TW201333180A - Improved process for converting a heavy feed into middle distillate using a pre-treatment upstream of the catalytic cracking unit - Google Patents

Abstract

The present invention describes an improved process for the conversion of a heavy feed that can be used to improve the selectivity for middle distillates. The invention consists of carrying out a hydrotreatment or hydroconversion process termed a pre-treatment of the heavy feed upstream of the assembly of the catalytic cracking unit followed by an oligomerization unit, which can be used to increase the net production of C3, C4 and light gasoline cuts obtained from the catalytic cracking unit, and as a consequence of very significantly increasing the production of middle distillate after the oligomerization step, as well as the selectivity for middle distillates over gasoline.

Description

Improved method for converting heavy feed to middle distillate using pretreatment upstream of the catalyst cracking unit

This invention relates to a process for improving the conversion of heavy hydrocarbon feeds to improve middle distillate yields. More precisely, the process of the invention can be used to: • improve the production of the middle distillate with respect to the feed; • substantially improve the selectivity of the middle distillate relative to gasoline; • obtain C3, C4 and light weight with low impurity content The gasoline fraction provides a substantial gain on the purification steps required prior to the oligomerization step or on the useful life of the catalyst employed in the oligomerization unit.

Such improvements can be achieved by means of a hydrotreating or hydroconversion unit (referred to as a pretreatment unit) placed upstream of the series of catalyst cracking units and oligomerization units.

In the past, optimized catalyst cracking units (known by the acronym FCC (Fluid Catalyst Cracking)) to produce light products, liquefied gases (or LPG), light olefins and gasoline to meet the polymerization obtained from the polymerization of light olefins The market or meet the gasoline consumption needs of the automotive industry.

In this type of function, the production of gas-to-liquids is always limited. Currently, given the significant development of diesel applications in the automotive industry, the demand for gas-based oil products has increased significantly. Therefore, there is an increasing need to locate in refineries that tend to produce middle distillates for production and to improve the selectivity of middle distillates relative to gasoline.

The FCC unit is present in almost half of the refineries, which on the one hand is the main source of gasoline and on the other hand is an important source of light olefins, and it is therefore important to be able to convert these units into a tendency to produce middle distillates. unit.

The context of the present invention relates to pretreatment via a hydrotreating or hydroconversion unit placed upstream of a catalytic cracking unit, which results in a more readily convertible feed which can be used to increase the total obtained from the FCC unit + oligomer unit The final throughput of the fraction and the selectivity of the middle distillate relative to gasoline.

Another effect of the present invention is to facilitate purification of the feedstock for the oligomerization unit and thereby increase the duration of the catalyst cycle by providing a feed having a lower impurity content (e.g., nitrogen or sulfur). The upstream of the "pretreatment" unit of the FCC and oligomerization can be a heavy feed hydroconversion or hydrotreating unit, which can perform all hydrofining reactions of aromatic compounds under high hydrogen pressure and in the presence of a catalyst. For example, hydrogenation, dehydrogenation, and hydrogenation.

The process can be used to partially convert a heavy hydrocarbon feed having an initial boiling point generally above 340 ° C into a gasoline and middle distillate under hydrostatic partial pressure and a hydrotreated feed fraction and an unconverted heavy hydrocarbon feed. This means that the amount of impurities, in particular nitrogen and sulfur compounds, can be reduced.

The heavy hydrocarbon feed having an initial boiling point typically above 340 °C can be converted to a lighter hydrocarbon portion, in particular a gasoline fraction, by the FCC process by cracking the heavy feed molecules in the presence of an acid catalyst. FCC also produces a large amount of LPG (liquefied petroleum gas) with a high olefin content. In the present invention, the FCC feed is comprised of unconverted feed from the hydrofinishing unit.

The purpose of the oligomerization process is oligomeric C3 to C12 olefins (which may be formed by several different fractions, for example, a C3 to C4 fraction and a C5-220 °C gasoline fraction, preferably 160 ° C and more preferably C5- 120 ° C, either alone or in the form of a mixture) to obtain a hydrocarbon mixture containing a monoolefin (mainly containing 9 or more carbon atoms).

Typically, starting from a C4 olefin, an oligomer containing predominantly 30 or fewer carbon atoms (mostly between 8 and 20) is obtained.

The present invention employs a combination of specific units that can be used to: a) improve overall middle distillate production; b) improve the selectivity of the middle distillate relative to gasoline; and: c) provide a smaller amount of impurities (eg, nitrogen) Feeds of sulfur, or even diolefins, to promote purification of the oligomerization unit and increase the catalyst cycle.

The present invention is primarily directed to providing a hydrotreating or hydroconversion unit upstream of a catalyst cracking unit that can be used to increase the overall throughput of the middle distillate.

This unit configuration can also be used to significantly increase the selectivity of the middle distillate relative to gasoline.

Another outstanding effect of the present invention is that it can be used to produce gasoline fractions having reduced amounts of impurities (e.g., nitrogen and sulfur and diolefins) obtained by catalyst cracking.

The thus purified gasoline fraction can be used to limit purification upstream of the oligomerization unit and increase catalyst cycle time.

The present invention is compatible with all catalyst cleavage reactor technologies, whether they are riser or dropper types.

The catalyst cleavage unit employed in the process of the invention can be divided into several embodiments having a single reactor or a plurality of reactors, each of which can operate in a riser or dropper mode.

Where a plurality of oligomeric units are coupled to a catalytic cracking unit, the units may be arranged in series or in parallel.

Patent application FR 2 935 377 relates to a process for converting hydrocarbon feeds (referred to as heavy feeds) to produce a minimum yield of propylene and gasoline. The process set forth in this patent comprises at least two reaction steps, the first step being for catalyst cracking and the second step being for the C3 and C4 olefins or C4 olefins or C4 and C5 olefins obtained by catalyst cleavage. Gather. In some cases, a third reaction step for selective hydrogenation of the olefin may be required prior to oligomerization.

