

 By kerosene of excellent quality is meant a kerosene whose smoke point is greater than 20 mm, preferably greater than 25 mm.

 The present invention therefore relates to a hydrocracking process for converting a hydrocarbon feedstock, which comprises: a hydrorefining step, in which the feedstock is brought into contact with hydrogen in the presence of a catalyst; hydrorefining, at a temperature T1, and recovering an effluent comprising converted products and unconverted products, - optionally a separation step in which at least a portion of the converted products formed during the hydrorefining stage are separated and a fraction comprising the unconverted products, and - a hydrocracking step, in which the unconverted products (thus possibly at least a part of the fraction containing said products resulting from the separation) are, at least in part, contact with hydrogen, in the presence of an amorphous hydrocracking catalyst comprising a carrier, palladium and platinum, at a temperature T2 less than T1, the difference between T1 and T2 being between 5 and 50 C, preferably between 10 and 40 C, more preferably between 15 and 30 C.

 A wide variety of fillers can be processed by the process of the invention.

Generally these fillers contain at least 20% by volume, and often at least 80% by volume, of compounds having a boiling point above 340 C.

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Preferably, 95% of the compounds present in the feed have a boiling point greater than 340 ° C., and more preferably 95% of the compounds present in the feed have a boiling point greater than 370 ° C.

 The nitrogen content of the hydrocarbon feedstocks treated in the process according to the invention is generally greater than 500 ppm by weight, preferably between 500 and 5000 ppm by weight, more preferably between 700 and 4000 ppm by weight, and so even more preferred between 1000 and 3000 ppm by weight.

 The sulfur content of these hydrocarbon feeds is, for its part, preferably between 0.01 and 5% by weight, more preferably between 0.2 and 4% by weight.

 According to the process of the invention, the feedstock is subjected, in a first reaction zone, to at least one hydrorefining stage, during which it is brought into contact with hydrogen in the presence of a hydrorefining catalyst. .

During this hydrorefining stage, the feedstock generally undergoes hydrodesulfurization, hydrodenitrogenation, as well as a conversion of a portion thereof into conversion products such as gases, gasolines, and middle distillates.

 The hydrorefining catalysts may be chosen from catalysts commonly used in this field.

 The hydrorefining catalyst may preferably comprise a matrix, at least one hydro-dehydrogenating element chosen from the group formed by the elements of group VIB and group VIII of the periodic table.

 The matrix may consist of compounds, used alone or in a mixture, such as alumina, halogenated alumina, silica, silica-alumina, clays (chosen for example from natural clays such as kaolin or bentonite), magnesia, titanium oxide, boron oxide, zirconia, aluminum phosphates, titanium phosphates, zirconium phosphates, coal, aluminates. It is preferred to use matrices containing alumina, in all these forms known to those skilled in the art, and even more preferably aluminas, for example gamma-alumina.

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 The hydro-dehydrogenating element may be selected from the group consisting of Group VIB elements and non-noble group VIII of the Periodic Table. Preferably, the hydro-dehydrogenating element is selected from the group consisting of molybdenum, tungsten, nickel and cobalt. More preferably, the hydro-dehydrogenating element comprises at least one group VIB element and at least one non-noble group VIII element. This hydro-dehydrogenating element may, for example, comprise a combination of at least one Group VIII element (Ni, Co) with at least one Group VIB element (Mo, W).

 Preferably, the hydrorefining catalyst further comprises at least one doping element deposited on said catalyst and selected from the group consisting of phosphorus, boron and silicon. In particular, the hydrorefining catalyst may comprise, as doping elements, boron and / or silicon, with possibly in addition to phosphorus. The boron, silicon and phosphorus contents are generally between 0.1 and 20%, preferably 0.1 and 15%, more preferably between 0.1 and 10%.

 The hydrorefining catalyst may advantageously comprise phosphorus. This compound provides, among other advantages, two main advantages to the hydrorefining catalyst, a first advantage being a greater ease of preparation of said catalyst, in particular for the impregnation of the hydrodehydrogenating element, for example from solutions based on nickel and of molybdenum.

A second advantage provided by this compound is an increase in the activity of hydrogenation of the catalyst.

 The hydrorefining catalyst may furthermore comprise at least one element of group VIIA (preferred chlorine, fluorine), and / or at least one element of group VIIB (preferred manganese), optionally at least one element of group VB (preferred niobium). .

 In a preferred hydrorefining catalyst, the total concentration of metal oxides of groups VIB and VIII is between 5 and 40% by weight, preferably between 7 and 30% by weight, and the weight ratio expressed as metal oxide between metal Group VIII metal (or metals) group VIII is between 20 and 1.25, preferably between 10 and 2. The concentration of

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 phosphorus oxide P2O5 may be less than 15% by weight, preferably less than 10% by weight.

In another hydrorefining catalyst comprising boron and / or silicon, preferably boron and silicon, said catalyst generally comprises, in% by weight relative to the total mass of said catalyst, from 1 to 99%, preferably from 10 to 98% and more preferably from 15 to 95% of at least one matrix, from 3 to 60%, preferably from 3 to 45%, and more preferably from 3 to 45%;
30% of at least one Group VIB metal, optionally from 0 to 30%, preferably from 0 to 25%, and more preferably from 0 to 20% of at least one Group VIII metal, 0.1 to 20%, preferably 0.1 to 15% and, more preferably, 0.1 to 10% boron and / or 0.1 to 20%, preferably 0.1 to 15% and more preferably from 0.1 to 10% silicon, optionally from 0 to 20%, preferably from 0.1 to 15% and, more preferably from 0.1 to 10% of phosphorus, and optionally from 0 to 20%, preferably from 0.1 to 15% and, more preferably from 0.1 to 10%, of at least one element chosen from the group
VIIA, for example fluorine.

