WO2017032926A2

WO2017032926A2 - Process for converting biomass

Info

Publication number: WO2017032926A2
Application number: PCT/FI2016/050582
Authority: WO
Inventors: Lauri Kuutti; Stella Rovio; Jaakko Hiltunen; Heimo KANERVA; Sauli VUOTI
Original assignee: Teknologian Tutkimuskeskus Vtt Oy
Priority date: 2015-08-27
Filing date: 2016-08-26
Publication date: 2017-03-02
Also published as: EP3341520A2; WO2017032926A3

Abstract

The present invention relates to a process for converting biomass comprising lignin, hemicellulose or combinations thereof, to valuable components, where the process comprises the step of treating biomass comprising lignin, hemicellulose or combinations thereof with deep eutectic solvent.

Description

PROCESS FOR CONVERTING BIOMASS

FIELD OF THE INVENTION

The present invention relates to a process for converting biomass to valuable components, where the process comprises the step of treating biomass comprising lignin, hemicellulose or combinations thereof with deep eutectic solvent. BACKGROUND OF THE INVENTION

Biomass comprising lignin, hemicellulose or combinations thereof is generally a renewable and low-cost bulky material which is suggested for processing to obtain more valuable chemicals. However, harsh and expensive pretreatment methods are necessary for processing these biomass materials on a larger industrial scale, and further, the energy demand in these pretreatment methods is very high.

In the pulp industry the fibrillation or separation of fibers from wood materials is typically carried out by unspecific chemical or mechanical methods. The main chemical processes used in the processing of wood biomass into wood pulp are the Kraft process and the sulfite process, where fibers and lignin are separated . In these processes the chemical structure of lignin is altered, which has negative effect on the utilization of lignin in further modifications. Similar problems are encountered also with organo-solv methods. Further, sulfur present in lignin makes its industrial application demanding . Ionic solvents (or ionic liquids) have been proposed for the sepa ration of lignin from lingo-cellulosic materials, where lignin, cellulose and hemicellulose ca n be dissolved and/or fractionated . However, ionic solvents are very expensive, typically their use is environmentally demanding, and their recycling is very difficult.

Eutectic mixtures a re a sub-class of ionic liquids with special properties. A eutectic mixture forms a eutectic with a melting point much lower than any of the individual components. The phenomenon was first described in 2003 for a mixture of choline chloride and urea in a 1 : 2 molar ratio, respectively. Choline chloride has a melting point of 302°C and that of urea is 133°C. The eutectic mixture melts at 12°C.

A deep eutectic mixture or deep eutectic solvent (DES) formed of choline chloride and urea has been studied in cellulose modifications and solubilization, where only modest concentrations of cellulose were solubilized in said mixture. WO 2013/153203 Al discloses pretreatment of lingo-cellulosic biomass, where lignin containing biomass is treated with a DES to solubilize lignin from the biomass. DESses consisting of choline chloride in combination with lactic acid, malic acid or oxalic acid are suggested for the solubilization lignin.

5-hydroxymethy furfural and furfural are important raw materials in the chemical industry, and they a re used for example in the manufacture of plastics, cellulose acetate and varnish. These furane compounds are typically manufactured from hexoses, pentoses and celluloses with sulfuric acid, whereby undesired side reactions occur.

Despite the ongoing research and development there is a need for improved methods and processes for converting biomass comprising lignin, hemicellulose or combinations thereof, to valuable components. SUMMARY OF THE INVENTION

An object of the invention is to provide a process for converting biomass comprising lignin, hemicellulose or combinations thereof, to valuable compounds and components.

A further object of the invention is to provide a process where lignin and non-soluble fibrous materials are obtained from biomass comprising lignin, hemicellulose or combinations thereof, in an efficient way.

Another object of the invention is to provide a process for the manufacture of 5- hydroxymethylfurfural, furfural, levulinic acid and formic acid from biomass comprising lignin, hemicellulose or combinations thereof.

Another object of the invention is to provide a process for the manufacture of magnetic lignin particles. The present invention relates generally to process for converting biomass comprising lignin, hemicellulose or combinations thereof, to valuable compounds and components.

