EP2992070A2

EP2992070A2 - Process for preparing a heavy base oil

Info

Publication number: EP2992070A2
Application number: EP14720073.7A
Authority: EP
Inventors: Laurent Georges Huve; John Joseph Baric; Nariman Boumendjel; Jakob Willem Duininck; Godfried Johannes Aarts
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2013-05-02
Filing date: 2014-04-22
Publication date: 2016-03-09
Also published as: WO2014177424A3; RU2671862C2; CN105209580B; WO2014177424A2; RU2015151620A3; RU2015151620A; CN105209580A; KR20160003203A

Abstract

The invention provides a process for preparing a heavy base oil comprising the steps of: (a) providing a hydrocarbonaceous feedstock which contains at least 50% by weight of hydrocarbons boiling above 460 °C, nitrogen in amount in the range of from 800-2500 ppmw, and sulphur in an amount in the range of from 1.5-4.0 %wt ppmw; (b) hydrotreating the hydrocarbonaceous feedstock with a hydrotreating catalyst in the presence of a hydrogen- containing gas under hydrotreating conditions to obtain a hydrotreated product which contains nitrogen in an amount in the range of from 30-80 ppmw and sulphur in an amount in the range of from 200-450 ppmw; (c) removing at least 50% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b); (d) catalytically dewaxing at least part of the hydrotreated product as obtained in step (c) with a dewaxing catalyst in the presence of a hydrogen- containing gas under catalytic dewaxing conditions to obtain a dewaxed product, which dewaxing catalyst comprises a Group VIII metal hydrogenation component, dealuminated aluminosilicate zeolite crystallites and a low acidity refractory oxide binder material which is essentially free of alumina; (e) hydrofinishing at least part of the dewaxed product as obtained in step (d) with a hydrofinishing catalyst in the presence of a hydrogen-containing gas under hydrofinishing conditions to obtain a heavy base oil; and (f) recovering the heavy base oil.

Description

PROCESS FOR PREPARING A HEAVY BASE OIL

Field of the Invention

The present invention relates to a process for preparing a heavy base oil.

Background of the Invention

A major application of base oils is their use in lubricants such as motor oils to protect the internal combustion engines in motor vehicles. The lubricants are generally composed of a majority of base oil and a variety of additives to obtain the desired properties.

Light lubricating base oils are mainly used in automotive applications and heavy lubricating base oils are used in heavy duty applications such as ship engines and industrial processes.

Base oils for use in lubricants are on a large scale prepared by firstly hydrotreating a vacuum gas oil distillate and/or a deasphalted oil and by subsequently catalytically dewaxing and hydrofinishing of the

hydrotreated liquid product or the 370 °C plus fraction of the hydrotreated liquid product. Generally a noble metal dewaxing catalyst is applied in the catalytic dewaxing step. Noble metal dewaxing catalysts are well known to be poisoned by organic nitrogen and organic sulphur compounds and therefore a severe hydrotreating step has to be applied in order to sufficiently reduce the levels of organic nitrogen and organic sulphur compounds in the 370 °C plus product of the hydrotreater .

Generally, a higher treating severity in the

hydrotreater improves the quality of the 370 °C plus hydrotreated product which serves as feedstock for a base oil plant. However, a higher hydrotreating severity means that the yield of the 370 °C plus hydrotreated product becomes lower and the overall hydrotreated product lighter (boiling point shift due to severe

hydrotreatment ) , which, as a consequence, reduces substantially the ratio of heavy lubricating base oils over light lubricating base oils.

A reduction of the yield of heavy lubricating base oils is undesirable in periods that there is a high demand for heavy base oils.

Object of the present invention is therefore to provide an upgrading process for hydrocarbonaceous feedstocks in which a high yield of heavy lubricating base oils is obtained.

Summary of the invention

This object is achieved when a hydrocarbonaceous feedstock is subjected to an upgrading process which comprises a particular sequence of processing steps.

