A method for the production of a lignin oil

Abstract

The present invention relates to a method for the production of a lignin oil, and the lignin oil obtained by the method. The method comprises liquefying a lignin material by thermal treatment at a temperature of from 100 °C to 245 °C in the presence of a base comprising potassium ions, and a non-aqueous fluid comprising ethanol; followed by addition of an acid to the lignin oil to precipitate potassium salt, and thereafter subjecting the lignin oil to demetallization.

Description

[0001] A METHOD FOR THE PRODUCTION OF A LIGNIN OIL

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for the production of a lignin oil, and the lignin oil obtained by the method.

[0004] TECHNICAL BACKGROUND

[0005] The current and expected demand for biofuels greatly exceeds the available supply. Advanced biofuels are of particular interest, as this class of biofuels does not compete with food crops for feedstock biomass. There is great potential for bioenergy from residues and wastes from wood logging and wood processing - this global potential has been estimated to be 2.4 Gm3per year (28 EJ per year), and the economic-ecological potential for Europe's existing disturbed forests was estimated to be 405 Mm3(Smeets & Faaij, Bioenergy potentials from forestry in 2050, Climatic Change, 2007).

[0006] Lignin materials such as lignin and lignocellulosic materials from such residues and wastes are more complex and difficult to process than are sugars and vegetable oils, and thus, cannot be economically converted into fuels and chemicals by the currently available technologies.

[0007] A major barrier to the efficient conversion of lignin materials to biofuels is liquefaction of the raw materials, due to the low solubility of lignin in water and other common solvents. The most prominent methods currently in use for the production of bio-oils from lignocellulosic materials are hydrothermal liquefaction and pyrolysis.

[0008] Hydrothermal liquefaction (HTL) processes typically operate at high temperatures (300- 400 °C) and pressures (100-350 bar), requiring expensive equipment. Yields of HTL processes are limited by repolymerization and condensation reactions that lead to the formation of char and other solids. Pyrolysis of lignin into bio-oil is most commonly done via flash pyrolysis at temperatures of 400 to 700 °C, requiring expensive equipment. Pyrolysis yields are also limited by the formation of char. Pyrolysis of lignocellulosic materials with higher lignin content has been reported to result in higher amounts of char. Pyrolysis oils are highly corrosive and unstable due to the high levels of acids, water, and aldehydes. The challenging properties of pyrolysis oils currently limit large-scale processes to co-refining, where the pyrolysis oils are blended into crude oil-derived streams, for example, with vacuum gas oil when fed to a fluidized bed catalytic cracking unit.

[0009] Complete dissolution of the lignin material without char formation or solid residue is desirable in order to maximize the yield of the process. It is also desirable to minimize the yield loss to CO2 during the liquefaction process by operating at moderate temperatures, since losses to CO2 have been observed to increase with increasing temperature.

[0010] Another challenge for the production of biofuels and biochemicals from materials containing lignin is the presence of metals that can inhibit or deactivate catalysts used in refining processes such as hydroprocessing. Certain methods for the demetallization of bio-oils disclose low product phosphorus levels but have not effectively reduced the levels of other metals. For example, the method described in WO 2015 / 095453 Al was effective for reducing phosphorus but not potassium.

[0011] In traditional crude oil refineries, hydroprocessing catalyst beds are protected by guard beds that comprise an inert trapping material, hydrodemetallization catalysts, or a combination of both. The higher the metal content in the hydroprocessing feed and / or the longer the time period between catalyst changeouts or catalyst skims, the larger the guard bed needed.

[0012] Phosphorus is of particular concern, as it is present in bio-oils in the form of phospholipids and, thus, is more difficult to remove than water-soluble metals. Both phospholipids and phosphorus are known to deactivate hydroprocessing catalysts. Other metals, such as calcium and magnesium, have been reported to be bound to phospholipids. In order to remove phosphorus from bio-oils, the phospholipids must be decomposed. Decomposition of the phospholipids facilitates removal of phosphorus either in the aqueous phase or at the interface between the two phases.

[0013] It is desirable to reduce both the content of phosphorus and metals such as aluminium, calcium, magnesium, manganese, phosphorus, potassium, and sodium of the lignin oil via demetallization prior to hydroprocessing to maximize the time period between catalyst changeouts or catalyst skims and to minimize the volume of guard bed required. Moreover, it is also desirable to reduce the content of phosphorus and metals by a means that allows for hydroprocessing of the entire lignin oil, as opposed to, for example, removal of fractions of the lignin oil containing high levels of metals prior to hydroprocessing.

[0014] There is still a need for an improved method for efficient liquefaction of lignin and reduction of the metal content in lignin oils.

[0015] SUMMARY OF THE INVENTION

[0016] An object of the present invention is to provide a method for the production of a lignin oil. A further object is to provide a lignin oil with a very low metal content. The lignin oil provided is flowable and is a suitable feedstock for hydroprocessing into fuels or chemicals.

[0017] The present invention is a feedstock-flexible process that converts different types of raw materials, ranging from lignocellulosic materials with a lignin content of about 40 wt% to isolated lignin containing about 100 wt% lignin, into lignin oils that are suitable for further refining into fuel or chemicals by means such as hydroprocessing. The feedstocks of interest for the present invention may comprise materials in which the lignin has been isolated or extracted from biomass or otherwise concentrated. The present invention utilizes mild or moderate temperatures and pressures, allowing for lower equipment costs than HTL or pyrolysis, and simplifies the addition of feedstock to the conversion process.

[0018] To increase the overall process yield, particularly on a carbon basis, organic compounds can be recovered from aqueous and gaseous streams. Organic compounds released into an aqueous phase that is separated from the lignin oil can be recovered by liquid-liquid extraction or other processes to avoid yield losses to wastewater. Gases formed in the liquefaction and demetallization steps can be captured and utilized as biogas or fed to other reactive processes, such as reforming or shift conversion, to produce hydrogen for use in hydroprocessing of the lignin oil.

[0019] Complete depolymerization of lignin into its constituent monoaromatic compounds is not required during liquefaction, or even desired. Rather, a production of a lignin oil without char formation maximizes yield and provides flexibility for downstream use, wherein fuel and chemicals with a range of molecular weights can be produced by the present invention.

[0020] The method of the present invention provides a lignin oil having a long boiling temperature range, wherein the lignin oil comprises high boiling fractions. This is an advantage as it enables a flexibility in the end products to be obtained from the lignin oil.

[0021] The method and the lignin oil according to the present invention are defined in the appended claims.

