EP3255123A1 - Conversion method comprising at least one fixed-bed hydrotreatment step and a hydrocracking step in by-passable reactors - Google Patents

Abstract

The invention relates to a process for the treatment of a hydrocarbon feedstock making it possible to obtain a heavy hydrocarbon fraction with a low sulfur content, said process comprising the following steps: a) an optional step of hydrodemetallation in reactive reactors; b) a step of fixed bed hydrotreatment of the effluent from step a), c) a step of hydrocracking in passible reactors of the effluent from step b), d) a step of separation of the effluent from step c).

Description

The present invention relates to the refining and the conversion of heavy hydrocarbon fractions containing, inter alia, sulfur-containing impurities. It relates more particularly to a process for the conversion of heavy petroleum feedstocks of the atmospheric residue and / or vacuum residue type for the production of heavy fractions that can be used as fuel bases, in particular as bunker oil bases with a low sediment content. The process according to the invention also makes it possible to produce atmospheric distillates (naphtha, kerosene and diesel), vacuum distillates and light gases (C1 to C4).

The quality requirements for marine fuels are described in ISO 8217. The sulfur specification now focuses on SO _x emissions (Annex VI of the MARPOL Convention of the International Maritime Organization). It results in a sulfur content recommendation of 0.5% or less outside the Sulfur Emission Control Areas (ZCES or Emission Control Areas) by 2020-2025, and below or equal to 0.1% by weight in ZCESs. Another very restrictive recommendation is the sediment content after aging according to ISO 10307-2 (also known as IP390) which must be less than or equal to 0.1%.

The sediment content according to ISO 10307-1 (also known as IP375) is different from the sediment content after aging according to ISO 10307-2 (also known as IP390). The sediment content after aging according to ISO 10307-2 is a much more stringent specification and corresponds to the specification for bunker fuels.

According to Annex VI of the MARPOL Convention, a ship may therefore use a sulfur-containing fuel oil if the ship is equipped with a flue gas treatment system that reduces emissions of sulfur oxides.

Fuel oils used in shipping generally include atmospheric distillates, vacuum distillates, atmospheric residues and residues. under vacuum from direct distillation or from refining process, including hydrotreating and conversion processes, these sections can be used alone or in mixture. These processes, although known to be suitable for heavy loads loaded with impurities, however, produce hydrocarbon fractions that may include catalyst fines and / or sediments that must be removed to satisfy a product quality such as bunker fuel oil.

The sediments may be precipitated asphaltenes. The conversion conditions, and in particular the temperature, cause them to undergo reactions (dealkylation, polycondensation, etc.) leading to their precipitation. In addition to the existing sediments in the heavy cut at the end of the process (measured according to ISO 10307-1, also known as IP375), there are also, according to the conversion conditions, sediments qualified as potential sediments that do not appear. only after physical, chemical and / or thermal treatment. All sediments including potential sediments are measured according to ISO 10307-1 also known as IP390. These sedimentation phenomena generally occur during the implementation of severe conditions (high temperature and residence time) giving rise to high conversion rates, for example greater than 35, 40 or 50% or more, and this depending on the nature of the charge. The formation of potential and / or existing sediments also tends to increase with the aging of the catalysts.

The conversion ratio is defined as the mass fraction of organic compounds having a boiling point above 520 ° C in the feed at the inlet of the reaction section minus the mass fraction of organic compounds having a higher boiling point. at 520 ° C at the outlet of the reaction section in the effluent, all divided by the mass fraction of organic compounds having a boiling point above 520 ° C at the inlet of the reaction section in the feedstock. In waste treatment processes, there is an economic interest in maximizing conversion because, generally, conversion products, especially distillates, are better valued than the unconverted feed or fraction.

In fixed bed hydrotreatment processes, the temperature is generally lower than in bubbling bed or slurry bed hydrocracking processes. The conversion rate in fixed bed is therefore generally lower, but the implementation is simpler than bubbling bed or "slurry". Thus the conversion rate of hydrotreatment processes in fixed bed is moderate or low, generally less than 45%, usually less than 35% at the end of the cycle, and less than 25% at the beginning of the cycle. The conversion rate generally varies during the cycle due to the increase in temperature to compensate for the catalytic deactivation.

In fact, sediment production is generally lower in fixed bed hydrotreatment processes than in bubbling bed or slurry bed hydrocracking processes. However, the temperatures sometimes reached from the middle of the cycle and up to the end of the cycle for fixed bed residue hydrotreating processes can lead to a sufficient sediment formation to degrade the quality of an oil, especially an oil. bunker, consisting largely of a heavy fraction from a process of hydrotreatment of residues in fixed bed. The skilled person is familiar with the difference between fixed bed and bed in "slurry". A "slurry" bed is a bed in which the catalyst is sufficiently dispersed in the form of small particles to be suspended in the liquid phase.

Brief description of the invention

In the context previously described, the Applicant has developed a new process incorporating a hydrocracking step in passable reactors allowing increased conversion over conventional hydrotreating processes residues.

By "passable reactor" is meant a reactor, which can be stopped by the implementation of a "by pass" while the other reactors of the unit are still in operation. Unlike the so-called reactive reactors that can be put back into service while the other (or other) reactor (s) of the unit is (are) in operation, the bypassable reactors can be shut down at any time and usually restarted only when restarting the entire unit

To image the difference between the two types of reactors, a bypassable reactor can be erased at any time and for a longer or shorter duration of the production scheme, while a switchable reactor necessarily stops in favor of another. which restarts.

Of course, the notion of "passable" reactors can be applied to a set of reactors that can be stopped and restarted, simultaneously or otherwise.

Surprisingly, it has been found that such a process using bypassable reactors makes it possible to obtain, after fractionation, low sulfur hydrocarbon fractions, distillates in increased quantity, and at least one liquid hydrocarbon fraction which can advantageously be used. , totally or partially, as fuel oil or as fuel oil base. The new process employs a per passable hydrocracking reactor which is in service for only part of the unit cycle, so as to obtain after fractionation at least one low sulfur heavy fraction meeting the future recommendations of the unit. IMO, but especially low sediment content, namely a sediment content after aging less than or equal to 0.1% by weight.

Another advantage of the new process incorporating a hydrocracking step in passable reactors is that it becomes possible to operate these hydrocrackable reactors at an average temperature over the entire cycle that is higher than that of the reactors. the fixed bed hydrotreatment section, thus leading to a higher conversion without the formation of sediment, generally increased by the higher temperature, is problematic for the quality of the product.

The temperature of the bypassable reactor requiring the shutdown of the reactor is generally between 390 ° C. and 430 ° C., and preferably between 405 ° C. and 425 ° C.

