Method for preparing kerosene

Abstract

The invention provides a process for producing kerosene, the process comprising at least the steps of: (a) providing a syngas stream comprising hydrogen (H2) and carbon monoxide (CO); (b) subjecting the syngas stream provided in step (a) to a Fischer-Tropsch reaction, thereby obtaining a Fischer-Tropsch product comprising at least 50% by weight of compounds boiling above 370 DEG C; (c) separating the Fischer-Tropsch product into at least a C1-C4 fraction, H2O and a C5 + fraction; (d) subjecting the C5 + fraction as separated in step (c) to a hydrotreating, thereby obtaining a mixture comprising at least a kerosene fraction and a heavier fraction; (e) separating the mixture as obtained in step (d), thereby obtaining at least the kerosene fraction and the heavier fraction, in which the kerosene fraction has a final boiling point of at most 302 DEG C, preferably at most 300 DEG C, as determined by ASTM D86-18 and a flash point of at least 38 DEG C, as determined by IP170, in the separation of step (e), preferably at most 300 DEG C, preferably at most 300 DEG C; the effective fractionation point between the kerosene fraction and the heavier fraction, as determined by ASTM D2892-15X2, is at least 315 DEG C and at most 330 DEG C, and wherein in step (e) a kerosene yield of higher than 70 wt% is obtained based on the weight of the C5 + fraction subjected to hydrotreatment in step (d); (f) recycling at least a portion of the heavier fraction as obtained in step (e) to the hydrotreating of step (d); wherein step d) is carried out by contacting the C5 + fraction with a first catalyst, wherein the first catalyst comprises a molecular sieve having a pore size of between 5 angstroms and 7 angstroms and a SiO2 / AlO3 ratio of at least 25 and a Group VIII metal.

Description

Technical Field

[0001] The present invention relates to a process for preparing kerosene, in particular from a Fischer-Tropsch derived product obtained from synthesis gas. Background Art

[0002] It is known in the art to produce 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.

[0003] For example, WO 2015 / 063213 A1 discloses a process 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 WO 2015 / 063213 A1 allows the preparation of lubricating base oils and one or more middle distillate fractions having improved cold flow properties.

[0004] As another example, WO 2021 / 255145 A1 discloses a method for preparing middle distillate oils and base oils from Fischer-Tropsch products. Experiment B and Example 4 of WO 2021 / 255145 A1 show that, in addition to base oils, middle distillates can also be produced by the following line-up: atmospheric distillation operating at an effective fractionation point of about 370°C and recycling the material boiling at above about 540°C obtained from the vacuum distillation step. Example 4 of WO 2021 / 255145 A1 does not provide any indication of the (high) kerosene yield, as only the yield of the 175°C to 370°C middle distillate fraction is shown (in Table 4). The 370°C endpoint of this middle distillate fraction is too high for kerosene, i.e. the 175°C to 370°C middle distillate fraction will contain gas oil and not just kerosene: the total yield of the middle distillate fraction (kerosene and gas oil) as shown in Table 4 on page 21 of WO 2021 / 255145 A1 is 40.4 wt.-%.

[0005] As another example, WO 2006 / 053894 A1 discloses a method for optimizing gas oil yield. As shown on page 11, lines 26 to 30 of WO 2006 / 053894 A1, the kerosene fraction preferably boils more than 80% by weight between 175° C. and 250° C.

[0006] US2004 / 067843 A1 discloses oxygenate treatment of a dewaxing catalyst to obtain a higher yield of dewaxed products. The yields of kerosene or naphtha are not reported.

[0007] Recently, increasing attention has been focused on producing kerosene from renewable raw materials.

[0008] This is because, as explained in, for example, WO 2020 / 154810, jet fuel is the least likely of the transportation fuels to be replaced by non-hydrocarbon-based fuels (such as electricity). To this end, WO 2020 / 154810A1 proposes a method for producing synthetic jet fuel, the method comprising: converting a feedstock into synthesis gas; converting the synthesis gas into a mixture comprising liquid hydrocarbons; refining the mixture comprising liquid hydrocarbons to separate a kerosene product; and hydrotreating the kerosene product to form a synthetic jet fuel. It is apparent from paragraph

[00142] of WO 2020 / 154810 A1 that at least four product fractions are obtained: a) a water-containing product; b) naphtha and gas products; c) a kerosene product; and d) gas oil and heavier products. In the examples of WO 2020 / 154810 A1, several catalysts are mentioned: Examples 1 and 2 mention a non-sulfided H-ZSM-5 oligomerization catalyst and a reduced non-sulfided Ni / Al2O3 hydrotreating catalyst; Example 3 mentions a Pt / SiO2-Al2O3 hydrocracking catalyst. The oligomerization and hydrocracking are carried out at about 1.5 MPa to 3 MPa.

