RU2801941C1 - Combined method for two-stage hydrocracking and hydrotreatment process - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to hydrocracking of hydrocarbon raw materials. A method is described for hydrocracking of hydrocarbon raw materials containing at least 20 vol.%, preferably at least 80 vol.%, of compounds boiling at a temperature above 340°C. In this case, the specified method includes at least following stages: a) hydrocracking of the specified raw materials, carried out in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature from 250°C to 480°C, pressure from 2 to 25 MPa, volumetric velocity from 0.1 to 6 h^-1, and with such an amount of injected hydrogen that the volume ratio of a number of liters of hydrogen to a number of liters of hydrocarbon is from 100 to 2000 l/l, b) separation into gas and liquid of the flow outgoing from the stage a) to obtain a liquid flow and a gas flow containing at least hydrogen, c) direction of the gas flow containing at least hydrogen to a compression stage before its return to at least the hydrocracking stage a), d) fractionation of the liquid flow into at least one flow containing reacted hydrocarbon products having boiling points below 340°C, and an unreacted liquid fraction having a boiling point above 340°C, e) hydrocracking of the specified unreacted liquid fraction from the stage d), carried out in the presence of hydrogen and a hydrocracking catalyst with a hydrogenating function provided by at least one group VIII metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium, and platinum, and/or at least one group VIB metal selected from chromium, molybdenum, and tungsten, alone or in a mixture, and an acidic function provided by aluminosilicate or zeolites, at a temperature from 250°C to 480°C, pressure from 2 to 25 MPa, volumetric velocity from 0.1 to 6 h^-1, and with such an amount of hydrogen injected that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l, f) hydrotreatment of the flow outgoing from the stage e), mixed with liquid hydrocarbon raw materials, containing at least 95 wt.% of compounds boiling at a temperature in the range from 150°C to 400°C, the specified raw material differs from the outgoing flow from the second hydrocracking stage e), wherein the specified hydrotreatment stage f) is carried out in the presence of hydrogen and at least one hydrotreatment catalyst containing at least one amorphous substrate and at least one hydrogenating-dehydrogenating element selected from at least one group VIB base element and at least one group VIII base element, at a temperature from 200°C to 390°C, pressure from 2 to 16 MPa, volumetric velocity from 0.2 to 5 h^-1, and with such an amount of injected hydrogen that the volume ratio of a number of liters of hydrogen to a number of liters of hydrocarbon is from 100 to 2000 l/l.

EFFECT: obtaining a combined method for hydrocracking and hydrotreatment.

15 cl, 8 tbl, 2 ex, 1 dwg

Description

State of the art

Hydrocracking of heavy oil fractions is a key refining process that makes it possible to obtain lighter fractions, such as gasolines, jet fuels and light gas oils, from excess and unsuitable for processing heavy feedstocks, which refiners seek to adapt their products to demand. Some hydrocracking processes also produce a highly refined residue that can be an excellent base for oils or feedstocks that are easily processed, for example, in a catalytic cracker. One of the product streams to which the hydrocracking process is directed is the middle distillate (a fraction that contains a gas oil fraction and a kerosene fraction).

Hydrocracking of vacuum distillates (DSV) makes it possible to obtain light fractions (gas oil, kerosene, naphtha, etc.) that are more valuable than DSV itself. This catalytic process does not convert all of the DSV into light ends. Thus, after fractionation, a more or less significant proportion of the unreacted DSV fraction, called UCO (from the English UnConverted Oil), remains. To increase the conversion, this unreacted fraction can be returned to the inlet of the hydrotreating reactor or to the inlet of the hydrocracking reactor. Return of the unreacted fraction to the inlet of the hydrotreating reactor or to the inlet of the hydrocracking reactor makes it possible to simultaneously increase the conversion, and also makes it possible to increase the selectivity for gas oil and kerosene. Another way to increase conversion while maintaining selectivity is to add a conversion or hydrocracking reactor to the unreacted recycle loop to the high pressure separation section. This reactor and the associated recycle loop form the second hydrocracking stage. Since this reactor is located downstream of the fractionation section, it operates with a low amount of sulfur (H₂S) and a small amount of nitrogen, which allows, if desired, the use of catalysts that are less sensitive to the presence of sulfur, which increases the selectivity of the process.

Indeed, two-stage hydrocracking includes a first stage, the purpose of which, as in the "one-stage" process, is to hydrotreat the feedstock, and also to achieve a feedstock conversion typically of the order of 30-70%. The stream leaving the first stage is then subjected to fractionation (distillation), the purpose of which is to separate the conversion products from the unreacted fraction. In the second stage of the two-stage hydrocracking process, only the fraction of the raw material that has not reacted in the first stage is processed. This separation makes the two-stage hydrocracking process more diesel fuel selective than the one-stage process, at an equivalent overall conversion rate. Indeed, the intermediate separation of the conversion products prevents their excessive cracking to naphtha and gas in the second stage on the hydrocracking catalyst. In addition, it should be noted that the unreacted fraction of the feedstock treated in the second stage usually has a very low content of NH ₃ and organic nitrogen compounds, as a rule, less than 20 v.h./million and even less than 10 w.h./ million

The gas oil hydrodesulphurization process allows reducing the amount of sulfur contained in the gas oil fraction while minimizing the conversion of feedstock into lighter products (gas, naphtha). The feedstock for hydrodesulfurization can consist, for example, of straight run gas oil (in English straight run gasoil) or gas oil from atmospheric fractionation of crude oil, light vacuum gas oil (Light Vacuum Gas Oil in English) or light vacuum distillates, LCO (light cycle gas oil) or distillate from a conversion process (FCC, coker, etc.), a gas oil fraction resulting from biomass conversion (eg esterification), used singly or in a mixture. The hydrogen partial pressure required for this process is lower than the hydrogen partial pressure in hydrocracking. Usually these two processes are implemented separately in the same refinery. However, they are based on very similar process flow diagrams, consisting of a charging furnace, fixed bed reactors, hydrogen recirculation compressors and more or less complex high pressure separation sections.