The inventive method can be used to implement two types of production corresponding to two different market scenarios: a "maximum propylene" scenario, which corresponds to maximizing the production of propylene while maintaining a minimum gasoline yield, or even from a separate source. The potential yield of the catalyst cracking unit is slightly increased compared to; or the "maxi gasoline" scenario, which corresponds to maximizing gasoline production and not producing propylene.

Patent WO 03/078547 describes a process for the catalyst to cleave a main feed having a boiling point above 350 ° C and a second relatively light feed having a boiling point of less than 320 ° C. The secondary feed consists of an olefin having at least 8 carbon atoms. It is produced by oligomerizing a light olefin having 4 or 5 carbon atoms.

Patent WO 03/078364 describes a process for the production of oligomers from C4 olefins which are subsequently cleaved in a catalyst cracking unit to maximize the production of propylene.

Patent application FR 11/01444 describes catalyst cleavage/oligomer unit tandem.

This application describes a method of converting a heavy feed which can be used to improve the selectivity to the middle distillate. The method uses a catalyst cleavage unit followed by one or more units for oligomerizing olefins having from 2 to 12 carbon atoms. This means that an additional middle distillate can be preferentially produced. Partially recycling the light fraction of the oligomeric product produced which is not incorporated into the middle distillate: • recycled to the oligomerization step for conversion to a middle distillate by reaction with the light olefin of the feed, As described in the patent FR 2 871 167; or recycled to the FCC for cracking into light olefins, these light olefins can be returned to the oligomerization unit as a supplement to the feed olefins for preferential formation. Heavy oligomeric product in the middle distillate.

The present invention consists of a specific series of three units which can be used to significantly improve the throughput of the middle distillate and the selectivity of the middle distillate relative to gasoline, which is currently in the context of demand changes from gasoline to gas oil. Medium high expectations.

The tandem illustrated in the present invention can also be used to improve the performance and service life of the catalyst used in the oligomerization unit by producing a purified gasoline fraction having a relatively small amount of impurities (e.g., sulfur, nitrogen, and diolefin) from the FCC. The fraction is then passed to an oligomerization unit for conversion to an olefin having a higher molecular weight corresponding to the middle distillate.

The splicing of the process of the invention consists of the use of a hydrotreating unit upstream of the catalytic cracking unit (FCC), such as a mild or intense hydrocracking unit (the commercial name of the unit given by AXENS is HyC or HyK) -HP) or fixed bed or bubbling bed hydrotreating (AXENS gives this unit the commercial name Hyvahl/Hoil _DC /Hoil _RC ) followed by one or more oligomerization units for processing all or only from the FCC A portion of the C3, C4 fraction and all gasoline or light gasoline fractions.

The synergistic effect of the cascade of the present invention can be used to increase the total amount of middle distillate produced as compared to simple concatenation consisting of a catalyst cleavage unit and an oligomerization unit as set forth in the prior art.

The series connection of the present invention can be used to substantially substantially improve the selectivity of the middle distillate relative to gasoline and to obtain a purified gasoline fraction that is delivered to the oligomerization unit; this can undoubtedly contribute to the performance and lifetime of the catalyst.

The present invention relates to a process for converting a hydrocarbon feedstock (referred to as a heavy feedstock, i.e., a feedstock comprising hydrocarbons having a boiling point above about 340 °C) which improves the middle distillate which forms the basis of the commercial gas oil. Production.

The following three objectives can be achieved using the process of the invention: 1) increasing the production of middle distillates by: • producing feeds that can be converted to a greater extent in the FCC, which have the advantage of producing more C3, C4 olefins And light gasoline, which can be used to produce more middle distillates after conversion in the oligomerization unit; ● inherently produce a middle distillate via the pretreatment unit; 2) extremely significantly increase the selectivity of the middle distillate relative to gasoline 3) Limiting the purification upstream of the oligomerization unit and increasing the catalyst cycle time by obtaining a gasoline fraction obtained from the cleavage of the catalyst and having an impurity content of nitrogen and sulfur and a reduced diolefin content.

The process according to the invention can be defined as a process for producing a middle distillate from a vacuum gas oil or an atmospheric feed oil type heavy feed (1) using 4 consecutive steps: - a) a pretreatment step (PRET), which is carried out Implemented in a hydrocracking or hydrotreating unit to reduce the amount of sulfur and nitrogenous impurities in the feed and its diene a hydrocarbon content, and which delivers a C5-160 ° C gasoline fraction (3), a first middle fraction (4) having a distillation range of 160 ° C to 360 ° C, and a portion having substantially the same distillation range as the introduction of the heavy feed ( The unconverted portion (5)); - b) the catalyst cleavage (FCC) step of the unconverted portion (5) obtained from the pretreatment step (PRET), which produces a fraction for use as a fuel (referred to as drying) Gas fraction (7)), C3 fraction (8), C4 fraction (9), C5-160 °C gasoline fraction (10) and second middle fraction (11), gasoline fraction (10) transport To the purification unit (PUR); - c) an oligomerization step (OLG) in which the C3 fraction (8), the C4 fraction (9) obtained from the catalytic cracking unit, and the gasoline obtained from the purification unit (PUR) are supplied a fraction (10') which produces a C3/C4 fraction (14), a C5-160 °C gasoline fraction (15) which enters the gasoline pool, and a third middle fraction (16) which is delivered to the addition Hydrogen Treatment Unit (HDT)); - d) The step of fully hydrogenating (HDT) the middle distillate (16) obtained from the oligomerization step to meet market specifications for gas oils.

In a preferred variant of the process of the invention, the pretreatment unit (PRET) mitigates the hydrocracking type and operates under the following conditions: • a temperature in the range of 350 ° C to 420 ° C; • a pressure in the range of 8 MPa to 12 MPa Within the range; ●HSV is in the range of 0.3 h ^-1 to 1 h ^-1 ; ●H ₂ /HC is in the range of 300 L/L to 800 L/L; ●The catalyst is based on NiMo, NiCoMo, NiW.

