Process for preparing Fischer-Tropsch derived middle distillates and base oils

Abstract

The present invention provides a method for preparing middle distillates and base oil from Fischer-Tropsch products, the method comprising: (a) preparing a molten-liquid ... 2 / AlO 3 (a) separating the mixture obtained in step (a) into one or more middle distillate fractions, a first residual fraction and a naphtha fraction by atmospheric distillation; and (c) separating the first residual fraction into at least a distillate base oil fraction and a second residual fraction by vacuum distillation.

Description

Technical Field

[0001] The present invention relates to a process for preparing middle distillates and one or more base oils from Fischer-Tropsch products, and also to gas oils and base oils obtained by said process. Background Art

[0002] It is known in the art to prepare one or more middle distillate fractions, such as, for example, kerosene or gas oil and base oil precursors or base oils, from Fischer-Tropsch derived feedstocks having good cold flow properties. For example, in WO2015 / 063213 a process is disclosed in which one or more middle distillate fractions and a first residual fraction are obtained by using two different catalysts in series in the hydrotreatment of a Fischer-Tropsch derived feedstock, wherein both catalysts have hydrocracking and hydroisomerization activity and the second catalyst is more active in hydroisomerization and less active in hydrocracking than the first catalyst. The stacked bed in WO2015 / 063213 allows the preparation of lubricating base oils and one or more middle distillate fractions having improved cold flow properties.

[0003] A problem with the process disclosed in WO2015 / 063213 is that, although the process allows for improved cold flow properties of middle distillates, it requires high single pass conversions to obtain sufficiently low cold flow properties, resulting in a loss in yield of valuable distillate base oil fractions.

[0004] For example, in WO02 / 070627 a process is disclosed in which two or more lubricating base oil grades and gas oil are obtained by subjecting a Fischer-Tropsch synthesis product to a hydroconversion catalyst, and the obtained products need to be subjected to further treatment steps to obtain dewaxed base oil and gas oil.

[0005] The problem with the process disclosed in WO02 / 070627 is that, although the process provides middle distillates and base oils, high quality middle distillates are not produced. In addition, the isomerization of the distillate base oil fraction in the process disclosed in WO02 / 070627 is low and it requires further dewaxing to make the final base oil product meet its specific specifications. Summary of the invention

[0006] It is an object of the present invention to solve or minimize at least one of the above problems.

[0007] Another object of the present invention is to produce high quality middle distillates.

[0008] Another object of the present invention is to produce a distillate base oil fraction which is sufficiently dewaxed to allow direct distillation into base oils and meet their specifications.

[0009] Furthermore, it is an object of the present invention to produce a vacuum tower bottoms product which is suitable as an extra heavy base oil from a viscosity and pour point point point of view without the need for additional catalytic dewaxing.

[0010] According to the present invention, one of the above or other objects can be achieved by providing a method for preparing middle distillates and base oil from Fischer-Tropsch products, the method comprising:

[0011] (a) subjecting the Fischer-Tropsch product to a hydrotreatment step in the presence of a catalyst comprising a molecular sieve having a pore size of between 5 and 7 angstroms and a SiO2 / Al2O3 ratio of at least 25, preferably from 50 to 180, and a Group VIII metal, to obtain a mixture comprising one or more middle distillate fractions and a first residual fraction and a naphtha fraction;

[0012] (b) separating the mixture obtained in step (a) into one or more middle distillate fractions, a first residual fraction and a naphtha fraction using atmospheric distillation;

[0013] (c) separating the first residual fraction into at least a distillate base oil fraction and a second residual fraction using vacuum distillation.

[0014] It has now surprisingly been found that, according to the present invention, by using a catalyst comprising a molecular sieve having a pore size between 5 and 7 angstroms and a SiO2 / Al2O3 ratio of at least 25, preferably 50 to 180 and a Group VIII metal in a hydroconversion step of a Fischer-Tropsch derived feedstock, a gas oil fraction having improved cold flow properties can be prepared with an improved distillate base oil yield. Using the catalyst according to the present invention, a distillate base oil fraction having a low pour point and a high viscosity index and a second residual fraction can be obtained in a single hydrocracking step without the need for a separate catalytic dewaxing step. In this way, high viscosity base oils can be produced at sufficiently low pour points for use in, for example, process oils and finished lubricants without the need for additional dewaxing (less CAPEX, no additional yield loss).