[0009] The final output of the process of WO 2020 / 154810 A1 (see paragraph

[00174] ) is a jet fuel having a high boiling point (e.g., between 140° C. and 260° C.) and a low freezing point (e.g., below -60° C.). Such a low freezing point is not optimal because it is much lower than that required according to the Jet A-1 fuel standard (-47° C.). As also confirmed in paragraph

[00181] , the jet fuel yield obtained according to the process of WO 2020 / 154810 A1 (focusing on jet fuel products having a high boiling point (between 140° C. and 260° C.) and a low freezing point (below -60° C.)) can be optimized.

[0010] In this regard, it should be noted that paragraph

[00187] of WO 2020 / 154810 A1, when discussing hydrocracking of waxes, mentions: "Of interest for the manufacture of synthetic jet fuels is the selectivity ratio of kerosene to naphtha. Under the operating conditions used herein, the mass ratio of hydrocarbons in the boiling range of 140°C to hydrocarbons boiling <140°C is 1:1." This 1:1 mass ratio means that 50% by weight of the hydrocracking products boiling below 260°C are gas and naphtha. This means that higher kerosene yields are possible.

[0011] Therefore, a problem with the method of WO 2020 / 154810 A1 is that the yield of kerosene is limited.

[0012] A further problem with the process according to WO 2020 / 154810 A1 is that the increase in kerosene yield is achieved by means of the oligomerization and hydrotreatment steps, thereby requiring several different processing units with multiple pieces of processing equipment.

[0013] US 2014 / 005450 A1 discloses the use of n-paraffin adsorption to increase selectivity and yield of synthetic distillate fuels. Paragraph

[0015] mentions the cut point being typically between 254°C and 266°C. Summary of the invention

[0014] It is an object of the present invention to solve or minimize at least one of the above problems or other problems.

[0015] It is yet another object of the present invention to provide a method for producing high quality kerosene meeting Jet A-1 specifications (as defined by ASTM D7566-20).

[0016] Another object of the present invention is to provide an alternative process for producing high quality kerosene in high yield (eg above 70%) without the need for (or use of) additional catalytic dewaxing or additional oligomerization.

[0017] According to the present invention, one of the above or other objects can be achieved by providing a method for preparing kerosene, the method comprising at least the following steps:

[0018] (a) providing a synthesis gas stream comprising hydrogen (H2) and carbon monoxide (CO);

[0019] (b) subjecting the synthesis gas stream provided in step (a) to a Fischer-Tropsch reaction thereby obtaining a Fischer-Tropsch product comprising at least 50 wt. % of compounds boiling above 370° C.;

[0020] (c) separating the Fischer-Tropsch product into at least a C1-C4 fraction, H2O and a C5+ fraction;

[0021] (d) subjecting the C5+ fraction separated in step (c) to a hydrotreatment, thereby obtaining a mixture comprising at least a kerosene fraction and a heavier fraction;

[0022] (e) separating the mixture as obtained in step (d) so as to obtain at least the kerosene fraction and the heavier fraction, wherein the kerosene fraction has a final boiling point of at most 302°C, preferably at most 300°C, as determined by ASTM D86-18 and a flash point of at least 38°C, as determined by IP170,

[0023] wherein in the separation of step (e), the effective cut point between the kerosene fraction and the heavier fraction as determined by ASTM D2892-15 X2 is at least 315°C and at most

[0024] 330℃, and

[0025] wherein in step (e), a kerosene yield higher than 70 wt. % is obtained based on the weight of the C5+ fraction subjected to hydrotreatment in step (d);

[0026] (f) recycling at least a portion of the heavier fraction as obtained in step (e) to the hydrotreatment of step (d);

[0027] Wherein step d) is carried out by contacting the C5+ fraction with a first catalyst, wherein the first catalyst comprises a molecular sieve having a pore size between 5 angstroms and 7 angstroms and a SiO2 / AlO3 ratio of at least 25 and a Group VIII metal.