Particularly, the present invention relates to a process for converting biomass, which process comprises the steps, where in the first step biomass comprising lignin, hemicellulose or combinations thereof is mixed with a DES to obtain a biomass mixture; in the second step water is added to the biomass mixture and an aqueous biomass mixture is obtained, the aqueous biomass mixture is separated into a non-solubilized fiber fraction, precipitated lignin fraction and a liquid fraction; and

in the third step the liquid fraction is heated to a temperature between 80°C and 130°C, and at least one of furfural, 5-hydroxymethylfurfural, levulinic acid and formic acid is formed and separated.

The present invention also relates to process for the manufacture of magnetic lignin particles and to magnetic lignin particles.

The present invention also relates magnetic lignin particles obtainable by the process. Characteristic features of the invention are presented in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an embodiment of the process.

Figure 2 shows another embodiment of the process, where magnetic lignin particles and fi bri Mated fibers are obtained.

Figure 3 shows fractionation efficiency of DES on different wood samples at three temperatures.

Figure 4 shows 5-hydroxymethylfurfural, furfural, formic acid, acetic acid and levulinic acid in the DES solutions of example 3.

Figure 5 shows UV-measurements of 5-hydroxymethylfurfural and furfural from water addition tests.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors found that biomass comprising lignin, hemicellulose or combinations thereof can be converted in a simple and efficient process to valuable compounds and components, such as non-condensate lignin, non-solubilized fiber fraction and furfural, 5-hydroxymethylfurfural, levulinic acid and formic acid. In the process biomass comprising lignin, hemicellulose or combinations thereof, such as lingo-cellulosic material, is treated at low or moderate temperatures with deep eutectic solvent (DES), followed by fractionation to more valuable compounds, which may optionally be processed further to compound such as furfural, 5-hydroxymethylfurfural, levulinic acid and formic acid. Biomass

Biomass comprising lignin, hemicellulose or combinations thereof refers here to any type of biomass, particularly lingo-cellulosic materials, which comprise lignin, hemicellulose or combinations thereof in addition to natural fibers. Typically the biomass comprises also cellulose. The biomass is suitably selected from fiber materials, waste streams and side streams, which originate from softwood, hardwood, straw, reed, hemp, sisal, flax, ramie, jute, agave, kenaf, rosella, urena, acaba, coir, corn, sugarcane, bagasse, banana, soybean, palm oil tree, cotton, sugar beet, olives, grapes and fruits, and combinations thereof. Waste streams and side streams comprising plant material, such as corn stover, banana fiber, empty fruit bunches like the ones from palm oil production, bean and pea hulls, sugar beet leftovers, hemp shives and bast fibers have low value use if any today, however they can be used in process of the invention as starting material for providing various high value chemicals and streams. Biomass comprising lignin, hemicellulose or combinations thereof is understood to mean also wood residues, saw mill discards, paper and board, paper, pulp and board mill discards and residues, press cakes and processing residues from fruit industry, municipal paper waste, recycled paper, fiber waste and residues and the like and any combinations of the above listed biomasses.

The biomass may be dried prior to introduction to the process of the invention.

The biomass is suitably pretreated mechanically and/or chemically prior to introduction to the process of the invention.

Suitable mechanical pretreatment methods include grinding, milling, refining, crushing and cutting and any combinations thereof.

Suitable chemical pretreatment methods include steam explosion, enzymatic treatment, acid hydrolysis and any combinations thereof.

The biomass may be sieved prior to using it as starting material in the process. If desired the particle size range may be selected according to the products, which are manufactured, i.e. fractions having longer fibers may be more desirable in some applications, and fractions comprising the smaller particle size typically provide higher amounts of solubilized lignin. Suitably the average particle size of the biomass entering the process is in the range of 0.5 - 10 mm.

Deep eutectic solvent (DES) useful in the first step of the process

The DES useful in the first step of process comprises a (2-R-ethyl)-trimethylammonium salt, or a mixture of said salts, and a Lewis acid selected from boric acid, meta-boric acid, boronic acid, borinic acid, alkyl borates, hydrated borate salts, puryvic acid and any combinations thereof. Preferably the Lewis acid is boric acid or pyruvic acid, particularly preferably boric acid. Boric acid refers here to H3BO3, also called as hydrogen borate, boracic acid, ortho- boric acid and acidum boricum.