[0015] An important advantage of the present invention is that a high quality middle distillate is obtained, which means a kerosene that complies with Jet-A1 from a freezing point point of view and a gas oil that can be applied as a blending component or as a neat grade in Nordic or even Arctic grade diesel mainly from a cloud point of view.

[0016] Another advantage of the present invention is that a distillate base oil fraction can be produced which is sufficiently dewaxed to allow direct distillation into one or more base oils meeting its specific specifications. Thus, the present invention allows arrangements where a catalytic dewaxing unit (CDW) can be omitted.

[0017] Another advantage is that the present invention produces a vacuum bottoms product (= second residual fraction) which is suitable as extra heavy base oil (XHBO) from the pour point and viscosity point of view without the need for additional catalytic dewaxing (X-CDW).

[0018] An advantage of the catalyst used according to the invention is that the catalyst preferentially converts heavier molecules. This results in a high yield of highly isomerized distillate base oil fractions and thus a high yield of distillate base oil. It also provides a high degree of isomerization in the residual base oil fraction. The high degree of isomerization of the middle distillate fraction allows operating at a reduced per-pass conversion, which even further increases the distillate base oil fraction yield. DETAILED DESCRIPTION

[0019] In step (a) of the process according to the present invention, the Fischer-Tropsch product is subjected to a hydrotreatment step in the presence of a catalyst comprising a molecular sieve having a pore size of between 5 and 7 angstroms and a SiO2 / Al2O3 ratio of at least 25, preferably from 50 to 180, and a Group VIII metal, so as to obtain a mixture comprising one or more middle distillate fractions, a first residual fraction and a naphtha fraction.

[0020] Fischer-Tropsch product streams are known in the art. The term "Fischer-Tropsch product" refers to the synthetic product of the Fischer-Tropsch process. In the Fischer-Tropsch process, synthesis gas is converted into synthetic products. Synthesis gas (Synthesis gas or syngas) is a mixture of hydrogen and carbon monoxide obtained by the conversion of hydrocarbon feedstocks. Suitable feedstocks include natural gas, crude oil, heavy oil fractions, coal, biomass and lignite. Fischer-Tropsch products derived from hydrocarbon feedstocks that are typically gaseous may also be referred to as GTL (gas to liquid) products. The preparation of Fischer-Tropsch products has been described, for example, in WO2003 / 070857.

[0021] The product stream of the Fischer-Tropsch process is typically separated into a water stream, a stream comprising unconverted synthesis gas, carbon dioxide, inert gases and C1 to C3 gases, and a C4+ stream.

[0022] The full Fischer-Tropsch hydrocarbon product suitably comprises a C1 to C300 fraction.

[0023] A lighter fraction of the Fischer-Tropsch product, suitably comprising a C3 to C9 fraction, is separated from the Fischer-Tropsch product by distillation to obtain a Fischer-Tropsch product stream, suitably comprising a C10 to C300 fraction.

[0024] The weight ratio of compounds having at least 60 or more carbon atoms to compounds having at least 30 carbon atoms in the Fischer-Tropsch product is preferably at least 0.2, more preferably 0.3.

[0025] The Fischer-Tropsch product used in the present invention is a paraffinic feedstock which comprises at least 50% by weight of compounds having a boiling point above 370°C and which has a paraffin content of at least 60% by weight, an aromatic content of less than 1% by weight, a cycloparaffin content of less than 2% by weight, a nitrogen content of less than 0.1% by weight and a sulphur content of less than 0.1% by weight.