[0028] According to the present invention, it has surprisingly been found that high kerosene yields (>70 wt. %) can be obtained by using a catalyst comprising a molecular sieve having a pore size of between 5 and 7 Angstroms and a SiO2 / AlO3 ratio of at least 25 and a Group VIII metal in the hydroconversion step of a Fischer-Tropsch derived feedstock, and by recycling a relatively wide-cut fraction (i.e. a fraction heavier than kerosene).

[0029] Yet another advantage of the process according to the present invention is that it produces a kerosene fraction having a relatively low aromatics content (meeting the maximum 0.5 wt. % aromatics as specified in ASTM D7566-20 Annex A1).

[0030] Furthermore, using the process according to the invention, kerosene can be obtained in a single hydrocracking step without the need for a separate catalytic dewaxing or oligomerization step (ie less CAPEX, no additional yield loss).

[0031] An important advantage of the present invention is that a high quality kerosene is obtained which is suitable for jet fuel from the freezing point point of view, ie having a freezing point below -40°C (Jet A), preferably below -47°C (Jet A1). DETAILED DESCRIPTION

[0032] In step (a) of the process according to the invention, a synthesis gas stream comprising hydrogen (H2) and carbon monoxide (CO) is provided.

[0033] Since those skilled in the art are familiar with how to provide a synthesis gas stream, it will not be described in detail here. It goes without saying that various carbon-containing (hydrogen) raw materials can be used to provide a synthesis gas stream. Suitable raw materials include natural gas, crude oil, heavy oil fractions, coal, biomass, waste and lignite. Preferably, the raw materials used in the present invention have a renewable source, such as biomass, waste, lignite and captured CO2 (from industry, biological sources or by means of direct air capture). The H2 in the synthesis gas stream can be produced using renewable sources such as wind energy and solar energy.

[0034] In step (b) of the process according to the invention the synthesis gas stream provided in step (a) is subjected to a Fischer-Tropsch reaction thereby obtaining a Fischer-Tropsch product comprising at least 50 wt% of compounds boiling above 370°C.

[0035] Again, since those skilled in the art are familiar with the Fischer-Tropsch reaction and the Fischer-Tropsch product, they will not be described in detail herein.

[0036] The term "Fischer-Tropsch product" means the synthesis product of the Fischer-Tropsch reaction. Fischer-Tropsch products derived from natural gas may also be referred to as GTL (gas to liquid) products. Fischer-Tropsch products derived from other feedstocks may also be referred to as XTL (anything to liquid) products. The preparation of Fischer-Tropsch products by means of the Fischer-Tropsch reaction has been described, for example, in WO 2003 / 070857.

[0037] In step (c) of the process according to the invention, the Fischer-Tropsch product is separated into at least a C1-C4 fraction, H2O and a C5+ fraction.

[0038] Separation of Fischer-Tropsch products is known in the art. Typically, according to the prior art, the Fischer-Tropsch product (which suitably comprises a C1-C300 fraction) is separated into an aqueous stream (which may comprise oxygenated hydrocarbons), a gaseous stream comprising unconverted synthesis gas, carbon dioxide, inert gases and several hydrocarbon fractions. Typically, a lighter fraction comprising a C3 to C9 fraction of the Fischer-Tropsch product, suitably a Fischer-Tropsch product, is separated from the Fischer-Tropsch product by distillation, thereby obtaining a Fischer-Tropsch product stream suitably comprising a C10 to C300 fraction.

[0039] However, according to the present invention, the entire C5+ fraction is separated and further processed. ("wide cut fraction") The C5+ fraction contains hydrocarbons containing 5 carbon atoms (i.e. C5) and heavier hydrocarbons. Preferably, the C5+ fraction contains at least 1.0 wt. % C5-C9, preferably at least 3.0 wt. % C5-C9.

[0040] The Fischer-Tropsch product used in the present invention is typically a paraffinic feedstock comprising at least 50% by weight of compounds boiling 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 sulphur content of less than 0.1% by weight.