Accordingly, the present invention relates to a process for preparing a heavy base oil comprising the steps of:

(a) providing a hydrocarbonaceous feedstock which

contains at least 50% by weight of hydrocarbons boiling above 460 °C, nitrogen in amount in the range of from 800-2500 ppmw, and sulphur in an amount in the range of from 1.2 to 4.0 %wt;

(b) hydrotreating the hydrocarbonaceous feedstock with a hydrotreating catalyst or hydrotreating catalyst package in the presence of a hydrogen-containing gas under hydrotreating conditions to obtain a hydrotreated product which contains nitrogen in an amount in the range of from 30-80 ppmw and sulphur in an amount in the range of from

200-450 ppmw; (c) removing at least 50% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b) ;

(d) catalytically dewaxing at least part of the

hydrotreated product as obtained in step (c) with a dewaxing catalyst in the presence of a hydrogen- containing gas under catalytic dewaxing conditions to obtain a dewaxed product, which dewaxing catalyst

comprises a Group VIII metal hydrogenation component, dealuminated aluminosilicate zeolite crystallites and a low acidity refractory oxide binder material which is essentially free of alumina;

(e) hydrofinishing at least part of the dewaxed product as obtained in step (d) with a hydrofinishing catalyst in the presence of a hydrogen-containing gas under

hydrofinishing conditions to obtain a heavy base oil; and

(f) recovering the heavy base oil.

In accordance with the present invention a high yield of heavy lubricating base oils can be obtained. The heavy lubricating base oils obtained include Group II and Group

III lubricating base oils having a high ratio of heavy lubricating base oils over light lubricating base oils. Such heavy lubricating base oils have a high viscosity making them very attractive for heavy duty applications. Detailed description of the invention

The hydrocarbonaceous feedstock as provided in step (a) preferably contains more than 65%, but at least 50% by weight of hydrocarbons boiling above 460°C. Suitably, the hydrocarbonaceous feedstock as provided in step (a) has a 370 °C plus fraction that has a viscosity at 100 °C of above 12 cSt, preferably at least 14 cSt.

The hydrocarbonaceous feedstock contains nitrogen in an amount in the range of from 800-2500 ppmw, preferably in the range of from 1000-1500 ppmw, and sulphur in an amount in the range of from 1.2 to 4.0 %wt, preferably in the range of from 1.5 - 3.0 %wt

In the hydrocarbonaceous feedstock as provided in step (a) the ratio of the fraction of hydrocarbons boiling in the range of from 370-460 °C and the fraction of hydrocarbons boiling in the range of from 460 to 800°C is preferably less than 10.

Examples of the hydrocarbonaceous feedstock to be used in accordance with the present invention are straight-run gasoil, hydrocracked gasoil, thermal cracked gasoil, coker gasoil, vacuum gasoil, light or heavy cycle oil, deasphalted oil (DAO) or a combination of two or more thereof. The hydrocarbon feedstock may also be a solvent extracted waxy raffinate. At least part of the

hydrocarbonaceous feedstock as provided in step (a) can suitably be a blend obtained by blending at least one distillate fraction, preferably a vacuum distillate fraction, and a deasphalted oil (DAO) . The DAO that can be used is suitably obtained by deasphalting a residual hydrocarbon oil, preferably a vacuum residue. The

deasphalting step may be carried out in any conventional manner. A well known and suitable deasphalting method is solvent deasphalting, which involves the counter-current treatment of the residual hydrocarbon oil feed with an extracting solvent. This extracting solvent usually is a light hydrocarbon solvent containing paraffinic compounds having 3 to 8 carbon atoms, such as propane, butane, isobutane, pentane, isopentane, hexane and mixtures of two or more of these. Preferred paraffinic hydrocarbons are those having 3 to 5 carbon atoms with propane, butane, pentane and mixtures thereof being most

preferred. The solvent deasphalting treatment is conveniently carried out in a rotating disc contactor or a plate column with the residual hydrocarbon oil feed entering in the top section and the extracting solvent entering in the bottom section. The lighter hydrocarbons present in the residual hydrocarbon oil dissolve in the extracting solvent and are withdrawn at the top of the apparatus. From this top-fraction, the DAO is obtained after recovery of the extracting solvent. The

asphaltenes, which are insoluble in the extracting solvent, are withdrawn at the bottom of the apparatus.

The conditions under which deasphalting takes place are known in the art. Suitably, deasphalting is carried out at a total extracting solvent to residual hydrocarbon oil ratio of 1.5-8 wt/wt, a pressure of 1-50 bar and a temperature of 50-230 °C.

The deasphalted oil may be obtained by deasphalting a residue fraction, preferably a vacuum residue fraction, containing hydrocarbons that have a boiling point of at least460 °C.

In step (b) , the hydrocarbonanceous feedstock is hydrotreated with a suitable hydrotreating catalyst or hydrotreating catalyst package in the presence of a hydrogen-containing gas under hydrotreating conditions to obtain a hydrotreated product which contains nitrogen in an amount in the range of from 30-80 ppmw and sulphur in an amount in the range of from 200-450 ppmw.

