BR112014014892B1 - IMPROVED PROCESS OF CONVERSION OF A HEAVY LOAD IN MEDIUM DISTILLATE, APPEALING FOR A PRE-TREATMENT AMOUNT OF THE CATALYTIC CRACKING UNIT - Google Patents

Abstract

improved process of converting a heavy load into medium distillate, calling for pre-treatment upstream of the catalytic cracking unit. the present invention relates to an improved process for converting a heavy load, allowing to improve selectivity in medium distillates. the invention consists in the application of a hydrotreatment or hydroconversion process, known as pre-treatment of the heavy load upstream of the catalytic cracking unit, followed by an oligomerization unit, which allows to increase the sharp production of cuts c3, c4 and light gasoline from the catalytic cracking unit and, therefore, significantly increase the production of medium distillate after the oligomerization step, as well as the selectivity of medium distillate over gasoline.

Description

FIELD OF THE INVENTION

[0001] The invention relates to the feeding of a conversion process in a heavy hydrocarbon cargo, presenting an improved yield in medium distillate. More precisely, the process according to the present invention allows: - to improve the production of medium distillate in relation to the load; - significantly improve the selectivity of medium distillate over gasoline; - obtain C3, C4 cuts and light gasoline with low impurity content, leading to a notable gain on the necessary purification steps, before the oligomerization step or on the life span of the catalysts used in the oligomerization units.

[0002] These improvements are possible, thanks to the use of a hydrotreatment or hydroconversion unit, the pre-treatment unit places the catalytic cracking unit and oligomerization unit upstream of the chain.

[0003] Historically, the catalytic cracking units known under the acronym FCC, short for the Anglo-Saxon terminology "Fluid Catalytic Cracking" (which means catalytic cracking in a fluidized layer) are optimized for the production of light products; liquefied gases (or LPG), light olefins and gasoline, in order to respond either to the market for polymers from the polymerization of light olefins, or to the need for gasoline consumption from car parking.

[0004] In this type of operation, the production of fuel oil bases remains limited. Currently, considering the strong progression of dieselization of car parking, the demand for fuel oil products is greatly increased. As a result, it becomes increasingly necessary to orient the refineries' production towards the production of medium distillates and improving the selectivity of medium distillate over gasoline.

[0005] FCC units, present near a refinery in two, being, on the one hand, the main source of gasoline and, on the other hand, an important source of light olefins, it is imperative to be able to convert these units into units that favor the production of medium distillates.

[0006] Within the scope of the present invention, it is treated by means of a pre-treatment via a hydrotreatment or hydroconversion unit installed upstream of the catalytic cracking unit to obtain a more converting load, allowing to increase the final production in medium distillate from of the set of an FCC unit + oligomerization unit, and improve the selectivity of medium distillate over gasoline.

[0007] Another effect of the present invention is to facilitate the purification of the charge of the oligomerization unit and, therefore, to increase the duration of the catalytic cycle, having charges with reduced content of impurities, such as nitrogen and sulfur. This so-called pre-treatment unit upstream of the FCC set and oligomerization can be a hydroconversion unit or a catalyst hydrotreatment unit for all hydro-refining reactions, such as hydrodesnitrogenation, hydrodesulfurization and aromatics hydrogenation.

[0008] This process allows partial conversion of heavy hydrocarbon charges, whose initial boiling temperature is generally above 340 ° C, under partial pressure of hydrogen, into gasoline and medium distillates and hydrotreat the cuts produced, as well as the heavy unconverted hydrocarbon cargo, which allows reducing the amount of impurities, notably nitrogenous and sulfur compounds.

[0009] The FCC process makes it possible to convert heavy hydrocarbon charges, whose initial boiling temperature is generally above 340 ° C into lighter hydrocarbon fractions, notably a gasoline cut, by cracking the molecules of the heavy charge in the presence of an acid catalyst. The FCC also produces LPG (liquefied petroleum gas) in considerable quantities with high olefin content. In the present invention, the FCC load consists of the unconverted load of the hydro-refining unit.

[00010] The object of the oligomerization process is to oligomerize the olefins in C3 to C12 and can be formed from several disjoint cuts, for example, a C3 to C4 cut and a C5 - 220 ° C gas cut, preferably 160 ° C and , even more preferably, C5 - 120 ° C, alone or in mixture, to obtain a mixture of hydrocarbons of mono-olefins with a number of carbon atoms greater than or equal to 9.

[00011] Typically, from C4 olefins, oligomers are obtained, whose number of carbon atoms is largely less than or equal to 30, and for the most part between 8 and 20.

[00012] The present invention uses a particular chain of units that allow: a) to improve overall production in medium distillate; b) improve the selectivity of medium distillate over gasoline, as well as c) facilitate the purification of the oligomerization unit and increase the duration of the catalytic cycle, with fillers with reduced content in impurities, such as nitrogen, sulfur, as well as in diolefins .

[00013] The invention resides essentially in the installation of a hydrotreatment or hydroconversion unit upstream of the catalytic cracking unit, which allows the overall production of medium distillate to increase.

[00014] This arrangement of units also allows to significantly increase the selectivity of average distillate over gasoline.

[00015] Another notable effect of the invention is that it allows to generate a gasoline cut, originating from catalytic cracking, whose content of impurities, such as nitrogen and sulfur, as well as in diolefins is reduced.

[00016] The cutting of gasoline thus purified makes it possible to limit the purification upstream of the oligomerization unit and increase the hardness of the catalytic cycle.

[00017] The present invention is compatible with all catalytic cracking reactor technologies, whether this is a technology with upward solid gas flow (called anglo-saxon terminology riserna) or a technology with downward flow (called "dropper" or "downer" "in Anglo-Saxon terminology).