In the (2-R-ethyl)-trimethylammonium salt the group R is selected from OH, halogens, ester groups, ether groups and carbamoyl group. The halogens are selected from F, CI, I and Br; the ester groups are suitably selected form formyl, acetyl, isopropyl and butyryl groups. Preferably the R is OH, CI, acetyl or formyl group. The counter anion in the salt can be an inorganic or organic counter anion. The inorganic salt is suitably a halogenide, sulphate or phosphate, preferably chloride salt. The organic salt is suitably acetate, lactate, butyrate or formiate.

Preferably the (2-R-ethyl)-trimethylammonium salt is selected from choline chloride, acetylcholine chloride, and chlorocholine chloride, particularly preferably choline chloride. Choline chloride is a widely available material and it is used for example as low cost animal feed.

The DES comprises a molar ratio from 5 : 1 to 1 : 1, preferably from 3 : 1 to 1 : 1 of the (2- R-ethyl)-trimethylammonium salt, or a mixture of said salts, preferably choline chloride and the Lewis acid, respectively. When the DES comprises choline chloride and puryvic acid, a molar ratio from 7:4 to 1 : 1, preferably from 1 : 2 to 1 : 1 is used.

The DES may be formed prior to introducing it to the first step of the process, or alternatively it may be formed in situ, whereby the (2-R-ethyl)-trimethylammonium salt, the Lewis acid and the biomass (optionally pretreated) are introduced to the reaction vessel in the first step. Process

The process of the invention comprises the steps, where in the first step biomass comprising lignin, hemicellulose or combinations thereof is mixed with a DES to obtain a biomass mixture;

in the second step water is added to the biomass mixture and an aqueous biomass mixture is obtained, the aqueous biomass mixture is separated into a non-solubilized fiber fraction, precipitated lignin fraction and a liquid fraction; and

In the second step lignin solubilized in the first step is precipitated.

Figure 1 illustrates one embodiment of the invention. In the first step of the process DES (20) is charged to a vessel (100) and biomass (10) is added to the DES (20), and the biomass (10) is mixed with the DES (20) to obtain biomass mixture (30). Water (40) and biomass mixture (30) are mixed in vessel (200) whereby an aqueous biomass mixture is obtained, comprising precipitated lignin. A non-solubilized fibrous fraction (50), precipitated lignin (60) and liquid fraction (70) are separated. The liquid fraction (70) is directed to vessel (300) where it is heated to a temperature between 80°C and 130°C and furfural, 5-hydroxymethylfurfural, levulinic acid and formic acid are formed . Furfural (80), 5-hydroxymethylfurfural (81), levulinic acid (82) and formic acid (83) are separated. Figure 2 illustrates another embodiment of the invention. In the first step of the process DES (20) is charged to a vessel (100) and biomass (10) is added to the DES (20), where the biomass (10) is mixed with the DES (20) to obtain a biomass mixture (30). Water (40) and biomass mixture (30) are mixed in vessel (200) whereby an aqueous biomass mixture is obtained, comprising precipitated lignin. A non-solubilized fibrous fraction (50), precipitated lignin (60) and liquid fraction (70) are separated. The liquid fraction (70) is directed to vessel (300) where it is heated to a temperature between 80°C and 130°C and furfural, 5-hydroxymethylfurfural, levulinic acid and formic acid are formed. Furfural (80), 5-hydroxymethylfurfural (81), levulinic acid (82) and formic acid (83) are separated. The non-solubilized fibrous fraction (50) is fibrillated in a fibrillator (400) to obtain fibrillated fibers (90). The precipitated lignin (60) and magnetic material (91) are mixed in vessel (500) and magnetic lignin particles (92) are separated. First step

In the first step biomass comprising lignin, hemicellulose or combinations thereof is treated with a DES to obtain biomass mixture, whereby lignin and hemicellulose are solubilized in the DES and a product mixture comprising the solubilized lignin and hemicellulose, non-solubilized fibers and the DES is obtained.

