WO2009116988A1 - Process for the preparation of middle distillates from kerogen - Google Patents

Process for the preparation of middle distillates from kerogen Download PDF

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WO2009116988A1
WO2009116988A1 PCT/US2008/057236 US2008057236W WO2009116988A1 WO 2009116988 A1 WO2009116988 A1 WO 2009116988A1 US 2008057236 W US2008057236 W US 2008057236W WO 2009116988 A1 WO2009116988 A1 WO 2009116988A1
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step
gas oil
fuel
product
diesel
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PCT/US2008/057236
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French (fr)
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Joanna Margaret Bauldreay
Vijay Nair
Augustinus Wilhelmus Maria Roes
James Timothy Talbert
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Shell Oil Company
Shell Internationale Research Maatschappij B.V.
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    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10LFUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
    • C10L1/00Liquid carbonaceous fuels
    • C10L1/04Liquid carbonaceous fuels essentially based on blends of hydrocarbons
    • C10L1/08Liquid carbonaceous fuels essentially based on blends of hydrocarbons for compression ignition
    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G2400/00Products obtained by processes covered by groups C10G9/00 - C10G69/14
    • C10G2400/06Gasoil

Abstract

The present invention relates to a process for the preparation of a middle distillate fuel from a kerogen pyrolysis product, comprising (a) hydrotreating the middle distillate fraction of a kerogen pyrolysis product; (b) separating the product of step (a) into at least one or more lower boiling fractions and a gas oil precursor fraction; (c) catalytically dewaxing the gas oil precursor fraction obtained in step (b); and (d) isolating the catalytically dewaxed gas oil or gas oil blending component from the product of step (c) by means of distillation. It further relates to a Diesel base fuel obtainable by the process.

Description

PROCESS FOR THE PREPARATION OF MIDDLE DISTILLATES

FROM KEROGEN

The present invention relates to a process for the preparation of novel base fuels, their preparation from kerogen materials from oil shale, and their use in compression ignition (diesel) engines or aviation engines.

Oil shale is a fine-grained sedimentary rock containing kerogen. The latter is a solid mixture of hydrocarbons. The kerogen in oil shale can be converted to a synthetic crude, through mining and subsequent surface retorting of the mined product, as described for example in Ullman' s Encyclopedia of Industrial Chemistry, Fifth Edition, Volume 18A, VCH Publishers, 1991, 101-126. When heated to a sufficiently high temperature, a full range liquid shale oil product and a combustible shale gas is yielded. A work-up procedure of a full range shale oil to obtain lubricating base oils is described for instance in US-A-4 , 744 , 884. This document discloses a process comprising hydrotreating of a full range shale oil, followed by hydrodewaxing the fraction boiling above 343°C derived from the hydrotreating step. The full range shale oil is most likely obtained from a mined and subsequently retorted full range shale oil. The product from the hydrodewaxing step has subsequently to be hydrogenated. After hydrogenating, the product from the hydrogenation stage is fractionated into one or more lubricating oil fractions. This process is rather complex. Furthermore, it contains a number of distillations which are energy consuming. The products disclosed in US-A-4 , 744 , 884 comprise high concentrations of polynaphthenic compounds as well as of unsaturated compounds, including polyaromatic compounds, which are highly undesirable when a product is desired with a high thermal stability.

Applicants have now found that a middle distillate fuel product with high thermal stability and good cetane index can be obtained from oil shale by subjecting the oil shale to if the oil shale is converted in an in-situ conversion, and if the thus obtained in-situ syncrude is hydrotreated and subsequently hydrodewaxed. Accordingly, the present invention relates to a process for the preparation of a middle distillate fuel from a kerogen pyrolysis product, comprising

(a) hydrotreating the middle distillate fraction of a kerogen pyrolysis product, and (b) separating the product of step (a) into at least one or more lower boiling fractions and a gas oil precursor fraction, and

(c) catalytically dewaxing the gas oil precursor fraction obtained in step (b) , and (d) isolating the catalytically dewaxed gas oil or gas oil blending component from the product of step (c) by means of distillation .