[00018] The catalytic cracking unit used in the present process may decline, according to several modalities; with a single reactor or several reactors, each reactor can operate in upward or downward flow.

[00019] In the case of several oligomerization units associated with the catalytic cracking unit, these may be arranged in series or in parallel.

EXAMINATION OF THE PREVIOUS TECHNIQUE

[00020] Patent application FR 2,935,377 refers to a process for converting a hydrocarbon cargo, said to be heavy, with a view to co-producing propylene and gasoline with a minimum yield. The process described in that patent comprises at least two reaction steps, a first catalytic cracking step and a second oligomerization step of C3 and C4 olefins, or C4 olefins, or C4 and C5 olefins, originating from catalytic cracking. A third reaction step of selective olefin hydrogenation may be necessary in certain cases, before oligomerization.

[00021] The process, according to this invention, makes it possible to carry out two types of production corresponding to two different operating cases: • a so-called "maxi propylene" corresponding to a maximum production in propylene, maintaining a minimum gasoline yield, even slightly increased in relation to the potential yield of the catalytic cracking unit alone or; • a so-called "maxi gasoline" operation corresponding to a maximum gasoline production without propylene production.

[00022] WO 03/078547 describes a catalytic cracking process for a main charge at a boiling temperature above 350 ° C and a relatively light secondary charge at a boiling temperature below 320 ° C, that secondary charge being constituted of olefins with at least 8 carbon atoms produced by oligomerization of light olefins with 4 to 5 carbon atoms.

[00023] WO 03/078364 describes a process for producing oligomers, from C4 olefins, these oligomers being subsequently cracked in a catalytic cracking unit, in order to maximize the production of propylene.

[00024] Patent application FR 11 / 01,444 describes an oligomerization unit catalytic cracking chaining process.

[00025] This order describes a process for converting a heavy load, allowing to improve selectivity in medium distillate. The process uses a catalytic cracking unit followed by one or more olefin oligomerization units with a number of carbon atoms ranging from C2 to C12, allowing to preferably produce an additional medium distilled cut. The light part of the oligomerate produced and not incorporable in the middle distillate cut is partly recycled • either in the oligomerization stage to be transformed into medium distillates by reaction with the light olefins of the load, as described in FR patent 2,871,167; • either at the FCC to be cracked into light olefins that return to the oligomerization units in addition to the charge olefins, in order to preferentially form the heavy oligomerates that can be incorporated into the medium distilled cut.

[00026] The present invention consists of the particular chaining of three units, making it possible to significantly improve the production of medium distillate, as well as the selectivity of medium distillate over gasoline, a selectivity currently being sought in a context of oscillation in the order of gasoline for fuel oil.

[00027] The chaining described in the present invention also allows to improve the performances and life durations of the catalyst used on the oligomerization unit, thanks to obtaining a purified FCC gasoline cut, with reduced content of impurities, such as sulfur, nitrogen, as well as in olefins, cut that is then sent in the oligomerization unit, in order to be converted into olefins of higher molecular weight corresponding to a medium distilled cut.

[00028] The process chain, according to the present invention, consists of the use of a hydro-refining unit, such as a mild or severe hydrocracking unit (of which the trade name by the company AXENS is HyC or HyK-HP) , or even hydrotreating in a fixed or boiling layer (whose commercial name by the company AXENS is Hyvahl / HoÜRc) located upstream of a catalytic cracking unit (FCC), followed by one or more oligomerization units treating all or a part only of cuts C3, C4 and total gasoline or light gasoline from the FCC.

[00029] The synergy resulting from the chain, according to the present invention, allows an increase in the total amount of medium distillates produced in relation to a simple chain consisting of a catalytic cracking unit and an oligomerization, as described in the prior art.

[00030] The present chain makes it possible to significantly improve the selectivity of the average distillate over gasoline, as well as obtaining a gasoline cut sent to the purified oligomerization unit, which has an undeniable advantage in terms of performance and life hardness of the catalyst .

BRIEF DESCRIPTION OF THE FIGURES

[00031] Figure 1 represents a scheme of the process, according to the invention, in which the units are noted: (PRET) for pre-treatment; (FCC) for catalytic cracking; (PUR) for the purification unit upstream of the oligomerization; (OLG) for this oligomerization unit; and (HDT) for the hydrotreatment unit of the middle distillate cut from the oligoid derived from the oligomerization.

BRIEF DESCRIPTION OF THE INVENTION

[00032] The invention relates to a process for converting a so-called heavy hydrocarbon charge, that is, a charge consisting of hydrocarbons with a boiling temperature above approximately 340 ° C, in order to improve the production of medium distillate that forms the basis for commercial fuel oil.

[00033] The process, according to the invention, allows to answer three objectives: 1) to increase the production of medium distillate thanks to: - the production of a more converting cargo at the FCC level, which has the advantage of leading to a increased production of olefins in C3, C4 and light gasoline which, once converted into the oligomerization unit, allows to produce more average distillate; - the intrinsic production of medium distillate via the pre-treatment unit; 2) increase significantly the selectivity of average distillate over gasoline; 3) limiting the purification upstream of the oligomerization unit and increasing the duration of the catalytic cycle, thanks to the obtaining of a gasoline cut, originating from catalytic cracking, whose content of impurities, such as nitrogen and sulfur, as well as in diolefins is reduced.