In a further preferred variant of the process according to the invention, the pretreatment unit (PRET) is of the hydrotreating type and operates under the following conditions: • a temperature in the range from 350 ° C to 420 ° C; • a pressure in the range from 4 MPa to 8 Within the range of MPa; ●HSV is in the range of 0.5 h ^-1 to 2 h ^-1 ; ●H ₂ /HC is in the range of 150 L/L to 200 L/L; ●The catalyst is based on NiMo, CoMo, NiCoMo .

In a preferred variant of the process of the invention, the catalyst cracking unit (FCC) operates under the following conditions: • When the catalyst cracking is carried out in a single riser reactor, the reactor outlet temperature (ROT) is between 450 ° C and 650. Within the range of °C, preferably in the range of 470 ° C to 620 ° C, and the C / O ratio is in the range of 2 to 20, preferably in the range of 4 to 15; ● in the reactor system of the dropper reactor The reactor outlet temperature (ROT) is in the range of 480 ° C to 650 ° C, and the C/O ratio is in the range of 10 to 50, preferably in the range of 10 to 30.

In a preferred variant of the process of the invention, the purification unit (PUR) of the ex FCC gasoline feed comprises fractional distillation by a distillation step to produce a light fraction of the nitrogen-containing compound depletion, and/or inclusion on the molecular sieve under the following conditions Lower adsorption step: ● temperature in the range of 20 ° C to 50 ° C; ● pressure in the range of 5 to 30 bar; ● HSV in the range of 0.5 h ^-1 to 4 h ^-1 ; ● molecular sieve (such as NaX Or NaY type).

In a preferred variant of the process of the invention, the unit of oligomeric (OLG) ex FCC gasoline operates under the following conditions: - operating temperature in the range of from 100 ° C to 350 ° C, preferably in the range of from 150 ° C to 270 ° C ● Operating pressure in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 4 MPa to 5 MPa; It is based on ceria-alumina or amorphous ceria-alumina or crystalline zeolite.

In another preferred variation of the method of the invention, the unit of oligomeric (OLG) ex FCC gasoline operates under the following conditions: • operating temperature in the range of from 180 ° C to 350 ° C, preferably from 200 ° C to 270 ° C Within the range; ● operating pressure in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 4 MPa to 5 MPa; In the case where the fraction is upgraded to diesel, the catalyst is based on crystalline zeolite.

In a preferred variant of the process of the invention, the unit of oligomeric (OLG) ex FCC gasoline operates under the following conditions: • the operating temperature is in the range of from 60 ° C to 200 ° C, preferably in the range of from 80 ° C to 180 ° C. ● Operating pressure in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 2 MPa to 4 MPa; ● Catalyst It is an organic acid resin type.

In a preferred variant of the process of the invention, the gasoline fraction (15) produced by oligomerization (OLG) is at least partially recycled to the FCC unit to maximize the production of the middle distillate.

According to the invention, the overall feed to be pretreated contains more than 50% by weight of hydrocarbons having a boiling point above 340 ° C and typically at least 80% by volume boiling above 340 ° C. Preferably, the typical feeds have a boiling point above 340 ° C and more preferably above 370 ° C, ie 95% of the compounds present in the feed have a temperature above 340 ° C, more preferably above 370 ° C. Boiling point.

The nitrogen content of the treated hydrocarbon feed is typically above 500 ppm by weight. Usually, the amount of sulfur is in the range of 0.01% by weight to 5% by weight.

The feed to the catalyst cracking unit corresponds to the unconverted portion of the feed of the pretreatment unit. It typically contains more than 50% by weight of hydrocarbons having a boiling point above 340 °C. The feed contains less impurities (e.g., nitrogen or sulfur containing compounds) than the feed to be hydrotreated and has a higher hydrogen content (typically in the range of 11% to 15%).

The gasoline fraction corresponds to a hydrocarbon fraction having a distillation range of from 50 ° C to 220 ° C, preferably from 50 ° C to 160 ° C.

The middle distillate corresponds to a hydrocarbon fraction having a distillation ranging from 130 ° C to 380 ° C, preferably from 150 ° C to 370 ° C.

The "slurry" fraction corresponds to a hydrocarbon fraction having an initial boiling point above 380 ° C, preferably above 360 ° C.

Specific conditions for the various steps of the method of the invention are set forth in detail below.

1) Pretreatment step (PRET)

According to the invention, the pretreatment step can be carried out by means of a unit for hydrotreating a heavy feed in a fixed or bubbling bed or by means of a hydrotreating or hydrocracking catalyst for mild or intense hydrocracking The conventional catalyst type is formed by a sulfide of a metal of Groups VI and VIII on an alumina or ceria-alumina type support. It is also conceivable to also include a catalyst for the zeolite in the carrier. When the pretreatment reaction is carried out in a dropper cocurrent mode in a fixed bed, the operating conditions are generally selected such that the temperature is in the range of 300 ° C to 450 ° C, preferably in the range of 350 ° C to 430 ° C, and the total pressure is 30 to 300 bar, preferably in the range of 50 to 180 bar, the hourly space velocity is in the range of 0.1 h ^-1 to 10 h ^-1 , preferably in the range of 0.3 h ^-1 to 5 h ^-1 , and hydrogen The ratio with the hydrocarbon is in the range of 200 Nm ³ /m ³ to 4000 Nm ³ /m ³ , preferably in the range of 300 Nm ³ /m ³ to 2000 Nm ³ /m ³ .

These units can be used for hydrodesulfurization, hydrodenitrogenation or hydrodearomatization of feeds and converting a portion of the heavy feed to a scalable product. This conversion of the hydroconversion unit is higher than the hydrotreating unit.

The pretreatment is carried out by means of a high hydrogen pressure fixed or bubbling bed catalyst process using a hydrotreating or hydrocracking catalyst.