[0026] The hydrotreatment in step (a) can be carried out in a heavy paraffin conversion unit. In this unit, both hydrocracking and hydroisomerization are carried out in the presence of the catalyst of step (a). In step (a), the product stream is contacted in the presence of hydrogen at a pressure of 20 to 100 bar and a temperature between 250° C. and 400° C. Preferably, step (a) is carried out at a pressure range of 30 to 70 bar and a temperature between 300° C. and 400° C.

[0027] Hydrocracking / hydroisomerization methods are known in the art and are therefore not described in detail herein. Hydrocracking / hydroisomerization and the effect of hydrocracking / hydroisomerization conditions on the amount of isomerized products are described, for example, in Chapter 6 of "Hydrocracking Science and Technology", Julius Scherzer; AJ Cruia, Marcel Dekker, Inc, New York, 1996, ISBN 0-8247-9760-4.

[0028] Step (a) is carried out in the presence of a catalyst comprising a molecular sieve having a pore size between 5 and 7 angstroms and a SiO2 / Al2O3 ratio of at least 25, preferably 50 to 180, and a Group VIII metal.

[0029] Suitably, the catalyst used in step (a) of the process according to the invention comprises a molecular sieve having a pore size of between 5 Angstroms and 6.6 Angstroms.

[0030] Preferably, the dewaxing catalyst is a heterogeneous catalyst comprising a molecular sieve, more suitably a 10-membered or 12-membered ring molecular sieve having a pore size between 5 angstroms and 6.6 angstroms, preferably a unidimensional 10-membered or 12-membered ring molecular sieve having a pore size between 5 angstroms and 6.6 angstroms, more preferably a unidimensional 10-membered or 12-membered ring molecular sieve having a pore size between 5 angstroms and 6.2 angstroms, and a metal having a hydrogenation function, such as a Group VIII metal. The pore size indicated relates to the maximum diameter of the pores, as described in the 6th revised edition of the Atlas of Zeolite Framework Types published in 2007 in the name of the Structure Commission of the International Zeolite Association.

[0031] Preferably, the hydrocracking in step (a) is carried out in the presence of a catalyst comprising a molecular sieve and a Group VIII metal, wherein the molecular sieve is selected from the group consisting of MTW, MTT, TON type molecular sieves, ZSM-48 and EU-2.

[0032] 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 referred to as the *MRE family and described in the disordered catalog of zeolite frameworks published in 2000 under the name of the International Zeolite Association Structure Committee) can be used. Even though EU-2 is considered 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 to be members of zeolites whose structures belong to the ZSM-48 family. In this application, any reference to ZSM-48 zeolite is also a reference to ZBM-30 and EU-11 zeolites.

[0033] In addition to ZSM-48 and / or EU-2 zeolites, other zeolites may be present in the catalyst composition, in particular when it is desired to modify its catalytic properties. It has been found to be advantageous to have the present zeolite ZSM-12, which has been defined in the Zeolite Structure Database published in 2007 / 2008 on behalf of the International Zeolite Association Structure Committee.

[0034] Suitable Group VIII metals are nickel, cobalt, platinum and palladium. Preferably, the Group VIII metal is platinum or palladium.

[0035] Preferably, the catalyst used in step (a) comprises a molecular sieve, platinum or palladium as Group VIII metal and a silica or titania binder, wherein the molecular sieve is a MTW, MTT, TON type molecular sieve or ZSM-48 or EU-2.

[0036] Suitably, the catalyst used in step (a) is a catalytic dewaxing catalyst.

[0037] The dewaxing catalyst suitably also comprises a binder. The binder may be non-acidic. Examples of suitable binders are clay, silica, titania, zirconium oxide, aluminum oxide, mixtures and combinations of the above and other binders known to those skilled in the art.

[0038] Preferably, the catalyst comprises a silica or titania binder.

[0039] The preparation of the dewaxing catalyst used in step (a) is described, for example, in WO 2015 / 063213.