In another hydrorefining catalyst, said catalyst comprises: between 1 and 95% by weight (% oxide) of at least one matrix, preferably alumina, between 5 and 40% by weight (% oxide), at least one element of the groups
VIB and VIII non-noble, - between 0 and 20%, preferably between 0.1 and 20% by weight (% oxide) of at least one promoter element selected from phosphorus, boron, silicon, - between 0 and 20% by weight (% oxide) of at least one element of group VIIB (manganese for example), - between 0 and 20% by weight (% oxide) of at least one element of group VIIA (fluorine, chlorine for example) ), and - between 0 and 60% by weight (% oxide) of at least one member of the VB group (niobium for example).

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 In general, hydrorefining catalysts having the following atomic ratios are preferred: a group VIII metal / Group VIB atomic ratio ranging from 0 to 1, a B atomic ratio / Group VIB metals ranging from 0.01 to 3, - a Si / Group VIB atomic ratio ranging from 0.01 to 1.5, - an atomic ratio P / Group VIB metals ranging from 0.01 to 1, and - an atomic ratio elements Group VIIA / Group VIB metals ranging from 0.01 to 2.

 The hydrorefining catalysts that are particularly preferred are the NiMo and / or NiW catalysts on alumina, and also the NiMo and / or NiW catalysts on alumina doped with at least one element included in the group of atoms formed by phosphorus, boron and silicon. and fluorine.

 The hydrorefining catalysts described above are therefore used during the hydrorefining stage, often called the hydrotreatment stage.

 Preferably, the hydrorefining catalyst is previously subjected to a sulfurization treatment for converting, at least in part, the metal species to sulfide, before contacting with the feedstock to be treated. This activation treatment by sulfurization is well known to those skilled in the art and can be performed by any method already described in the literature either in-situ, that is to say in the reactor, or ex-situ.

 Preferably, the operating conditions used during the hydrorefining stage may be defined as follows: a temperature T1 ranging from 330 to 420 ° C., preferably from 350 to 410 ° C., more preferably from 360 ° to 400 ° C., and even more preferably from 370 to 390 ° C; a pressure greater than 7.5 MPa, preferably greater than 8. 2 MPa, more preferably greater than 9.0 MPa, and even more preferably greater than 11.0 MPa and less than 20 MPa; a space velocity ranging from 0.1 to 6 h -1, preferably from 0.2 to 3 h -1; a quantity of hydrogen introduced with a volume ratio in liters of hydrogen per liter of hydrocarbons ranging from 100 to 2000 l / l.

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 During the hydrorefining stage of the process of the invention, the contents of organic nitrogen compounds, organic sulfur compounds and condensed polycyclic aromatic hydrocarbons are generally reduced. A large part of the organic nitrogenous and sulfurous products of the feed is transformed into H2S and NH3.

 The operating conditions of the hydrorefining stage are preferably set so that the organic nitrogen content of the feed resulting from this hydrorefining is less than 10 ppm by weight, preferably less than 5 ppm.

 Preferably, the operating conditions of the hydrorefining stage are set so as to obtain a level of conversion of the feedstock into compounds having a boiling point of less than 340.degree. C., better still less than 370.degree. 50%, preferably between 20 and 40%.

 According to the process of the present invention, the effluent recovered during the hydrorefining stage is subjected to a separation stage in which at least a portion of the converted products formed during the hydrorefining stage are separated and a fraction including unconverted products.

 The effluent of this hydrorefining step may be sent to a separation means, such as for example a separator flask, in order to remove the ammonia and hydrogen sulphide produced during the hydrorefining step. The hydrocarbon effluent resulting from this separation may undergo atmospheric distillation. This distillation can be supplemented, in some cases, by vacuum distillation. The purpose of the distillation is to achieve the separation between the converted products, that is to say generally having boiling points below 340 ° C., preferably below 370 ° C., and a fraction, generally liquid, comprising unconverted products. .

 It is advantageous to distil at atmospheric pressure to obtain several converted products, such as, for example, gasolines, kerosene, gas oil, as well as unconverted products having an initial boiling point greater than 340 ° C., or even greater than 370 ° C. C.

 According to the process of the present invention, the fraction comprising unconverted products is, at least in part, subjected to a hydrocracking step.

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 Preferably, the fraction subjected to a hydrocracking step consists essentially of products having a boiling point greater than 340 ° C., preferably greater than 370 ° C.

 This fraction subjected to the hydrocracking stage generally has very low levels of organic sulfur, organic nitrogen, hydrogen sulphide and ammonia. By organic sulfur and organic nitrogen is meant sulfur and nitrogen included in organic compounds.

 The organic nitrogen content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is preferably less than 10 ppm by weight, more preferably less than 5 ppm by weight.

 The organic sulfur content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is preferably less than 100 ppm by weight, more preferably less than 20 ppm by weight.

 The H2S content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is preferably less than 100 ppm by weight, more preferably less than 10 ppm by weight, and even more so. preferred less than 5 ppm by weight.

 The NH 3 content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is preferably less than 100 ppm by weight, more preferably less than 10 ppm by weight and even more preferably less than 5 ppm by weight.

 According to the process of the invention, the hydrocracking step is carried out by placing it in contact with hydrogen in the presence of a hydrocracking catalyst.

 The hydrogen used during the hydrocracking stage generally has a hydrogen sulphide content of less than 100 ppm, preferably less than 10 ppm, more preferably less than 5 ppm and an ammonia content of less than 50 ppm. preferably less than 10 ppm, more preferably less than 5 ppm.

 According to the process of the invention, the hydrocracking catalyst has an amorphous or non-zeolitic character. The hydrocracking catalyst generally comprises at least one amorphous acidic support and at least one noble-metal hydride-dehydrogenating function.