[0041] Preferably, at least a portion of the C1-C4 fraction obtained in step (c) is converted into synthesis gas and combined with the synthesis gas stream provided in step (a). This can help to increase the yield of the kerosene fraction.

[0042] In step (d) of the process according to the invention, the C5+ fraction separated as in step (c) and the heavier fraction recycled as in step (f) are subjected as a combined stream to hydrotreatment, thereby obtaining a mixture comprising at least a kerosene fraction and a heavier fraction.

[0043] Since those skilled in the art are familiar with hydroprocessing, it will not be described in detail here.

[0044] The hydroprocessing in step (d) can be carried out in a heavy paraffin conversion unit. In this unit, both hydrocracking and hydroisomerization are carried out in the presence of a catalyst. In the presence of hydrogen, the product stream is contacted at a typical pressure in the range of 20 bara to 100 bara and at a temperature between 250°C and 400°C. Preferably, the hydroprocessing in step (d) is carried out at a pressure higher than 20 bara, preferably higher than 30 bara, more preferably higher than 40 bara. Typically, the hydroprocessing in step (d) is carried out at a pressure lower than 100 bara, preferably lower than 70 bara. Preferably, the hydroprocessing in step (d) is carried out at a pressure higher than 30 bara to 70 bara and at a temperature between 300°C and 400°C.

[0045] 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.

[0046] According to the present invention, step d) is carried out by contacting the C5+ fraction and the heavier fraction recycled as in step (f) as a combined stream with a first catalyst, wherein the first catalyst comprises a molecular sieve having a pore size between 5 angstroms and 7 angstroms and a SiO2 / AlO3 ratio of at least 25 (preferably 50 to 180) and a Group VIII metal.

[0047] Suitably, the first catalyst used in step (d) of the process according to the invention comprises a molecular sieve having a pore size of between 5 Angstroms and 6.6 Angstroms.

[0048] Preferably, the first 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.

[0049] Preferably, the first catalyst comprises 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.

[0050] 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.

[0051] 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.

[0052] Suitable Group VIII metals are in particular nickel, cobalt, platinum and palladium. Preferably, the Group VIII metal is platinum or palladium.

[0053] Preferably, the first catalyst comprises a molecular sieve and platinum or palladium as a Group VIII metal, wherein the molecular sieve is a MTW, MTT, TON type molecular sieve or ZSM-48 or EU-2.

[0054] Suitably, the first catalyst used in step (d) is a dewaxing catalyst. The dewaxing catalyst suitably also comprises a binder. The binder can be non-acidic. Examples of suitable binders are mixtures and combinations of clay, silica, titania, zirconium oxide, aluminum oxide, other binders mentioned above and known to those skilled in the art. Preferably, the catalyst comprises an aluminum oxide, silica or titania binder.

[0055] The preparation of dewaxing catalysts is described, for example, in WO 2015 / 063213 A1. If desired, a dealumination treatment of the zeolite (if used) as described in WO 00 / 29511 A1 (in particular as described on page 10, line 10 to page 11, line 31) can be considered.

[0056] According to a particularly preferred embodiment of the present invention, in step (d), the C5+ fraction and the heavier fraction recycled as in step (f) are contacted as a combined stream with a second catalyst before contacting with the first catalyst, wherein the second catalyst comprises a Group VIII noble metal supported on an amorphous acidic support.

[0057] The amorphous support mentioned herein refers to a support that does not contain zeolite or other crystalline materials. Preferred amorphous acidic supports include refractory metal oxide supports, more preferably silica, alumina, silica-alumina, zirconia, titania and mixtures thereof, even more preferably silica, alumina and silica-alumina.

[0058] A particularly preferred second catalyst comprises platinum supported on a silica-alumina support.

[0059] The second catalyst preferably comprises a Group VIII noble metal as a hydrogenation / dehydrogenation functional group. The Group VIII noble metal is preferably palladium, platinum or a combination thereof, more preferably platinum. The second catalyst can comprise a Group VIII noble metal in an amount of 0.005 to 5 weight parts, preferably 0.02 to 2 weight parts per 100 weight parts of carrier material. A particularly preferred second catalyst comprises platinum in an amount of 0.05 to 2 weight parts, more preferably 0.1 to 1 weight parts per 100 weight parts of carrier material. The second catalyst may also comprise an adhesive to enhance the strength of the catalyst. The adhesive may be non-acidic. Examples are clay and other adhesives known to those skilled in the art. Examples of catalysts suitable for use as the second catalyst are described in WO-A-0014179, EP-A-532118, EP-A-666894, EP-A-776959 and WO2009 / 080681.

