US20180265794A1

US20180265794A1 - Continuous production of fuel grade hydrocarbons by hydrotreatment of forestry byproduct lignin

Info

Publication number: US20180265794A1
Application number: US15/762,086
Authority: US
Inventors: Christian DAHLSTRAND; Joseph Samec
Original assignee: Ren Fuel K2B AB
Current assignee: Ren Fuel K2B AB
Priority date: 2015-09-22
Filing date: 2016-09-21
Publication date: 2018-09-20
Also published as: SE1551213A1; EP3353269A1; WO2017052454A1

Abstract

The present invention relates to a composition and a method of preparing the composition where the composition comprises lignin dissolved in depolymerized lignin obtained from hydrotreatment of lignin. The method may be operated in batch mode or in a continuous mode but there is no need to add any oil.

Description

FIELD OF THE INVENTION

The present invention relates to a composition and a method of preparing the composition where the composition comprises lignin dissolved in lignin derived hydrotreated compounds. The method may be operated in batch mode or in a continuous mode but there is no need to add any mineral oil.

BACKGROUND

There is an increasing interest in using biomass as a source for fuel production. Biomass includes, but is not limited to, plant parts, fruits, vegetables, processing waste, wood chips, chaff, grain, grasses, com, com husks, weeds, aquatic plants, hay, paper, paper products, recycled paper and paper products, lignocellulosic material, lignin and any cellulose containing biological material or material of biological origin.
An important component of biomass is the lignin present in the solid portions of the biomass. Lignin comprises chains of aromatic and oxygenate constituents forming larger molecules that are not easily treated. A major reason for the difficulty in treating the lignin is the inability to disperse or dissolve the lignin for contact with catalysts that can break down the lignin.
Lignin is one of the most abundant natural polymers on earth. One common way of preparing lignin is by separation from wood during pulping processes. Only a small amount (1-2%) is utilized in specialty products whereas the rest primary serves as fuel. Even if burning lignin is a valuable way to reduce usage of fossil fuel, lignin has significant potential as raw material for the sustainable production of chemicals and liquid fuels.
Various lignins differ structurally depending on raw material source and subsequent processing, but one common feature is a backbone consisting of various substituted phenyl propane units that are bound to each other via aryl ether or carbon-carbon linkages. They are typically substituted with methoxyl groups and the phenolic and aliphatic hydroxyl groups provide sites for e.g. further functionalization.
Today lignin may be used as a component in for example pellet fuel as a binder but it may also be used as an energy source due to its high energy content. Lignin has higher energy content than cellulose or hemicelluloses and one gram of lignin has on average 22.7 KJ, which is 30% more than the energy content of cellulosic carbohydrate. The energy content of lignin is similar to that of coal. Today, due to its fuel value lignin that has been removed using the kraft process, sulphate process, in a pulp or paper mill, is usually burned in order to provide energy to run the production process and to recover the chemicals from the cooking liquor.
There are several ways of separating lignin from black or red liquor obtained after separating the cellulose fibres in the kraft or sulphite process respectively, during the production processes. One of the most common strategies is ultra-filtration. Lignoboost® is a separation process developed by Innventia AB and the process has been shown to increase the lignin yield using less sulphuric acid. In the Lignoboost® process, black liquor from the production processes is taken and the lignin is precipitated through the addition and reaction with acid, usually carbon dioxide (CO₂), and the lignin is then filtered off. The lignin filter cake is then re-dispersed and acidified, usually using sulphuric acid, and the obtained slurry is then filtered and washed using displacement washing. The lignin is usually then dried and pulverized in order to make it suitable for lime kiln burners or before pelletizing it into pellet fuel.
Biofuel, such as biogasoline and biodiesel, is a fuel in which the energy is mainly derived from biomass material or gases such as wood, corn, sugarcane, animal fat, vegetable oils and so on. However the biofuel industries are struggling with issues like food vs fuel debate, efficiency and the general supply of raw material. At the same time the pulp or paper making industries produces huge amounts of lignin which is often, as described above, only burned in the mill. Two common strategies for exploring biomass as a fuel or fuel component are to use pyrolysis oils or hydrogenated lignin.
In order to make lignin more useful as a source for fuel production one has to solve the problem with the low solubility of lignin in organic solvents. One drawback of using lignin as a source for fuel production is the issue of providing lignin in a form suitable for hydrotreaters or crackers. The problem is that lignin is not soluble in oils or fatty acids which is, if not necessary, highly wanted.
Prior art provides various strategies for degrading lignin into small units or molecules in order to prepare lignin derivatives that may be processed. These strategies include hydrogenation, dexoygenation and acid catalyst cleaving. WO2011003029 relates to a method for catalytic cleavage of carbon-carbon bonds and carbon-oxygen bonds in lignin. US20130025191 relates to a depolymerisation and deoxygenation method where lignin is treated with hydrogen together with a catalyst in an aromatic solvent. All these strategies relates to methods where the degradation is performed prior to eventual mixing in fatty acids or gas oils. WO2008157164 discloses an alternative strategy where a first dispersion agent is used to form a biomass suspension to obtain a better contact with the catalyst. These strategies usually also requires isolation of the degradation products in order to separate them from unwanted reagents such as solvents or catalysts.
The direct treatment of lignin at present day refineries has not yet been realized. This has mainly to do with compatibility issues as the physical properties of lignin are very different as compared to the standard refinery oil feeds.
Producing pyrolysis oils or synthesis gas from biomass is however possible and has been done both in Sweden and elsewhere. The production can be via pyrolysis of black liquor or biomass in an oil based slurry. However, refineries cannot handle the corrosive pyrolysis oils and the syngas products methanol, which is poisonous, and dimethyl ether (DME), which is gaseous, cannot be used in currents automobile engines.
A variety of fats and greases derived from biomass have already found their way into everyday fuels (Hydrogenated vegetable oil (HVO)). Some of the companies that actively use these raw materials are Preem (Evolution Diesel®), Neste (NexBTL®), and ENI (Ecofining™ process). The use of tall oil is not controversial as it is a forestry byproduct. Use palm oil in the production of “green” fuels has received unwanted attention from Green Peace because palm oil is associated with the destruction of the rainforests. ENI uses first generation vegetable oils in their production of green fuels, however, their feedstock production clashes with the production of food.
When focusing on the lignin part of biomass there are several different strategies for producing liquid fuels. One of the main strategies to make a feedstock for oil refineries is to perform lignin depolymerization. However, many of the monomeric lignin units generated in this way are not soluble in standard refinery carrier oils, as shown in WO2014116173. An alternative strategy is through lignin hydrotreatment. Much of the research into lignin hydrotreating has been focused on lignin model compounds. The few reports where actual lignin is used show that lignin can be hydrotreated in the presence of conventional catalysts in a batch setup under solvent-free conditions or with solvent. Solvent-free conditions may be problematic to use for continuous industrial hydrotreatment as the lignin powder would need to be transported into a reactor at high gas pressures. However, using methanol, a report shows that “under optimal reaction conditions, the main products are alkylphenolics and gratifyingly no ring hydrogenation or char formation takes place”.
Today only the HVO is believed to have successfully been commercialized as fuel. The feedstock limitations (tall oil) or the detrimental environmental effects (palm oil) will continue to be issues for the production of green fuels from biomass oils. There is a need to find reliable, economical ways to use renewable biomass to produce liquid fuels. One such way has been developed by RenFuel AB. They convert lignin into a lignin oil, Lignol® which is soluble in gas oils for example used for hydrotreating.
An alternative procedure for making liquid fuels is by performing hydrotreatment of solid lignin dispersed in hydrocarbon oil. U.S. Pat. No. 7,994,375 discloses a method of converting biomass such as lignin into liquid fuel. The method comprises forming a slurry of lignin and a carrier oil (Tall oil for example) which is hydrotreated into diesel or naphtha boiling range products. The disclosed process aims at fully deoxygenate the lignin. There are however some obvious issues with having a slurry, including sedimentation, pumping problems and loss in reactivity. Also the catalyst activity may be hampered by the large slurry particles. Using hydrotreated pyrolysis oil as a carrier liquid comes with the problem of corrosion since pyrolysis oils have a pH of 2-3 which may result in release of metals which in turn damage the catalysts.
GB2104545 discloses a process where a slurry of lignin is treated in a hydrocracking reactor. The process results in an oil (slurrying oil) which is mixed with the lignin to prepare a pumpable slurry mixture. The slurry mixture is then introduced into a cracking reactor where the catalyst is provided in particulate form. A problem with using a slurry is that a fixed bed catalyst cannot be used and it is only the lignin in solution that is hydrotread i.e. the particulate lignin is not or only poorly hydrotreated.
Some of the problems associated with the hydrotreatment of lignin which need solving to become industrially interesting are:

- Lignin does not significantly dissolve in carrier liquids
- Expensive to use standard solvents as carrier liquids, i.e. methanol
- Using vegetable oils is too often associated with either destruction of rainforest to produce palm oil or competition with food to produce vegetable oils.

SUMMARY OF THE INVENTION

The aim of the present invention is to overcome the drawbacks of the prior art and provide a composition comprising lignin and depolymerized. The present invention further aims at presenting a novel method of preparing green light products. One application for the composition may be as a raw material for fuel production (e.g. petrol or diesel) or as an additive to fuel or oil or as a starting material for the chemical industry.
Enabling the use of a fixed bed reactor will solve many issues as the lignin will contain relatively high amounts of metals, as compared to a distilled mineral oil, the reactor might need a guard bed. As a consequence of the high oxygen content in lignin the fixed bed reactor can handle the exothermic reaction of water formation by having low activity on the first bed followed by beds with more active catalyst. In addition the fully dissolved lignin enables the use of lower temperature and lower hydrogen pressure as compare to having the lignin in a slurry. Furthermore by dissolving the lignin in a carrier liquid or in suitable solvents commercially available and standard hydrotreater reactors and system may be used to treat the lignin instead of specifically designed hydrotreaters.
In a first aspect the present invention relates to composition as defined in claim 1.
In a second aspect the present invention relates to method of preparing the composition according to the present invention wherein the method comprises:

- a. providing a first feed of lignin wherein the feed is a liquid;
- b. hydrotreating the lignin forming a first product stream comprising light compounds and depolymerized lignin;
- c. removing the light compounds from the first product stream leaving a second product stream comprising depolymerized lignin;
- d. providing a second feed of lignin; and
- e. mixing the second product stream with the second feed of lignin.

In a third aspect the present invention relates to an intermediate composition comprising lignin at least partly dissolved or dissolved in depolymerized lignin such as a mixture comprising phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol.
In a fourth aspect the present invention relates to a fuel obtained by the method according to the present invention.
All the embodiments described herein are applicable to all the aspects unless stated otherwise.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1, a schematic disclosure of the Bergius process

FIG. 2, the effect on polarity during hydrotreatment.

FIG. 3, a schematic overview of the present invention. The compounds that are found at the upper part of the column are smaller and contain less oxygen than compounds further down the column.

FIG. 4, a schematic disclosure of the effect of hydrotreating on different materials of the feed.

FIG. 5, HSQC comparison between the Lignoboost® starting material and the hydrotreated product.

