Process for manufacture of fuel

Abstract

The disclosure relates to a method for preparing sustainable aviation fuel, wherein the method comprises pretreating tall oil material; hydroprocessing said purified tall oil material using one or more catalysts and recovering an intermediate product; fractionating the intermediate product or a fraction thereof into sustainable aviation fuel boiling in the temperature range of 110 – 300 °C.

Description

[0001] PROCESS FOR MANUFACTURE OF FUEL

[0002] FIELD OF THE DISCLOSURE

[0003] The present disclosure relates to a method for preparing tail-oil material based sustainable aviation fuel (SAF) and more particularly to a method comprising pretreatment of a tall oil material, hydroprocessing the purified feedstock and fractionating the hydroprocessed intermediate product or a fraction thereof, in order to recover a hydrocarbon composition that can be used as kerosene as such or in a blend for aviation turbine fuel (jet fuel).

[0004] BACKGROUND OF THE DISCLOSURE

[0005] Biomass is increasingly recognized as a valuable feedstock to be used as a sustainable alternative for the production of hydrocarbons, which are suitable as fuels or fuel components. There is an increasing interest in alternative feedstocks for replacing at least partly crude oil, in the production of for example aviation fuel.

[0006] Fossil based aviation turbine fuels (Jet A-1 , Jet A) contain a complex mixture of hydrocarbons that have normally 8 to 16 hydrocarbon atoms. The aviation turbine fuels used need to fulfil strict requirements set for them before they can be sold. The most used aviation turbine fuel standard is ASTM D1655-23 Standard Specification for Aviation Turbine Fuels. This specification lists properties that need to be met including freezing point of less than -47 degrees of Celsius for Jet A-1 (ASTM D2386-19 / IP16-19), viscosity less than 8.0 mm2 / s in -20 degrees of Celsius (ASTM D455-23 / IP71 -20) and flash point less than 38 degrees of Celsius (ASTM D56-22). Renewable energy sources represent the potential fuel alternatives to overcome the global energy crises in a sustainable and eco-friendly manner. Sustainable Aviation Fuels (SAF) are a real alternative to fossil aviation fuels. Aviation is just as important for the energy transition as the transport sector and industry in reducing CO2emissions.

[0007] Biofuels and biochemicals are typically manufactured from feedstock originating from renewable sources, including oils and fats obtained from plants, animals, algal materials, fish and various waste streams, side streams and sewage sludge. These feedstocks, particularly the various waste streams and side streams, contain varying amounts of contaminants, such as gums, phospholipids and other phosphorus compounds, metals, and metal compounds, which are, for example, deleterious to converting catalysts. One of these sources is crude tall oil (CTO) obtained as a by-product of the kraft process of wood pulp manufacture. Crude tall oil is a mixture of components with different boiling points and thus a multistage process is usually needed in order to overcome the challenges of handling this complex feedstock in manufacturing processes. Despite the ongoing research and development of processes for processing biomass, especially crude tall oil, there is still a need to provide an improved process for converting biomass to aviation fuel or aviation fuel blending components.

[0008] BRIEF DESCRIPTION OF THE DISCLOSURE

[0009] An object of the present disclosure is to provide a method for preparing tail-oil material based sustainable aviation fuel (SAF) which fulfils the requirements for aviation turbine fuel of the ASTM D1655-23 standard.

[0010] The object of the disclosure is achieved by a method which is characterized by what is stated in the independent claim. The preferred embodiments of the disclosure are disclosed in the dependent claims.

[0011] The disclosure is based on the idea of producing SAF having similar properties as conventional jet fuel but with a smaller carbon footprint by pretreating tall oil material, hydroprocessing the purified feedstock and fractionating the hydroprocessed intermediate product or a fraction thereof, in order to recover a hydrocarbon composition that can be used as aviation turbine fuel as such or in aviation turbine fuel as part of a blend.

[0012] An advantage of the method of the disclosure is that the tail-oil material based sustainable aviation fuel prepared by the method fulfils the requirements for aviation turbine fuel of the ASTM D1655-23 standard. The similarity in physical and chemical properties provide the technical possibility to utilize the product produced by the method in high blend ratios with e.g., Jet A-1 kerosene fuel.

[0013] Sustainably produced aviation turbine fuels are produced from biological materials to lower the carbon footprint of the existing aviation transportation. The synthetic and renewable blending components used in aviation turbine fuels go through strict evaluation procedure before they can be used as blending components with the fossil-based jet fuels. In addition to the D1655-23 standard for conventional jet fuel, ASTM D7566-22a is the 'Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons' and describes the fuel quality specifications for each qualified SAF production pathway. These SAF components are typically used on the blend levels of 10 to 50 percent by volume, depending which approval path they have been gone through before added to the ASTM D7566-22a. Currently there are eight accepted sustainable aviation fuels that include e.g., Fischer-Tropsch hydroprocessed synthesized paraffinic kerosene and Synthesized paraffinic kerosene from hydroprocessed esters and fatty acids. The ASTM D7566-22a standard also lists the physical and chemical properties which the fuel component needs to fulfil before it is blended with the regular aviation turbine fuels. In future, biofuels and biochemicals may replenish the conventional non-renewable energy resources due to their renewability and several other advantages.

[0014] Another advantage of the method of the disclosure is that the tail-oil material based sustainable aviation fuel prepared can be used as such as aviation turbine fuel, since the sustainable aviation fuel prepared by the method of the disclosure fulfils the ASTM D1655- 23 standards requirements for aviation turbine fuel.

[0015] Fossil based aviation turbine fuels contain a complex mixture of hydrocarbons that normally have 8 to 16 hydrocarbon atoms. These include linear, branched, and cyclic paraffins as well as aromatic hydrocarbons. The i- and n-paraffins are the most desirable hydrocarbons as they offer the most desirable combustion cleanliness characteristics in jet fuels. Naphthenes (cycloparaffins) are the next preferred for this use. The olefins have good combustion characteristics but because of their poor thermal and gum stability their use in aviation turbine fuels is limited to less than 1 percent.

[0016] A further advantage of the sustainable aviation fuel prepared by the method of the disclosure is the high amount of n- and i-paraffins over 30 wt%. The high amount of naphthenes (cycloparaffins) over 25 wt% is also advantageous. Additionally, the Bromine Index value and low gum content (<1 mg / 100 ml) indicates that there are no olefins in the SAF produced by the method of the disclosure.

[0017] A further advantage of the sustainable aviation fuel prepared by the method of the disclosure is the good thermal stability properties. The thermal stability is one key parameter for aviation turbine fuels as the fuel, in addition to being fuel for the aircraft, also works as coolant in the aircraft. Therefore, deposit formation of poor-quality fuels would highly influence the operability of the aircraft.

[0018] An advantage of the method of the disclosure of the second alternative pretreatment, is that fatty acids separated in the first evaporator as part of the first fraction are still recovered as crude fatty acid in the first distilling column. Since more light components such as water, crude sulphate turpentine (CST), silicon components, light fatty acids and light neutrals are separated as the first fraction, these light components do not interfere the process of further evaporation of the second fraction. For example, the pressure is more easily maintained, and the evaporation(s) following the first evaporation takes place in a more controlled manner because low boiling light components do not cause so much “carry over”. When water and light components are first evaporated from the tall oil material in the first evaporation, the following evaporation(s) are more efficient. In addition to recovering a crude fatty acid fraction also other light components can be, if desired, refined further in another process or sold further as such.

[0019] A still further advantage of using three or more evaporators in any of the alternative pretreatments is that the second evaporator in the second evaporation can be a small and cheap evaporator that removes lighter components from the feed material. The following third evaporator can also be smaller and cheaper than the second evaporator in two-step evaporation. Consequently, for example a three-step evaporation unit can be cheaper than a two-step evaporation unit.

[0020] An advantage of the method of the disclosure of the first alternative pretreatment, is that the yield of purified material from the evaporation, especially from the four-step evaporation can be very high, up to 95%. The multi-step process enables the optimization of the evaporation conditions, and this enables the optimization of the process of the method of the disclosure and a high yield of sustainable aviation fuel.