The invention consists in combining a two-stage hydrocracking process with a gas oil hydrodesulfurization process, using at least a portion of the second hydrocracking stage reactor to desulphurize the gas oil feedstock mixed with unreacted fraction, or UCO.

Research carried out by the present inventors led them to the discovery that co-treatment of a mixture consisting of a stream from the second stage of a two-stage hydrocracking process treating a DSV type feedstock and a gas oil type feedstock in the hydrotreatment stage allows, in comparison with the co-treatment of a VGO type feedstock and raw materials such as gas oil in a mixture directly in a two-stage hydrocracking process:

- limit the cracking of feedstock such as gas oil at the hydrotreatment stage and maximize the selectivity of the process,

- to limit the concentration of nitrogen and sulfur at the stage of hydrotreating of raw materials such as gas oil mixed with the stream from the second stage of hydrocracking, which optimizes this stage,

- in addition to desulphurization of gas oil type feedstock, to reduce the formation of heavy polyaromatic products (HPNA), which allows to reduce the blowdown from the bleed channel of the second stage of hydrocracking and, thus, increase the conversion of the process, and

- in addition to desulphurizing the gas oil type feedstock, to convert the unreacted part from the second hydrocracking stage e), which allows to reduce the amount of catalyst used in said hydrocracking stage e) at the same conversion per pass through the stage consisting of a combination of the second hydrocracking stage e) and step f) hydrotreating.

The method according to the invention also allows, in comparison with specialized two-stage DVS hydrocracking and gas oil hydrodesulfurization processes operating separately:

- reduce the initial investment and catalyst consumption in the second stage e) hydrocracking.

The essence of the invention

The present invention relates to a two-stage vacuum distillate-type hydrocarbon feedstock hydrocracking process in which the entire effluent from a second hydrocracking stage e) is treated in a hydrotreatment stage f) followed by said second hydrocracking stage e) in admixture with a liquid hydrocarbon feedstock of the gas oil type , different from the stream leaving the second hydrocracking stage e).

In particular, the present invention relates to a process for the hydrocracking of hydrocarbon feedstocks containing at least 20 vol%, preferably at least 80 vol% of compounds boiling above 340°C, said process comprising at least the following steps:

a) hydrocracking said feedstock, carried out in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature of 250°C to 480°C, a pressure of 2 to 25 MPa, a space velocity of 0.1 to 6 h ^-1 and at such the amount of hydrogen introduced so that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l,

b) separating the effluent from step a) into gas and liquid to obtain a liquid stream and a gas stream containing at least hydrogen,

c) directing the gas stream containing at least hydrogen to the compression stage before returning it to at least stage a) hydrocracking,

d) fractionating the liquid stream into at least one stream containing reacted hydrocarbon products having boiling points below 340°C and unreacted liquid fraction having a boiling point above 340°C,

e) hydrocracking said unreacted liquid fraction from step d) carried out in the presence of hydrogen and a hydrocracking catalyst at a temperature from 250°C to 480°C, a pressure from 2 to 25 MPa, a space velocity from 0.1 to 6 h ^-1 and at such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l,

f) hydrotreating the effluent from step e) mixed with a liquid hydrocarbon feed containing at least 95% by weight of compounds boiling at a temperature in the range from 150°C to 400°C, wherein said hydrotreating step f) is carried out in the presence of hydrogen and at least one hydrotreating catalyst, at a temperature of 200°C to 390°C, a pressure of 2 to 16 MPa, a space velocity of 0.2 to 5 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of liters hydrogen to liters of hydrocarbon ranged from 100 to 2000 l/l,

An advantage of the present invention is that it provides a process that combines a two-stage hydrocracking process with a gas oil hydrodesulfurization process to limit cracking of the gas oil feedstock in the hydrotreatment stage and maximize process selectivity and middle distillate yields.

- reduce the initial investment and catalyst consumption in the second stage e) hydrocracking.

Another advantage of the present invention is that it provides a process whereby, by co-treating the effluent from the hydrocracking stage e), mixed with a liquid hydrocarbon feedstock of the gas oil type in the hydrotreating stage f), after the hydrocracking stage e), not only to desulfurize liquid hydrocarbon feedstock such as gas oil, but also to convert the unreacted part of the stream from the hydrocracking stage e), which makes it possible to reduce the amount of catalyst used in said hydrocracking stage e) at the same conversion per pass in the stage consisting of a combination of the second hydrocracking stage e) and step f) hydrotreating.

Another advantage of the present invention is that it provides a process which, through said co-treatment, not only desulfurizes liquid hydrocarbon feedstocks such as gas oil, but also reduces the formation of heavy polyaromatics (HPNAs). Indeed, HPNAs are gradually formed as they are returned to the second stage of hydrocracking. The implementation of stage f) hydrotreating after stage e) hydrocracking allows to reduce the accumulation of HPNA due to the hydrogenation of the precursors of these HPNA, ie low molecular weight HPNA.

Another advantage of the present invention is that it provides a process which, by combining the two processes, reduces operating costs and catalyst consumption in the second hydrocracking stage.

Detailed description of the invention

According to the invention, the method includes step a) hydrocracking said feedstock, carried out in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature of 250°C to 480°C, a pressure of 2 to 25 MPa, a space velocity of 0.1 to 6 h ^-1 and with such an amount of introduced hydrogen that the volume ratio of liters of hydrogen to liters of hydrocarbon was from 100 to 2000 l/l.

Operating conditions such as temperature, pressure, hydrogen recycle rate, hourly space velocity can vary greatly depending on the nature of the feedstock, the quality of the desired products and the facilities available to the refinery owner.

Preferably, step a) of the hydrocracking according to the invention is carried out at a temperature of from 320°C to 450°C, very preferably from 330°C to 435°C, at a pressure of 3 to 20 MPa, very preferably from 6 to 20 MPa, a space velocity of 0.2 to 4 h ^-1 , very preferably from 0.3 to 5 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 200 to 2000 l/l.

Such operating conditions, used in step a) of the process according to the invention, generally allow one-pass conversion to products with boiling points below 340° C., more preferably below 370° C., more than 15 wt.%, even more preferably in the range from 20 to 95 wt%.