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 The supports generally have large areas that can range from 150 to 800 m2g-1 and have a superficial acidity. They may be chosen from halogenated alumina (in particular chlorinated or fluorinated alumina), combinations of boron and aluminum oxides, combinations of titanium oxide, silicon oxide and aluminum oxide, zirconium oxide combinations, aluminum and silicon, amorphous silica-aluminas, halogenated silica-aluminas (chlorinated or fluorinated in particular). These oxides or combinations of amorphous oxides can be obtained by all the synthetic methods known to those skilled in the art. Preferably, the support of the hydrocracking catalyst is an amorphous silica-alumina.

 The support may consist of pure silica-alumina or result from mixing, with said silica-alumina, a binder such as silica (SiO 2), alumina (Al 2 O 3), clays, titanium oxide (TiO 2) ), boron oxide (B203) and zirconia (ZrO2) and any mixture with the binders mentioned above. The preferred binders are silica and alumina and even more preferably alumina in all these forms known to those skilled in the art, for example gamma-alumina. The weight content of binder in the catalyst support can be between 0 and 40% by weight, preferably between 1 and 40% by weight, and more preferably between 5% and 20% by weight. As a result, the weight content of silica-alumina is generally between 60 - 100% by weight. However, catalysts whose support consists solely of silica-alumina without any binder are preferred.

 The support may be prepared by shaping the silica-alumina in the presence or absence of binder by any technique known to those skilled in the art.

The shaping can be carried out for example by extrusion, pelletizing, by the method of coagulation in drop (oil-drop), by rotating plate granulation or by any other method well known to those skilled in the art. At least one calcination can be carried out after any one of the steps of the preparation, it is usually carried out in air at a temperature of at least 150 ° C., preferably at least 300 ° C.

 The catalyst supports may have a number of features.

 Among the characteristics used in the following, the specific surface area B.E.T. is determined by nitrogen adsorption according to the ASTM D standard.

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 3663-78 established from the BRUNAUER-EMMETT-TELLER method described in the journal The Journal of American Society ", 60, 309, (1938).

 Concerning volume measurements, they are generally made by mercury porosimeter intrusion according to ASTM standard D4284-83 at a maximum pressure of 4000 bar, using a surface tension of 484 dyne / cm and a contact angle for the silica supports. amorphous alumina of 140. The average mercury diameter, Dmoyen, is defined as a diameter such that all pores less than this diameter constitute 50% of the pore volume (VHg), in a range of between 36 Å and 1000. In order to obtain a better precision, the mercury volume value in ml / g given in the following text corresponds to the value of the total mercury volume in ml / g measured on the sample minus the mercury volume value in ml / g. measured on the same sample for a pressure corresponding to 30 psi (about 2 bar). In order to better characterize the porous distribution, the following porous distribution criteria are defined as mercury: the volume V1 corresponds to the volume contained in the pores, the diameter of which is less than the mean diameter minus 30 Å. The volume V 2 corresponds to the volume contained in the pores with a diameter greater than the average diameter less than 30 Å and less than the average diameter plus 30 Å. The volume V3 corresponds to the volume contained in the pores with a diameter greater than the average diameter plus 30 Å. The volume V4 corresponds to the volume contained in the pores whose diameter is less than the average diameter minus 15 Å.

The volume V5 corresponds to the volume contained in the pores with a diameter greater than the average diameter less than and less than the average diameter plus 15 Å. The volume V6 corresponds to the volume contained in the pores of diameter greater than the average diameter plus 15 Å.

 In what follows, the porous distribution measured by nitrogen adsorption was determined by the Barrett-Joyner-Halenda model (BJH). The nitrogen desorption adsorption isotherm according to the BJH model is described in the periodical "The Journal of American Society", 73, 373, (1951) written by E.P.Barrett, L.G.Joyner and P.P.Halenda.

In the following description of the invention, the term nitrogen adsorption volume, the volume measured for P / PO = 0. 99, pressure for which it is assumed that nitrogen has filled all the pores. The average nitrogen desorption diameter is defined as being a diameter such that all the pores smaller than this diameter constitute 50% of the

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 porous volume (Vp) measured on the desorption branch of the nitrogen isotherm. By surface adsorption is meant the area measured on the branch of the adsorption isotherm. For example, see the article by A. Lecloux "Memoirs Royal Society of Sciences of Liège, 6th series, Volume I, fasc 4, pp.169-209 (1971)".

 The sodium content was measured by atomic absorption spectrometry.

 In the following description, the X-ray analysis is carried out on powder with a Philips PW 1830 diffractometer operating in reflection and equipped with a rear monochromator using the radiation CoKalpha (AKai = 1.7890, ÀKa2 = 1.793, ratio of intensity K [alpha] 1 / Ka2 = 0.5). For the X-ray diffraction pattern of gamma-alumina, reference is made to the ICDD database, sheet 10-0425. In particular, the 2 most intense peaks are located at a position corresponding to a d between 1.39 and 1.40 and a d between 1.97 and 2.00. We call d the inter-sectional distance that is deduced from the angular position using the Bragg relation (2 d (hkl) * sin (#) = n * A). By gamma-alumina, is meant in the following text among others for example an alumina included in the group consisting of cubic gamma, pseudo-cubic gamma, gamma tetragonal, gamma or poorly crystallized gamma gamma gamma gamma surface gamma, low gamma gamma from large boehmite, gamma from crystallized boehmite, gamma from boehmite poorly or poorly crystallized, gamma from a mixture of crystallized boehmite and an amorphous gel, gamma from an amorphous gel, gamma evolution to delta. For the positions of the diffraction peaks of eta, delta and theta aluminas, reference may be made to the article by BC Lippens, JJ Steggerda, in Physical and Chemical Aspects of Adsorbents and Catalysts, EG Linsen (Ed.), Academy Press, London. 1970, p.171-211.