[00034] The process, according to the present invention, can be defined as a production process of medium distillate, from a heavy load (1) of a vacuum diesel type or atmospheric residue, using 4 steps in series: a) a pre-treatment step (PRET) that is carried out in a hydrocracking or hydrotreating unit, allowing to reduce the content of sulfur and nitrogen impurities in the load, as well as its content in diolefins, and which releases a C5-160 ° gasoline cut C (3), a first medium distilled cut (4) of 160 ° C - 360 ° C distillation range and a so-called unconverted part (5) which has roughly the same distillation range as the heavy inlet load; b) a catalytic cracking step (FCC) of this unconverted part (5) from the pre-treatment step (PRET) that produces a dry gas cut (7) that is used as fuel, a C3 cut (8) , a C4 cut (9), a C5 - 160 ° C gas cut (10), and a second medium distillate cut (11), the gas cut (10) being sent in a purification unit (PUR); c) an oligomerization step (OLG) fed by cut C3 8), cut C4 (9) from the catalytic cracking unit and gasoline cut (10 ') from the purification unit (PUR) and which' produces a cut C3 / C4 (14), a C5-160 ° C gasoline cut (15) that joins the gasoline pool, and a third medium distilled cut (16) which is sent to a hydrotreatment unit (HDT); d) a total hydrogenation step (HDT) of the middle distillate cut (16) from the oligomerization step to achieve the specifications of the fuel oil on the market.

[00035] According to a preferred variant of the process, according to the present invention, the pretreatment unit (PRET) is of the soft hydrocracking type and operates under the following conditions: - temperature between 350 ° C and 420 ° C - pressure between 8 and 12 MPa; - WH between 0.3 and 1 h1; - H2 / HC between 300 and 800 L / L; - NiMo, NiCoMo, NiW based catalysts.

[00036] According to another preferred process variant, according to the present invention, the pretreatment unit (PRET) is a hydrotreatment type and operates under the following conditions: - temperature between 350 ° C and 420 ° C - pressure between 4 and 8 MPa; - WH between 0.5 and 2 tr1; - H2 / HC between 150 and 200 L / L; - NiMo, NiCoMo, NiW based catalysts.

[00037] According to a preferred variant of the process, according to the present invention, the catalytic cracking unit (FCC) works under the following conditions: - when the catalytic cracking is done in a single reactor with upward flow, the reactor outlet temperature (ROT) is between 450 ° C and 650 ° C, preferably between 470 ° C and 620 ° C, and the C / O ratio is between 2 and 20, and preferably between 4 and 15; - when the reactor is in a downward flow, the reactor outlet temperature (ROT) is between 480 ° C and 650 ° C, and the C / O ratio is between 10 and 50, preferably between 10 and 30.

[00038] According to a preferred process variant, according to the present invention, the gasoline charge purification unit (PUR) ex FCC comprises distillation fractionation to produce a light fraction depleted in nitrogen compounds and / or an adsorption step on a molecular sieve under the following conditions: - temperature between 20 ° C and 50 ° C - pressure from 500 to 3,000 kPa (5 to 30 bar); - WH between 0.5 and 4 h1 - molecular sieve (for example, Na X or NaY type)

[00039] According to a preferred process variant, according to the present invention, the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 100 ° C and 350 ° C, and preferably included between 150 ° C and 270 ° C - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 4 and 5 MPa; - catalysts based on aluminum silica or alumina - amorphous silica or crystallized zeolite.

[00040] According to another preferred process variant, according to the present invention, the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 180 ° C and 350 ° C, and preferably between 200 ° C and 270 ° C - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, even more preferably between 4 and 5 MPa; - catalysts based on crystallized zeolite in the case of a diesel distillate recovery.

[00041] According to a preferred process variant, according to the present invention, the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 60 ° C and 200 ° C, and preferably included between 80 ° C and 180 ° C, - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 2 and 4 MPa; - catalysts like acid organic resins.

[00042] According to a preferred variant of the process, according to the present invention, the gasoline fraction produced by oligomerization (OLG) is at least partly recycled to the FCC, to maximize the production of medium distillates.

DETAILED DESCRIPTION OF THE INVENTION

[00043] According to the invention, the overall charge to be pretreated contains more than 50% by weight of hydrocarbons, having a boiling point above 340 ° C, and often at least 80% by volume of compounds boiling above 340 ° C. Preferably, these typical charges have a boiling point greater than 340 ° C, and even better than 370 ° C, that is, that 95% of the compounds present in the charge have a boiling point greater than 340 ° C, that is , that 95% of the compounds present in the charge have a boiling point above 340 ° C and even better above 370 ° C.

[00044] The nitrogen content of the treated hydrocarbon charges is usually more than 500 ppm by weight. The sulfur content is generally between 0.01 and 5% by weight.

[00045] The catalytic cracking unit load corresponds to the unconverted part of the pre-treatment unit load. It generally contains more than 50% by weight of hydrocarbons having a boiling point above 340 ° C. This charge contains less impurities such as nitrogenous or sulfur compounds, than the charge to be hydrotreated and it typically has a higher hydrogen content between 11 and 15%.

[00046] The gasoline cut corresponds to the hydrocarbon cut of distillation interval between 50 ° C and 220 ° C, preferably between 50 ° C and 160 ° C.

[00047] The medium distilled cut corresponds to a hydrocarbon cut with a distillation interval between 130 ° C and 380 ° C, preferably between 150 ° C and 370 ° C.

[00048] The slurry cut corresponds to a hydrocarbon cut with a distillation start point above 380 ° C, preferably above 360 ° C.

[00049] The particular conditions of the different stages of the process, according to the invention, are described in more detail below.

1) Pre-treatment step (PRET)

[00050] According to the invention, the pretreatment step can consist of a heavy load hydrotreating unit in a fixed or boiling layer, or of mild or severe hydrocracking, working with the help of hydrotreating or hydrocracking catalysts , classically of the metal sulfide catalysts of groups VI and VIII on supports of alumina or aluminum silica type. Catalysts, including also a zeolite in the support, can be considered.