In the first step of the process preferably the DES is charged to a vessel and then the biomass is added to the DES. Optionally the biomass mixture may contain water not more than 10 wt%, calculated from the total weight of the biomass mixture. Water may be added to the DES, or to the biomass mixture, or the biomass may contain the water. The amount of water in the biomass mixture may be decreased for example by distillation, evaporation etc. According to one embodiment the biomass mixture is formed of the DES and the biomass, then it is mixed for 0.5 to 2 hours, followed by adding of 5-10 wt% water. Preferably the biomass mixture contains water not more than 10 wt%, calculated from the total weight of the biomass mixture. According to another embodiment the biomass is mixed with the DES, which contains 5-10 wt% water, calculated from the total weight of the biomass mixture, to obtain the biomass mixture, which is mixed for 0.5 to 2 hours, followed by removal of water, suitably using vacuum. The procedures described in the above embodiments may be used for optimizing the solubilization of lignin and cleavage of hemicelluloses.

In the first step the biomass mixture contains 2-40 wt%, preferably 5-25 wt% of the biomass, calculated based on dry weight.

In the first step the temperature is 50°C -150°C, preferably 70°C -130°C, particularly preferably 80°C -120°C.

In the first step the pressure is 100 mbar - 20 bar, preferably 1-10 bar. Inert gas, such as N2, Ar, He or CO2 may be used for pressurization of the reaction vessel. Higher pressure enhances the fibrillation the non-solubilized fibers in an optional fibrillation step. The non-solubilized fibers are separated and they may be subjected to said optional fibrillation. Further, the higher pressure also enhances the solubilization of lignin and hemicellulose. Optionally, in the first step, spherical particles or balls are used. Said spherical particles or balls are added to the biomass mixture for achieving grinding and/kneading effect and improving thus pulping effect and providing more surface area to the non- solubilized fibers. Preferably spherical particles or balls having a diameter from 100 μιη to 5 mm are used. Suitably the spherical particles or balls are glass balls, zirconium balls, such as zirconium silicate or zirconium oxide, or metal balls, which are insoluble in the chemical media used in the process.

In the first step the biomass mixture is mixed for 1-30 hours, preferably for 2-30 hours, particularly preferably 2-20 hours. Suitably mixing devices selected from high-shear mixers, homogenizers, processing grinders, helical mixers, high intensity mixers, fluidizers and twin-screw mixers may be used.

Second step

After the mixing is completed in the first step water is added to the biomass mixture to obtain an aqueous biomass mixture. Suitably the temperature of the water is between 40 and 100°C. Water is added to obtain suitably a volumetric ratio 10 : 1 - 1 : 1 of water with respect to DES. Lignin solubilized in the first step is precipitated. The aqueous biomass mixture is separated into a non-solubilized fiber fraction, precipitated lignin fraction and a liquid fraction. Suitably the temperature of the aqueous biomass mixture in the separation is 50-150°C, preferably 70-130°C, particularly preferably 80-120°C. The separation of the solid non-solubilized fiber fraction, precipitated lignin fraction and the optional spherical particles or balls, from the liquid fraction is carried out suitably using sieves, suitably with the aid of pressure, or using centrifuges, filters, pressure filters etc. The non-solubilized fibers and optional spherical particles or balls may be washed with water or organic solvent selected from lower alkyl alcohols, lower ketones, tetrahydrofuran, DMSO and combinations thereof, suitably selected from ethanol, methanol, isopropanol, acetone, methylethyl ketone, tetrahydrofuran and DMSO. The DES may conveniently be removed from the washing liquid and recycled. In the second step lignin is precipitated and separated and hydrolysis of hemicellulose in the liquid fraction is carried out. Suitably the aqueous biomass mixture is cooled prior to the separation. Typically non-condensate lignin having narrow average particle size, such as 20-50 μιη can be obtained, defined using particle size measurement based on laser diffraction. Hydrolyzed hemicelluloses remain in the liquid fraction from the second step, comprising the DES and water.

Third step

In the third step the liquid fraction obtained from the second step is heated to a temperature between 80°C and 130°C. DES promotes at elevated temperatures the formation of furfural from pentoses; the formation of hemicelluloses and 5- hydroxymethylfurfural from hexoses; and further, levulinic acid and formic acid may be obtained. When adjusting the temperature of the liquid fraction to 80°C -100°C, preferably 90°C -97°C, for 0.1-30 hours furfurals are obtained predominantly, and when adjusting the temperature of the liquid fraction to 102°C -115°C, preferably 105°C - 112°C, for 0.1-30 hours the equilibrium is shifted to levulinic acid. At temperatures above 115°C formic acid is obtained. Water content of the liquid fraction is 0-25 % by weight. If furfurals are desired the water content is adjusted between 5 and 15 % by weight.