Applicants have found that the pyrolysis product of kerogen in oil shale may be converted to a middle distillate base fuel or a fuel blending component having a high energy content, relatively low density, and high thermal stability, and a high cetane number, and good low temperature performance through a relatively simple process, and under mild conditions . The above process is found further advantageous because it yields a middle distillate such as either a gas oil (blending component) in step (d) having excellent cold flow properties like the cloud point and cold filter plugging point. Furthermore a gas oil (blending component) with excellent lubricity properties is obtained. Finally the yield on feed to step (a) of all gas oil fractions as recovered in step (b) and in step (d) is high.

As feed for step (a) , preferably a synthetic crude is produced from the kerogen in the oil shale formation utilizing downhole heaters, producing a hydrocarbon fluid from the formation by pyrolysing hydrocarbons present in the formation. This process has been described for instance in US-A-2634961, US-A-2732195, US-A-2780450, US-A-2789805, US-A- 2923535, US-A-4886118, US-A-2914309, US-A-4344483, US-A- 4067390, US-A-4662439, US-A-4384613, US-A-2923535, US-A- 4886118 and EP-A-1276959. This process treats a hydrocarbon containing formation in situ and produces a hydrocarbon fluid from the formation by pyrolysing hydrocarbons present in the formation. The term "pyrolysis product" generally refers to a fluid produced substantially during pyrolysis of hydrocarbons. As used herein, a "pyrolysis zone" generally refers to a volume of hydrocarbon containing formation that is reacted or reacting to form a pyrolysis product. The pyrolysis product may be obtained either from an in-situ process, wherein the heat is generate in a kerogen containing formation to produce a pyrolysis product, or a to a surface retorting of kerogenic material. Preferably, the pyrolysis product is obtained in the in-situ process, since the pyrolysis products having a low olefin content (e.g.<10% by weight) and low average carbon number (e.g.<35) . The absence of larger amounts of components having more than 35 carbon atoms is particularly beneficial for the manufacture of fuel products, since the need for conversion of these compounds through suitable conversion processes such as thermal or catalytic cracking into the fuel carbon range to obtain a product in the Diesel boiling range is only strongly reduced. An example of such a process is that disclosed in EP-A- 1276959, wherein a system of heat injection and hydrocarbon fluid production wells for use in the method according to the invention and pyrolysis products having a low olefin content (e.g.<10% by weight) and low average carbon number (e.g.<35) which are obtainable by the in-situ pyrolysis method and system is described in some detail. Preferably, the middle distillate fraction of a kerogen pyrolysis product is derived from an in-situ conversion of oil shale set out above. Such feeds were further found to contain only a limited amount of metals, generally present in concentrations below 1.0 ppmw, with most of the metals present in much lower concentrations . However, preferably a guard bed of appropriate demetalization catalyst is employed to efficiently remove any metal ions considered to interfere with the catalysts of steps (a) and/or (c) . The term "middle distillate fraction" herein refers to the hydrocarbonaceous product boiling in the range of from 1800C to 4000C (ASTM D86) . This middle distillate range comprises a kerosene fraction (usually boiling of from 180 to about 2300C) and a Diesel fraction (usually boiling of from about 230 to 400°C) .

Although full range shale oil, or middle distillate fractions of shale oil derived from conventional surface retorting may be employed, these products are generally less suitable for the subject process due to the high content of metals, heteroatom containing compounds, and olefins. This may require a pre-treatment, e.g. to remove arsenic, copper iron and/or zinc ions present in the feed. Furthermore, in order to achieve products of sufficiently high stability and cetane numbers, rather stringent treatment conditions have to be employed in steps (a) and (c) , and the yields are lower.

The hydrotreating reaction of step (a) is preferably performed in the presence of hydrogen and a catalyst, which catalyst can be chosen from those known to one skilled in the art as being suitable for this reaction. Catalysts for use in step (a) typically comprise an acidic functionality and a hydrogenation-dehydrogenation functionality. Preferred acidic functionalities are refractory metal oxide carriers . Suitable carrier materials include silica, alumina, silica-alumina, zirconia, titania and mixtures thereof. Preferred carrier materials for inclusion in the catalyst for use in the process of this invention are silica, alumina and silica- alumina .