[00051] When the pretreatment reactions are carried out in a layer fixed to the descending layer, the operating conditions are, in general, chosen at temperatures between 300 ° C and 450 ° C, preferably between 350 and 430 ° C, total pressures of 3 to 30MPa (30 to 300 bariums), preferably between 5 and 18MPa (50 and 180 bariums), hourly volume velocities from 0.1 to 10 h-1, preferably between 0.3 to 5h-1, and hydrogen on hydrocarbons between 200 Nm3 / m3 and 4000 Nm3 / m3, preferably between 300 and 2000 Nm3 / m3.

[00052] These units allow hydrodesulfurization, hydrodesnitrogenation, hydrodesarmatization of the cargo and ensure the conversion of a part of the heavy cargo into recoverable products. This conversion is more important for the hydroconversion unit than for the hydrotreatment unit.

[00053] Pre-treatment is carried out by a catalytic process under strong pressure of hydrogen in a fixed layer or in a boiling layer, using hydrotreating or hydrocracking catalysts.

[00054] The pretreatment section comprises at least one reaction zone containing at least one hydro-refining catalyst which preferably has a strong activity for hydrodesulfurization, hydrodesnitrogenation and hydrogenation of aromatics.

[00055] Pre-treatment catalysts, also called hydro-refining, can be chosen catalysts commonly used in this field. The hydro-refining catalyst may preferably comprise a matrix, at least one electro-dehydrogenating element chosen from the group formed by the elements of the VIB group and the VIII group of the periodic classification.

[00056] The matrix may consist of compounds, used alone or in a mixture, such as alumina, halogenated alumina, silica, aluminum silica, clays (chosen, for example, from natural clay, such as kaolin or bentonite), magnesia, titanium oxide, boron oxide, zirconium, aluminum phosphates, titanium phosphates, zirconium phosphates, coal, aluminates. It is preferred to use matrices containing alumina, in all such forms known to the Technician, and even more preferably alumines, for example, gamma alumina.

[00057] The hydrodehydrogenating element can be chosen from the group formed by the elements of the VIB group and the noble group VII of the periodic classification.

[00058] Preferably, the hydrodehydrogenating element is chosen from the group formed by molybdenum, tungsten, nickel and cobalt.

[00059] Preferably, the hydrodehydrogenating element comprises at least one element of the VIB group and at least one element of the non-noble group VIII. Such a hydrodehydrogenating treatment may, for example, comprise a combination of at least one element of the group VIII (Ni, Co) with at least one element of the group VIB (Mo, W).

[00060] Preferably, the hydro-refining catalyst further comprises at least one doping element deposited on that catalyst and chosen from the group formed by phosphorus, boron and silicon. In particular, the hydro-refining catalyst may comprise, as doping elements, boron and / or silicon, with possibly, in addition, phosphorus.

[00061] The levels of boron, silicon, phosphorus are generally between 0.1 and 20% by weight, preferably 0.1 and 15% by weight, more preferably between 0.1 and 10% by weight.

[00062] The hydro-refining catalyst can advantageously comprise phosphorus.

[00063] This compound provides, among others, two main advantages to the hydro-refining catalyst; a first advantage is that it is easier to prepare this catalyst, especially when impregnating the hydrodehydrogenating element, for example, from solutions based on nickel and molybdenum.

[00064] A second advantage provided by this compound is an increase in the hydrogenation activity of the catalyst.

[00065] In a preferred hydro-refining catalyst, the total concentration in metal oxides of groups VIB and VIII is comprised between 2% (preferably 5%) and 40% by weight, preferably between 3% (preferably, 7%) and 30% by weight, and the weight ratio expressed in metal oxide between metal (or metals) of the VIB group on metal (s) of the group VIII is between 20 and 1.25, preferably between 10 and 2.

[00066] The concentration in phosphorus oxide P2O5 can be less than 15% by weight, preferably less than 10% by weight. Preferred supports are alumina or aluminum silica, containing 5 to 95% SiO2, considered alone or in mixture with a zeolite.

[00067] In another hydro-refining catalyst, comprising boron and / or silicon, preferably boron and silicon, that catalyst also comprises, in% by weight, in relation to the total mass of that catalyst, - from 1 to 99%, of preferably from 10 to 98% and, more preferably, from 15 to 95% of at least one matrix; - from 3 to 60%, preferably from 3 to 45% and more preferably from 3 to 30% of at least one metal in the VIB group; - optionally, from 0 to 30%, preferably from 0 to 25% and, more preferably, from 0 to 20% of at least one group VIII metal; - from 0.1 to 20%, preferably from 0.1 to 15% and, more preferably, - from 0.1 to 10% of boron and / or from 0.1 to 20%, preferably from 0 , 1 to 15% and, more preferably, from 0.1 to 10% of silicon; - optionally from 0 to 20%, preferably from 0.1 to 15% and, more preferably, from 0.1 to 10% of phosphorus; and - optionally from 0 to 20%, preferably from 0.1 to 15% and, more preferably, from 0.1 to 10% of at least one element chosen from the group VIIA, for example, fluorine.

[00068] In another hydro-refining catalyst, this catalyst comprises: - between 1 and 95% by weight (% oxide) of at least one matrix, preferably alumina; - between 5 and 40% by weight (% oxide) of at least one member of the groups VIB and VIII non-noble; - between 0 and 20%, preferably between 0.1 and 20% by weight (% oxide) of at least one promoter element, chosen from phosphorus, boron, silicon; - between 0 and 20% by weight (% oxide) of at least one member of the VIIB group (manganese, for example); - between 0 and 20% by weight (% oxide) of at least one member of the VIIA group (fluorine, chlorine, for example); and - between 0 and 60% by weight (% oxide) of at least one member of the VB group (niobium, for example).

