A method to extract a primary lignin

Abstract

The present invention relates to the field of extraction of lignin wherein lignin is separated into a primary lignin. In one aspect, the present invention concerns a method to extract a primary lignin from lignocellulosic biomass comprising lignin. By providing a lignocellulosic biomass and a mixture of water and alcohol in a reactor, maintaining a temperature between 110°C and 180°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Adding water to the removed extract to allow a part of the dissolved lignin to precipitate forming a primary lignin and separate it from the solution. In another aspect, the present invention concerns an isolated lignin obtained by the method as a primary lignin.

Description

[0001] A method to extract a primary lignin and a primary lignin Field of the invention

[0002] The present invention relates to the field of extraction of a primary lignin and a secondary lignin from lignocellulosic biomass. More specifically, the present invention provides an alternative method wherein lignin dissolved in a solvent comprising water and alcohol, is separated into a primary lignin and a secondary lignin through a sequence of precipitation steps. In another aspect, the present invention relates to an alternative method to extract a primary lignin. In another aspect, the present invention relates to a primary lignin extracted by an alternative method.

[0003] Background of the invention

[0004] Lignin is a complex and high molecular weight polymer that constitutes about a quarter to a third of the dry weight of lignocellulosic biomass. It is one of the most abundant sources of aromatics found in nature and may be used for functional materials derived from renewable feedstocks.

[0005] Conventional methods for extraction include the so called organosolv process, wherein a solvent comprising water and alcohol is used to dissolve lignin in lignocellulosic biomass.

[0006] Some of the functional groups of lignin are reactive and the extraction method may alter the structure for example by condensation reactions. Also, the dissolution is accompanied by some fragmentation of the native lignin structure. Therefore, dissolved lignin typically comprises heterogeneous fractions of lignin and it is challenging to separate the lignin and other compounds from each other at high yield. Traditional methods of lignin extraction do not separate between different fractions of the dissolved lignin, which may limit the potential applications of the extracted lignin.

[0007] Depending on the properties of the extracted lignin, lignin could find applications in a diverse range of products. Traditionally, a high phenolic hydroxyl content of lignin has been positively correlated with both antioxidant activity and dark color of the lignin.

[0008] Thus, there are drawbacks associated with conventional methods for lignin extraction.

[0009] Summary of the invention

[0010] The objective of the present invention is to overcome the drawbacks of the prior art and improve the methods for lignin extraction from lignocellulosic biomass.

[0011] In a first aspect, the present invention concerns a method to extract a primary lignin and a secondary lignin from lignocellulosic biomass comprising lignin. The method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol and water. Maintaining a temperature between 110°C and 160°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary lignin and a secondary solution. Separate the primary lignin from the secondary solution. Evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming secondary lignin and a third solution. Separate the secondary lignin from the third solution. In another aspect, the present invention concerns an isolated lignin obtained by the method as a primary lignin according to the first aspect.

[0012] In a third aspect, the present invention concerns a method to extract a primary lignin from lignocellulosic biomass comprising lignin, wherein the method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol, water and optionally mineral acid. Maintaining a temperature between 110°C and 180°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution. Separate the primary lignin from the secondary solution.

[0013] In a fourth aspect, the present invention concerns an isolated lignin obtained by the method as a primary lignin according to the third aspect.

[0014] Brief description of figures

[0015] Figure 1 depicts reflectance as a function of wavelength for lignin according to example 2, 3, 4 as well as according to comparative example 2 and 3.

[0016] Figure 2 depicts a photograph of primary lignin (left) according to example 1 and a secondary lignin (right) according to example 1.

[0017] Itemized embodiments

[0018] In one embodiment according to the first aspect, the present invention concerns a method to extract a primary lignin and a secondary lignin from lignocellulosic biomass comprising lignin. The method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol, water and optionally mineral acid, and maintaining a temperature between 110°C and 160°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution, wherein the precipitate formed by water addition is the primary lignin. Separate the primary lignin from the secondary solution. Evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension comprising a secondary lignin and a third solution, wherein the precipitate formed by alcohol evaporation is the secondary lignin. Separate the secondary lignin from the third solution. In another embodiment according to the first aspect, the present invention concerns a method wherein if the temperature in the reactor was maintained at a temperature above 130°C the extract is filtered prior to the addition of water to the removed extract. Preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

[0019] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of alcohol in the solvent is between 40 wt% and 80 wt%, preferably between 50 wt% and 70 wt%, more preferably between 55 wt% and 65 wt%.

[0020] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of water in the solvent is between 20 wt% and 60 wt%, preferably between 50 wt% and 30 wt%, more preferably between 45 wt% and 35 wt%.

[0021] In another embodiment according to the first aspect, the present invention concerns a method wherein the mineral acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof, preferably wherein the mineral acid is sulfuric acid. Preferably the amount of mineral acid in the solvent is between 0.2 wt% and 2 wt%.

[0022] In another embodiment according to the first aspect, the present invention concerns a method wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6.

[0023] In another embodiment according to the first aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 160°C the pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least a part of the lignocellulosic biomass to be dissolved to form the extract.

[0024] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of extract removed from the reactor is between 5 wt% and 50 wt% compared to the mass of solvent in the reactor. Preferably the amount of extract removed from the reactor is between 10 wt% and 30 wt%. In another embodiment according to the first aspect, the present invention concerns a method wherein the primary lignin is separated from the secondary solution by sedimentation and / or filtration.