Preferred hydrogenation-dehydrogenation functionalities are Group VIII non-noble metals, for example iron, nickel and cobalt which non-noble metals may or may not be combined with a Group IVB metal, for example W or Mo, oxide promoters. The catalyst may comprise the hydrogenation/dehydrogenation metal active component in an amount of from 0.005 to 5 parts by weight, preferably from 0.02 to 2 parts by weight, per 100 parts by weight of carrier material .

A particularly preferred catalyst comprises an alloy of Nickel and Molybdenum and/or Cobalt and molybdenum on an alumina carrier. If desired, applying a halogen moiety, in particular fluorine, or a phosphorous moiety to the carrier, may enhance the acidity of the catalyst carrier. Examples of suitable hydrocracking/hydroisomerisation processes and suitable catalysts are described in WO-A-0014179, EP-A- 532118, EP-A-666894 and EP-A-776959. Preferably, the catalyst bed is protected by a guard bed against potential fouling due to particulates, asphaltenes, and/or metals present in the feed.

Preferably any compounds having 4 or less carbon atoms and any compounds having a boiling point in that range are separated from the synthetic crude product before being used in step (a) . The synthetic crude product preferably has not been subjected to any hydroconversion step on the surface apart from the, above referred to, optional mild hydrotreating step. In addition to the synthetic crude also other feeds may be additionally processed in step (a) . Possible other fractions may suitably be a higher boiling fraction obtained in step (b) or part of said fraction and/or one or more of the fractions boiling above the gas oil range as obtained in step (c) . In step (a) the feed is contacted with hydrogen in the presence of the catalyst at elevated temperature and pressure. The temperatures typically will be in the range of from 175 to 380 0C, preferably higher than 250 0C and more preferably from 300 to 370 0C, and yet more preferably from at a reactor temperature from 343 to to 370 0C (650 to 700° F) .

Preferably, step (a) is performed at a pressure reactor pressure between at 500 and 5000 psig reactor pressure, preferably at 750 to 2500, more preferably at 1000 to 1800 psig. Liquid hourly space velocities (LHSV) are preferably in the range of from of 0.5 - 1.0 1/hr, and hydrogen treat rates preferably in the range of from 4,000 - 5,000 SCF/bbl. In step (b) the product of step (a) is preferably separated into one or more fuel fractions, and a gas oil precursor fraction having preferably a TlO wt% (as determined by ASTM method D86) boiling point of between 200 and 450 0C. The T90 wt% boiling point of the gas oil precursor fraction is preferably between 300, and preferably between 400 and 550 0C If the product of step (a) contains higher boiling compounds, a separate higher boiling fraction may be removed from the gas oil precursor fraction in order to meet these T90 wt% boiling points. By performing step (c) on the preferred narrow boiling gas oil precursor fraction obtained in step (b) a gas oil fraction can be obtained having the desired cold flow properties. The separation is preferably performed by means of a first distillation at about atmospheric conditions, preferably at a pressure of between 1.2-2 bara, wherein the fuel product, such as naphtha, kerosene and gas oil fractions, are separated from the higher boiling fraction of the product of step (a) . The gas oil fraction obtained directly in step (a) will be referred to as the hydrocracked gas oil fraction. The higher boiling fraction, of which suitably at least 95 wt% boils above 370 0C, is subsequently further separated in a vacuum distillation step wherein a vacuum gas oil fraction, the gas oil precursor fraction and the higher boiling fraction are obtained. The vacuum distillation is suitably performed at a pressure of between 0.001 and 0.05 bara.

The vacuum distillation of step (b) is preferably operated such that the desired gas oil precursor fraction is obtained boiling in the specified range. Preferably the kinematic viscosity at 100 0C of the gas oil precursor fraction is between 3 and 10 cSt .