The hydrotreating catalyst or catalyst package to be used in the first reaction zone in step (a) can suitably be a desulphurisation catalyst or a combination of desulphurisation catalysts (including a possible

demetallisation catalyst or demetallisation catalyst combination prior to the desulphurisation step) . The desulphurisation catalyst may be any hydrodesulphurisation catalyst known in the art or combination of hydrotreating catalysts that will deliver hydrotreated effluent with the prescribed levels of nitrogen and sulphur. Typically, these catalysts comprise a Group VIII metal of the Periodic Table and a compound of a Group VIB metal of the Periodic Table as

hydrogenation components on a porous catalyst support, usually alumina or amorphous silica-alumina. Well-known examples of suitable combinations of hydrogenation compounds are cobalt-molybdenum, nickel-molybdenum, nickel-tungsten, and nickel-cobalt-molybdenum. A

hydrodesulphurisation catalyst comprising compounds of nickel and/or cobalt and molybdenum as hydrogenation compounds is preferred. The hydrotreated product as obtained in step (b) contains nitrogen in an amount in the range of from 30-80 ppmw and sulphur in an amount in the range of from 200-450 ppmw, which means that the hydrotreating in step (b) is not a severe hydrotreating process. Suitably therefore use is made of hydrotreating catalysts or hydrotreating catalyst combinations that are not too active. Therefore, preferably use is made of an alumina-based hydrotreating catalyst. Preferably, the catalyst is substantially free of a cracking component. A catalyst or combination of catalysts comprising nickel and/or cobalt and molybdenum supported on alumina without a zeolitic cracking compound is particularly preferred.

In step (b) also use can be made of stacked-bed configurations in which two or more hydrotreating

catalyst are stacked.

The temperature in the hydrotreating step is suitably in the range of from 250-480 °C, preferably in the range of from 280-450 °C, and more preferably in the range of from 350-420 °C. Suitable hydrotreating pressures are in the range of from 30-250 bara. Preferably, the hydrotreating pressure is in the range of from 110 to 180 bara, more preferably in the range of from 120 to 170 bara.

The weight hourly space velocity is suitably in the range of from 0.2-10 hr^-1, preferably in the range of from 0.2-2.0 hr^-1, and more preferably in the range of from 0.2-1.0 hr^"1.

It will be appreciated that the exact hydrotreating conditions in step (a) will inter alia depend on the catalyst used, and the sulphur content and nitrogen content of the hydrocarbon feedstock.

The ratio of the amount of nitrogen and the amount of sulphur (N/S) in the hydrotreated product as obtained in step (b) is suitably in the range of from 0.1-0.3, preferably in the range of from 0.12-0.28

In step (c) , at least 50% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b) is removed. Suitably, at least part of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b) is removed by means of stripping, preferably steam stripping. Suitably, the stripping is carried out at a temperature ranging from 100 to 350C, preferably from 130 to 240C and a pressure ranging from 1 to 50 bar, preferably from 1.5 to 10 bar. Preferably at least 80%, more preferably at least 90%, and most

preferably at least 95% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b) is removed from the hydrotreated product in step (c) . Preferably in step (c) also hydrocarbons boiling below

370 °C are separated from the hydrotreated product as obtained in step (b) .

Preferably, the entire hydrotreated product as obtained in step (b) is subjected to step (c) .

In step (d) , at least part of the hydrotreated product as obtained in step (c) is catalytically dewaxed with a dewaxing catalyst in the presence of a hydrogen- containing gas under catalytic dewaxing conditions to obtain a dewaxed product, which dewaxing catalyst comprises a Group VIII metal hydrogenation component, dealuminated aluminosilicate zeolite crystallites and a low acidity refractory oxide binder.

Preferably, the entire hydrotreated product as obtained in step (c) is subjected to step (d) .

By catalytic dewaxing is here meant a process for decreasing the pour point of lubricating base oil products by selectively converting the components of the oil feed which impart a high pour point to products which do not impart a high pour point. Products which impart a high pour point are compounds having a high melting point. These compounds are referred to as waxes. Wax compounds include for example high temperature melting normal paraffins, iso-paraffins and mono-ringed

compounds. The pour point is preferably reduced by at least 40 °C and more preferably by at least 60 °C. The hydrocarbonacous feedstock in the process according to the present invention will thus contain waxy molecules which impart an undesirable high pour point. Small amounts of these compounds can strongly influence the pour point. The feedstock will suitably contain between less than 2% and up to 80% of these waxy compounds.