The passable hydrocracking section is stopped in such a way as to prevent the generation of sediments, in particular potential sediments, while allowing hydrotreatment to be continued on the upstream reactors.

Most often, the hydrocracking section is implemented from the beginning of the cycle of the unit and for at least 30% of the cycle, or even at least 50% of the cycle. The stopping temperature of the hydrocracking section in passable reactors is to be determined by the operator by monitoring the sediment content of the effluent, in particular the potential sediments, as soon as the sediment content after aging ( IP390) is greater than 0.05 or 0.08% by weight for example, it is time to stop the hydrocracking section in passable reactors.

The average temperature of the process is a mass weighting of the average temperatures of the different beds. It is calculated taking into account for each reactor its average temperature and its weight of catalysts.

For example, for a two-bed reactor of mass m1 and m2 and average temperature T1 and T2, the weighted average temperature will be calculated as (T1 * m1 + T2 * m2) / (m1 + m2).

During the period from the beginning to about the middle of the cycle, the catalysts of the hydrotreatment section are little deactivated and therefore active at moderate temperatures which leads to the production of very stable effluents with no sediment, there is therefore an interest in exploiting this margin of stability by applying a hydrocracking step in passable reactors operating at a higher temperature and allowing a gain in conversion. Similarly, the coking and the increase of the pressure drop are not problematic in the hydrocracking section, since the bypassable reactors can be stopped without stopping the unit, which then makes it possible to reduce the pressure drop of the section. reaction by subtraction of the loss of charges from the reactors by passables.

For terrestrial applications such as power generation plants or utilities production, there are requirements for sulfur content fuel oil, with lower demands on stability and sediment content than for bunker fuels intended to be burned in engines.

1. a) une étape optionnelle d'hydrodémétallation en réacteurs permutables dans laquelle la charge hydrocarbonée est mise en contact avec de l'hydrogène sur un catalyseur d'hydrodémétallation,
2. b) une étape d'hydrotraitement en lit fixe de l'effluent issu de l'étape a),
3. c) une étape d'hydrocraquage en réacteurs by passables de l'effluent issu de l'étape b),
4. d) une étape de séparation de l'effluent issu de l'étape c) conduisant à au moins une fraction gaz et une fraction liquide ayant une teneur en sédiments après vieillissement inférieure ou égale à 0,1% en poids,

More specifically, the invention relates to a process for treating a hydrocarbon feed containing at least one hydrocarbon fraction having a sulfur content of at least 0.1% by weight, an initial boiling point of at least 340 ° C and a final boiling temperature of at least 440 ° C, to obtain conversion products and a heavy hydrocarbon fraction with low sulfur content. This heavy hydrocarbon fraction may be optionally produced so that its sediment content after aging is less than or equal to 0.1% by weight. The method comprises the following steps:

1. a) an optional hydrodemetallation step in permutable reactors in which the hydrocarbon feedstock is contacted with hydrogen on a hydrodemetallization catalyst,
2. b) a fixed bed hydrotreating step of the effluent from step a),
3. c) a hydrocracking step in passible reactors of the effluent from step b),
4. d) a step of separating the effluent from step c) leading to at least a gas fraction and a liquid fraction having a sediment content after aging less than or equal to 0.1% by weight,

One of the objectives of the present invention is to propose a process coupling conversion and desulphurization of heavy petroleum feedstocks for the production of fuel oils and low-sulfur fuel oil bases.

Another objective of the process according to the invention is the production of bunker fuels or bunker oil bases with a low sediment content, that is to say, after aging less than or equal to 0.1% by weight, this being achieved by the implementation of steps a), b), c) and d) during the first part of the cycle, then by stopping the reactors by passables in the second part of the cycle.

Another object of the present invention is to jointly produce, by the same method, atmospheric distillates (naphtha, kerosene, diesel), vacuum distillates and / or light gases (C1 to C4). The bases of the naphtha and diesel type can be upgraded to refineries for the production of automotive and aviation fuels, such as, for example, super-fuels, Jet fuels and gas oils.

Description of Figure 1

The figure 1 describes a scheme for implementing the invention without limiting its scope. The hydrocarbon feedstock (1) and hydrogen (2) are brought into contact in an optional step a) of hydrodemetallation in permutable reactors, in which the hydrogen (2) can be introduced at the inlet of the first catalytic bed and between two beds of step a).

The effluent (3) resulting from the hydrodemetallation stage a) in swarfable reactor reactors is sent to a fixed bed hydrotreatment stage b), in which additional hydrogen (4) can be introduced as input of the first catalytic bed and between two beds of step b).

In the absence of step a), the hydrocarbon feedstock (1) and the hydrogen (2) are introduced directly into the hydrotreatment step b). The effluent (5) resulting from the fixed bed hydrotreating step b) is sent to a step c) of hydrocracking in passable reactors in which additional hydrogen (6) can be introduced at the inlet of the first catalytic bed and between two beds of step c). When at least one reactor of the bypassable hydrocracking section is stopped, this reactor is short-circuited by means of valves, that is to say that the supply of this reactor is directly connected to the reactor. the effluent line of this reactor. If there is only a single passable reactor or when all the bypassable reactors are stopped, the effluent (5) resulting from the fixed bed hydrotreatment step is introduced directly at the inlet of the step d) separation.

When at least one passable reactor is in operation, the effluent (7) from the hydrocracking step c) in passable reactors is sent in a step of separation d) for obtaining at least a light hydrocarbon fraction (8) and a heavy fraction (9) containing compounds boiling at least 350 ° C. and having a sediment content after aging less than or equal to 0.1% by weight.

Description of Figure 2

The figure 2 describes a simplified diagram of implementation of the sequence of reactors of the invention without limiting the scope thereof. For the sake of simplicity only the reactors are represented but it is understood that all the equipment necessary for operation are present (balloons, pumps, exchangers, ovens, columns, etc.). Only the main streams containing the hydrocarbons are represented, but it is understood that hydrogen-rich gas streams (make-up or recycle) can be injected at the inlet of each catalytic bed or between two beds.

The charge (1) enters a hydrodemetallation step in reactive guard reactors consisting of reactors Ra and Rb. The effluent (2) of the hydrodemetallation step in permutable guard reactors is sent to the fixed bed hydrotreating step consisting of the reactors R1, R2 and R3. The fixed bed hydrotreating reactors can for example be loaded respectively with hydrodemetallation, transition and hydrodesulfurization catalysts. Because the hydrodemetallization step in a switchable guard reactors is optional, the feedstock (1) can enter directly into the fixed bed hydrotreatment section. The effluent (3) of the fixed bed hydrotreating step is sent to the per passable hydrocracking step represented by a reactor Rc.