5-hydroxymethylfurfural, furfural, levulinic acid and formic acid may be separated from the liquid fraction using suitable methods. Volatile compounds such as formic acid may be separated by distillation and 5-hydroxymethylfurfural, furfural, levulinic acid by chromatographic methods, such as any type of column chromatography, flash chromatography and the like, using water and organic solvents. DES may be separated from the remaining liquid fraction by removing water and possible organic solvents by suitable methods, such as evaporation, chromatographic methods etc. and it may be recycled to the first step of the process.

Wood biomass originating from wood based waste streams and side streams, such as from the Kraft process can be converted to non-soluble fiber fraction, lignin and xylan using the process of the invention, with high yields of even 90 %.

According to one embodiment the process comprises a fourth step, where lignin obtained in the second step is converted to magnetic lignin particles. In the fourth step 2-40 wt%, preferably 5-25 wt% of lignin obtained in the second step is added to a DES and mixed, whereby a lignin-DES mixture is obtained. The mixing may be carried out at pressure of 0-10 bar and a temperature of 30°C -140°C, preferably 40°C -140°C, for 0.1-30 hours.

0.1-100 wt%, preferably 0.2-50 wt%, particularly preferably 5-20 wt%, of magnetic material selected from Fe30₄, Nb and Nd, preferably Fe30₄, calculated respect to the amount of lignin (or lignin and chitosan when also chitosan is used) is mixed with the lignin-DES mixture for 0.1-30 hours. The mixing may be carried out at pressure of 0- 10 bar and a temperature of 30°C -140°C, preferably 40°C -140°C. 10-500 vol% of water or a lower (C1-C5) alcohol or a mixture thereof is brought into contact with the lignin-DES mixture, whereby magnetic lignin particles are precipitated, washed and optionally dried. The obtained magnetic lignin particles, which also mean here magnetic lignin-chitosan particles, may be used as such, or optionally they may be bound to a carrier material, such as polymeric matrixes. Optionally the magnetic lignin particles may be dialyzed to reach higher purity. The dialysis may be carried out using distilled water by a membrane with a cutoff (MWCO) of 1000 Da.

Optionally the lignin may also be cationized or anionized prior to solubilization in the DES. The cationization or anionization may be carried out using reagents known as such for cationization or anionization of lignin.

Optionally part of lignin may be replaced with chitosan. According to a preferable embodiment 2-50 wt% lignin is replaced with chitosan, whereby the amount of chitosan is 1-20 wt%, preferably 2.5 - 12.5 wt% and the total amount of lignin and chitosan is not more than 40 wt%, preferably not more than 25 wt% in the DES mixture, chitosan prevents particle agglomeration and improves stabilization of the magnetic lignin particles. The DES useful in the fourth step may be selected from DES formed of at least one or more hydrogen bond donor and at least one or more hydrogen bond acceptor, where the hydrogen donor is selected from urea, organic acids, alcohols, polyols, aldehydes, carbohydrates, saccharides, boric acid, metaboric acid, mono-, di- and tri-alkyl ureas, oxamide, mono- and dialkyl oxamides, guanidine, mono-,di-tri- and tetra- alkylguanidines, imides, and hydrated borate salts. The hydrogen bond acceptor is selected from amino acids, salts, organic salts, natural salts, choline chloride, acetylcholine chloride, and chlorocholine chloride. Preferably choline chloride: boric acid in a ratio from 3 : 2 to 3 : 3 is used.

Optionally the DES used in the fourth step may comprise 0.01-30 wt%, preferably 2- 15 wt% of water.

The DES used in the process (in the first step or in the fourth step) is obtained by mixing the components forming the DES to obtain a clear solution. Preferably the mixing temperature is 30-90°C. Preferably the mixing is carried out for 15 min - 24 hours, as total mixing time.

The process may further comprise an optional fibrillation step, where the non- solubilized fibers obtained in the first step are separated and subjected to said fibrillation. The fibrillation may be carried out using fibrillation equipment known as such, like Masuko grinders and homogenizers.

Magnetic lignin particles comprising lignin and magnetic material selected from Fe30₄, Nb and Nd, preferably Fe30₄, are obtained. The magnetic lignin particles may also comprise chitosan. Further, the lignin may also be cationized or anionized lignin.