[00069] In general, hydro-refining catalysts are preferred which have the following atomic relationships: - an atomic ratio of group VIII metals / metals of the VIB group ranging from 0 to 1; - when B is present, an atomic B / metals group VIB ratio ranging from 0.01 to 3; - when Si is present, an atomic Si / metals group VIB ratio ranging from 0.01 to 1.5; - when P is present, an atomic P / metals group VIB ratio ranging from 0.01 to 1; and - when at least one element of the VIIA group is present, an atomic relationship of elements of the VIIA group / metals of the VIB group that ranges from 0.01 to 2.

[00070] Hydro-refining catalysts, particularly preferred are NiMo and / or NiW catalysts on alumina or aluminum silica, doped with at least one element included in the group of atoms formed by phosphorus, boron, silicon and fluorine .

[00071] The applicant has also developed these catalysts. Let us cite, for example, patents, such as those described in patents FR2904243, FR2903979, EP1892038.

[00072] In the case where a stronger conversion is desired over the pretreatment stage, hydrocracking catalysts are used. These hydrocracking catalysts must be bifunctional catalysts, having a hydrogenating phase, in order to be able to hydrogenate the aromatics and carry out the balance between the saturated compounds and the corresponding olefins and an acidic phase that allows to promote the hydroisomerization and hydrocracking reactions.

[00073] The acidic function is provided by supports of larger surfaces (usually 100 to 80 m2.g'1) presenting a superficial acidity, such as halogenated aluminas (chlorinated or fluorinated notably), combinations of boron and aluminum oxides , amorphous aluminum silica and zeolites.

[00074] The hydrogenating function is provided either by one or more metals in group VII of the periodic classification of elements, such as iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, or by an association of at least a metal in the VIB group of the periodic classification, such as molybdenum and tungsten and at least one metal in the group VIII.

[00075] The applicant also develops a range of these catalysts. Let us cite, for example, the patents FR 2 819 430, FR 2 846 574, FR 2 875 417, FR 2 863 913, FR 2 795 341 and FR 2 795 342.

[00076] Among the catalysts usable in the pretreatment unit (PRET), according to the invention, the HR 500 series catalysts (HR526, HR538, HR548, HR558, HR562, HR568 and HRK558, for example, can be mentioned) ), HDK700 (HDK766, HDK776, HDK786) or HYK700 (HYK732, HYK752, HYK762, HYK742) marketed by the company AXENS.

[00077] The effluent separation unit of the pretreatment unit generally comprises a primary separation of the gas and liquid effluents, a hydrogen recycling section, as well as distillations for the fractionation of the different liquid cuts.

[00078] At the end of the pretreatment step (PRET), the unconverted cut produced contains significantly less sulfur and nitrogen compounds than if the load had not undergone a pretreatment step and has a higher hydrogen content. These aspects allow to clearly reduce the levels of impurities that will be obtained in the effluents of the FCC stage that is placed downstream.

2) Catalytic cracking step (FCC):

[00079] The catalytic cracking unit comprises a reactor that can be upstream or downstream.

[00080] When catalytic cracking is carried out in a single reactor with upward flow, the reactor outlet temperature (ROT) is between 450 ° C and 650 ° C, preferably between 470 ° C and 620 ° C, and the C / O ratio is between 2 and 20 and, preferably, between 4 and 15.

[00081] When the reactor has a downward flow, the outlet temperature of the content (ROT) is between 480 ° C and 650 ° C, and the C / O ratio is between 10 and 50.

[00082] The used catalyst flow from the FCC reactor is separated from the cracking effluents by any solid gas separation system known to the technician, and regenerated in a dedicated regeneration zone.

[00083] The effluent from the catalytic cracking reactor is sent in a fractionation zone to produce several cuts defined according to the needs of the refiner.

[00084] According to the invention, the catalytic cracking catalyst consists of an alumina, silica or aluminum silica matrix with or without an ultra-stable Y-type zeolite dispersed in that same matrix.

[00085] The addition of an additive based on zeolite ZSM5, with a content of less than 30% by weight of the total catalyst inventory, can also be considered.

[00086] The FCC reactor catalyst is typically made up of medium-diameter particles, usually between 40 and 140 micrometers, and most often between 50 and 120 micrometers.

[00087] The catalytic cracking catalyst contains at least one suitable matrix, such as alumina, silica or aluminum silica with or without the presence of a type Y zeolite dispersed in that matrix.

[00088] The catalyst may comprise, in addition, at least one zeolite which has a selectivity of the form of one of the following types of structures: MEL (for example, ZSM-11), MFI (for example, ZSM-5), NES, EDO, FER, CHA (e.g. SAPO-34), MFS, MWW. It can also comprise one of the following zeolites: NU-85, NU-86, NU-88 and IM-5, which also have form selectivity.

[00089] The advantage of these zeolites that present a shape selectivity is to obtain a better propylene / isobutene selectivity, that is, a higher propylene / isobutene ratio in the cracking effluents.

[00090] The proportion of zeolite that presents a shape selectivity in relation to the total amount of zeolite may vary depending on the loads used and the structure of the products surveyed.

[00091] Often, from 0.1% to 60%, preferably from 0.1 to 40% and, in particular, from 0.1 to 30% by weight of zeolite, have a selectivity of form.

[00092] The zeolite (s) can be dispersed in a matrix based on silica, alumina or aluminum silica, the ratio of zeolite (any confused zeolites) to the weight of the catalyst often being between 0.7 and 80% by weight, preferably between 1 and 50% by weight, and even more preferably between 5 and 40% by weight.