FIG. 6, HSQC NMR-spectrum of lignin dissolved in guaiacol which has been hydrotreated.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a composition for use in a refinery processes for the production of various fuels or chemicals.
In the present application the term “lignin” means a polymer comprising coumaryl alcohol, coniferyl alcohol and sinapyl alcohol monomers.
In the present application the term “carrier liquid” means a liquid selected from fatty acids or mixture of fatty acids, esterified fatty acids, rosin acid, crude oil, mineral oil, bunker fuel and hydrocarbon oils or mixtures thereof.
In the present invention the term “oil” means a nonpolar chemical substance that is a viscous liquid at ambient temperature and is both hydrophobic and lipophilic.
In the present application the terms “red liquor” and “brown liquor” denote the same liquor.
In the present invention the term “hydrogen donor” should be interpreted as a substance or compound that gives or transfers hydrogen atoms to another substance or compound.
For the purpose of this application the term “membrane filtration” shall include both cross-flow and dead-end flow modes by the use of porous membranes or filters.
In the present application the terms “heavy products” and “depolymerized lignin” denotes the same thing and are used interchangeably.
In the present application the terms “green carrier liquid” and “green carrier oil” denotes the same thing and are used interchangeably.
Oil refineries cannot use lignin as feedstock in current hydrotreaters as lignin does not dissolve in standard carrier oil. In the Bergius process coal is finely divided and formulated in recirculated heavy oil and then treated under hydrogen in presence of a solid catalyst at elevated temperatures. In the hydrotreatment process heavy oils, middle oils, gasoline, and gases are generated. After fractionation through distillation the gases, gasoline, and middle oils continue to become products of various kinds while the heavy oils are recirculated for reuse as carrier oil for more coal (FIG. 1). Instead the present invention relates to formulate lignin in depolymerized lignin or recirculated partially hydrotreated lignin which will serve as carrier liquid for a hydrotreater replacing the gas oil (FIG. 3). The depolymerized lignin may be prepared by hydrotreatment, hydrothermal treatment, hydrothermal cracking or solvolysis or any combination thereof.
There are two different processes in the hydrotreatment which are intimately related as they both involve the cleavage of C—O bonds; depolymerization and hydrophobization. The depolymerization is mostly a consequence of ether bond cleavages while hydrophobization is associated with the removal of hydroxyl-groups. The starting material lignin is polar, while completely deoxygenated compounds, i.e. pure hydrocarbons are non-polar. The polarity of the feed changes as it goes through the hydrotreater and becomes less polar (FIG. 2). The feed also becomes smaller through the process of depolymerization.
One object of the present invention is to develop a new method to enable the formulation of lignin into green carrier oils or liquids which can be pumped into conventional hydrotreaters for conversion into green light products. The green carrier oil is produced by the partial deoxygenation of lignin through hydrotreatment or by hydrothermal treatment or hydrothermal cracking or solvolysis or any combination thereof.
Unlike U.S. Pat. No. 7,994,375 the present invention is not dependent on further addition of a carrier liquid and solves another problem which is to form a solution of lignin where the lignin is dissolved in hydrotreated lignin compounds. The present invention does not aim at fully deoxygenate the lignin only to the extent that it dissolves lignin.
The method according to the present invention may be a continuous process or a batch process.

Lignin

In order to obtain lignin biomass may be treated in any suitable way known to a person skilled in the art. The biomass may be treated with pulping processes or organosols processes for example. Biomass includes, but is not limited to wood, fruits, vegetables, processing waste, chaff, grain, grasses, com, com husks, weeds, aquatic plants, hay, paper, paper products, recycled paper, shell, brown coal, algae, straw, bark or nut shells, lignocellulosic material, lignin and any cellulose containing biological material or material of biological origin. In one embodiment the biomass is wood, preferably particulate wood such as saw dust or wood chips. The wood may be any kind of wood, hard or soft wood, coniferous tree or broad-leaf tree. A non-limiting list of woods would be pine, birch, spruce, maple, ash, mountain ash, redwood, alder, elm, oak, larch, yew, chestnut, olive, cypress, banyan, sycamore, cherry, apple, pear, hawthorn, magnolia, sequoia, walnut, karri, coolabah and beech.
It is preferred that the biomass contains as much lignin as possible. The Kappa number estimates the amount of chemicals required during bleaching of wood pulp in order to obtain a pulp with a given degree of whiteness. Since the amount of bleach needed is related to the lignin content of the pulp, the Kappa number can be used to monitor the effectiveness of the lignin-extraction phase of the pulping process. It is approximately proportional to the residual lignin content of the pulp.
K≈c*1
K: Kappa number; c: constant 6.57 (dependent on process and wood); l: lignin content in percent. The Kappa number is determined by ISO 302:2004. The kappa number may be 20 or higher, or 40 or higher, or 60 or higher. In one embodiment the kappa number is 10-100.
The biomass material may be a mixture of biomass materials and in one embodiment the biomass material is black or red liquor, or materials obtained from black or red liquor. Black and red liquor contains cellulose, hemi cellulose and lignin and derivatives thereof and cooking chemicals. The composition according to the present invention may comprise black or red liquor, or lignin obtained from black or red liquor.
Black liquor comprises four main groups of organic substances, around 30-45 weight % ligneous material, 25-35 weight % saccharine acids, about 10 weight % formic and acetic acid, 3-5 weight % extractives, about 1 weight % methanol, and many inorganic elements and sulphur. The exact composition of the liquor varies and depends on the cooking conditions in the production process and the feedstock. Red liquor comprises the ions from the sulfite process (calcium, sodium, magnesium or ammonium), sulfonated lignin, hemicellulose and low molecular resins.
The lignin according to the present invention may be Kraft lignin, sulfonated lignin, Lignoboost® lignin, precipitated lignin, filtrated lignin, acetosolv lignin or organosolv lignin. In one embodiment the lignin is Kraft lignin, acetosolv lignin or organosolv lignin. In another embodiment the lignin is Kraft lignin. In another embodiment the lignin is organosolv lignin. In another embodiment the lignin obtained as residual material from ethanol production. The lignin may when added b in particulate form with a particle size of 5 mm or less, or 1 mm or less, or 500 μm or less, or 300 μm or less.
A problem with lignin, native lignin or Kraft lignin for example, is that it is not soluble in most organic solvents, fatty acids or oils. Instead prior art have presented various techniques to depolymerize and covert the depolymerized lignin into components soluble in the wanted media.
One of the mildest ways of attaining lignin from wood is by organosolv pulping. Through this method the lignin retains much of its native structure with many ether bonds. This makes organosolv lignin easy to depolymerize and deoxygenate. Unlike organosolv lignin Kraft lignin is harshly processed in order to remove much lignin from the cellulose fibres in the Kraft process. Through the Kraft process the native lignin is destroyed and recondensed into Kraft lignin which is very resilient towards chemical treatment. The chemical bonds in Kraft lignin are more difficult to cleave as compared to organosolv lignin. Reviewing the recent literature on lignin catalysis much of the work is focused on organosolv lignin as this lignin is much more effected by catalysis as compared to Kraft lignin. Even if the use of organosolv lignin in hydrotreating is easier there is much more Kraft lignin available than organosolv lignin making Kraft lignin a more interesting source.
The weight average molecular weight (mass) (M_w) of the lignin according to the present invention may be 30,000 g/mol or less, such as not more than 20,000 g/mol, or not more than 10,000 g/mol, or not more than 5,000 g/mol, or not more than 2,000 g/mol, but preferably higher than 1,000 g/mol, or higher than 1,200 g/mol, or higher than 1,500 g/mol. In one embodiment the number average molecular weight of the lignin is between 1000 and 4,000 g/mol, or between 1,500 and 3,500 g/mol. Kraft lignin usually have a molecular weight (Mw) of around 2,000-10,000 g/mol such as 2,500 and 5,000 depending on the Kraft process conditions.
The amount of lignin, non-hydrotreated lignin, in the composition may be 1-50 wt % such as 2 wt % or more, or 3 wt % or more, or 5 wt % or more, or 10 wt % or more, but 40 wt % or less, or 30 wt % or less, or 20 wt % or less, or 15 wt % or less. Lower amounts of lignin makes the composition more easy to pump and to high amounts of lignin may make the hydrotreatment less efficient. The composition may also comprise hydrotreated lignin obtained from the hydrotreatment of a previous or another composition according to the invention.
The composition is preferably free or essentially free of particles which may block or interfere with the catalyst in the hydrotreater which would reduce the flow through and the efficiency of the hydrotreater. The composition may in one embodiment be defined as not being a slurry. In one embodiment the composition is free of particles having a diameter of 5 mm or more, or 3 mm or more, or 1 mm or more, or 500 μm or more, or 300 μm or more, or 100 μm or more, or 50 μm or more, or 20 μm or more.