Each reactor Ra, Rb, Rc can be taken offline without stopping the rest of the unit. On the other hand, only Ra and Rb which are permutable reactors can be stopped so as to change the catalyst and then be restarted without stopping the rest of the unit. This catalyst change (rinsing, unloading, reloading, sulphurization and restarting) is generally allowed by a not shown packaging section. The reactor Rc stops during the cycle without stop the rest of the unit but will only be restarted after the complete shutdown of the unit, the purpose of this stop being to unload and reload all deactivated catalysts. The following table gives an example of realizable sequences according to the figure 2 : Permutable hydrodemetallation Hydrotreatment in fixed bed by passable hydrocracking sequences offline HDM1 HDM2 HDM Transition HDS offline HCK1 1 - Ra Rb R1 R2 R3 - rc 2 Ra - Rb R1 R2 R3 - rc 3 - Rb Ra R1 R2 R3 - rc 4 - Rb Ra R1 R2 R3 rc -

During the sequence 1 which starts at the beginning of the cycle, all the reactors are in operation until the time when the reactive hydrodemetallation reactor R A is deactivated and / or clogged. Ra is then taken offline during the sequence 2 so as to discharge the spent catalyst (previously rinsed in situ via the conditioning section) and then reload fresh or regenerated catalyst (previously sulphured ex situ or in situ via the conditioning section) . In sequence 3, the switchable reactor Ra is brought back online downstream of the switchable reactor Rb, so there has been permutation. After a certain time, the reactors reach on average a critical temperature because of the catalytic deactivation of all the catalysts, it is then time in the sequence 4 to stop the reactor Rc by passable hydrocracking, until the end of the cycle, so as to control the production of sediments, in particular potential sediments. During the next cycle, it is possible to restart with the switchable hydrodemetallization reactor Rb at the head. It is also possible to retain all or part of the catalysts of the previous cycle if it is not completely deactivated, which may for example be the case if a switchable hydrodemetallation reactor is put online shortly before the total shutdown of the reactor. 'unit. The preceding table is only an illustration of the possible sequences, it being understood that the deactivation time of the hydrodemetallation reactive reactors is a function of the treated feedstock, in particular the metal content. Similarly, the operating time of the hydrocracking section in permutable reactors is a function of the load and of the applied severity (temperature and residence time in particular).

Thus, we must not remember the order in which the reactive or bypassable reactors are taken offline but we must simply remember the possibility of doing it at any time without completely stopping the unit.

Similarly, there may be more than 2 permutable reactors in the hydrodemetallation section in permutable reactors, or more than 1 reactor per passable in the hydrocracking section in passable reactors. Similarly, there may be more or less than 3 fixed bed hydrotreating reactors, the representation by R1, R2 and R3 being given purely by way of illustration.

Detailed description of the invention

The following text provides information on the charge and the various steps of the method according to the invention.

The charge

The feedstock treated in the process according to the invention is advantageously a hydrocarbon feed having an initial boiling point of at least 340 ° C. and a final boiling point of at least 440 ° C. Preferably, its initial boiling point is at least 350 ° C., preferably at least 375 ° C., and its final boiling point is at least 450 ° C., preferably at least 460 ° C. C, more preferably at least 500 ° C, and even more preferably at least 600 ° C.

The hydrocarbon feedstock according to the invention may be chosen from atmospheric residues, vacuum residues resulting from direct distillation, crude oils, crude head oils, deasphalting resins, asphalts or deasphalting pitches, process residues. conversion products, aromatic extracts from lubricant base production lines, oil sands or derivatives thereof, oil shales or their derivatives, source rock oils or their derivatives, whether alone or in combination. In the present invention, the fillers being treated are preferably atmospheric residues or vacuum residues, or mixtures of these residues.

The hydrocarbon feedstock treated in the process may contain, among other things, sulfur-containing impurities. The sulfur content may be at least 0.1% by weight, preferably at least 0.5% by weight, preferably at least 1% by weight, more preferably at least 2% by weight. .

The hydrocarbon feedstock treated in the process may contain, inter alia, metallic impurities, in particular nickel and vanadium. The sum of the nickel and vanadium contents is generally at least 10 ppm, preferably at least 50 ppm, preferably at least 100 ppm.

These charges can advantageously be used as they are. Alternatively, they can be diluted by co-charging. This co-charge may be a hydrocarbon fraction or a lighter hydrocarbon fraction mixture, which may preferably be chosen from the products resulting from a fluid catalytic cracking (FCC) process according to the English terminology. Saxon), a light cut (LCO or "light cycle oil" according to the English terminology), a heavy cut (HCO or "heavy cycle oil" according to the English terminology), a decanted oil, a residue of FCC, a gas oil fraction, especially a fraction obtained by atmospheric distillation or under vacuum, such as vacuum gas oil, or may come from another refining process such as coking or visbreaking.

The co-charge may also advantageously be one or more cuts resulting from the process of liquefying coal or biomass, aromatic extracts, or any other hydrocarbon cuts, or non-petroleum fillers such as pyrolysis oil. The heavy hydrocarbon feedstock according to the invention may represent at least 50%, preferably 70%, more preferably at least 80%, and even more preferably at least 90% by weight of the total hydrocarbon feedstock treated by the process according to the invention.

In some cases it is possible to introduce the charge downstream of the first or following bed, for example at the inlet of the hydrotreatment section in a fixed bed, or at the inlet of the hydrocracking section in passable reactors.

The process according to the invention makes it possible to obtain conversion products, in particular distillates and a heavy hydrocarbon fraction with a low sulfur content. This heavy hydrocarbon fraction may be produced in such a way that its sediment content after aging is less than or equal to 0.1% by weight, this being allowed by the stopping (bypass or bypass) of at least one reactor of the hydrocracking section in passable reactors.

Step a) optional hydrodemetallation in reactive guard reactors

During the optional hydrodemetallation step a), the feedstock and hydrogen are contacted on a hydrodemetallization catalyst charged to at least two permutable reactors under hydrodemetallation conditions. This optional step a) is preferably carried out when the feed contains more than 50 ppm, or even more than 100 ppm of metals and / or when the feedstock comprises impurities capable of inducing too fast clogging of the catalytic bed, such as derivatives of iron or calcium for example. The goal is to reduce the impurity content and thus protect the downstream hydrotreating step from the deactivation and clogging, hence the notion of aging reactors. These reactors hydrodemetallation guards are implemented as permutable reactors (technology "PRS" for "Permutable Reactor System" according to the English terminology) as described in the patent FR2681871 .

