RU2662825C2 - Process to prepare gas oil fraction and residual base oil - Google Patents

Abstract

FIELD: chemistry.SUBSTANCE: present invention relates to a process for producing a gas oil fraction, heavy distillate fraction and a residual base oil fraction from Fischer-Tropsch derived feedstock. Method includes the following steps: (a) directing the feedstock to a hydroprocessing step to produce at least partially isomerised feedstock; (b) separating the isomerised feedstock by means of distillation into at least a gas oil fraction, a heavy distillate fraction having distillation temperature T90 wt% of 400 to 550°C, and a residual fraction, the residual fraction having a distillation temperature T10 wt% of 200 to 450°C; (c) recycling from more than 20 to not more than 70 wt% of the residual fraction to step (a) and (d) catalytic dewaxing of the remaining residual fraction to obtain a residual base oil.EFFECT: proposed method makes it possible to improve the quality and / or yield of the fractions obtained.14 cl, 1 dwg, 2 tbl, 2 ex

Description

The invention relates to a method for producing gas oil and base oil.

Such methods are known in the art, for example, from WO 2009080681. This publication describes a method for producing a gas oil fraction and a residual base oil fraction from a Fischer-Tropsch derived feedstock by directing the feedstock to a hydroprocessing step to obtain at least partially isomerized feedstock ; separating the isomerized feed by distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction; recycling at least a portion of the heavy distillate fraction to hydroprocessing; and lowering the pour point of the residual fraction using catalytic dewaxing to obtain a base oil.

Method WO 2009080681 provides many different products, but gives only a limited yield of heavy base oil. At the same time, there remains a general need in the technical field for an additional increase in the yield and quality of Fischer-Tropsch synthesis products.

The objective of the present invention is to provide a method that allows you to get at least part of the gas oil fraction and the residual base oil fraction. Another object of the invention is to improve the quality and / or yield of all liquid fuel components.

In a first aspect, the invention relates to a method for producing a gas oil fraction, a heavy distillate fraction and a residual base oil fraction from a Fischer-Tropsch derived feedstock using (a) directing the feedstock to a hydroprocessing step to produce at least partially isomerized feedstock; (b) separating the isomerized feed by distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction, the residual fraction having a distillation temperature of T10% by weight. from 200 ° C to 450 ° C; (c) recycling a portion of the residual fraction to step (a); and (d) catalytic dewaxing of the remaining residual fraction to obtain a residual base oil.

Applicants have discovered that, according to the method of the invention, a highly saturated residual base oil can be obtained that is substantially sulfur free and has a high viscosity index. In addition, the gas oil fraction has improved cold flow properties and is therefore very useful as a component of liquid fuel. Along with this, the amount of heavy distillate increases.

The feed formed in the Fischer-Tropsch synthesis is a feedstock obtained in the process of Fischer-Tropsch condensation. The Fischer-Tropsch condensation process is a reaction that converts carbon monoxide and hydrogen into longer chain hydrocarbons, usually paraffinic hydrocarbons, in the presence of a suitable catalyst and usually at elevated temperatures (for example, 125-300 ° C, preferably 175-250 ° C ) and / or pressures (for example, 5-100 bar (0.5-10.0 MPa), preferably 12-70 bar (1.2-7.0 MPa)). If necessary, ratios of hydrogen to carbon monoxide other than 2: 1 can be used.

The feed formed in the Fischer-Tropsch synthesis preferably has an initial boiling point below 400 ° C and a final boiling point above 600 ° C. Preferably, the fraction boiling at a temperature above 540 ° C. in the feed in step (a) is at least 20% by weight.

The hydrocracking / hydroisomerization reaction in step (a) is preferably carried out in the presence of hydrogen and a catalyst known in the art as suitable for the reaction. The catalysts used in step (a) typically have acidic functionality and hydrogenation / dehydrogenation functionality. Preferably, zeolites and carriers based on refractory metal oxides possess acid functionality. Suitable carrier materials include zeolites, silica, alumina, silica-alumina, zirconia, titanium dioxide, and mixtures thereof. Zeolites may include beta, Y, ZSM-12, EU-2, ZSM-48 zeolites. Carrier materials preferred for inclusion in a catalyst for use in the process of this invention are silica, alumina, and silica-alumina. A particularly preferred catalyst comprises platinum supported on a silica-alumina support. If necessary, applying to the carrier a halogen-containing functional group, in particular a fluorine-containing or phosphorus-containing functional group, can increase the acidity of the catalyst carrier.

