CN1926220A - Process to continuously prepare two or more base oil grades and middle distillates - Google Patents

Abstract

A process for the simultaneous preparation of two or more base oil fractions and middle distillates from a deasphalted oil or vacuum distillate feedstock, or mixtures thereof, by carrying out the steps of: (a) hydrocracking the feedstock, whereby an effluent is obtained; (b) distilling the effluent obtained in step (a) into one or more middle distillates and a residue having a boiling point significantly above 340°C; (c) separating said residue into a light basis by a further distillation step an oil precursor fraction and a heavy base oil precursor fraction; (d) reducing the pour point of each separated base oil precursor fraction in two simultaneous and parallel operating catalytic dewaxing reactors to obtain a first and a second dewaxed oil; (e) hydrotreating the first dewaxed oil obtained when the heavy base oil precursor fraction is dewaxed in step (d); (f) from step (d) The second dewaxed oil of the light base oil precursor fraction and the hydrotreated oil from step (e) separate two or more base oil fractions.

Description

Process for the continuous preparation of two or more base oil fractions and middle distillates

technical field

The present invention relates to a process for the continuous preparation of two or more base oil fractions and middle distillates.

Background technique

WO-A-0250213 describes a process in which different base oil fractions are prepared in a so-called "modular" mode. In this process, the bottom fraction of the fuel hydrocracking process is separated into various base oil precursor fractions, from which the process also obtains middle distillates as products. These fractions were subsequently catalytically dewaxed sequentially using a platinum-ZSM-5 based catalyst.

WO-A-9718278 discloses a process in which up to 4 base oil fractions such as 60N, 100N and 150N are prepared starting from the bottoms fraction of a fuel hydrocracker. In this process, the bottoms fraction is fractionated into 5 fractions by vacuum distillation, of which the 4 heavier fractions are further processed into different base oil fractions by first undergoing catalytic dewaxing followed by hydrofinishing steps .

WO-A-02/50213 discloses a so-called "modular" process for the production of different base oil fractions from the bottoms fraction of a fuel hydrocracking process.

A disadvantage of the above method is that the process is discontinuous. In other words, the base oil fractions are not produced simultaneously but sequentially. When the hydrocracker bottoms fraction is fractionated and awaits catalytic dewaxing, the resulting intermediate product requires storage tanks. Another disadvantage is that the mode switching of device heating and device cooling can cause corrosion of the device. This paradigm shift also results in intermediate off-spec product each time a new fraction is processed. These substandard petroleum products need to be reprocessed or disposed of, which is disadvantageous.

EP-A-649896 discloses a process for producing a residue comprising base oil by a process comprising a hydrotreating step and a hydrocracking step of a heavy petroleum feedstock. The hydrotreatment step yields a product from which middle distillates and bottoms fractions (residues) are obtained. The bottoms fraction was subsequently solvent dewaxed into a monofraction base oil fraction.

EP-A-0272729 discloses a process for the production of lubricating base oils in which the flash produced by the resid conversion process is fed to a hydrocracker. The effluent from the hydrocracker is sent to a catalytic dewaxing unit, after which the entire dewaxed stream is optionally hydrotreated.

WO-A-9723584 discloses a process for subjecting the bottoms fraction of a fuel hydrocracker to a catalytic dewaxing step. The dewaxed oil is partly recycled to the hydrocracking step and partly obtained as lubricating base oil.

A disadvantage of the above method described in WO-A-9723584 is that a broad pour point distribution occurs if more than one base oil fraction is separated from the dewaxed oil. In other words, the resulting lower viscosity base oil fraction will have too low a pour point. This pour point sacrifices or differs from the desired value, indicating a loss in yield of the lower viscosity base oil fraction.

It is an object of the present invention to provide a process which enables the simultaneous preparation of two or more base oil fractions with their respective pour points closer to desired values.

Another object of the invention is to provide an alternative method.

Contents of the invention

The following methods achieve one or more of the above objects or other objects.