These permutable reactors are generally fixed beds located upstream of the fixed bed hydrotreatment section and equipped with lines and valves so as to be permuted between them, that is to say for a system with two permutable reactors Ra and Rb, Ra can be in front of Rb and vice versa. Each reactor Ra, Rb can be taken offline so as to change the catalyst without stopping the rest of the unit. This catalyst change (rinsing, unloading, reloading, sulphurization and restart) is generally allowed by a conditioning section (set of equipment outside the main high pressure loop). The permutation for catalyst change occurs when the catalyst is no longer sufficiently active (poisoning by metals and coking) and / or the clogging reaches a loss of pressure too high.

According to one variant, there may be more than 2 reactive reactors in the hydrodemetallation section in permutable reactors.

During step a) of hydrodemetallation, hydrodemetallation reactions (commonly called HDM), but also hydrodesulphurization reactions (commonly called HDS), hydrodenitrogenation reactions (commonly called HDN) accompanied by Hydrogenation, hydrodeoxygenation, hydrodearomatization, hydroisomerization, hydrodealkylation, hydrocracking, hydrodephalting and Conradson carbon reduction reactions. Step a) is called hydrodemetallation because it removes the majority of the metals from the charge.

The hydrodemetallation stage a) in permutable reactors according to the invention may advantageously be carried out at a temperature of between 300 ° C. and 500 ° C., preferably between 350 ° C. and 430 ° C., and under an absolute pressure. between 5 MPa and 35 MPa, preferably between 11 MPa and 26 MPa, preferably between 14 MPa and 20 MPa. The temperature is usually adjusted according to the desired level of hydrodemetallation and the duration of the targeted treatment. Most often, the space velocity of the hydrocarbon feedstock, commonly referred to as VVH, which is defined as the volumetric flow rate of the feedstock divided by the total volume of the catalyst, can be in a range of 0.1 h ^-1. at 5 h ^-1 , preferably from 0.15 h ^-1 to 3 h ^-1 , and more preferably from 0.2 h ^-1 to 2 h ^-1 .

The amount of hydrogen mixed with the feedstock may be between 100 and 5000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feedstock, preferably between 200 Nm3 / m3 and 2000 Nm3 / m3, and more preferably between 300 Nm3 / m3 and 1000 Nm3 / m3. The hydrodemetallation stage a) in permutable reactors can be carried out industrially in at least two reactors in a fixed bed and preferably in a downflow of liquid.

The hydrodemetallization catalysts used are preferably known catalysts. They may be granular catalysts comprising, on a support, at least one metal or metal compound having a hydro-dehydrogenating function.

These catalysts may advantageously be catalysts comprising at least one Group VIII metal, generally selected from the group consisting of nickel and cobalt, and / or at least one Group VIB metal, preferably molybdenum and / or tungsten. For example, it is possible to use a catalyst comprising from 0.5% to 10% by weight of nickel, preferably from 1% to 5% by weight of nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of nickel. weight of molybdenum, preferably from 3% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a mineral support. This support may for example be chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. Advantageously, this support may contain other doping compounds, in particular oxides selected from the group consisting of boron oxide, zirconia, ceria, titanium oxide, phosphoric anhydride and a mixture of these oxides. Most often an alumina support is used and very often a support of alumina doped with phosphorus and possibly boron. When phosphorus pentoxide P2O5 is present, its concentration is less than 10% by weight. When B2O5 boron trioxide is present, its concentration is less than 10% by weight. The alumina used may be a gamma (γ) or η (eta) alumina. This catalyst is most often in the form of extrudates. The total content of metal oxides of groups VIB and VIII may be from 5% to 40% by weight, preferably from 5% to 30% by weight, and the weight ratio expressed as metal oxide between metal (or metals) of group VIB on metal (or metals) of group VIII is generally between 20 and 1, and most often between 10 and 2.

Catalysts that can be used in the hydrodemetallation step a) in permutable reactors are, for example, indicated in the patent documents. EP 0113297 , EP 0113284 , US 5221656 , US 5827421 , US 7119045 , US 5622616 and US 5089463 .

Step b) Fixed bed hydrotreatment

The effluent from the optional hydrodemetallation step a) is introduced, optionally with hydrogen, into a fixed bed hydrotreating step b) to be contacted on at least one hydrotreatment catalyst.

In the absence of the optional hydrodemetallation step a) in reactive guard reactors, the feedstock and the hydrogen are introduced directly into the fixed bed hydrotreatment step b) to be brought into contact on at least one hydrotreating catalyst (s) The hydrotreatment catalyst (s) are used in at least one fixed bed reactor and preferably with a liquid downflow reactor.

Hydrotreatment, commonly known as HDT, is understood to mean the catalytic treatments with hydrogen supply making it possible to refine, that is to say, to reduce substantially the content of metals, sulfur and other impurities, hydrocarbon feedstocks, while improving the ratio hydrogen on the load and transforming the load more or less partially into lighter cuts. Hydrotreatment includes, in particular, hydrodesulfurization reactions (commonly referred to as HDS), hydrodenitrogenation reactions (commonly referred to as HDN), and hydrodemetallation reactions (commonly referred to as HDM), accompanied by hydrogenation, hydrodeoxygenation, hydrogenation, and hydrogenation reactions. hydrodearomatization, hydroisomerization, hydrodealkylation, hydrocracking, hydro-deasphalting and Conradson carbon reduction.

According to a preferred variant, the hydrotreatment step b) comprises a first hydrodemetallation stage (HDM) b1) carried out in one or more hydrodemetallation zones in fixed beds and a second hydrodesulphurization second stage (b2) (HDS). performed in one or more hydrodesulfurization zones in fixed beds. During said first hydrodemetallation step b1), the effluent from step a), or the feedstock and hydrogen in the absence of step a), are contacted on a catalyst of hydrodemetallation, under hydrodemetallation conditions, then during said second hydrodesulfurization step b2), the effluent of the first hydrodemetallation step b1) is brought into contact with a hydrodesulphurization catalyst, under conditions of hydrodesulfurization. This process, known as HYVAHL-F ™, is for example described in the patent US 5417846 .

The person skilled in the art easily understands that, in step b1) of hydrodemetallization, hydrodemetallation reactions are carried out but at the same time also a part other hydrotreating reactions, and in particular hydrodesulfurization and hydrocracking reactions. Similarly, in the hydrodesulfurization step b2), hydrodesulphurization reactions are carried out, but also part of the other hydrotreatment reactions, in particular hydrodemetallation and hydrocracking reactions.