[0021] A still further advantage of the method of the disclosure is that the amount of impurities in the sustainable aviation fuel are according to the standard.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In the following the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

[0024] Figure 1 shows a schematic flow diagram representing one embodiment of the method for preparing sustainable aviation fuel;

[0025] Figure 2 shows a schematic flow diagram representing another embodiment of the method for preparing sustainable aviation fuel;

[0026] Figure 3 shows the distillation properties of 100% sustainable aviation fuel prepared by the method of the disclosure and its 10% and 50% blends with Jet A-1 ;

[0027] Figure 4 shows the composition by mass percentages of one sustainable aviation fuel prepared by the method of the disclosure analysed with GC-VUV (ASTM D8369-21 ); and

[0028] Figure 5 shows the composition by mass percentages of one sustainable aviation fuel prepared by the method of the disclosure analysed with 2DGC-FID.

[0029] DETAILED DESCRIPTION OF THE DISCLOSURE

[0030] The disclosure relates to a method for preparing sustainable aviation fuel, wherein the method comprises pretreating tall oil material and recovering purified tall oil material; hydroprocessing said purified tall oil material using one or more catalysts and recovering an intermediate product; fractionating, typically by distillation, the intermediate product or a fraction thereof into sustainable aviation fuel boiling in the temperature range of 110 — 300 °C.

[0031] The pretreatment according to the disclosure is either done by (a1); evaporating tall oil material in a first evaporation step (A) at a temperature between 100 °C and 250 °C and at a pressure between 40 and 80 mbar to produce a first fraction comprising light hydrocarbons and water and a second fraction comprising fatty acids, resin acids, neutral substances and residue components,

[0032] (b1) evaporating said second fraction in a second evaporation step (B) and at least one further evaporation step to produce product fraction(s) comprising fatty acids and resin acids, and a residue fraction, and

[0033] (c1) recovering one or more of said product fraction(s) as purified tall oil material; or alternatively by

[0034] (a2) evaporating tall oil material in a first evaporator at a temperature between 255 °C and 295 °C and a pressure between 80 mbar and 220 mbar to obtain a first fraction comprising crude sulphate turpentine, light fatty acids, light neutrals, silicon compounds and water and a second fraction comprising fatty acids, resin acids, neutral substances and residue components;

[0035] (b2-1) evaporating said second fraction in a second evaporator at a temperature between 230 °C and 270 °C and a pressure between 5 mbar and 20 mbar to obtain a third fraction comprising fatty acids, resin acids and light neutral substances, and a first concentrate fraction; and evaporating said first concentrate fraction in a third evaporator at a temperature between 280 °C and 320 °C and a pressure between 5 and 20 mbar to produce a fourth fraction comprising fatty acids, resin acids and light neutral substances, and a residue fraction; or alternatively

[0036] (b2-2) evaporating said second fraction in a second evaporator at a temperature between 300 °C and 340 °C and a pressure between 3 and 10 mbar to obtain a third fraction comprising fatty acids, resin acids and neutral substances and a residue fraction;

[0037] (c2) distilling said first fraction in a first distilling column to obtain at least a crude fatty acid fraction;

[0038] (d2) distilling said third and said fourth fraction of step (b1 ) or said third fraction of step (b2) in a second distilling column to obtain at least a crude fatty acid fraction; and (e2) recovering a combined crude fatty acid fraction from said first distilling column and said second distilling column as purified tall oil material.

[0039] According to embodiments of the disclosure the method further comprises distilling the intermediate product of step (ii) into at least a diesel fraction distilled within the temperature range of 150 - 370 °C and optionally also into a naphtha fraction distilled within the temperature range of 30 - 210 °C, and thereafter distilling the sustainable aviation fuel from the diesel fraction in the fractionating of step. Typically, the diesel fraction has a cloud point between -10 °C and -34 °C and a cold filter plugging point (CFPP) between +5 °C and -20 °C.

[0040] The term “diesel” in the connection with the present disclosure refers to the product of the method of the disclosure distilling in the temperature range 150 - 370 °C. It is a mixture of hydrocarbons having C5 to C26 hydrocarbons.

[0041] The term “naphtha” in the connection with the present disclosure refers to the product of the method of the disclosure distilling in the temperature range 30 - 210 °C. It is a mixture of hydrocarbons having C5 to C12 hydrocarbons.

[0042] The term “sustainable aviation fuel” (SAF) in connection with the present disclosure refers to the kerosene prepared by the method of the disclosure boiling in the temperature range of 110 - 300 °C. It is a mixture of hydrocarbons having C6 to C16 hydrocarbons. Generally, both fossil-based aviation turbine fuels (Jet A-1 , Jet A) and sustainable aviation fuel (SAF), made from non-petroleum feedstocks, are kerosene. Both turbine-powered aircraft and aircraft with diesel engines require kerosene as a fuel. Typically, the kerosene fraction (Jet A-1 ) has a freezing point below -47 °C. Generally, the sustainability criteria of SAF relates to lifecycle carbon emissions reduction, limited fresh-water requirements, no competition with needed food production (like first generation biofuels) and no deforestation. The kerosene of the present disclosure is made from renewable biomass and waste resources, from non-petroleum feedstocks.

[0043] The term “tall oil material” in connection with the present disclosure refers to a by-product of Kraft pulping of wood, especially coniferous wood. The tall oil material is a sole crude tall oil, a mixture of different crude tall oils and / or a mixture of crude tall oil(s) and a different fatty acid feedstock, e.g., additional tall oil fatty acid or any other fatty acid of biological origin.

[0044] The term “crude tall oil” in connection with the present disclosure refers to the crude tall oil generated in the Kraft chemical pulping of trees for paper and other products. In a Kraft mill, wood chips are treated with a cooking liquor (or white liquor) containing sodium hydroxide and sodium sulphide to dissolve the lignin (delignification) of wood in order to produce pulp. Extractives in wood (resin acid, fatty acid, neutral and oxidized substances) react with the cooking liquor. After the cooking stage, residual used cooking liquor (now called weak black liquor) is separated from pulp during a washing step. This weak black liquor contains the valuable pulp cooking chemicals which are extracted from the liquor in the pulp mill recovery boiler before being re-used in the pulping process. On top this weak black liquor a floating layer of soap containing solid materials is formed.

[0045] This layer of soap has strong foaming properties and needs to be removed from the weak black liquor in order to allow the chemicals to be extracted in the recovery boiler. First, weak black liquor is evaporated to achieve a dry solids content of 30% for optimal removal of the soap layer and to allow combustion of the black liquor in the chemical’s recovery boiler. This evaporation results in strong black liquor, which is fed to the pulp mill recovery boiler. In the evaporation step the layer is soap is removed and now called Crude sulphate soap (CSS). CSS can either be burned as process fuel or further processed into crude tall oil. CSS further processing into CTO typically involves an acidulation process in which the CSS is treated with sulphuric acid in a reactor to split the sodium salts into free acids and sodium sulphate. The free acids form a layer of CTO on top of the aqueous phase, which contains the sodium sulphate and other impurities. Crude tall oil is mainly composed of both saturated and unsaturated oxygen-containing organic compounds such as unsaponifiable matter, neutral substances including sterols and esters, resin acids (mainly abietic acid and its isomers), fatty acids (mainly palmitic acid, linoleic acid, oleic acid and linolenic acid), fatty alcohols, and other alkyl hydrocarbon derivatives. The handling and cooking of the wood causes break down of the triglyceride structures and hence crude tall oil does not contain any significant amounts of triglycerides. Typically, crude tall oil contains some amounts of impurities such as inorganic sulphur compounds, sodium, potassium, calcium, magnesium, silicon, and phosphorus. The composition of the crude tall oil varies depending on the specific wood species.