[0022] LIST OF DEFINITIONS

[0023] Hydroprocessing: a number of catalytic processes in the presence of hydrogen gas for removal of sulphur, oxygen, nitrogen and metals, or saturation of olefins and aromatics. Hydroprocessing encompasses hydrocracking, hydrotreating, hydrodewaxing, and hydrodemetallization. Hydrocracking: a catalytic process for breaking down large organic molecules into smaller molecules by the breaking of carbon-carbon bonds in the presence of hydrogen gas.

[0024] Hydrotreating: a catalytic process for the removal of heteroatoms from chemicals, biogas, bio-oils, oils, or fuels in the presence of hydrogen. Hydrotreating also includes saturation of olefins and aromatics. Hydrotreating encompasses hydrodearomatization (HDA), hydrodenitrogenation (HDN), hydrodesulfurization (HDS), hydrodeoxygenation (HDO), hydrofinishing, and olefin saturation.

[0025] Hydrodesulfurization (HDS): a catalytic process for removing sulphur (S) from chemicals, bio-gas, oils, bio-oils, or fuels in the presence of hydrogen gas. HDS reactions release sulphur as hydrogen sulphide (H2S).

[0026] Hydrodenitrogenation (HDN): a catalytic process for removing nitrogen (N) from chemicals, bio-gas, oils, bio-oils, or fuels in the presence of hydrogen gas. HDN reactions release nitrogen as ammonia (NH3). Also known as hydrodenitrification.

[0027] Hydrodeoxygenation (HDO): a catalytic process for removing oxygen (O) from chemicals, bio-gas, oils, bio-oils, or fuels in the presence of hydrogen gas. HDO reactions release oxygen as water.

[0028] Hydrodemetallization (HDM): a catalytic process for the removal of metals from chemicals, bio-gas, oils, bio-oils, or fuels in the presence of hydrogen gas.

[0029] Hydrofinishing: a final hydrotreating step after hydrocracking and / or hydrotreating that improves the colour and oxidation stability of the product.

[0030] Hydrodewaxing: the reduction of the wax content, such as paraffin wax (C18-C36 hydrocarbons), from hydrocarbons during oil refining in the presence of hydrogen gas. Hydrodewaxing includes dewaxing by shape-selective hydrocracking, isomerization, and combinations of shape-selective hydrocracking and isomerization.

[0031] Shape-selective hydrocracking: hydrocracking using shape-selective catalysts.

[0032] Shape-selective catalysts: catalysts whose shape, such as pore structure, affects a chemical reaction. Hydrodewaxing via shape-selective hydrocracking uses the pore structure to selectively crack normal paraffins. Simulated Distillation: a method for determination of the boiling point distribution in an oil or fractions thereof by gas chromatography according to EN 15199-1, where the percentage distilled is calculated as a function of temperature.

[0033] BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 shows simulated distillation of lignin oil by gas chromatography. The cumulative weight percentage recovered is presented as a function of the boiling point of the components of the sample (x-axis: effective temperature; y-axis: cumulative weight percent recovered).

[0035] Figure 2 shows simulated distillation of lignin oil by gas chromatography. The analysis area percent of the gas chromatogram is presented as a function of the effective temperature.

[0036] DETAILED DESCRIPTION OF THE INVENTION

[0037] In a first aspect, the present invention relates to a method for providing a lignin oil, wherein the method comprises the steps of: a) adding a lignin material; b) adding a non-aqueous fluid comprising ethanol; c) adding a base comprising potassium ions, preferably a base selected from potassium hydroxide, potassium alkoxide and / or potassium hydride; d) subjecting the mixture comprising lignin, the base, and the non-aqueous fluid, to a thermal treatment at a temperature of from 100 °C to 245 °C, preferably of from 110 °C to 240 °C, more preferably of from 120 °C to 235 °C; to obtain a liquid comprising lignin oil; e) adding an acid to the lignin oil to precipitate potassium salt, and optionally washing the precipitated salt; f) optionally adding one or more of water, an acid, a bio-oil, or a solvent, to the lignin oil to obtain a mixture; g) subjecting the lignin oil obtained in e), or the mixture obtained in step f), to a temperature of from 10 °C to 320 °C, preferably of from 80 °C to 250 °C, more preferably of from 120 °C to 200 °C, to obtain a second mixture comprising an aqueous phase and a lignin oil; h) removing the aqueous phase from the second mixture to obtain a demetallized lignin oil; i) optionally repeating steps f)-h); and j) optionally subjecting the demetallized lignin oil to hydroprocessing; whereby the demetallized lignin oil obtained has a total metal content of less than 200 ppm, preferably of from 0 to 50 ppm.

[0038] The steps a) to j) may be performed in consecutive order. Alternatively, steps a), b) and c) could be performed in any order. Steps e) and f) may be performed in the reverse order. Step d) has to be performed after steps a), b) and c) and before e) and f). Step g) and h) have to be performed in said order after the last of steps e) and f).

[0039] Steps f)-h) may be repeated at least once. Repeating steps f)-h) enables reduction of the total metal content and facilitates efficient phosphorus removal. In one embodiment, an acid is added in the first instance of step f) and when repeated, water without acid is added.

[0040] All aspects and embodiments disclosed herein can be combined with any other aspect and / or embodiment disclosed herein.

[0041] The term 'lignin material' is defined herein as a material comprising at least 40 wt% lignin as calculated on the total dry weight of the material, and up to and including 100 wt% lignin. The amount of lignin is determined as Klason lignin, which is the residue obtained after removal of the carbohydrate portion of wood or plant tissue by total acid hydrolysis. The content of Klason lignin is determined by a gravimetric method, for example by TAPPI Standard T 222. In one embodiment, the lignin material is selected from Kraft lignin, hydrolysis lignin, organosolv lignin, lignosulfonates, sulphur lignin, sulphur-free lignin, soda lignin, alkaline lignin, or any other lignin separated from biomass. The method according to the present invention provides for a lignin oil having a total metal content of less than 200 ppm, preferably of from 0 to 50 ppm, more preferably of from 0 to 20 ppm, even more preferably of from 0 to 10 ppm; and a total phosphorus content of less than 10 ppm, preferably of from 0 to 5 ppm.

[0042] The term "fluid" is used herein for gases as well as liquids.

[0043] The non-aqueous fluid added in step b) comprises ethanol. The recovery of ethanol is relatively energy efficient in comparison with other solvents, and distillation may be performed at relatively low temperature. Ethanol is a good solvent for the lignin oil obtained during the liquefaction. Bio-oils and ethanol are also miscible, which means that a bio-oil, for example a lignin oil recycled from elsewhere in the process, can be used as a non-aqueous solvent for the lignin material in step b), whereby the amount of ethanol can be reduced. In one embodiment, the non-aqueous fluid comprises at least 5 wt% ethanol. An ethanol content of at least 5 wt% reduces the viscosity of the lignin oil, thus improving processability. The non-aqueous fluid can comprise up to 100 wt% ethanol.