[00093] In the case where several zeolites are used, they can be incorporated in a single matrix or in several different matrices. The zeolite content which presents a selectivity of form in the total inventory is less than 30% by weight.

[00094] The catalyst used in the catalytic cracking reactor can consist of an ultra-stable Y-type zeolite dispersed in an alumina, silica, or aluminum silica matrix, to which is added an additive based on zeolite ZSM5, the amount in crystals of ZSM5 in the total inventory being less than 30% by weight.

[00095] The effluent separation unit of the catalytic cracking reactor (FCC) generally comprises a primary separation of the effluents from the FCC, a compression and fractionation section of the gases, as well as distillations for the fractionation of the different liquid cuts.

[00096] In certain cases, the HCO cut produced at the FCC (noted flow (17) in Figure 1) can be recycled in the pre-treatment unit.

[00097] The olefinic cuts originating from the catalytic cracking consisting of C3, C4 olefins and gasoline with a cut-off point below 220 ° C and, preferably, below 160 ° C, may be formed from several disjoint cuts, such as, for example , a C3 cut and a gasoline cut are sent to one or more oligomerization units.

[00098] At the end of this stage, the gasoline cut produced contains less sulfur and nitrogen compounds than at the end of an FCC alone, while retaining an equivalent olefin content.

[00099] These aspects make it possible to reduce, even avoid, the purifications directly upstream of the oligomerization stage.

3) Purification step (PUR)

[000100] The gasoline cargo to be treated is sent in a purification unit that uses an adsorbent such as a molecular sieve (for example, type Na X or NaY), working under the following operational conditions: - temperature between 20 ° C and 50 ° C - pressure from 500 to 3,000 kPa (5 to 30 bar) - WH between 0.5 and 4 h-1.

[000101] Among the adsorbents usable in the purification unit, metallic oxides, such as alumines, crystallized silicoaluminates such as zeolites (often called molecular sieves) or mixtures of these compounds, can be mentioned.

[000102] Among these compounds, molecular sieves based on faujasite zeolite are preferred.

[000103] An example is the zeolite NaX, for that marketed by the company Axens by the name SBE 13X.

[000104] In a number of cases a simple fractionation can also allow to produce a light fraction depleted in nitrogen compounds and acceptable by the oligomerization section.

4) Oligomerization step (OLG)

[000105] The object of the oligomerization step is to oligomerize the olefins in C3 to C12 and can be formed from several disjoint cuts, such as, for example, a C3 to C4 cut and a gasoline cut C5-160 ° C, alone or in mixture to obtain a mixture of hydrocarbons containing mono-olefins with a majority of carbon atoms greater than or equal to 8.

[000106] Typically, from C4 olefins, oligomers are obtained whose number of carbon atoms is largely less than or equal to 30, and for the most part between 8 and 20.

[000107] Oligomerization is distinguished from polymerization by the addition of a limited number of molecules. The number of molecules added is in the context of the invention comprised between 2 and 10, terminals comprised, preferably between 2 and 5, and even more preferably between 2 and 4.

[000108] Oligomerates may, however, comprise traces of olefins that have been oligomerized with a number of molecules greater than 10. More often, these traces represent less than 5% by weight in relation to the formed oligomers.

[000109] Oligomerization can be carried out in one or more stages, with one or more reactors arranged in parallel or in series, and one or more catalysts.

[000110] The following description of the operational conditions category can be applied to any of the stages and / or to any of the reactors.

[000111] The solid oligomerization catalyst that operates in a heterogeneous phase is chosen from those known in the prior art. The particular conditions of the different process steps, according to the invention, are described in more detail below.

[000112] The oligomerization catalysts used are preferably acid catalysts based on aluminum silica or amorphous alumina-crystallized zeolite silica or resins.

[000113] Among the resins, TA801 marketed by AXENS will preferably be chosen.

[000114] The operating temperature is between 60 ° C and 200 ° C and, preferably, between 80 ° C and 180 ° C.

[000115] The operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 2 and 4 MPa.

[000116] Among the zeolites, preference will be given to those described in patent FR 2 894 85 0.

[000117] The operating temperature is between 100 ° C and 350 ° C and, preferably, between 150 and 270 ° C.

[000118] The operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 4 and 5 MPa.

[000119] A portion of the C5-220 ° C gasoline cut produced by the oligomerization unit, and preferably C5-160 ° C light gasoline can optionally be recycled in the oligomerization reactor to improve the yield in medium distillate.

5) Final hydrogenation step (HDT)

[000120] The final hydrogenation step (HDT) uses partially or totally sulfur catalysts based on Ni or NiMo or CoMo or even Ni CoMo and NiW, supported on a refractory oxide type support (Al, Ti, Si) eventually with one or more promoters (F, P, Ca, Na).

[000121] The invention is explained in more detail by means of Figure 1.

[000122] Charge 1 is introduced with a hydrogen supply 1b in the pretreatment unit (PRET).

[000123] The purpose of this treatment in the presence of hydrogen is to transform the olefins into alkanes; can be performed by any catalyst known to the Technician and under the associated operating conditions. In particular, sulfurized catalysts based on Ni and Mo, such as HR 306, HR 406 or HR 506 marketed by the AXENS company, can be used. These catalysts operate in the gas phase and at a high temperature of 350 - 420 ° C and with a high content of hydrogen.

[000124] Ni and S-based catalysts, such as those in the LD 241, 341 and 541 series, marketed by AXEMNS, operated in liquid phase, but at a lower temperature (150 - 180 °) can also be used and preferred. Ç)

[000125] From the pretreatment unit (PRET), classically extracted in order of increasing molecular weight: - a gasoline cut 3 - a cut called "medium distillates" 4 - an unconverted cut 5.

