A METHOD FOR THE PRODUCTION OF A BIO-OIL
The present invention relates to a method for providing a bio-oil from biomass, wherein the method comprises the steps of:—adding a biomass with a lignin content of from 0 to 40 wt %;—adding a non-aqueous fluid;—adding a base comprising potassium N ions;—subjecting the mixture to thermal treatment at a temperature of from 100° C. to 320° C. to obtain a liquid comprising bio-oil;—adding an acid to precipitate salts;—subjecting the liquid comprising bio-oil to a temperature of from 10° C. to 320° C. to obtain a mixture comprising an aqueous phase and a bio-oil; and—removing the aqueous phase from the mixture to obtain a demetallized bio-oil;—whereby the demetallized bio-oil obtained has a total metal content of less than 200 ppm, and a total phosphorus content of less than 10 ppm.
The present invention relates to a method for the production of a bio-oil from a biomass, and the bio-oil obtained by the method.
TECHNICAL BACKGROUNDThe 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 Gm3 per 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).
Lignocellulosic materials are more complex and difficult to process than are sugars and vegetable oils, and thus, cannot be economically converted into biofuels and biochemicals by the currently available technologies. A biorefinery needs flexibility to process a variety of feedstocks with seasonal availability, so the process must tolerate a wide range of feed compositions.
A major barrier to the efficient conversion of lignocellulosic materials to biofuels is liquefaction of the raw materials at high yields. The most prominent methods currently in use for the production of bio-oils from lignocellulosic materials are hydrothermal liquefaction and pyrolysis.
Hydrothermal liquefaction (HTL) processes typically operate at high temperatures and pressures, 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 biomass 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.
Complete dissolution of the biomass 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.
A challenge for the production of biofuels and biochemicals from lignocellulosic biomass materials 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 A1 was effective for reducing phosphorus but not potassium.
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.
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.
It is desirable to reduce both the content of phosphorus and metals such as aluminium, calcium, magnesium, manganese, phosphorus, potassium, and sodium of the bio-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 bio-oil, as opposed to, for example, removal of fractions of the bio-oil containing high levels of metals prior to hydroprocessing.
As is apparent from the above, there is still a need for an improved method for efficient liquefaction of biomass and reduction of the metal content in bio-oils.
SUMMARY OF THE INVENTIONAn object of the present invention is to provide a method for the production of a bio-oil. A further object is to provide a bio-oil with a low metal content. The bio-oil provided is flowable and is a suitable feedstock for hydroprocessing into fuels or chemicals.
The present invention is a feedstock-flexible process that converts biomass with a lignin content of up to about 40 wt % into bio-oils that are suitable for further refining into fuels or chemicals by means such as hydroprocessing.
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.
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 bio-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 bio-oil.
Complete conversion of biomass into its constituent monoaromatic compounds is not required or even desired. Rather, a production of a bio-oil without char formation maximizes yield and provides flexibility for downstream use. This enables fuel and chemicals with a range of molecular weights to be produced.
The method of the present invention provides a bio-oil having a long boiling temperature range, wherein the bio-oil comprises high boiling fractions. This is an advantage as it provides flexibility as to the end products to be obtained from the bio-oil.
The method and the bio-oil according to the present invention are defined in the appended claims.
List of DefinitionsHydroprocessing: 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.
Hydrotreating: a catalytic process for the removal of heteroatoms from chemicals, bio-gas, 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.
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).
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.
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.
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.
Hydrofinishing: a final hydrotreating step after hydrocracking and/or hydrotreating that improves the colour and oxidation stability of the product.
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.
Shape-selective hydrocracking: hydrocracking using shape-selective catalysts.
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.
In a first aspect, the present invention relates to method for providing a bio-oil, comprising the steps of:
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- a) adding a biomass with a lignin content of from 0 to 40 wt %;
- b) adding a non-aqueous fluid;
- 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 the biomass, the base, and the non-aqueous fluid to thermal treatment at a temperature of from 100° C. to 320° C., preferably of from 110 to 280° C., more preferably of from 120 to 240° C.; to obtain a bio-oil;
- e) adding an acid to the liquid comprising bio-oil to precipitate 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 bio-oil obtained to obtain a mixture;
- g) subjecting the bio-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 bio-oil;
- h) removing the aqueous phase from the second mixture to obtain a demetallized bio-oil;
- i) optionally repeating steps f)-h); and
- j) optionally subjecting the demetallized bio-oil to hydroprocessing;
- whereby the demetallized bio-oil obtained has a total metal content of less than 200 ppm, preferably of from 0 to 50 ppm, and a total phosphorus content of less than 10 ppm.