[0044] Furthermore, ethanol facilitates precipitation of potassium sulphate and other sulphate salts when a sulfuric acid is added in step e) as compared to other alcohols. Consequently, the use of ethanol is preferred when precipitating salts. Ethanol may also dissolve both hydrophobic and hydrophilic molecules and is an excellent solvent for purifying the precipitated salts, as it washes away the lignin oil and organic compounds remaining in the precipitated salt without dissolving the salt.

[0045] In addition to ethanol, , the non-aqueous fluid may further comprise at least one of Ci- io alcohol, Ci-30 hydrocarbon, a bio-oil, an ether, an alkyl acetate, a ketone, sulfolane, a fluid stream recycled from a hydroprocessing step, or any combination of two or more thereof. The ketone is preferably acetone. The use of a recycled process stream, such as bio-oil or a fluid stream from a hydroprocessing step, reduces the requirement for fresh non-aqueous fluid, such as a Cuo alcohol.

[0046] In one embodiment the non-aqueous fluid comprises a Ci-io alcohol in addition to the ethanol. Preferably said Cuo alcohol is selected from methanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, glycerol, propylene glycol, cresol, resorcinol, hydroquinone, guaiacol, catechol, phenol, or benzyl alcohol, or any combination thereof. Preferably, the Cuo alcohol has a boiling point of from 50 to 250 °C. More preferably said Cuo alcohol is selected from methanol, guaiacol, catechol, phenol, or benzyl alcohol. Even more preferably, said Cuo alcohol is methanol. Preferably, the alcohol is derived from renewable sources. The alcohol component of the non-aqueous fluid functions not only as a solvent but also as a capping agent of lignin derivatives via alkylation, thereby suppressing repolymerization reactions between reactive phenolic compounds that lead to char formation. Selection of the alcohol impacts the solubility and solvation characteristics of the resulting bio-oil, wherein selection of an alcohol with more hydrophobic character results in more hydrophobic lignin derivatives.

[0047] In one embodiment the non-aqueous fluid added in step b) further comprises a C1-30 hydrocarbon or a mixture of C1-30 hydrocarbons in. Preferably, the C1-30 hydrocarbon is a saturated hydrocarbon, more preferably a C1-30 alkane, which may be branched, linear, or cyclic. The C1-30 hydrocarbon is preferably selected from propane, butane, hexane, heptane, octane, nonane, decane, undecane and dodecane, which may be branched or linear, or from cyclic (naphthenic) hydrocarbons, such as those produced from the saturation of lignin and lignin derivatives.

[0048] The bio-oil optionally added as a part of the non-aqueous fluid in step b) or the bio-oil added in step f) is each independently preferably selected from a lignin oil recycled from a process comprising the method presented herein, or a bio-oil selected from tall oil pitch, crude tall oil, pyrolysis oil, lignin oil, hydrothermal liquefaction oil, turpentine, vegetable oil, oil obtained from any one of lignocellulosic material, softwood, hardwood, bagasse, bark, sawdust, other types of forest biomass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, agriculture raw materials, or agriculture residues, aquaculture residues, animal residues, food industry residues, or a combination thereof.

[0049] As used herein, the expression "agriculture residues" include the parts of the plants with agricultural origin not used for food, including stalks, stems, haulm, leaves, straw, corn stover, bagasse, peel, nutshell, fruit kernel, husks. As used herein, the expression "other types of forest biomass" encompasses plants and trees from plantations of any age, including short rotation coppice, and includes all parts of the tree, such as the trunk, including pieces thereof, bark, branches, needles or leaves, cones and roots.

[0050] Examples of hardwood are the Betulaceae family: such as alder, birch, hazel, hornbeam; Fabaceae family: such as acacia (subfamily mimosoideae); Fagaceae family: such as beech, chestnut, oak; Juglandaceae family: such as hickory, pecan, walnut;

[0051] Myrtaceae family: such as gum, eucalyptus, angophora; Rosaceae family: such as Prunus genus: cherry; Salicaceae family: such as aspen, cottonwood, poplar, willow; Sapindaceae family: such as maple, buckeye, horse chestnut, and Ulmaceae family: such as elm, zelkova. Examples of softwood are Ginkgoaceae family: ginkgo biloba; and conifers, comprising Araucariaceae family: such as kauri; Cupressaceae family: such as cypress, juniper, redwood; Pinaceae family: such as cedar, Douglas-fir, fir, hemlock, larch, pine, spruce, tamarack; Podocarpaceae family: such as yellowwood; Taxaceae family: such as yew.

[0052] In one embodiment, vegetable oils are excluded as non-aqueous fluid. A reason for this is not to compete with resources from food industry. Examples of vegetable oils excluded are a$ai palm oil, avocado oil, Brazil nut oil, buriti oil, canola oil, carapa oil, coconut oil, corn oil, cottonseed oil, grape seed oil, graviola oil, hazelnut oil, hemp seed oil, jambu oil, linseed oil, olive oil, palm oil, palm kernel oil, passion fruit oil, peanut oil, pracaxi oil, rapeseed oil, rice bran oil, safflower oil, sesame oil, Solarium oil, soybean oil, sunflower oil, tucuma oil, and walnut oil. More preferably, the bio-oil added as a non- aqueous fluid in step b) and the bio-oil added in step f) is each independently selected from lignin oil recycled from a process comprising the method presented herein; tall oil pitch; crude tall oil; pyrolysis oil; lignin oil; hydrothermal liquefaction oil; turpentine; oil obtained from any one of lignocellulosic material, softwood, hardwood, bagasse, bark, sawdust, other types of forest biomass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, agriculture raw materials, agriculture residues, food industry residues; or a combination thereof.

[0053] In one embodiment, the non-aqueous fluid comprises a lignin oil that is recycled from the process disclosed herein. The lignin oil recycled from the process may contain alcohols produced in the liquefaction process, such as methanol, ethanol, propanol, guaiacol, catechol and other phenolic alcohols. Said alcohols, once recycled, aid in dissolving lignin material added to the process. Said alcohols may also serve as capping agents.

[0054] Liquefaction of lignin material can be carried out in the presence of a catalyst to aid in the depolymerization of the lignin. Base-catalysed depolymerization of lignin suppresses repolymerization and char formation during liquefaction and thus is favoured over acid- catalysed depolymerization. Complete dissolution of the lignin material without char formation is desirable in order to maximize the yield of the process.