A process for the simultaneous preparation of two or more base oil fractions and middle distillates from deasphalted oil or vacuum distillate feedstocks or mixtures thereof by carrying out the following steps:

(a) hydrocracking the feed, thereby obtaining an effluent;

(b) distilling the effluent obtained in step (a) into one or more middle distillates and a residue having a boiling point significantly higher than 340°C;

(c) separating said resid by a further distillation step into a light base oil precursor fraction and a heavy base oil precursor fraction;

(d) reducing the pour point of each separated base oil precursor fraction in two simultaneous and parallel operating catalytic dewaxing reactors to obtain first and second dewaxed oils;

(e) hydrotreating the first dewaxed oil obtained when dewaxing the heavy base oil precursor fraction in step (d);

(f) separating two or more base oil fractions from the second dewaxed oil from the light base oil precursor fraction of step (d) and the hydrotreated oil from step (e).

Applicants have found that two or more base oil fractions can be produced continuously when processed according to the present invention and at the same time reduce the hydrotreating capacity because only the heavier fraction requiring further hydrotreating is subjected to the described step (e). Additionally, any product pour point sacrifice can be avoided because two dewaxing reactors operating in parallel can be operated such that the pour points of the resulting low and high viscosity base oil fractions are close to the desired values. Any sacrifice of pour point signifies a loss in yield of fractions below the desired pour point.

Detailed ways

The feed to step (a) can be any typical mineral crude derived feed to a hydrocracker. Such feeds may be vacuum gas oils or heavier fractions obtained by distillation under near-vacuum conditions of the atmospheric residue of crude mineral oil feeds. The deasphalted oil obtained during the deasphalting of the residue obtained in said vacuum distillation can also be used as feed. Light and heavy FCC oils obtained in fluid catalytic cracking processes (FCC), hot flash fractions and aromatic-rich fractions obtained in the solvent extraction processing step in conventional base oil processing can also be The extract was used as feed. Mixtures of the aforementioned feeds and optionally other hydrocarbon sources are also suitable as feeds. In addition to the above feed, another optional hydrocarbon source which may preferably be present in an amount of 2-30 wt% of the feed to step (a) is paraffin wax obtained in a Fischer-Tropsch process. Preferably, the feed to step (a) consists of a mineral crude derived feed.

Step (a) may be performed at a conversion of 15-90 wt%. Conversion is expressed as the weight percent of the fraction boiling above 370°C in the feed that is converted to products boiling below 370°C. The main products with a boiling point below 370°C are naphtha, kerosene and gas oil. Examples of possible hydrocracking processes suitable for carrying out step (a) are described in EP-A-699225, EP-A-649896, WO-A-9718278, EP-A-705321, EP-A-994173 and US- A-4851109.

The operating conditions of the single-step hydrocracking process preferably include: a temperature of 350-450° C.; a hydrogen pressure of 9-200 MPa, more preferably higher than 11 MPa; 0.1-10 kg oil/liter catalyst/hour (kg/l/hr ), preferably 0.2-5 kg/l/hr, more preferably 0.5-3 kg/l/hr; and a hydrogen-to-oil ratio of 100-2,000 liters of hydrogen per liter of oil.

Preferably, the hydrocracker is operated in two steps consisting of a prehydrotreatment step and a hydrocracking step. Nitrogen and sulfur are largely removed in the hydrotreating step, aromatics are largely saturated to naphthenes, and part of the naphthenes are converted to paraffins by ring-opening reactions. In order to increase the yield of the more viscous base oil fraction, it is more preferred to operate the fuel hydrocracker by first (i) hydrotreating the hydrocarbon feed at a conversion of the feed, where conversion as defined above less than 30wt%, preferably 15-25wt%, and (ii) hydrocracking the product of step (i) in the presence of a hydrocracking catalyst such that the combined conversion of steps (i) and (ii) is 15-90wt %, preferably 40-85 wt%.

The operating conditions of the hydrotreating step are preferably: a temperature of 350-450° C.; a hydrogen pressure of 9-200 MPa, more preferably higher than 11 MPa; a weight of 0.1-10 kg oil/liter catalyst/hour (kg/l/hr) Hourly Space Velocity (WHSV), preferably 0.2-5 kg/l/hr, more preferably 0.5-3 kg/l/hr; and a hydrogen to oil ratio of 100-2,000 liters of hydrogen per liter of oil.