The pretreatment section comprises at least one reaction zone comprising at least one hydrorefining catalyst, preferably having a high activity for hydrodesulfurization, hydrodenitrogenation and hydrogenation of aromatic compounds.

The pretreatment catalyst (also known as hydrotreating catalyst) can be selected from catalysts commonly used in the art. The hydrotreating catalyst may preferably comprise a matrix and at least one hydrogenation-dehydrogenation element selected from the group consisting of: elements from Groups VIB and VIII of the elemental cycle classification.

The matrix may be composed of a compound which is used singly or in the form of a mixture, for example, alumina, aluminum halide, cerium oxide, cerium oxide-alumina, clay (for example, selected from natural clays such as kaolin or bentonite). ), magnesium oxide, titanium oxide, boron oxide, zirconium oxide, aluminum phosphate, titanium phosphate, zirconium phosphate, coal and aluminate. It is preferred to use a matrix comprising alumina which is in all forms known to those skilled in the art and more preferably alumina such as gamma alumina.

The hydrogenation-dehydrogenation element may be selected from the group formed by elements from Group VIB and non-precious elements from Group VIII in the elemental cycle classification.

Preferably, the hydrogenation-dehydrogenation element is selected from the group consisting of molybdenum, tungsten, nickel and cobalt.

More preferably, the hydrogenation-dehydrogenation element comprises at least one element from Group VIB and at least one non-precious element from Group VIII. This hydrogenation-dehydrogenation element may, for example, comprise a combination of at least one element from Group VIII (Ni, Co) and at least one element from Group VIB (Mo, W).

Preferably, the hydrotreating catalyst further comprises at least one doping element deposited on the catalyst and selected from the group consisting of phosphorus, boron and cerium. In particular, the hydrofinishing catalyst may include boron and/or rhenium, and may also have phosphorus as a doping element.

The amount of boron, bismuth and phosphorus is usually in the range of from 0.1% by weight to 20% by weight, preferably from 0.1% by weight to 15% by weight, more preferably from 0.1% by weight to 10% by weight.

The hydrotreating catalyst may advantageously comprise phosphorus.

This compound provides a hydrofinishing touch that has two main advantages in particular Medium: The first advantage is more convenient to specifically prepare the catalyst during the impregnation of the hydrogenation-dehydrogenation element, for example, from a solution based on nickel and molybdenum.

A second advantage provided by this compound is the increased hydrogenation activity of the catalyst.

In a preferred hydrotreating catalyst, the total concentration of oxides of metals from Groups VIB and VIII is in the range of 2% by weight (preferably 5% by weight) to 40% by weight, preferably 3% by weight. (preferably 7% by weight) to 30% by weight, and the weight ratio (expressed as metal oxide) of one or more metals from Group VIB and one or more metals from Group VIII is between 20 and 1.25 Within the range, preferably in the range of 10 to 2.

The concentration of phosphorus oxide P ₂ O ₅ may be less than 15% by weight, preferably less than 10% by weight. Preferred carriers are alumina containing 5-95% SiO ₂ or cerium oxide-alumina, either alone or in admixture with the zeolite.

In another hydrotreating catalyst comprising boron and/or rhenium, preferably boron and rhodium, the catalyst typically comprises (in the form of % by weight relative to the total mass of the catalyst): from 1% to 99%, Preferably from 10% to 98% and more preferably from 15% to 95% of at least one substrate; from 3% to 60%, preferably from 3% to 45%, more preferably from 3% to 30%, at least one from a metal of Group VIB; - optionally from 0 to 30%, preferably from 0 to 25%, more preferably from 0 to 20%, of at least one metal from Group VIII; from 0.1% to 20%, preferably 0.1 % to 15% and more preferably 0.1% to 10% of boron and/or 0.1% to 20%, preferably 0.1% to 15% and more preferably 0.1% to 10%; Optionally, 0 to 20%, preferably 0.1% to 15%, more preferably 0.1% to 10% phosphorus; and ● optionally 20 to 20%, preferably 0.1% to 15%, more preferably At least one of 0.1% to 10% of an element selected from Group VIIA (e.g., fluorine).

In another hydrorefining catalyst, the catalyst comprises: from 1% by weight to 95% by weight (% by weight) of at least one substrate, preferably alumina; from 5% by weight to 40% by weight (oxidized) At least one of the range of components from Group VIB and Group VIII (non-precious elements); ● in the range of from 0 to 20%, preferably from 0.1% by weight to 20% by weight (% by weight) At least one promoter element selected from the group consisting of phosphorus, boron and lanthanum; at least one of 0 to 20% by weight (% by weight) of at least one element from Group VIIB (for example, manganese); 0 to 20% by weight (oxidized) At least one of the range of elements from Group VIIA (e.g., fluorine, chlorine); and from 0 to 60% by weight (% by weight) of at least one element from Group VB (e.g., hydrazine).

In general, a hydrotreating catalyst having the following atomic ratio is preferred: • The atomic ratio of the Group VIII metal/Group VIB metal is in the range of 0 to 1; • In the presence of B, the B/Group VIB metal The atomic ratio is in the range of 0.01 to 3; ● the atomic ratio of the Si/VIB metal is 0.01 to 1.5 in the presence of Si Within the range; ● in the presence of P, the atomic ratio of the P/Group VIB metal is in the range of 0.01 to 1; and ● in the presence of at least one element from the Group VIIA, the Group VIIA metal / Group VIB metal The atomic ratio is in the range of 0.01 to 2.

The preferred hydrotreating catalyst is NiMo and/or NiW on alumina or ceria-alumina catalyst, ie on alumina or ceria-alumina catalyst and doped with at least one NiMo and/or NiW included in an element of an atomic group formed of phosphorus, boron, germanium, and fluorine.

Applicants have also developed such catalysts. Examples which may be cited are those described in the patents FR 2 904 243, FR 2 903 979 and EP 1 892 038.