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).
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 when step f) is performed for the first time, and when repeated, water without acid is added.
All aspects and embodiments disclosed herein can be combined with any other aspect and/or embodiment disclosed herein.
The term “biomass”, as used herein, does not comprise animal-based biomass. Algae is defined herein as non-animal-based biomass. The biomass used in the present invention may originate from agriculture, aquaculture, food industry, forest, forest industry, grassland, or any combination thereof. The biomass is preferably originating or selected from softwood, hardwood, other types of forest biomass, straw, bagasse, grass, algae, seagrass, seaweed, cones, needles, leaves, bark, nutshell, fruit kernel, husk, corn stover, agriculture residues, or food industry residues, or any combination thereof. The biomass may have been processed. Such processing may constitute pre-cooking, such as with a base.
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.
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; 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.
In one embodiment the biomass comprises from 0.1 to 99 wt % of carbohydrates as calculated on total dry weight of the biomass. In one embodiment the biomass comprises lignin at a level of from 0.1 to 40 wt %, as calculated on total dry weight of the biomass. The lignin content 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.
The term “fluid” is used herein for gases as well as liquids.
The method according to the present invention provides a bio-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.
In one embodiment the biomass, or the mixture of biomass and non-aqueous fluid, has a water content of from 0.1 to 65 wt %, preferably from 0.5 to 45 wt %, more preferably from 1 to 40 wt %, as calculated on the total weight of the biomass.
In one embodiment the biomass provided in a) is subjected to steam explosion to obtain wood pellets or black pellets with a water content of from 5 to 12 wt %, preferably from 5 to 10 wt %, more preferably from 5 to, and not including, 10 wt %. The steam explosion may be performed at a temperature of 150-220° C. The biomass may be dried by heating or pressing.
In one embodiment, the non-aqueous fluid comprises C1-10 alcohol, C1-30 hydrocarbon, or a bio-oil, an ether, an alkyl acetate, a ketone, sulfolane, a fluid stream recycled from a hydroprocessing step, or any combination 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 C1-10 alcohol.
In a preferred embodiment, the non-aqueous fluid comprises methanol, ethanol, n-propanol or iso-propanol, or a combination of two or more thereof.
In one embodiment the non-aqueous fluid further comprises an additional C1-10 alcohol, C1-30 hydrocarbon, or a bio-oil, an ether, an alkyl acetate, a ketone, sulfolane, a fluid stream recycled from a hydroprocessing step, or any combination thereof, in addition to methanol, ethanol, n-propanol or iso-propanol.
In one embodiment the additional C1-10 alcohol comprises methanol, ethanol, 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 additional C1-10 alcohol has a boiling point of from 50 to 250° C. In some embodiments, the additional C1-10 alcohol is selected from butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, glycerol, propylene glycol, cresol, resorcinol, hydroquinone, guaiacol, catechol, phenol, or benzyl alcohol; or any combination thereof. More preferably the additional C1-10 alcohol is selected from guaiacol, catechol, phenol, or benzyl alcohol. 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.
In a preferred embodiment the non-aqueous fluid comprises at least 5 wt % ethanol. The non-aqueous liquid may comprise up to 100 wt % ethanol. Ethanol is a good solvent for the oil obtained during the liquefaction. The recovery of methanol or ethanol is relatively energy-efficient in comparison with other solvents, and distillation may be performed at relatively low temperature. The use of ethanol also facilitates precipitation and washing of potassium sulphate and other sulphate salts when a sulfuric acid is added in step e). Consequently, the use of ethanol is preferred when precipitating salt, while other alcohols may be used earlier in the process, i.e., during liquefaction of the biomass and/or lignin (i.e. steps a) to d) as disclosed herein). Ethanol may also dissolve both hydrophobic and hydrophilic molecules. In addition, ethanol is an excellent solvent for purifying the precipitated salt, as it washes away the bio-oil and organic compounds remaining in the precipitated salt without dissolving the salt.
In one embodiment the non-aqueous fluid added in step b) comprises a C1-30 hydrocarbon or a mixture of C1-30 hydrocarbons. Preferably, the C1-30 hydrocarbon is a saturated hydrocarbon, more preferably a C1-30alkane, 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.