[0046] The understanding of quality of crude tall oil depends on the end use. In addition to the amount of impurities, different qualities of crude tall oil typically depend on rosin acid content and total acid number (TAN) value, defined as milligrams of potassium hydroxide per gram (mgKOH / g) crude tall oil. The relative proportions of rosin acids and fatty acids are typically related. In general, the higher the rosin contents, the lower the unsaponifiables content and to some extent also the fatty acid content. Fuel quality crude tall oil typically contains a relatively high level of fatty acids (typically up to 65%), has a relatively low acid number value (typically <135 mgKOH / g) and low rosin acid content (typically <23%). The term “neutrals” in connection with the present disclosure refers to esters, unsaponifiables (monomeric neutrals such as sterols and alcohols) as well as polymeric neutrals (polymers).

[0047] The term “unsaponifiables” in connection with the present disclosure refers to substances which lack the ability to form soaps i.e., cannot be saponified by caustic treatment. Typical unsaponifiables are higher aliphatic alcohols, sterols, and hydrocarbons, particularly fatty alcohols (C20-C24), sterols (C30) and carotenes, and various other alkyl- and cycloalkyl hydrocarbon derivatives (C10-C30).

[0048] The term “evaporator” in connection with the present disclosure refers to a device where evaporation takes place. Evaporation is a unit operation thermally separating solutions based on component volatility. It takes advantage of vapor pressure differences of different components.

[0049] The term “distilling column” or “distillation column” in connection with the present disclosure refers to a device where distillation takes place. A typical distillation column comprises a vertical shell where the separation of liquid components is carried out, column internals such as trays or plates and / or packings which are used to enhance component separations, a reboiler to provide the necessary vaporisation for the distillation process, a condenser to cool and condense the vapour leaving the top of the column, a reflux drum to hold the condensed vapour from the top of the column so that liquid (reflux) can be recycled back to the column. Typically, the feed is introduced near the middle of the column to a tray known as the feed tray and the feed tray divides the column into a top (enriching or rectification) section and a bottom (stripping) section. The feed flows down the column where it is collected at the bottom in the reboiler. Heat is supplied to the reboiler to generate vapour. The source of heat input is normally steam. The vapour raised in the reboiler is reintroduced into the unit at the bottom of the column. The liquid removed from the reboiler is known as the bottom product or simply, bottoms. The vapour moves up the column and it is cooled by a condenser when it exits the top of the unit. Typically, the condensed liquid is stored in a holding vessel known as the reflux drum and some of this liquid is recycled back to the top of the column and this is called the reflux. The condensed liquid that is removed from the system is known as the distillate or top product.

[0050] Feedstock

[0051] In embodiments of the disclosure the tall oil material used as feedstock is a sole crude tall oil, a mixture of different crude tall oils or a mixture of crude tall oil(s) and a different fatty acid feedstock(s). The fatty acid feedstock(s) is not crude tall oil and is typically chosen from one or more of tall oil fatty acid and any other fatty acids of biological origin.

[0052] Preferably the tall oil material comprises low-quality crude tall oil, typically the crude tall oil comprises less than 500 ppm impurities, preferably 10 - 250 ppm, more preferably 10 - 100 ppm, most preferably 10 - 50 ppm impurities. Typically, the impurities are the total amount of restricted metals critical for catalysts (including Ca, Fe, K, Mg, Na, As), optionally together with the amounts of silicon and / or phosphor, all measured by X-ray fluorescence spectrometry (XRF) or by inductively coupled plasma optical emission spectrometry (Xylene / ICP-OES, ASTM D5185-18). The feedstock of the embodiments of the disclosure either comprises tall oil material feedstock or consists of tall oil material feedstock, preferably the tall oil material is the sole feedstock. The tall oil material may also partly comprise crude tall oil which has been slightly purified or modified for example in a falling film evaporator, centrifuge and / or decanter centrifuge, however crude tall oil or mixtures of crude tall oil are preferred. The amount of resin acids, fatty acids, neutrals and acid number of some crude tall oils is shown in Table 1 . Examples of typical amounts of impurities in crude tall oil are shown in Table 2.

[0053] Table 1 Examples of crude tall oil

[0054] Table 1 , cont. Examples of crude tall oil Table 2 Amounts of impurities in crude tall oil (ppm)

[0055] Table 2, cont. Amounts of impurities in crude tall oil (ppm) Pretreatment

[0056] The feedstock may be purified by evaporation, typically in at least three evaporation steps. In an embodiment, where three evaporation steps are employed, the first evaporator is operating at 100 - 250 °C and 40 - 80 mbar, the second evaporator operating at 200 - 280 °C and approximately 3 - 15 mbar, and the third evaporator operating at 250 - 370 °C and approximately 0.1 - 5 mbar. In further embodiments, where four evaporation steps are employed, the first evaporator is operating at 100 - 250 °C and 30 - 90 mbar, the second evaporator is operating at 150 - 250 °C and approximately 20 - 80 mbar, the third evaporator is operating at 200 - 320 °C and approximately 3-20 mbar, and a fourth evaporator is operating at 280 - 380 °C and approximately 0.1 - 10 mbar. In still further embodiments, where four evaporation steps are employed, the first evaporator is operating at 100 - 250 °C and 70 - 90 mbar, the second evaporator is operating at 180 - 230 °C and approximately 20 - 60 mbar, the third evaporator is operating at 220 - 270 °C and approximately 3-15 mbar, and a fourth evaporator is operating at 320 - 370 °C and approximately 0.1 - 5 mbar. These embodiments are particularly suited to the purification of crude tall oil. The concentrate fraction of the first evaporator is fed to the second evaporator, and the concentrate of the second evaporator is fed to the third evaporator and the condensates of the third and fourth evaporator are recovered as product fractions. The use of an initial evaporation step enables boiling in the subsequent step(s) to be performed in a controlled manner since low boiling compounds are removed in the first step. Turpentine can be recovered from the light fractions removed from the first and second evaporation steps.

[0057] In case more than one further evaporation step is used, the purified tall oil material is one or more of the condensate fraction(s) of the evaporator(s) of the further evaporation step(s), and the residue fraction is the residue fraction of the last evaporator. Typically, this pretreatment consists of four evaporation steps i.e., a first evaporation step, a second evaporation step and two further evaporation steps. Typically, in the method of the disclosure the evaporating in step (b1) comprises a second evaporation step and at least two further evaporation steps.

[0058] In some embodiments of the method of the disclosure, the process further comprises an additional pretreatment step of storing the tall oil material in a storage tank before the first evaporator.

[0059] According to an embodiment of the disclosure where the first alternative pretreatment is used, tall oil material is purified by

[0060] (a1); evaporating tall oil material in a first evaporation step at a temperature between 100 °C and 250 °C to produce a first fraction comprising light hydrocarbons and water and a second fraction comprising fatty acids, resin acids, neutral substances, and residue components,

[0061] (b1) evaporating said second fraction in a second evaporation step (B) and at least one further evaporation step to produce product fraction(s) comprising fatty acids and resin acids and a residue fraction, and (c1) recovering said product fraction as purified tall oil material.

[0062] According to the embodiments of the disclosure, the first evaporator is typically a fallingfilm evaporator or a thin film evaporator. The second evaporator is preferably a thin film evaporator or short path evaporator. The third evaporator and the optional further evaporator(s) are typically, independently from each other, thin film evaporator(s) or short path evaporator(s). The evaporators can be either of the same type or different type. Typically, the evaporating in the process of the disclosure is performed with any commercially available suitable evaporators. Preferably the evaporating is performed in an evaporator selected from the group defined above. Examples of suitable evaporation methods are typically those utilizing thin film evaporation technology. Suitable combinations for evaporators (in this order) in the evaporation unit are:

[0063] For three stage evaporation:

[0064] TF + SP + SP

[0065] FF + TF + TF

[0066] FF + TF + SP

[0067] For four stage evaporation:

[0068] FF + TF + SP + SP

[0069] FF + TF + TF + TF

[0070] FF + TF + TF + SP where

[0071] FF = falling film evaporator

[0072] TF = thin film evaporator

[0073] SP = short path evaporator

[0074] The reaction time of a single evaporation, or the residence time for every separate evaporator in case this step is part of a continuous process, is typically 12 - 120 seconds, not including the heating time.