According to the invention, the hydrocarbon feedstock processed by the method according to the invention and sent to step a) is selected from a hydrocarbon feedstock containing at least 20 vol%, preferably at least 80 vol% of compounds boiling above 340°C, preferably from 370 °C to 580°C (i.e. corresponding to compounds containing at least 15 to 20 carbon atoms).

Said hydrocarbon feedstock may advantageously be selected from vacuum gas oil (VGO) or vacuum distillate (DSV), such as gas oils obtained from the direct distillation of crude oil or conversion units, such as FCC units, cokers or visbreaking, as well as from raw materials originating from aromatic extraction plants from lubricating base oils or from solvent dewaxing of lubricating base oils, or from a distillate formed during the desulfurization or hydroconversion of RAT (atmospheric residues) and / or RSV (vacuum residues), or the feedstock may preferably be deasphalted oil, or a feedstock derived from biomass, or any mixture of the above types of feedstock. The specified list is not restrictive. Generally speaking, said feed has an initial boiling point above 340°C, preferably above 370°C.

Said hydrocarbon feedstock may contain heteroatoms such as sulfur and nitrogen. The nitrogen content is usually from 1 to 8000 ppm, more specifically from 200 to 5000 wpm, and the sulfur content is from 0.01 to 6 wt.%, more often from 0.2 to 5 wt. .% and even more preferably from 0.5 to 4 wt.%.

Said raw material processed by the method according to the invention and sent to step a) may, in certain cases, contain metals. The total content of nickel and vanadium in the raw materials processed by the method according to the invention is preferably less than 1 ppm.

The asphaltene content is typically below 3000 wpm, preferably below 1000 wpm, even more preferably below 200 wpm.

In the case where the feed contains compounds such as tars and/or asphaltenes, it is preferable to first pass the feed through a bed of a catalyst or adsorbent other than a hydrocracking or hydrotreating catalyst.

According to the invention, hydrocracking step a) is carried out in the presence of at least one hydrocracking catalyst. Preferably, the hydrocracking catalyst is selected from classical hydrocracking catalysts known to those skilled in the art.

All hydrocracking catalysts used in hydrocracking processes are bifunctional, combining an acidic function with a hydrogenating function. The acid function is provided by high surface substrates (typically 150-800 m ² /g) having surface acidity, such as halogenated (particularly chlorinated or fluorinated) aluminas, combinations of boron and aluminum oxides, amorphous aluminosilicates and zeolites. The hydrogenating function is provided either by one or more Group VIII metals of the Periodic Table of the Elements, or by a combination of at least one Group VIB metal of the Periodic Table and at least one Group VIII metal.

Preferably, the hydrogenating function of the hydrocracking catalyst or catalysts is provided by at least one Group VIII metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum, preferably from cobalt and nickel, and/or at least one Group VIB metal. selected from chromium, molybdenum and tungsten, alone or in a mixture, and preferably selected from molybdenum and tungsten.

Preferably, the content of the Group VIII metal in the hydrocracking catalyst or catalysts is advantageously between 0.5 and 15% by weight, preferably between 2 and 10% by weight, the percentages being expressed as oxides by weight.

Preferably, the content of the Group VIB metal in the hydrocracking catalyst or catalysts is advantageously between 5 and 25% by weight, preferably between 15 and 22% by weight, the percentages being expressed as weight percent oxides.

The catalyst or catalysts may optionally also contain at least one promoter element deposited on the catalyst and selected from the group consisting of phosphorus, boron and silicon, optionally at least one Group VIIA element (preferably chlorine, fluorine), optionally at least at least one Group VIIB element (preferably manganese) and optionally at least one Group VB element (preferably niobium).

Preferably, the acidic function of the hydrocracking catalyst or catalysts is provided by alumina, aluminosilicate or zeolites, preferably selected from Y zeolites, and preferably aluminosilicate or zeolites.

The preferred catalyst contains and preferably consists of at least one Group VI metal and/or at least one non-noble Group VIII metal and a Y zeolite and an alumina binder.

An even more preferred catalyst contains, and preferably consists of, nickel, molybdenum, zeolite Y, and alumina.

The other catalyst contains and preferably consists of nickel, tungsten and alumina or aluminosilicate.

In step a) of the process according to the invention, the conversion, in the first step, to products having boiling points below 340° C., preferably below 370° C., is greater than 20%, preferably greater than 30% and even more preferably between 30% and 80% and preferably from 40% to 60%.

The hydrocarbon feedstock processed by the process of the invention and sent to step a) can optionally be sent to a hydrotreatment step prior to being subjected to hydrocracking step a) of said process. In the optional hydrotreatment step, said feedstock is successfully desulphurized and denitrogenated.

Preferably, said hydrotreating step is advantageously carried out under classical hydrotreating conditions, in particular in the presence of hydrogen and a hydrotreating catalyst and at a temperature of 200°C to 400°C, a pressure of 2 to 16 MPa, a space velocity of 0.2 to 5 h ^{- 1} and with such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l.

It is possible to successfully use classical hydrotreating catalysts, preferably containing at least one amorphous support and at least one hydrogenating-dehydrogenating element selected from at least one non-noble element of groups VIB and VIII, most often at least one element of group VIB and at least one non-noble element of group VIII.

Preferably, the amorphous support is alumina or aluminosilicate.

Preferred catalysts are selected from NiMo on alumina and NiMo or NiW on aluminosilicate.

The effluent from the hydrotreating step and entering the hydrocracking step a) has a nitrogen content preferably below 300 wpm, preferably below 50 wpm.

In the case where a hydrotreating step is carried out, this hydrotreating step and the hydrocracking step a) can advantageously be carried out in the same reactor or in different reactors. When they are carried out in the same reactor, this reactor contains several layers of catalysts, and the first catalyst layers contain the hydrotreating catalyst or catalysts, and the subsequent catalyst layers contain the hydrocracking catalyst or catalysts.

According to the invention, the method includes step b) separating into gas and liquid the stream leaving step a) to obtain a liquid stream and a gas stream containing at least hydrogen.