[0025] In another embodiment according to the first aspect, the present invention concerns wherein the secondary lignin separated from the third solution by sedimentation and / or filtration.

[0026] In another embodiment according to the first aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding additional solvent to the reactor, and after the addition of additional solvent, maintaining a temperature between 110°C and 160°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract, and removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. In another embodiment according to the first aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 160°C the pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0027] In another embodiment according to the first aspect, the present invention concerns a method wherein the temperature is maintained between 110°C and 160°C in the reactor for a duration of less than 120 minutes, preferably a duration of less than 110 minutes, more preferably for a duration of less than 100 minutes, wherein the duration is measured between the addition of solvent or the addition of additional solvent in the reactor and the removal of at least a part of the extract from the reactor. In another embodiment according to the first aspect, the present invention concerns a method wherein, after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6.

[0028] In one embodiment according to the first aspect, the present invention concerns wherein the temperature is maintained between 120°C and 150°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0029] In one embodiment according to a second aspect, the present invention concerns an isolated lignin obtained by the method according to the first aspect.

[0030] In an embodiment according to a third aspect, the present invention concerns a method to extract a primary lignin from lignocellulosic biomass comprising lignin. The method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol, water and optionally mineral acid. Maintaining a temperature between 110°C and 180°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution, wherein the precipitate formed by water addition is the primary lignin. Separate the primary lignin from the secondary solution.

[0031] In another embodiment according to the third aspect, the extract is filtered prior to the addition of water to the removed extract, preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

[0032] In another embodiment according to the third aspect, if the temperature in the reactor was maintained at a temperature above 130°C the extract is filtered prior to the addition of water to the removed extract, preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

[0033] In another embodiment according to the third aspect, the amount of alcohol in the solvent is between 30 wt% and 70 wt%, preferably between 35 wt% and 65 wt%, more preferably between 40 wt% and 60 wt%.

[0034] In another embodiment according to the third aspect, the mineral acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof, preferably wherein the mineral acid is sulfuric acid. Preferably the amount of mineral acid in the solvent is between 0.2 wt% and 2 wt%.

[0035] In another embodiment according to the third aspect, the present invention concerns a method wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 7, preferably between 2 and 6, more preferably between 2.5 and 5. In another embodiment according to the third aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least a part of the lignocellulosic biomass to be dissolved to form the extract.

[0036] In another embodiment according to the third aspect, the present invention concerns a method wherein the amount of extract removed from the reactor is between 5 wt% and 50 wt% compared to the mass of solvent in the reactor. Preferably the amount of extract removed from the reactor is between 10 wt% and 30 wt%. In another embodiment according to the third aspect, the present invention concerns a method wherein the primary lignin is separated from the secondary solution by sedimentation, centrifugation and / or filtration.

[0037] In another embodiment according to the third aspect, the amount of water added to the removed extract is between 3 and 0.2 times the amount of the removed extract by volume, preferably wherein the amount of water added to the removed extract is between 2.6 and 0.4 times the amount of the removed extract by volume.

[0038] In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding additional solvent to the reactor, and after the addition of additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract, and removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding at least a part of the secondary solution and additional solvent to the reactor. After the addition of at least a part of the secondary solution and additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract. Subsequently, removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved.

[0039] In another embodiment according to the third aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0040] In another embodiment according to the third aspect, the present invention concerns a method wherein the amount of alcohol in the sum of at least a part of the secondary solution and the additional solvent added to the reactor is between 30 wt% and 70 wt%, preferably between 35 wt% and 65 wt%, more preferably between 40 wt% and 60 wt%.

[0041] In another embodiment according to the third aspect, the present invention concerns a method wherein the temperature is maintained between 110°C and 180°C in the reactor for a duration of less than 120 minutes, preferably a duration of less than 110 minutes, more preferably for a duration of less than 100 minutes, wherein the duration is measured between the addition of solvent or the addition of at least a part of the second solution and additional solvent in the reactor and the removal of at least a part of the extract from the reactor.

[0042] In another embodiment according to the third aspect, the present invention concerns a method wherein, after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6.

[0043] In another embodiment according to the third aspect, the present invention concerns a method wherein the temperature is maintained between 120°C and 175°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Preferably, the present invention concerns a method wherein the temperature is maintained between 120°C and 160°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0044] In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises the steps of evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension comprising a secondary lignin and a third solution, and separate the secondary lignin from the third solution. In another embodiment according to the third aspect, the present invention concerns a method wherein the secondary lignin is separated from the third solution by sedimentation and / or filtration. In one embodiment according to a fourth aspect, the present invention concerns an isolated lignin obtained by the method according to the third aspect.

[0045] Detailed description of the invention

[0046] According to the first aspect, the present invention concerns a method to extract a primary lignin and a secondary lignin from lignocellulosic biomass comprising lignin. The method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol, water and optionally mineral acid, and maintaining a temperature between 110°C and 160°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution, wherein the precipitate formed by water addition is primary lignin. Separate the primary lignin from the secondary solution. Evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension comprising a secondary lignin and a third solution, wherein the precipitate formed by alcohol evaporation is the secondary lignin. Separate the secondary lignin from the third solution.

[0047] A method to extract lignin according to the above enables separation of fractions of dissolved lignin into a primary lignin and a secondary lignin with distinct properties.