Method of Treating Lignin

The method according to the present invention aims at preparing light compounds that may be used as fuel components or additives to fuels or compounds that may be further refined in a hydrotreater or a catalytic cracker for example. The method is schematically disclosed in FIG. 3 and comprises providing a first feed of lignin where the feed is a liquid or a solution. The feed may be lignin dissolved in a solvent or for example black liquor. The first feed may comprise depolymerized lignin, an organic solvent or a mixture of organic solvents or a mixture of depolymerized lignin and at least one organic solvent. The first feed may be prepared at a temperature of at least 50° C. or higher, or 70° C. or higher, or 90° C. or higher.
The first feed comprising a solution of lignin is introduced into a hydrotreater where the feed is hydrotreated using any suitable hydrotreating technique forming a first product stream comprising light compounds and depolymerized lignin (heavy compounds). The ratio of light compounds and depolymerized lignin depends on the hydrotreating conditions such as time, temperature, pressure, catalyst and hydrogen donor. From the first product stream the light compounds are removed (denoted “Gasoline” and “Diesel” in FIG. 3), for example by distillation or evaporation, and leaves a second product stream (denoted “green carrier liquid” in FIG. 3) comprising the depolymerized lignin. The light compounds may be further treated using an additional hydrotreater or a catalytic cracker for example. A second feed of lignin is then provided and mixed with the second product stream or the depolymerized lignin. The depolymerized lignin at least partly dissolve or fully dissolve the lignin of the second feed making the lignin more susceptible to hydrotreatment making the hydrotreatment more efficient. The second feed of lignin may be prepared as the first feed of lignin and may comprise the same solvent or mixture of solvents as the first feed of lignin. This is of course also true for every subsequent feed of lignin.
The feed of lignin entering the hydrotreated is preferably a fully dissolved solution. The feed is also preferably essentially free from particles. FIG. 3 discloses a schematic view of the method and the compounds and temperatures disclosed in the figure are only examples and should not be seen as limiting. The method may be adapted by the skilled person in order to prepare a first and a second and a subsequent product stream which contains the wanted compounds.
Performing hydrotreating over a series of packed beds instead of in a slurry gives much greater possibilities to control the hydrotreating process. Different catalytic materials can be placed in different positions in the beds to give optimal performance. The hydrogen flow and temperature can be optimized for each bed to give the optimal degree of hydrotreating and product properties.
The hydrotreater used in the present invention may be a fixed bed hydrotreater. The hydrotreater reactor may comprise one or more fixed beds where each bed may contain different catalysts. The system may also contain a guard bed arranged prior to or inside the reactor in order to remove metals and optionally also a particle filter arranged at the inlet or prior to the inlet of the hydrotreater.
The mixing of the second product stream and the second feed of lignin may be done at a temperature of at least 50° C. or higher, or 70° C. or higher, or 90° C. or higher. The mixing may be done using stirring or shaking or any other suitable method. The mixing may be an extraction step where the second product stream extracts lignin from a liquid lignin composition such as black liquor.
This method may be operated continuously, in other words a more or less continuous second feed of lignin (dry or in liquid phase) may be mixed as described herein with the continuously prepared second product stream of depolymerized lignin. The second product stream may vary for each cycle and may comprise different compounds or may comprise different ratios of the compounds for each cycle.
The addition of the hydrogen gas or hydrogen donor (H-donor) may be done in the hydrotreater or prior to feeding the lignin or lignin containing mixture into the hydrotreater.
The present invention provides a method of preparing light compounds from lignin without the need to add fossil fuels or oils, or the use of fatty acids derived from crops. By hydrotreating lignin the method prepares a solvent for dissolving lignin. The present invention is also believed to result in high yield of high valuable products and low coke formation. By adjusting the parameters of the method such as temperature, time, pressure and catalyst the present method may be adapted to obtain specific products from the hydrotreatment step so that the first product stream contains the wanted products and the second product stream contains compounds that dissolve lignin.