In the catalytic dewaxing step in accordance with the invention the hydrotreated feedstock is contacted under catalytic dewaxing conditions with a catalyst composition comprising a Group VIII metal hydrogenation component, dealuminated aluminosilicate zeolite crystallites and a low acidity refractory oxide binder.

It has been found that this type of dewaxing catalyst is very stable over time even though a high content of sulphur and nitrogen is present in the oil feed. Examples of such catalysts are described in WO-A-9641849.

The aluminosilicate zeolite crystallites preferably have pores with a diameter in the range of from 0.35 to 0.80 nm. This diameter refers to the maximum pore

diameter. As is generally recognised, the pores in a molecular sieve are polygonal shaped channels having a minimum and a maximum pore diameter. For the purpose of the present invention the maximum pore diameter is the critical parameter, because it determines the size of the waxy molecules which can enter the pores.

Examples of aluminosilicate zeolites which are suitable to be used in the present invention are

ferrierite, ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM- 35, ZSM-38, ZSM-48, ZSM-57, SSZ-23, SSZ-24, SSZ-25, SSZ- 26, SSZ-32, SSZ-33 and MCM-22 and mixtures of two or more of these. Preferably, the zeolitic component is ZSM-5,

ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, or ZSM-48.

Preferably, the zeolitic component in the dewaxing catalyst is present in an amount in the range of from 10- 50 wt%, based on the total weight of the dewaxing

catalyst.

Preferred aluminosilicate zeolites are of the MFI- topology for example ZSM-5.

Preferably, small crystallites are used in order to achieve an optimum catalytic activity. Preferably, crystallites smaller than 10 micron, and more preferably smaller than 1 micron are used. The practical lower limit is suitably 0.1 micron. The dewaxing catalyst also comprises a low acidity refractory oxide binder material which is essentially free of alumina. Examples are low acidity refractory oxides such as silica, zirconia, titanium dioxide, germanium dioxide, boria and mixtures of two or more of these. The most preferred binder is silica. The weight ratio of modified molecular sieve to binder is suitably within the range of from 05/95 to 95/05.

The dealumination of the aluminosilicate zeolite results in a reduction of the number of alumina moieties present in the zeolite and hence in a reduction of the mole percentage of alumina. The expression "alumina moiety" as used in this connection refers to an

A^C^-unit which is part of the framework of the alumino- silicate zeolite, i.e. which has been incorporated via covalent bindings with other oxide moieties, such as silica (S1O2), in the framework of the aluminosilicate zeolite. The mole percentage of alumina present in the aluminosilicate zeolite is defined as the percentage of moles AI2O3 relative to the total number of moles of oxides constituting the aluminosilicate zeolite (prior to dealumination) or modified molecular sieve (after

dealumination) .

Preferably, the surface of the zeolite crystallites is selectively dealuminated . A selective surface

dealumination results in a reduction of the number of surface acid sites of the zeolite crystallites, whilst not affecting the internal structure of the zeolite crystallites .

Dealumination can be attained by methods known in the art. Particularly useful methods are those, wherein the dealumination selectively occurs, or anyhow is claimed to occur selectively, at the surface of the crystallites of - li the molecular sieve. Examples of dealumination processes are described in the afore mentioned WO-A-9641849.

Preferably, dealumination is performed by a process in which the zeolite is contacted with an aqueous

solution of a fluorosilicate salt wherein the

fluorosilicate salt is represented by the formula:

(A)₂/bSiF₆

wherein ^λΑ' is a metallic or non-metallic cation other than H+ having the valence ^xb' . This treatment will be also referred to as the AHS treatment. Examples of cations ^xb' are alkylammonium, NH4⁺, Mg⁺⁺, Li⁺, Na⁺, K⁺, Ba⁺⁺, Cd⁺⁺, Cu+, Ca⁺⁺, Cs+, Fe⁺⁺, Co⁺⁺, Pb⁺⁺, Mn⁺⁺, Rb+, Ag⁺, Sr⁺⁺, Tl⁺, and Zn⁺⁺. Preferably ^λΑ' is the ammonium cation. The zeolite material may be contacted with the fluorosilicate salt at a pH of suitably between 3 and 7.