[0075] Alternative pretreatment

[0076] The second alternative pretreatment of the method of the disclosure comprises evaporating tall oil material in a multistage evaporation, comprising two or three evaporators and utilizing two distilling columns. Examples of suitable evaporation methods are typically those utilizing thin film evaporation technology. The evaporators in the evaporation methods can thus be selected from the group consisting of thin film evaporators, falling film evaporators, short path evaporators, and any other evaporators using thin film evaporation technology. The evaporators can be either of the same type or different type and are selected independently from the above listed evaporators.

[0077] Typically, the method of treating the feedstock comprising tall oil material comprises the following steps

[0078] (a2) evaporating tall oil material in a first evaporator at a temperature between 255 °C and 295 °C and a pressure between 80 and 220 mbar to obtain a first fraction comprising crude sulphate turpentine, light fatty acids, light neutrals, silicon compounds and water and a second fraction comprising fatty acids, resin acids, neutral substances and residue components;

[0079] (b2-1) evaporating said second fraction in a second evaporator at a temperature between 230 and 270 °C and a pressure between 5 and 20 mbar to obtain a third fraction comprising fatty acids, resin acids and light neutral substances, and a first concentrate fraction; and evaporating said first concentrate fraction in a third evaporator at a temperature between 280 and 320 °C and a pressure between 5 and 20 mbar to produce a fourth fraction comprising fatty acids, resin acids and light neutral substances, and a residue fraction; or alternatively

[0080] (b2-2) evaporating said second fraction in a second evaporator at a temperature between 300 and 340 °C and a pressure between 3 and 10 mbar to obtain a third fraction comprising fatty acids, resin acids and neutral substances and a residue fraction;

[0081] (c2) distilling said first fraction in a first distilling column to obtain at least a crude fatty acid fraction;

[0082] (d2) distilling said third and said fourth fraction of step (b1 ) or said third fraction of step (b2) in a second distilling column to obtain at least a crude fatty acid fraction; and

[0083] (e2) recovering a combined crude fatty acid fraction from said first distilling column and said second distilling column as purified tall oil material.

[0084] In the method of the disclosure a first evaporator is used for separating a first fraction typically comprising crude sulphate turpentine, light fatty acids, light neutrals, silicon components and water and a second fraction comprising fatty acids, resin acids, neutral substances and residue components. The first fraction is distilled in a first distilling column.

[0085] One or two further evaporator(s) are used for separating a residue fraction, typically called tall oil pitch (TOP) or TOP Fuel, from the second fraction separated in the first evaporator. The third and fourth fractions or a sole third fraction, is used as feed for the second distilling column. If only one additional evaporator, a second evaporator, is used, only a third fraction is used as feed in the second distilling column. If a second and third evaporator is used, the feed to the second distilling column consists of a third and fourth fraction. The size of the second and third evaporator is typically adjusted so that the feed (feed fraction) to the second distilling column consists of 40 - 70 wt% of said third fraction and 30 - 60 wt% said fourth fraction, preferably about 45 - 60 wt% of said third fraction and about 40 - 55 wt% of said fourth fraction. In some embodiments of the method of the disclosure, the process further comprises an additional pretreatment step of storing the tall oil material in a storage tank before the first evaporator.

[0086] In embodiments of the disclosure the amount of metals of the combined crude fatty acid fraction, especially the amount of restricted metals (including (Ca), iron (Fe), potassium (K), magnesium (Mg), sodium (Na) and arsenic (As)) measured by X-ray fluorescence spectrometry (XRF) or by inductively coupled plasma optical emission spectrometry (Xylene / ICP-OES, ASTM D5185-18), is typically below 20 ppm, preferably below 10 ppm, more preferably below 5 ppm, most preferably below 3 ppm, including the amount being between two of the following amounts: 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 , 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 , 0.5, 0.4, 0.3, 0.2, 0.1 and 0 ppm, typically between 0.1 and 20 ppm, preferably between 0.2 and 15 ppm, more preferably between 0.5 and 5 ppm and most preferably between 0.5 and 3 ppm. For the restricted metals the total amount of calcium Ca, Fe, K, Mg, Na and As (ppm) of the combined crude fatty acid fraction is measured. Further, amounts of single impurities can also be measured by XRF or by Xylene / ICP-OES. The amount of phosphorous of the combined crude fatty acid fraction, measured by XRF or by Xylene / ICP-OES, is typically below 5 ppm, preferably below 2 ppm, more preferably below 1 ppm, most preferably below 0.5 ppm, including the amount being between two of the following amounts: 5, 4, 3, 2, 1 , 0.5, 0.4, 0.3, 0.2, 0.1 and 0 ppm. Further, the amount of silicon (Si) of the combined crude fatty acid fraction, measured by XRF or by Xylene / ICP- OES, is typically below 15 ppm, preferably below 5 ppm, more preferably below 3 ppm, most preferably below 2 ppm, including the amount being between two of the following amounts: 15, 14, 13, 12, 11 , 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 , 0.5, 0.4, 0.3, 0.2, 0.1 and 0 ppm, typically between 0.1 and 10 ppm, preferably between 0.2 and 5 ppm and more preferably between 0.5 and 2 ppm.

[0087] According to the embodiments of the disclosure, the first evaporator is typically a falling film evaporator or a thin film evaporator or a short path evaporator, preferably a falling film evaporator or thin film evaporator. In order to obtain a suitable amount of first fraction, the temperature of the first evaporation is adjusted to a temperature selected from between 255 °C and 295 °C, preferably evaporating tall oil material in said first evaporator is done at a temperature between 260 °C and 290 °C, more preferably between 270 °C and 280 °C, including the temperature being a temperature between two of the following temperatures; 255 °C, 260 °C, 270 °C, 280 °C, 290 °C and 295 °C at a pressure selected from between 80 to 220 mbar, preferably between 90 and 210 mbar, more preferably between 100 and 200 mbar, most preferably between 120 and 180 mbar.

[0088] According to the embodiments of the disclosure where three evaporators are used, the temperature of the second evaporation is adjusted to a temperature selected from between 230 °C and 270 °C, preferably evaporating the second fraction obtained from the first evaporator in a second evaporator is done at a temperature between 235 and 265 °C, preferably between 240 and 260 °C, more preferably between 245 and 255 °C, including the temperature being a temperature between two of the following temperatures; 230 °C, 235 °C, 240 °C, 245 °C, 250 °C, 255 °C, 260 °C, 265 °C and 270 °C and / or at a pressure between 5 and 20 mbar, preferably between 6 and 18 mbar, more preferably between 8 and 15 mbar, most preferably between 10 and 12 mbar. Typically, the condensate or vapour retrieved from the second evaporation is ready to be fed to the second distilling column and the concentrate is fed to a third evaporator. The third evaporation temperature is adjusted to a temperature selected from between 280 °C and 320 °C, preferably between 285 and 315 °C, more preferably between 290 and 310 °C, most preferably between 295 and 305 °C, including the temperature being a temperature between two of the following temperatures; 280 °C, 285 °C, 290 °C, 295 °C, 300 °C, 305 °C, 310 °C, 315 °C and 320 °C and / or at a pressure selected from between 3 to 15 mbar, preferably between 5 and 12 mbar and more preferably between 8 and 10 mbar. Typically, the condensate or vapour of the third evaporator is fed to the second distilling column together with the condensate or vapour of the second evaporator. If one of the third or fourth fraction is condensate and the other is vapour, the fractions are typically fed separately to the second distilling column.