The operating conditions of the hydrocracking step combined with the hydrotreating step are preferably: a temperature of 300-450° C.; a hydrogen pressure of 9-200 MPa, more preferably higher than 11 MPa; 0.1-10 kg oil/liter of catalyst/hour ( kg/l/hr), preferably 0.2-5 kg/l/hr, more preferably 0.5-3 kg/l/hr; and a ratio of hydrogen to oil of 100-2,000 liters of hydrogen per liter of oil.

The resid produced by the above method contains very low sulfur content (typically below 250 or even below 150 ppmw) and very low nitrogen content (typically below 30 ppmw). The resid is preferably a full range resid.

It has been found that by performing the combined hydrotreating and hydrocracking steps as described above, a resid is obtained which yields a substantial more viscous base oil fraction (also known as the middle engine oil fraction) and has an acceptable Viscosity Index Quality. In addition, sufficient quantities of naphtha, kerosene and gas oil are obtained by this method. This enables a fuel hydrocracker process in which products from naphtha to gas oil and a residue are obtained simultaneously, which can lead to a medium engine oil base oil fraction. The viscosity index of the resulting base oil fraction is suitably 95-120, which is acceptable for obtaining a base oil with a viscosity index of API Group II specification.

It has been found that the viscosity index of the resid and the resulting base oil fraction in the hydrotreating step (i) increases with the conversion in said hydrotreating step. By operating this hydrotreatment step at a high conversion of more than 30% by weight, it is possible to achieve viscosity index values of the resulting base oil well in excess of 120. However, such high conversions in step (i) have the disadvantage that the yield of the medium oil fraction would be undesirably reduced. Carrying out step (i) under the above-mentioned conversion rate level, can obtain the base oil of API Group II medium machine oil grade with desired amount. The minimum conversion in step (i) will be determined by the desired viscosity index of 95-120 for the resulting base oil fraction, and the minimum acceptable yield for the mid-motor oil fraction will be determined by the Maximum conversion rate.

The prehydrotreating step is generally carried out using the catalysts and conditions of the above publications related to hydrocracking. Suitable hydrotreating catalysts generally comprise a metal hydrogenation component, suitably a Group IVB or VIII metal such as cobalt-molybdenum, nickel-molybdenum, etc., on a porous support such as silica-alumina or alumina. The hydrotreating catalyst is suitably free of zeolitic material or present in low amounts of less than 1 wt%. Examples of suitable hydrotreating catalysts are: commercial ICR 106, ICR 120 from Chevron Research and Technology Co.; 244, 411, DN-120, DN-180, DN-190 and DN-200 from Criterion Catalyst Co.; Haldor Topsoe A/ TK-555 and TK-565 of S; HC-k, HC-P, HC-R and HC-T of UOP; KF-742, KF-752, KF-846, KF-848STARS and KF-849; and HR-438/448 from Procatalyse SA.

The hydrocracking step is preferably carried out in the presence of an acidic large pore zeolite contained within a porous support material, said catalyst having additional metal hydrogenation/dehydrogenation. The metal with hydrogenation/dehydrogenation is preferably a combination of Group VIII/VIB metals such as nickel-molybdenum and nickel-tungsten. The support is preferably a porous support such as silica-alumina and alumina. It has been found that in order to achieve high yields of medium engine oil fractions in full range residues when operating the hydrocracker at the preferred conversions as described above, it is advantageous to have a minimum amount of zeolite in the catalyst. Preferably, more than 1% by weight of zeolite is present in the catalyst. Examples of suitable zeolites are zeolites X, Y, ZSM-3, ZSM-18, ZSM-20 and zeolite beta, of which zeolite Y is most preferred. Examples of suitable hydrocracking catalysts are commercial ICR 220 and ICR 142 from Chevron Research and Technology Co.; Z-763, Z-863, Z-753, Z-703, Z-803, Z-733, Z-723, Z-673, Z-603 and Z-623; TK-931 from Haldor Topsoe A/S; DHC-32, DHC-41, HC-24, HC-26, HC-34 and HC-43 from UOP ; KC2600/1, KC2602, KC2610, KC2702, and KC2710 from AKZO Nobel/Nippon Ketjen; and HYC642 and HYC652 from Procatalyse SA.