[0060] According to another preferred embodiment of the present invention, in step (d), the C5+ fraction and the heavier fraction recycled as in step (f) are contacted as a combined stream with a second catalyst after contacting with the first catalyst, wherein the second catalyst comprises a Group VIII noble metal supported on an amorphous acidic support.

[0061] It is generally preferred that where both the first catalyst and the second catalyst are present, the amount of catalyst used as in step d) comprises 10 to 90 volume % of the first catalyst and 90 to 10 volume % of the second catalyst.

[0062] In step (e) of the process according to the invention, the mixture as obtained in step (d) is separated so as to obtain at least a kerosene fraction and a heavier fraction, wherein the kerosene fraction has a final boiling point of at most 302° C., preferably at most 300° C., as determined by ASTM D86-18, and a flash point of at least 38° C., as determined by IP170. In this regard, it is noted that ASTM 7566-20 Annex A1 also specifies other methods for determining the flash point besides IP170, which other methods (e.g. ASTM D56) produce similar values.

[0063] The separation in step (e) is generally carried out by means of atmospheric distillation.

[0064] Preferably, the kerosene fraction obtained in step (e) has a freezing point of at most -40°C, preferably at most -47°C, as determined by ASTM D5972. In this way, the kerosene fraction obtained in step (e) 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. In this regard, it is noted that ASTM 7566-20 Annex A1 also specifies other methods for determining freezing point in addition to ASTM D5972, which other methods (e.g. ASTM D2386) produce similar values.

[0065] Furthermore, it is preferred that the kerosene fraction obtained in step (e) has a C16+ amount of at least 5 wt.-%, preferably at least 10 wt.-%, more preferably at least 15 wt.-%, even more preferably at least 20 wt.-%.

[0066] According to the present invention, in the separation of step (e), the effective cut point between the kerosene fraction and the heavier fraction as determined by ASTM D2892-15 X2 is at least 315° C. and at most 330° C., preferably at most 325° C. Preferably, the effective cut point between the kerosene fraction and the heavier fraction, again as determined by ASTM D2892-15 X2, is at least 316° C., more preferably at least 317° C., even more preferably at least 318° C., yet even more preferably at least 319° C. and most preferably at least 320° C. In this regard it should be noted that this effective cut point as determined by ASTM D2892-15 X2 is measured by a different method than the above-mentioned FBP as determined by ASTM D86-16 (and therefore may result in different values).

[0067] A person skilled in the art will readily appreciate that in step (e) in addition to the kerosene fraction and the heavier fractions further fractions may be obtained from the mixture as obtained in step (d). Examples are the second C1-C4 fraction and the naphtha fraction.

[0068] According to a particularly preferred embodiment of the present invention, a second C1-C4 fraction and a naphtha fraction are also obtained in step (e), wherein at least a portion of the second C1-C4 fraction and / or the naphtha fraction is converted into synthesis gas and combined with the synthesis gas stream provided in step (a).

[0069] In the context of the present invention, the naphtha fraction comprises at least 50 wt% C5-C7, preferably at least 75 wt% C5-C7.

[0070] According to the invention, in step (e) a kerosene yield higher than 70% by weight is obtained, based on the weight of the C5+ fraction subjected to hydrotreatment in step (d).

[0071] In step (f) of the process according to the invention, at least a portion of the heavier fraction as obtained in step (e) is recycled to the hydrotreatment of step (d). Preferably, a large portion (at least 50% by weight), more than 90% by weight or even all of the heavier fraction as obtained in step (e) is recycled to the hydrotreatment of step (d).

[0072] For clarity, it should be noted that this heavier fraction is combined with the C5+ fraction and subjected to hydroprocessing as a combined stream.