 Finally, in the following description, the RMS MAS analyzes are carried out on a Brüker MSL 400 type spectrometer, in a 4 mm probe. The rotation speed of the samples is of the order of 11 kHz. Potentially, the NMR of aluminum makes it possible to distinguish three types of aluminum whose chemical shifts are reported hereafter: - between 100 and 40 ppm, aluminum of type tetra-coordinated, noted AlIV,

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 between 40 and 20 ppm, aluminum of the penta-coordinated type, denoted Alv, between 20 and 100 ppm, aluminum of the hexa-coordinated type, denoted AlVI.

 The aluminum atom is a quadrupole nucleus. Under certain analysis conditions (low radio frequency fields: 30 kHz, low pulse angle: # / 2 and water saturated sample), the Magic Angle Rotation NMR (MAS) technique is a quantitative technique. The decomposition of the MAS NMR spectra gives direct access to the quantity of the different species. The spectrum is wedged in chemical displacement with respect to a 1 M solution of aluminum nitrate. The aluminum signal is at zero ppm. We chose to integrate the signals between 100 and 20 ppm for the AlIV and AIV, which corresponds to the area 1, and between 20 and -100 ppm for AlVI, which corresponds to the area 2. In the According to the following description of the invention, the proportion of octahedral AlVI is the ratio: 2 / (area 1 + area 2).

 According to a first mode of the present invention, the support of the hydrocracking catalyst is a non-zeolitic support based on silica-alumina (that is to say comprising silica and alumina) which has the following characteristics: a mass content silica (SiO2) greater than 5% by weight and less than or equal to 95% by weight, preferably between 10 and 80% by 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% by weight, preferably a content of cationic impurities 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.

preferably an anionic impurities content of less than 1% by weight, preferably less than 0.5% by weight and even more preferably less than 0.1% by weight.

 a mean pore diameter, measured by mercury porosimetry, of between 20 and 140 Å, preferably of between 40 and 120 Å and even more preferably between 50 and 100,

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preferably a ratio between the volume V 2, measured by mercury porosimetry, between Dmoyen-30 and Dmoyen + 30 A, on the total pore volume also measured by mercury porosimetry greater than 0.6, preferably greater than 0.7 and even more preferably greater than
0.8.

preferably a volume V3 included in the pores with diameters larger than
Dmoyen + 30, measured by mercury porosimetry, less than 0.1 ml / g, preferably less than 0.06 ml / g and even more preferably less than 0.04 ml / g.

- preferably a ratio between the volume V5 between Dmoyen - 15 and Dmoyen + 15 measured by mercury porosimetry, and the volume V2 between Dmoyen - 30 and Dmoyen + 30, measured by mercury porosimetry, greater than 0.6, more preferably greater than 0.7 and even more preferably greater than 0.8. preferably a volume V6 included in the pores of diameters larger than
Dmoyen + 15 A, measured by mercury porosimetry, less than 0.2 ml / g, preferably less than 0.1 ml / g and even more preferably less than 0.05 ml / g.

a total pore volume, measured by mercury porosimetry, of between 0.1 ml / g and 0.6 ml / g, preferably between 0.20 and 0.50 ml / g and even more preferably higher at 0.20 ml / g, a total pore volume, measured by nitrogen porosimetry, of between 0.1 ml / g and
0.6 ml / g, preferably between 0.20 and 0.50 ml / g, a BET specific surface area of between 100 and 550 m 2 / g, preferably between 150 and 500 m 2 / g, preferably between adsorption surface such that the ratio between the adsorption surface and the BET surface is greater than 0.5, preferably greater than 0.65 and more preferably greater than 0.8.

a porous volume, measured by mercury porosimetry, comprised in pores with a diameter greater than 140 Å of less than 0.1 ml / g, preferably less than 0.05 ml / g and even more preferably less than 0, 03 ml / g.

a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 160 less than 0.1 ml / g, preferably less than 0.05 ml / g and even more preferably less than 0.025 ml / g .

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 a pore volume, measured by mercury porosimetry, contained in pores with a diameter greater than 200 Å of less than 0.1 ml / g, preferably less than 0.05 ml / g and even more preferably less than 0.025 ml; / g.

a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 500 less than 0.01 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 the rho, chi, kappa, eta, gamma, theta and delta aluminas and, preferably, characterized by it contains at least the main characteristic lines of at least one of the transition aluminas included in the group consisting of gamma, eta, theta and delta alumina, and more preferably characterized in that it contains at least minus the main characteristic lines of gamma alumina and eta, and even more preferably characterized in that it contains the peaks at a d between 1.39 to 1.40 and at d between 1.97 to 2.00 to.

 The MAS NMR spectra of the solid of 27A / of such a support show two distinct peak mass. A first type of aluminum whose maximum resonates around 10 ppm ranges between -100 and 20 ppm. The position of the maximum suggests that these species are essentially of the AlVI (octahedral) type. A second type of minority aluminum whose maximum resonates around 60 ppm ranges between 20 and 110 ppm. This massif can be broken down into at least two species. The predominant species of this massif corresponds to the atoms of Allv (tetrahedral). For the supports of this embodiment of the invention, advantageously, the proportion of octahedra Alvi is greater than 50%, preferably greater than 60%, and even more preferably greater than 70%.

 The support may comprise at least two silico-aluminic zones, said zones having Si / Al ratios lower or higher than the overall Si / Al ratio determined by X-ray fluorescence. Thus, a support having an Si / Al ratio equal to 0.5 comprises for example two silico-aluminic zones, one of the zones has a ratio Si / Al determined by TEM of less than 0.5 and the other zone has a ratio Si / Al determined by MET of between 0.5 and 2.5. .

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 The support may comprise a single silico-aluminic zone, said zone having a Si / Al ratio equal to the overall Si / Al ratio determined by X-ray fluorescence and less than 2.3.