[0089] According to the embodiments of the disclosure where two evaporators are used, the temperature of the second evaporation is higher than the temperature in the second evaporator of the embodiment utilizing three evaporators. In the two evaporator embodiment the temperature of the second evaporator is adjusted to a temperature selected from between 300°C and 340°C, preferably evaporating the second fraction obtained from the first evaporator in a second evaporator is done at a temperature between 310 and 330 °C, more preferably between 315 and 320 °C, including the temperature being a temperature between two of the following temperatures; 300 °C, 305 °C, 310 °C, 315 °C, 320 °C, 325 °C, 330 °C, 335 °C and 340 °C and / or at a pressure between 3 and 10 mbar, preferably 5 to 12 mbar, more preferably between 8 and 10 mbar.

[0090] The second evaporator and the optional third evaporator are typically, independently from each other, a thin film evaporator or short path evaporator. The evaporators can be either of the same type or different type and are selected the above listed evaporators. Preferably the second evaporator is a short path evaporator, and the third evaporator is a short path evaporator. Typically, the evaporating in the process of the disclosure is performed with any commercially available suitable evaporators. Preferably the evaporating is performed in an evaporator selected from the group defined above. In an especially preferred embodiment of the disclosure, the evaporation is performed by evaporation using thin film evaporation. Suitable combinations for evaporators (in this order) in the evaporation unit are:

[0091] For two stage evaporation:

[0092] TF + SP

[0093] TF + TF

[0094] SP + SPF or three stage evaporation:

[0095] FF + TF + SP

[0096] TF + TF + SP

[0097] TF + SP + SP

[0098] SP + SP + SP

[0099] TF + TF + TF

[0100] FF + TF + TF where

[0101] FF = falling film evaporator

[0102] TF = thin film evaporator

[0103] SP = short path evaporator

[0104] The reaction time of a single evaporation, or the residence time for every separate evaporator in case this step is part of a continuous process, is typically 12 - 120 seconds, not including the heating time. According to the embodiments of the disclosure, the temperature of the first distilling column is adjusted to a temperature selected from between 130°C and 170°C, preferably distilling the first fraction of the first evaporator is done at a temperature between 140 °C 160 °C, more preferably between 145 °C and 155 °C, including the temperature being a temperature between two of the following temperatures; 130 °C, 135 °C, 140 °C, 145 °C, 150 °C, 155 °C, 160 °C, 165 °C and 170 °C and / or at a pressure selected from between 30 to 70 mbar, preferably between 40 and 60 mbar.

[0105] According to the embodiments of the disclosure, the temperature of the second distilling column is adjusted to a temperature selected from between 260 °C and 300 °C, preferably distilling condensate(s) or vapour(s) of the second evaporator and optionally third evaporator is done at a temperature between 270 °C and 290 °C, more preferably between 275 °C and 285 °C, including the temperature being a temperature between two of the following temperatures; 260 °C, 265 °C, 270 °C, 275 °C, 280 °C, 285 °C, 290 °C, 295 °C and 300 °C and / or at a pressure selected from between 3 to 8 mbar, preferably between 4 and 7 mbar, more preferably between 5 and 6 mbar.

[0106] The reaction time of the first distilling column, or the residence time in case this distillation is part of a continuous process, is typically 1 - 2 hours not including the heating time.

[0107] The reaction time of the second distilling column, or the residence time in case this distillation is part of a continuous process, is typically 2 - 4 hours not including the heating time.

[0108] Hydroprocessing

[0109] Prior to hydroprocessing, the feedstock may be passed through one or more guard units together with hydrogen in order to remove hazardous substances such as metal residues, thereby protecting the hydroprocessing catalysts from poisoning and fouling. Typically, the method of the disclosure comprises one or more guard unit(s), wherein the guard unit(s) are separate from the hydroprocessing reactor(s), or included upstream of the hydroprocessing catalyst bed(s) in the same reactor(s)

[0110] In the embodiments of the disclosure, the purified tall oil material, for example the recovered fraction(s) after several evaporation(s) or the recovered combined crude fatty acid fraction of the alternative pretreatment, may be subjected to a catalytic hydroprocessing step carried out in the presence of hydrogen, to yield an hydroprocessed intermediate product, which may be subjected to a one or more fractionation(s) for providing sustainable aviation fuel and optionally other liquid fuels and / or chemicals. The hydroprocessing step may be carried out for effecting at least one of hydrodeoxygenation, hydrodewaxing, hydroisomerization, hydrocracking, hydrodearomatization and ring opening reactions.

[0111] Hydroprocessing is performed using one hydroprocessing reactor or using two or more reactors (i.e., separate pressure vessels). In the case that a plurality of hydroprocessing reactors are employed, the reactors can be connected in series so that the product of one reactor is fed to another reactor. Each reactor can contain a single “bed” comprising one or more catalysts and optionally other materials such as an inert material (e.g. for temperature control). Alternatively, any given reactor may contain a plurality of catalyst beds which each contain one or more catalysts and optionally other materials such as an inert material. Examples of the inert material include alumina, silicon carbide and glass beads.

[0112] Reactors containing more than one catalyst bed can comprise a quench gas inlet and a distributer between any two catalyst beds.

[0113] Hydroprocessing may be performed using one or more hydroprocessing catalysts comprising one or more metals selected from Group VIA and Group VIII metals (Periodic Table of Elements). Particularly useful examples are Mo, W, Co, Ni, Pt and Pd. The catalyst(s) can also contain one or more support materials, for example zeolite, alumina (AI2O3), gamma-alumina, zeolite-alumina, alumina-silica (SiO2), ZrO2, alumina-silica- zeolite and activated carbon. Typically, the hydroprocessing step is performed using one or more reactors which each comprise catalysts comprising one or more metals selected from Group VIA and Group VIII metals, preferably a mixture of CoO and MoOs (C0M0) and / or a mixture of NiO and MoO3(NiMo), and / or a mixture of Ni, Mo and Co and / or NiW and one or more support materials selected from zeolite, alumina, silica, zeolite-alumina, alumina-silica, alumina-silica-zeolite and activated carbon. Also, noble metals, such as Pt and / or Pd dispersed on gamma-alumina may be used.

[0114] In embodiments of the disclosure, the hydroprocessing is carried out under a pressure of 5 - 300 bar (total pressure, abs). In an embodiment, the pressure in the hydroprocessing is from 30 to 250 bar, preferably from 30 to 120 bar.

[0115] In embodiments of the disclosure, hydrogen partial pressure is maintained in the range from 50 to 250 bar, preferably from 80 to 200 bar, more preferably from 80 to 110 bar.

[0116] The hydroprocessing is carried out at a temperature in the range of 100 to 450 °C, preferably 280 °C to 450 °C, more preferably from 350 °C to 400 °C. The hydroprocessing feed rate WHSV (weight hourly spatial velocity) of the feedstock oil is proportional to an amount of the catalyst. The WHSV of the feed material varies between 0.1 and 10, it is preferably in the range of 0.1- 5 and more preferably in the range of 0.3 - 0.7.

[0117] The ratio of H2 / feed varies between 600 and 4000 Nl / I, preferably of 1300-2200 Nl / I.

[0118] The feed is pumped to the hydroprocessing reactor at a desired speed. Suitably the feed rate LHSV (liquid hourly space velocity) of the feed material is in the range of 0.01 -10 h-1 , preferably 0.1 - 5 h-1.

[0119] Fractionation

[0120] The hydroprocessed composition can be cooled and light gaseous compounds such as water, hydrogen, hydrogen sulphide, carbon monoxide and carbon dioxide can be removed from the composition as a gas phase. The removed gases can be passed through an amine scrubber in order to separate hydrogen sulphide and carbon dioxide from the remaining gases. Hydrogen can be separated and reused as quench gas in the hydroprocessing reactor.

[0121] The sustainable aviation fuel prepared by the method of the disclosure is isolated by fractionation of the hydroprocessed intermediate product or a fraction thereof, preferably following the removal of gas phase, preferably in a phase separator, wherein the gas phase is removed directly after the hydroprocessing of step (ii). The gas phase can be recycled back to the hydrotreatment. According to standard ASTM D1655-23, the sustainable aviation fuel is distilled to fulfil the following requirements: initial boiling point: no limit, 10% V / V recovery: maximum 205.0 °C, and final boiling point: maximum 300.0 °C. Distillation residue can be maximum of 1 .5% V / V and distillation loss: maximum 1 .5% V / V. Typically, the sustainable aviation fuel prepared by the method of the present disclosure is distilled in the temperature range of 110 °C - 270 °C in a conventional distilling column at Atmospheric Equivalent Temperature (AET).