[0073] An important aspect of the process according to the invention is the separation of a "wider cut" (as a "heavier fraction") from the kerosene fraction in step (e) and the recycling of this wider cut to the hydrotreatment step in step (d). In this regard it should be noted that the recycling of the fraction obtained in the separation step has been proposed before, but such recycling would be limited to a "smaller cut" (such as the recycling of the second residual fraction proposed in WO 2021 / 255145 A1, which is the residual base oil).

[0074] The present invention will be further illustrated by the following non-limiting examples.

[0075] Example

[0076] Example 1 (The present invention)

[0077] The Fischer-Tropsch product is obtained by separating the effluent from the Fischer-Tropsch process in a waste gas stream comprising C1-C4 hydrocarbons, an aqueous stream comprising dissolved oxygenated hydrocarbons, a light wax stream and a heavy wax stream in a series of hot and cold separators, high pressure separators and low pressure separators.

[0078] The light wax stream and the heavy wax stream were combined to form the C5+ fraction used in the experiments. The C5+ fraction contained 6.8 wt% boiling below 150°C and 58.9 wt% boiling above 370°C as determined according to ASTM D-7169 and ASTM D-2887.

[0079] The entire C5+ fraction (ie a relatively "wide cut") was fed continuously to a hydrocracking step operated at a pressure of 60 barg and a temperature of 341 °C.

[0080] In the hydrocracking step, the C5+ feed was contacted in a reactor with a silica-bound, ammonium hexafluorosilicate-treated Pt / ZSM-12 catalyst (referred to as the "first catalyst" according to the present invention) having a maximum pore size of 6.0 angstroms and a SAR of 90. The weight hourly space velocity (based on the total volume of catalyst in the reactor) was 1.0 kg of fresh feed per liter of catalyst per hour.

[0081] The liquid products from the hydrocracking step were separated into a light fraction comprising kerosene and a heavier fraction in a fractionator having an effective cut point (as determined by ASTM D2892-15X2) of 319° C. The boiling point distributions of the light fraction comprising kerosene and the heavier fraction were determined according to ASTM D-2887 and ASTM D-7169, respectively.

[0082] The heavier fractions were recycled to the hydrocracking step at a combined feed ratio of 1.47.

[0083] The weighted average bed temperature is adjusted until there is no net accumulation of heavier fractions, ie until the flow rate of heavier fractions is 0.47 times the fresh feed flow rate.

[0084] Using the boiling point distribution determined according to ASTM D-2887, the light fraction containing kerosene was separately distilled into a kerosene fraction and a light fraction (mainly containing C5-C8 naphtha) based on ASTM D2892-15 X2 at an effective cut point of 125° C. The yield of the kerosene fraction was 70.9 wt % based on the fresh C5+ fraction fed.

[0085] The properties of the kerosene fractions are shown in Table 1 below.

[0086] Table 1 . Properties of kerosene fractions

[0087]

[0088]

[0089] 1 Specifications = Specifications according to ASTM D7566-20

[0090] 2 Reporting = This value needs to be reported on the Certificate of Analysis / Quality Certificate for the fuel, but is not a minimum or maximum specification.

[0091] discuss

[0092] As can be seen from Table 1 above, by using a catalyst comprising a molecular sieve (having a pore size between 5 Å and 7 Å and a SiO2 / AlO3 ratio of at least 25) and a Group VIII metal in the hydroconversion step of a Fischer-Tropsch derived C5+ fraction, and by recycling the "wide cut" 319°C+ fraction, a high yield (higher than 70 wt%) of high quality kerosene is obtained without the need for additional catalytic dewaxing or additional oligomerization.

[0093] In this regard it should be noted that although there are significant amounts of material boiling above 260°C in the kerosene fraction, the freezing point is well below the minimum specification of -40°C, and even below the -47°C specified for Jet A1.

[0094] The final boiling point (FBP) of kerosene of 291°C, which is well below the specified maximum of 300°C, suggests that further optimization of kerosene yield is possible by optimizing the effective cut point between kerosene and recycled heavier fractions.

[0095] Furthermore, the flash point of +44°C, which is well above the specified minimum of +38°C, indicates that the kerosene yield can be further optimized by optimizing the cut point between kerosene and light fractions.

[0096] Example 2 (The present invention)

[0097] Analogously to Example 1 , a C5+ Fischer-Tropsch product comprising 4.7 wt% boiling below 150°C and 67 wt% boiling above 370°C was continuously fed to the hydrocracking step at 60 barg and a temperature of 343.4°C.