The effluent from the hydrocracker is separated into one or more of the aforementioned fuel fractions and a residue. Wherein the residual oil mainly boils above 340° C., which is used as the feed of step (c). Predominantly boiling above 340°C means in particular that more than 80% by weight of the substance boils above 340°C, preferably more than 90% by weight of the substance boils above 340°C. Since most of the resid can boil in the gas oil boiling range, a considerable amount of gas oil with good cold flow properties can be recovered after dewaxing. Preferably, 10-40 wt% of the dewaxed oil obtained in the process boils in the heavy gas oil boiling range of 350-400°C. It should of course be understood that in step (c) a lower boiling gas oil fraction is also obtained.

The final boiling point of the resid will be determined in part by the final boiling point of the feed to step (a) and can be much greater than 700°C, up to the point where it cannot be measured by standard test methods.

Part of the residue obtained in step (b) may optionally be recycled to step (a) as described in EP-A-0994173, which publication is hereby incorporated by reference. The resid may optionally only be recycled to the hydrocracking step of step (a) as described in EP-B-0699225, which publication is hereby incorporated by reference. Preferably less than 15 wt% of the resid is recycled to step (a), more preferably no resid is recycled to step (a). It has been found that API Group II base oils of good quality can be produced without such recycling being necessary.

In step (c), the feed is separated by distillation into a light base oil precursor fraction and a heavy base oil precursor fraction and optionally a vacuum gas oil fraction. Preferably, any vacuum gas oil is not separated from the light base oil precursor fraction but remains combined with said fraction, thereby also being dewaxed in step (d). Distillation is suitably carried out under reduced pressure, more preferably vacuum distillation at a pressure of 0.01-0.3 bar. Preferably, the recovery point of 10 wt% of the heavy base oil precursor fraction obtained in step (c) is 420-550°C, more preferably 440-520°C.

The feed to step (d) will comprise the base oil precursor fraction obtained in step (c). Optionally, some partially isomerized paraffins boiling in the heavy or light base oil precursor fraction boiling range may be present in admixture with the light base oil precursor fraction. This paraffinic product as obtained in the Fischer-Tropsch or gas-liquid process is also called waxy raffinate. Such waxy residues may be prepared as described in WO-02070630, which publication is incorporated herein by reference.

Optionally, a noble metal guard bed may be placed just upstream of the dewaxing catalyst bed in the dewaxing reactor in step (d) to reduce the content of sulfur and especially nitrogen compounds. Such guard beds may be particularly advantageous in dewaxing reactors processing heavy base oil precursor fractions. Examples of such methods are described in WO-A-9802503, which reference is hereby incorporated by reference.

The catalytic dewaxing step carried out in step (d), operating in parallel operating reactors, may be carried out by any method which lowers the pour point of the base oil fraction in the presence of a catalyst and hydrogen. Suitably, the pour point is lowered by at least 10°C, and more suitably by at least 20°C. Suitable dewaxing catalysts are heterogeneous catalysts comprising molecular sieves, optionally in combination with metals having a hydrogenation effect, such as Group VIII metals. Molecular sieves, more suitably intermediate pore size zeolites, exhibit good catalytic ability to lower the pour point of base oil fractions under catalytic dewaxing conditions. Preferably, the intermediate pore size zeolite has a pore size of 0.35-0.8 nm. Suitable intermediate pore size zeolites are ZSM-5, ZSM-12, ZSM-22, ZSM-23, SSZ-32, ZSM-35 and ZSM-48. Another preferred group of molecular sieves are the silico-aluminophosphate (SAPO) materials described in US-A-4859311, of which SAPO-11 is most preferred. ZSM-5 can be used optionally in its HZSM-5 form in the absence of any Group VIII metals present. Other molecular sieves are preferably used in combination with added Group VIII metals. Suitable Group VIII metals are nickel, cobalt, platinum and palladium. Examples of possible combinations are 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 eg described in WO-A-9718278, US-A-5053373, US-A-5252527 and US-A-4574043.

The process of the present invention allows the continuous production of base oils using dewaxing catalysts which exhibit a relatively broad pour point distribution in the case of processing full range residues as described in WO-A-9723584. By utilizing the present invention, such broad pour point distributions can be avoided despite the use of such relatively poor performing dewaxing catalysts. An example of such a catalyst exhibiting a relatively broad pour point distribution is a ZSM-5 based catalyst. ZSM-5 based catalysts can therefore be advantageously used in the present invention. The process also allows the use of different dewaxing catalysts in reactors operating in parallel, which catalysts may be better suited to their respective feeds.