In one embodiment the non-aqueous fluid added in step b) comprises a bio-oil. The bio-oil added as a non-aqueous fluid in step b) or the bio-oil added in step f) is each independently preferably selected from a bio-oil recycled from a process comprising the method according to the present invention; tall oil pitch (TOP); 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, grass, algae, seagrass, seaweed, agriculture raw material, such as agriculture residues, aquaculture residues, animal residues, or food industry residues; or any combination thereof. In one embodiment, vegetable oils are excluded as the non-aqueous fluid. A reason for this is not to compete with resources from food industry. Examples of vegetable oils excluded are agai 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, jamby 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, tucum5 oil, and walnut oil. More preferably, the bio-oil added as a non-aqueous fluid in step b) or the bio-oil added in step f) is each independently selected from a bio-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, or food industry residues; or any combination thereof.
In one embodiment, the non-aqueous fluid comprises a bio-oil that is recycled from the process disclosed herein. The bio-oil recycled from the process may further contain alcohols produced in the liquefaction process, such as methanol, ethanol, propanol, guaiacol, catechol and other phenolic alcohols, such as phenol, or benzyl alcohol. Said alcohols, once recycled, contribute to dissolving biomass added to the process and may also serve as capping agents. In one embodiment, the non-aqueous fluid comprises at least 5 wt % of said alcohols, thus reducing the viscosity of the bio-oil, thereby improving processability.
Liquefaction of biomass can be carried out in the presence of a catalyst to aid in the depolymerization of lignin and suberin, as well as decomposition of cellulose and hemicellulose. Base-catalyzed depolymerization of lignin and suberin, suppresses repolymerization and char formation during liquefaction and thus is favoured over acid-catalyzed depolymerization. Complete dissolution of the biomass without char formation is desirable in order to maximize the yield of the process.
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 potassium hydroxide, to a mixture comprising biomass and an alcohol, such as methanol, 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 biomass to bio-oil. Alternatively, a potassium alkoxide in an alcohol solution, such as potassium ethoxide in ethanol solution, can be added to the biomass.
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.
Too small amounts of potassium in relation to the amount of biomass will not give 100% liquefaction. 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 moisture content of the base used must be taken into account.
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 bio-oil, as well as deactivation of the heterogeneous catalyst.
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.
In one embodiment the base added in step c) further comprise a strong base 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 further added in step c) is preferably selected from sodium sulphide, or sodium hydroxide, or any combination thereof.
In one embodiment the base added in step c) further comprise a superbase. 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, potassium 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 C1-6 alkoxides, such as sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide, or potassium tert-butoxide.
In one embodiment, the mixture subjected to thermal treatment in step d) comprises 5-50 wt % biomass, 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. Preferably, the mixture comprises 8-40 wt % biomass, 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 % biomass, 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.
Conversion of the biomass includes the liquefaction of solids, reduction of the viscosity of the resulting bio-oil, and reduction of the final boiling point of the bio-oil, and occurs via base-catalyzed depolymerization of biomass components, such as lignin and suberin, as well as decomposition of polysaccharides such as cellulose and hemicellulose.
By dispersing the biomass 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 conversion of the biomass. 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 during liquefaction, 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 biomass.
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 biomass has been liquefied.
In one embodiment, the mixture in step d) has a total water content of from 1 to 20 wt %, preferably from 2 to 15 wt %, before the mixture is subjected to the thermal treatment.
By thermal treatment at a temperature of from 100° C. to 320° C., preferably of from 110° C. to 280° C., more preferably of from 120° C. to 240° C.; during a time period of from 0.5 to 360 min, from 1 to 360 min, from 5 to 300 min, from 16 to 300 min, from 16 to 240 minutes, from 16 to 200 minutes, or from 30 to 180 minutes, in step d), a liquid comprising bio-oil is provided without involving any extraction of solid materials.
In one embodiment, the temperature in step d) is from 100 to 245° C., preferably of from 120 to 240° C., more preferably of from 140 to 235° C.
The yield of the resulting bio-oil depends on the temperature applied. At a temperature of 240° C. the yield is already 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.
The time period required to convert the biomass to a bio-oil depends on the temperature of the mixture, i.e. the biomass, base, and non-aqueous fluid. The time for the thermal treatment in step d) is preferably long enough to provide heat uniformity. Achieving a certain extent of conversion requires shorter time periods when using higher temperatures. The required time period also depends on the temperature that the components, i.e. the biomass, base, and non-aqueous fluid, have when they are added to the mixture.