[0055] In one embodiment, the base comprising potassium ions that is added in step c) is selected from potassium hydroxide, potassium alkoxide and / or potassium hydride. Preferably, the base comprising potassium ions is selected from potassium hydroxide, potassium methoxide, potassium ethoxide, potassium isopropoxide, potassium tert- butoxide or potassium hydride. More preferably the base is selected from potassium hydroxide, potassium ethoxide and potassium hydride. Even more preferably the base is potassium hydroxide. Addition of a metal hydroxide, such as sodium hydroxide or potassium hydroxide, to a mixture comprising lignin material and an alcohol, such as methanol or ethanol or propanol, provides for the formation of potassium alkoxide, e.g., potassium methoxide potassium ethoxide, or potassium isopropoxide, upon heating, which is a stronger base than potassium hydroxide, thus improving the process economy in the conversion of lignin material to lignin oil. Alternatively, a metal alkoxide in an alcohol solution, such as potassium ethoxide in ethanol solution, can be added to the lignin material.

[0056] An advantage with using potassium-containing bases is that potassium is more reactive than sodium. This may be due to the valence electrons being situated further away from the nucleus in potassium than in sodium, thus providing for a quicker dissociation. Using a base comprising potassium ions in the method according to the present invention, provides for 100 % liquefaction of the biomass, i.e. no solid residue from the biomass remains.

[0057] Too small amounts of potassium in relation to the amount of lignin material will not give 100 % depolymerization. In one embodiment the amount of potassium ions to Moisture and Ash Free (MAF) biomass is at least 0.2:1 part by weight, preferably at least 0.3:1, or more preferably 0.4:1. The upper limit of the amount of potassium ions is irrelevant for effecting the method, although from an economic perspective the upper limit of the amount of potassium ions to Moisture and Ash Free (MAF) biomass may be 100:1, preferably 10:1. The person skilled in the art knows how to calculate the amount of potassium ions and that the water content of the base should be discounted.

[0058] The base added in step c) may further comprise a weak base, a strong base or a superbase. Use of a homogeneous base, i.e., without a support, rather than a heterogeneous supported base, as catalyst, avoids operational difficulties involved with the separation and recovery of the catalyst from the resulting lignin oil, as well as deactivation of the heterogeneous catalyst.

[0059] The weak base can be selected from organic bases, such as pyridines, anilines, tertiary aliphatic amines; or from inorganic bases, such as sodium bicarbonate. A weak organic base may also function as a solvent or co-solvent for the liquefaction mixture. In one embodiment the strong base is selected from sodium sulphide, sodium hydroxide, barium hydroxide, calcium hydroxide, caesium hydroxide, lithium hydroxide, rubidium hydroxide, or strontium hydroxide, or any combination thereof. The strong base is preferably selected from sodium sulphide, or sodium hydroxide, or any combination thereof.

[0060] A superbase is defined in IUPAC as a compound that has a very high basicity. In this specification the same definition is used. Examples of superbases are organometallic or inorganic compounds, such as a Grignard reagent; hydrides of alkali metals, such as lithium hydride, or sodium hydride; combinations of organolithium compounds with alkali metal alkoxides, such as n-butyllithium and potassium tert-butoxide; or from organic compounds, such as phosphazenes, e.g. Schwesinger phosphazenes, proazaphosphatranes, such as Verkade proazaphosphatranes; phosphines; amidines; such as Schwesinger vinamidines; guanidines; or metal amides, such as lithium diisopropylamide; or any combination thereof. Specific examples of alkali metal alkoxides are alkali-metal Ci-6 alkoxides, such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, or potassium tert-butoxide.

[0061] In one embodiment, the mixture subjected to thermal treatment in step d) comprises 5- 50 wt% lignin, 1-35 wt% base, and 30-94 wt% of a non-aqueous fluid up to a maximum or a total of 100 wt%, as calculated on the total weight of the mixture. Preferably, the mixture comprises 8-40 wt% lignin, 5-25 wt% base, and 40-87 wt% of a non-aqueous fluid, up to a maximum or a total of 100 %, as calculated on the total weight of the mixture. More preferably, the mixture comprises 10-35 wt% lignin, 10-20 wt% base, and 50-80% of a non-aqueous fluid, up to a maximum or a total of 100 %, as calculated on the total weight of the mixture.

[0062] In one embodiment the lignin material, or the mixture subjected to thermal treatment in step d), has a water content of from 0 to 40 wt%, preferably of from 0 to 30 wt%, most preferably less than, and not including, 10 wt%. In one embodiment, the mixture in step d) has a total water content of from 0 to 9 wt%, before the mixture is subjected to the thermal treatment.

[0063] By dispersing the lignin material with a non-aqueous fluid, the base (e.g., KOH) can form alkoxide ions instead of hydroxide ions, increasing the strength of the base and thereby improving the rate and extent of depolymerization of lignin. Use of a stronger base, such as an alkoxide instead of the corresponding hydroxide, can also reduce the amount of base required for liquefaction. Consequently, it is advantageous to minimize water in the process, e.g., by limiting the initial water content of the mixture. Preferably, no free water is added in steps a) to d). The term "free water" is used herein for water that is, or was, not contained in the lignin material.

[0064] Water can be formed via dehydration reactions during the liquefaction process. Said water can be removed by evaporation, distillation, or liquid-liquid extraction once the lignin material has been liquefied.

[0065] By subjecting the mixture comprising lignin, a base, and non-aqueous fluid to a temperature of up to 245 °C, preferably, of from 100 °C to 245 °C, more preferably of from 110 °C to 240 °C, even more preferably from 120 °C to 235 °C; during a time period of from 1 to 360 minutes, from 5 to 300 minutes, or from 16 to 300 minutes, or from 16 to 240 minutes, or from 16 to 180 minutes, or from 30 to 150 minutes, or from 30 to 120 minutes, or from 35 to 90 minutes, in step d), a liquid comprising lignin oil is provided, without involving any extraction of solid materials. The quality and yield of the resulting bio-oil depend on the temperature applied. The use of temperatures of not more than 245 °C, or not more than 240 °C thus provides a homogeneous oil without formation of char or visible particles of biomass or other organic origin. Moreover, at a temperature of 240 °C the yield is close to 100% by mass. More gas is formed already at slightly higher temperatures. Excessively high temperatures (> 330 °C) result in significant yield losses due to decarboxylation and gas formation, as well as char formation. Excessively high temperatures also require a greater energy input than that needed to liquefy the biomass into a bio-oil. Liquefaction of the lignin material to a lignin oil proceeds as depolymerization occurs, catalysed by the base. The rate of depolymerization depends on the temperature of the mixture. The time period required to convert the lignin to a lignin oil during the basecatalysed liquefaction depends on the temperature of the lignin mixture. Achieving a certain extent of depolymerization requires shorter time periods when using higher temperatures. The time period for subjecting the mixture in step d) to the desired temperature is preferably long enough to provide heat uniformity.