Catalytic dewaxing step (c) will be performed in the presence of hydrogen and a suitable dewaxing catalyst at catalytic dewaxing conditions. Suitable dewaxing catalysts are heterogeneous catalysts comprising a molecular sieve and optionally in combination with a metal having a hydrogenation function, such as the Group VIII metals. Molecular sieves, and more suitably intermediate pore size zeolites, have shown a good catalytic ability to reduce the pour point and cloud point of the gas oil precursor fraction under catalytic dewaxing conditions. Preferably the intermediate pore size zeolites have a pore diameter of between 0.35 and 0.8 nm. Suitable intermediate pore size zeolites are mordenite, ZSM- 5, ZSM-12, ZSM-22, ZSM-23, SSZ-32, ZSM-35 and ZSM-48. Another preferred group of molecular sieves are the silica- aluminaphosphate (SAPO) materials, for example SAPO-31, SAPO- 41 and SAPO-Il of which SAPO-Il is most preferred as for example described in US-A-4859311. ZSM-5 may optionally be used in its HZSM-5 form in the absence of any Group VIII metal. The other molecular sieves are preferably used in combination with an added Group VIII metal. Suitable Group VIII metals are nickel, cobalt, platinum and palladium. Examples of possible combinations are Pt/mordenite, Pt/ZSM- 35, Ni/ZSM-5, Pt/ZSM-23, Pd/ZSM-23, Pt/ZSM-12, Pt/ZSM-48 and Pt/SAPO-11. Further details and examples of suitable molecular sieves and dewaxing conditions are for example described in WO-A-9718278, US-A-4343692, US-A-5053373, WO-A- 0014184, US-A-5252527 and US-A-4574043.

The dewaxing catalyst suitably also comprises a binder. The binder can be a synthetic or naturally occurring (inorganic) substance, for example clay, silica and/or metal oxides . Natural occurring clays are for example of the montmorillonite and kaolin families. The binder is preferably a porous binder material, for example a refractory oxide of which examples are: alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica- titania as well as ternary compositions for example silica- alumina-thoria, silica-alumina-zirconia, silica-alumina- magnesia and silica-magnesia-zirconia . More preferably a low acidity refractory oxide binder material, which is essentially free of alumina, is used. Examples of these binder materials are silica, zirconia, titanium dioxide, germanium dioxide, boria and mixtures of two or more of these of which examples are listed above. The most preferred binder is silica.

If a dewaxing catalyst is employed that requires activation though sulphur or nitrogen poisoning, and if step (a) was performed such that the remaining sulphur and/or nitrogen levels are too low to achieve sufficient catalyst activation, additional mercaptanes and/or amines may be added to the feed to step (c) .

A preferred class of dewaxing catalysts comprise intermediate zeolite crystallites as described above and a low acidity refractory oxide binder material which is essentially free of alumina as described above, wherein the surface of the aluminosilicate zeolite crystallites has been modified by subjecting the aluminosilicate zeolite crystallites to a surface dealumination treatment.

A preferred dealumination treatment is by contacting an extrudate of the binder and the zeolite with an aqueous solution of a fluorosilicate salt as described in for example US-A-5157191 or WO-A-0029511.

In the case of a feed that is essentially free of sulphur or nitrogen containing compounds, suitable dewaxing catalysts as described above are silica bound and dealuminated Pt/ZSM-5, silica bound and dealuminated Pt/ZSM- 23, silica bound and dealuminated Pt/ZSM-12, silica bound and dealuminated Pt/ZSM-22, as for example described in WO-A- 0029511 and EP-B-832171. Catalytic dewaxing conditions are known in the art and typically involve operating temperatures in the range of from 200 to 500 0C, suitably from 250 to 400 0C, hydrogen pressures in the range of from 10 to 200 bar, preferably from 40 to 70 bar, weight hourly space velocities (WHSV) in the range of from 0.1 to 10 kg of oil per litre of catalyst per hour (kg/l/hr) , suitably from 0.2 to 5 kg/l/hr, more suitably from 0.5 to 3 kg/l/hr and hydrogen to oil ratios in the range of from 100 to 2,000 litres of hydrogen per litre of oil. In step (d) the catalytically dewaxed gas oil fraction is isolated from the product of step (c) by means of distillation. Preferably a vacuum distillation is used, such that also the fraction boiling above the gas oil range can be separated into useful products.