[0098] In the hydrocracking step, a fresh C5+ fraction is supplied to a reactor comprising a stacked bed of a first catalyst below a second catalyst. The volume ratio of the second catalyst to the first catalyst is 4:1. The C5+ fraction contacts the second catalyst before contacting the first catalyst. The weight hourly space velocity (based on the total volume of catalyst in the reactor) is 1.0 kg fresh feed per liter of catalyst per hour.

[0099] The first catalyst was the silica-bound, ammonium hexafluorosilicate-treated Pt / ZSM-12 catalyst from Example 1. The second catalyst comprised 0.8 wt% platinum on an amorphous silica-alumina support.

[0100] The liquid product from the hydrocracking step was separated into a light fraction comprising kerosene and a heavier fraction in a fractionator having an effective cut point (as determined by ASTM D2892-15X2) of 328.5° C. The boiling point distribution of the light fraction comprising kerosene and the heavier fraction was determined according to ASTM D-2887 and ASTM D-7169, respectively.

[0101] The heavier fractions were recycled to the hydrocracking step at a combined feed ratio of 1.57. The weighted average bed temperature was adjusted until there was no net accumulation of heavier fractions, ie until the flow rate of heavier fractions was 0.57 times the fresh feed flow rate.

[0102] The kerosene fraction was separately distilled into a kerosene fraction and a light fraction at an effective cut point of 125° C. based on ASTM D2892-15 X2 using a boiling point distribution determined according to ASTM D2887.

[0103] The yield of the kerosene fraction was 77.2% by weight, based on the fresh C5+ fraction fed.

[0104] The properties of the kerosene fractions are shown in Table 1 above.

[0105] discuss

[0106] As can be seen from Table 1 above, the use of stacked beds and by recycling the "wide cut" 328.5°C+ fraction allows the production of high yields (more than 70% by weight) of high quality kerosene with a freezing point below -47°C (meeting the Jet A1 standard). This does not require additional catalytic dewaxing or additional oligomerization.

[0107] In this regard it should be noted that although there are significant amounts of material boiling above 260°C in the kerosene fraction, the freezing point is well below the minimum specification of -40°C, and even below the -47°C specified for Jet A1.

[0108] The D86 final boiling point (FBP) of the kerosene of Example 2 at 302° C. is slightly above the specified maximum value of 300° C. Those skilled in the art will readily appreciate that further optimization of the effective cut point and / or the sharpness of separation between the kerosene and the recycled heavier fractions will likely result in a FBP below the specified maximum value of 300° C. Such optimization will have only a small effect on the yield obtained, and a reduction in FBP is not expected to result in a deterioration in the freezing point.

[0109] Furthermore, the flash point of +43.5°C, which is well above the specified minimum of +38°C, indicates that the kerosene yield can be further optimized by optimizing the cut point between kerosene and light fractions.

[0110] Example 3 (Comparative Example)

[0111] The experiment of Example 2 was repeated, except that:

[0112] - the reactor in the hydrocracking step contains only the second catalyst comprising 0.8 wt. % platinum on an amorphous silica-alumina support, as described in Example 2;

[0113] - the temperature in the hydrocracking step was 344.1°C; and

[0114] - The effective cut point between the light fractions including kerosene and the heavier fractions is 329°C.

[0115] The yield of the kerosene fraction was 77.2% by weight, based on the fresh C5+ fraction fed.

[0116] The properties of the kerosene fractions are shown in Table 1 above.

[0117] discuss

[0118] The data of Comparative Example 3 in Table 1 above show that it is not possible to obtain a kerosene fraction with a high C16+ content that meets the freezing point specification of a maximum of -40°C, let alone -47°C, using only the second catalyst.

[0119] To meet the freezing point specification of maximum -40°C, the kerosene fraction would need to be fractionated more lightly (perhaps by using a cut of 140°C to 260°C), but this would be at the expense of kerosene yield and would take it well below 70 wt%. It is estimated that when only the second catalyst is used, the kerosene yield will be in the range of 50 wt% to 60 wt% based on fresh C5+ feed.

[0120] Those skilled in the art will readily appreciate that many modifications may be made without departing from the scope of the invention.