Those skilled in the art sometimes define a transition zone in which all types of hydrotreatment reactions occur. According to another variant, the hydrotreatment stage b) comprises a first hydrodemetallation stage (HDM) b1) carried out in one or more hydrodemetallation zones in fixed beds, a second transition stage b2) carried out in one or more a plurality of transition zones in fixed beds, and a third hydrodesulphurization (HDS) step b3) carried out in one or more hydrodesulfurization zones in fixed beds. During said first hydrodemetallation step b1), the effluent from step a), or the feedstock and hydrogen in the absence of step a), are contacted on a catalyst of hydrodemetallization, under hydrodemetallation conditions, then during said second transition step b2), the effluent of the first hydrodemetallation step b1) is brought into contact with a transition catalyst, under transition conditions, then during said third hydrodesulfurization step b3), the effluent of the second transition stage b2) is brought into contact with a hydrodesulfurization catalyst, under hydrodesulfurization conditions.

Step b1) of hydrodemetallization according to the above variants is particularly necessary in the absence of step a) hydrodemetallation in reactive guard reactors so as to treat the impurities and protect the downstream catalysts. The need for a hydrodemetallation step b1) according to the above variants in addition to the hydrodemetallation step a) in relatable guard reactors is justified when the hydrodemetallization carried out in step a) is not not sufficient to protect the catalysts of step b), in particular the hydrodesulphurization catalysts.

The hydrotreating step b) according to the invention is carried out under hydrotreatment conditions. It can advantageously be implemented at a temperature between 300 ° C and 500 ° C, preferably between 350 ° C and 430 ° C and under an absolute pressure between 5 MPa and 35 MPa, preferably between 11 MPa and 26 MPa, preferably between 14 MPa and 20 MPa. The temperature is usually adjusted according to the desired level of hydrotreatment and the duration of the targeted treatment. Most often, the space velocity of the hydrocarbon feedstock, commonly referred to as VVH, which is defined as the volumetric flow rate of the feedstock divided by the total volume of the catalyst, can be in a range of 0.1 h ^-1. at 5 h ^-1 , preferably from 0.1 h ^-1 to 2 h ^-1 , and more preferably from 0.1 h ^-1 to 1 h ^-1 . The amount of hydrogen mixed with the feedstock may be between 100 and 5000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feedstock, preferably between 200 Nm3 / m3 and 2000 Nm3 / m3, and more preferably between 300 Nm3 / m3 and 1500 Nm3 / m3. The hydrotreating step b) can be carried out industrially in one or more liquid downflow reactors.

The hydrotreatment catalysts used are preferably known catalysts. They may be granular catalysts comprising, on a support, at least one metal or metal compound having a hydro-dehydrogenating function. These catalysts may advantageously be catalysts comprising at least one Group VIII metal, generally selected from the group consisting of nickel and cobalt, and / or at least one Group VIB metal, preferably molybdenum and / or tungsten. For example, it is possible to use a catalyst comprising from 0.5% to 10% by weight of nickel, preferably from 1% to 5% by weight of nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of nickel. weight of molybdenum, preferably from 3% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a mineral support. This support may for example be chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals.

Advantageously, this support may contain other doping compounds, in particular oxides selected from the group consisting of boron oxide, zirconia, ceria, titanium oxide, phosphoric anhydride and a mixture of these. oxides. Most often an alumina support is used and very often a support of alumina doped with phosphorus and possibly boron. When phosphorus pentoxide P2O5 is present, its concentration is less than 10% by weight. When B2O5 boron trioxide is present, its concentration is less than 10% by weight. The alumina used may be a gamma (γ) or η (eta) alumina. This catalyst is most often in the form of extrudates. The total content of metal oxides of groups VIB and VIII may be from 3% to 40% by weight and generally from 5% to 30% by weight and the weight ratio expressed as metal oxide between metal (or metals) of group VIB on metal (or metals) of group VIII is generally between 20 and 1, and most often between 10 and 2.

In the case of a hydrotreatment step including a hydrodemetallation step (b1) (HDM) and then a hydrodesulfurization step (b2) (HDS), specific catalysts adapted to each step are preferably used. Catalysts that can be used in the hydrodemetallation step b1) are, for example, indicated in the patent documents. EP 0113297 , EP 0113284 , US 5221656 , US 5827421 , US 7119045 , US 5622616 and US 5089463 . Catalysts that can be used in the hydrodesulfurization step b2) are, for example, indicated in the patent documents EP 0113297 , EP 0113284 , US 6589908 , US 4818743 or US 6332976 . It is also possible to use a mixed catalyst also called transition catalyst, active in hydrodemetallation and hydrodesulphurization, for both the hydrodemetallation section b1) and for the hydrodesulphurization section b2) as described in the patent document. FR 2940143 .

In the case of a hydrotreatment step including a step b1) of hydrodemetallation (HDM) then a step b2) of transition, then a step b3) hydrodesulfurization (HDS), it is preferred to use specific catalysts adapted to each step. Catalysts that can be used in the hydrodemetallation step b1) are, for example, indicated in the patent documents. EP 0113297 , EP 0113284 , US 5221656 , US 5827421 , US 7119045 , US 5622616 and US 5089463 . Catalysts that can be used in the transition stage b2), which are active in hydrodemetallation and hydrodesulphurization, are described, for example, in the US Pat. patent document FR 2940143 . Catalysts that can be used in the hydrodesulfurization step b3) are, for example, indicated in the patent documents EP 0113297 , EP 0113284 , US 6589908 , US 4818743 or US 6332976 . It is also possible to use a transition catalyst as described in the patent document FR 2940143 for sections b1), b2) and b3).

Step c) hydrocracking in reactors by passables

The effluent from step b) of hydrotreatment is introduced into a stage c) of hydrocracking in passable reactors. Hydrogen can also be injected upstream of the different catalytic beds composing the hydrocrackable bypassable reactors. In addition to the thermal cracking and hydrocracking reactions desired in this step, any type of hydrotreating reaction (HDM, HDS, HDN, etc.) is also produced. Specific conditions, including temperature, and / or the use of one or more specific catalysts, promote the desired cracking or hydrocracking reactions.

The reactors of the hydrocracking step c) are used as bypassable reactors. By passable reactors we mean a set of at least one reactor, which can be stopped by the implementation of a bypass (short circuit using lines and valves) while the other (or the other) reactor (s) of the unit (ie the hydrodemetallation section and / or the hydrotreatment section) is (are) in operation. Unlike the so-called reactive reactors which can be put back into service while the other (or the other) reactor (s) of the unit is (are) in operation, the bypassable reactors do not have this possibility (or the restarting is not desired), they will be put back into service when the whole unit is restarted.