Applicants have found that the gas oil base fuel as obtained in step (d) has superior cold temperature performance at a high flash point. This is advantageous since the higher average molecular weight of such fuel makes it intrinsically safer in the case of handling or spills. The cold temperature conditions comprise the cloud point as determined by International Standard ISO 3015. The cloud point of the gas oil as obtained in step (d) is preferably below -40 0C and more preferably below -50 0C. A further important cold temperature feature, the cold filter plugging point (CFFP) as determined by European Standard EN 116 of the gas oil as obtained in step (d) is preferably below -30 0C and more preferably below -40 0C.

The gas oil obtained in step (d) can be directly used as a gas oil product or may be used as blending component together with other gas oil blending components . The other blending components may suitably be the gas oil fraction (s) obtained in step (b) of the above process. These gas oil fractions are suitably obtained in the atmospheric distillation of step (b) and in the vacuum distillation of step (b) . In a preferred embodiment prior to performing step (b) the, preferably entire, effluent of step (a) is subjected to a catalytic dewaxing step under the dewaxing process conditions and in the presence of the catalyst as described for step (c) . In this manner the cold flow properties of the gas oil and kerosene fractions obtained in step (b) are also improved resulting in a blend which is even more suited as a winter gas oil fuel. This dewaxing step may be performed in the same reactor as wherein step (a) is performed. A stacked bed reactor comprising the hydro- cracking/hydroisomerisation catalyst on top of the dewaxing catalyst would be a practical and preferred embodiment of how such a reactor would look like. The dewaxed gas oil as obtained in step (d) is preferably blended with the gas oil fraction (s) obtained in step (b) of the above process. A blend having improved cold flow properties is thus obtained in a high yield. Blending can be achieved in a tanker park, direct in-line blending of the effluents of steps (b) and (d) or by recycling the dewaxed gas oil as obtained in step (d) to step (b) . In the latter preferred option the dewaxed gas oil is suitably fed to the atmospheric distillation of step (b) .

Also gas oil blending components as obtained from a raw gas field condensate distillate, a mildly hydrotreated gas field condensate distillate or a crude petroleum source, for example straight run gas oil, cat cracked gas oil and hydrocracked gas oil, may be combined with the dewaxed gas oil as for example described in WO-A-0011116.

The product fractions obtained may be employed as kerosene for primary use as jet fuel, and a higher boiling Diesel for primary use in compression ignition engines.

Diesel fuel compositions usually contain one or more base fuels which may typically comprise liquid hydrocarbon middle distillate gas oil(s) . Such fuel compositions will typically have boiling points within the usual middle distillate range of 150 to 4000C, depending on grade and use.

They will typically have a density from 750 to 1000 kg/m^, preferably for automotive uses from 780 to 860 kg/m^, at 15°C (e.g. ASTM D4502 or IP 365) and a cetane number (ASTM D613) of from 35 to 120, more preferably from 40 to 85. They will typically have an initial boiling point in the range 150 to 2300C and a final boiling point in the range 290 to 4000C. Their kinematic viscosity at 400C (ASTM D445) might suitably be from 1.5 to 6 cSt .

Industrial gas oils will contain a base fuel which may comprise fuel fractions such as the kerosene or gas oil fractions obtained in traditional refinery processes, which upgrade crude petroleum feedstock to useful products . Preferably such fractions contain components having carbon numbers in the range 5 to 40, more preferably 5 to 31, yet more preferably 6 to 25, most preferably 9 to 25, and such fractions have a density at 15°C of 650 to 1000 kg/m^, a kinematic viscosity at 200C of 1 to 80 cSt, and a boiling range of 150 to 400°C.