[0040] The mixture obtained in step (a) is preferably an at least partially isomerized feedstock. When operating at comparable single-pass conversions, the catalyst used in step (a) according to the invention results in a higher degree of isomerization of the mixture obtained in step (a) than when using a catalyst system as described in WO2015 / 063213 and WO02 / 070627. This higher degree of isomerization results in a lower cloud point of the resulting middle distillate and a lower pour point of the base oil and residual base oil.

[0041] In step (b) of the process according to the invention, the mixture obtained in step (a) is separated by atmospheric distillation into one or more middle distillate fractions, a first residual fraction and a naphtha fraction.

[0042] Preferably, the middle distillate fraction(s) obtained in step (b) has a cloud point according to ASTM D2500 between -10°C and -50°C, more preferably between -15°C and -35°C.

[0043] The one or more middle distillate fractions may comprise a single middle distillate fraction, for example a single fraction having a majority of components (e.g. 95% by volume or more) with a boiling point in the range of 150°C to 400°C. The single fraction is preferably a wide range gas oil. Preferably, at least a gas oil fraction is obtained in step (b). The gas oil fraction will typically contain a majority of the components having a boiling point in the range of typical diesel fuel ("gas oil"), i.e. about 150°C to 400°C or 170°C to 370°C. According to ASTM D86, it will suitably have a 90% by volume distillation temperature of 300°C to 370°C. The gas oil fraction is typically a wide range heavy gas oil fraction. The cloud point of the gas oil fraction (wide range or heavy gas oil) is preferably below -10°C, preferably between -15°C and -35°C, and is therefore suitable for the production of Nordic and / or Arctic grade diesel and / or diesel blending components.

[0044] Optionally, the broad range gas oil may be distilled into a kerosene fraction and a heavy gas oil fraction.

[0045] The kerosene fraction obtained in step b) has a freezing point below -40° C. In this way, the kerosene fraction obtained in step b) of the process according to the invention has cold flow properties which make it suitable as a jet-A or even jet-A1 blending component.

[0046] The first residual fraction comprises compounds having a boiling point higher than the boiling point range of the middle distillate. Suitably, the first residual fraction is a fraction of which at least 95% by weight have a boiling point higher than 330°C. When operating at a comparable single-pass conversion, the first residual fraction obtained has a higher degree of isomerization than when obtained according to the methods described in WO2015 / 063213 and WO02 / 070627. This higher degree of isomerization is due to the use of a catalyst according to the present invention. In this way, a first residual fraction having a lower pour point is obtained.

[0047] In step (c) of the process of the present invention, the first residual fraction is separated into at least a distillate base oil fraction and a second residual fraction by vacuum distillation. The second residual fraction thus obtained generally comprises compounds having a boiling point above a temperature of 440° C. Preferably, the boiling point when 10% by weight of the second residual fraction from step (c) is recovered is in the range of between 440° C. and 560° C. according to ASTM D7169, more preferably the boiling point when 5% by weight is recovered is in the range of between 440° C. and 560° C. according to ASTM D7169.

[0048] Therefore, unlike the methods described in, for example, WO2015 / 063213 and WO02 / 070627, the second residual fraction obtained according to the present invention is suitable as an extra heavy base oil without the need for an additional catalytic dewaxing step. The second residual fraction is also referred to as a vacuum bottom product. The second residual fraction can undergo a subsequent dewaxing step to obtain an extra heavy base oil with a better pour point. The term extra heavy base oil refers to a residual base oil.

[0049] In one embodiment, the second residual fraction is a residual base oil.

[0050] In another embodiment, the second residual fraction is further dewaxed to obtain a residual base oil.

[0051] Suitably, the residual base oil has a pour point below -5°C, preferably in the range between -10°C and -40°C. Furthermore, the kinematic viscosity of the residual base oil at 100°C is in the range between 10 cSt and 35 cSt, preferably between 12 cSt and 30 cSt.

[0052] Optionally, the process according to the invention comprises a further step (d), wherein at least a part of the second residual fraction is recycled to step (a).