More specifically, this first embodiment of the invention relates to a non-zeolitic support based on silica-alumina containing an amount greater than 5% by weight and less than or equal to 95% by weight of silica (SiO 2) characterized by: - a diameter porous medium, measured by mercury porosimetry, between 20 and 140, a total pore volume, measured by mercury porosimetry, of between 0.1 ml / g and 0.6 ml / g, a total pore volume, measured by nitrogen porosimetry, between 0.1 ml / g and
0.6 ml / g, a BET specific surface area of between 100 and 550 m 2 / g, a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 140 Å 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; less than 0.1 ml / g; a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 500 less than 0.01 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 the rho, chi, eta, gamma, kappa, theta and delta aluminas.

According to a second mode of the present invention, the support of the hydrocracking catalyst comprises at least one silica-alumina, said silica-alumina having the following characteristics: a silica SiO 2 content of between 10 and 60%, preferably between 20 and 60% and even more preferably between 30 and
50% by weight, - an Na content of less than 300 ppm by weight and, preferably, less than
200 ppm weight,

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a total pore volume of between 0.5 and 1.2 ml / g measured by mercury porosimetry, a specific surface area greater than 200 m 2 / g and preferably greater than 250 m 2 / g, and a porosity defined as follows: i) a volume of mesopores with a diameter between 40 and
150, and whose mean diameter varies between 80 and 120 representing between 30 and 80% of the total pore volume previously defined and, preferably between 40 and 70%, ii) a volume of macropores, whose diameter is greater than 500 and, preferably between 1000 Å and 10000 Å represents between 20 and 80% of the total pore volume, preferably between 30 and
60% of the total pore volume and, more preferably, at least
35% of the total pore volume.

 According to the present invention, the amorphous hydrocracking catalyst comprises palladium and platinum. These two compounds are part of the hydro-dehydrogenating element of the hydrocracking catalyst.

 The hydro-dehydrogenating element may comprise, in addition to palladium and platinum, one or more noble metals of group VIII of the periodic table of elements, or a combination of at least one metal of group VIB of the periodic table and at least one less a Group VIII metal.

 The hydrocracking catalyst may comprise, in% by weight relative to the total weight of the catalyst, from 0.2 to 8% by weight, preferably from 0.3 to 5% by weight, more preferably from 0.4% by weight. at 2% by weight of noble metals of group VIII.

 The hydrocracking catalyst may be preliminarily subjected to a reduction treatment for converting, at least in part, the noble metal oxides into reduced noble metals. One of the preferred methods for carrying out the reduction of the catalyst is a treatment in hydrogen at a temperature of between 150 and 650 ° C. and at a total pressure of between 0.1 and 20 MPa.

It should also be noted that any ex-situ reduction method may be suitable.

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 By way of example, a reduction may comprise a maintenance at a temperature of 150 ° C. for 2 hours, followed by a rise in temperature to 350 ° C. at a rate of 1 ° C. per minute and then a hold at 350 ° C. for 2 hours. . During this reduction treatment, the hydrogen flow rate may be 1000 liters of hydrogen per liter of catalyst.

 According to an essential characteristic of the process of the invention, the hydrocracking step is carried out at a temperature T2 lower than the water-treatment temperature T1, the difference between T1 and T2 being between 5 and 50 ° C. preferably between 10 and 40 C, more preferably between 15 and 30 C.

 The operating conditions used during the hydrocracking step of the process according to the invention may be: a temperature T2 greater than 200 ° C., preferably between 250 ° and 420 ° C., more preferably between 300 ° and 400 ° C., even more preferably between 330 and 380 C; a pressure greater than 7.5, preferably greater than 8. 2 MPa, more preferably greater than 9.0 MPa, and even more preferably greater than 11.0 MPa and less than 20 MPa; a space velocity of between 0.1 and 20 h -1, preferably between 0.1 and 6 h -1, more preferably between 0.2 and 3 h -1; - A quantity of hydrogen introduced such that the volume ratio in liters of hydrogen per liter of hydrocarbon is between 80 and 50001/1, preferably between 100 and 2000 l / l.

 These operating conditions used during the hydrocracking step can be set so as to achieve a pass conversion, in products having a boiling point below 340 C (and better still below 370 C) greater than 30% by weight. preferably between 40 and 95% by weight.

 The effluent recovered during the hydrocracking step is generally subjected to a so-called final separation step, so as to separate the gases, such as ammonia, hydrogen sulphide, hydrogen, as well as the other light gases from the effluent.

 Following this final separation step, atmospheric distillation can be implemented. In some cases, this atmospheric distillation is

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 supplemented by vacuum distillation. The distillation is intended to achieve separation between the converted products, that is to say generally having boiling points below 340 C (and better still below 370 C) and an unconverted liquid fraction.

 It is advantageously possible to distil at atmospheric pressure to obtain several converted fractions, such as, for example, gasolines, kerosene, gas oil and an unconverted liquid fraction having an initial boiling point greater than 340 ° C. or even greater than 370 ° C.

 To improve the final separation, vacuum distillation can be added.

This will be the case for example to distill the diesel with better efficiency.

 The unconverted liquid fraction may be wholly or partially injected into the hydrocracking reactor for conversion.

 Advantageously, the final separation is carried out with the means of the separation step carried out between the hydrorefining and hydrocracking stages, when these comprise an atmospheric distillation and optionally a vacuum distillation.

 This method makes it possible to obtain levels of conversion of the feedstock into products whose boiling point is less than 370.degree. C., greater than 70% and preferably greater than 80%. This process also makes it possible to obtain high selectivities in middle distillates and more particularly in gas oil.

 The gas oil and kerosene obtained have excellent qualities, ie a high cetane number and a low sulfur content.

 The following examples illustrate the present invention without, however, limiting its scope.

Example 1 Preparation of a Hydrocracking Catalyst According to the Invention (C1)
The preparation of the support S1 according to the invention is described below.