Such a dealumination process is for example described in US-A-5157191. The dealumination treatment is referred to as the AHS-treatment .

The dewaxing catalyst to be used in accordance with the present invention is preferably prepared by first extruding the aluminosilicate zeolite with the binder and subsequently subjecting the extrudate to a dealumination treatment, preferably the AHS treatment as described above. It has been found that an increased mechanical strenght of the catalyst extrudate is obtained when prepared according to this sequence of steps.

The Group VIII metal of the Periodic Table is

suitably added to the catalyst extrudate comprising the dealuminated aluminosilicate zeolite crystallites by known techniques, such as ion-exchange techniques.

Typical ion-exchange techniques call for contacting the selected zeolite with a salt of the desired replacing cation. Although a wide variety of salts can be employed, particular preference is given to chloride, nitrates and sulphates. Representative ion-exchange techniques are disclosed in a wide variety of patents including

US-A-3140249, US-A-3140251 and US-A-3140253.

In step (d) use is made of dewaxing catalyst which comprises a Group VIII metal hydrogenation component. Group VIII metal components include those components based on both noble and non-noble metals. Particularly suitable Group VIII metal components, accordingly, are palladium, platinum, nickel and/or cobalt in sulphidic, oxidic and/or elemental form. The total amount Group VIII metal of the Periodic Table will suitably not exceed 10% by weight calculated as element and based on total weight of support, and preferably is in the range of from 0.1 to 5.0% by weight, more preferably from 0.2 to 3.0% by weight. If both platinum and palladium are present, the weight ratio of platinum to palladium may vary within wide limits, but suitably is in the range of from 0.05 to 10, more suitably 0.1 to 5. Catalysts comprising

palladium, platinum and nickel as the hydrogenation component are preferred. The Group VIII metal

hydrogenation component is preferably platinum or

palladium, more preferably platinum.

The catalytic dewaxing conditions in step (d) of the process according to the invention are typical catalytic dewaxing conditions. Therefore, the temperature is suitably in the range of from 300-400 °C, preferably in the range of from 320-390 °C, and more preferably in the range of from 330-380 °C. Suitable dewaxing pressures are in the range of from 80-240 bara. Preferably, the

dewaxing pressure is in the range of from 100-180 bara, more preferably in the range of from 120-170 bara. The weight hourly space velocity in step (d) is suitably in the range of from 0.4 to 7 hr^-1, preferably in the range of from 0.5 to 2.5 hr^-1, and more preferably in the range of from 0.65 to 2.25 hr^-1.

Step (d) is carried out in the presence of hydrogen. Hydrogen is suitably supplied to the second reaction zone at a rate of 350 to 1500 Nl/kg feed.

The dewaxed product as obtained in step (d) has a viscosity index (VI) which enables the production of high VI lubricating base oils. The dewaxed product as obtained in step (d) suitably contains sulphur in an amount of less than 350 ppmw, preferably less than 300 ppmw, and it contains nitrogen in an amount of less than 80 ppmw, preferably less than 60 ppmw. The dewaxed product has suitably a viscosity at 100 °C in the range of 10 to 17 cSt, preferably in the range of from 10 to 15 cSt.

In step (e) , at least part of the dewaxed product as obtained in step (d) is hydrofinished with a

hydrofinishing catalyst in the presence of a hydrogen- containing gas under hydrofinishing conditions to obtain a heavy base oil.

Preferably, the entire dewaxed product as obtained in step (d) is subjected to step (e) .

Hydrofinishing is known in the art and examples of suitable hydrofinishing steps are disclosed in, for instance, US-A-5139647, WO-A-9201657 and WO-A-9201769.

Generally, hydrofinishing comprises contacting a

hydrocarbon feed, in this case a feed comprising the dewaxed lubricating base oil, with a hydrogenation catalyst under relatively mild conditions in order to saturate at least part of the aromatics still present in the dewaxed base oil. Suitable catalysts are those normally applied for this purpose with noble metal-based catalysts, such as those comprising Pt and/or Pd supported on an amorphous silica-alumina carrier. In an alternative embodiment of the present invention, in the hydrotreating steps in step (b) use is made of a non- noble metal hydrofinishing catalyst, a so-called base metal hydrofinishing catalyst such as nickel-molybdenum on an alumina support.