[0122] The sustainable aviation fuel obtained by the method of the disclosure is either used as such (100 %) or it can be blended with one or more other aviation fuel(s), preferably other kerosene(s). Particularly suitable example of the other fuel is Jet A-1 kerosene. Fuel blends can contain the composition in various amounts. Preferably, the sustainable aviation fuel of the method of the disclosure is contained in a fuel blend in an amount of 1- 99 vol.% based on the volume of the blend. In embodiments of the disclosure the sustainable aviation fuel prepared by the method of the disclosure typically comprises over 30 wt% of n- and i-paraffins, more preferably over 40 wt% of n- and i-paraffins, and most preferably over 50 wt% of n- and i-paraffins.

[0123] In embodiments of the disclosure the sustainable aviation fuel prepared by the method of the disclosure typically comprises over 25 wt% of cycloalkanes, more preferably over 28 wt% of cycloalkanes, and most preferably over 50 wt% of cycloalkanes.

[0124] In embodiments of the disclosure the sustainable aviation fuel prepared by the method of the disclosure typically comprises over 8 wt% of aromatic hydrocarbons. Typically, over 98 wt% of the total aromatic hydrocarbons are monoaromatic hydrocarbons.

[0125] The n- and i-paraffins, the cycloalkanes and the aromatic hydrocarbons are typically detected by two-dimensional gas chromatography according to the internal methods, ASG 2253 (GCxGC-TOFMS) and ASG 2502 (GCxGC-FID). The application of (GCxGC-FID) provides a complete quantitative overview of the composition and can replace with only one measurement the standard methods DIN EN 12916, DIN EN 14103 and DIN EN 14078. Alternatively, the hydrocarbons are detected by GC-VUV (ASTM D8369-21 ) or the standard methods mentioned above.

[0126] In Figure 1 tall oil material 10 is fed to a first evaporation step A. A first fraction 1 comprising light compounds such as water and short chain hydrocarbons is removed, and the concentrate fraction 3 of the first evaporator A comprising fatty acids, resin acids, neutral substances and residue components, such as pitch and metals, is fed to a second evaporation step B. The liquid fraction 3’ recovered from the second evaporator B comprising fatty acids, resin acids, neutral substances and residue components is fed to the third evaporator C and the liquid fraction 3” recovered from evaporation step C is fed to the fourth evaporation step D. The condensate fractions 4, 4’comprising fatty acids, resin acids and light neutral substances of the further evaporation steps C and D are recovered as product fractions. One or more of the product fractions are recovered as purified tall oil material 40. A residue fraction 6 is recovered after the last evaporation step. Turpentine is optionally recovered from fractions 1 and 2 removed from evaporation steps A and B. Volatiles are optionally removed form evaporation steps C 5 and D 5’. The purified tall oil material 40 is fed to hydroprocessing 400. The hydroprocessed intermediate product 50 obtained is fed to a distilling column 500’ and a diesel fraction 8 and optionally one or more other fractions (not shown) is recovered. A sustainable aviation fuel 60 and optionally one or more other fractions (not shown) are recovered from a further distilling column 500. In Figure 2 tall oil material 10 is fed to a first evaporator 100. A first fraction 11 is fed to a first distilling column 200 and a second fraction 12 is fed to a second evaporator 110. A crude fatty acid fraction 20 as well as optionally other fractions such as water, crude sulphate turpentine 21 , 22 are recovered from the first distilling column 200. The concentrate fraction 14 of the second evaporator 110 is fed to a third evaporator 120 and a residue fraction 15 and a fourth fraction 16 are recovered. The third fraction 13 obtained from the second evaporator and the fourth fraction 16 obtained from the third evaporator are fed to a second distilling column 300. A crude fatty acid fraction 30 as well as optionally other fractions such as a tall oil rosin pitch fraction 31 and a tall oil rosin fraction 32 are recovered from the second distilling column 300. The crude fatty acid fraction 20 from the first distilling column 200 and the crude fatty acid fraction 30 from the second distilling column 300 are combined and a combined crude fatty acid fraction 40 is recovered as a purified tall oil material 40. The purified tall oil material 40 is fed to hydroprocessing 400 comprising one or more hydroprocessing reactors (not shown). The hydroprocessed intermediate product 50 obtained is fed to a distilling column 500. A sustainable aviation fuel 60 and optionally one or more other fractions 61 , 62 are recovered from the distilling column 500.

[0127] According to embodiments of the disclosure the method, or parts thereof, can be a continuous, batch or semi-batch process.

[0128] EXAMPLES

[0129] Example 1 CTO purification and hydrogenation

[0130] A sustainable aviation fuel was produced by subjecting crude tall oil (CTO) to a purification pretreatment and hydroprocessing treatment according to Figure 1. The crude tall oil originated from kraft pulping of a mixture of northern softwood (pine and spruce) and birch. The crude tall oil contained 51 wt% of fatty acids, 26 wt% of resin acids and 23 wt% of neutral compounds.

[0131] The crude tall oil was purified by four-step evaporation to remove 1 wt% turpentine and light fraction and 10% of the oil as a heavy pitch fraction. The purified tall oil (PTO) was fed into a reactor system together with hydrogen under pressure. The reactor system contained commercially available sulfided catalysts. The main reactions taking place in the reactors are removal of heteroatoms, saturation of double bonds and isomerization. The reactors were operated at high pressures, up to 100 bar, at high temperatures, up to 400 °C in the presence of excess hydrogen, up-to H2 / CTO feed rate (Nl / I) 1500. The total hydrogenated product consisted of a mixture of linear, isomeric and cyclic hydrocarbons and also some aromatic compounds. The carbon distribution was from C5 to C25+. This product was then distilled into a naphtha fraction distilling in the temperature range of 30 - 210 °C and a diesel fraction distilling in the temperature range of 150 - 370 °C.

[0132] Example 2 Preparation of sustainable aviation fuel

[0133] The diesel fraction of Example 1 was distilled in a distillation unit, where a fraction boiling in the temperature range of 110 - 270 °C was collected. The diesel used for the fractionation had cloud point of -8.4 °C and CFPP -11 °C.

[0134] The distillation was carried out at a cut point of 270 °C, which was selected to achieve a carbon number range of C6 to C16 for the sustainable aviation fuel of the purified tall oil (Tall Oil-SAF). This carbon number range ensured that the Tall Oil-SAF had adequate fluidity properties, such as viscosity and freezing point, for blending with Jet A-1 kerosene. The yield for Tall Oil-SAF fraction was 20 - 30 wt%. The distillation residue was 70 - 80 wt%, essentially consisting of hydrocarbons having a carbon number higher than C17.

[0135] Example 3 Characteristics of Tall Oil-SAF and its blends

[0136] The Tall Oil-SAF alone and its 10% and 50% blends with Jet A-1 were compared with those of Jet A-1 kerosene. The results of the physical properties shown in Tables 3-5 and Figure 3, indicate that Tall Oil-SAF have similar properties to those of Jet A-1 kerosene.

[0137] The cetane number of Tall Oil-SAF and its blends were measured by both indicated cetane number (ICN) and derived cetane number (DCN) methods, and the results were consistent. It should be noted that the Tall Oil-SAF did not contain any additives, and the improvements in some properties of the blends (such as electrical conductivity) were due to the additives or the characteristics of Jet A-1 .