The present invention provides several advantages. The process provides efficient means for utilizing non-solubilized fibrous material, lignin, cellulose and hemicelluloses of biomass in a new and energy efficient way, where DES, water and optional solvents are recyclable, and water consumption and energy consumption is reduced. High purity non-condensed lignin can be obtained with good yields, even without the need to use organic solvents. Furthermore, hemicelluloses can be simultaneously converted to valuable platform chemicals and the purity of lignin thus improved.

The non-solubilized fibrous material, such as the fibrous structures and multifilament fractions can be fibrillated more readily and the obtained fibrillated product is particularly suitable for example for the manufacture of multifilament structures.

The yields of the solubilized components are increased significantly, and for example 50-70 wt%, even up to 90 wt% of total lignin content in wood biomass can be recovered by the process of the invention. Lignin separated from the biomass is non-condensed and it can be obtained with high purity. The obtained lignin may further be used in the manufacture of lignin products, such as lignin resins, films, magnetic lignin particles etc.

The process provides also efficient and economic means for producing selectively 5- hydroxymethylfurfural, furfural, levulinic acid and formic acid from biomass, said compounds being valuable raw materials in the chemical industry. Elevated pressures in the process increase further the yields of these products.

The process provides also an efficient means for producing magnetic lignin particles, which are particularly useful in the removal of metal ions, particularly heavy metal ions from aqueous solutions, such as community and industrial waste-waters, contaminated waters, waste-waters in mines etc. Said magnetic lignin particles are also useful in medical diagnostic and treatment methods, magnetic immunoassay methods, as catalysts in biomedical imaging, information storage and genetic engineering. Further, the magnetic lignin particles are reusable, because they can be regenerated and the captured metal can be recovered and reused.

The energy consumption of the process is remarkably low. The DES, water and optional solvents can all be recycled in the process. If desired, only non-toxic chemicals may be selected for use in the process, which is advantageous for occupational safety and environmental aspects. No harmful emissions are released in the process. The process is simple, no harmful residues are left and no specific equipment is needed. The invention will now be illustrated with the following examples. Examples

Example 1

Converting of saw dust using DES comprising choline chloride and boric acid

Dissolution (solubilisation) experiments were carried out using a glass reactor equipped with mixer. The inside temperature in the vessel was 95°C in the dissolution trial. The stirring speed of PTFE centrifugal stirrer paddles was 100 rpm and reaction time was adjusted to 16 hours. The load of saw dust was 5 wt % in DES solution. The DES solutions were prepared using dry salts, which were mixed and heated up to the reaction temperature. The ChCI-Ba (choline chloride-boric acid) DES (molar ratio 5 : 3) formed a clear solution when the temperature was reached 65-70°C. Dry wood material was added slowly under mechanical stirring to ensure good mixing of solution and wood.

After 16 h dissolution period the DES/wood mixtures were fractionated using a set of three metallic sieves (1 mm, 0.3 mm and 0.15 mm) above the erlenmayer flask with vacuum filtration for collecting the <0.15 mm fraction. The fractionation of wood meal was first aided using total 400 ml of boiling water in 2 batches for washing the solid through the sieves. The precipitates were collected from sieves, dried at 50°C overnight and weighed. The precipitated lignin-rich portion ("< 0.15 mm") was filtered from DES solution, washed with 100 ml of cold water, dried at 50°C overnight and weighed. Carbohydrate content dropped systematically from the largest fractions to the smallest fraction, and respectively, the lignin content increased. The lignin rich content in the smallest precipitated sample was over 70 % and the yield was 20 % from the original lignin content in the saw dust.