Suitably, the dewaxing catalyst further comprises a binder. Binders may be synthetic or naturally occurring (inorganic) substances, such as clays, silicas and/or metal oxides. Naturally occurring clays are, for example, the montmorillonite and kaolin series. The binder is preferably a porous binder material such as a refractory oxide, examples of which are: alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria , silica-beryllia, silica-titania and ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and Silica-magnesia-zirconia. More preferably, a low acid refractory oxide binder material substantially free of alumina is used. Examples of such binder materials are silica, zirconia, titania, germania, boria and mixtures of two or more of these whose examples are listed above. The most preferred binder is silica.

A preferred class of dewaxing catalysts comprises medium zeolite crystals as described above and a substantially alumina-free low acidity refractory oxide binder material as described above wherein the aluminosilicate zeolite crystals are surface dealuminated by Treatment to modify the surface of aluminosilicate zeolite crystals. A preferred dealumination treatment is eg described in US-A-5157191 by contacting the extrudate of binder and zeolite with an aqueous solution of fluorosilicate. Examples of suitable dewaxing catalysts as described above are silica bound and dealuminated Pt/ZSM-5, silica bound and dealuminated Pt /ZSM-23, silica bound and dealuminated Pt/ZSM-12, and silica bound and dealuminated Pt/ZSM-22.

Catalytic dewaxing conditions are well known in the art and typically include: an operating temperature of 200-500°C, suitably 250-400°C; a hydrogen pressure of 10-200 bar; 0.1-10 kg oil/liter catalyst/hour ( kg/l/hr), suitably 0.2-5kg/l/hr, more suitably 0.5-4kg/l/hr; and 100-2,000 liters of hydrogen/hydrogen per liter of oil and ratio of oil. The weight hourly space velocity (WHSV) in the catalytic dewaxing step where the light base oil precursor fraction is processed is preferably higher than the WHSV in the dewaxing step of the heavy base oil precursor fraction. More preferably, the WHSV in the dewaxing step of the light base oil precursor fraction is 1-5 kg/l/hr.

If the dewaxing step is cascaded with the hydrofinishing step, the pressure levels in both steps are suitably of the same order of magnitude. Since higher pressures are preferred in the hydrofinishing step to obtain base oils with the desired properties, the dewaxing step is also suitably performed at this higher pressure, although more selectivity can be achieved at lower pressures of dewaxing. Lower catalytic dewaxing pressures may be advantageously used if no hydrofinishing step is required, as is the case for obtaining dewaxed oil from light base oil precursor fractions to produce spindle oil base oil fractions. A suitable pressure is 15-100 bar, more suitably 1.5-6.5 MPa.

The hydrotreating step (e) is also referred to as a hydrofinishing step improving the quality of the dewaxed fraction. In this step, lube range olefins are saturated, heteroatoms and colored species are removed and, if the pressure is high enough, residual aromatics are also saturated. The conditions are preferably chosen so as to obtain a base oil fraction comprising more than 95 wt% saturates, more preferably a base oil comprising more than 98 wt% saturates. The hydrofinishing step is conveniently carried out in cascade with the dewaxing step of the heavy base oil precursor fraction.

The hydrofinishing step is suitably carried out at a temperature of 230-380° C.; at a total pressure of 1-25 MPa (preferably higher than 10 MPa, more preferably 12-25 MPa). WHSV (weight hourly space velocity) is 0.3-10 kg oil/liter catalyst/hour (kg/l.h).

The hydrofinishing or hydrogenation catalyst is suitably a supported catalyst comprising a dispersed Group VIII metal. Possible Group VIII metals are cobalt, nickel, palladium and platinum. The cobalt and nickel containing catalyst may also contain Group IVB metals, suitably molybdenum and tungsten.

Suitable supports or support materials are low acidity amorphous refractory oxides. Examples of suitable amorphous refractory oxides include inorganic oxides such as alumina, silica, titania, zirconia, boria, silica-alumina, fluorinated alumina, fluorinated dioxide Silica-alumina and mixtures of two or more of these.