[000126] The cut 5 is thus sent to the catalytic cracking unit (FCC) where they are extracted in a classical way, in order of increasing molecular weight: - a dry gas cut 7 consisting of hydrogen (H2), methane and possibly ethane , of ethylene; - a C3 8 cut made up of hydrocarbon molecules, containing 3 carbon atoms, rich in propylene - a C4 9 cut made up of hydrocarbon molecules containing 4 carbon atoms, rich in butenes; - a gasoline cut 10 - a cut called "medium distillates" 11 - a cut 12 called "Slurry" that gathers the fuel pool - in certain cases, an HCO cut can be stretched and recycled in the pre-treatment 2.

[000127] The gasoline cut 10 is then optionally purified in a purification unit (PUR).

[000128] The 10 'gasoline cut is then sent with cuts 8 and 9, as a load from the oligomerization unit (OLG).

[000129] From this oligo unit (OLG), 3 cuts are extracted: - a refined cut 14 that corresponds to unconverted olefins and paraffins of the C3 8 and C49 charges; - a gasoline cut 15 corresponding to the paraffins contained in cut 10 'as well as a part of the oligomerates formed from cuts 8 and 9; - a cut of medium distillates corresponding to the heavy oligomerates formed from cuts 8, 9, 10 '.

[000130] The cut of medium distillates is sent to a hydrogenation unit (HDT) in order to meet the specifications.

Examples

[000131] Two examples are provided below to illustrate the improved performance of the process, according to the invention, in relation to the process, according to the prior art.

Example 1 (prior art): FCC + oligo reference case

[000132] This first example constitutes the base case and corresponds to a mono riser FCC unit followed by an oligomerization unit.

[000133] The FCC unit has a capacity of 40,000 BPSDm, either 230 t / hour, (BPSD is the abbreviation for barrels per day), treating a straight run VGO, that is, a cut called vacuum gas oil, directly from the vacuum distillation unit.

[000134] The catalytic cracking unit works with a catalytic system made up of aluminum silica.

Tabela 1: características principais da carga VGO

[000135] The main characteristics of the load, as well as the operating conditions of the FCC unit are presented respectively in Tables 1 and 2 below.

Table 1: main characteristics of the VGO load

Table 2: FCC operating conditions Example 1

[000136] Under these conditions, the yields in relation to the load of the products leaving the catalytic cracking unit are given in table 3.

Table 3: Product yields from the catalytic cracking unit in Example 1.

[000137] The olefin content of PI-160 ° C gasoline is 47.6% by weight and the nitrogen content is 50 ppm by weight.

[000138] The sulfur content is 800 ppm by weight.

[000139] The C3 cut composed mainly of propylene and propane, as well as the C4 cut composed mainly of butenes and butane, as well as the gasoline cut (PI-160 ° C) are then sent to the oligomerization unit.

[000140] Considering the presence of sulfur and nitrogen, a purification section is installed upstream of the oligomerization unit. It consists of a molecular sieve mass NaX, which is arranged in a fixed layer and works at a temperature of 25 ° C with an operating layer and a regenerating layer.

* a temperatura é aumentada gradualmente para manter a atividade do catalisador[000141] The operational conditions of the purification and oligomerization units are shown in table 4.

* the temperature is gradually increased to maintain the catalyst activity

Table 4: Operational conditions of the purification and oligomerization units.

[000142] Under these conditions, the yields of the products obtained in the catalytic cracking and oligomerization unit in relation to the load entering the catalytic cracking unit are given in table 5 below.

TABLE 5: yields of products from the catalytic cracking and oligomerization of Example 1

[000143] The medium distilled cut from the oligomerization is then hydrogenated: the hydrogenation is carried out with a sulfur nickel catalyst (LD 541) at 160 ° C under 5,000kPa (50 bar) of hydrogen, and with a WH of 1.5 h-1 and a flow of hydrogen gas led to a net charge flow of 100 NL / I.

[000144] Sending C3, C4 and gasoline cuts to oligomerization, therefore, increases the yield in medium distillates by 29.3% by weight.

EXAMPLE 2 (according to the invention): chaining a smooth hydrocracking unit, followed by an FCC unit with an oligomerization unit for olefins in C3, C4 and gasoline

[000145] In example 2, the FCC unit works under the same conditions as those described for example 1, but this time the FCC unit is preceded by a smooth hydrocracking unit, powered by the same load as that of example 1, this is, a direct distillation VGO.

[000146] The operating conditions of the smooth hydrocracking unit are shown in table 6

Table 6: Operating conditions of the smooth hydrocracking unit - Example 2

[000147] Under these conditions, yields in relation to the load of the smooth hydrocracking products are given in table 7. Table 7: yields of the products of the smooth hydrocracking unit in example 2

[000148] At the end of the catalytic cracking, the yields of the products in relation to the hydrotreated VGO load evolve as shown in table 8 below.

Table 8: yield of products at the end of the catalytic cracking of example 2

[000149] The olefin content of PI-160 ° C gasoline is 44.0% and the nitrogen content is 20 ppm by weight. The sulfur content is 150 ppm.

[000150] The C3 cut composed mainly of propylene and propane, as well as the C4 cut composed mainly of butenes and butane, as well as the gasoline cut (PI-160 ° C) are then sent to the oligomerization unit.

* a temperatura é aumentada gradualmente para manter a atividade do catalisador.[000151] The purification and oligomerization conditions are given in table 9 below:

* the temperature is gradually increased to maintain the activity of the catalyst.