According to a non-preferred variant, there may be more than 1 reactor per passable in the hydrocracking section in passable reactors.

The hydrocracking step c) according to the invention is carried out under hydrocracking conditions. It can advantageously be used at a temperature of between 340 ° C. and 480 ° C., preferably between 350 ° C. and 430 ° C. absolute pressure of between 5 MPa and 35 MPa, preferably between 11 MPa and 26 MPa, preferably between 14 MPa and 20 MPa. The temperature is usually adjusted according to the desired level of hydrocracking and the duration of the intended treatment. Preferably, the average temperature at the beginning of the cycle of the per passable reactor hydrocracking step c) is always greater by at least 5 ° C, preferably by at least 10 ° C, more preferably by at least 15 ° C at the average temperature at the beginning of the cycle of the hydrotreatment step b). This difference may decrease during the cycle due to the increase of the temperature of the hydrotreating step b) to compensate for the catalytic deactivation. Overall, the average temperature over the entire cycle of step c) of hydrocracking in passable reactors is always at least 5 ° C higher than the average temperature over the entire cycle of step b) hydrotreating.

Most often, the space velocity of the hydrocarbon feedstock, commonly referred to as VVH, which is defined as the volumetric flow rate of the feedstock divided by the total volume of the catalyst, can be in a range of 0.1 h ^-1. at 5 h ^-1 , preferably from 0.2 h ^-1 to 2 h ^-1 , and more preferably from 0.25 h ^-1 to 1 h ^-1 . The amount of hydrogen mixed with the feedstock may be between 100 and 5000 normal cubic meters (Nm3) per cubic meter (m3) of liquid feedstock, preferably between 200 Nm3 / m3 and 2000 Nm3 / m3, and more preferably between 300 Nm3 / m3 and 1500 Nm3 / m3. The hydrocracking step c) can be carried out industrially in at least one fixed-bed reactor, and preferably with a downflow of liquid.

The hydrocracking catalysts used may be hydrocracking or hydrotreatment catalysts. They may be granular catalysts, in the form of extrudates or beads, comprising, on a support, at least one metal or metal compound having a hydro-dehydrogenating function. These catalysts may advantageously be catalysts comprising at least one Group VIII metal, generally selected from the group consisting of nickel and cobalt, and / or at least one Group VIB metal, preferably molybdenum and / or tungsten. For example, it is possible to use a catalyst comprising from 0.5% to 10% by weight of nickel, preferably from 1% to 5% by weight of nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of nickel. weight of molybdenum, preferably from 5% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a mineral support. This support may for example be chosen from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. Advantageously, this support may contain other doping compounds, in particular oxides selected from the group consisting of boron oxide, zirconia, ceria, titanium oxide, phosphoric anhydride and a mixture of these oxides. Most often an alumina support is used and very often a support of alumina doped with phosphorus and possibly boron. When phosphorus pentoxide P2O5 is present, its concentration is less than 10% by weight. When B2O5 boron trioxide is present, its concentration is less than 10% by weight. The alumina used may be a gamma (γ) or η (eta) alumina. This catalyst is most often in the form of extrudates. The total content of metal oxides of groups VIB and VIII may be from 5% to 40% by weight and in general from 7% to 30% by weight and the weight ratio expressed as metal oxide between metal (or metals) of group VIB on metal (or metals) of group VIII is generally between 20 and 1, and most often between 10 and 2.

Alternatively, the hydrocracking step can in part or in all advantageously use a bifunctional catalyst, having a hydrogenating phase in order to be able to hydrogenate the aromatics and achieve the equilibrium between the saturated compounds and the corresponding olefins and a phase acid that promotes the hydroisomerization and hydrocracking reactions. The acid function is advantageously provided by supports with large surface areas (generally 100 to 800 m2.g-1) having a surface acidity, such as halogenated aluminas (chlorinated or fluorinated in particular), combinations of boron oxides and aluminum, amorphous silica-aluminas and zeolites. The hydrogenating function is advantageously 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 an association of at least a group VIB metal of the periodic table such as molybdenum and tungsten and at least one non-noble group VIII metal (such as nickel and cobalt). The catalyst must also advantageously have a high resistance to impurities and asphaltenes due to the use of a heavy load.

Preferably, the bifunctional catalyst used comprises at least one metal selected from the group consisting of Group VIII and VIB metals, taken alone or as a mixture, and a support comprising 10 to 90% by weight of a zeolite containing iron and 90% by weight. at 10% by weight of inorganic oxides. The Group VIB metal used is preferably selected from tungsten and molybdenum and the Group VIII metal is preferably selected from nickel and cobalt. The bifunctional catalyst is preferably prepared according to the method of preparation described in Japanese Patent Application No. 2289,419 (IKC) or EP 0 384 186 . Examples of this type of catalysts are described in the patents JP 2966 985 , JP 2908 959 , JP 01 049399 and JP 61 028717 , US 4,446,008 , US 4,622,127 , US 6,342,152 , EP 0 537 500 and EP 0 622 118 .

According to another preferred variant, monofunctional catalysts and bifunctional catalysts of the alumina, amorphous silica-alumina or zeolitic type may be used in a mixture or in successive layers.

The use in the hydrocracking section of catalysts analogous to bubbling bed hydrocracking catalysts or bifunctional catalysts is particularly advantageous.

Prior to the injection of the feed, the catalysts used in the process according to the present invention are preferably subjected to an in-situ or ex-situ sulphurization treatment.

Step d) separating the hydrocracking effluent

The process according to the invention may furthermore comprise a step d) of separation which makes it possible to obtain at least one gaseous fraction and at least one heavy liquid fraction.

The effluent obtained at the end of step c) of hydrocracking (or of step b) of hydrotreatment when the reactor (s) are passable comprises a liquid fraction and a gaseous fraction containing the gases. , especially H2, H2S, NH3, and C1-C4 hydrocarbons. This gaseous fraction can be separated from the effluent by means of separating devices that are well known to those skilled in the art, in particular by means of one or more separator flasks that can operate at different pressures and temperatures, possibly associated with stripping means with steam or hydrogen and one or more distillation columns. The effluent obtained at the end of step c) of hydrocracking or hydrotreatment step b) when the at least one reactor is passed through, is advantageously separated in at least one separator tank into at least one a gaseous fraction and at least one heavy liquid fraction. These separators may for example be high temperature high pressure separators (HPHT) and / or high temperature low pressure separators (HPBT).