Preferably, the Group VIII noble metals, for example, palladium, and more preferably platinum, have hydrogenation / dehydrogenation functionality. The catalyst may contain an active hydrogenation / dehydrogenation component in an amount of from 0.005 to 5 parts by weight, preferably from 0.02 to 2 parts by weight, per 100 parts by weight of carrier material. A particularly preferred catalyst for use in the hydroconversion step contains platinum in an amount in the range of 0.05 to 2 parts by mass, more preferably 0.1 to 1 parts by mass, per 100 parts by mass of carrier material. The catalyst may also contain a binder to enhance the strength of the catalyst. The binder may be non-acidic. Examples are clays, aluminas, and other binders known to one skilled in the art. Examples of suitable hydrocracking / hydroisomerization processes and suitable catalysts are described in WO-A-0014179, EP-A-532118, EP-A-666894 and EP-A-776959.

The hydrocracking / hydroisomerization reaction in step (a) is carried out at elevated temperature and pressure. Temperatures typically range from 175 ° C to 380 ° C, preferably above 250 ° C, and more preferably from 300 ° C to 370 ° C. The pressure is usually in the range of 10-250 bar abs. (1-25 MPa) and preferably 20-80 bar abs. (2-8 MPa). Hydrogen can be supplied in the form of a gas at an hourly space velocity of from 100 to 10,000 nl / l / h, preferably from 500 to 5,000 nl / l / h. The hydrocarbon feed may be supplied at an hourly average space velocity of 0.1 to 5 kg / l / h, preferably more than 0.5 kg / l / h and more preferably less than 2 kg / l / h. The ratio of hydrogen to hydrocarbon feed may be in the range from 100 to 5000 nl / kg and preferably from 250 to 2500 nl / kg. The conversion in step (a), defined as the mass percentage of a feed with a boiling point above 370 ° C., converted in a passage to a fraction with a boiling point below 370 ° C., is at least 20% by weight, preferably at least 25% of the mass., But preferably not more than 80% of the mass., More preferably not more than 70% of the mass. The term “feed” as used above in the definition is the sum of the hydrocarbon feed fed to step (a), including, for example, any recycle streams. The hydrocracked and at least partially isomerized feed obtained in step (a) may also be called a waxy raffinate. The waxy raffinate preferably has a relatively low pour point, below 40 ° C, more preferably below 35 ° C and even more preferably below 30 ° C. The waxy raffinate preferably has a distillation temperature of T10% by weight. from 200 ° C to 450 ° C and preferably from 300 ° C to 420 ° C. The waxy raffinate may contain the entire residual fraction of atmospheric distillation. The waxy raffinate may have a distillation temperature of T98% by mass, above 600 ° C.

In step (b), the feed is separated by distillation into at least a gas oil fraction, a heavy distillate fraction and a residual fraction. Distillation can be carried out in one or more stages. The first step may be atmospheric distillation followed by, for example, vacuum distillation. Distillation is usually carried out at low (vacuum) pressures, more preferably vacuum distillation is carried out at a pressure of from 1 to 250 mbar (0.0001-0.025 MPa), more preferably from 10 to 100 mbar (0.001-0.010 MPa) and most preferably from 10 to 75 mbar (0.001-0.0075 MPa). Preferably, the effective temperature of the separation boundary in step (b), at which the gas oil fraction and the higher boiling fraction of the heavy distillate are separated, is from 300 ° C to 400 ° C and more preferably from 320 ° C to 370 ° C. Preferably, the effective temperature of the separation boundary in step (b), at which the heavy distillate fraction and the residual fraction are separated, is from 450 ° C. to 600 ° C.