[0048] A method to extract a primary lignin and a secondary lignin according to the above results in a primary lignin exhibiting high reflectance of light with wavelengths in the visible range, i.e. between 380 nm and 750 nm, in combination with high absorption of light with wavelengths in the ultraviolet (UV) range, i.e. between 100-400 nm, whereas the secondary lignin exhibits low reflectance of light with wavelengths in the visible range.

[0049] Furthermore, a method to extract a primary lignin and a secondary lignin according to the above results in a primary lignin exhibiting high antioxidant activity.

[0050] Additionally, a method to extract lignin according to the above enables separation of fractions of dissolved lignin into a primary lignin and a secondary lignin and results in a high overall yield of extracted lignin.

[0051] Thus, a method to extract lignin according to the above results in a combination of properties related to the fractions that are prone to precipitate as a response to water addition, i.e. the primary lignin, and the fractions that are prone to precipitate as a response to evaporation of alcohol, i.e. secondary lignin.

[0052] The lignocellulosic biomass comprising lignin may be of any origin as the method described herein is of general character. As recognized by a skilled person it may be of particular interest to use wood, such as softwood and / or hardwood due to their relatively high lignin content.

[0053] The solvent is a mixture of alcohol, water and optionally mineral acid and is beneficial for the yield of lignin as the combination enhances solubility of lignin and selectivity to extract lignin compared to other components of lignocellulosic biomass. Additionally, a solvent comprising alcohol enables a method wherein lignin may be precipitated by the evaporation of alcohol from extract. As recognized by a skilled person, relevant alcohols may be (but are not limited to) ethanol, methanol, butanol, isopropanol or a combination thereof.

[0054] By maintaining a temperature above 110°C lignin is more prone to dissolve in the solvent thereby increasing the yield of extracted primary lignin and secondary lignin, respectively. By maintaining a temperature below 160°C, the properties related to UV absorption and antioxidant activity in combination with reflectance of visible light is preserved for the primary lignin. Without being bound by theory, the elevated temperatures above 160°C may promote irreversible structural changes that cause the primary lignin to change properties.

[0055] Addition of water to the removed extract allows at least a part of the dissolved lignin to precipitate to form a primary lignin. In other words, the addition of water induces nucleation and / or aggregation of dissolved lignin fractions prone to precipitate as a result of water addition.

[0056] Separation of primary lignin from the secondary solution, enable further processing to precipitate another fraction of the dissolved lignin in the secondary solution.

[0057] Evaporation of alcohol from the secondary solution allows at least another part of the dissolved lignin to precipitate to form a secondary lignin.

[0058] In another embodiment according to the first aspect, the present invention concerns a method wherein if the temperature in the reactor was maintained at a temperature above 130°C the extract is filtered prior to the addition of water to the removed extract. By filtering the extract, the yield of the primary lignin is further improved. Preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

[0059] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of alcohol in the solvent is between 40 wt% and 80 wt%. By using such solvent, the yield of the primary lignin and secondary lignin is further improved. Preferably the amount of alcohol in the solvent is between 50 wt% and 70 wt%, more preferably the amount of alcohol in the solvent is between 55 wt% and 65 wt%.

[0060] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of water in the solvent is between 20 wt% and 60 wt%. By using such solvent, the yield of the primary lignin and secondary lignin is further improved. Preferably the amount of water in the solvent is between 50 wt% and 30 wt%, more preferably the amount of water in the solvent is between 45 wt% and 35 wt%.

[0061] In another embodiment according to the first aspect, the present invention concerns a method wherein the mineral acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof. A catalytic amount of mineral acid increases the efficiency of the extraction. Preferably wherein the mineral acid is sulfuric acid. Preferably the amount of mineral acid in the solvent is between 0.2 wt% and 2 wt%.

[0062] In another embodiment according to the first aspect, the present invention concerns a method wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8. By having a mass ratio between the solvent compared to the dry weight of lignocellulosic biomass above 1 the amount of solvent is sufficient to dissolve lignin. By having a mass ratio between the solvent compared to the dry weight of lignocellulosic biomass below 8 the amount of extracted primary lignin with respect to the amount of solvent is improved. Preferably the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 2 and 7, more preferably between 3 and 6.

[0063] In another embodiment according to the first aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 160°C the pressure in the reactor is maintained between 2 bar and 14 bar. By having a pressure between 2 bar and 14 bar, the yield of primary lignin and secondary lignin is high in combination a low complexity of equipment required for the method thereby resulting in an efficient the extraction of lignin. Preferably while the temperature in the reactor is maintained between 110°C and 160°C the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least a part of the lignocellulosic biomass to be dissolved to form the extract.

[0064] In another embodiment according to the first aspect, the present invention concerns a method wherein the amount of extract removed from the reactor is between 5 wt% and 50 wt% compared to the mass of solvent in the reactor. By removing between 5 wt% and 50 wt% of extract from the reactor the efficiency of the extraction method is further improved. Preferably the amount of extract removed from the reactor is between 10 wt% and 30 wt%.

[0065] In another embodiment according to the first aspect, the present invention concerns a method wherein the primary lignin is separated from the secondary solution by sedimentation and / or filtration. Sedimentation and / or filtration is beneficial approach to collect and separate the primary lignin. In another embodiment according to the first aspect, the present invention concerns wherein the secondary lignin is separated from the third solution by sedimentation and / or filtration. Sedimentation and / or filtration is beneficial approach to collect and separate the secondary lignin.