After a possible cooling, this gaseous fraction is preferably treated in a hydrogen purification means so as to recover the hydrogen that is not consumed during the hydrotreatment and hydrocracking reactions. The hydrogen purification means may be an amine wash, a membrane, a PSA type system, or a plurality of such means arranged in series. The purified hydrogen can then advantageously be recycled in the process according to the invention, after possible recompression. The hydrogen may be introduced at the inlet of the hydrodemetallization step a) and / or at different locations during the hydrotreatment step b) and / or at the inlet of the hydrocracking step c) and / or at different locations during step c) hydrocracking.

The separation step d) may also comprise atmospheric distillation and / or vacuum distillation. Advantageously, the separation step d) further comprises at least one atmospheric distillation, in which the liquid hydrocarbon fraction (s) obtained (s) obtained after separation is (are) fractionated (s) by atmospheric distillation in at least one atmospheric distillate fraction and at least one atmospheric residue fraction. The atmospheric distillate fraction can contain fuel bases (naphtha, kerosene and / or diesel) that can be used commercially, for example in refineries for the production of motor and aviation fuels. The kerosene and / or diesel type fractions may also be used as fluxes and be incorporated into a distillate type or residual type fuel or oil fuel pool (according to ISO8217).

In addition, the separation step d) of the process according to the invention may advantageously also comprise at least one vacuum distillation in which the liquid hydrocarbon fraction (s) obtained (s) after separation. and / or the atmospheric residue fraction obtained after atmospheric distillation is (are) fractionated by vacuum distillation into at least one vacuum distillate fraction and at least one vacuum residue fraction. Preferably, the separation step d) comprises, first of all, an atmospheric distillation, in which the liquid hydrocarbon fraction (s) obtained after separation is (are) fractionated (s). ) by atmospheric distillation into at least one atmospheric distillate fraction and at least one atmospheric residue fraction, followed by vacuum distillation in which the atmospheric residue fraction obtained after atmospheric distillation is fractionated by vacuum distillation into at least one vacuum distillate fraction and at minus a fraction residue under vacuum. The vacuum distillate fraction typically contains vacuum gas oil fractions. The vacuum distillate fraction can be recovered as a distillate type marine fuel (according to ISO8217) with a very low sulfur content or can be incorporated into a residual type oil pool (according to ISO8217). Advantageously, the vacuum distillate fraction can be sent in a fluidized catalytic cracking process or a fixed bed hydrocracking process.

At least a portion of the atmospheric residue fraction or a portion of the vacuum residue fraction may optionally be recycled to the hydrocracking step c). The atmospheric residue fraction and / or the vacuum residue fraction can be sent to a catalytic cracking process. The atmospheric residue fraction and / or the vacuum residue fraction can be used as fuel oil or as fuel oil base, possibly as a base of low sulfur bunker oil.

Part of the vacuum residue fraction and / or part of the vacuum distillate fraction may be fed into a catalytic cracking or bubbling bed hydrocracking step. According to one variant, this bubbling bed hydrocracking stage is fed at least in part by a heavy liquid fraction coming from a high-temperature high-pressure separator.

According to one particular embodiment, part of the atmospheric distillate fraction and / or vacuum distillate fraction according to the invention can be left in the heavy liquid hydrocarbon fraction so that the viscosity of the mixture is directly that of a desired oil grade, for example 180 or 380 cSt at 50 ° C.

fluxing

The liquid hydrocarbon fractions, in particular the heavy fractions containing the atmospheric residue and / or the vacuum residue, according to the invention may, at least in part, advantageously be used as fuel oil bases or as fuel oil, in particular as a base for bunker oil or as bunker oil with a sediment content (after aging) less than or equal to 0.1% by weight.

By "fuel oil" is meant in the invention a hydrocarbon fraction that can be used as a fuel. By "oil base" is meant in the invention a hydrocarbon fraction which, mixed with other bases, is a fuel oil.

To obtain a fuel oil, the liquid hydrocarbon fractions from step d) can be mixed with one or more fluxing bases selected from the group consisting of light-cutting oils of a catalytic cracking, heavy cutting oils of a catalytic cracking, the residue of a catalytic cracking, a kerosene, a gas oil, a vacuum distillate and / or a decanted oil. Preferably, kerosene, gas oil and / or vacuum distillate produced in the process of the invention will be used.

Example Example 1 (not according to the invention)

The filler is a mixture of atmospheric residues (RA) of Middle Eastern origin. This mixture is characterized by a high amount of metals (100 ppm by weight) and sulfur (4.0% by weight), as well as 7% of [370-].

The hydrotreatment process involves the use of three reactors in fixed beds (R1, R2 and R3) with a downward flow of liquid in which the so-called hydrodemetallation (HDM) and hydrotreatment (HDT) stages take place.

The effluent obtained at the end of these two steps is flash separated to obtain a liquid fraction and a gaseous fraction containing the gases, in particular H 2, H 2 S, NH 3, and C 1 -C 4 hydrocarbons. The liquid fraction is then stripped in a column, then fractionated in an atmospheric column and then a vacuum column in several sections (Bp-350 ° C, 350-520 ° C and 520 ° C +).

The reactor R1 is charged with hydrodemetallization catalyst and the reactors R2, R3 with hydrotreatment catalyst. The process is carried out under a hydrogen partial pressure of 15 MPa, a reactor temperature at the beginning of the cycle of 360 ° C. and at the end of the cycle of 420 ° C.

Table 1 below shows the hourly space velocities (VVH) for each catalytic reactor, and the corresponding average temperatures (WABT) obtained over the entire cycle according to the described operating mode.

These conditions have been set according to the state of the art, for an operating time of 11 months and a HDM rate greater than 90%. Table 1: Operational conditions of the different sections VVH (h-1) WABT (° C) HDM and HDT in Fixed Bed R1 0.50 390 R2 0.50 390 R3 0.50 390 Total 0.17 390

The WABT is an average temperature over the height of the bed and also averaged over time over the duration of a cycle.

The yields obtained according to the non-compliant example are presented in Table 4 for comparison with the yields according to the example in conformity.

Example 2 (in accordance with the invention)

The process according to the invention is carried out in this example with the same filler, the same catalysts, and under the same operating conditions for the reactor R1. The reactor R2 is operated under the same operating conditions but its VVH is larger.

The method according to the invention comprises the use of a new bypassable hydrocracking reactor noted Rc, replacing the reactor R3 which appears in the hydrotreating section (HDT) of the prior art. This hydrocracking step is carried out at high temperature downstream of the hydrodemetallation and hydrotreatment steps in a fixed bed which take place in the reactors R1 and R2.