The gas oil fraction, as a rule, will contain a large part (for example, 95 vol.% Or more) of components having boiling points in a typical range of diesel fuel (“gas oil”), i.e. from about 150 ° C to 400 ° C or from 170 ° C to 370 ° C. Accordingly, 90 vol.% Will have a distillation temperature from 300 ° C to 370 ° C. Gas oil will typically have a density (IP-365/97) of 0.76 to 0.79 g / cm ³ at 15 ° C; cetane number (ASTM D-613) more than 70, appropriate from 74 to 85; VK 40 (kinematic viscosity at 40 ° C according to ASTM D-445) of from 2 cSt to 4.5 cSt (2-4.5 mm ² / s), preferably from 2.5 cSt to 4.0 cSt (2.5 -4.0 mm ² / s), more preferably from 2.9 cSt to 3.7 cSt (2.9-3.7 mm ² / s); and the sulfur content (ASTM D-2622) is 5 mg / kg or less, preferably 2 mg / kg or less.

The gas oil will accordingly have a flash point (ASTM D-92) of 100 ° C or higher, preferably 110 ° C or higher, for example, from 110 ° C to 120 ° C.

The term “gas oil fraction” may refer to a middle distillate fraction suitable for producing gas oil and / or kerosene and / or diesel fuel.

The heavy distillate fraction will have an intermediate boiling range. Such a fraction preferably has a distillation temperature of T90% by mass, from 400 ° C. to 550 ° C., preferably from 450 ° C. to 550 ° C. Optionally, at least a portion of the heavy distillate fraction can be recycled to step (a). For example, more than 15% of the mass., More than 30% of the mass., Or more than 40% of the mass., Or even more than 50% of the mass. heavy distillate fractions can be recycled to step (a). Usually, not more than 90% of the mass., More preferably not more than 80% of the mass., Even more preferably not more than 70% of the mass. heavy distillate fractions can be recycled to step (a). In one embodiment, the entire heavy distillate fraction can be recycled to step (a).

The residual fraction is the bottom fraction, which remains after atmospheric and vacuum distillation. The distillation temperature of 10% of the mass. said fraction is preferably above 400 ° C and most preferably above 500 ° C. The residual fraction has a distillation temperature T10% of the mass. from 200 ° C to 450 ° C, preferably from 300 ° C to 240 ° C. T10 is the temperature corresponding to atmospheric boiling point at which 10% of the total product is distilled off, as determined, for example, by gas chromatography, such as ASTM D7169. In step (c), a portion of the residual fraction is recycled to step (a). Preferably more than 20% by weight, more preferably more than 25% by weight, even more preferably more than 30% by weight, or even more preferably more than 40% by weight. the residual fraction can be recycled to stage (a). Typically, not more than 70% by weight, more preferably not more than 60% by weight, even more preferably not more than 50% by weight. the residual fraction can be recycled to stage (a). Alternatively, the entire residual fraction may be recycled to step (a).

The remainder of the residual fraction that is not recirculated is dewaxed in step (d) to obtain a residual base oil. Such dewaxing, or other dewaxing, known in the art, can also be carried out on heavy distillate fractions to produce distillate base oils. Preferably, more than 20% by weight, more preferably more than 30% by weight, and most preferably more than 40% by weight, and not more than 60% by weight, of the residual fraction is subjected to catalytic dewaxing in step (d). Stage (d) is carried out by catalytic dewaxing. Catalytic dewaxing can be carried out by any process in which the pour point of the base oil precursor fraction is lowered in the presence of a catalyst and hydrogen. Suitable dewaxing catalysts are heterogeneous catalysts comprising molecular sieves and, in some cases, in combination with a metal having hydrogenating activity, such as Group VIII metals. Molecular sieves and more preferably intermediate pore zeolites have shown good catalytic ability to lower the pour point of the base oil precursor fraction under catalytic dewaxing conditions. Preferably, intermediate pore zeolites have a pore diameter of from 0.35 nm to 0.8 nm. Suitable intermediate pore zeolites are mordenite, ZSM-5, ZSM-12, ZSM-22, ZSM-23, SSZ-32, ZSM-35, ZSM-48 or EU-2.