[0066] In another embodiment according to the first aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding additional solvent to the reactor, and after the addition of additional solvent, maintaining a temperature between 110°C and 160°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract, and removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. By the method defined in this section the efficiency of the lignin extraction is further improved. In another embodiment according to the first aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 160°C the pressure in the reactor is maintained between 2 bar and 14 bar. This further improves the yield of the extraction. Preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0067] In another embodiment according to the first aspect, the present invention concerns a method wherein the temperature is maintained between 110°C and 160°C in the reactor for a duration of less than 120 minutes, wherein the duration is measured between the addition of solvent or the addition of additional solvent in the reactor and the removal of at least a part of the extract from the reactor. By using a duration of less than 120 min the properties related to UV absorption and antioxidant activity in combination with reflectance of visible light is preserved forthe primary lignin. Without being bound by theory, longer durations may promote irreversible structural changes that cause the primary lignin to change properties. Preferably a duration of less than 110 minutes, more preferably for a duration of less than 100 minutes.

[0068] In another embodiment according to the first aspect, the present invention concerns a method wherein, after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6. This further improves the efficiency of the extraction.

[0069] In one embodiment according to the first aspect, the present invention concerns a method wherein the temperature is maintained between 120°C and 150°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. This further improves the yield of the extracted primary lignin and secondary lignin.

[0070] In one embodiment according to a second aspect, the present invention concerns an isolated lignin obtained by the method to obtain a primary lignin according to the first aspect.

[0071] In an embodiment according to a third aspect, the present invention concerns a method to extract a primary lignin from lignocellulosic biomass comprising lignin. The method comprises providing a lignocellulosic biomass and a solvent in a reactor, wherein the solvent is a mixture of alcohol, water and optionally mineral acid. Maintaining a temperature between 110°C and 180°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor. Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution, wherein the precipitate formed by water addition is the primary lignin. Separate the primary lignin from the secondary solution. A method to extract lignin according to the above enables separation of fractions of dissolved lignin into a primary lignin with distinct properties. Notably, the primary lignin has a combination of particularly high reflectance of visible light as well as high antioxidant scavenging activity.

[0072] A method to extract a primary lignin and a secondary lignin according to the above results in a primary lignin exhibiting high reflectance of light with wavelengths in the visible range, i.e. between 380 nm and 750 nm, in combination with high absorption of light with wavelengths in the ultraviolet (UV) range, i.e. between 100-400 nm.

[0073] Furthermore, a method to extract a primary lignin according to the third aspect results in a primary lignin exhibiting high antioxidant activity.

[0074] Additionally, a method to extract lignin according to the above enables high yield of a fractions of lignin with particularly high reflectance and high antioxidant activity.

[0075] Thus, a method to extract lignin according to the above results in a combination of properties related to the fractions that are prone to precipitate as a response to water addition, i.e. the primary lignin. The lignocellulosic biomass comprising lignin may be of any origin as the method described herein is of general character. As recognized by a skilled person it may be of particular interest to use wood, such as softwood and / or hardwood due to their relatively high lignin content.

[0076] The solvent is a mixture of alcohol, water and optionally mineral acid and is beneficial for the yield of lignin as the combination enhances solubility of lignin and selectivity to extract lignin compared to other components of lignocellulosic biomass. Additionally, a solvent comprising alcohol enables a method wherein lignin may be precipitated by the evaporation of alcohol from extract. As recognized by a skilled person, relevant alcohols may be (but are not limited to) ethanol, methanol, butanol, isopropanol or a combination thereof.

[0077] By maintaining a temperature above 110°C lignin is more prone to dissolve in the solvent thereby increasing the yield of extracted primary lignin and secondary lignin, respectively. By maintaining a temperature below 180°C, the properties related to UV absorption and antioxidant activity in combination with reflectance of visible light is preserved for the primary lignin. Without being bound by theory, the elevated temperatures above 180°C may promote irreversible structural changes that cause the primary lignin to change properties.

[0078] Addition of water to the removed extract allows at least a part of the dissolved lignin to precipitate to form a primary lignin. In other words, the addition of water induces nucleation and / or aggregation of dissolved lignin fractions prone to precipitate as a result of water addition. In another embodiment according to the third aspect, the present invention concerns a method wherein the extract is filtered prior to the addition of water to the removed extract. By filtering the extract, the yield of the primary lignin is further improved. Preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh. As also seen in the comparative examples, the filtering the extract will result in a lignin with a combination of high reflectance and high antioxidant activity. A filter with at least mesh 28 is for the purpose of the present disclosure denoting suitable size of the filter openings (although technically this standardized mesh sizing system refer to 28 openings per linear inch of the material). A skilled person will recognize that non-woven filters with the similar sized openings corresponding to mesh 28 and mesh 35 may be used.

[0079] In another embodiment according to the third aspect, the present invention concerns a method wherein if the temperature in the reactor was maintained at a temperature above 130°C the extract is filtered prior to the addition of water to the removed extract. By filtering the extract, the yield of the primary lignin is further improved. Preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

[0080] In another embodiment according to the third aspect, the amount of alcohol in the solvent is between 30 wt% and 70 wt%. By using such solvent, the yield of the primary lignin and secondary lignin is further improved. Preferably the amount of alcohol in the solvent is between 35 wt% and 65 wt%, more preferably the amount of alcohol in the solvent is between 40 wt% and 60 wt%.