[0053] In case of recycling of the second residual fraction or another fraction obtained in the fractionation of the hydrotreated feedstock, references herein to the feedstock of step (a) are to the combined feedstock, ie the sum of the fresh feedstock and any recycled fractions.

[0054] The distillate base oil fraction obtained in step (c) will have an intermediate boiling range. Preferably, the boiling point when 90 wt% of the distillate base oil fraction from step (c) is recovered is within the range of 420°C and 560°C according to ASTM D2887.

[0055] Preferably, the process according to the present invention comprises a further step (e) wherein the distillate base oil fraction is fractionated into one or more base oils.

[0056] In one embodiment, the distillate base oil fraction may not be fully isomerized. The base oil fraction may be further dewaxed and fractionated into one or more base oils and optionally an isomerized gas oil fraction, preferably fractionated into base oils having a kinematic viscosity at 100°C in the range of 1.2 cst to 3 cst according to ASTM D445, and / or a base oil having a kinematic viscosity at 100°C in the range of 3 cst to 5 cst, and / or a base oil having a kinematic viscosity at 100°C in the range of 5 to 7, and / or a base oil having a kinematic viscosity at 100°C in the range of 7 cst to 9 cst according to ASTM D445.

[0057] In another embodiment, the distillate base oil fraction is fully isomerized and can be separated into one or more base oils and an optional isomerized gas oil fraction. The second distillate base oil fraction is preferably fractionated into one or more base oils. In yet another embodiment, the distillate base oil fraction is fully isomerized and separated into two or more base oils. The distillate base oil fraction is separated into various base oils having a kinematic viscosity in the range of 1.2 cst to 9 cst at 100°C.

[0058] Unlike the processes described in WO2015 / 063213 and WO02 / 070627, the distillate base oil fraction obtained in step c) of the process according to the invention has such a low pour point after step c) that the process according to the invention enables the production of base oils without the need for additional dewaxing (less CAPEX, no additional yield losses). Furthermore, the distillate base oil fraction and the derived base oils from step e) have a high viscosity index, higher than the distillate base oil fraction and the derived base oils obtained in the process as described in WO2015 / 063213, which makes the distillate base oil fraction very suitable for use in process oils and finished lubricants.

[0059] In another aspect, the present invention provides a Fischer-Tropsch derived arctic or severe winter climate grade gas oil according to paraffinic diesel fuel specification EN 15940, having a cloud point according to ASTM D2500 below -10°C, preferably between -10°C and -60°C. An arctic or severe winter climate range gas oil refers to a broad range or heavy gas oil obtained in step b) of the process according to the invention.

[0060] In another aspect, the present invention provides a Fischer-Tropsch derived distillate base oil according to the present invention, which has a pour point below -10 °C, preferably between -20 °C and -50 °C.

[0061] Preferably, the Fischer-Tropsch derived distillate base oil has a viscosity index between 100 and 150.

[0062] In another aspect, the present invention provides a Fischer-Tropsch derived residual base oil according to the present invention, which has a Vk100 higher than 10 mm2 / s and a pour point below -5 °C. The term ultra-heavy base oil refers to the Fischer-Tropsch derived residual base oil.

[0063] The following examples are given for certain aspects of some embodiments to facilitate a better understanding of the present invention. These examples should in no way be construed as limiting or defining the scope of the present invention.

[0064] Experiment A

[0065] The Fischer-Tropsch feed is obtained by fractionating the C5+ effluent from the Fischer-Tropsch process to obtain a heavy C14+ stream and an unused light <C14 stream for experimentation. The heavy C14+ stream contains 80% w with a boiling point above 370 °C and 47% w with a boiling point above 540 °C as determined by ASTM D-7169. The Fischer-Tropsch feed is continuously fed to the hydrocracking step in a once-through operating mode at 38 bar. The liquid product from the hydrocracking step is separated in a fractionator at a fractionation point between 320 °C and 370 °C into a distillate fraction and a first residue fraction. The boiling point distributions of the distillate and the first residue fraction are determined according to ASTM D-2887 and ASTM D-7169, respectively, while the n-alkane content is determined based on the GCxGC technique as described by Blomberg et al., J. High Resol. Chromatogr. 20 (1997) p. 539. The cloud points and pour points of the light and heavy products are determined according to ASTM D5773 and ASTM D5949.