In the present invention, reference to ZSM-48 and EU-2 is used to indicate that all zeolites belonging to the ZSM-48 family of disordered structures, also called the * MRE family, and described in the Catalog of Disorder, can be used. in Zeolite Frameworks ”), published in 2000 on behalf of the Structural Commission of the International Zeolite Association. Even if it is believed that EU-2 is different from ZSM-48, both ZSM-48 and EU-2 can be used in the present invention. Zeolites ZBM-30 and EU-11 are very similar to ZSM-48, and are also considered zeolites, the structure of which belongs to the ZSM-48 family. In this application, any reference to zeolite ZSM-48 is also a reference to zeolite ZBM-30 and EU-11.

In addition to zeolite ZSM-48 and / or EU-2, other zeolites may be present in the catalyst composition, especially if it is necessary to modify its catalytic properties. It has been found that it may be preferable to have an existing ZSM-12 zeolite defined in the Database of Zeolite Structures published in 2007/2008 on behalf of the Structural Commission of the International Zeolite Association.

Another preferred group of molecular sieves are aluminosilicate phosphate (SAPO) materials, of which SAPO-11 is most preferred, for example, as described in US-A-4859311. Optionally, ZSM-5 in its HZSM-5 form can be used in the absence of any Group VIII metal. Other molecular sieves are preferably used in combination with the added Group VIII metal. Suitable Group VIII metals are nickel, cobalt, platinum and palladium. Examples of possible combinations are Pt / ZSM-35, Ni / ZSM-5, Pt / ZSM-23, Pd / ZSM-23, Pt / ZSM-48 and Pt / SAPO-11. Further details and examples of suitable molecular sieves and dewaxing conditions are described, for example, in WO-A-9718278, US-A-4343692, US-A-5053373, US-A-5252527 and US-A-4574043. The dewaxing catalyst also suitably contains a binder. The binder may be a synthetic or naturally occurring (inorganic) substance, for example clay, silica and / or metal oxides. Naturally occurring clays, for example, belong to the families of montmorillonite and kaolin. The binder is preferably a porous material, for example a refractory oxide, examples of which are: alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thorium dioxide, silica-beryllium dioxide, silica titanium dioxide, as well as ternary compositions, for example, silica-alumina-thorium dioxide, silica-alumina-zirconia, silica-alumina-magnesium oxide and silica-magnesium oxide led zirconium. More preferably, a binder material is used - a refractory oxide with low acidity, which is practically free of aluminum oxide. Examples of such binder materials are silicon dioxide, zirconia, titanium dioxide, germanium dioxide, boron oxide and mixtures of two or more components, examples of which are listed above. The first preferred binder is silica. A second preferred binder is titanium dioxide.

A preferred class of dewaxing catalysts includes the intermediate pore size zeolite crystallites described above and the low acidity refractory oxide binder material described above, which is substantially free of alumina, where the surface of the aluminosilicate zeolite crystallites is modified by subjecting the surface of the aluminosilicate zeolite crystallites to a dealumination treatment . A preferred dealumination treatment consists in contacting the binder and zeolite extrudate with an aqueous solution of a fluorosilicate salt, as described, for example, in US-A-5157191 or WO-A-0029511. Examples of suitable dewaxing catalysts described above are silica coupled and dealuminized Pt / ZSM-5, silica coupled and dealuminated Pt / ZSM-23, silica coupled and dealuminated Pt / ZSM-12 bonded to silica and dealuminated Pt / ZSM-12 / ZSM-22, which are described, for example, in WO-A-0029511 and EP-B-832171.

More preferably, the molecular sieve is MTW, MTT or TON type molecular sieve, or ZSM-48, or EU-2, examples of which are described above, the Group VIII metal is platinum or palladium, and the binder is silicon dioxide.