[0081] As understood by a skilled person, the lignocellulosic biomass may comprise water when provided to the reactor. For instance, sawdust comprising 40 wt% water may be added to the reactor, and the water brought along with the sawdust is regarded as a part of the solvent in the reactor and is accounted for instance with respect to the amount of alcohol in the solvent in the reactor.

[0082] In another embodiment according to the third aspect, the mineral acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof. A catalytic amount of mineral acid increases the efficiency of the extraction. Preferably wherein the mineral acid is sulfuric acid. Preferably the amount of mineral acid in the solvent is between 0.2 wt% and 2 wt%.

[0083] In another embodiment according to the third aspect, the present invention concerns a method wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 7. By having a mass ratio between the solvent compared to the dry weight of lignocellulosic biomass above 1 the amount of solvent is sufficient to dissolve lignin. By having a mass ratio between the solvent compared to the dry weight of lignocellulosic biomass below 7 the amount of extracted primary lignin with respect to the amount of solvent is improved. Preferably the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 2 and 6, more preferably between 2.5 and 5.

[0084] As understood by a skilled person, the lignocellulosic biomass may comprise water when provided in the reactor. In such cases, the water that is provided along with the lignocellulosic biomass is considered a part of the solvent, and the ratio of solvent compared to the dry weight of lignocellulosic biomass accounts for water added along with the lignocellulosic biomass.

[0085] In another embodiment according to the third aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 2 bar and 14 bar. This further improves the yield of the extraction. Preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

[0086] In another embodiment according to the third aspect, the present invention concerns a method wherein the amount of extract removed from the reactor is between 5 wt% and 50 wt% compared to the mass of solvent in the reactor. By removing between 5 wt% and 50 wt% of extract from the reactor the efficiency of the extraction method is further improved. Preferably the amount of extract removed from the reactor is between 10 wt% and 30 wt%.

[0087] In another embodiment according to the third aspect, the present invention concerns a method wherein the primary lignin is separated from the secondary solution by sedimentation, centrifugation and / or filtration. This further enables collection of a primary lignin which exhibits a combination of high reflectance of light with wavelengths in the visible range, i.e. between 380 nm and 750 nm, in combination with high absorption of light with wavelengths in the ultraviolet (UV) range, i.e. between 100-400 nm, as well as high antioxidant activity.

[0088] In another embodiment according to the third aspect, the amount of water added to the removed extract is between 3 and 0.2 times the amount of the removed extract by volume. The amount of water added to the removed extract surprisingly affected the reflectance of the obtained lignin. An amount in the range above resulted in high yield of a lignin with high reflectance as well as high antioxidant activity. Preferably the amount of water added to the removed extract is between 2.6 and 0.4 times the amount of the removed extract by volume.

[0089] In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding additional solvent to the reactor, and after the addition of additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract, and removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. By removing a part of the extract and addition of additional solvent, according to the method specified herein, the yield of extracted lignin increased, which is further supported by the results presented in following sections.

[0090] In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises after removing the at least a part of the extract from the reactor, adding at least a part of the secondary solution and additional solvent to the reactor. After the addition of at least a part of the secondary solution and additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract. Subsequently, removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. By removing a part of the extract and addition of secondary solution and additional solvent, according to the method specified herein, the yield of extracted lignin increased, which is further supported by the results presented in following sections. Also, surprisingly, the reuse of secondary solution as a solvent in the reactor did not cause the extracted lignin to reduce its reflectance and antioxidant activity.

[0091] In another embodiment according to the third aspect, the present invention concerns a method wherein while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 2 bar and 14 bar. By having a pressure between 2 bar and 14 bar, the yield of primary lignin and secondary lignin is high in combination a low complexity of equipment required for the method thereby resulting in an efficient the extraction of lignin. Preferably while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least a part of the lignocellulosic biomass to be dissolved to form the extract.

[0092] In another embodiment according to the third aspect, the present invention concerns a method wherein the amount of alcohol in the sum of at least a part of the secondary solution and the additional solvent added to the reactor is between 30 wt% and 70 wt%. This further improves the yield of a lignin with high reflectance as well as high antioxidant activity. Preferably the amount of alcohol is between 35 wt% and 65 wt%, more preferably between 40 wt% and 60 wt%.

[0093] In another embodiment according to the third aspect, the present invention concerns a method wherein the temperature is maintained between 110°C and 180°C in the reactor for a duration of less than 120 minutes. By using a duration of less than 120 min the properties related to UV absorption and antioxidant activity in combination with reflectance of visible light is preserved for the primary lignin. Without being bound by theory, longer durations may promote irreversible structural changes that cause the primary lignin to change properties. Preferably a duration of less than 110 minutes, more preferably for a duration of less than 100 minutes.

[0094] In another embodiment according to the third aspect, the present invention concerns a method wherein, after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6. This further improves the efficiency of the extraction.

[0095] In another embodiment according to the third aspect, the present invention concerns a method wherein the temperature is maintained between 120°C and 175°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. This further improves the efficiency of the extraction. Preferably, the present invention concerns a method wherein the temperature is maintained between 120°C and 160°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. This further improves the efficiency of the extraction.

[0096] In another embodiment according to the third aspect, the present invention concerns a method wherein the method comprises the steps of evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension comprising a secondary lignin and a third solution, and separate the secondary lignin from the third solution. This enables separation effractions of dissolved lignin into a primary lignin and yet another secondary lignin and results in a high overall yield of extracted lignin.