[0138] The lubricity (BOCLE) values for Tall Oil-SAF and its blends with Jet A-1 were better than expected for such low sulphur kerosene components as no additives were added before the testing. The corrosion inhibitors and lubricity improvers as additives improve this property but was not used in the Tall Oil-SAF. The good lubricity characteristics of Tall Oil- SAF can be explained with the aromatic content. The aromatic hydrocarbons have poor combustion characteristics, but when synthetized fuels contain minimum of 8.0 wt% of aromatic hydrocarbons, this prevents the aged elastomer shrinkage and prevents associated leakage of fuels. Therefore, the Tall Oil-SAF’s naturally occurring aromatic content lowers the risk of fuel leakages when used as blending component with Jet A or Jet A-1 turbine fuels. Table 3. Physical properties of the Tall Oil-SAF and its blends with Jet A-1

[0139] The thermal stability was tested at 260 °C and 325 °C. Results presented in Table 4, demonstrate a good thermal stability for Tall Oil-SAF. Table 4. Thermal stability of Tall Oil-SAF and its blends with Jet A-1

[0140] The distillation properties of the composition are shown in Table 5, wherein the IBP is the initial boiling point and FBP is the final boiling point. Figure 3 illustrates the distillation properties of 100% Tall Oil-SAF and its 10% and 50% blends with Jet A-1 . As can be seen the distillation curves are between the min-max distillation curves that are set for the Jet A-1.

[0141] Table 5. Distillation (ASTM D86:23) results for Tall Oil-SAF and its blends with Jet A-1

[0142] The chemical properties of Tall Oil-SAF and its blends were evaluated.

[0143] The aromatic compounds in Tall Oil-SAF and its blends with Jet A-1 were measured with various methods and the results are presented in Table 6. The results showed that Tall Oil-SAF contains mainly monoaromatics with trace amounts of diaromatics. Tri- and polyaromatics were not detected.

[0144] Table 6. Aromatic composition of Tall Oil-SAF and its blends with Jet A-1 . Table 6. cont. Aromatic composition of Tall Oil-SAF and its blends with Jet A-1 .

[0145] Table 7 shows several chemical properties. The values measured for Tall Oil-SAF and its blends in Jet A-1 fulfil the limits required by D1655-23. The Bromine Index is measured to determine the presence of any possible residual olefins in the fuel and its blends with Jet A-1.

[0146] The low Bromine Index and gum content measured for Tall Oil-SAF indicates that the hydrogenation has been efficient and there are only trace amounts of olefins left in the fuel. The Tall Oil-SAF has a low sulphur content (1.4 mg / kg) that also lowers total sulphur content of the blend. In the combustion process sulphur oxides are formed that may be corrosive to turbine metal parts. Therefore, the usage of Tall Oil-SAF decreases the risk of unwanted corrosion in turbine engines.

[0147] Table 7. Chemical properties of Tall Oil-SAF and its blends with Jet A-1 . The trace contaminants in the fuel and its blends with Jet A-1 were analysed. The results are shown in Table 8. The analysis revealed that the fuel and its blends had trace metal and halogen levels below the required threshold, except for phosphorous (0.6 mg / kg). Table 8. Trace metals in Tall Oil-SAF and its blends in Jet A-1 .

[0148] Tall Oil-SAF was analysed with GC-VUV (Gas Chromatography with Vacuum Ultraviolet Absorption Spectroscopy Detection, ASTM D8369-21 ), and Table 9 shows the amounts of the various components of the distillate. Figure 4 shows the Tall Oil-SAF composition by mass percentages. The Tall Oil-SAF is mainly paraffinic, the paraffins being n-, iso- and cyclic paraffins.

[0149] PTO contains resin acids and neutrals substances with ring structures and these result in the aromatic and naphthene compounds in the Tall Oil-SAF product. Measured olefin content in the Tall Oil-SAF was 2.9% with GC-VUV method. This result is in contradiction with the good thermal stability of the Tall Oil-SAF (Table 4). Additionally, the Bromine Index value and low gum content (< 1 mg / 100 ml, Table 7) indicates that there are no olefins in the Tall Oil-SAF. The olefin content analytics has been found to be challenging and it is possible that GC-VUV determination detected other fuel components as olefins. Table 9. Detailed chemical composition for Tall Oil-SAF with GC-VUV (ASTM D8369-21 )

[0150] In addition to olefin determination, determination of cyclic paraffins with GC-VUV has been found to be challenging. Cyclic paraffins have similar boiling points and molecular weights, which can cause co-elution and peak overlap in the chromatogram and cyclic paraffins have weak absorption in the VUV region, which can reduce the sensitivity and signal-to- noise ratio of the detector. Therefore, the detailed chemical composition of Tall Oil-SAF was also analysed with 2DGC-FID (Two-dimensional gas chromatography with flame ionization detection) and 2DGC-MS (Two-dimensional gas chromatography with mass spectrometric detection) and results are presented in Table 10 and Figure 5.

[0151] There is a significant difference in Tall-Oil-SAF compositions between these two methods. GC-VUV gives higher n- and i-paraffin amount (62.1 wt%) and smaller cycloalkane content (29.9 wt%). 2DGC-FID gives 38.7 wt% for n- and i-paraffins and 52.5 wt% for cycloalkane content. 2DGC-FID results give more specific information about the cycloalkanes and classifies cycloalkenes to one-ring alkanes (32.6%) and two-ring cycloalkanes (19.9%). It is possible that two-ring cycloalkanes are wrongly classified in the GC-VUV analysis as branched alkanes. The 2DGC-FID results have been confirmed with mass spectrometry and can be considered more reliable than GC-VUV results. With 2DGC-FID and 2DGC- MS no olefins were reported.

[0152] Table 10. Detailed chemical composition for Tall Oil-SAF (2DGC-FID)

[0153] As can be seen from the results, the characterization of the Tall Oil-SAF shows that its physical and chemical properties are similar to those of Jet A-1 (ASTM D1655-23).

[0154] The Tall Oil-SAF was also tested for additive response and the product showed good additive response both with regard to conductivity and corrosion.

[0155] Example 4 Alternative purification of feedstock, hydroprocessinq and fractionation

[0156] A crude tall oil according to Table 1 (CTO 3) is treated according to the process of Figure 2.

[0157] The crude tall oil was first evaporated in a short path evaporator. At 100 mbar pressure and 255 °C temperature the fraction comprising water, crude sulphate turpentine (CST), light fatty acids and light neutrals (first fraction) was 9.1 wt% and at a temperature of 295 °C the amount of the first fraction was 23.3 wt%. At lower temperatures the amounts were lower and at higher temperatures significantly higher. At lower pressure the first fraction is over 20 wt% already at 255 °C. At 200 mbar pressure and 255 °C temperature the first fraction was 6.5 wt% and at a temperature of 295 °C the amount of the first fraction was 15.9 wt%. The analysis results are shown in Table 11 . Table 11 . First fraction analysis results

[0158] A first fraction (9 wt% of the tall oil material) is obtained at 255 °C temperature and 100 mbar pressure and it is fed to a distilling column dimensioned for the first fraction. A crude fatty acid fraction (about 6 wt% of the tall oil material), a crude sulphate turpentine fraction (about 2 wt% of the tall oil material) and a water fraction are recovered. Analysis results for a crude sulphate turpentine fraction are shown in Table 12. The acid number of the crude sulphate turpentine fraction is 0 measured according to SCAN-T 11 .

[0159] Table 12. Crude sulphate turpentine fraction example

[0160] The second fraction from the first evaporator, comprising fatty acids, resin acids, neutral substances, and residue components, is fed to a second short path (SP) evaporator . A heavy fraction is separated in two evaporators, SPs, in series. Most of the impurities are removed along with the heaviest components. The feed for the SPs is assumed to be free from water and crude sulphate turpentine. The concentrate fraction is fed to a further short path evaporator and a tall oil pitch residue fraction (about 20 wt% of the tall oil material), and a fourth fraction are recovered. The size of the second and third evaporator is adjusted so that the feed to the second distilling column consists of about 55 - 60 wt% of the third fraction and about 40 - 45 wt% of the fourth fraction. The combined condensate of the third fraction obtained from the second evaporator and the fourth fraction obtained from the third evaporator (the combined fraction is about 70 wt% of the tall oil material) are fed to a second distilling column.