 The silica-alumina gels are prepared by mixing sodium silicate and water, by sending this mixture to an ion exchange resin. A solution of aluminum hexahydrate in decationized silica sol water is added. In order to obtain a gel, ammonia is added, the precipitate is then filtered off and

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 perform a wash with concentrated water and ammonia solution until the conductivity of the wash water is constant. The gel resulting from this step is mixed with Pural boehmite powder so that the final composition of the mixed support in anhydrous product is, at this stage of the synthesis, equal to 60% Al 2 O 3 - 40% SiO 2. This suspension is passed through a colloid mill in the presence of nitric acid. The added nitric acid content is adjusted so that the output percentage of the nitric acid mill is 8% based on the mass of solid mixed oxide. This mixture is then filtered in order to reduce the amount of water in the mixed cake. Then, the cake is kneaded in the presence of 10% nitric acid and then extruded. Mixing is done on a Z-arm kneader.

The extrusion is carried out by passing the paste through a die provided with orifices 1.4 mm in diameter. The extrudates thus obtained are dried at 150 ° C., then calcined at 550 ° C. and then calcined at 700 ° C. in the presence of steam.

The characteristics of the support S1 are the following: a composition of the silica-alumina support of 60.7% Al.sub.2 O.sub.3 and 39.3%
SiO2; a BET surface area of 258 m 2 / g; a total pore volume, measured by nitrogen adsorption, of 0.47 ml / g; a mean pore diameter, measured by mercury porosimetry, of 69; a ratio between the volume V2, measured by mercury porosimetry, of between Dmoyen - 30 and Dmoyen +30 on the total mercury volume of 0.89; a volume V3, measured by mercury porosimetry, included in pores with diameters greater than Dmoyen + 30 A of 0.032 ml / g; a volume V6, measured by mercury porosimetry, included in pores with diameters greater than Dmoyen + of 0.041 ml / g; a ratio between the adsorption surface and the BET surface of 0.83; a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 140 of 0.012 ml / g; a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 160 of 0.0082 ml / g;

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 a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 200 of 0.0063 ml / g; a porous volume, measured by mercury porosimetry, included in pores with a diameter greater than 500 of 0.001 ml / g; an X-ray diffraction diagram containing at least the main gamma characteristic lines and the peaks at a d between 1.39 and 1.40 Å and at a d ranging from 1.97 to 2.00 Å, the diffraction pattern X also containing the main lines characteristic of gamma alumina and in particular the peaks at a d between 1.39 to 1.40 and a d between 1.97 to 2.00; an atomic sodium content of 200 +/- 20 ppm; an atomic sulfur content of 800 ppm; and MAS NMR spectra of the 27Al solid of the catalysts showing two distinct peak mass, a first type of aluminum whose maximum resonates at 10 ppm ranging between 100 and 20 ppm, the position of the maximum suggesting that these species are essentially AlVI type (octahedral), a second type of minority aluminum whose maximum resonates around 60 ppm and which extends between 20 and 100 ppm, this massif being able to be decomposed into at least two species, the predominant species of this mass correspond to the atoms of Allv (tetrahedral), the proportion of octahedral AlVI being 70%.

The catalyst contains a single silico-aluminum zone with a Si / Al ratio determined by TEM microprobe of 0.63.

 The catalyst C1 is obtained by dry impregnation of the support S1 with an aqueous solution containing platinum and palladium salts. The platinum salt is hexachloroplatinic acid H2PtCl6 * 6H2O and the palladium salt is palladium nitrate Pd (NO3) 2. After maturation at room temperature in an atmosphere saturated with water, the impregnated extrudates are dried at 120 ° C. overnight and then calcined at 500 ° C. under dry air. The final Pt content is 0.5% by weight. The final Pd content is 1.0% by weight.

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Example 2 Preparation of a Hydrocracking Catalyst According to the Invention (C2)
Support S2 is an amorphous silica-alumina having a chemical composition of 40% by weight SiO 2 and 60% by weight Al 2 O 3. Its Si / Al molar ratio is 0.56. Its Na content is of the order of 100-120 ppm by weight. It is in the form of cylindrical extrusions with a diameter of 1.7 mm. Its specific surface is 320m2 / g.

Its total pore volume, measured by mercury porosimetry, is 0.83 ml / g. The pore distribution is bimodal. In the field of mesopores we observe a broad peak between 40 and 150 Å with a maximum in dV / dD around 70. On the support, macropores having a size greater than 500 Å representing approximately 40% of the total pore volume.

 The catalyst C2 is obtained by dry impregnation of the support S2 with an aqueous solution containing platinum and palladium salts. The platinum salt is hexachloroplatinic acid H 2 PtCl 6 6H 2 O and the palladium salt is palladium nitrate Pd (NO 3) 2. After maturation at room temperature in an atmosphere saturated with water, the impregnated extrudates are dried at 120 ° C. overnight and then calcined at 500 ° C. under dry air. The final Pt content is 0.5% wt. The final Pd content is 1.0% wt.

Example 3 Evaluation of catalysts C1 and C2 under conditions in accordance with the invention.

 A vacuum distillate is subjected to a hydrorefining step on a Procatalyse-marketed catalyst HR448, based on nickel (3.3% by weight), on molybdenum (16.5% by weight) supported on alumina, in the presence of hydrogen, at a temperature of 385 C and at a hourly space velocity of 0.50 h-1. During this hydrorefining step, the conversion into products whose boiling point is less than 370 C is about 35% by weight.

 The effluent produced during this hydrorefining step is subjected to a separation step making it possible to recover a 370 C + fraction which is subjected to a hydrocracking step.

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The physico-chemical characteristics of the fraction 370+ subjected to the hydrocracking step are described in Table 1:
Table 1: Characteristics of the fraction subjected to the hydrocracking step.