Preferably, the catalytic dewaxing of the residual fraction is carried out in the presence of the catalyst described above, wherein the zeolite has at least one channel with pores formed by 12-membered rings containing 12 oxygen atoms. Preferred zeolites having 12 membered rings are of the MOR type, MTW type, FAU type, or BEA type (according to the lattice type code). Preferably, MTW type zeolite is used, for example ZSM-12. A preferred catalyst containing MTW type zeolite also contains platinum or palladium as a Group VIII metal and a binder of silica or titanium dioxide. More preferably, the catalyst is a silica-bound AHS treated Pt / ZSM-12 zeolite-containing catalyst as described above. These 12-membered zeolite-type catalysts are preferred because they have been found to be suitable for converting waxy paraffin compounds to less waxy isoparaffin compounds. More preferably, the above-described catalyst containing a 12-membered zeolite is used in the first hydroconversion stage to lower the pour point of the residual fraction to an intermediate value between the pour point of the feed and the pour point of the final base oil. More preferably, the pour point of the intermediate is from -10 ° C to + 10 ° C. The process conditions in such a first step may correspond to the conditions for catalytic dewaxing, as described below. This first hydroconversion step is followed by the final dewaxing step, which preferably uses a catalyst that contains a zeolite having at least one channel with pores formed by 10-membered rings containing 10 oxygen atoms. Suitable zeolites with a 10 membered ring use zeolites from the following list, including types: TON, MFI, MTT or FER. A particular catalyst may be one of the catalysts described above that corresponds to these types of zeolites. A preferred catalyst containing a 10-membered zeolite will also contain platinum or palladium as a Group VIII metal and a silica binder. More preferably, the catalyst is a catalyst comprising Pt / ZSM-5, treated with AHS and bound to silicon dioxide, or Pt / ZSM-23, treated with AHS and linked to silicon dioxide, as described above.

Catalytic dewaxing conditions are known in the art and typically include operating temperatures in the range of 200 ° C to 500 ° C, preferably 250 ° C to 400 ° C, hydrogen pressure in the range of 10 to 200 bar (1.0-20 MPa) , preferably from 40 to 70 bar (4.0-7.0 MPa), hourly average feed rate (WHSV) in the range from 0.1 to 10 kg of oil per 1 liter of catalyst per hour (kg / l / h), preferably from 0.2 to 5 kg / l / h, more preferably from 0.5 to 3.0 kg / l / h, and a hydrogen / oil ratio in the range from 100 to 2000 l of hydrogen per 1 l of oil. By varying the temperature from 275 ° C, preferably from 315 ° C to 375 ° C, at a pressure of 40-70 bar (4.0-7.0 MPa), at the stage of catalytic dewaxing, base oils with various pour points varying from preferably + 10 ° C for heavier grades to -60 ° C for lighter grades. The residual base oil may preferably have a pour point below 0 ° C, preferably below -30 ° C, more preferably below -50 ° C.

The residual base oil obtained in step d) according to the method of the invention preferably has a kinematic viscosity at 100 ° C (VK100) above 15 cSt (15 mm ² / s), determined in accordance with ASTM D-445. More preferably, the kinematic viscosity of the inventive base oil at 100 ° C. (VK100) is at least 18 cSt (18 mm ² / s), even more preferably at least 21 cSt (21 mm ² / s), and even more preferably at least 23 cSt (23 mm ² / s). For example, the base oil may have VK100 in the range of 15-35 cSt (15-35 mm ² / s), preferably in the range of 15-30 cSt (15-30 mm ² / s), more preferably in the range of 19-30 cSt (19 -30 mm ² / s), more preferably in the range of 20-30 cSt (20-30 mm ² / s), more preferably in the range of 22-30 cSt (22-30 mm ² / s), more preferably in the range of 22- 26 centistokes (22-26 ^mm2 / s), and most preferably in the range of 24-26 centistokes (24-26 ^mm2 / s).

The kinematic viscosity described in the present invention is determined according to ASTM D-445.

The base oil obtained in stage d) in accordance with the method of the invention preferably contains molecules having a sequential number of carbon atoms, and preferably at least 95% of the mass. hydrocarbon molecules C30 +. More preferably, the base oil contains at least 75% of the mass. hydrocarbon molecules C35 +.

The term “cloud point” refers to the temperature at which a cloud point develops in a sample, which is determined according to ASTM D-5773. Base oil typically has a cloud point between 80 ° C and -60 ° C. Preferably, the base oil has a cloud point between 30 ° C and -55 ° C, more preferably between 10 ° C and -50 ° C. It was found that, depending on the feedstock and dewaxing conditions, some paraffin heavy base oils formed in the Fischer-Tropsch synthesis may have a cloud point above ambient temperature, while other characteristics are not negatively affected.