Hydrotreating and Cracking

Hydrotreating and catalytic cracking are common steps in the oil refinery process where the sulfur, oxygen and nitrogen contents of the oil is reduced and where high-boiling, high molecular weight hydrocarbons are converted into gasoline, diesel and gases. During hydrotreating the feed is normally exposed to hydrogen gas (for example 20-200 bar) and a hydrotreating catalyst (NiMo, CoMo or other HDS, HDN, HDO catalyst) at elevated temperatures (200-500° C.). The hydrotreatment process results in hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and hydrodeoxygenation (HDO) where the sulphurs, nitrogens and oxygens primarily are removed as hydrogen sulfide, ammonia, and water. Hydrotreatment also results in the saturation of olefins. Catalytic cracking is a category of the broader refinery process of cracking. During cracking, large molecules are split into smaller molecules under the influence of heat, catalyst, and/or solvent. There are several sub-categories of cracking which includes thermal cracking, steam cracking, fluid catalyst cracking and hydrocracking. During thermal cracking the feed is exposed to high temperatures and mainly results in homolytic bond cleavage to produce smaller unsaturated molecules. Steam cracking is a version of thermal cracking where the feed is diluted with steam before being exposed to the high temperature at which cracking occurs. In a fluidized catalytic cracker (FCC) or “cat cracker” the preheated feed is mixed with a hot catalyst and is allowed to react at elevated temperature. The main purpose of the FCC unit is to produce gasoline range hydrocarbons from different types of heavy feeds. During hydrocracking the hydrocarbons are cracked in the presence of hydrogen. Hydrocracking also facilitates the saturation of aromatics and olefins.
In one embodiment of the present invention the hydrotreatment comprises treating the lignin with hydrogen gas or a hydrogen donor. The hydrogen donor may for example be formic acid or an alcohol or a combination thereof. A non-limiting list of suitable alcohols is methanol (MeOH), ethanol (EtOH), propanol, iso-propanol (i-PrOH), glycerol, glycol, butanol, t-butanol (i-BuOH) or combinations thereof. The pressure in the reactor during the hydrotreatment may be 5 to 400 bar such as 50 bar or higher, or 100 bar or higher, or 300 bar or lower, or 200 bar or lower, or 150 bar or lower. In one embodiment the hydrogen pressure is 20-200 bar, such as 30-70 bar such as 40-60 bar. Since water is generated during the hydrogenation a large amount of energy is released. By using a low hydrogen gas pressure this issue may be handled. The hydrotreatment may be performed at a temperature of not more than 500° C., or not more than 400° C., preferably not more than 300° C., or not more than 200° C., preferably at 100° C. or higher, or 150° C. or higher. In one embodiment the hydrotreatment is done at a temperature of 200 to 350° C.
In one embodiment the hydrotreatment is performed in the presence of a catalyst for HDS, HDO, and/or HDN. For example a transition metal catalyst such as an Al, W, Ir, Re, Ni, Mo, Zr, Co, Ru, Rh, Pt or Pd based catalyst. For example Raney nickel, nickel on carbon, Ni/Si, Ni/Fe, Nickel nanopowder, zeolite, amorphous silica-alumina, Pd/C, NiMo or CoMo or a combination thereof. In one embodiment the catalyst is a NiMo or a CoMo catalyst.
The components of the feedstock will be influenced differently when subjected to the hydrotreatment process. The transformation of the lignin may be incremental and may require more than one pass through the hydrotreater before forming a fully deoxygenated product. On the first pass lignin will partially be deoxygenated and depolymerized. Most of this material will follow the heavy fraction of depolymerized lignin (called green carrier liquid) back for a second pass through the hydrotreater. On the second pass through the hydrotreater it is more likely that larger amounts of fully deoxygenated products form, i.e. liquid petroleum gas (LPG) and liquid fuel. By adjusting the distillation parameter the middle distillates (diesel) can either form product or be recirculated for one more pass through the hydrotreater. Due to partial hydrocracking the recirculated fraction will eventually form LPG and light liquid fuel.
The hydrotreatment is performed until the amount of wanted products is obtained. For example the hydrotreatment may be done during at least 30 minutes, or at least 1 hour, or at least 2 hours, or at least 4 hours. In one embodiment the hydrotreatment is done during 1-2 hours. FIG. 4 discloses schematically the hydrotreatment products obtained when treating different materials.

Distillation

The first product stream formed during hydrotreatment comprises light compounds and depolymerized lignin and the light compounds are in the next step removed from the first product stream to form a second product stream comprising the heavy products and optionally also some residues. The removal of the light products may be done by distillation or evaporation under reduced or at atmospheric pressure.
FIG. 4 discloses a schematic view of the present invention where the different distillation temperature intervals for the compounds, light and heavy, are shown. The specific compounds and distillation temperatures are only illustrative and should not be seen as limiting.
The partially deoxygenated heavy oil or green carrier liquid comprises depolymerized lignin which is a mixture of compounds. These compounds may have a mean boiling point of at least 165° C., preferably at least 175° C., or at least 180° C. or preferably at least 200° C., or at least 220° C. but may be less than 350° C., or less than 300, or less than 250° C. The mixture may further comprise compounds that decompose before reaching their boiling point at atmospheric pressure. In one embodiment the mean boiling point is 200-350° C. The amount of said depolymerized lignin in the green carrier liquid may be 70 wt % or more, or 80 wt % or more, or 90 wt % or more, or 95 wt % or more, or 99 wt % or more. The depolymerized lignin may be phenol or phenol derivatives, polyphenols or polyphenol derivatives such as alkylphenol, alkyl alkoxyphenol or alkoxyphenol or diphenols or a mixture thereof.
The depolymerized lignin in the green carrier liquid may also be defined by having a boiling point of at least 180° C., or at least 200° C., or at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C. The amount of said depolymerized lignin in the green carrier liquid may be 70 wt % or more, or 80 wt % or more, or 90 wt % or more, or 95 wt % or more, or 99 wt % or more. The green carrier liquid may comprise compounds that has a boiling point below each of these temperatures but then at low amounts such as 10 wt % or less, or 5 wt % or less, or 2 wt % or less, or 0.5 wt % or less.
In one embodiment the amount of depolymerized lignin in the first product stream that is used as green carrier liquid is at least 20%, or at least 40%, or at least 60%, or at least 70%, or at least 80%, or at least 85% or at least 90% but less than 100%, or less than 95%.
The depolymerized lignin may also comprise hydrotreated oligomeric or polymeric lignin herein called oligomeric hydrotreated lignin (OHL). The oligomeric hydrotreated lignin will most likely have a reduced molecular weight in comparison with the lignin in the composition prior to the hydrotreatment however it might not have a boiling point due to that it decomposes before reaching its boiling point. The hydrotreated lignin (OHL) is probably oligomeric but may be polymeric lignin. The hydrotreated lignin may have a molecular weight (M_w) of 400 g/mol or higher, or 600 g/mol or higher, or 800 g/mol or higher but preferably not more than 1500 g/mol, or 1300 g/mol or lower, or 1000 g/mol or lower. The OHL may also be partly deoxygenated in comparison with the non-hydrotreated lignin. The amount of OHL in the green carrier liquid may be 0-50 wt % such as 1 wt % or higher, or 5 wt % or higher, or 10 wt % or higher, or 45 wt % or lower, or 35 wt % or lower, or 25 wt % or lower, or 15 wt % or lower. The amount of OHL in the green carrier liquid may be adjusted in order to optimize the system and the method such as amount of hydrogen, flow, temperature and yield. By adjusting the hydrogen pressure and temperature the amount of coke may be reduced.