Example 2

Converting of saw dust, milled fine softwood and thermo-mechanical pulp using DES comprising choline chloride-boric acid

Dissolution (solubilisation) experiments were carried out at different fractionation temperatures. The samples were coarse softwood (saw dust), fine softwood milled by Willey mill with 2 mm sieve and thermo-mechanical pulp (TMP). The inside temperature in the vessel was 75°C, 95°C and 110°C in the dissolution trials. The influence of drying (sample of fine softwood, dried at 140 °C) and the addition of extra water (sample of fine softwood + 5% H2O in DES and sample of fine softwood + 10% H2O in DES) were also taken into account. The stirring speed of PTFE centrifugal stirrer paddles was 100 rpm and reaction time was adjusted to 16 hours. The load of saw dust was 5 wt % in DES solution. The ChCh BA DES (molar ratio 5 : 3) solutions were prepared using dry salts, which were mixed and heated up to the reaction temperature. The ChCI-Ba DES formed a clear solution when the temperature was reached 65-70 °C. Dry wood material was added slowly under mechanical stirring to ensure good mixing of solution and wood . The fractionation study was continued at elevated fractionation temperature of 110°C. The fractionation efficiency of ChCh BA DES with different wood samples at three fractionation temperature is presented in Figure 3 and Table 1. Gravimetric fraction distribution in percentage of the fractionated wood samples of the whole mass in DES screening tests at 95°C is shown in Figure 3. The better the fractionation ability, the better the wood meal settle to smaller fractions. The influence of refining the samples can be seen in case of TMP at 95°C. Comparison of the samples SW coarse and SW fine shows clearly the effect of the particle size, while finer particle size fractionate more easily to smaller cuts.

The following Table 1 shows the fractionation yields of smallest fraction (particle size < 150μιη) in the experiments of softwood using ChCh BA (molar ration of 5 : 3) DES solution. As a reference, the fractionation tests of saw dusts were done only in water, gave for coarse 3.4 %, fine 2.0 % and TMP 4.1 % as finest precipitates.

Table 1

The monosaccharide composition (mg/100 mg of dry matter) in coarse (1 mm) and finest particle size fractions (< 150 μιη) of the experiments performed at 95°C are presented in Table 2 below. Monosaccharides of hemicelluloses are highlighted. Table 2 also shows the percentage portions of lignin in fractions. Table 2.

Example 3

5-HMF, furfural, formic acid, acetic acid and levulinic acid in the DES solutions of example 2

UV/VIS spectroscopy measurements of six different acidic ChCh BA DES sample solutions obtained in the treatment at 95 °C in example 2 (Figure 4) . The signal at 283 nm indicates the presence of furans (5-hydroxymethylfurfural, furfural) . Capillary electrophoresis was used for the quantitative analysis of those compounds, and degradation components of furans. This was done for the experiments carried out for the 95°C and 110°C experiments. High acidity of ChCh BA DES promotes the formation of 5-hydroxymethylfurfural from hexoses and in smaller extent the formation of furfural from pentoses of hemicelluloses.

The yield of furfural was increased with elevated temperature. The degradation reactions of both 5-hydroxymethylfurfural and furfural produce formic, acetic and levulinic acids. The concentration of levulinic acid increased at the temperature of 110°C. Table 3 presents amounts of 5-hydroxymethylfurfural, furfural, formic acid, acetic acid and levulinic acid in the DES solutions in the 75°C, 95°C and 110°C experiments in mg/g of dry wood. Acid content was determined only for 95°C and 110°C experiments.

Table 3

Example 4

Production of 5-hydroxymethylfurfural and furfural The production of 5-hydroxymethylfurfural and furfural was studied. The amount of water was increased from 0 to 25 % in relation to the whole mass (reaction mixture). The procedure as described in example 2 was used . The highest amounts of 5- hydroxymethylfurfural and furfural were in the case of 10 % water. Figure 5 shows UV-measurements of 5-hydroxymethylfurfural and furfural from the water addition test 0, 5, 10, 15, 20 and 25 %. Wood meal was spruce fine sawdust. The signal at 283 nm indicates the presence of furans (5-hydroxymethylfurfural, furfural). High acidity of ChCh BA DES promotes the formation of 5-hydroxymethylfurfural from hexoses and in smaller extent the formation of furfural from pentoses of hemicelluloses. The higher water content (10 %) favored the production of furans. The degradation reactions of both 5-hydroxymethylfurfural and furfural produce formic, acetic and levulinic acids. Example 5

Producing of magnetic lignin particles

Lignin (1.0 g) was dissolved in 3 : 2 choline chloride: boric acid DES-solution (20.0 g) for 2 h at 60°C to obtain a 5 wt% brown and viscous solution. Then, Fe30₄ particles (0.25 g) were added to the solution and the solution was homogenized by continuous vigorous mechanical stirring for 20 min at 60°C. The mixture was then precipitated by pouring it into excess of cold distilled water, mixing the aqueous solution for 15 min, and filtering the solid particles, followed by extensive washing with cold distilled water. Optionally, the particles can be dialyzed using distilled water by a membrane with a cutoff (MWCO) of 1000 Da to reach higher purity.