In the case where it is desired to have a higher conversion rate in the pretreatment step, a hydrocracking catalyst is used. The hydrocracking catalysts must be bifunctional catalysts having a hydrogenation phase (which is capable of hydrogenating the aromatic compound and creating a balance between the saturated compound and the corresponding olefin) and an acid phase (which is available) Promote hydroisomerization and hydrocracking reactions).

Providing acid functionality by a carrier having a relatively large surface area (typically from 100 m ² /g to 800 m ² /g) and surface acidity, such as, for example, aluminum halide (specifically chlorinated or fluorine) Alumina), a combination of boron and aluminum, amorphous ceria-alumina and zeolite.

The hydrogenation function is provided by one or more metals from Group VIII of the elemental cycle classification (eg, iron, cobalt, nickel, rhodium, ruthenium, palladium, osmium, iridium or platinum), or from at least one a metal of Group VIB of the elemental periodic classification (such as molybdenum or tungsten) and at least one metal from Group VIII The association.

Applicants have also developed various such catalysts. Examples of patents that can be cited are 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.

Catalysts that can be used in the pretreatment (PRET) unit of the present invention are sold by AXENS from the following series of catalysts: HR 500 (eg HR526, HR538, HR548, HR558, HR562, HR568 and HRK558), HDK700 (HDK766) , HDK776, HDK786) or HYK700 (HYK732, HYK752, HYK762, HYK742).

The unit for separating the effluent from the pretreatment unit typically includes a primary separation of the gas and liquid effluent, a hydrogen recycle section, and a distillation stage for fractionating the various liquid fractions.

At the end of the pretreatment step (PRET), the unconverted fraction produced contains substantially less sulfur and nitrogen containing compounds and higher hydrogen content than the feed is not subjected to the pretreatment step. This aspect means that the amount of impurities obtained in the effluent from the FCC step (which is placed downstream) can be substantially reduced.

2) Catalyst lysis step (FCC):

The catalyst lysis unit comprises a reactor that can be in a riser or dropper mode.

When the catalyst cleavage is carried out in a single pipette reactor, the reactor outlet temperature (ROT) is in the range of 450 ° C to 650 ° C, preferably in the range of 470 ° C to 620 ° C, and the C/O ratio is 2 It is in the range of 20, preferably in the range of 4 to 15.

When the reactor is in the dropper mode, the reactor outlet temperature (ROT) is in the range of 480 ° C to 650 ° C and the C/O ratio is in the range of 10 to 50.

The spent catalyst stream obtained from the FCC reactor is separated from the cracked effluent by any gas-solid separation system known to those skilled in the art and regenerated in a dedicated regeneration zone.

The effluent from the catalytic cracking reactor is sent to a fractionation zone to produce several fractions as defined by the refiner needs.

According to the invention, the catalyst cleavage catalyst is comprised of an alumina, ceria or cerium oxide-alumina matrix with or without an ultrastable Y-type zeolite dispersed in the same matrix.

It is also conceivable to add an additive based on ZSM-5 zeolite in an amount of less than 30% by weight of the total amount of the catalyst.

The catalyst used in the FCC reactor is typically comprised of particles having an average diameter generally ranging from 40 microns to 140 microns, typically in the range of 50 microns to 120 microns.

The catalyst cleavage catalyst contains at least one suitable substrate (e.g., alumina, ceria or cerium oxide-alumina) with or without the Y-type zeolite dispersed in the matrix.

The catalyst may also include at least one zeolite having a form selectivity and having one of the following structural types: MEL (eg, ZSM-11), MFI (eg, ZSM-5), NES, EUO, FER, CHA (eg, SAPO- 34), MFS, MWW. It may also include one of the following zeolites which also have a form selectivity: NU-85, NU-86, NU-88 or IM-5.

An advantage of such zeolites having formal selectivity is that a preferred propylene/isobutylene selectivity is obtained, i.e., a higher propylene/isobutylene ratio in the effluent from the cracking.

The ratio of the formally selective zeolite to the total amount of zeolite can vary depending on the feed used and the structure of the desired product. Typically, from 0.1% to 60% by weight, preferably from 0.1% to 40% by weight and in particular from 0.1% to 30% by weight, of a formally selective zeolite is used.

One or more zeolites may be dispersed in a matrix based on cerium oxide, aluminum oxide or cerium oxide-alumina, and the ratio of zeolite (all zeolites) to the weight of the catalyst is usually in the range of 0.7% by weight to 80% by weight, It is preferably in the range of 1% by weight to 50% by weight and more preferably in the range of 5% by weight to 40% by weight.

Where several zeolites are used, the zeolites may be incorporated into a single matrix or several different matrices. The amount of zeolite having a form selectivity in the total inventory is less than 30% by weight.

The catalyst used in the catalyst cleavage reactor may be composed of an ultrastable Y-type zeolite dispersed in an alumina, ceria or cerium oxide-alumina matrix, and an additive based on ZSM-5 zeolite is added to the matrix. The amount of ZSM-5 crystals in the total catalytic amount is less than 30% by weight.

The unit for separating the effluent from the catalytic converter (FCC) typically comprises a primary separation of the FCC effluent, a section for compressing and fractionating the gas, and a distillation for fractionating the various liquid fractions.

In some cases, the HCO fraction (shown as stream (17) in Figure 1) produced during the FCC can be recycled to the pretreatment unit.

The olefinic fraction obtained by catalytic cracking (consisting of C3, C4 olefins and gasoline having a fractionation temperature of less than 220 ° C, preferably less than 160 ° C) may be derived from several different fractions (for example, C3 fractions and gasoline fractions) Forming, transporting the olefinic fractions to one or more oligomerization units.

At the end of this step, the resulting gasoline fraction contains less sulfur compounds and nitrogen-containing compounds than at the end of the FCC alone, while maintaining an equivalent amount of olefins.

This aspect means that the purification step directly upstream of the oligomerization step can be reduced or even avoided.