[0066] The required time period also depends on the temperature that the components, i.e., the lignin, base, and non-aqueous fluid, have when they are added to the mixture. As used herein, the term time period is equal to residence time. Whereas time period is usually used for a batch process and residence time is usually used for a continuous process, the terms may be used interchangeably herein. The required time period also depends on the temperature that the components, i.e. the biomass, base, and nonaqueous fluid, have when they are added to the mixture.

[0067] The temperature during the thermal treatment in step d) may be changed gradually, continuously, or in several heating stages over a period of time. The thermal treatment may be performed with only one heating stage. The desired temperature may be reached by using pre-heated lignin material, or pre-heated non-aqueous fluid, or preheated base, from any of the previous steps a) to c); and / or by heating of the mixture in step d).

[0068] When performing several heating stages, such as two heating stages, the lignin material may be liquefied during the first heating stage(s), and during the final heating stage(s), the lignin is depolymerized to the desired extent. The temperature could be kept constant, or essentially constant, during any one heating stage. Essentially constant is in this context defined as a temperature variation of less than 10% of the desired temperature. Removing water prior to the final heating stage ensures that the base is in the alkoxide form rather than the hydroxide form, thereby improving the effectiveness of the base during the lignin depolymerization. Water, when present, may be removed by distillation, evaporation, or by liquid-liquid extraction.

[0069] The thermal treatment in step d) may be performed at conditions where the nonaqueous fluid is in a near-supercritical or supercritical state. As used herein, the near- supercritical state denotes the state where the fluid is in the vicinity of its critical point, such as 20 °C below its critical temperature, for example at temperatures of 220-240 °C when using ethanol at a pressure of 63 bar.

[0070] In one embodiment, wherein during the thermal treatment in step d), the mixture is subjected to at least one temperature in the range from 100 °C to 190 °C in a first heating stage, whereupon the mixture is subjected to at least one temperature in the range from 180 °C to 240 °C in a second heating stage. The temperature of the second heating stage is preferably higher than the temperature of the first heating stage, more preferably by at least 20 °C. In one embodiment, the first heating stage lasts for a time period of from 3 to 210 minutes, preferably from 3 to 150 minutes, and the second heating stage lasts for a time period of from 2 to 150 minutes, preferably from 3 to 120 minutes.

[0071] The base-catalysed liquefaction may be performed batch-wise, semi-batch-wise, or in continuous operation, in a single vessel or in multiple vessels. Different types of equipment may be used, such as a stirred tank reactor, plug flow reactor, or vessels in series. Digesters used in the pulp industry in various configurations, such as batch, continuous, horizontal, and multitube reactors, are examples of suitable equipment. Heat exchange can be attained in various configurations, such as by using a heated vessel, multitube heat exchangers, or combinations thereof. Heating the mixture in stages to different temperatures for different times can be accomplished with different types of vessels in series, using various residence times and different configurations. For example, the first stage of liquefaction may take place in a stirred tank at a first temperature with a long residence time, followed by a second liquefaction stage at a higher temperature with a shorter residence time than that of the first stage. Pre-heated base, and / or non-aqueous fluid(s) may be added between stages of liquefaction.

[0072] Addition of the non-aqueous fluid can be performed at any point or at multiple points throughout the liquefaction in step d). In one embodiment, methanol and / or ethanol are added in the vapor phase, preferably above the boiling point of water. Water is condensed and removed from the process, while methanol and / or ethanol vapours are recycled to the reactor. This distillation process can be done under vacuum or under pressure. The advantage with this procedure is continuous removal of water. If the liquefaction is done in two stages, the second stage could be performed at a higher pressure than the first, so that the alcohol is in the liquid phase in the second stage and in the gas phase in the first stage. An advantage of using relatively low pressure in the first stage is simplified feeding of lignin material to the reactor.

[0073] In one embodiment any solids remaining from the lignin material are removed from the lignin oil obtained in step d). Preferably, the solids are removed from the obtained lignin oil before the second heating stage in step d). The removed solids may be used for sugar production or as a pulp material.

[0074] An acid, preferably a strong acid, e.g., hydrochloric acid, sulfuric acid, or nitric acid, is added in step e) which neutralizes or acidifies the liquid comprising the bio-oil. The addition of the acid may also precipitate salts. In one embodiment, the method further comprises a step of removing salts from the liquid comprising lignin oil obtained in step e). The precipitated salts are preferably removed by filtration. Removal of salts produces a higher quality lignin oil, while at the same time allowing the salts to be used for other purposes, e.g. as fertilizer.

[0075] In one embodiment, the precipitated salt is purified with a washing liquid essentially not dissolving the salt or acting as an anti-solvent to the salt. Preferably, the washing liquid is selected from Cuo alcohol, C2-7 ester or C3-7 ketone, or any combination thereof. More preferably, the washing liquid comprises ethanol, ethyl acetate or acetone. Even more preferably the washing liquid is ethanol.

[0076] In one embodiment, the potassium salt precipitated in step b) is further purified to obtain a salt having an organic content of less than 1000 ppm, preferably less than 500 ppm, more preferably less than 100 ppm.

[0077] Washing the precipitated salt to a suitable purity allows it to be used as fertilizer, since fertilizers should preferably have a maximum organic content of 100 ppm. Yet another reason to wash the salt is to remove organics, including lignin oil, from the salt. The lignin oil washed away from the salt may be pooled with the lignin oil obtained in the liquefaction step, thereby providing a higher overall lignin oil yield.

[0078] In one embodiment, step e) further comprises washing the precipitated salt with ethanol. Lignin oil is soluble in ethanol and thereby washing the salts with ethanol enables a higher overall yield of lignin oil. The reason being that the lignin oil washed out from the salts can be reintroduced to the process or pooled with the lignin oil already obtained in the liquefaction step. The ethanol may also be recirculated, e.g. as a nonaqueous fluid.

[0079] Acids and bases used in the method according to the present invention can be selected so as to obtain precipitates that can be used as fertilizers or other useful products. The skilled person is well equipped to choose suitable acids and bases to this end. For example, addition of sulfuric acid or nitric acid causes potassium ions occurring in the lignin oil to precipitate as potassium sulphate and potassium nitrate, respectively. Thus, in a preferred embodiment the acid for salt precipitation, i.e., the acid added in step e), is selected from sulfuric acid or nitric acid.

[0080] The lignin oil obtained in step e), is subjected to demetallization, preferably by acid treatment. Demetallization provides for the removal of metals from the lignin oil. Demetallization of the lignin oil, i.e., steps f) -h) of the present invention, may comprise addition of one or more of water, an acid, a bio-oil, or a solvent, to the lignin oil to obtain a mixture. The lignin oil, or the mixture comprising lignin oil, is subjected to a temperature of from 10 °C to 320 °C, preferably of from 80 °C to 250 °C, more preferably of from 120 °C to 200 °C, to obtain a second mixture comprising an aqueous phase and a lignin oil, followed by removal of the aqueous phase to obtain a demetallized lignin oil. The entire process of liquefaction and demetallization may be performed continuously or batchwise. The latter would minimize the required equipment.