The term “pour point” refers to the temperature at which the flow of a base oil sample will begin under carefully controlled conditions. The pour point referred to herein is determined according to ASTM D 97-93. Molecular weights are determined according to ASTM D-2503. The viscosity index (VI) is determined using ASTM D-2270.

The residual base oil in accordance with the present invention preferably has a viscosity index in the range of 120-160. The residue will preferably not contain or will contain very few compounds containing sulfur and nitrogen. This is characteristic of the product obtained in the Fischer-Tropsch reaction, which uses synthesis gas with almost no impurities. Preferably, the residual base oil contains sulfur, nitrogen and metals in the form of compounds with hydrocarbons and is present in an amount of less than 50 ppm, more preferably less than 20 ppm, even more preferably less than 10 ppm. Most preferably, it will contain sulfur and nitrogen, typically below the detection limits, which are currently 5 ppm for sulfur and 1 ppm for nitrogen when, for example, X-ray or Antek analysis methods are used for determination Nitrogen. However, sulfur may enter the product using sulfidized hydrocracking / hydrodewaxing catalysts and / or sulfidized dewaxing catalysts.

In addition, it was found that, apparently, there is a correlation between the kinematic viscosity, pour point and the effect of lowering the pour point, which may have an isomerized bottoms product obtained in the Fischer-Tropsch synthesis. For a given composition of raw materials and a boiling temperature range (which is determined by the lower cut-off point of the distillate base oil and gas oil fractions after dewaxing) for the bottoms product, the pour point and the resulting viscosity are associated with the rigidity of the dewaxing treatment. It was found that the effect of lowering the pour point was significant for the isomerized bottoms obtained in the Fischer-Tropsch synthesis having a pour point above -28 ° C, an average molecular weight of between about 600 and 1100, and an average degree of branching of the molecules from about 6.5 to about 10 alkyl branches per 100 carbon atoms, as described in US-A-7053254. Obtained in the Fischer-Tropsch synthesis, the residual base oil according to the invention can be further characterized by the content of various carbon fragments in it. In particular, the residual base oil obtained in the Fischer-Tropsch synthesis can be characterized by the percentage of epsilon-methylene carbon atoms, i.e. by the percentage of secondary methylene carbon atoms that are four or more carbon atoms away from the end group and / or branch (additionally referred to as CH2> 4) compared to the percentage of isopropyl carbon atoms. It is found that the isomerized bottoms products of the Fischer-Tropsch synthesis described in US-A-7053254 differ from the paraffin components of the base oil formed in the Fischer-Tropsch synthesis obtained with increased dewaxing rigidity in that the latter compounds have a percentage of epsilon -methylene carbon atoms to carbon atoms in isopropyl branches equal to 8.2 or higher, which is measured for the entire base oil of the Fischer-Tropsch synthesis. It has been found that the measurable effect of lowering the pour point by mixing with the base component, which is described in US-A-7053254, is achieved only if in the base oil of the present invention, the ratio of the percentage fractions of epsilon-methylene carbon atoms to carbon atoms in isopropyl branches equal to 8.2 or more. It should be noted that where the effect of lowering the pour point is undesirable, the addition of a Fischer-Tropsch derived base oil having a lower pour point and a higher proportion of compounds that have a percentage of epsilon-methylene carbon atoms to atoms may be useful. carbon in isopropyl branches equal to 8.2 or more, since such mixtures are usually more homogeneous, which is expressed by lower cloud points. Thus, it is preferred that the Fischer-Tropsch derived residual base oil of the present invention has a pour point below -6 ° C, more preferably below -20 ° C, and most preferably below -28 ° C. Such component (b) does not have or only has a minor effect of lowering the pour point.

In a preferred embodiment of the present invention, the residual base oil obtained in step (d) is added to the gas oil fraction obtained in step (b). If only small amounts, preferably less than 5% of the mass. base oil is added to gas oil, more preferably less than 3% of the mass. base oil, even more preferably less than 2% of the mass. base oil, the quality of liquid gas oil fuel components is improved even further.