As used herein, 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 temperature during the thermal treatment in step d) may be changed gradually, continuously, or in several heating stages over a period of time. Preferably, the thermal treatment is performed with two heating stages. The desired temperature may be reached by using pre-heated biomass, or pre-heated non-aqueous fluid, or pre-heated base, from any of the previous steps a) to c); and/or by heating in step d).
When performing several heating stages, the biomass may be liquefied during any or all of the first heating stage(s), with biomass conversion being performed to the desired extent during the final heating stage(s). 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 biomass liquefaction. Water, when present, may be removed by distillation, evaporation or by liquid-liquid extraction.
The thermal treatment in step d) may be performed at conditions where the non-aqueous 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.
In one embodiment, wherein during the thermal treatment in step d), the mixture is subjected to at least one temperature in the range from 130° 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 320° 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 30 to 180 minutes, and the second heating stage lasts for a time period of from 30 to 120 minutes.
The liquefaction process of steps a)-d) may be performed 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 using a heated vessel, multitube heat exchangers, or any combination 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 pre-heated non-aqueous fluid(s), may be added between stages of liquefaction.
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 biomass and/or lignin to the reactor.
In one embodiment, any solids remaining from the biomass are removed from the bio-oil obtained in step d). Preferably, such biomass solids are removed from the bio-oil obtained before the second heating stage in step d). The removed solids may be used for sugar production or as a pulp material.
An acid, preferably a strong acid, e.g., hydrochloric acid, sulfuric acid, or nitric acid, added in step e) 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 removal of the precipitated salts from the bio-oil. The precipitated salts are preferably removed by filtration. Removal of salts produces a higher quality bio-oil, while at the same time allowing the salts to be used for other purposes, e.g. as fertilizer.
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 C1-10 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.
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.
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 bio-oil, from the salt. The bio-oil washed away from the salt may be pooled with the bio-oil obtained in the liquefaction step, thereby providing a higher overall bio-oil yield.
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 bio-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.
The bio-oil obtained in step e), is subjected to demetallization, preferably by acid treatment. Demetallization provides for the removal of metals from the bio-oil. Demetallization of the bio-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 bio-oil obtained in step d) to obtain a mixture. The obtained bio-oil, or the mixture comprising the obtained bio-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 bio-oil, followed by removal of the aqueous phase to obtain a demetallized bio-oil. The entire process of liquefaction and demetallization may be performed continuously or batchwise. The latter would minimize the required equipment.
In one embodiment of step f), the added bio-oil is dispersed in a solvent. The dispersion of the added bio-oil may be performed either before or after any 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.
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.
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 organic acid, 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 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.
The contents of steps a)-c) and f) may be mixed by any suitable mixing method to obtain the mixture.
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.
The desired temperature in step g) may be reached by using pre-heated bio-oil, pre-heated 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 step g) is carried out for the first time, the temperature is from 120° C. to 200° C., more preferably of from 140° C. to 200° C., and not including 200° C., even more preferably from 150 to 200° C., and not including 200° C., or most preferably of from 150 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 and lower temperatures may be used, such as from 10° C. to 200° C. The temperature used depends on the composition of the bio-oil, whereby the temperature used shall be sufficient for phase separation. When the biomass does not contain phospholipids, lower temperatures, such as from 10° C. to 200° C., may be used the first time step g) is carried out.
A higher temperature 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.
When steps are repeated, lower temperatures may be used in subsequent repetitions than originally used. 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 bio-oil without increasing the temperature.
The mixture of step f) may be subjected to the desired temperature 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 from 0.01 to 10 minutes.
After heat treatment in step g) a mixture comprising an aqueous phase and a bio-oil is obtained. The aqueous phase may have been formed by dehydration reactions or derive from the water content of the biomass, an aqueous solution of the base added i step c) or the acid added in step e), and/or addition of water in the optional step f).
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, the 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.
Removal of the aqueous phase from the bio-oil is critical for the removal of metals from the bio-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 any combination of these; electrical means, such as electrostatic desalting units; chemical means, such as addition of an emulsion breaker; or by any 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. The removal of the aqueous phase in the method disclosed herein does not involve the use of enzymes.
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.
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 bio-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.
In one embodiment, after removal of the aqueous phase in step h) using a decanter, the bio-oil is subjected to centrifugation to remove any remaining water.