[0097] In another embodiment according to the third aspect, the present invention concerns a method wherein the secondary lignin is separated from the third solution by sedimentation and / or filtration. Sedimentation and / or filtration is beneficial approach to collect and separate the primary lignin. In one embodiment according to a fourth aspect, the present invention concerns an isolated lignin obtained by the method according to the third aspect. In one embodiment, the method according to the present invention the method comprises providing a lignocellulosic biomass and a solvent in a reactor. The solvent is a mixture of ethanol, water and a catalytic amount of sulfuric acid, and wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 4 and 5. Maintaining a temperature between 120°C and 150°C and pressure between 5 bar and 10 bar in the reactor to allow at least a part of the lignin to be dissolved to form an extract. Removing at least a part of the extract from the reactor, wherein the part removed from the reactor is between 10 wt% and 20 wt%. After removing the at least a part of the extract from the reactor, i) aciding additional solvent to the reactor, wherein after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 4 and 5. After the addition of additional solvent, ii) maintaining a temperature between 120°C and 150°C and pressure between 5 bar and 10 bar in the reactor, to allow at least another part of the lignin to be dissolved to form the extract; and Hi) removing at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved. In some embodiments according to the present invention i) followed by ii) followed by Hi) is performed in a sequence between two and eight times.

[0098] In some embodiments according to the first aspect, the method comprises adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the amount of water is between 1.5 to 2.0 times the amount of removed extract. The primary suspension comprises a primary lignin and a secondary solution, wherein the precipitate formed by water addition is the primary lignin. Separate the primary lignin from the secondary solution. Evaporate the alcohol from the secondary solution in a rotary evaporator to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension, wherein the evaporated alcohol is collected, and wherein the secondary suspension comprises a secondary lignin and a third solution, wherein the precipitate formed by alcohol evaporation is the secondary lignin. Separate the secondary lignin from the third solution.

[0099] Although the present disclosure has been described with reference to specific embodiments, it will be apparent to those skilled in the art that many variations and modifications may be done within the scope of the present disclosure as described in the specification and defined with reference to the claims below.

[0100] Examples

[0101] Example 1 - Lignin H:

[0102] Sawdust from softwood was used as lignocellulosic biomass. 833 g of sawdust and 100 g of water was added to a reactor. The dry content of the added sawdust was 60 wt%, i.e. the corresponding dry weight of the sawdust was 500 g. The reactor was heated to a temperature of 125°C.

[0103] A mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent, and the solvent was heated in a separate compartment. Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust while the temperature in the reactor was maintained at 125°C and the pressure was maintained between 3 bar and 3.5 bar.

[0104] The temperature in the reactor was maintained at 125°C and the pressure was maintained between 3 bar and 3.5 bar for an additional 10-15 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract.

[0105] 340 g of extract was removed from the reactor. In total, the time from heating the reactor comprising the sawdust and water to 125°C until a part of the extract was removed was 90 minutes.

[0106] After the first removal of extract according to above, extract was also formed by addition of additional solvent and allowing at least another part of the lignin to dissolve in four so called cycles. After removing the 340 g of extract, each cycle was initiated by the addition of 340 g of additional solvent to the reactor and the temperature in the reactor was maintained at 125°C and the pressure was maintained between 3 bar and 3.5 bar to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Thereafter, the cycles were ended by removing another 340 g of extract from the reactor. In total, the time for each cycle from the addition of additional solvent until the removal of another 340 g of extract was 40 min. Finally, about 1750 g of extract was removed from the reactor.

[0107] For each 340 g part of extract removed from the reactor, 340 g of water was added to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution.

[0108] The primary lignin was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjd, Qualitative filter paper, Grade 3). For example 1, the primary lignin is denoted lignin H. Ethanol was evaporated using a rotary evaporator from the secondary solution to allow at least another part of the dissolved lignin to precipitate to form a secondary suspension, wherein the secondary suspension comprises a secondary lignin and a third solution. The evaporated ethanol was condensed and collected to be reused for another batch of lignin extraction.

[0109] The secondary lignin was separated from the third solution by collecting the secondary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3). Example 2 - Lignin M

[0110] Sawdust from softwood was used as lignocellulosic biomass. 833 g of sawdust and 100 g of water was added to a reactor. The dry content of the added sawdust was 60 wt%, i.e. the corresponding dry weight of the sawdust was 500 g. The reactor was heated to a temperature of 140°C.

[0111] A mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent, and the solvent was heated in a separate compartment.

[0112] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust while the temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar.

[0113] The temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar for an additional 10-15 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract.

[0114] 340 g of extract was removed from the reactor. In total, the time from heating the reactor comprising the sawdust and solvent to 140°C until a part of the extract was removed was 90 minutes.

[0115] After the first removal of extract according to above, extract was also formed by addition of additional solvent and allowing at least another part of the lignin to dissolve in seven so called cycles. After removing the 340 g of extract, each cycle was initiated by the addition of 340 g of additional solvent to the reactor. For the first three cycles the temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Thereafter, the cycles were ended by removing another 340 g of extract from the reactor. In total, the time from the addition of additional solvent until the removal of another 340 g of extract was 10-15 min for the first three cycles. For the subsequent last four cycles the temperature in the reactor was maintained between 140°C and 143°C and the pressure was maintained between 5.5 bar and 6.5 bar to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Thereafter, the cycles were ended by removing another 340 g of extract from the reactor. In total, the time from the addition of additional solvent until the removal of another 340 g of extract was 40 min for the last four cycles. Finally, about 1750 g of extract was removed from the reactor.