The method described above leads to the production of medium distillates with extremely good cold flow properties. For example, the cloud point of any gas oil fraction is usually below -18 ° C, often even below -24 ° C. The limit temperature of cold filterability (CFPP) is usually below -20 ° C, often -28 ° C or lower. Typically, the pour point is below -18 ° C, often below -24 ° C.

The present invention also relates to gas oil obtained by the method of the present invention. Gas oil has a pour point below -18 ° C and CFPP below -20 ° C. This gas oil can be mixed with mineral gas oil to improve the quality of the liquid fuel components of mineral gas oil, as well as reduce the amount of sulfur in mineral gas oil.

In FIG. 1 is a schematic flow chart of a preferred embodiment of a method in accordance with the present invention.

In the framework of this description, a single reference number will denote both pipelines and flows passing through these pipelines.

The technological scheme as a whole is indicated by position number 1.

In the Fischer-Tropsch process reactor 2, a Fischer-Tropsch product stream is obtained. This product 20 is fed to a hydrocracking / hydroisomerization reactor 3, in which part of it is converted to a product boiling below a temperature in the range of 300-450 ° C. under atmospheric conditions. The effluent from reactor 3 (not shown) is distilled in a distillation column (not shown) to recover a middle distillate or gas oil fraction 30, a heavy distillate fraction 40 and a residual fraction 50. A middle distillate fraction 30 is distilled in a distillation column 4 to obtain gas oil 60 and kerosene 70. The heavy distillate fraction 40 is fed to the catalytic dewaxing reactor 5 to obtain a distillate base oil 80. The stream 80 leaving the reactor 5 is distilled in a distillation column 6 to obtain additional base oils 90 with different kinematic viscosities at 100 ° C, from 2 to 10 mm ² / s, preferably from 2 to 8 mm ^{2 / s. A} portion of the residual fraction 50 is fed to the catalytic dewaxing reactor 7 to obtain a residual base oil 100 with kinematic viscosity at 100 ° C from 15 to 35 mm ^{2 / s. A} portion of the residual fraction 50A is recycled to reactor 3, combining 50A with Fischer-Tropsch product 20.

Below the present invention is described in the following examples, which are not intended to limit the scope of the invention in any way.

Examples

The C5-C750 ° C fraction + Fischer-Tropsch reaction product obtained in Example VII using the catalyst of Example III WO-A-9934917 was continuously fed to the hydrocracking step (step (a)). Raw materials contained approximately 60% of the mass. C30 + product. The ratio of C60 + / C30 + was approximately 0.55. In the hydrocracking step, this fraction was brought into contact with the hydrocracking catalyst of Example 1 of EP-A-532118. The effluent from step (a) was continuously distilled under vacuum to obtain a gas oil fraction, a heavy distillate fraction and a residual fraction. The yield and properties of gas oil are shown in table 1. The yield is given based on the feed supplied to the hydrocracking unit. 60% of the residual fraction was recycled to stage (a), and the rest was sent to stage (d) of catalytic dewaxing. The conditions of the hydrocracking stage (a) were as follows: hourly average fresh feed rate (WHSV) 0.6 kg / l⋅h, WHSV recycle feed 0.17 kg / l⋅h, hydrogen gas supply rate = 750 nl / kg, total pressure = 77 bar (7.7 MPa), temperature in the reactor 334 ° С.

At the stage of dewaxing, the residual fraction was brought into contact with dealuminated, associated with silicon catalyst ZSM-5, containing 0.7% of the mass. Pt and 30% of the mass. ZSM-5, as described in Example 9 of WO-A-0029511. The conditions for dewaxing were 40 bar (4.0 MPa) hydrogen, WHSV = 0.5 kg / l⋅h and a temperature of 320 ° C. The yield and properties of the resulting residual base oil are shown in table 1.

The heavy distillate fraction was subjected to a catalytic dewaxing step similar to that described above. The oil obtained as a result of catalytic dewaxing was distilled into three fractions of the base oil boiling in the ranges of 305-400 ° C, 400-480 ° C and above 480 ° C. The yield and properties of these three distillate base oils are shown in Table 1. The yield of distillate base oils based on the liquid feed to the catalytic dewaxing stage.