Furthermore, the fuels of the present invention preferably contain low levels of olefins. The fuels of the present invention preferably contain <5.0 weight% olefins, more preferably <2.0 weight % olefins, and even more preferably <1.0 weight % olefins. The weight % olefins can be calculated from the bromine number and the average molecular weight by use of the following formula: Wt % 01efins= (Bromine No.) (Average Molecular Weight) /159.8.

According to the present invention there is yet further provided a method of operating a jet engine or a diesel engine and/or an aircraft which is powered by one of more of said engines, which method involves introducing into said engine a fuel composition according to the present invention .

According to the present invention there is yet further provided a process for the preparation of a fuel composition which process involves blending a petroleum derived Diesel fuel with the Diesel base fuel.

The present invention may be used to formulate fuel blends which are expected to be of particular use in modern commercially available internal compression ignition engines as alternatives to the standard engine base fuels, for instance as commercial and legislative pressures favour the use of increasing quantities of synthetically derived fuels. In the context of the present invention, "use" of a fuel component in a fuel composition means incorporating the component into the composition, typically as a blend (i.e. a physical mixture) with one or more other fuel components, conveniently before the composition is introduced into an engine . The fuel compositions to which the present invention relates have use in aviation engines, such as jet engines or aero diesel engines, but also in any other suitable power source. A base fuel may itself comprise a mixture of two or more different fuel components, and/or be additivated as described below.

The Diesel base fuel will typically have a boiling point within the usual Diesel range of 230 to 4000C, depending on grade and use. It will typically have a density from 775 to

840 kg/m3, preferably from 780 to 830 kg/m3, at 15°C (e.g. ASTM D4502 or IP 365) . It will typically have an initial boiling point in the range 230 to 2600C and a final boiling point in the range 350 to 4000C.

Its kinematic viscosity at -200C (ASTM D445) might suitably be from 1.2 to 8.0 mm2/s. It may be desirable for the composition to contain 5%v or greater, preferably 10%v or greater, or more preferably 25%v or greater, of the fuel component according to the invention.

The fuel composition or the fuel component as sole base fuel should be suitable for use as a Diesel fuel. Its components (or the majority, for instance 95%w or greater, thereof) should therefore have boiling points within the typical Diesel fuel range, i.e. from 230 to 4000C. The Diesel base fuel is preferably derived from derived from kerogen, and preferably has an initial boiling point in the range 230 to 260°C and a final boiling point in the range 380 to 400°C (as determined according to ASTM method D6730) .

Suitably, in accordance with the present invention, the Diesel fuel will consist of at least 80%w, preferably at least 83%w, more preferably at least 85%w, most preferably at least 89%w, of aliphatic hydrocarbons. Of these, preferably at least 30%w are naphthenic, i.e. cycloparaffinic components, the remainder preferably being composed of normal and iso-paraffins . It further preferably comprises of from 80 to 90 % by weight of aliphatic hydrocarbons. The ratio of iso-paraffins to n-paraffins is in the range of from 1:1 to: to 1: 0,7. The actual value for this ratio will be determined, in part, by the hydroconversion process used to prepare the Diesel from the kerogen, or the in-situ synthetic crude.

The aromatics content of the Diesel component, as determined by ASTM D4629, will typically be below 25%w, preferably below 20%w, and more preferably below 15%w, yet more preferably below 10%w, and more preferably below 9%w. The ratio of monoaromatic compounds to diaromatic compounds is preferably above 9.