Table 2 below gives an example of operation of the bypassable reactor Rc. Table 2: Operations around the bypassable reactor according to the invention Fixed bed reactors Bypassable Hydrocracking Reactor sequences HDM / Transition HDT offline HCK 1 R1 R2 - rc 2 R1 R2 rc -

In sequence 1, the effluent obtained at the end of the hydrocracking step is similar in terms of purification to that of Example 1, but is more converted. In sequence 2, the effluent obtained is slightly degraded in terms of purification but similar in terms of conversion.

The reactor Rc of the hydrocracking step is charged with a hydrocracking catalyst.

The process is carried out under a hydrogen partial pressure of 15 MPa, a reactor temperature at the beginning of the cycle of 390 ° C., and at the end of the cycle of 420 ° C.

Once the temperature of 420 ° C reached on the bypass reactor, the reactor Rc is taken offline until the end of the cycle via the use of a bypass to limit the formation of sediment.

Table 3 below shows the hourly space velocity (VVH) for each catalytic reactor and the corresponding average temperatures (WABT) obtained over the entire cycle according to the operating mode described. Table 3: Operational conditions of the different sections VVH (h-1) WABT (° C) HDM and HDT in fixed bed R1 0.50 390 R2 0.40 390 HCK bypass rc 0.67 405 Total 0.17 394

Table 4 below shows the comparison of the yields and hydrogen consumption obtained according to the non-compliant example and according to the example according to the invention. Table 4: Comparison of average yields obtained during the cycle Non-conforming example Conforming example Mean WABT (° C) 390 394 Conso H2 1.67 1.77 returns H2S 3.94 3.94 NH3 0.24 0.24 C1-C4 1.61 1.86 PI-350 ° C 17.9 18.8 350 ° C-520 ° C 40.2 42.1 520 ° C + 37.8 34.9 Total 101.67 101.77

It therefore appears from Tables 2, 3 and 4 that the process according to the invention incorporating a hydrocracking section with a passable reactor Rc, makes it possible to increase the mean WABT of the cycle by + 4 ° C. to VVH overall identical. The WABT is the average temperature of the bed during a cycle.

VVH is the ratio of the volume flow rate of charge to the volume of catalyst contained in the reactor.

According to Table 4, the gain obtained in terms of WABT (+ 4 ° C) results in an increase in the yields of the most valuable sections: +09 points on the section [PI-350 ° C] and + 1.9 points on the cut [350 ° C-520 ° C].

Claims (10)

A continuous process for treating a hydrocarbon feedstock containing at least one hydrocarbon fraction having a sulfur content of at least 0.1% by weight, an initial boiling temperature of at least 340 ° C, and an end temperature boiling point of at least 440 ° C, the process comprising the following steps: a) an optional hydrodemetallization step in which at least two reactive reactors are used at a temperature of between 300 ° C. and 500 ° C., and under an absolute pressure of between 5 MPa and 35 MPa, in the presence of the charge; hydrocarbon and hydrogen, and a hydrodemetallation catalyst, b) a fixed bed hydrotreatment step comprising at least one reactor in which the effluent from step a) when it exists, or directly the hydrocarbon feedstock when step a) does not exist, is brought into contact with at least one hydrotreating catalyst at a temperature of between 300 ° C. and 500 ° C. and under an absolute pressure of between 5 MPa and 35 MPa, c) a fixed-bed hydrocracking step in which at least one passable reactor is carried out at a temperature of between 340 ° C. and 480 ° C., and under an absolute pressure of between 5 MPa and 35 MPa, in the presence of the effluent from step b), and a hydrocracking catalyst, d) a step of separating the effluent from the hydrocracking step c) to obtain at least one gaseous fraction and at least one heavy liquid fraction, said heavy liquid fraction being sent to an atmospheric distillation producing at least one distillate and atmospheric residue, said atmospheric residue being wholly or partly in vacuum distillation producing a vacuum residue, said atmospheric and vacuum residues can be sent to a catalytic cracking process, or be used as fuel oil or as a fuel base. A method of treating a hydrocarbon feedstock according to claim 1, wherein a bypassable reactor of the fixed bed hydrocracking stage is stopped as long as the temperature of said bypassable reactor is between 390 ° C and 430 ° C, and preferably between 405 ° C and 425 ° C. A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrodemetallization step a) is carried out under the following operating conditions: - temperature between 350 ° C and 430 ° C, absolute pressure of between 11 MPa and 26 MPa, preferably between 14 MPa and 20 MPa, WH, (defined as the volumetric flow rate of the feed divided by the total volume of the catalyst), of between 0.1 h ^-1 and 5 h ^-1 , preferably between 0.15 h ^-1 and 3 h ^-1 , and more preferably between 0.2 h ^-1 and 2 h ^-1. A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrodemetallization step a) uses a hydrodemetallization catalyst comprising from 0.5% to 10% by weight nickel, preferably from 1% to 5% by weight. % by weight of nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of molybdenum, preferably from 3% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a mineral support . A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrotreating step b) is carried out at a temperature of between 350 ° C and 430 ° C, and at an absolute pressure of between 11 MPa and 26 MPa preferably between 14 MPa and 20 MPa. A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrotreatment step b) uses a catalyst comprising from 0.5% to 10% by weight nickel, preferably from 1% to 5% by weight nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of molybdenum, preferably from 5% to 20% by weight of molybdenum (expressed as molybdenum MoO3) on a mineral support selected from the group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrocracking step c) is carried out at a temperature of between 350 ° C and 430 ° C, and at an absolute pressure of between 11 MPa and 26 MPa preferably between 14 MPa and 20 MPa. A process for treating a hydrocarbon feedstock according to claim 1, wherein the hydrocracking step c) uses a catalyst comprising from 0.5% to 10% by weight of nickel, preferably from 1% to 5% by weight nickel (expressed as nickel oxide NiO), and from 1% to 30% by weight of molybdenum, preferably from 5% to 20% by weight of molybdenum (expressed as molybdenum oxide MoO3) on a mineral support chosen from group consisting of alumina, silica, silica-aluminas, magnesia, clays and mixtures of at least two of these minerals. Process for treating a hydrocarbon feedstock according to claim 1, wherein the separation step d) comprises at least one atmospheric distillation which makes it possible to obtain at least one atmospheric distillate fraction, and at least one atmospheric residue fraction. Process for treating a hydrocarbon feedstock according to claim 1, wherein the separation step d) comprises at least one vacuum distillation which makes it possible to obtain at least one vacuum distillate fraction and at least one vacuum residue fraction .

Images