Hydrofinishing conditions as per invention involve operating temperatures up to 390 °C and preferably in the range of from 300 to 380 °C, more preferably 330 to

370 °C, operating pressures in the range of from 80 to

200 bara, preferably in the range of from 100 to 170 bara, and weight hourly space velocities in the range of from 0.3-2.5 hr^-1, preferably in the range of from 0.5 - 1.5 hr^"1.

The yield of the heavy base oil in step (e) is high when compared to known processes for preparing base oils wherein use is made of hydrocracking and catalytically dewaxing steps. This high yield of heavy base oils can be expressed as the ratio of heavy base oil over light base oil as obtained in step (e) . The high yield of heavy base oil can for instance be expressed as the ratio of 500N base oil over 150N base oil as obtained in step (e) . The 500 N base oil is a heavy Group II base oil having typically a viscosity at 100 °C in the range of from 10.0-12.9 cSt, whereas the 150N base oil is a light Group

II base oil having typically a viscosity at 100 °C in the range of from 4.8-6.8 cSt. Suitably, the ratio of 500N base oil over 150N base oil as obtained in step (e) is at least 1.0, preferably at least 1.5, more preferably at least 2.5, and most preferably at least 3.0.

This high yield of heavy base oil is established by the particular sequence of process steps (a) - (e) and use of particular catalysts and/or catalyst combinations and constitutes a major improvement over known processes to prepare base oils, especially in view of today's

increasing demand for heavy base oils.

In step (f) the heavy base oil is recovered. The heavy base oil as obtained in step (e) can for instance be separated from the other components of the effluent from the hydrofinishing process, including light base oils, by means of conventional methods, such as by distillation under atmospheric or reduced pressure. Of these, distillation under reduced pressure, including vacuum flashing and vacuum distillation, is most suitably applied. The cut point (s) of the distillate fraction (s) is/are selected such that each product distillate

recovered has the desired heavy base oils properties for its envisaged application.

The heavy base oil as recovered in step (f) suitably contains sulphur in an amount of less than 300 ppmw, preferably less than 200 ppmw, and it contains nitrogen in an amount of less than 80 ppmw, preferably less than 50 ppmw. The heavy base oil has suitably a viscosity at

100 °C in the range of 10-15 cSt, preferably in the range of from 10-13 cSt.

The invention will be illustrated by the following non-limiting Examples.

A Basrah Light waxy distillate feedstock is provided in a step (a) . Table 1: Main characteristics of the feedstock

70% °C 532

80% °C 548

90% °C 573

94% °C 592

96% °C 611

98% °C >620

Laboratory Solvent Dewaxing at °C -20

Wax content % 9.2

Filter Oil

Kinematic Viscosities

At 40 °C cSt 272.22

At 100 °C cSt 17.16

Viscosity Index 53.6

Sulphur Content % 2.93

Basic Nitrogen Content ppm 414

Aromatics (UV method)

Mono mmo1/ 100g 47.8

Di mmo1/ 100g 9.3

Poly mmo1/ 100g 47.1

In a step (b) the feedstock is hydrotreated.

Example 1 (according to the invention)

The feedstock as described in Table 1 is hydrotreated over a conventional NiMo on alumina hydrotreating catalyst (for this example C-424 from Criterion catalyst portfolio) aiming at producing a hydrotreated effluent (370 °C+ fraction) containing ca. 50 ppm nitrogen and ca. 300 ppm sulphur.

The operating conditions and main outcome of the hydroprocessing step are indicated in Table 2.

Table 2 : Production of a hydrotreated effluent in step

(b) of the present invention

Processing Conditions unit S & N effluent as per step (b) invention

Inlet pressure bar a 149

Reactor temperature, WABT °C 385

WHSV T/m³.h^_1 1.0

Recycle gas rate Nl/kg 1604

Yield Structure

C₁-C4 % of 0.21

NH₃ % of 0.15

H₂S % of 2.82

H₂0 % of 0.34

Total Liquid Product % of 97.55

370 °C+ % of 85.79

Hydrogen consumption % of 1.06

Product Analysis

Nitrogen ppmw 50

Sulphur ppmw 275

S/N 6

kioo cSt 10.41 Viscosity Index 101

Pour Point °C +48

370 °C+ Distillation ASTM D2887

IBP °C 374

5% °C 401

10% °C 419

30% °C 462

50% °C 495

70% °C 526

90% °C 572

95% °C 595

FBP °C 648

460 °C+ content % 71

Example 2 (comparative Example)

The same feedstock (Table 1) is hydrotreated in a conventional manner to significantly lower nitrogen and sulphur levels, < 5 ppmw and < 50 ppmw, respectively, to match the typical requirements for second stage noble metal isomerization-dewaxing and hydrofinishing catalysts as per current practice. For this a high activity

iMo/Al20₃ -type-II hydrotreating catalyst (like for example DN-3100 from Criterion catalyst portfolio) is needed. The operating conditions and main outcome of the hydroprocessing step are indicated in Table 3.