Solvents

According to the present invention the composition comprises depolymerized lignin, preferably depolymerized Kraft lignin, which acts as a solvent and dissolves the lignin of the composition. The depolymerized lignin may be obtained by partly hydrotreating, hydrocracking or thermally cracking lignin.
The depolymerized lignin may be a mixture of phenol derivatives or polyphenol derivatives such as phenol or polyphenols and an alkylphenol, alkyl alkoxyphenol or an alkoxyphenol. The phenol derivatives may have two or more hydroxyl groups. The polyphenols may be diphenols or triphenols for example. In one embodiment the mixture comprises phenol, alkylphenol, alkyl alkxoyphenol and alkoxyphenol.
The phenol derivative according to the present invention has the general structure according to formula (1)
wherein each R1 to R6 may be individually selected from hydrogen, hydroxyl group, an alkyl group, an alkoxy group and alkyl alkoxy group and wherein at least one of R1 to R6 is a hydroxyl group. In one embodiment R6 is a hydroxyl group. In one embodiment the phenol derivative is a diol or a diphenol and preferably the hydroxyl groups are in ortho position to each other. In one embodiment at least one of R1 to R6 is an alkoxygroup such as a C1-C5 alkoxygroup. In one embodiment an alkoxy group is in ortho position to the hydroxyl group. In one embodiment at least one of R1 to R6 is a C1-C10 alkyl group such as a C1-C5 alkyl group. In one embodiment at least one of R1 to R6 is a methyl group. In one embodiment R6 is a hydroxyl group and at least one of R1 or R5 is an alkoxy group, for example a methoxy group, and at least one of R2-R4 is a C1-C5 alkyl group such as a methyl group or ethyl group.
The polyphenol according to the present invention has the general structure according to formula (2a) or (2b)
wherein each R′ and R″ is individually a C1-C5 alkyl group, preferably a C2-C3 alkyl group and wherein each Ph₁to Ph₃is a phenol derivative according to formula (1). The phenol derivatives (Ph) may be in ortho, meta or para position to each other. The phenol or polyphenol derivatives may be derived from lignin preferably Kraft lignin.
The mixture may comprise phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol. The weight proportion of phenol derivatives to polyphenol derivatives in the mixture may be from 1:100 to 100:1 (phenol derivative:polyphenol derivative).
Oxygenated products such as alcohols increase the hydrophilicity and thereby increases the amount of lignin that may be dissolved. In one embodiment the mixture contains at least 50 wt % oxygenated compounds, or at least 70 wt % oxygenated compounds, or at least 90 wt % oxygenated compounds.
The depolymerized lignin in the composition may also comprise hydrotreated oligomeric or polymeric lignin herein called oligomeric hydrotreated lignin (OHL). The oligomeric hydrotreated lignin may have a reduced molecular weight in comparison with the lignin in the lignin feed. The hydrotreated lignin (OHL) is probably oligomeric but may be polymeric lignin and is preferably Kraft lignin. The hydrotreated lignin may have a molecular weight (M_w) of 400 g/mol or higher, or 600 g/mol or higher, or 800 g/mol or higher but preferably not more than 1500 g/mol, or 1300 g/mol or lower, or 1000 g/mol or lower. The OHL may also be partly deoxygenated in comparison with the non-hydrotreated lignin. The amount of OHL in the depolymerized lignin may be 0-50 wt % such as 1 wt % or higher, or 5 wt % or higher, or 10 wt % or higher, or 45 wt % or lower, or 35 wt % or lower, or 25 wt % or lower, or 15 wt % or lower of the total weight of the depolymerized lignin.
According to the present invention the composition may further comprise an added solvent. This solvent may be added to the first feed of lignin or, prior to or during the mixing of the second product stream with the second lignin feed. In one embodiment the composition does not comprise any added carrier liquid such a fossil fuel or oil or fatty acid or fatty acid ester.
The solvent may also be an organic solvent or a mixture of organic solvents. In one embodiment the solvent is a mixture of an organic solvent. The organic solvent may be but is not limited to oxygenates such as an ester, ether, alcohol, aldehyde, sulfoxide or ketone. Preferred solvents are C1-C10 alcohols, C1-C10 aldehydes, C2-C15 ketones, C2-C10 ethers, and C2-C10 esters. A non-limiting list of solvents is methanol, ethanol, propanol, isopropanol, glycerol, phenol, alkylphenols or diols and butyl ether such as tert-butyl methyl ether; diethyl ether, diglyme, diisopropyl ether, dimethoxyethane, diethylene glycol, diethyl ether, polyethylene glycol, 1,4-dioxane and tetrahydrofuran, methylated tetrahydrofuran, mesityl oxide, furfural, isophorone. Preferred C2-C10 esters are organic esters, aromatic or non-aromatic esters, examples of esters are benzyl benzoate, various acetates such as methyl acetate, ethyl acetate, cyclopentyl methyl ether and butyl acetate, various lactates such as ethyl lactates. Solvents that are similar to or may be converted into fuel or petrol are interesting when the composition is to be used for fuel preparation. Such solvents could be ketones, ethers or aldehydes. In one embodiment the solvent is a C2-C15 ketone such as a C4-C12 ketone or a C6-C8 ketone. In one embodiment the solvent is a C1-C10 aldehyde such as a C4-C9 aldehyde or C6-C8 aldehyde. In one embodiment the solvent is a C4-C10 ether. In one embodiment the solvent is a mixture of a C2-C15 ketone and a C1-C10 aldehyde. In one embodiment the solvent is or comprises mesityl oxide. In one embodiment the solvent is or comprises acetone. In one embodiment the solvent is or comprises acetophenone. In one embodiment the solvent is or comprises pentanone. In one embodiment the solvent is or comprises ethyl isopropyl ketone. In one embodiment the solvent is or comprises isophorone. In one embodiment the organic solvent is or comprises an aromatic aldehyde or a mixture containing an aromatic aldehyde for example furfural. In one embodiment the solvent comprises furfural or furfuryl alcohol. In one embodiment the solvent is or comprises benzaldehyde. In one embodiment the solvent is or comprises ethyl acetate. In one embodiment the solvent is a C1-C10 alcohol or a C1-C10 diol. In one embodiment the solvent is or comprises ethanol. In one embodiment the solvent is or comprises methanol. In one embodiment the solvent is or comprises isopropanol. In one embodiment the solvent is or comprises solketal. In one embodiment the solvent is or comprises phenol. In one embodiment the solvent is a C2-C10 ester. In one embodiment the solvent is or comprises tetrahydrofuran or methylated tetrahydrofuran. In one embodiment the solvent is or comprises 1,4-dioxane.
In one embodiment the solvent comprises a combination of C1-C10 alcohols, C2-C10 ethers and C2-C10 esters. In one embodiment the solvent comprises two C1-C10 alcohols for example ethanol and glycerol, and in another embodiment the solvent comprises propanol and glycerol. In one embodiment the solvent comprises polyethylene glycol and a C1-C10 alcohol. When the solvent is a mixture of an organic solvent and water the mixture may contain methanol and water, ethanol and water, isopropanol and water or ethyl acetate and water, preferably ethanol and water, isopropanol and water and ethyl acetate and water.
In one embodiment the solvent is a mixture of a C2-C15 ketone such as a C4-C12 ketone or a C6-C8 ketone or a C1-C10 aldehyde such as a C4-C9 aldehyde or C6-C8 aldehyde and an alcohol. In one embodiment the solvent is a mixture of a C1-C10 alcohol such as a C3-C8 alcohol and an aldehyde.
In one embodiment the amount of depolymerized lignin in the composition is 1-99 weight % of the total weight of the composition. In one embodiment the amount of depolymerized lignin is 10-90 weight %, or 20-80 weight %. In one embodiment the amount of depolymerized lignin is 75 weight % or less, or 70 weight % or less, or 65 weight % or less, or 60 weight % or less, or 40 weight % or more, or 45 weight % or more, or 50 weight % or more, or 55 weight % or more of the total weight of the composition.
In one embodiment the amount of added organic solvent in the composition is 1-99 weight % of the total weight of the composition. In one embodiment the amount of solvent is 10-60 weight %, or 20-50 weight %. In one embodiment the amount of organic solvent is 70 weight % or less, or 40 weight % or less, or 20 weight % or less, or 10 weight % or less, or 5 weight % or less, or 2 weight % or less of the total weight of the composition. In one embodiment the composition does not comprise any added organic solvent.