Preferably step b) of gas-liquid separation is carried out in a high temperature and high pressure separator operating at 50°C to 450°C, preferably 100°C to 400°C, even more preferably 200°C to 300 °C and the pressure corresponding to the outlet pressure of step a) minus the head loss.

According to the invention, the method includes step c) directing a gas stream containing at least hydrogen to a compression step before returning it to at least hydrocracking step a). This step is necessary so that the gas can be returned upstream, ie to hydrocracking step a) and therefore at a higher pressure.

The gas stream containing at least hydrogen can advantageously be mixed with make-up hydrogen before or after it is introduced into compression step c), preferably via a make-up hydrogen compressor.

In one embodiment, a portion of the gas stream containing at least pressurized hydrogen may also advantageously be sent to hydrocracking and/or f) hydrotreating steps.

According to the invention, the process comprises step d) fractionating the liquid stream leaving step a) into at least one stream containing reacted hydrocarbon products having boiling points below 340°C, preferably below 370°C and preferably below 380°C, and a liquid unreacted fraction having a boiling point above 340°C, preferably above 370°C and preferably above 380°C, also referred to as UCO (from the English "unconverted oil", unconverted oil).

Preferably, said fractionation step d) comprises a first separation step comprising a separation device such as, for example, a separator tank or a stripping column, operating at a pressure of preferably 0.5 to 2 MPa, the purpose of which is to remove hydrogen sulfide (H ₂ S) from at least one hydrocarbon stream obtained in stage a) hydrocracking. The hydrocarbon stream leaving this first separation can preferably be subjected to atmospheric distillation, and in some cases a combination of atmospheric distillation and vacuum distillation. The purpose of distillation is to effect a separation between the converted hydrocarbon products, ie typically products with boiling points below 340°C, preferably below 370°C and preferably below 380°C, and the liquid unreacted fraction (residue) (UCO).

In another embodiment, the fractionation step contains only one atmospheric distillation column.

The reacted hydrocarbon products having boiling points below 340°C, preferably below 370°C and preferably below 380°C are preferably distilled at atmospheric pressure to obtain several converted fractions with boiling points not exceeding 340°C, preferably a light gaseous C1- C4, at least one gasoline fraction and at least one middle distillate fraction (kerosene and gas oil).

The liquid fraction representing the unreacted residue (UCO) containing products whose boiling point is above 340°C, preferably above 370°C and preferably above 380°C, obtained by distillation, at least part, and preferably all, is introduced into the second stage hydrocracking e) the process according to the invention.

The purge can preferably be implemented on the residual liquid fraction to prevent the accumulation of heavy polyaromatic products (HPNA) present in the heavy ends recycle loop. Indeed, HPNAs are gradually formed during their return to the second hydrocracking stage, and the return of these heavy aromatic components to the second hydrocracking stage e) results in an increase in their molecular weight. The presence of HPNA in said recirculation loop ultimately results in a significant head loss. Therefore, purge is necessary to limit the accumulation of these HPNA products.

According to the invention, the method includes step e) hydrocracking said unreacted liquid fraction from step d), possibly purged, carried out in the presence of hydrogen and a hydrocracking catalyst, at a temperature of 250°C to 480°C, a pressure of 2 to 25 MPa, a space velocity of 0.1 to 6 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon was from 100 to 2000 l/l.

Preferably, the hydrocracking step e) according to the invention is carried out at a temperature of 320°C to 450°C, very preferably 330°C to 435°C, a pressure of 3 to 20 MPa, very preferably 9 to 20 MPa, a space velocity of 0 ,2 to 4 h ^-1 , preferably from 0.2 to 3 h ^-1 , and with such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l.

Such operating conditions, applied in step e) of the process according to the invention, generally allow single pass conversions to products having boiling points below 340° C., preferably below 370° C. and more preferably below 380° C., greater than 15% by weight and even more preferably conversions in the range of 20 to 80% by weight. However, the conversion per pass in step e) is kept low to maximize the selectivity of the process for products with boiling points between 150°C and 370°C (middle distillates). The per-pass conversion is limited by using an increased degree of recirculation in the second hydrocracking stage loop. The degree of recirculation is defined as the ratio of the feed rate to stage e) and the feed rate to stage a), preferably this ratio is from 0.2 to 4, preferably from 0.5 to 2.

According to the invention, hydrocracking step e) is carried out in the presence of at least one hydrocracking catalyst. Preferably, the hydrocracking catalyst for the second stage is selected from classical hydrocracking catalysts known to the person skilled in the art. The hydrocracking catalyst used in said step e) may be identical to or different from the catalyst used in step a), preferably different from it.

All hydrocracking catalysts used in hydrocracking processes are bifunctional, combining an acidic function with a hydrogenating function. The acid function is provided by high surface substrates (typically 150-800 m ² /g) having surface acidity, such as halogenated (particularly chlorinated or fluorinated) aluminas, combinations of boron and aluminum oxides, amorphous aluminosilicates and zeolites. The hydrogenating function is provided either by one or more Group VIII metals of the Periodic Table of the Elements, or by a combination of at least one Group VIB metal of the Periodic Table and at least one Group VIII metal.

Preferably, the hydrocracking catalyst or catalysts used in step e) have a hydrogenating function provided by at least one Group VIII metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum, preferably from cobalt and nickel and/or at least one Group VIB metal selected from chromium, molybdenum and tungsten, used alone or in a mixture, preferably molybdenum and tungsten.

Preferably, the content of the Group VIII metal in the hydrocracking catalyst or catalysts is advantageously between 0.5 and 15% by weight, preferably between 2 and 10% by weight, the percentages being expressed as weight percent oxides.

Preferably, the content of the Group VIB metal in the hydrocracking catalyst or catalysts is advantageously between 5 and 25 wt.%, preferably between 15 and 22 wt.%, the percentages being expressed as oxides by weight.

The catalyst or catalysts used in step e) optionally may also include at least one promoter element deposited on the catalyst and selected from the group consisting of phosphorus, boron and silicon, optionally at least one element of group VIIA (preferably chlorine, fluorine ) and optionally at least one Group VIIB element (preferably manganese), optionally at least one Group VB element (preferably niobium).