3) Purification step (PUR)

The gasoline feed to be treated is sent to a purification unit which uses an adsorbent such as a molecular sieve (for example, NaX or NaY type) and operates under the following operating conditions: • the temperature is in the range of 20 ° C to 50 ° C; It is from 5 to 30 bar; ● HSV is in the range of 0.5 h ^-1 to 4 h ^-1 .

Examples of adsorbents that can be used in the purification unit and which can be cited are metal oxides (such as alumina), crystalline cerium-aluminates (such as zeolites (generally referred to as molecular sieves)) or mixtures of such compounds.

Among these compounds, molecular sieves based on faujasite-type zeolite are preferred. An example is a NaX zeolite, such as sold by Axens under the trade name SBE 13X.

In some cases, simple fractionation can also be used to produce a light fraction of the nitrogen-containing compound that is depleted and acceptable for the oligomeric segment.

4) Oligomerization step (OLG)

The purpose of the oligomerization step is to oligomerize C3 to C12 olefins which may be formed from several different fractions (for example, C3 to C4 fractions and C5-160 ° C fractions, either alone or in a mixture), thereby obtaining the main Contains 8 or more A mixture of hydrocarbons of a single olefin of a plurality of carbon atoms.

Generally, oligomers containing mainly 30 or fewer carbon atoms are available from C4 olefins; most contain from 8 to 20 carbon atoms.

The difference between oligomerization and polymerization is the addition of a limited number of molecules. In the context of the present invention, the number of molecules added together is in the range of 2 to 20 (inclusive), preferably between 2 and 5 and more preferably between 2 and 4.

However, the oligomeric product may comprise oligoolefins containing more than 10 molecules in trace amounts. Typically, the traces represent less than 5% by weight of the oligomer formed.

Oligomerization can be carried out in one or more steps using one or more reactors in parallel or in series configuration and one or more catalysts.

The following description of the catalyst and operating conditions can be applied to any of the steps and to any of the reactors.

The solid oligomeric catalysts operating in the heterogeneous phase are selected from the catalysts known in the art. Specific conditions for the various steps of the method of the invention are set forth in more detail below.

The oligomeric catalyst used is preferably an acid catalyst based on ceria-alumina or amorphous ceria-alumina, crystalline zeolite or resin.

A preferred resin is TA801 sold by AXENS.

The operating temperature is in the range of from 60 ° C to 200 ° C, preferably in the range of from 80 ° C to 180 ° C.

The operating pressure is in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 2 MPa to 4 MPa.

Preferred zeolites are described in the patent FR 2 894 850. Operating temperature The degree is in the range of 100 ° C to 350 ° C, preferably in the range of 150 ° C to 270 ° C.

The operating pressure is in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 4 MPa to 5 MPa; The poly unit produces a portion of the C5-220 ° C gasoline fraction, preferably a light C5-160 ° C gasoline fraction, which is recycled to the oligomerization reactor to improve the middle distillate yield.

5) Final hydrogenation step (HDT)

The final hydrogenation step (HDT) requires a partially or fully vulcanized catalyst based on Ni or NiMo or CoMo or even NiCoMo and NiW, supported on a refractory oxide type carrier (Al, Ti, Si), and The situation has one or more promoters (F, P, Ca, Na).

The invention is explained in more detail with the aid of Figure 1.

The feed (1) is introduced into the pretreatment unit (PRET) together with the hydrogen supply (1b).

This treatment in the presence of hydrogen is intended to convert the olefin to an alkane; it can be carried out using any of the catalysts known in the art and under relevant operating conditions. In particular, a sulfide catalyst based on Ni and Mo, such as HR 306, HR 406 or HR 506 sold by AXENS, may be used. The catalysts are operated in the gas phase and at high temperatures (350-420 ° C) and at high hydrogen levels.

Catalysts based on Ni and S (such as those sold by AXENS, LD series 241, 341 and 541) and operated at lower temperatures (150-180 ° C) in the liquid phase may also be used and are preferred.

Conventionally, the following materials are extracted from the pretreatment unit (PRET) in order of increasing molecular weight: • gasoline fraction (3); • fraction called “middle fraction” (4); • unconverted fraction (5) .

The fraction (5) is then conveyed to a catalyst cracking unit (FCC) from which the following materials are extracted in order of increasing molecular weight: • a dry gas fraction (7) from hydrogen (H ₂ ), Methane and possibly ethane, ethylene; ● C3 fraction (8) formed from a propylene-rich hydrocarbon molecule containing 3 carbon atoms; ● C4 fraction (9) consisting of 4 carbon atoms Hydrogen-rich hydrocarbon molecules are formed; ● gasoline fraction (10); ● fraction called "middle fraction"(11); ● fraction called "slurry" fraction (12), which is added To the fuel pool; • In some cases, the HCO fraction can be withdrawn and recycled to the pretreatment (2).

The gasoline fraction (10) is then purified in a purification unit (PUR) as appropriate.

The purified gasoline fraction (10') is then fed as a feed together with fractions (8) and (9) for the oligomerization unit (OLG).

The following three fractions are extracted from this oligomerization unit (OLG): • Fraction (14), which is called raffinate and corresponds to from C3(8) and C4 (9) unconverted olefin and paraffin fed; • gasoline fraction (15) corresponding to paraffin wax contained in fraction (10') and a portion or formed from fractions (8) and (9) Oligomer product; a middle distillate corresponding to the heavy oligomeric product formed from fractions (8), (9) and (10').

The middle distillate is sent to a hydrogenation unit (HDT) to meet commercial specifications.

Instance

Two examples are now provided to illustrate the improved performance of the method of the invention compared to prior art methods.

Example 1 (Prior Art): Reference Case for FCC+ Oligo

This first example constitutes a base case and corresponds to a single riser FCC unit and a subsequent oligomerization unit.

The FCC unit has a capacity of 40,000 BPSD, i.e., 230 t/hr (abbreviation of BPSD cylinder/day), which processes straight-run VGO (i.e., vacuum gas oil) obtained directly from the vacuum distillation unit.