Pre-Treatments

The feed of lignin provided may be treated in a pre-treatment step prior to the step of providing the feed of lignin. The pre-treatment may be selected from membrane filtration, solvent extraction or acidification and separation or a combination thereof. The purpose of the pre-treatment may be to remove unwanted products such as salts, catalysts or metal compounds which may damage the catalyst in the hydrotreatment step for example. If the feed is black liquor a pre-treatment step may remove cooking chemicals which may be returned to the pulping mill.
When using membrane filtration the cut-off of the membrane may be 200 to 10,000 Da such as 200-5,000 Da or 500-1000 Da. The filtration may also be performed in several steps using membranes with different cut offs. For example the lignin feed may be filtrated using a filter having a cut off of 10,000 Da and where after the permeate is diluted by addition of water or a suitable solvent and then filtrated using a membrane with a cut-off of 200-1000 Da. The retentate is then used as the lignin feed according to the present invention. In another embodiment the lignin feed may be filtrated using a filter having a cut off of 200-1000 Da and where after the permeate is diluted by addition of water or a suitable solvent and then filtrated using a membrane with a cut-off of 200-1000 Da. The retentate is then used as the lignin feed according to the present invention. The process may comprise recirculation of the liquid lignin composition and dilution of certain fractions containing lignin before subjecting to filtration, either in the incoming process flow to a filtration unit or in recirculated process liquid or both, at one or more points downstream of a first filtration step. Recirculation is preferably performed in a continuous loop, i.e. liquid is pumped from one point to another point in the system upstream thereof. If desired, dilution is thereby performed by injecting solvent, e.g. water into the recirculation pipes by suitable pumping means. Dilution is believed to make the removal of unwanted substances such as salts more efficient.
In its most general embodiment the process using dilution comprises subjecting a liquid lignin containing composition, e.g. black liquor, to a first membrane filtration with a first filter cut-off adapted to separate species in said liquid lignin containing composition in fractions thereby providing a permeate and a retentate having respective molecular weight distributions defined by said cut-off; subjecting either the retentate or the permeate from the first membrane filtration to at least one further ultrafiltration step with a second filter cut-off different from said first filter cut-off to provide a retentate (concentrate) and a permeate having respective molecular weight distributions defined by both the cut-off in the first filter and the cut-off in said second filter; recirculation of a fraction of the liquid lignin composition from a filter unit, suitably the retentate, back to inflowing liquid; wherein a dilution is performed on a desired lignin containing fraction at some point downstream of the first filtration unit; and collecting a desired lignin containing fraction, i.e. a retentate (concentrate) or a permeate from the further membrane filtration for further processing.
The lignin may also be precipitated by acidification followed by separation such as decantation or filtration. The pre-treatment may be a combination of the above mentioned treatments and may comprise the steps of membrane filtration, precipitation by acidification followed by membrane filtration.

EXAMPLES

Example 1

Solubility and Boiling Points:
Monomeric compounds attained after hydrotreating include alkyl phenolics, aromatics, naphthalenes, catecholics, guaiacolics, alkanes, cyclic alkanes. These monomers in turn come from oligomeric lignin. The solubility of lignin in some of these compounds was investigated and compound mixtures to show that lignin will be soluble in its own hydrotreatment products. After hydrotreatment the products was separated according to their boiling points (Table 1). The high boiling fraction is rich in oxygenates (phenolics) as these types of compounds have high boiling points while the fractions with a low boiling are largely fully deoxygenated compounds and will be removed as product.

TABLE 1

Solubility of lignin in different solvents which
are attained from lignin hydrotreatment.

	Solvents	bp [° C.]	Solubility [wt %]

Phenolics
4-ethylguaiacol	234	28
guaiacol	205	30
o-cresol	191	36
phenol	182	35
Aromatics
propylbenzene	159	Not soluble
ethylbenzene	136	Not soluble
toluene	110	Not soluble
Alkanes
propylcyclohexane	155	Not soluble
nonane	151	Not soluble
ethylcyclohexane	130	Not soluble
octane	125	Not soluble
heptane	98	Not soluble
cyclohexane	81	Not soluble

Mixtures of Oxygenated and Non-Oxygenated:
To reach an understanding of the proportions of oxygenated solvents which can be used for carrier liquid for lignin, a quick study with different proportions of one oxygenated (guaiacol) was performed and one non-oxygenated solvent, propylbenzene (Table 2). To all samples 10 wt % of lignin was added. If the solvent composition contains less than 10% non-oxygenated solvents than it is quite easy to dissolved at least 10 wt % lignin in the composition. To get mixtures with 10 wt % lignin into solvent compositions containing 20 to 30% non-oxygenated solvent it is preferable to heat the mixture above room temperature (70° C.).

TABLE 2

Solubility of lignin in solvent mixtures
attained from lignin hydrotreatment.