Suitable hydrogenation catalysts include: one or more of nickel (Ni) and cobalt (Co) comprising 1 to 25 weight percent (wt %), preferably 2 to 15 wt %, relative to the total weight of the catalyst on an elemental basis species, and those catalysts having one or more Group VIB metal components in an elemental amount of 5-30 wt%, preferably 10-25 wt%, relative to the total weight of the catalyst. Examples of suitable nickel-molybdenum containing catalysts are KF-847 and KF-8010 (AKZO Nobel), M-8-24 and M-8-25 (BASF), and C-424, DN-190, HDS-3 and HDS-4 (Criterion). Examples of suitable nickel-tungsten containing catalysts are NI-4342 and NI-4352 (Engelhard), C-454 (Criterion). Examples of suitable cobalt-molybdenum containing catalysts are KF-330 (AKZO-Nobel), HDS-22 (Criterion) and HPC-601 (Engelhard).

In the present invention, preferably platinum-containing and more preferably platinum and palladium-containing catalysts are used in hydrocracking feeds containing low amounts of sulfur. The total amount of these Group VIII noble metal components present in the catalyst is suitably 0.1-10 wt%, preferably 0.2-5 wt%, the weight percentages expressing the amount of metal (as an element) relative to the total weight of the catalyst.

A preferred support for these palladium and/or platinum containing catalysts is amorphous silica-alumina, wherein more preferably the silica-alumina comprises 2 to 75 wt% alumina. Examples of suitable silica-alumina supports are disclosed in WO-A-9410263. A preferred catalyst comprises an alloy of palladium and platinum, preferably supported on an amorphous silica-alumina support, examples of which are commercially available as catalysts C-624 and C-654 from Criterion Catalyst Company (Houston, TX). .

In step (f), two or more base oil fractions and optionally comprising Fractions of gas oil. The base oil and optionally the gas oil containing fraction are preferably separated from the mixture of these streams. This is advantageous because any compounds present in the heavy base oil precursor fraction converted to the light base oil fraction boiling range in step (d) will contribute to the light base oil fraction base oil yield.

Since the gas oil product obtained above has been subjected to a catalytic dewaxing step, a fuel product with very low aromatics and sulfur content combined with excellent low temperature properties is obtained. In particular, very low sulfur content below 10 ppm, low aromatics content below 0.1 mmol/100 g, good cold flow properties such as pour point below -30°C and below Gas oil with cold filter plugging point at -30°C. The gas oil also has excellent lubricating properties. This makes these gas oils particularly good refinery blending components to blend into low sulfur gas oils. The gas oil can also be used as a drilling mud component, electrical insulating oil, cutting oil, aluminum rolling oil or as a fruit spray oil.

Step (f) can be carried out by withdrawing the product from the rectification column under near vacuum conditions known to those skilled in the art. Preferably a so-called side stripper is used to separate out the base oil product. In order to meet the volatility requirements of the desired base oil fraction, an intermediate fraction can also be withdrawn. The aforementioned low pressure distillation step may conveniently be preceded by a higher pressure distillation step at about atmospheric conditions to separate any naphtha, kerosene and gas oil fractions, either individually or as a mixture, from the dewaxed oil. These middle distillates can be used as such or recycled to step (b) to obtain a mixture of dewaxed and hydrocracked middle distillate fuels. Thus in step (f), a gaseous overhead fraction, a liquid overhead fraction comprising the above-mentioned middle distillates and various base oil fractions such as spindle oil, light machine oil and medium base oil etc.

In the context of the present invention, the terms "spindle oil", "light machine oil" and "medium machine oil" refer to base oil fractions with increasing kinematic viscosity at 100°C and in which the spindle oil additionally has the greatest volatility Specification. The advantages of the present approach are realized for any set of base oils with these different viscosity requirements and volatility specifications. Preferably the spindle oil is a light base oil product with a kinematic viscosity below 5.5 cSt and preferably above 3.5 cSt at 100°C. The spindle oil may have a Noack volatility preferably below 20% and more preferably below 18% as measured by the CEC L-40-T87 method, or a flash point above 180°C as measured by ASTM D93. Preferably, the light motor oil has a kinematic viscosity at 100°C below 9 cSt and preferably above 6.5 cSt, more preferably between 8 and 9 cSt. Preferably, the medium motor oil has a kinematic viscosity at 100°C below 14 cSt and preferably above 10 cSt, more preferably between 11 and 13 cSt. The corresponding base oil fractions may have a viscosity index of 95-120. The gas oil obtained in the process of the invention typically has a boiling point of 150-370°C and a T90wt% of 340-400°C.