<Tb>
<Tb>

Density <SEP> (20/4) <SEP> 0.854
<tb> Sulfur <SEP> Organic <SEP> (ppm <SEP> Weight) ~~~~~~ 8 ~~~~~
<tb> Organic <SEP> Nitrogen <SEP> (ppm <SEP> Weight) <SEP> 2 <SEP>
<tb> H2S <SEP> (ppm <SEP> weight) <SEP> 5 <SEP>
<tb> NH3 <SEP> (ppm <SEP> weight) <SEP> 4 <SEP>
<tb> Simulated Distillation <SEP>
<tb> Initial <SEP> Point <SEP> 325 C <SEP>
<tb> Point <SEP> 5% <SEP> 366 C <SEP>
<tb> Point <SEP> 10% <SEP> 384 C <SEP>
<tb> Point <SEP> 50% <SEP> 449 C <SEP>
<tb> Point <SEP> 90% <SEP> 527 C <SEP>
<tb> Point <SEP> Final <SEP> 591 <SEP> C
<Tb>

The fraction subjected to the hydrocracking step is introduced into a hydrocracking test unit simulating the operation of the second step of a 2-step hydrocracking process which comprises a fixed bed reactor with upward circulation of the hydrocracking unit. charge ("up flow"), into which 50 ml of catalyst is introduced.

 Catalysts C1 and C2 are reduced beforehand to 350 ° C. for 2 hours under a hydrogen flow rate of 50 hours, under a total pressure of 14 MPa. At the beginning of this reduction step, the temperature is increased to 350 ° C. with a temperature rise rate of 1 ° C. per minute.

 Once the reduction is completed, the fraction described in Table 1 is then hydrocracked. The operating conditions of this test simulating the second step of the hydrocracking process in two steps are as follows:

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Table 2: Operating conditions

<Tb>
<tb> Total <SEP> pressure <SEP> 14 <SEP> Mpa
<tb> Catalyst <SEP> 50 <SEP> ml
<tb> temperature <SEP> 365 <SEP> - <SEP> 370 <SEP> - <SEP> 375 C
<tb> flow rate <SEP> hydrogen <SEP> 50 <SEP> l / h
<tb> flow rate <SEP> of <SEP> load ~~~~~~~~~~~ 50 <SEP> ml / hr
<Tb>

The catalytic performances are expressed by the net conversion to products having a boiling point lower than 370 C, by the gross selectivity in middle distillate (150-370 C cut) and by the ratio between the fuel yield and the kerosene yield. in the middle distillate fraction. They are expressed from the results of simulated distillation. These performances are determined at the different temperature levels of the test. For each temperature level, the performances are measured on the catalyst after a period of stabilization, generally at least 72 hours, has been respected.

The net CN conversion is given by the following formula:
CN 370 '= [(% 370' effluents) (% 370-feedstock) Il [[100 - (% 370'load)] with:% 370-effluents: mass content of compounds with boiling points below 370 C in the effluents, and (% 370'charge: mass content of compounds having boiling points below 370 C in the feedstock.

The crude selectivity of middle distillate SB is obtained as follows:
SB middle distillates = [(Fraction (150 C - 370 C) effluents)] / [(% 370 C-effluents)]
The ratio between the fuel yield and the kerosene yield (Go. / Ker. Ratio) in the average distillate fraction corresponds to the ratio between the yield of the fraction (250 C - 370 C) of the effluent and the yield of the fraction (150 C - 250 C) of the effluent.

 The catalytic performances obtained on the catalysts C1 and C2 are given in Table 3 below.

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Table 3: Catalytic Results Obtained on Catalyst C1 and C2

<Tb>
<Tb>

Catalyst <SEP> Temperature <SEP> CN <SEP> 370 C- <SEP> SB <SEP> Report
<tb> (C) <SEP> (% <SEP> Weight) <SEP> Distillate <SEP> Medium <SEP> Go./Ker.
<Tb>

(% <SEP> weight) <SEP> (% weight <SEP> /
<tb> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~% weight)
<tb> C1 <SEP> 360 <SEP> 60 <SEP> 77 <SEP> 1,4
<tb> C1 <SEP> 370 <SEP> 80 <SEP> 71 <SEP> 1.0
<tb> C1 <SEP> 375 <SEP> 90 <SEP> 68 <SEP> 0.7
<tb> C2 <SEP> 360 <SEP> 59 <SEP> 75 <SEP> 1,3
<tb> C2 <SEP> 370 <SEP> 78 <SEP> 70 <SEP> 0.9
<tb> C2 <SEP> 375 <SEP> 89 <SEP> 67 <SEP> 0.6
<Tb>

The amorphous acid hydrocracking catalysts C1 and C2 employed in the hydrocracking stage make it possible to obtain high conversion levels of products having a boiling point of less than 370 ° C., and high selectivities for middle distillates. at temperature levels such that the temperature of the hydrocracking step is lower than the temperature of the hydrorefining step by 10 to 25 ° C., the hydrorefining step being carried out at 385 ° C. in this step. example.

 The effluent from the hydrocracking is distilled so as to recover the kerosene fraction (compounds having boiling points greater than 150 ° C. and less than 250 ° C.) and the gas oil fraction (compounds having boiling points greater than 150 ° C.). 250 C and less than 370 C). The kerosene and gas oil fractions are then analyzed. The characteristics of these cuts are summarized in Table 4 for kerosene and in Table 5 for gas oil.

Table 4: characteristics of the kerosene fraction obtained

<Tb>
<tb> Catalyst <SEP> Point <SEP> of <SEP> Smoke <SEP> (mm)
<tb> C1 <SEP> 27
<tb> C2 <SEP> 26
<Tb>

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Table 5: Characteristics of the gas oil fraction obtained

<Tb>
<tb> Catalyst <SEP> Content <SEP> in <SEP> Cetane <SEP> engine <SEP> Content <SEP> in <SEP> Content <SEP> in <SEP>
<tb> sulfur <SEP> aromatic <SEP> polyaromatic
<tb> (ppm <SEP> weight) <SEP> (% <SEP> weight) <SEP> s <SEP> (% <SEP> weight)
<tb> C1 <SEP> 7 <SEP> 57 <SEP> 9.1 <SEP> 1.7
<tb> C2 <SEP> 8 <SEP> 56 <SEP> 9.3 <SEP> 1.9
<Tb>

The amorphous acid hydrocracking catalysts C1 and C2 of the PtPd / silicalumin type, in accordance with the invention, used in the second hydrocracking step of the hydrocracking process according to the invention make it possible to obtain kerosene and gas oil fractions. excellent qualities.