[0066] Example 1

[0067] In the hydrocracking step, the feed is contacted with a silica-bonded ammonium hexafluorosilicate-treated Pt / ZSM-12 catalyst at a temperature between 320 °C and 335 °C. Other conditions are selected such that the 370 °C+ conversion is in the range of 35% to 75% w. The yields and n-alkane contents at 50% 370 °C+ conversion are calculated by interpolation and shown in Table 1. The cold flow properties of the product at 58% 370 °C+ conversion are shown in Table 2.

[0068] Example 2 (Comparative Example)

[0069] In the hydrocracking step, the feed is contacted with a catalyst comprising 0.8 wt% platinum on an amorphous silica-alumina support comprising 4 wt% beta zeolite and 66 wt% silica-alumina (29 wt% alumina content) and 30 wt% alumina binder at a temperature between 300°C and 310°C. Other conditions are selected so that the 370°C+ conversion is in the range of 35% to 75%w. The yield and normal paraffin content at 50% 370°C+ conversion are calculated by interpolation and are shown in Table 1. The cold flow properties of the product at 62% 370°C+ conversion are shown in Table 2.

[0070] Example 3

[0071] The first residual fraction from Example 1 obtained at 58% 370°C+ conversion was vacuum distilled in three fractions. The fraction kinematic viscosity at 100°C measured according to ASTM D7042, the fraction cloud point measured according to ASTM D2500 and the fraction pour point measured according to ASTM D97 are shown in Table 3.

[0072] Table 1: Yield distribution and n-paraffin content at 50% 370°C+ conversion

[0073] Example 1 Example 2 C1-C4 ％w 3.5 2.4 C5-150℃ ％w 10.6 11.2 150-370℃ ％w 45.3 46.0 370-540℃ ％w 28.7 27.0 >540℃ ％w 11.8 13.4 C10 to C22 normal paraffins ％w 8.2 23.6 C23 to C40 normal paraffins ％w 0.4 13.2

[0074] Table 2: Cold flow properties at 60% 370°C+ conversion

[0075]

[0076] Table 3: Product properties of the fractions obtained according to the invention

[0077] Fraction 1 Fraction 2 Fraction 3 Vk 100℃ cSt 2.2 3.6 12.9 Viscosity Index 114 130 148 Pour Point ℃ -42 -30 -39

[0078] discuss

[0079] The data presented show that similar yields are obtained with the catalyst according to the invention as with the catalyst in the comparative example (see Table 1). However, the n-paraffin content is much lower in both the middle distillate range (C10 to C22) and the heavier fractions for the catalyst according to the invention, which indicates a higher degree of isomerization (see Table 1). This is also visible in the lower cloud point and pour point of the light product fraction (see Table 2, fractions comprising the middle distillate fraction and naphtha) and the lower pour point of the heavy product fraction (see Table 2, first residual fraction). Using the catalyst according to the invention, base oil fractions with good cold flow properties and viscosity index can be obtained in a single hydrocracking process step without the need for a separate catalytic dewaxing step (see Table 3).

[0080] Experiment B

[0081] Experiments were carried out using a Fischer-Tropsch derived wax feed. The feed was a C5+ effluent from a Fischer-Tropsch process. About 76%w of the feed boiled above 370°C and about 53%w boiled above 540°C as determined using ASTM D7169.