Table 3: Production of a hydrotreated effluent in a

conventional manner

Processing Conditions of a unit S & N effluent as conventional step (b) per current practice

Inlet pressure bar a 149

Reactor temperature, WABT °C 389

WHSV T/m³.h^_1 1.0

Recycle gas rate Nl/kg 1580

Yield Structure

C1-C4 % of 0.68

NH₃ % of 0.15

H₂S % of 2.84

H₂0 % of 0.34

Total Liquid Product % of 97.71

370 °C+ % of 70.70

Hydrogen consumption % of 1.88

Product Analysis

Nitrogen ppmw 2

Sulphur ppmw 55

S/N 25 Vkioo cSt 8.30

Viscosity Index 115

Pour Point °C +44

370 °C+ Distillation ASTM D2887

IBP °C 372

5% °C 388

10% °C 404

30% °C 447

50% °C 482

70% °C 515

90% °C 561

95% °C 586

FBP °C 643

460 °C+ content %w 63

Summary Table Step (b)

Step (b) Effluent - Example 1 Effluent - Example 2

Catalyst NiMo/Al₂0₃ High activity conventional NiMo/Al₂0₃

Nitrogen, ppm 50 2

Sulphur, ppmw 275 55

370 °C+ yield, %wof 85.8 70.7

460 °C+, % 71 63

Vkioo , cSt 10.41 8.30

Viscosity Index 101 115

Pour Point, °C +48 +44 In a step (c) , ¾S and N¾ contaminants and light products are stripped from the effluents as obtained in Examples 1 and 2. Subsequently, in a step (d) the

products obtained in step (c) are subjected to a dewaxing step in accordance with the present invention and a conventional dewaxing step.

Example 3 (according to the invention)

The 370 °C+ fraction of Example 1 is catalytically dewaxed on Shell commercial dewaxing catalyst SLD-800, a base metal (Ni) catalyst specifically developed for the dewaxing of severely contaminated feedstocks.

The operating conditions and main outcome of the catalytic dewaxing step are indicated in Table 4.

Table 4: Production of a catalytically dewaxed product as per

invention

370 °C+ Distillation ASTM D2887

IBP °C 370

5% °C 406

10% °C 423

30% °C 464

50% °C 491

70% °C 524

90% °c 570

95% °c 600

FBP °c 647

Heavy (12 cSt) / Light % 70 / 13=5.38 base oil (5 cSt)

Example 4 (comparative Example)

The 370 °C+ fraction of Example 2 is catalytically dewaxed on Shell commercial dewaxing catalyst SLD-821, a noble metal (Pt) catalyst specifically developed for the dewaxing of deeply hydrotreated feedstocks for base oil

II and III production.

The operating conditions and main outcome of the catalytic dewaxing step are indicated in Table 5.

Table 5: Production of a catalytically dewaxed product in a

conventional manner

50% °C 485

70% °C 517

90% °C 464

95% °C 590

FBP °C 642

Heavy (12 cSt) / Light % 55 / 32=1.71 base oil (5.5 cSt)

Summary Table Step (d)

Step (d) Example 3 Example 4

Catalyst SLD-800 SLD-821

370 °C+ yield, % of 83.3 87.0

(step 2)

370 °C+ yield, %wof 71.5 61.5

(steps 1+ 2)

Vkioo , cSt 10.30 8.81

Viscosity Index 91 106

Pour Point, °C -12 -12

In a step (e) , the dewaxed product as obtained in step (d) according to the present invention is

hydrofinished .

Example 5 (according to the invention)

The 370 °C+ fraction of Example 3, stripped from any gases, is submitted to a hydrofinishing step using either a base metal hydrofinishing catalyst (high active

NiMo/Al₂C>3-type catalysts) ; Example 5a, or a noble metal hydrofinishing catalyst (like Criterion LN-5) ; Example 5b, known for its high hydrogenation power and resistance to sulphur and nitrogen poisoning.