The catalyst cleavage unit is operated using a catalyst system composed of cerium oxide-alumina.

The main characteristics of the feed and the operating conditions for the FCC unit are shown in Tables 1 and 2, respectively.

Under these conditions, the yield of the feed relative to the product leaving the catalytic cracking unit is given in Table 3.

The amount of olefins in IBP-160 ° C gasoline was 47.6% by weight and the nitrogen content was 50 ppm by weight.

The sulfur content is 800 ppm by weight.

The C3 fraction (mainly composed of propylene and propane) and the C4 fraction (mainly composed of butene and butane) and the gasoline fraction (IBP-160 ° C) are then conveyed to the oligomerization unit.

The purified fraction is placed upstream of the oligomerization unit due to the presence of sulfur and nitrogen. It consists of a large number of NaX molecular sieves in the form of a fixed bed. Arranged and operated at a temperature of 25 ° C, with one bed in operational mode and one bed in regenerative mode.

The operating conditions for the purification and oligomerization units are presented in Table 4.

Under these conditions, the yields of the feeds obtained in the catalyst cracking unit and the oligomerization unit compared to the feeds entering the catalyst cracking unit are given in Table 5 below:

The middle distillate obtained from the oligomerization is then hydrogenated: using a nickel sulfide catalyst (LD 541) at 160 ° C and 50 bar hydrogen and at 1.5 h ^-1 HSV and the flow rate of gaseous hydrogen with respect to the liquid feed flow rate is 100 NL / Hydrogenation is carried out under L.

Thus, the delivery of the C3, C4 and gasoline fractions to the oligomerization step increases the yield of the middle distillate by 29.3% by weight.

Example 2 (Invention): mitigation of a hydrocracking unit, followed by FCC units and units for oligomeric C3, C4 olefins and gasoline

In Example 2, the FCC units were operated under the same conditions as those set forth for Example 1, but at this point there was a mild hydrocracking unit prior to the FCC unit, supplied and examples in the moderated hydrocracking unit. 1 same feed (ie straight-run VGO).

The operating conditions used to mitigate the hydrocracking unit are presented in Table 6.

Under these conditions, the yields of the feeds leaving the product of the mild hydrocracking step are given in Table 7.

At the end of the catalyst cracking step, the yield of the product with respect to the hydrotreated VGO feed varies, as illustrated in Table 8 below:

The olefin content of the IBP-160 ° C gasoline was 44.0% and the nitrogen content was 20 ppm by weight. The sulfur content is 150 ppm.

The C3 fraction (mainly composed of propylene and propane) and the C4 fraction (mainly composed of butene and butane) and the gasoline fraction (IBP-160 ° C) are then conveyed to the oligomerization unit.

Purification and oligomerization conditions are given in Table 9 below:

The amount of impurities (nitrogen and sulfur) in the feed is small, which means that the amount of molecular sieve used in the purification unit located upstream of the oligomerization unit is substantially substantially reduced (from 22.1 metric tons to 8.8 metric tons).

The size of the sieve purification unit is thus greatly reduced.

The yields of the products obtained from the C3=, C4=, mild hydrocracking of the gasoline fraction, the catalyst cracking and the oligomerization in the feed to the mitigation hydrocracking unit are given in Table 10:

The middle distillate was then hydrogenated under the same conditions as those of Example 1.

The in-line coupling of the mild hydrocracking (PRET) and (FCC) units and the oligomeric unit (OLG) unit significantly improves the amount of middle distillate produced. In the basic case, the production of this middle distillate accounted for 45.0% by weight of the FCC feed, compared to 54.03% by weight in the configuration of the invention, ie an increase of 9.03%.

The gasoline fraction itself does not increase due to pretreatment, and actually decreases by 1.30% by weight from 33.95% by weight to 32.65% by weight in the base case.

This improved the selectivity of the middle distillate to gasoline (middle fraction/gasoline ratio), which changed from 1.32 to 1.65, ie a relative increase of 25% by weight, which represents a significant improvement in the fuel market change.

1‧‧‧Heavy feedstock

1b‧‧‧ Hydrogen supply

3‧‧‧C5-160 °C gasoline fraction

4‧‧‧First middle distillate

5‧‧‧Unconverted part

7‧‧‧Dry gas fraction

8‧‧‧C3 fraction

9‧‧‧C4 fraction

10‧‧‧C5-160 °C gasoline fraction

10'‧‧‧ gasoline fraction

11‧‧‧Second middle distillate

12‧‧‧"Slurry" fraction

14‧‧‧C3/C4 fraction

15‧‧‧C5-160 °C gasoline fraction

16‧‧‧ third middle distillate

17‧‧‧ flow

FCC‧‧‧catalyst cracking unit

HDT‧‧‧Hydrogenation unit/hydrogenation unit

OLG‧‧‧ oligomeric unit

PRET‧‧‧Pretreatment unit

PUR‧‧·purification unit

Figure 1 represents an arrangement of the method of the present invention, wherein each unit is represented as follows: (PRET) system pretreatment; (FCC) is a catalyst cleavage; (PUR) is an upstream unit of the oligomerization purification unit; (OLG) is the oligomerization unit And (HDT) is a unit of a middle distillate obtained by hydrotreating from oligomerization.