[0082] The catalyst system is used to feed the feed continuously to the hydrocracking step at a WHSV based on 0.8t / m3 / h of fresh feed and a unit pressure of 60 bar. The ratio of hydrogen to oil is about 1250Nm3 / t fresh feed. The catalyst bed temperature is changed to set the desired conversion rate, and its range is 325°C to 345°C. The product passes through a high-pressure separator, and the recovered liquid product is subsequently separated in an atmospheric fractionator, which operates at an effective fractionation point of about 370°C. The distillate fraction is recovered from the top of the fractionator, while the first residual fraction is sent to a vacuum flasher operating at an effective fractionation point of about 540°C. The distillate base oil fraction is recovered from the top of the flasher, while the second residual fraction is recovered (once-through operation) or recycled back to the inlet of the hydrocracker (recycling operation). The gas produced is recovered from the high-pressure separator and the atmospheric tower and analyzed by online gas chromatography.

[0083] The boiling point distribution of the produced fractions was determined using ASTM D2887 or ASTM D7169. The normal paraffin content was determined by GCxGC technique as described in Blomberg et al., J. High Resol. Chromatogr. 20 (1997) p. 539. The pour point and cloud point of the fractions were determined using ASTM D97 and ASTM D2500. The freezing point was determined using ASTM D2386. Viscosity measurements were made using ASTM-D7042. Viscosity index was calculated according to ASTM D2270.

[0084] A portion of the produced distillate fraction was distilled off-line into naphtha and middle distillate product fractions using ASTM D2892. A portion of the distillate base oil fraction was vacuum distilled off-line into different base oil fractions using spin-belt distillation.

[0085] Example 4

[0086] In the hydrocracking step, the feed was contacted with a silica bound, ammonium hexafluorosilicate treated Pt / ZSM-12 catalyst in a once through mode of operation. The yields and product properties at 50% 370°C+ conversion were calculated by interpolation and are shown in Table 4. Using the same method, performance data were obtained at similar pour points for the distillate base oil fractions given in Table 5 and similar cloud points for the recovered distillate fractions given in Table 6.

[0087] Example 5 (Comparative Example)

[0088] The experiment of Example 4 was repeated using a stacked bed catalyst system. The system comprised a first catalyst and a second catalyst in an 80 / 20 ratio (v / v), with the first catalyst being above the second catalyst. The first catalyst comprised 0.8 wt % platinum on an amorphous silica-alumina support comprising 70 wt % silica-alumina (29 wt % alumina content) and 30 wt % alumina binder. The second catalyst was a silica-bound, ammonium hexafluorosilicate treated Pt / ZSM-12 catalyst as used in Example 4. The results are shown in Tables 4-6.

[0089] Experiment 6 (Comparative Example)

[0090] The experiment of Example 4 was repeated using a catalyst comprising 0.8 wt% platinum on an amorphous silica-alumina support comprising 70 wt% silica-alumina (29 wt% alumina content) and 30 wt% alumina binder. The results are shown in Tables 4-6.

[0091] Table 4 Comparison at similar conversion rate (50%)

[0092]

[0093]

[0094] nd = not determined

[0095] discuss

[0096] The data presented in Table 4 show that at similar conversions, higher distillate base oil fraction yields were obtained compared to the catalyst systems used in Comparative Examples 5 and 6, which translated into higher base oil yields.

[0097] A better cloud point of the distillate fraction as obtained in Example 4 according to the invention enables the production of high value middle distillate products for use in, for example, Arctic grade diesel.

[0098] The very low pour point (-41°) of the distillate base oil fraction that has been produced according to the invention (Example 4) enables the production of base oils without additional dewaxing (less CAPEX, no additional yield loss).

[0099] The second residual fraction obtained in Example 4 has a viscosity of about 25 cSt and a pour point of -17°C, indicating that high viscosities at sufficiently low pour points can be produced according to the present invention without the need for an additional catalytic dewaxing step. These base oils are suitable for use in process oils and finished lubricants.

[0100] Table 5 Comparison of 370℃ to 540℃ fractions (distillate base oil fractions) at similar pour points (-36℃)

[0101]

[0102]

[0103] a It is not possible to achieve this with the catalyst system of Example 6

[0104] discuss

[0105] The data presented in Table 5 show that at similar pour points of the distillate base oil fractions, a much higher distillate base oil yield was obtained compared to the catalyst system used in Comparative Example 5, which translates into a higher base oil yield.