Table 9: operational conditions of the purification and oligomerization units

[000152] The lower impurity content (nitrogen and sulfur) of the face allows for a very large reduction in the amount of molecular sieve used in the purification unit located upstream of the oligomerization unit, which goes from 22.1 tonnes to 8.8 tonnes .

[000153] The size of the purification unit on a sieve is therefore very small.

[000154] The yields of the products from the smooth hydrocracking, catalytic cracking and oligomerization of the C3 =, C4 =, gasoline cuts in relation to the load entering the smooth hydrocracking unit are given in table 10.

Table 10: yields of products from the smooth hydrocracking and catalytic cracking and oligomerization of example 2

[000155] The cutting of medium distillates is then hydrogenated under the same conditions as in example 1.

[000156] Linking the smooth hydrocracking unit (PRET) and the unit (FCC) with an oligomerization unit (OLG), significantly improves the amount of medium distillates produced.

[000157] In the base case, this production of medium distillates represents 45.0% by weight of the FCC load, against 54.03% by weight in the configuration according to the invention, either an increase of 9.03%.

[000158] The cut of gasoline does not increase due to the pre-treatment and even decreases from 1.30%, going from 33.95% by weight in the base case to 32.65% by weight.

[000159] The selectivity in average distillates in relation to gasoline (average distillates / gasoline ratio) is, therefore, improved, going from 1.32 to 1.65, either a 25% gain in relative weight, which is an improvement in relation to the evolution of the fuel market.

Claims (9)

1. Production process of medium distillate, from a heavy load (1) of a vacuum diesel type or atmospheric residue, characterized by the fact that it uses 4 stages in series: (a) a pretreatment stage (PRET ) which is carried out in a hydrocracking or hydrotreating unit, allowing to reduce the content of sulfur and nitrogen impurities in the load, as well as its content in diolefins, and which releases a C5 - 160 ° C gasoline cut (3), a first cut medium distillate (4) of distillation range 160 ° C - 360 ° C and a so-called unconverted part (5) which has roughly the same distillation range as the heavy inlet charge; (b) a catalytic cracking step (FCC) of this unconverted part (5) from the pre-treatment step (PRET) which produces a so-called dry gas cut (7) that is used as fuel, a C3 cut (8 ), a C4 cut (9), a C5 - 160 ° C gas cut (10), and a second medium distillate cut (11), the gas cut (10) being sent in a purification unit (PUR); (c) an oligomerization step (OLG) fed by cut C3 (8), cut C4 (9) from the catalytic cracking unit and gasoline cut (10 ') from the purification unit (PUR) and which produces a C3 / C4 cut (14), a C5 - 160 ° C (15) gasoline cut that joins the gasoline pool, and a third medium distilled cut (16) which is sent to a hydrotreatment unit (HDT); (d) a total hydrogenation step (HDT) of the middle distillate cut (16) from the oligomerization step to reach the market's fuel oil specifications. 2. Process, according to claim 1, characterized by the fact that the pre-treatment unit (PRET) is a smooth hydrocracking type and operates under the following conditions: - temperature between 350 ° C and 420 ° C - pressure comprised between 8 and 12 MPa; - WH between 0.3 and 1 h1; - H2 / HC between 300 and 800 L / L; - NiMo, NiCoMo, NiW based catalysts. 3. Process, according to claim 1, characterized by the fact that the pre-treatment unit (PRET) is a hydrotreatment type and works under the following conditions: - temperature between 350 ° C and 420 ° C; - pressure between 4 and 8 MPa; - WH between 0.5 and 2 h-1; - H2 / HC between 150 and 200 L / L; - NiMo, NiCoMo, NiW based catalysts. 4. Process according to claim 1, characterized by the fact that the catalytic cracking unit (FCC) works under the following conditions: - when the catalytic cracking is done in a single reactor with upward flow, the reactor outlet temperature ( ROT) is between 450 ° C and 650 ° C, preferably between 470 ° C and 620 ° C, and the C / O ratio is between 2 and 20, and preferably between 4 and 15; - when the reactor is in a downward flow, the reactor outlet temperature (ROT) is between 480 ° C and 650 ° C, and the C / O ratio is between 10 and 50, preferably between 10 and 30. 5. Process according to claim 1, characterized by the fact that the purification unit (PUR) of the gasoline charge ex FCC comprises a fractionation by distillation to produce a light fraction depleted in nitrogen compounds and / or an adsorption step on molecular sieve under the following conditions: - temperature between 20 ° C and 50 ° C; - pressure from 500 to 3,000 kPa (5 to 30 bar); - WH between 0.5 and 4 h’1 - molecular sieve (for example, Na X or NaY type) 6. Process, according to claim 1, characterized by the fact that the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 100 ° C and 350 ° C, and preferably between 150 ° C and 270 ° C - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 4 and 5 MPa; - catalysts based on aluminum silica or alumina - amorphous silica or crystallized zeolite. 7. Process according to claim 1, characterized by the fact that the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 180 ° C and 350 ° C, and preferably between 200 ° C and 270 ° C; - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 4 and 5 MPa; - catalysts based on crystallized zeolite, in the case of a recovery of diesel distillate. 8. Process according to claim 1, characterized by the fact that the gasoline oligomerization unit (OLG) ex FCC operates under the following conditions: - operating temperature is between 60 ° C and 200 ° C, and preferably between 80 ° C and 180 ° C; - operating pressure is between 1 and 10 MPa (1 MPa = 106 Pascals), preferably between 2 and 6 MPa, more preferably between 2 and 4 MPa; - catalysts like acid organic resins. 9. Process according to claims 6 to 8, characterized by the fact that the gasoline fraction (15) produced by the oligomerization is at least partly recycled to the FCC to maximize the production of medium distillates.

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