[0161] A crude fatty acid fraction (55 wt% of the tall oil material), a tall oil rosin pitch fraction and a tall oil rosin fraction are recovered from the second distilling column. The crude fatty acid fraction from the first distilling column and the crude fatty acid fraction from the second distilling column are combined and a combined crude fatty acid fraction is recovered as purified tall oil material. The first CFA fraction is about 10 wt% of the combined crude fatty acid fraction. Analysis result for a combined crude fatty acid fraction is shown in Table 13 and Table 14.

[0162] Table 13. Analysis of combined crude fatty acid fraction

[0163] Table 14. Impurities of combined crude fatty acid fraction Table 14, cont. Impurities of combined crude fatty acid fraction

[0164] The purified tall oil is fed into a reactor system together with hydrogen under pressure. The reactor system contained commercially available sulfided catalysts. The main reactions taking place in the reactors are removal of heteroatoms, saturation of double bonds and isomerization. The reactors are operated at high pressures, up to 100 bar, at high temperatures, up to 400 °C in the presence of excess hydrogen, up-to H2 / CTO feed rate (Nl / I) 1500. This purified tall oil material is especially suitable as feedstock in the method of the disclosure, as the amounts of impurities is low and turpentine and pitch has been removed.

[0165] Distillation of the hydroprocessed intermediate product is carried out at a cut point of 270 °C, which is selected to achieve a carbon number range of C6 to C16 for the sustainable aviation fuel component (Tall Oil-SAF). This carbon number range ensured that the Tall Oil-SAF had adequate fluidity properties, such as viscosity and freezing point, for blending with Jet A-1 kerosene.

Claims

CLAIMS1. A method for preparing sustainable aviation fuel (60), characterized in that the method comprises(i) pretreating tall oil material (10) by(a1); evaporating tall oil material (10) in a first evaporation step (A) at a temperature between 100 °C and 250 °C and at a pressure between 40 and 80 mbar to obtain a first fraction (1 ) comprising light hydrocarbons and water and a second fraction (3) comprising fatty acids, resin acids, neutral substances, and residue components,(b1 ) evaporating said second fraction (12) in a second evaporation step (B) and at least one further evaporation step (C, D) to obtain a product fraction(s) (4, 4’) comprising fatty acids and resin acids, and a residue fraction (6), and(c1 ) recovering said product fraction(s) (4, 4’) as purified tall oil material (40); or alternatively by(a2) evaporating tall oil material (10) in a first evaporator (100) at a temperature between 255 °C and 295 °C and a pressure between 80 and 220 mbar to obtain a first fraction (11 ) comprising crude sulphate turpentine, light fatty acids, light neutrals, silicon compounds and water and a second fraction (12) comprising fatty acids, resin acids, neutral substances and residue components;(b2-1 ) evaporating said second fraction (12) in a second evaporator (110) at a temperature between 230 °C and 270 °C and a pressure between 5 and 20 mbar to obtain a third fraction (13) comprising fatty acids, resin acids and light neutral substances, and a first concentrate fraction (14); and evaporating said first concentrate fraction (14) in a third evaporator (120) at a temperature between 280 °C and 320 °C and a pressure between 5 and 20 mbar to produce a fourth fraction (16) comprising fatty acids, resin acids and light neutral substances, and a residue fraction (15); or alternatively(b2-2) evaporating said second fraction (12) in a second evaporator (110) at a temperature between 300 °C and 340 °C and a pressure between 3 and 10 mbar to obtain a third fraction (13) comprising fatty acids, resin acids and neutral substances and a residue fraction (15);(c2) distilling said first fraction (11 ) in a first distilling column (200) to obtain at least a crude fatty acid fraction (20);(d2) distilling said third (13) and said fourth fraction (16) of step (b1 ) or said third fraction (13) of step (b2) in a second distilling column (300) to obtain at least a crude fatty acid fraction (30); and(e2) recovering a combined crude fatty acid fraction (40) from said first distilling column (200) and said second distilling column (300) as purified tall oil material (40);(ii) hydroprocessing (400) said purified tall oil material (40) of step (c1 ) or (e2) using one or more catalysts and recovering an intermediate product (50);(iii) fractionating (500) the intermediate product (50) of step (iii) or a fraction (8) thereof into sustainable aviation fuel (60) boiling in the temperature range of 110 - 300 °C.

2. The method according to claim 1 , characterized in that the evaporating in step (b1 ) comprises a second evaporation step (B) and at least three further evaporation steps (C, D).

3. The method according to any of the preceding claims, characterized in that the method further comprises distilling (500) the intermediate product (40) of step (ii) into at least a diesel fraction (8) distilled within the temperature range of 150 - 370 °C, and wherein said sustainable aviation fuel (60) is distilled from said diesel fraction (8) in the fractionating of step (iii).

4. The method according to any of the preceding claims, characterized in that the hydroprocessing (400) is performed in one hydroprocessing reactor or in two or more hydroprocessing reactors, wherein the hydroprocessing reactor(s) comprises one or more catalyst bed(s).

5. The method according to any of the preceding claims, characterized in that the method further comprises one or more guard unit(s), wherein the guard unit(s) are separate from the hydroprocessing reactor(s), or included upstream of the hydroprocessing catalyst bed(s) in the same reactor(s).

6. The method according to any of the preceding claims, wherein the hydroprocessing step is performed using one or more catalysts which each comprise one or more metals selected from Group VIA and Group VIII metals and one or more support materials selected from zeolite, alumina, gamma-alumina, zeolite-alumina, alumina- silica, ZrO2, alumina-silica-zeolite and activated carbon.

7. The method according to claim 6, wherein the metals are selected from Mo, W, Co, Ni, Pt and Pd.

8. The method according to claim 6 or 7, wherein the hydroprocessing step is performed using one or more reactors which each comprise catalysts comprising one or more metals selected from Group VIA and Group VIII metals, preferably a mixture of CoMo and / or a mixture NiMo, and / or a mixture of Ni, Mo and Co and / or NiW, and one or more support materials selected from zeolite, alumina, silica, zeolite-alumina, alumina-silica, alumina-silica-zeolite and activated carbon.

9. The method according to any of the preceding claims, characterized in that the tall oil material used as feedstock is a sole crude tall oil or a mixture of different crude tall oils.

10. The method according to any of claims 1 - 8, characterized in that the tall oil material used as feedstock is a mixture of crude tall oil(s) and a different fatty acid feedstock(s), wherein the different fatty acid feedstock(s) is chosen from one or more of tall oil fatty acid and any other fatty acid(s) of biological origin.11 . The method according to any of the preceding claims, characterized in that the tall oil material is the sole feedstock.

12. The method according to any of the preceding claims, characterized in that the method further comprises removing a gas phase in a phase separator directly after step (ii).

13. The method according to any of the preceding claims, characterized in that the sustainable aviation fuel of step (iv) comprises over 30 wt% of n- and i-paraffins, more preferably over 40 wt% of n- and i-paraffins, and most preferably over 50 wt% of n- and i-paraffins.

14. The method according to any of the preceding claims, characterized in that the sustainable aviation fuel of step (iv) comprises over 25 wt% of cycloalkanes, more preferably over 28 wt% of cycloalkanes, and most preferably over 50 wt% of cycloalkanes.

15. The method according to any of the preceding claims, characterized in that the sustainable aviation fuel of step (iv) comprises over 8 wt% of aromatic hydrocarbons.

16. The method according to any of the preceding claims, characterized in that the method further comprises adding additives to the sustainable aviation fuel of step (iv).

17. The method according to any of the preceding claims, characterized in that the method further comprises blending the sustainable aviation fuel of step (iv) with an aviation turbine fuel, preferably a Jet A-1 fuel.

18. The method according to claim 17, characterized in that the amount of sustainable aviation fuel of step (iv) is 1 -99 vol.% based on the volume of the blend .

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