The Diesel base fuel according to the present invention will typically have a density from 775 to 840 kg/m^ at 15°C; a kinematic viscosity from 1.2 to 6, preferably from 2 to 5, more preferably from 2 to 3.5, mm^/s at -200C; and a sulphur content of 20 ppmw (parts per million by weight) or less, preferably of 15 ppmw or less, yet more preferably 10 ppmw, 5 ppmw or 3 ppmw or less. The Diesel fuel component may itself be additivated

(additive-containing) or unadditivated (additive-free) . If additivated, e.g. at the refinery or in later stages of fuel distribution, it will contain minor amounts of one or more additives selected for example from anti-static agents (e.g. STADIS™ 450 (ex. Octel) ) , antioxidants (e.g. substituted tertiary butyl phenols), metal deactivator additives (e.g. N, N' -disalicylidene 1, 2-propanediamine) , fuel system ice improver additives (e.g. diethylene glycol monomethyl ether), corrosion inhibitor/lubricity improver additives (e.g. APOLLO™ PRI 19 (ex. Apollo), DCI 4A (ex. Octel), NALCO™ 5403 (ex. Nalco) ) , or thermal stability improving additives (e.g. APA 101™, (ex. Shell)) that are approved in international civil and/or military jet fuel specifications. Unless otherwise stated, the (active matter) concentration of each such additional component in the additivated fuel composition is at levels required or allowed in international jet fuel specifications.

In this specification, amounts (concentrations, %v, ppmw, wt%) of components are of active matter, i.e. exclusive of volatile solvents/diluent materials.

The present invention is particularly applicable where the fuel composition is used or intended to be used in a jet engine, a direct injection diesel engine, for example of the rotary pump, in-line pump, unit pump, electronic unit injector or common rail type, or in an indirect injection diesel engine. It may be of particular value for rotary pump engines, and in other diesel engines which rely on mechanical actuation of the fuel injectors and/or a low pressure pilot injection system. The fuel composition may be suitable for use in heavy and/or light duty diesel engines.

The present invention may lead to any of a number of advantageous effects, including good engine low temperature performance . Examples The present invention will now be described by way of example :

Example 1

A diesel range hydrocarbon material originating from kerogen converted in-situ in a pilot production field was employed as feed for the preparation of the Diesel base fuel. This material was fractioned from a full range shale oil pyrolysis product.

The properties of the feed are listed in Table 1.

Table 1. Analysis of Feed

Figure imgf000017_0001

The feed was subjected to a hydrotreatment in a hydrotreating microreactor pilot plant unit, by bringing the feed into contact with a catalyst in the presence of hydrogen and at elevated temperatures and pressure.

The catalyst bed was an 80/20 stacked bed of (a) a commercially available Ni-Mo on alumina hydrotreating catalyst that is usually employed for nitrogen removal, followed by (b) commercial high performance Co-Mo catalyst employed for sulphur removal. The catalysts were diluted in a 2:1 volume ratio with 120 mesh (125 micrometer) silicon carbide, i.e., 2.0 volumes of silicon carbide to 1.0 volume of catalyst. The catalyst bed was protected by a guard bed of against potential fouling due to particulates, asphaltenes, and/or metals present in the feed. This stacked bed configuration and the catalyst combination was employed to reduce both nitrogen and sulphur level of the diesel product to below specification of 15 ppmw for an Ultra Low Sulphur Diesel (ULSD) commercial product. The catalyst beds were activated by flowing a commercial vacuum as oil feedstock over the catalyst for 3 days at 650 0F.

The unit feed was then switched to the kerogene derived diesel feed and the operating conditions adjusted to the values set out below.

The product from the hydrotreating reactor was transported into a high pressure separator, where it was separated into a gaseous and a liquid stream. The liquid stream was subsequently sent to a stripper vessel, where nitrogen gas was bubbled through the liquid to remove any dissolved hydrogen sulfide and ammonia from the liquid. The stripped liquid was then collected in the unit product accumulator. The gas stream from the high pressure separator was combined with the gas stream from the stripper vessel. The flow rate of the combined gas stream was measured using a wet test meter, and the gas was analysed via chromatography. Hydrogen was added (treat rates expressed as SCF per barrel of feed) . Initial operations with the Diesel feed were conducted at 1,200 psig reactor pressure (15 psig = 103 kpa gauge) . Other operating conditions were reactor temperatures of 650 - 700 deg. F, liquid hourly space velocities (LHSV) of 0.5 - 1.0 1/hr, and hydrogen treat rates of 4,000 - 5,000 SCF/bbl (500 SCF/bbl = 99.8 standard m3/m3) . The reactor pressure was then increased to 1,500 psig, where performance data was obtained at the conditions of 675 deg. F reactor temperature, 0.5 1/hr LHSV, and 5,000 SCF/bbl. A sample of the thus obtained product was taken after removal of the gaseous compounds. Its properties are given in Table 2 below: Table 2: Properties of Intermediate Diesel Product (Feed for the dewaxing stage)