[0081] In one embodiment, the bio-oil added in step f) is selected from a lignin oil recycled from a process comprising the method presented herein, tall oil pitch, crude tall oil, pyrolysis oil, lignin oil, hydrothermal liquefaction oil, turpentine, vegetable oil, oil obtained from any one of lignocellulosic material, softwood, hardwood, bagasse, bark, sawdust, other types of forest biomass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, agriculture residues, aquaculture residues, animal residues, food industry residues; or combinations thereof. In one embodiment, the biooil added in step f) is selected from lignin oil recycled from a process comprising the method presented herein; tall oil pitch; crude tall oil; pyrolysis oil; lignin oil; hydrothermal liquefaction oil; turpentine; oil obtained from any one of lignocellulosic material, softwood, hardwood, bagasse, bark, sawdust, other types of forest biomass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, agriculture raw materials, agriculture residues, food industry residues; or any combination thereof.

[0082] In one embodiment of step f), any bio-oil used may be dispersed in a solvent. The dispersion of the bio-oil may be performed either before or after the addition of water. Addition of a water insoluble solvent in step f) can be advantageous for the subsequent removal of the aqueous phase by facilitating the separation of the aqueous phase from the bio-oil. The need for a solvent depends on the miscibility of the bio-oil with water, which can vary widely depending on the composition of the bio-oil. For example, tall oil pitch and crude tall oil are not readily miscible with water, thus, addition of a solvent to such bio-oils is not necessary from a phase separation standpoint. However, a solvent may be desirable for reducing the viscosity of a bio-oil to facilitate transport or mixing. The mixture of bio-oil and solvent is preferably in a liquid form at a temperature above 120 °C, or above 150 °C.

[0083] In one embodiment, the solvent added in step f) is selected from a water-insoluble C4-6 alcohol, preferably butanol; ethers, such as methyl tetrahydrofuran; alkyl acetates, such as butyl acetate or ethyl acetate; a liquid stream recycled from a hydroprocessing step, or mixtures thereof. The hydroprocessing step from which a liquid stream can be recycled may be the hydroprocessing in step j) according to the invention. Using a recycled stream lowers the requirement for fresh solvent. Solvents of bio-renewable origin are preferred in the production of fuel and chemicals.

[0084] In one embodiment of step f), one or more acids are added, preferably selected from mineral acids, e.g., hydrochloric acid, sulfuric acid, or nitric acid; or from organic acids, such as citric acid, formic acid, lactic acid, oxalic acid, or acetic acid. More preferably sulfuric acid or nitric acid is added in step e). The addition of the one or more acids preferably adjusts the pH of the aqueous phase in the mixture to a pH of 0-6, preferably a pH of 0-4, more preferably a pH of 0-2, even more preferably the pH is less than 1. In an alternative embodiment, the addition of the one or more acids adjusts the pH of the aqueous phase in the mixture to a pH of 1-4, preferably a pH of 1-2. If sufficient acid is added in step e), any acid addition in step f) may be omitted. The acid in step e) and the acid in step f) could be the same or different.

[0085] The mixtures in steps a)-c) and f) may be obtained by any suitable mixing method.

[0086] The present method allows for a large amount of water to be present in the mixture when it is heated during demetallization. The mixture may have a water content of from 10 to 90 wt%, based on the total weight of the mixture; preferably 15-75 wt%, and more preferably 20-60 wt%. Increasing the water content improves removal of metals. Alternatively, repeating the steps without increasing the water content can also improve the removal of metals.

[0087] The desired temperature in step g) may be reached by using pre-heated lignin oil, preheated liquids added in step f); or by direct heating of the mixture obtained in step f). When the contents of step f) are pre-heated prior to obtaining the mixture in step f), said mixture is obtained at a time point when said contents are still warm or hot. Preferably, when the step g) is carried out for the first time, the temperature is from 120 °C to 200 °C, more preferably from 130 °C to 200 °C, even more preferably from 140 °C to 200 °C, and not including 200 °C, and most preferably from 130 °C to 190 °C. This temperature is required for effective decomposition of the phospholipids and subsequent phosphorus removal. However, when step g) is repeated, the phospholipids have already been decomposed in the first instance of step g), hence lower temperatures may be used, such as from 10 °C to 200 °C, preferably from 10 °C to 190 °C; depending on the composition of the lignin oil, wherein the temperature used is sufficient for phase separation. Lower temperatures, such as from 10 °C to 200 °C, or preferably from 10 °C to 190 °C, may also be used the first time step g) is carried out if the lignin material does not contain phospholipids.

[0088] A higher temperature in step g) facilitates a lower content of phosphorus in the obtained demetallized bio-oil. However, if the temperature is too high, e.g., above 200 °C, the separation of the organic and aqueous phases becomes more difficult due to increasing emulsification. Additionally, temperatures below 200 °C are preferred to avoid excess energy usage in the form of heat input beyond that required for an efficient phase separation.

[0089] When steps are repeated, lower temperatures may be used in later instances than in the first instance. Heavy bio-oils with high viscosities require higher temperatures than lighter bio-oils to achieve effective mixing and, subsequently, an efficient phase separation. The use of a solvent can be advantageous to decrease the viscosity of the lignin oil without increasing the temperature. The lignin oil obtained after the salt precipitation in step e) or the mixture obtained in step f) may be subjected to the desired temperature in step g) gradually, continuously, or in several stages over a period of time. The time required for heating depends on the rate of heating and the thoroughness of mixing. The mixture is subjected to the desired temperature for a period of 0.01 to 10 minutes.

[0090] After heat treatment in step g) a mixture comprising an aqueous phase and a lignin oil is obtained. The aqueous phase may have formed through dehydration reactions or derive from the water content of the lignin material, an aqueous solution of the base added in step c) or the acid added in step e), and / or addition of water in the optional step f).

[0091] In one embodiment, the phases of the mixture in step g) are allowed to separate before water is removed. The time required for phase separation depends on the temperature of the mixture, the composition of the mixture, optional addition of an emulsion breaker, and the process equipment used. Phase separation can be carried out in a batch process or continuous process. In a continuous process using a decanter, for example, the mixture is continuously fed to the decanter, while an aqueous stream and an organic stream are continuously removed from the decanter.