Preferably, the hydrocracking catalyst or catalysts used in step e) have an acid function provided by alumina, aluminosilicate or zeolites, preferably selected from Y zeolites, preferably aluminosilicate or zeolites.

The preferred catalyst used in step e) contains and preferably consists of at least one Group VI metal and/or at least one non-noble Group VIII metal, Y zeolite and alumina.

An even more preferred catalyst contains, and preferably consists of, nickel, molybdenum, zeolite Y, and alumina.

Another preferred catalyst contains and preferably consists of nickel, tungsten and alumina or aluminosilicate.

According to the invention, the process comprises step f) hydrotreating the effluent from step e), mixed with a liquid hydrocarbon feed containing at least 95% by weight of compounds boiling at a temperature in the range from 150°C to 400°C, preferably from 150°C to 380°C and preferably from 200°C to 380°C.

Thus, the entire effluent from step e) is co-treated in hydrotreating step f) mixed with a different liquid hydrocarbon feed than the effluent from second hydrocracking step e).

Said liquid hydrocarbon feed may preferably be a feed coming from a plant external to the process according to the invention or an internal stream of said process according to the invention, said internal stream being different from said stream leaving the second hydrocracking stage e). Preferably, said liquid hydrocarbon feed is a feed from a plant external to said process of the invention.

Preferably, said liquid hydrocarbon feedstock treated in step f) in admixture with the effluent from step e) is advantageously selected from a liquid hydrocarbon feedstock formed from straight run crude oil, preferably straight run gas oil , light vacuum gas oil (in English Light Vacuum Gas Oil, LVGO) or light vacuum distillates, and from liquid hydrocarbon feedstock from a coking unit (in English coking), preferably coker gas oil, from a light cracking unit (in English visbreaking, visbreaking ), from a steam cracker (in English steam cracking) and / or from a catalytic cracker (in English Fluid Catalytic Cracking), LCO (light Cycle oil) or light gas oils from a catalytic cracker are preferred, and gas oil type feedstock, formed as a result of the conversion of biomass (for example, esterification), and these types of raw materials can be used individually or in a mixture.

Said liquid hydrocarbon feed may also advantageously be a liquid hydrocarbon feed produced in a fluidized bed reformer, such as H-Oil.

The proportion of this other liquid hydrocarbon feed treated in step f) together with the effluent from step e) is between 20 and 80 wt% of the total weight of the liquid mixture at the inlet of hydrotreating step f), preferably between 30 and 70 wt%. and even more preferably from 40 to 60 wt%.

Treatment of the effluent from step e) mixed with said liquid hydrocarbon feedstock in hydrotreating step f) followed by hydrocracking step e) allows, in addition to desulphurization of said liquid hydrocarbon feedstock, the formation of heavy polyaromatic products (HPNA) to be minimized. Reducing the formation of HPNA allows minimizing the necessary purge of the liquid fraction (unreacted UCO residue) from step d) and thereby increasing the overall conversion of the process. The degree of purge corresponding to the ratio of the mass flow rate of the discharge stream to the mass flow rate of the hydrocarbon feedstock entering the process according to the invention is preferably from 0 to 2%.

According to the invention, said step f) is carried out in the presence of hydrogen and at least one hydrotreating catalyst, at a temperature of 200°C to 390°C, a pressure of 2 to 16 MPa, a space velocity of 0.2 to 5 h ^-1 and at such an amount of hydrogen introduced that the volume ratio of liters of hydrogen to liters of hydrocarbon is from 100 to 2000 l/l.

In said step f) classical hydrotreating catalysts can advantageously be used, preferably those containing at least one amorphous support and at least one hydrogenating-dehydrogenating element selected from at least one non-noble element of groups VIB and VIII, preferably at least at least one element of group VIB and at least one non-noble element of group VIII.

Preferably, the amorphous support is alumina or aluminosilicate.

Preferred catalysts are selected from NiMo or CoMo on alumina and NiMo or NiW on aluminosilicate.

Surprisingly, hydrotreating step f) also makes it possible to convert the unreacted portion of the effluent from hydrocracking step e), which makes it possible to reduce the amount of catalyst used in hydrocracking step e) at the same conversion per pass in a step consisting of a combination of hydrocracking step e) and step f) hydrotreating. In addition, the presence of hydrotreating stage f) increases the amount of hydrogen in the unreacted liquid fraction with boiling points above 340°C (UCO) returned to stage e) hydrocracking, which facilitates the conversion of this fraction in said stage e) and thus further reduces the amount of catalyst required at the specified stage (with the same service life).

The hydrocracking step e) and the hydrotreating step f) can advantageously be carried out in the same reactor or in different reactors. When they are carried out in the same reactor, the intermediate introduction of liquid hydrocarbon feedstock is preferably carried out between different catalyst beds. In this case, the reactor contains several layers of catalysts, with the first catalyst layers containing the hydrocracking catalyst or catalysts, and the subsequent catalyst layers containing the hydrotreating catalyst or catalysts.

Stage f) hydrotreating preferably operates at a pressure higher than the pressure of the stream exiting stage a) hydrocracking.

Thus, in a first particular embodiment, at least a portion, and preferably all, of the effluent from hydrotreating step f) can be advantageously recycled to gas-liquid separation step b).

This configuration allows only one compressor to be used on the hydrogen recycle circuit. Indeed, in this case, the return of the gas containing hydrogen to stage f) is provided by the same compressor that returns the gas containing hydrogen to stage a).

In a second particular embodiment, at least a portion, and preferably all, of the effluent from hydrotreating step f) can advantageously be sent to a second gas-liquid separation step to produce a liquid stream and a gas stream containing at least hydrogen.

Preferably, said second gas-liquid separation step is carried out in a high temperature/high pressure separator operating at a pressure and temperature compatible with the outlet temperature and pressure of step f). Said second separation step is preferably carried out at a temperature of 200 to 390° C. and a pressure of 2 to 16 MPa.

In this case, the liquid stream from the second separation stage can preferably be returned to stage e) hydrocracking and/or stage f) hydrotreating.

In one embodiment, the gas stream containing at least hydrogen leaving the second separation stage can be successfully sent to stage c) compression. In this case, the method uses two gas-liquid separators and a single compressor in the hydrogen recycle loop, as well as a single compressor for make-up hydrogen, which reduces the cost of the installation.