Example 5 Evaluation of Catalyst C1 Under Conditions Not in Accordance with the Invention
Catalyst C1 is evaluated under hydrocracking conditions.

 The fraction subjected to hydrocracking is identical to that described in Example 3, the characteristics of which are reported in Table 1.

 Before injection of this fraction, the catalyst C1 undergoes a reduction treatment under operating conditions identical to the operating conditions of the reduction treatment described in Example 3.

 Once the reduction is achieved, the fraction described in Table 1 can be processed. The operating conditions of this test, which are not in accordance with the invention, are described in Table 8. The temperature of the hydrocracking step is equal to the temperature of the hydrorefining stage, ie 385 C.

Table 8: Operating conditions

<Tb>
<tb> Total <SEP> pressure <SEP> 14 <SEP> Mpa
<tb> Catalyst <SEP> 50 <SEP> ml
<tb> temperature <SEP> 385 C
<tb> flow rate <SEP> hydrogen <SEP> 50 <SEP> l / h
<tb> flow rate <SEP> of <SEP> load ~~~~~~~~~~~~ 50 <SEP> ml / hr
<Tb>

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The catalytic performances obtained on the catalyst C1 under these operating conditions are given in Table 9 below.

Table 9 Catalyst results obtained on the catalyst C1.

<Tb>
<Tb>

Catalyst <SEP> Temperature <SEP> CN <SEP> 370 C- <SEP> SB <SEP> Report
<tb> (C) <SEP> (% <SEP> Weight) <SEP> Distillate <SEP> Medium <SEP> Go./Ker.
<Tb>

(% <SEP> weight) <SEP> (% weight <SEP> /
<tb>% weight)
<tb> C1 <SEP> 385 <SEP> 100 <SEP> 49 <SEP> 0.6
<Tb>

The conversion to products having a boiling point below 370 C is total, but the selectivity to middle distillates (150-370 C) is very low.

Claims (11)

 1. hydrocracking process for the conversion of a hydrocarbon feedstock, characterized in that it comprises: - a hydrorefining step, wherein the charge is brought into contact with hydrogen in the presence of a hydrorefining catalyst, at a temperature T1, and recovering an effluent comprising converted products and unconverted products, - optionally a separation step in which at least a portion of the converted products formed during step d are separated hydrorefining and a fraction comprising the unconverted products, and - a hydrocracking step, wherein the unconverted products are at least partly contacted with hydrogen in the presence of a hydrocracking catalyst amorphous mixture comprising a carrier, palladium and platinum, at a temperature T2 less than T1, the difference between T1 and T2 being between 5 and 50 C. 2. Method according to claim wherein the difference between T1 and T2 is between 15 and 30 C. 3. Method according to any one of claims 1 and 2, characterized in that the hydrorefining catalyst further comprises at least one doping element deposited on said catalyst and selected from the group consisting of phosphorus, boron and silicon. 4. Method according to any one of claims 1 to 3, characterized in that the hydrorefining step is carried out at a temperature T1 ranging from 330 to 420 C. 5. Method according to any one of claims 1 to 4, characterized in that the fraction subjected to a hydrocracking step consists essentially of products having a boiling point greater than 340 C. <Desc / Clms Page number 28> 6. Method according to any one of claims 1 to 5, characterized in that the organic nitrogen content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is less than 10 ppm by weight and the organic sulfur content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is less than 100 ppm by weight. 7. Method according to any one of claims 1 to 6, characterized in that the H2S content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is less than 100 ppm by weight and the NH3 content of the portion of the fraction comprising the unconverted products subjected to the hydrocracking step is less than 100 ppm by weight. 8. Process according to any one of claims 1 to 7, characterized in that the support of the hydrocracking catalyst is an amorphous silica-alumina. 9. The method of claim 8 wherein the support of the hydrocracking catalyst comprises: - an amount greater than 5% by weight and less than or equal to 95% by weight of silica (SiO 2) - a mean pore diameter, measured by mercury porosimetry , between 20 and 140, a total pore volume, measured by mercury porosimetry, of between 0.1 ml / g and 0.6 ml / g, a total pore volume, measured by nitrogen porosimetry, of between 0, 1 ml / g and 0.6 ml / g, a BET specific surface area between 100 and 550 m 2 / g, a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 140 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 Å; less than 0.1 ml / g; a pore volume, measured by mercury porosimetry, included in pores with a diameter greater than 500 less than 0.01 ml / g. <Desc / Clms Page number 29> 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 the rho, chi, eta, gamma, kappa, theta and delta aluminas. 10. The method of claim 8 wherein the support of the hydrocracking catalyst has the following characteristics: a SiO 2 silica content of between 10 and 60%, an Na content of less than 300 ppm by weight, a porous volume. total between 0.5 and 1.2 ml / g measured by mercury porosimetry, - a specific surface area greater than 200 m2 / g, and - a porosity defined as follows: iii) a volume of mesopores whose diameter is between 40Â and 150, and whose average diameter varies between 80 and 120 representing between 30 and 80% of the total pore volume previously defined, iv) a volume of macropores, whose diameter is greater than 500 Å and preferably between 1000 Å and 10000 represents between 20 and 80% of the total pore volume.  11. Method according to any one of claims 1 to 10, characterized in that the hydrocracking step is carried out at a temperature T2 of between 300 and 400 C.