[0116] For each 340 g part of extract removed from the reactor, the extract was filtered through a filter with 40 mesh. Thereafter, 340 g of water was added to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution. The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3). For example 2, the primary lignin is denoted lignin M.

[0117] Ethanol was evaporated from the secondary solution to allow at least another part of the dissolved lignin to precipitate to form a secondary suspension comprising a secondary lignin and a third solution. The secondary lignin was separated from the third solution by collecting the secondary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3).

[0118] Below a summary for example 1 and example 2 is found in the table specifying the reactor conditions for which at least a part of the lignin was allowed to dissolve to form an extract.

[0119] Table 1. Temperature, pressure and time in the reactor for which at least a part of the lignin was allowed to dissolve to form an extract.

[0120]

[0121] Comparative example 1:

[0122] Extract was formed according to example 1.

[0123] For each 340 g part of extract removed from the reactor, 340 g of water was added to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary precipitate and a second solution. Ethanol was evaporated from the primary suspension to allow at least another part of the dissolved lignin to precipitate. The lignin precipitate was separated by allowing sedimentation of the precipitate, removal of the supernate, and collecting the precipitate by filtration (Ahlstrom Munksjd, Qualitative filter paper, Grade 3). The precipitate forms a comparative example of extracted lignin.

[0124] Example 3 - Batch high

[0125] Sawdust from softwood was used as lignocellulosic biomass. Sawdust with a dry content of 60 wt% was added to a reactor and a mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent.

[0126] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust the reactor was heated to a temperature of 162°C under the course of 60 min.

[0127] The temperature in the reactor was maintained around 162°C and the pressure was maintained between 9.5 bar and 10.5 bar for an additional 180 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract. Finally, about 1750 g of extract was removed from the reactor. The extract was removed from the reactor and filtered through a filter with 40 mesh. Thereafter, 340 g of water was added (for every 340 g of extract) to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution.

[0128] The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3). For example 3, the primary lignin is denoted lignin batch high.

[0129] Example 4 - Batch low

[0130] Sawdust from softwood was used as lignocellulosic biomass. Sawdust with a dry content of 60 wt% was added to a reactor and a mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent.

[0131] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust the reactor was heated to a temperature of 100°C. The temperature in the reactor was maintained around 100°C and the pressure was maintained between 0.8 bar and 1.1 bar for an additional 180 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract. Finally, about 1750 g of extract was removed from the reactor. The extract was removed from the reactor and filtered through a filter with 40 mesh. Thereafter, 340 g of water was added (for every 340 g of extract) to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution.

[0132] The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3). For example 4, the primary lignin is denoted lignin batch low.

[0133] Comparative example 2 - Lignin M direct removal of solvent

[0134] Sawdust from softwood was used as lignocellulosic biomass. 833 g of sawdust and 100 g of water was added to a reactor. The dry content of the added sawdust was 60 wt%, i.e. the corresponding dry weight of the sawdust was 500 g. The reactor was heated to a temperature of 140°C.

[0135] A mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent, and the solvent was heated in a separate compartment.

[0136] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust while the temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar.

[0137] The temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar for an additional 10-15 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract.

[0138] 340 g of extract was removed from the reactor. In total, the time from heating the reactor comprising the sawdust and water to 140°C until a part of the extract was removed was 90 minutes.

[0139] After the first removal of extract according to above, extract was also formed by addition of additional solvent and allowing at least another part of the lignin to dissolve in seven so called cycles. After removing the 340 g of extract, each cycle was initiated by the addition of 340 g of additional solvent to the reactor. For the first three cycles the temperature in the reactor was maintained between 138°C and 140°C and the pressure was maintained between 5.2 bar and 5.5 bar to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Thereafter, the cycles were ended by removing another 340 g of extract from the reactor. In total, the time from the addition of additional solvent until the removal of another 340 g of extract was 10-15 min for the first three cycles. For the subsequent last four cycles the temperature in the reactor was maintained between 140°C and 143°C and the pressure was maintained between 5.5 bar and 6.5 bar to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract. Thereafter, the cycles were ended by removing another 340 g of extract from the reactor. In total, the time from the addition of additional solvent until the removal of another 340 g of extract was 40 min for the last four cycles. Finally, about 1750 g of extract was removed from the reactor.

[0140] For each 340 g part of extract removed from the reactor, the extract was filtered through a filter with 40 mesh. Thereafter, rotary evaporator was used to evaporate solvent as well as to precipitate and collect lignin.

[0141] Comparative example 3 - Solid residue from extract

[0142] The solid residue was collected on the filter from Example 2 - Lignin M when the extract was filtered through a filter with 40 mesh (prior to water addition).

[0143] Example 5 - Comparison between batch and cycles

[0144] Lignin was extracted in four separate experiments in accordance with Example 2 - Lignin M, however, the reactor was heated to 123 °C, 127 °C, 137 °C and 146 °C, respectively, (instead of to 140 °C as in Example 2 - Lignin M). Also, the temperature was maintained at 123 °C, 127 °C, 137 °C and 146 °C, respectively, to allow at least a part of the lignin to dissolve in the solvent to form an extract and to allow at least another part of the lignin to dissolve in the solvent to form an extract. The time from heating the reactor until a part of the extract was removed was 90 minutes, and after the first removal the following three cycles were 10 minutes, and the last four cycles were 40 minutes (i.e. 90, 10, 10, 10, 40, 40, 40, and 40 minutes therefore in total 280 minutes).