Alternatively, the gas stream containing at least hydrogen leaving the second separation stage may be sent to the second compression stage before being returned to stage e) and/or stage f).

Description of the figure

Fig. 1 illustrates one particular embodiment of the invention.

Hydrocarbon feedstock type DSV or VGO (1) is included in hydrocracking section A of stage a) corresponding to the first stage of hydrocracking. Said section may contain one or two hydrocracking reactors R1 and/or R2 (not shown in the figure). The effluent (2) from step a) is sent to the gas-liquid separator B of step b) allowing the separation of the gaseous stream (7) containing hydrogen. The gas stream (7) is sent to recirculation compressor C, where it is mixed with make-up hydrogen stream (11) and then returned to the hydrocracking reactor via line (8).

The liquid stream (3) exiting the separator B is fed into the fractionation column D of step d).

The effluent containing light fractions (10), gasoline fraction (9) and middle distillate fraction (8) corresponding to gas oil and kerosene are separated in a fractionating column. The unreacted liquid fraction is also separated, designated UCO (UnConverted-Oil) (12), which is then sent via line (4) to the second hydrocracking section E of stage e). Said hydrocracking section E contains a hydrocracking reactor R3 (not shown in the figure). Purge (13) is carried out on the stream of unreacted liquid fraction from stage d).

Liquid hydrocarbon feedstock (12) of the gas oil type is introduced downstream of the UCO hydrocracking section E of step e) and processed in the hydrodesulfurization section F of step f) in admixture with the effluent from hydrocracking E, i.e. with hydrocracked UCO (5).

The examples illustrate the invention without limiting its scope.

Examples

Example 1a (comparative): specialized processes

This example is a basic comparison in which the DSV or VGO hydrocracking and gas oil (GO) hydrodesulfurization processes are performed as two separate dedicated processes.

The hydrocracking unit processes vacuum gas oil (VGO) type feedstock and the HDS gas oil unit processes gas oil (GO) type feedstock described in Table 1.

Table 1 Type VGO GO Consumption t/h 49 51 Density t/m ³ 0.92 0.83 PI TBP °C 300 47 PF TBP °C 552 416 S weight.% 2.18 0.68 N h/m 1800 210

PI - boiling point

PF - end boiling point

TBP - True Boiling Point

Basic working conditions

- Gas oil hydrotreating

The GO feed is introduced into the preheat stage, then into the hydrotreating reactor under the following conditions shown in Table 2.

table 2 Reactor HDS GO Temperature °C 336 Partial pressure H ₂ MPa 4 Catalyst CoMo on alumina HR1246 VVH h ^-1 1.04

The catalyst used is a CoMo catalyst on alumina, type HR1246, manufactured by Axens.

Then the HDS gas oil process is carried out, consisting of a heat recovery line, further high pressure separation, including a recirculating compressor and allowing to separate, on the one hand, hydrogen, sulfur and nitrogen compounds, and on the other hand, a desulphurized stream fed to the stripping column to remove hydrogen sulfide and naphtha.

The final gas oil stream has the following properties shown in Table 3.

Table 3 Type GO Consumption t/h 46 Density t/m ³ 0.82 PI TBP °C 151 PF TBP °C 450 S h/m 10.00 N h/m 2

- Two-stage hydrocracking unit

The VGO feed is introduced into the preheat stage, then into the hydrotreating reactor under the following conditions as shown in Table 4.

Table 4 Reactor R1 Temperature °C 385 Partial pressure H ₂ MPa 14 Catalyst CoMo on alumina
HR1058 VVH h ^-1 1.67

The catalyst used is a CoMo catalyst on alumina, type HR1058, manufactured by Axens.

The stream from this reactor is then mixed with a stream of hydrogen for cooling, after which it is introduced into the second hydrocracking reactor R2, operating under the conditions indicated in table 5.

Table 5 Reactor R2 Temperature °C 390 Partial pressure H ₂ MPa 12.5 Catalyst Metal on zeolite
HYK742 VVH h ^-1 3

The catalyst used is a zeolite metal catalyst, type HYK742, manufactured by Axens.

Reactors R1 and R2 form the first stage of hydrocracking, then the stream from reactor R2 is sent to a separation stage consisting of a heat recovery line, further separation at high pressure, including a recirculation compressor and allowing to separate, on the one hand, hydrogen, hydrogen sulfide and ammonia, and on the other hand on the other hand, a stream fed to a stripper column, then an atmospheric fractionation column, to recover concentrated streams of H ₂ S, naphtha, kerosene, gas oil with desired specifications, and a heavy unconverted stream. This heavy unconverted stream is introduced into the preheat stage and then into the R3 hydrocracking reactor forming the second hydrocracking stage. Reactor R3 operates under the conditions indicated in Table 6.

Table 6 Reactor R3 Temperature °C 345 Partial pressure H ₂ MPa 12.5 Catalyst Metal on amorphous aluminosilicate, HDK766 VVH h ^-1 3

The catalyst used is an amorphous aluminosilicate metal catalyst, type HDK766, manufactured by Axens.

The effluent from reactor R3 is then introduced into the high pressure separation stage behind the first hydrocracking stage and recycled. The mass flow rate at the inlet of the reactor R3 is equal to the mass flow rate of VGO feedstock, a purge corresponding to 2 wt.% of the flow rate of VGO feedstock is taken from the bottom of the fractionation column from the crude oil stream.

The distillate fraction obtained in the hydrocracking unit and separated from the fractionation column meets the Euro V specifications, in particular, it contains less than 10 ppm sulphur.

The yield of middle distillates in this process is 85 wt.% with a total conversion of hydrocarbons with a boiling point above 380°C, equal to 98 wt.

The total catalyst volume required for this scheme is 147 m ³ .

Example 1b (comparative): Co-treatment of a DSV feedstock and a gas oil type feedstock in a two-stage hydrocracking process

This example is a basic comparative case in which the reactions of DSV or VGO hydrocracking and gas oil hydrodesulphurization (GO) are carried out in one two-stage hydrocracking process (co-processing of two feedstocks).