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 repetition of step f) reduces the corrosivity of the demetallized bio-oil in downstream processing, thus without needing a base for neutralization. Addition of a base to the demetallized bio-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.
The aqueous phase 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 the first time or times step f) is carried out, and fresh water is used when step f) is repeated, at least once. Using demineralized water in the final execution of step f) ensures that no metals are introduced to the bio-oil from the wash water.
Residual water, when present in the demetallized bio-oil, may be removed by distillation, evaporation, membrane separation, liquid-liquid extraction, or by any other suitable method. The obtained demetallized bio-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 %.
In one embodiment the demetallized bio-oil obtained in step h) is subjected to further treatment, such as hydroprocessing, to obtain fuels or chemicals.
Hydroprocessing of the bio-oil may comprise passing the bio-oil through a guard bed, followed by hydrotreating and optionally, mild hydrocracking and/or hydrodewaxing, and lastly, hydrofinishing the bio-oil with various catalysts. Fractionation is performed to obtain the product fuel and/or chemicals. Hydroprocessing, hydrotreatment, hydrocracking, hydrodewaxing, hydrofinishing and fractionation are concepts well known to the skilled person.
In another aspect, the present invention relates to a bio-oil obtained by the method according to the present invention.
In a further aspect, the present invention relates to a bio-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. As used herein the total metal content preferably refers to the content of metal selected from aluminium, calcium, magnesium, manganese, phosphorus, potassium, and sodium.
In one embodiment, the bio-oil has a total metal content of less than 20 ppm, from 0.01 to 20 ppm, preferably of from 0.01 to 10 ppm; and the total phosphorus content is from 0.01 to 10 ppm or from 0.01 to 5 ppm.
In one embodiment the bio-oil has a total metals 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.
In one embodiment, the bio-oil obtainable with the method according to the present invention, has a Final Boiling Point (FBP) below 700° C., preferably below 660° C., more preferably below 640° C.
Preferably, at least 50 wt %, or at least 75 wt % of the demetallized bio-oil boils below 440° C.
The present invention is 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 person skilled in the art. Unless otherwise stated, parts and percentages as used herein are parts by weight and weight percent.
EXAMPLES Examples 1-7 Liquefaction of Biomass:60 g biomass, 60 g of a base, and 280 g of a non-aqueous fluid were added to an autoclave. The mixture was heated to a first temperature, T1, and held at this temperature with stirring for a time, t1. Subsequently, the temperature was increased to a second temperature, T2, and kept at this level for a time, t2, while stirring. A liquid comprising an oil-phase was obtained. The results are presented in Table 1.
For each one of the Examples 1-5 of Table 1, 100% liquefaction was achieved and no char formation was observed in the obtained bio-oil. Examples 6-7, catalysed by NaOH, still contained unreacted material with visible particles remaining in the obtained bio-oil.
Acidification and Salt SeparationFor each one of the Examples 1-5 where 100% liquefaction was achieved, acidification and salt separation were performed according to the following procedure: 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 precipitation was filtrated over a 22 μm retention filter paper in a Büchner funnel. The precipitated salt formed a filter cake on the filter paper. The precipitated salt was rinsed with ethanol. The ethanol was removed from the filtrate comprising the bio-oil using a rotary evaporator.
Example 8 Demetallization100 mL of bio-oil obtained in Example 1 was added to an autoclave. Sulfuric acid in water (100 mL, pH 1) was added to the bio-oil. The mixture was stirred while heated to about 170° C. After the target temperature was reached, the stirring was turned off, and the two phases were given 30 minutes to separate. After the contents in the autoclave had cooled to 90° C., for ease of handling, the contents were transferred to a separation funnel. 50 mL of butanol and 50 mL of 2-methyl tetrahydrofuran were added to the bio-oil sample. An aqueous phase and an oil phase were collected. The water and butanol were boiled off using a rotary evaporator, leaving the isolated bio-oil.
ResultsSimulated distillation of the demetallized bio-oil was done by gas chromatography (EN 15199-1), whereby the entire sample was vaporized and exited the column, showing that no solids were present. The simulated distillation of the bio-oil in Example 1 is shown in
Elemental analysis of the resulting bio-oil was made by a LECO CHN elemental analyzer using a combustion method and the results are shown in Table 2.
The metal contents of the bio-oil and the demetallized bio-oil were analyzed using inductively coupled plasma mass spectroscopy (ICP SCAN CM-38) and the results are shown in Table 3.