[0092] Removal of the aqueous phase from the lignin oil is critical for the removal of metals from the lignin oil, as the metals are partitioned into the aqueous phase. Poor phase separation thereby results in poor demetallization performance. Removal of the aqueous phase by evaporation does not facilitate demetallization, as the metals are not removed with the water in this case. Removal of the aqueous phase can be facilitated by the use of mechanical means, such as a centrifuge, decanter, decanter centrifuge, coalescer, electrostatic coalescer, oil desalter, API (American Petroleum Institute) separator, rotating separator, or by a combination of these; electrical means, such as electrostatic desalting units; chemical means, such as addition of an emulsion breaker; or by a combination of these. Suitable emulsion breakers, also known as demulsifiers, are selected from amines, such as octylamine or dioctylamine; alcohols, such as ethanol or long-chain alcohols; polyhydric alcohols, such as propylene glycol or polyethylene glycol; fatty acid alkoxylates; oxyalkylated alkyl phenols; oxyalkylated alkyl resins; sulfonates; other nonionic surfactants comprising both hydrophilic and hydrophobic groups; or combinations thereof. In the method disclosed herein, the removal of the aqueous phase does not involve the use of enzymes.

[0093] When removal of the aqueous phase in step h) is facilitated by the use of mechanical means, the need for repeating the washing steps may be eliminated, due to the effectiveness of the phase separation resulting in efficient removal of metals.

[0094] In one embodiment, removal of the aqueous phase in step h) is carried out by decanting. After decanting, residual water containing metals may be removed from the lignin oil by mechanical means, electrical means, or chemical means, or any combination of these. In embodiments, the residual water is removed by any one of distillation, evaporation, membrane separation, or by liquid-liquid extraction.

[0095] In one embodiment, after removal of the aqueous phase in step h) using a decanter, the lignin oil is subjected to centrifugation, to remove any remaining water.

[0096] While optional, repeating steps f)-h) enables further reduction of the total metal content, including further phosphorus removal. In one embodiment, an acid is added the first time step f) is carried out, and when repeated, water without acid is added. Using water without acid in the final repeated instance of step f) reduces the corrosivity of the demetallized lignin oil for downstream processing, thus without needing a base for neutralization. Addition of a base to the demetallized lignin oil is not desirable, as this would result in the addition of metals, nitrogen compounds, or other species that are hydroprocessing catalyst inhibitors or catalyst poisons.

[0097] The aqueous phase obtained in step h) may be demineralized and / or extracted with an organic solvent to separate organic compounds therefrom. The water added in step f) may be demineralized water, including distilled water; or the aqueous phase recycled from step h). Recycling the aqueous phase may be performed to reduce the need for demineralized water, whereby recycled water is used in the first instance or instances of step f), and fresh water is used in the last instance or instances when step f) is repeated. Using demineralized water in the final instance of step f) ensures that no metals are introduced to the lignin oil from the wash water.

[0098] Residual water, when present in the demetallized lignin oil, may be removed by distillation, evaporation, membrane separation, or any other suitable method, or by liquid-liquid extraction. The obtained demetallized lignin oil preferably has a water content of less than 10 wt%, more preferably of from 0.01 to 5 wt%, most preferably of from 0.01 to 1 wt%.

[0099] In one embodiment the demetallized lignin oil obtained in h) is subjected to further treatment, such as hydroprocessing, to obtain fuel or chemicals.

[0100] Hydroprocessing of the lignin oil may comprise passing the lignin oil through a guard bed, followed by hydrotreating and optionally, mild hydrocracking and / or hydrodewaxing, and lastly, optionally hydrofinishing the lignin oil with various catalysts. Fractionation is performed to obtain the product fuel and / or chemicals.

[0101] Hydroprocessing, hydrotreatment, hydrocracking, hydrodewaxing, hydrofinishing and fractionation are concepts well known to the skilled person.

[0102] In another aspect, the present invention relates to a lignin oil obtainable by the method according to the present invention. In one embodiment, the obtained lignin oil has a final boiling point (FBP) of at most 700 °C, at most 680 °C, or at most 650 °C. Preferably, at least 50 wt%, preferably at least 75 wt% of the lignin oil boils below 440 °C.

[0103] In a further aspect, the present invention relates to a lignin oil having a total metal content of less than 50 ppm, preferably of from 0 to 50 ppm, more preferably of from 0 to 20 ppm, even more preferably of from 0 to 10 ppm; and a total phosphorus content of less than 10 ppm, preferably of from 0 to 5 ppm. As used herein the total metal content preferably refers to the content of metal selected from aluminium, calcium, magnesium, manganese, phosphorus, potassium, and sodium.

[0104] In one embodiment the lignin oil has a total metal content of less than 20 ppm, preferably of from 0 to 10 ppm, and a total phosphorus content of less than 10 ppm, preferably of from 0 to 5 ppm.

[0105] Preferably, at most 50 wt%, preferably at most 25 wt% of the demetallized lignin oil boils above 440 °C.

[0106] The present invention will now be further illustrated by the below examples. The presented examples should not be seen as limiting the scope of the invention, and the skilled person would realize that there are obvious alternatives and modifications that could be carried out. Experimental methods presented without specific conditions in the following examples generally follow the conventional conditions known to the skilled person. Unless otherwise stated, parts and percentages as used herein are parts by weight and weight percent.

[0107] EXAMPLES

[0108] EXAMPLE 1

[0109] Liquefaction

[0110] 60 g lignin material, 60 g of a base, and 280 g of a non-aqueous fluid according to Table 1 were added to an autoclave and mixed. The mixture was heated to 240 °C and kept at this temperature for 120 minutes while stirring. Table 1

[0111] Salt precipitation and washing

[0112] The contents in the autoclave were cooled to 60 °C and transferred into a beaker. Concentrated sulfuric acid (23 mL) was slowly added to the mixture. A salt precipitation was formed. The liquid containing the was filtrated over a 22 pm retention filter paper in a Buchner funnel. The precipitated salt formed a filter cake on the filter paper. The precipitated salt was rinsed with the non-aqueous fluid. The non-aqueous fluid was removed from the filtrate comprising the lignin oil using a rotary evaporator.

[0113] RESULTS

[0114] Liquefaction

[0115] Liquefaction of the lignin material into a lignin oil was achieved in all tests, wherein no char formation was observed. The best liquefaction results were achieved with ethanol and methanol, wherein the demetallized lignin oil was homogenous. When butanol was used a solids-free liquid was attained, but the lignin oil consisted of two organic phases, wherein the heavy organic phase had a very high viscosity forming a brown rubbery-like mass.

[0116] Salt precipitation

[0117] Precipitation and separation of salts from the lignin oil proceeded easily and quickly when methanol and ethanol was used as the non-aqueous fluid. However, subsequent addition of ethanol caused the salts to precipitate. When butanol was used a brown rubbery-like mass was formed that could not be dissolved with any of ethanol, butanol, acetone or water, making it challenging to separate the precipitated salts therefrom. When water was used, no solids remained in the resulting lignin oil, but separation of the salts from the lignin oil was not feasible.