The hydrocracking unit processes vacuum distillate (VGO) mixed with gas oil (GO) as feedstock, identical to those used in example 1a). Characteristics of raw materials (VGO) and (GO) are shown in table 1.

Basic working conditions

The mixture of the two feedstocks, VGO and GO, is introduced into the preheat stage and then into the hydrotreating reactor R1 operating under conditions identical to those described in Table 4 for example 1a).

The effluent from reactor R1 is then mixed with a hydrogen stream for cooling and then introduced into a second hydrocracking reactor R2 operating under conditions identical to those used in example 1a) and described in table 5.

Reactors R1 and R2 form the first stage of hydrocracking, then the stream from reactor R2 is sent to a separation stage consisting of a heat recovery line, further separation at high pressure, including a recirculation compressor and allowing to separate, on the one hand, hydrogen, hydrogen sulfide and ammonia, and on the other hand on the other hand, a stripper feed stream, followed by an atmospheric fractionation column, to recover concentrated streams of H ₂ S, naphtha, kerosene, gas oil with desired specifications, and a heavy unconverted stream. This heavy unconverted stream is introduced into the preheat stage and then into the R3 hydrocracking reactor forming the second hydrocracking stage. Reactor R3 operates under the same conditions as used in example 1a) and are described in table 6.

The effluent from reactor R3 is then introduced into the high pressure separation stage behind the first hydrocracking stage and recycled. The mass flow rate at the inlet of the reactor R3 is equal to the mass flow rate of the VGO feed, a purge corresponding to 2 wt.% of the flow rate of the VGO feed is taken from the bottom of the fractionation column from the crude oil stream.

The distillate fraction obtained in the hydrocracking unit and separated from the fractionation column meets the Euro V specifications, in particular, it contains less than 10 ppm sulphur.

The yield of middle distillates in this process is 80 wt.% with a total conversion of hydrocarbons with a boiling point above 380°C, equal to 98 wt.

The total catalyst volume required for this scheme is 110 m ³ .

Example 2 (according to the invention)

This example is a scheme according to the invention, in which the hydrodesulphurization of gas oils is carried out in co-treatment with the stream from the second hydrocracking stage (ie hydrocracked UCO). Thus, this scheme consists of a single two-stage hydrocracking unit (there is no separate gas oil hydrodesulfurization process).

First process step a) is exactly the same as the first step in Example 1. Reactors R1 and R2 are operated with the same pure VGO or DSV feed described in Table 1 under the same operating conditions as shown in Tables 4 and 5.

The effluent from the R2 reactor is then sent to a separation stage b) consisting of a heat recovery line, then a high pressure separation including a recirculation compressor (stage c), which makes it possible to separate, on the one hand, hydrogen, hydrogen sulfide and ammonia, and on the other hand on the other hand, the stream fed to the stripper and then to the atmospheric fractionation column (stage d) to separate concentrated streams of H ₂ S, naphtha, gas oil kerosene with the desired specification and unreacted heavy liquid fraction (UCO) having a boiling point above 380 ° C. This unconverted heavy stream is introduced into the preheat stage and then into the hydrocracking reactor R3 forming the second hydrocracking stage e). This reactor is operated under the following conditions listed in Table 7.

Table 7 Reactor R3 Temperature °C 345 Partial pressure H ₂ MPa 13 Catalyst Metal on amorphous aluminosilicate HDK766 VVH h ^-1 2.8

The catalyst used is an amorphous aluminosilicate metal catalyst, type HDK766, manufactured by Axens.

The R3 reactor stream is then mixed with a GO feed identical to that used in Example 1 and described in Table 1. This GO feed is preheated in a manner known to those skilled in the art by thermal integration with another process stream. The mixture of reactor stream R3 and GO feedstock is then introduced into the hydrotreating reactor R4 (step f), the purpose of which is to desulfurize the GO feedstock. The operating conditions in this reactor are shown in Table 8.

Table 8 Reactor R4 Temperature °C 385 Partial pressure H ₂ MPa 12.5 Catalyst NiMo on alumina
HR1058 VVH h ^-1 5.4

The catalyst used is a NiMo catalyst on alumina, type HR1058, manufactured by Axens.

The effluent from reactor R4 (stage f) is then introduced into the high pressure separation stage b) after the first hydrocracking stage a) and recycled. The mass flow rate at the inlet of the reactor R3 is equal to the mass flow rate of VGO feedstock, a purge corresponding to 1 wt.% of the flow rate of VGO feedstock is taken from the bottom of the fractionation column from the crude oil stream.

The resulting distillate fraction recovered from the fractionation column complies with the Euro V specifications, in particular it contains less than 10 ppm sulphur.

The yield of middle distillates in this process is 85 wt.% with a total conversion of hydrocarbons with a boiling point above 380°C, equal to 99 wt.

The total catalyst volume required for this scheme is 78 m ³ .

Surprisingly, the use of the R4 reactor in step f) under the indicated operating conditions allows, compared to the dedicated processes in example 1a):

- reduce the initial investment and catalyst consumption in the second stage e) of hydrocracking, which translates into a decrease in the total volume of catalyst required for the entire process,

and, compared to the co-processing of DVS feedstock and GO feedstock in a two-stage hydrocracking process allows:

- reduce the cracking of feedstock such as gas oil at the hydrotreatment stage, which is reflected in an increase in the yield of middle distillates,

- in addition to desulphurization of the gas oil type feedstock, to minimize the formation of heavy polyaromatic products (HPNA), which translates into a decrease in blowdown through the bleed channel of the second stage of hydrocracking and, therefore, in an increase in process conversion, and

- in addition to desulphurizing the gas oil type feedstock, convert the unreacted part leaving the second hydrocracking stage e), which results in a reduction in the amount of catalyst used in said hydrocracking stage e) at the same conversion per pass in the stage combining the second hydrocracking stage e) and step f) hydrotreating.