Claims

1. A method for preparing kerosene, the method comprising at least the following steps: (a) providing a synthesis gas stream comprising hydrogen (H2) and carbon monoxide (CO); (b) subjecting the synthesis gas stream provided in step (a) to a Fischer-Tropsch reaction, thereby obtaining a Fischer-Tropsch product comprising at least 50 wt. % of compounds boiling above 370° C.; (c) separating the Fischer-Tropsch product into at least a C1-C4 fraction, H2O and a C5+ fraction; (d) subjecting said C5+ fraction separated as in step (c) to hydrotreatment, thereby obtaining a mixture comprising at least a kerosene fraction and a heavier fraction; (e) separating said mixture as obtained in step (d) so as to obtain at least said kerosene fraction and said heavier fraction, wherein said kerosene fraction has a final boiling point of at most 302°C, preferably at most 300°C, as determined by ASTM D86-18 and a flash point of at least 38°C, as determined by IP170, wherein in the separation of step (e), the effective cut point between the kerosene fraction and the heavier fraction as determined by ASTM D2892-15 X2 is at least 315°C and at most 330°C, and wherein in step (e), a kerosene yield higher than 70 wt. % is obtained based on the weight of the C5+ fraction subjected to hydrotreatment in step (d); (f) recycling at least a portion of said heavier fraction as obtained in step (e) to said hydrotreatment of step (d); Wherein step d) is carried out by contacting the C5+ fraction with a first catalyst, wherein the first catalyst comprises a molecular sieve having a pore size between 5 and 7 angstroms and a SiO2 / AlO3 ratio of at least 25 and a Group VIII metal.

2. The process according to claim 1, wherein at least a portion of the C1-C4 fraction obtained in step (c) is converted into synthesis gas and combined with the synthesis gas stream provided in step (a).

3. The process according to claim 1 or 2, wherein the hydrotreatment in step (d) is carried out at a pressure higher than 20 bara, preferably higher than 30 bara, more preferably higher than 40 bara.

4. The process according to any one of the preceding claims, wherein the first catalyst comprises a molecular sieve and platinum or palladium as Group VIII metal, and wherein the molecular sieve is a MTW, MTT, TON type molecular sieve or ZSM-48 or EU-2.

5. The process according to any one of the preceding claims 1 to 4, wherein in step (d), the C5+ fraction is contacted with a second catalyst before contacting with the first catalyst, wherein the second catalyst comprises a Group VIII noble metal supported on an amorphous acidic support.

6. The process according to any one of the preceding claims 1 to 4, wherein in step (d), the C5+ fraction is contacted with a second catalyst after contacting with the first catalyst, wherein the second catalyst comprises a Group VIII noble metal supported on an amorphous acidic support.

7. The process according to claim 5 or 6, wherein the amount of catalyst used in step d) comprises 10 to 90 volume % of the first catalyst and 90 to 10 volume % of the second catalyst.

8. The process according to any one of the preceding claims, wherein the kerosene fraction obtained in step (e) has a freezing point as determined by ASTM D5972 of at most -40°C, preferably at most -47°C.

9. The process according to any one of the preceding claims, wherein the kerosene fraction obtained in step (e) has a C16+ amount of at least 5 wt.-%, preferably at least 10 wt.-%, more preferably at least 15 wt.-%, even more preferably at least 20 wt.-%.

10. The process according to any one of the preceding claims, wherein in the separation of step (e), the effective cut point between the kerosene fraction and the heavier fraction as determined by ASTM D2892-15 X2 is at most 325°C.

11. The process according to any one of the preceding claims, wherein in step (e) a second C1-C4 fraction and a naphtha fraction are also obtained, wherein at least a portion of the second C1-C4 fraction and / or the naphtha fraction is converted into synthesis gas and combined with the synthesis gas stream provided in step (a).

12. The process according to any one of the preceding claims, wherein in step (e) the separation is carried out by atmospheric distillation.

13. Process according to any one of the preceding claims, wherein the kerosene fraction is obtained without a separate catalytic dewaxing or oligomerization step and wherein the hydrotreatment in step d) is carried out in a heavy paraffin conversion unit, preferably without subsequent separation of n- and iso-paraffins.

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