		Amount of lignin
		solubilized by
Solvent mixture	Proportions	solvent mixture	Comments

guaiacol	50:50	<10
propylbenzene
guaiacol	60:40	<10
propylbenzene
guaiacol	70:30	10	Mostly dissolved
propylbenzene			at 70° C.
guaiacol	80:20	10	Fully dissolved
propylbenzene			at 70° C.
guaiacol	90:10	>10	Fully dissolved
propylbenzene			at 25° C.

Batch Hydrotreating:
Several hydrotreating conditions have been attempted and the preliminary results show that hydrocarbons which have been fully deoxygenated may be produced. Industrial grade NiMo catalyst was used under batch conditions as a starting point. The first test under solvent free conditions (Table 3, entry 1) showed that it was too mild hydrotreating conditions for to short duration. Increasing the temperature to 350° C. and doubling the reaction time resulted in the recovery of a THF soluble fraction which was fully deoxygenated (Table 3, entry 2). The HSQC-NMR spectrum shows that the original lignin is drastically transformed to yield a hydrocarbon product (FIG. 5).

TABLE 3

Hydrotreatment of lignin under various conditions. 10
min ramp to temperature plateau from room temperature.

		Lignin	H₂	Temp.	Reaction
		conc.	pressure	plateau	time
Entry	Solvent	[wt %]	[bar]	[° C.]	[h]

1	None	100	50	300	1
2	None	100	50	350	2
3	guaiacol	50	50	350	4

Using guaiacol as a solvent was attempted with very nice results (Table 3, entry 3). An amber-colored oil was obtained after the hydrotreatment and according to the HSQC-NMR spectrum this oil is fully deoxygenated (FIG. 6). Obviously the spectrum mostly shows the sharp peaks from products attained from guaiacol hydrotreatment. However, the spectrum does not contain signals from the oxygen containing groups found in the original lignin and this result is very promising as many of the products formed when hydrotreating lignin is different types of alkylphenols.

Claims

1. A composition comprising Kraft lignin having a weight average molecular weight (M_w) of at least 1,000 g/mol dissolved in depolymerized Kraft lignin.

2. The composition according to claim 1 wherein the depolymerized lignin is a mixture comprising phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol.

3. The composition according to claim 1 wherein the concentration of lignin is at least 1 wt %, or at least 3 wt %, or at least 5 wt %, or at least 10 wt %, or at least 15 wt %, or at least 25 wt %, or 40 wt % or less, or 35 wt % or less, or 30 wt % or less of the total weight of the composition.

4. The composition according to claim 1 wherein no added carrier liquid is present.

5. The composition according to claim 1 wherein the mixture comprises at least 50 wt % of oxygenated compounds.

6. The composition according to claim 1 wherein the amount of lignin is 2-20 wt %; wherein the Kraft lignin has a weight average molecular weight (M_w) of higher than 1,500 g/mol but lower than 10,000 g/mol; wherein the amount of depolymerized Kraft lignin is 80-98 wt % and the depolymerized lignin comprises alkylphenols and alkoxy phenols.

7. The composition according to claim 1 wherein the boiling point of the depolymerized lignin is at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C.

8. The composition claim 1 wherein the composition is free of any particles having a diameter of 100 μm or more, or 50 μm or more, or 20 μm or more.

9. The composition according to claim 1 wherein the depolymerized lignin is obtained by hydrotreatment or by hydrothermal treatment or hydrothermal cracking or solvolysis or any combination thereof.

10. A method of preparing the composition according to claim 1 wherein the method comprises:

a. providing a first feed of Kraft lignin having a weight average molecular weight (M_w) of at least 1,000 g/mol wherein the feed is a solution of Kraft lignin;

b. hydrotreating the first feed forming a first product stream comprising light compounds and depolymerized lignin;

c. removing the light compounds from the first product stream leaving a second product stream comprising the depolymerized lignin;

d. providing a second feed of lignin; and

e. mixing the depolymerized lignin with the second feed of lignin.

11. The method according to claim 10 wherein the first feed of lignin is a mixture of the Kraft lignin and an organic solvent selected from an ester, ether, alcohol, aldehyde, sulfoxide or ketone.

12. The method according to claim 10 wherein the hydrotreating step comprises treating the lignin with hydrogen gas or a hydrogen donor.

13. The method according to claim 10 wherein the hydrotreating is performed together with a HDS, HDN or HDO catalyst such as a transition metal catalyst such as a Ni, Co, Mo, Zr, Ru, Pt or Pd based catalyst.

14. The method according to claim 10 wherein the hydrotreating is performed at a temperature of not more than 500° C., or not more than 400° C., or not more than 300° C., or not more than 200° C., or at 100° C. or higher, or 150° C. or higher.

15. The method according to claim 10 wherein the hydrotreating is performed at a pressure of 5 to 400 bar such as 50 bar or higher, or 100 bar or higher, or 300 bar or lower, or 200 bar or lower.

16. The method according to claim 15 wherein the hydrotreating is performed at a hydrogen gas pressure of 100-150 bar.

17. The method according to claim 10 wherein the first feed of lignin is a mixture of lignin and an alcohol such as phenol.

18. The method according to claim 10 wherein the depolymerized lignin comprises compounds having a boiling point of at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C.

19. The method according to claim 10 wherein the mixing of the second product stream and the second feed of lignin is done at a temperature of at least 50° C. or higher, or 70° C. or higher, or 90° C. or higher.

20. The method according to claim 10 wherein the depolymerized lignin comprises a mixture comprising phenol derivatives and polyphenol derivatives such as an alkylphenol, an alkyl alkoxyphenol or an alkoxyphenol and a diphenol.

21. The method according to claim 10 wherein the feed of lignin provided in step a and d are treated in a pre-treatment step prior to step a and d respectively wherein the pre-treatment is selected from membrane filtration, solvent extraction or acidification and separation or a combination thereof.

22. The method according to claim 10 wherein the amount of depolymerized lignin compounds having a boiling point of at least 220° C., or at least 250° C., or at least 280° C., or at least 300° C., or at least 330° C., or at least 350° C., is at least 50 wt %, or at least 60 wt %, or at least 70 wt %, or at least 80 wt %, or at least 90 wt %, or at least 95 wt %.

23. An intermediate composition comprising Kraft lignin having a weight average molecular weight (M_w) of 1,000 g/mol dissolved in depolymerized lignin.

24. A The fuel obtained by the method according to claim 10.