The present invention has been described herein with reference to specific embodiments. It is, however clear to those skilled in the art that the process and products may be varied within the scope of the claims.

Claims

1. A process for converting biomass, characterized in that the process comprises the steps, where in the first step biomass comprising lignin, hemicellulose or combinations thereof is mixed with a DES to obtain a biomass mixture, in the second step water is added to the biomass mixture and an aqueous biomass mixture is obtained, the aqueous biomass mixture is separated into a non-solubilized fiber fraction, precipitated lignin fraction and a liquid fraction, and

in the third step the liquid fraction is heated to a temperature between 80°C and 130°C, and at least one of furfural, 5-hydroxymethylfurfural levulinic acid and formic acid is formed and separated .

2. The process according to claim 1, characterized in that the DES comprises a (2-R-ethyl)-trimethylammonium salt, or a mixture of said salts, and a Lewis acid selected from boric acid, meta-boric acid, boronic acid, borinic acid, alkyl borates, hydrated borate salts, pyruvic acid and any combinations thereof.

3. The process according to claim 1 or 2, characterized in that the DES comprises choline chloride and boric acid.

4. The process according to any one of claims 1-3, characterized in that the biomass mixture contains 2-40 wt%, preferably 5-25 wt% of the biomass, calculated based on dry weight.

5. The process according to any one of claims 1-4, characterized in that the biomass mixture contains water not more than 10 wt%, calculated from the total weight of the biomass mixture.

6. The process according to any one of claims 1-5, characterized in that in the first step the pressure is 100 mbar - 20 bar.

7. The process according to any one of claims 1-6, characterized in that spherical particles or balls are used in the first step.

8. The process according to claim 7, characterized in that the spherical particles or balls have a diameter from 100 μιη to 5 mm.

9. The process according to any one of claims 1-7, characterized in that the non- solubilized fiber fraction is washed with water or organic solvent selected from lower alkyl alcohols, lower ketones, tetrahydrofuran, DMSO, or combinations thereof.

10. The process according to any one of claims 1-9, characterized in that the non- solubilized fiber fraction is separated and subjected to fibrillation.

11. The process according to any one of claims 1-10, characterized in that water having a temperature between 40 and 90°C is added to the biomass mixture obtained from the first step to obtain a volumetric ratio 10 : 1- 1 : 1 of water with respect to DES, and lignin is precipitated.

12. The process according to any one of claims 1-11, characterized in that in the third step the temperature of the liquid fraction is adjusted to 80°C -100°C, where furfurals are obtained.

13. The process according to any one of claims 1-11, characterized in that in the third step the temperature of the liquid fraction is adjusted to 102°C -115°C, whereby levulinic acid is obtained.

14. The process according to any one of claims 1-11, characterized in that in the third step the temperature of the liquid fraction is adjusted above 115°C, whereby formic acid is obtained

15. The process according to any one of claims 1-14, characterized in that 2-40 wt% of lignin obtained in the second step or of a mixture of chitosan and said lignin, is mixed with a DES to obtain a lignin-DES mixture, and 0.1-100 wt% of magnetic material selected from Fe30₄, Nb and Nd, calculated respect to the amount of lignin or to the mixture of lignin and chitosan, is mixed with the lignin- DES mixture, whereby magnetic lignin particles are precipitated.

16. The process according to any one of claims 1-15, characterized in that DES is separated from liquid fraction or fractions by removing water and possible organic solvents and recycled to the first step of the process.

17. Magnetic lignin particles comprising lignin and magnetic material selected from Fe30₄, Nb and Nd, preferably Fe30₄.

18. The magnetic lignin particles according to claim 17, characterized in that the magnetic lignin particles comprise chitosan.

19. The magnetic lignin particles according to claim 17 or 18, characterized in that the lignin is cationized or anionized lignin.

20. The magnetic lignin particles according to any one of claims 17 - 19, characterized in that the magnetic lignin particles are obtained by the process according to claim 15 or 16.