Claims (21)

1. A method for hydrocracking hydrocarbon feedstock containing at least 20 vol.%, preferably at least 80 vol.% compounds boiling at temperatures above 340°C, and this method includes at least the following stages: a) hydrocracking said feedstock, carried out in the presence of hydrogen and at least one hydrocracking catalyst, at a temperature of 250°C to 480°C, a pressure of 2 to 25 MPa, a space velocity of 0.1 to 6 h ^-1 and at such the amount of hydrogen introduced so that the volume ratio of the number of liters of hydrogen to the number of liters of hydrocarbon is from 100 to 2000 l/l, b) separating the effluent from step a) into gas and liquid to obtain a liquid stream and a gas stream containing at least hydrogen, c) directing the gas stream containing at least hydrogen to the compression stage before returning it to at least stage a) hydrocracking, d) fractionating the liquid stream into at least one stream containing reacted hydrocarbon products having boiling points below 340°C and unreacted liquid fraction having a boiling point above 340°C, e) hydrocracking said unreacted liquid fraction from step d) in the presence of hydrogen and a hydrocracking catalyst with a hydrogenating function provided by at least one Group VIII metal selected from iron, cobalt, nickel, ruthenium, rhodium, palladium and platinum, and/ or at least one Group VIB metal selected from chromium, molybdenum and tungsten, alone or in a mixture, and an acid function provided by aluminosilicate or zeolites, at a temperature of 250°C to 480°C, a pressure of 2 to 25 MPa, by volume speed from 0.1 to 6 h ^-1 and with such an amount of injected hydrogen that the volume ratio of liters of hydrogen to liters of hydrocarbon was from 100 to 2000 l/l, f) hydrotreating the effluent from step e), mixed with a liquid hydrocarbon feed containing at least 95 wt.% compounds boiling at a temperature in the range from 150°C to 400°C, said feed is different from the effluent from the second hydrocracking step e), wherein said hydrotreating step f) is carried out in the presence of hydrogen and at least one hydrotreating catalyst containing at least one amorphous support and at least one hydrogenating-dehydrogenating element selected from at least one non-noble element of group VIB and at least one non-noble element of group VIII, at a temperature from 200°C to 390°C, a pressure from 2 to 16 MPa, a space velocity from 0.2 to 5 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of the amount liters of hydrogen to the number of liters of hydrocarbon ranged from 100 to 2000 l/l. 2. The method according to p. 1, and the hydrocarbon feed processed by this method and sent to stage a) is selected from hydrocarbon feed containing at least 80 vol.% of compounds boiling in the temperature range from 370°C to 580°C. 3. The method according to one of paragraphs. 1 or 2, wherein the hydrocarbon feedstock treated in this manner and sent to step a) is selected from vacuum distillates (DSV) selected from straight-run crude oil gas oils or from conversion plants, and from distillates formed from the desulfurization or hydroconversion of atmospheric residues and/or vacuum residues, deasphalted oils, and raw materials derived from biomass, or from any mixture of the above raw materials. 4. The method according to one of paragraphs. 1-3, and stage a) hydrocracking is carried out at a temperature of from 320°C to 450°C, a pressure of 3 to 20 MPa, a space velocity of 0.2 to 4 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of the amount liters of hydrogen to the number of liters of hydrocarbon ranged from 200 to 2000 l/l. 5. The method according to one of paragraphs. 1-4, moreover, the specified hydrocarbon feedstock processed by the specified method, before being sent to the specified stage a) of hydrocracking, is sent to the hydrotreating stage, and the specified hydrotreating stage is carried out in the presence of hydrogen and a hydrotreating catalyst and at a temperature from 200°C to 400°C, pressure from 2 to 16 MPa, space velocity from 0.2 to 5 h ^-1 and with such an amount of introduced hydrogen that the volume ratio of the number of liters of hydrogen to the number of liters of hydrocarbon was from 100 to 2000 l/l. 6. The method according to one of paragraphs. 1-5, and the method includes stage d) fractionating the liquid stream leaving stage a), at least one stream containing the reacted hydrocarbon products having boiling points below 380°C, and the unreacted liquid fraction having a boiling point above 380 °C. 7. The method according to one of paragraphs. 1-6, wherein the purge is carried out on the unreacted liquid fraction having a boiling point above 340°C. 8. The method according to one of paragraphs. 1-7, and stage e) of hydrocracking is carried out at a temperature of from 320°C to 450°C, a pressure of 3 to 20 MPa, a space velocity of 0.2 to 4 h ^-1 and with such an amount of hydrogen introduced that the volume ratio of the amount liters of hydrogen to the number of liters of hydrocarbon ranged from 200 and 2000 l/l. 9. The method according to one of paragraphs. 1-8, wherein the liquid hydrocarbon feed used in step e) contains at least 95% by weight of compounds boiling at a temperature in the range of 150°C to 380°C. 10. The method according to one of paragraphs. 1-9, said liquid hydrocarbon feed being processed in step f) mixed with the effluent from step e) is selected from straight run gas oil, light vacuum gas oil (LVGO) or light vacuum distillates and liquid hydrocarbon raw materials coming from a coking unit (coking in English), preferably coking gas oil, from a light cracking unit (visbreaking, in English visbreaking), a steam cracking unit (in English steam cracking) and / or from a catalytic cracking unit (in English English Fluid Catalytic Cracking), preferred are LCO (light cycle oil, light cycle oil) or light gas oils coming from a catalytic cracker, and gas oil type feedstock formed as a result of biomass conversion. 11. The method according to one of paragraphs. 1-10, wherein at least a portion of the effluent from hydrotreating step f) is recycled to gas-liquid separation step b). 12. The method according to one of paragraphs. 1-10, wherein at least a portion of the total effluent from hydrotreating step f) is sent to a second gas-liquid separation stage to produce a liquid stream and a gas stream containing at least hydrogen. 13. Process according to claim 12, wherein the liquid stream leaving the second separation stage is recycled to hydrocracking stage e) and/or hydrotreating stage f). 14. The method according to one of paragraphs. 12 or 13, wherein the gas stream containing at least hydrogen leaving the second separation stage is sent to compression stage c). 15. The method according to one of paragraphs. 12 or 13, wherein the gas stream containing at least hydrogen leaving the second separation stage can be sent to the second compression stage before being returned to stage e) and/or stage f).

Images