The method of the present invention is further illustrated by FIG. 1 . Figure 1 shows the hydrocarbon feed line (1 ) of the hydrocracker (2). In the distillation column (4) the hydrocracked product (3) is separated into naphtha (5), kerosene (6), gas oil (7), bottom fraction (8). The bottoms fraction or full range residue (4) is divided in a distillation column (9) into a light base oil precursor fraction (10) and a heavy base oil precursor fraction (11). The light base oil precursor fraction (10) is dewaxed in a dewaxing reactor (12) to obtain a dewaxed oil (16; "second dewaxed oil"). The heavy base oil precursor fraction (11) is dewaxed in a dewaxing reactor (13). The dewaxed oil (15; "first dewaxed oil") is hydrotreated in a hydrofinishing reactor (14) to obtain a dewaxed and hydrotreated oil (17). Combine oils (16) and (17). The hydrogen ( 19 ) is separated in the separator ( 18 ) and recycled to the dewaxing units ( 12 ) and ( 13 ) after feeding with fresh hydrogen ( 20 ). The oil ( 21 ) is subsequently separated in a distillation column ( 22 ) into a low boiling fraction ( 26 ), a spindle oil fraction ( 23 ), a light engine oil fraction ( 24 ) and a medium engine oil fraction ( 25 ). The fraction (26) is recycled to the processing section of the hydrocracker (2) to separate the valuable fuel fraction.

Claims (10)

1. prepare the method for two or more base oil fractions and middle runnings by carrying out following steps simultaneously by deasphalted oil or the charging of vacuum cut or their mixture:

(a), obtain effluent thus with the charging hydrocracking;

(b) effluent that obtains in the step (a) is distilled into one or more middle runningss and boiling point apparently higher than 340 ℃ residual oil;

(c) by further distilation steps described residual oil is separated into lighter body precursor fraction and heavy base oil precursor fraction;

(d) pour point of each isolating base oil precursor fraction of reduction in the catalytic dewaxing reactor of two whiles and parallel running obtains first and second pressed oils;

(e) the first pressed oil hydrotreatment that will obtain in the time of will in step (d), making the dewaxing of heavy base oil precursor fraction;

(f) from going out two or more base oil fractions from second pressed oil of the lighter body precursor fraction of step (d) with from the hydrotreatment of step (e) is separating of oil.

2. the method for claim 1, wherein the residual oil that obtains in step (b) is higher than 340 ℃ above the boiling point of 80wt%, and the first and second pressed oil meter 10-40wt% boiling points that wherein made in step (d) based on combination are lower than 400 ℃ heavy gas oil boiling range fraction.

3. each method of claim 1-2, wherein the heavy base oil precursor fraction that obtains in step (c) with 20-40wt% is recycled to step (a).

4. each method of claim 1-3, wherein the recovery point of the heavy base oil precursor fraction that obtains in step (c) of 10wt% is 420-550 ℃.

5. the method for claim 4, wherein the recovery point of the heavy base oil precursor fraction that obtains in step (c) of 10wt% is 440-520 ℃.

6. each method of claim 1-5, wherein the charging of step (d) also be included in obtain in the Fischer-Tropsch process and boiling point be in the isomerized paraffin of part in heavy and/or the lighter body precursor fraction boiling range.

7. each method of claim 1-6 wherein is higher than in dewaxing step (d) WHSV when the timesharing of processing heavy base oil precursor level when the weight hourly space velocity of processing lighter body precursor level timesharing in catalytic dewaxing step (d).

8. the method for claim 7, wherein the WHSV when the timesharing of processing lighter body precursor level is 1-5kg/l/hr.

9. each method of claim 1-8 is the 15-65 crust with the pressure of lighter body precursor fraction dewaxing in step (d) wherein, is the 100-250 crust with the pressure of heavy base oil precursor fraction dewaxing.

10. each method of claim 1-9, wherein the mixture implementation step (f) of first pressed oil of second pressed oil that timesharing obtains to processing lighter body precursor level and processing heavy base oil precursor level timesharing hydrotreatment.