Figure imgf000019_0001

The dewaxing step (c) stage was performed using a dewaxing catalyst comprising Nickel on alumina in a microreactor . The catalyst was first sulphided by flow of commercial vacuum gas oil. Subsequently, the intermediate product was subsequently spiked with t-butyl amine (and dimethylsulfide for continued sulfidation of the catalytic dewaxing catalyst (a commercially available SDD-800 catalyst) at 1500 psig, 710-720 0F and 3.4 LHSV. The dewaxed total liquid product was then distilled into a lighter fraction, and a diesel fraction. The sulphur and nitrogen content of the total liquid product thus obtained were determined to be below 1 ppm. (see Table 3 and 4 for its properties) .

Table 3 Properties of the dewaxed diesel component

Figure imgf000020_0001

Table 4. Composition of dewaxed diesel

Figure imgf000021_0001

The thus obtained diesel fulfils all requirements for a ultra low sulphur diesel, including the cold flow properties (see Table 5) . It furthermore has a very low concentration of aromatic compounds, making the material a very safe diesel to handle . Table 5 - Test Results for Dewaxed ULSD

Figure imgf000022_0001

Table 5 (continued)

Figure imgf000023_0001

The resultant Diesel was found to be highly thermally stable.

Claims

C L A I M S
1. A process for the preparation of a middle distillate fuel from a kerogen pyrolysis product, comprising (a) hydrotreating the middle distillate fraction of a kerogen pyrolysis product;
(b) separating the product of step (a) into at least one or more lower boiling fractions and a gas oil precursor fraction; (c) catalytically dewaxing the gas oil precursor fraction obtained in step (b) ; and
(d) isolating the catalytically dewaxed gas oil or gas oil blending component from the product of step (c) by means of distillation .
2. A process according to claim 1, wherein in step (b) from the product of step (a) a gas oil-precursor fraction is isolated which has a T10wt% boiling point of between 200 and 450 0C and a T90wt% boiling point of between 400 and 550 0C.
3. A process according to claim 1 or claim 2, wherein the middle distillate fraction of step (a) is derived from the in-situ conversion of an oil shale reservoir.
4. A diesel base fuel obtainable according to the process according to claims 1 to 3, having an initial boiling point in the range 230 to 2600C and a final boiling point in the range 380 to 4000C (as determined according to ASTM method D6730), and comprising of from 80 to 90 % by weight of aliphatic hydrocarbons.
5. A diesel base fuel according to claim 4, wherein the ratio of monoaromatic compounds to diaromatic compounds is above 9,0.
6. A diesel base fuel according to any one of claims 4 to 5, wherein the ratio of iso-paraffins to n-paraffins is in the range of from 1:1 to: to 1: 0,7.
7. A diesel base fuel according to any one of claims 4 to 6, comprising less than 2% olefins.
8. A diesel base fuel according to any one of claims 4 to 7, having a cloud point of below -200C.
9. A fuel composition comprising said diesel base fuel component according to any one of claims 4 to 8 in the amount of 0.1 to 99.9%v, and further at least one additive an/or a further base fuel.
10. A method of operating a compression ignition (diesel) engine and/or an aircraft which is powered by one of more of said engines, which method involves introducing into said engine a fuel composition according to claim 9.
11. A process for the preparation of a fuel composition which process involves blending a petroleum derived diesel fuel with a diesel base fuel according to any one claims 4 to 9.
PCT/US2008/057236 2008-03-17 2008-03-17 Process for the preparation of middle distillates from kerogen WO2009116988A1 (en)

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