[0106] The very low pour point (-36°) of the distillate base oil fraction that has been produced according to the invention (Example 4) enables the production of base oils without additional dewaxing (less CAPEX, no additional yield loss).

[0107] The higher viscosity index of the distillate base oil fractions compared to the viscosity index obtained in Example 5 brings additional value to the base oils obtained according to the present invention (Example 4). The second residual fraction obtained in Example 4 has a viscosity of about 25 cSt and a pour point of -10°C, indicating that high viscosity base oils at sufficiently low pour points can be produced according to the present invention without the need for an additional catalytic dewaxing step. These base oils are suitable for application in process oils and finished lubricants. Although the purpose of these examples is to prepare base oils, Example 4 also results in the production of distillate fractions with very low cloud points.

[0108] Table 6 Comparison of <370 fractions (distillate fractions) at similar cloud points (-30°C)

[0109]

[0110]

[0111] a It is not possible to achieve this with the catalyst system of Example 6

[0112] discuss

[0113] The data presented in Table 6 show that at similar cloud points of the distillate fractions, much higher distillate base oil fraction yields are obtained compared to the catalyst system used in Comparative Example 5 because it allows operation at lower single pass conversions, which translates into higher base oil yields.

[0114] The very low cloud point of -30°C of the distillate fraction obtained in Example 4 according to the invention enables the production of Nordic and / or Arctic grade diesel and / or diesel blending components, which brings additional value.

[0115] The very low pour point of the distillate base oil fraction that has been produced according to the invention (Example 4) enables the production of base oils without additional dewaxing (less CAPEX, no additional yield loss).

Claims

1. A method for preparing middle distillates and base oils from Fischer-Tropsch products, the method comprising: (a) subjecting the Fischer-Tropsch product to a hydrotreating step in the presence of a catalyst comprising a molecular sieve having a pore size of between 5 angstroms and 7 angstroms and a SiO2 / Al2O3 ratio of at least 25 and a Group VIII metal to obtain a mixture comprising one or more middle distillate fractions and a first residual fraction and a naphtha fraction, wherein the hydrotreating step is carried out without a separate dewaxing step; wherein the Fischer-Tropsch product is a paraffinic feedstock comprising at least 50% by weight of compounds having a boiling point above 370°C and having a paraffin content of at least 60% by weight, an aromatic content of less than 1% by weight, a cycloparaffin content of less than 2% by weight, a nitrogen content of less than 0.1% by weight and a sulfur content of less than 0.1% by weight; (b) separating the mixture obtained in step (a) into one or more middle distillate fractions, a first residual fraction and a naphtha fraction using atmospheric distillation; (c) separating the first residual fraction into at least a distillate base oil fraction and a second residual fraction using vacuum distillation.

2. The process according to claim 1, wherein the catalyst used in step (a) comprises a molecular sieve, platinum or palladium as a Group VIII metal and a silica or titania binder, and wherein the molecular sieve is a MTW, MTT, TON type molecular sieve or ZSM-48 or EU-2.

3. The method according to claim 1 or 2, wherein the molecular sieve has a SiO2 / Al2O3 ratio of 50 to 180.

4. The process according to claim 1 or 2, wherein the catalyst used in step (a) is a hydrocracking catalyst.

5. The process according to claim 1 or 2, wherein the one or more middle distillate fractions obtained in step (b) are at least a gas oil fraction.

6. The process according to claim 1 or 2, wherein the boiling point when recovering 10 wt% of the second residual fraction from step (c) is in the range between 440°C and 560°C according to ASTM D7169.

7. The process according to claim 1 or 2, wherein the boiling point at the time of recovering 5 wt% of the second residual fraction from step (c) is in the range between 440°C and 560°C according to ASTM D7169.

8. The method according to claim 1 or 2, further comprising: (d) recycling at least a portion of said second residual fraction into step (a).

9. The method according to claim 1 or 2, further comprising: (e) fractionating the distillate base oil fraction into one or more base oils.

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