Comparative example

Example 1 was repeated except that 50% of the heavy distillate fraction was recycled instead of the residual fraction. The yield and properties of the gas oil fraction, residual base oil and distillate base oils are shown in table 2.

Discussion

In Tables 1 and 2 and by comparison of a comparative example in which the heavy distillate fraction is partially recycled to the hydrocracking / hydroisomerization step with Example 1 in accordance with the present invention, in which the residual fraction is partially recycled, it is shown that the overall liquid product yield increases with a higher amount of gas oil, the amount of distillate base oils increases, while still receiving a significant proportion of the residual base oil. In addition to this, the number of less attractive naphthas decreased.

Claims (18)

1. A method for producing a gas oil fraction, a heavy distillate fraction, and a residual base oil fraction from a Fischer-Tropsch derived raw material, comprising: (a) directing the feed to a hydroprocessing step to obtain at least partially isomerized feed; (b) separating the isomerized feed by distillation into at least a gas oil fraction, a heavy distillate fraction that has a distillation temperature of T90% wt. from 400 to 550 ° C, and a residual fraction, and the residual fraction has a distillation temperature of T10% wt. 200 to 450 ° C; (c) recycling from more than 20 to not more than 70% wt. residual fraction to stage (a); and (d) catalytic dewaxing of the remaining residual fraction to obtain a residual base oil. 2. The method according to claim 1, in which the gas oil fraction and the heavy distillate fraction are separated in stage (b) at a temperature of the separation border from 300 to 400 ° C. 3. The method according to claim 1 or 2, in which the heavy distillate fraction and the residual fraction are separated in stage (b) at a temperature of the separation border from 450 to 600 ° C. 4. The method according to p. 1 or 2, in which the raw material formed in the Fischer-Tropsch synthesis has an initial boiling point below 400 ° C and a final boiling point above 600 ° C. 5. The method according to p. 1 or 2, in which the fraction boiling at a temperature above 540 ° C in the feedstock in stage (a) is at least 20% wt. 6. The method according to p. 1 or 2, in which the residual base oil obtained in stage (d) has a kinematic viscosity at 100 ° C according to ASTM D-445 in the range of 15-35 cSt (15-35 mm ² / s) preferably in the range of 15-30 centistokes (15-30 ^mm2 / s), more preferably in the range of 19-30 centistokes (19-30 ^mm2 / s), more preferably in the range of 20-30 centistokes (20-30 ^mm2 / s), more preferably in the range of 22-30 cSt (22-30 mm ² / s), more preferably in the range of 22-26 cSt (22-26 mm ² / s) and most preferably in the range of 24-26 cSt (24 -26 mm ² / s). 7. The method according to p. 1 or 2, in which the base oil obtained in stage (d) has a cloud point between 80 and -60 ° C, determined according to ASTM D-5773. 8. The method according to claim 1 or 2, in which the base oil obtained in stage (d) has a pour point below 0 ° C, preferably below -30 ° C, more preferably below -50 ° C, determined according to ASTM D- 97-93. 9. The method according to p. 1 or 2, in which the base oil obtained in stage (d) has a viscosity index from 120 to 160, determined according to ASTM D-2270. 10. The method according to p. 1 or 2, in which to improve the quality of the liquid fuel components of gas oil to the gas oil fraction obtained in stage (b), add the residual base oil obtained in stage (d) in an amount of less than 5% wt. of the total number of gas oil and base oil fractions. 11. The method according to p. 1 or 2, in which the stage of dewaxing is carried out using the process of catalytic dewaxing in the presence of a catalyst containing a molecular sieve with an average pore size and a metal of group VIII. 12. The method according to claim 11, in which the molecular sieve is a molecular sieve of the type MTW, MTT, TON, or ZSM-48, or EU-2. 13. The method according to claim 11, in which the metal of group VIII is platinum or palladium. 14. The method according to claim 11, in which the catalyst used in the catalytic dewaxing of the residual fraction contains a molecular sieve MTW, platinum or palladium as a metal of group VIII and the binder is silicon dioxide or titanium dioxide.

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