[0118] Washing of salt

[0119] Repeated washing of the precipitated salt with methanol or ethanol gave an increasingly whiter salt. The brown rubber-like mass obtained with butanol could not be dissolved nor successfully washed with either methanol, ethanol or butanol.

[0120] Simulated distillation

[0121] The simulated distillation of the lignin oil was performed by gas chromatography (EN 15199-1), wherein the entire sample was vaporized and exited the column, showing that no solids were present. The simulated distillation of the lignin oil obtained with ethanol according to the second entry in Table 1 is shown in Figures 1 and 2. 1

Claims

CLAIMS1. A method for providing a lignin oil, wherein the method comprises the steps of a) adding a lignin material; b) adding a non-aqueous fluid comprising ethanol; c) adding a base comprising potassium ions, preferably a base selected from potassium hydroxide, potassium alkoxide and / or potassium hydride; d) subjecting the mixture comprising lignin, the base, and the non-aqueous fluid, to thermal treatment at a temperature of from 100 °C to 245 °C, preferably of from 110 °C to 240 °C, more preferably of from 120 °C to 235 °C; to obtain a liquid comprising lignin oil; e) adding an acid to the lignin oil to precipitate potassium salt, and optionally washing the precipitated salt; f) optionally adding one or more of water, an acid, a bio-oil, or a solvent, to the lignin oil to obtain a mixture; g) subjecting the lignin oil obtained in e), or the mixture obtained in step f), to a temperature of from 10 °C to 320 °C, preferably of from 80 °C to 250 °C, more preferably of from 120 °C to 200 °C, to obtain a second mixture comprising an aqueous phase and a lignin oil; h) removing the aqueous phase from the second mixture to obtain a demetallized lignin oil; i) optionally repeating steps f)-h); and j) optionally subjecting the demetallized lignin oil to hydroprocessing; whereby the demetallized lignin oil obtained has a total metals content of less than 200 ppm, preferably of from 0 to 50 ppm.

2. The method according to claim 1, wherein the lignin material is selected from Kraft lignin, hydrolysis lignin, organosolv lignin, lignosulfonates, sulphur lignin, sulphur- free lignin, soda lignin, alkaline lignin, or any other lignin separated from biomass.

3. The method according to claim 1 or 2, wherein the lignin material or lignin material mixed with a non-aqueous fluid in b) has a water content of from 0 to 40 wt%, preferably from 0 to 30 wt%, most preferably less than, and not including, 10 wt%.

4. The method according to any one of the previous claims, wherein no free water is added in steps a) to d).

5. The method according to any one of claims 1-4, wherein the non-aqueous fluid further comprises at least one of a Cuo alcohol, a bio-oil, C1-30 hydrocarbon, ether, alkyl acetate, ketone, sulfolane, a fluid stream recycled from hydroprocessing, or any combination thereof.

6. The method according to claim 5, wherein the Cuo alcohol is selected from methanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, glycerol, propylene glycol, cresol, resorcinol, hydroquinone, guaiacol, catechol, phenol, or benzyl alcohol, preferably methanol or ethanol, or any combination thereof.

7. The method according to any one of claims 1-6, wherein the non-aqueous fluid comprises at least 5 wt% ethanol.

8. The method according to any one of claims 1-7, wherein the base further comprises a strong base selected from sodium sulphide, sodium hydroxide, barium hydroxide, calcium hydroxide, caesium hydroxide, lithium hydroxide, rubidium hydroxide, or strontium hydroxide; preferably sodium sulphide, or sodium hydroxide; or any combination thereof.

9. The method according to any one of claims 1-8, wherein the base further comprises a superbase selected from organometallic or inorganic compounds, such as a Grignard reagent; hydrides of alkali-metals, such as lithium hydride, or sodium hydride; combinations of organolithium compounds with alkali metal alkoxides, such as n-butyllithium and potassium tert-butoxide; phosphazenes, e.g.Schwesinger phosphazenes; proazaphosphatranes, such as Verkade proazaphosphatranes; phosphines; amidines; such as Schwesinger vinamidines; guanidines or metal amides, such as lithium diisopropylamide; or any combination thereof.

10. The method according to any one of claims 1-9, wherein the mixture subjected to thermal treatment in step d), comprises 5-50 wt% lignin, 1-35 wt% base, and 30-94 wt% of a non-aqueous fluid up to a maximum or a total of 100 %, as calculated on the total weight of the mixture.

11. The method according to any one of claims 1-10, wherein in any of steps b) and f) or both, a bio-oil is added, which is independently selected from a lignin oil recycled from the process comprising the method of claim 1, tall oil pitch, crude tall oil, pyrolysis oil, lignin oil, hydrothermal liquefaction oil, turpentine, vegetable oil, or an oil obtained from any one of softwood, hardwood, bagasse, bark, sawdust, other types of forest biomass grass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, aquaculture residues, animal residues, agriculture raw materials, agriculture residues, or any combination thereof.

12. The method according to any one of claims 1-11, wherein the temperature in step d) is from 120 to 245 °C.

13. The method according to any one of claims 1-12, wherein the mixture in step d) is subjected to the desired temperature gradually, continuously, or in several stages over a period of time, whereupon any water present is removed.

14. The method according to any one of claims 1-13, further comprising a step of removing salts from the liquid comprising lignin oil obtained in step e), preferably by filtration.

15. The method according to claim 14, wherein step e) further comprises washing the precipitated salt with ethanol.

16. The method according to any one of claims 1-15, wherein any of the acids added in step e) and f) is independently a strong acid, preferably independently selected from sulfuric acid, hydrochloric acid, or nitric acid.

17. The method according to any one of claims 1-16, wherein steps f)-h) are repeated at least once.

18. The method according to any one of claims 1-15, wherein the lignin oil is subjected to the hydroprocessing in step j), to obtain fuel or chemicals.

19. The method according to any one of claims 1-18, wherein a solvent selected from a water insoluble C4-6 alcohol, ethers, alkyl acetate, a liquid stream recycled from the hydroprocessing step, or mixtures thereof, is added during step f).

20. The method according to any one of claims 1-19, wherein the demetallized lignin oil has a total metal content of less than 20 ppm, preferably of from 0 to 10 ppm, and a total phosphorus content of less than 10 ppm, preferably of from 0 to 5 ppm.

21. A lignin oil obtainable by the method according to any one of claims 1-20, wherein at least 75 wt%, preferably at least 50 wt%, of the lignin oil boils below 440 °C.

22. A lignin oil having a total metal content of from 0 to 20 ppm, even more preferably of from 0 to 10 ppm; and a total phosphorus content of less than 10 ppm, preferably of from O to 5 ppm.

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