1‧‧‧Heavy feedstock

1b‧‧‧ Hydrogen supply

3‧‧‧C5-160 °C gasoline fraction

4‧‧‧First middle distillate

5‧‧‧Unconverted part

7‧‧‧Dry gas fraction

8‧‧‧C3 fraction

9‧‧‧C4 fraction

10‧‧‧C5-160 °C gasoline fraction

10'‧‧‧ gasoline fraction

11‧‧‧Second middle distillate

12‧‧‧"Slurry" fraction

14‧‧‧C3/C4 fraction

15‧‧‧C5-160 °C gasoline fraction

16‧‧‧ third middle distillate

17‧‧‧ flow

FCC‧‧‧catalyst cracking unit

HDT‧‧‧Hydrogenation unit/hydrogenation unit

OLG‧‧‧ oligomeric unit

PRET‧‧‧Pretreatment unit

PUR‧‧·purification unit

Claims (9)

A method of producing a middle distillate from a heavy gas feed of a vacuum gas oil or an atmospheric residue type (1) using the following four consecutive steps: a) a pretreatment step (PRET), which is in hydrocracking Or a hydrotreating unit is implemented to reduce the amount of sulfur and nitrogen-containing impurities in the feedstock and its diene content, and it delivers a C5-160 ° C gasoline fraction (3) with a distillation range of 160 ° C - 360 a first middle fraction (4) of °C and a portion referred to as an unconverted portion (5) having substantially the same distillation range as the introduced heavy feed; b) catalytic cracking (FCC) from the pretreatment step ( PRET) The step of obtaining the unconverted portion (5) which produces a fraction called dry gas fraction (7) used as a fuel, C3 fraction (8), C4 fraction (9), C5-160 °C gasoline fraction (10) and second middle fraction (11), the gasoline fraction (10) is sent to a purification unit (PUR); c) an oligomerization step (OLG), which is supplied from the catalyst for cracking The C3 fraction (8) obtained by the unit, the C4 fraction (9), and the gasoline fraction (10') obtained from the purification unit (PUR), and which produces a C3/C4 fraction (14), enters the gasoline Pool C5-160 °C gasoline fraction (15) and transport to hydrogenation The third intermediate processing unit (HDT) of the fraction (16); D) fully hydrogenated (HDT) is obtained from the oligomerization step of the intermediate fraction (16) of the step to meet market specifications on the gas-oil system. A method for producing a middle distillate from a heavy gas feed of a vacuum gas oil or an atmospheric residue type (1), wherein the pretreatment unit (PRET) is a hydrocracking type and is under the following conditions Operation: temperature in the range of 350 ° C to 420 ° C; pressure in the range of 8 MPa to 12 MPa; HSV in the range of 0.3 h ^-1 to 1 h ^-1 ; H ₂ /HC in 300 L / L to Within the range of 800 L/L; the catalyst is based on NiMo, NiCoMo, NiW. A method for producing a middle distillate from a heavy gas feed (1) of a vacuum gas oil or an atmospheric residue type according to claim 1, wherein the pretreatment unit (PRET) is hydrotreated and under the following conditions Operation: temperature in the range of 350 ° C to 420 ° C; pressure in the range of 4 MPa to 8 MPa; HSV in the range of 0.5 h ^-1 to 2 h ^-1 ; H ₂ /HC in the 150 L / L to 200 Within the range of L/L; the catalyst is based on NiMo, CoMo, NiCoMo. A method of producing a middle distillate from a heavy gas feed (1) of a vacuum gas oil or an atmospheric residue type according to claim 1, wherein the catalyst cracking unit (FCC) operates under the following conditions: when in a single When the catalyst cracking is carried out in the riser reactor, the reactor outlet temperature (ROT) is in the range of 450 ° C to 650 ° C, preferably in the range of 470 ° C to 620 ° C, and the C/O ratio is 2 Within the range of 20, preferably in the range of 4 to 15; when the reactor is a dropper reactor, the reactor outlet temperature (ROT) is in the range of 480 ° C to 650 ° C, and the C / The O ratio is in the range of 10 to 50, preferably 10 to 30. A method of producing a middle distillate from a heavy gas feed of a vacuum gas oil or an atmospheric residue type (1), wherein the purification unit (PUR) for ex FCC gasoline feed comprises distillation The step of fractionating to produce a light fraction of the nitrogen-containing compound depletion, and/or comprising the step of adsorbing on the molecular sieve under the following conditions: temperature in the range of 20 ° C to 50 ° C; pressure in the range of 5 to 30 bar ;HSV is in the range of 0.5 h ^-1 to 4 h ^-1 ; molecular sieve (for example, NaX or NaY type). A method of producing a middle distillate from a heavy gas feed (1) of a vacuum gas oil or an atmospheric residue type according to claim 1, wherein the unit for the oligomerization (OLG) of the ex FCC gasoline is as follows Operating under conditions: operating temperature is in the range of 100 ° C to 350 ° C, preferably in the range of 150 ° C to 270 ° C; operating pressure is in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascal), It is preferably in the range of 2 MPa to 6 MPa, more preferably in the range of 4 MPa to 5 MPa; the catalyst is based on cerium oxide-alumina or amorphous cerium oxide-alumina or crystalline zeolite. A method of producing a middle distillate from a heavy gas feed (1) of a vacuum gas oil or an atmospheric residue type according to claim 1, wherein the unit for the oligomerization (OLG) of the ex FCC gasoline is as follows Operating under conditions: the operating temperature is in the range of 180 ° C to 350 ° C, preferably in the range of 200 ° C to 270 ° C; the operating pressure is in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascals) Preferably, it is in the range of 2 MPa to 6 MPa, more preferably in the range of 4 MPa to 5 MPa; in the case of upgrading the fraction to diesel, the catalyst is based on crystalline zeolite. A method of producing a middle distillate from a heavy gas feed (1) of a vacuum gas oil or an atmospheric residue type according to claim 1, wherein the unit for the oligomerization (OLG) of the ex FCC gasoline is as follows Operating under conditions: the operating temperature is in the range of 60 ° C to 200 ° C, preferably in the range of 80 ° C to 180 ° C; the operating pressure is in the range of 1 MPa to 10 MPa (1 MPa = 10 ⁶ Pascals) Preferably, it is in the range of 2 MPa to 6 MPa, more preferably in the range of 2 MPa to 4 MPa; the catalyst is an organic acid resin type. The method of any one of claims 6 to 8, wherein the gasoline portion (15) produced by oligomerization (OLG) is at least partially recycled to the FCC unit to maximize the production of the middle distillate.