Claims
1. A method for providing a demetallized bio-oil, comprising the steps of:
- a) starting with a biomass with a lignin content of from 0 to 40 wt %;
- b) adding a non-aqueous fluid;
- c) adding a base comprising potassium ions, thereby obtaining a mixture comprising the biomass, the base, and the non-aqueous fluid;
- d) subjecting the mixture comprising the biomass, the base, and the non-aqueous fluid to thermal treatment at a temperature of 100° C. to 320° C. to obtain a liquid comprising bio-oil;
- e) adding an acid to the liquid comprising bio-oil to precipitate 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 bio-oil of step e) to obtain a mixture;
- g) subjecting the liquid obtained in step e), or the mixture obtained in step f), to a temperature of from 10° C. to 320° C. to obtain a second mixture comprising an aqueous phase and a bio-oil;
- h) removing the aqueous phase from the second mixture to obtain a demetallized bio-oil;
- i) optionally repeating steps f)-h); and
- j) optionally subjecting the demetallized bio-oil to hydroprocessing;
- whereby the demetallized bio-oil obtained has a total metal content of less than 200 ppm and a total phosphorus content of less than 10 ppm.
2. The method according to claim 1, wherein the temperature in step d) may be changed gradually, continuously, or in several stages over a period of time, whereupon any water present is removed.
3. The method according to claim 2, wherein during the thermal treatment the mixture in step d) is subjected to at least one temperature in the range from 130° 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 320° C. in a second heating stage.
4. The method according to claim 3, wherein the temperature of the second heating stage is higher than the temperature of the first heating stage.
5. (canceled)
6. The method according to claim 1, wherein the mixture in step d) has a total water content of from 1 to 20 wt % before the mixture is subjected to the thermal treatment.
7. The method according to claim 1, wherein the amount of potassium ions to Moisture and Ash Free (MAF) biomass is at least 0.2:1 by weight.
8. (canceled)
9. The method according to claim 1, wherein the biomass, or the mixture of biomass and non-aqueous fluid, has a water content of from 0.1 to 65 wt %.
10. The method according to claim 1, wherein no free water is added in steps a) to d).
11. The method according to claim 1, wherein the non-aqueous fluid comprises methanol, ethanol, n-propanol or iso-propanol, or a combination of two or more thereof.
12. (canceled)
13. (canceled)
14. The method according to claim 1, 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, or any combination thereof.
15. The method according to claim 1, wherein the base further comprises a superbase selected from an organometallic or inorganic compound, a Grignard reagent, a hydride of an alkali-metal, lithium hydride, odium hydride, a combination of an organolithium compound with an alkali metal alkoxide, n-butyllithium and potassium tert-butoxide, a phosphazene, a proazaphosphatrane, a phosphine, an amidine, a Schwesinger vinamidine, a guanidine, a metal amide, lithium diisopropylamide; or any combination thereof.
16. (canceled)
17. The method according to claim 3, wherein biomass solids are removed from the bio-oil obtained before the second heating stage in step d).
18. (canceled)
19. (canceled)
20. The method according to claim 1, wherein the temperature in step d) is from 100° C. to 245° C.
21. The method according to claim 1, wherein any of the acids added in step e) and optional step f) are independently selected from a strong acid, sulfuric acid, hydrochloric acid, or nitric acid.
22. The method according to claim 1, further comprising removal of salts from the liquid comprising the bio-oil obtained in step e).
23. The method according to a claim 1, wherein the precipitated salt is washed with a washing liquid.
24. (canceled)
25. The method according to claim 1, wherein steps f)-h) are repeated at least once.
26. The method according to claim 1, wherein the demetallized bio-oil is subjected to the hydroprocessing in step j), to obtain fuel or chemicals.
27. The method according to claim 1, wherein a solvent selected from a water insoluble C4-6 alcohol, ethers, alkyl acetates, a liquid stream recycled from the hydroprocessing step, or mixtures thereof, is added during step f).
28. (canceled)
29. A demetallized bio-oil obtainable by the method according to claim 1, wherein at least 50 wt % of the demetallized bio-oil boils below 440° C.
30-32. (canceled)
Type: Application
Filed: Dec 13, 2023
Publication Date: Jul 16, 2026
Inventor: Anders EDLING HULTGREN (Sundsvall)
Application Number: 19/133,499