The operating conditions and main outcome of the hydrofinishing steps (e) are indicated in Table 6. Table 6: Production of a hydrofinished product in accordance

with step (e) of the invention

95% °C 596 596

FBP °C 640 639

Heavy (12 cSt) / Light % 61/19=3.21 64/19=3.37 base oil (5 cSt)

Example 6 (comparative Example)

The 370 °C+ fraction of counter Example 4, stripped from any gases, is submitted to a hydrofinishing step ( using noble metal hydrofinishing catalyst (LN-5) from Criterion .

The operating conditions and main outcome of the hydrofinishing step (e) are indicated in Table 7.

Table 7: Production of a hydrofinished product in a

conventional manner

30% °C 454

50% °C 485

70% °c 517

90% °c 464

95% °c 590

FBP °c 641

Heavy (12 cSt) / Light % 55 / 32=1.71 base oil (5 cSt)

In view of the above, it will be clear that the process of the present invention constitutes an

improvement over a conventional process for preparing heavy base oil.

Claims

C L A I M S

1. Process for preparing a heavy base oil comprising the steps of:

(a) providing a hydrocarbonaceous feedstock which contains at least 50% by weight of hydrocarbons boiling above 460 °C, nitrogen in amount in the range of from

800-2500 ppmw, and sulphur in an amount in the range of from 1.5-4.0 %wt;

(b) hydrotreating the hydrocarbonaceous feedstock with a hydrotreating catalyst in the presence of a hydrogen- containing gas under hydrotreating conditions to obtain a hydrotreated product which contains nitrogen in an amount in the range of from 30-80 ppmw and sulphur in an amount in the range of from 200-450 ppmw;

(c) removing at least 50% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step

(b) ;

(d) catalytically dewaxing at least part of the

hydrofinishing conditions to obtain a heavy base oil; and (f) recovering the heavy base oil.

2. Process according to claim 1, wherein the hydrocarbonaceous feedstock as provided in step (a) contains more than 65% by weight of hydrocarbons boiling above 460 °C.

3. Process according to claim 1 or 2, wherein the hydrocarbonaceous feedstock as provided in step (a) contains at least 50% by weight of hydrocarbons having a viscosity at 100 °C of above 14 cSt.

4. Process according to any one of claims 1-3, wherein the ratio of the amount of nitrogen and the amount of sulphur (N/S) in the hydrotreated product as obtained in step (b) is in the range of from 0.1-0.3.

5. Process according to any one of claims 1-4, wherein in step (c) N¾ and ¾S are removed from the hydrotreated product as obtained in step (b) by means of stripping.

6. Process according to any one of claims 1-5, wherein in step (c) at least 90% of the N¾ and ¾S which is present in the hydrotreated product as obtained in step (b) is removed.

7. Process according to any one of claims 1-6, wherein the zeolitic component in the dewaxing catalyst in step

(d) is present in an amount in the range of from 10 to 50 wt%, based on the total weight of the dewaxing catalyst.

8. Process according to claim 7, wherein the zeolitic component is ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM- 35, or ZSM-48

9. Process according to any one of claims 1-8, in which the hydrotreating conditions in steps (b) comprise a temperature in the range of from 250-480 °C, a pressure in the range of from 30-250 bar, and a weight hourly space velocity in the range of from 0.2-10 hr^-1; the dewaxing conditions in steps (d) comprise a temperature in the range of from 350-460 °C, a pressure in the range of from 80-240 bar, and a weight hourly space velocity in the range of from 0.4-7 hr^-1; and the hydrofinishing conditions in steps (e) comprise a temperature in the range of from 300 - 390 °C, a pressure in the range of from 80 to-200 bar, and a weight hourly space velocity in the range of from 0.5-2.5 hr^-1.

10. Process according to any one of claims 1-9, wherein the hydrofinishing catalyst in step (e) is a noble metal- based hydrofinishing catalyst.

11. Process according to any one of claims 1-9, wherein the hydrofinishing catalyst in step (e) is a base metal hydrofinishing catalyst.

12. Process according to any one of claims 1-11, wherein in step (c) also hydrocarbons boiling below 370 °C are separated from the hydrotreated product as obtained in step (b) .

13. Process according to any one of claims 1-12, wherein the entire hydrotreated product as obtained in step (b) is subjected to step (c) .

14. Process according to any one of claims 1-13, wherein the entire hydrotreated product as obtained in step (c) is subjected to step (d) .

15. Process according to any one of claims 1-14, wherein the entire dewaxed product as obtained in step (d) is subjected to step (e) .