[0145] Lignin was further extracted in two additional separate experiments in batch, one with at a temperature of 100°C and the other at a temperature of 140°C, respectively according to below. Batch 100°C

[0146] Sawdust from softwood was used as lignocellulosic biomass. Sawdust with a dry content of 60 wt% was added to a reactor and a mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent.

[0147] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust the reactor was heated to a temperature of 100°C under the course of 60 min. The temperature in the reactor was maintained around 100°C for an additional 180 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract (i.e. therefore in total 240 minutes). Finally, about 1750 g of extract was removed from the reactor. The extract was removed from the reactor and filtered through a filter with 40 mesh. Thereafter, 340 g of water was added (for every 340 g of extract) to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution.

[0148] The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3).

[0149] Batch 140° C

[0150] Sawdust from softwood was used as lignocellulosic biomass. Sawdust with a dry content of 60 wt% was added to a reactor and a mixture of ethanol and water (60:40, v / v) with 0.5 wt% sulfuric acid was used as the solvent.

[0151] Solvent was added in three sequences to the reactor, to reach a final mass ratio of 4.5 between the liquid compared to the dry weight of the sawdust the reactor was heated to a temperature of 140°C under the course of 75 min. The temperature in the reactor was maintained around 140°C for an additional 210 minutes, to allow at least a part of the lignin to dissolve in the solvent to form an extract (i.e. therefore in total 285 minutes). Finally, about 1750 g of extract was removed from the reactor. The extract was removed from the reactor and filtered through a filter with 40 mesh. Thereafter, 340 g of water was added (for every 340 g of extract) to allow at least a part of the dissolved lignin to precipitate to form a primary suspension, wherein the primary suspension comprises a primary lignin and a secondary solution.

[0152] The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3).

[0153] Example 6 - Amount of water added to precipitate a primary lignin

[0154] Lignin was extracted in accordance with Example 2 - Lignin M, however, for each part x (x=340 mL) of extract removed from the reactor, 0.2x, 0.5x, lx or 2x parts of water was added to allow at least a part of the dissolved lignin to precipitate to form a primary suspension. In other words, 0.2x corresponds to 68 g of water, 0.5x corresponds to 170 g of water, lx corresponds to 340 g of water, and 2x corresponds to 680 g of water, respectively. The primary precipitate was separated from the secondary solution by allowing sedimentation of the primary lignin, removal of the secondary solution, and collecting the primary lignin by filtration (Ahlstrom Munksjo, Qualitative filter paper, Grade 3).

[0155] Characterization :

[0156] Size-. Weight average molecular weight, number average molecular weight and dispersity was determined by size-exclusion chromatography. Briefly, 8 mg of lignin was dissolved in 2 ml of a 0.5 wt% LiBr solution in dimethyl sulfoxide (DMSO). The samples were filtered using a 0.2 pm NYL syringe filter prior to analysis. The separation was performed with 0.5 wt% LiBr solution in DMSO as eluent at a flow rate of 0.5 ml / min, a column oven temperature of 60°C, and an injection volume of 100 pl.

[0157] UV absorption: The primary lignins according to example 1 and example 2 dissolved in DMSO, respectively, wherein the concentration of lignin was 0.03 mg per mL of DMSO. UV absorption was measured between 255 nm and 400 nm with a broad-spectrum absorption (UVA and UVB).

[0158] Antioxidant activity: The antioxidant activity of the primary lignins according to example 1 and example 2 was measured with a diphenylpicrylhydrazine (DPPH) assay using DMSO, an incubation time of 90 minutes by measurement of absorbance at 517 nm using a UV-vis spectrophotometer, wherein the concentration of lignin was 0.03 mg per mL of DMSO. The absorbance at 517 nm was used to determine the free radical scavenging activity.

[0159] Structure:31P nuclear magnetic resonance (NMR) spectroscopy was used to analyze the hydroxyl functionality of the samples. The samples were prepared by dissolving 30 mg lignin in 100 pl N, / -di methylformamide and 100 pl pyridine, followed by addition of 50 pl of an internal standard solution (60 mg ml^ eHNDI in pyridine, 5 mg ml^ CrfAcAcS) relaxing agent). Finally, 100 pl phosphorylating agent, CI-TMDP, was added, followed by the dropwise addition of 450 pl CDCI3. The spectra were acquired using pulse program "zgig30", 256 scans, an acquisition time of 1.68 s, and a relaxation delay of 5 s at a temperature of 297 K. The data were processed in MestReNova. The data was Fourier transformed, and a Bernstein polynomial fit of the third order corrected the baseline line.

[0160] Heteronuclear single quantum coherence (HSQC) NMR spectroscopy was used to analyze the p-O-4' linkages. The samples were prepared by dissolving 80 mg lignin in 600 pL DMSO-d6. The spectra were acquired using the pulse program "hsqcetgpsi" using 80 scans, an acquisition time of 0.11 s, a relaxation delay of 1.5 s, and a temperature of 297 K, using 1024 x 256 increments. The data were processed in a MestReNova using a 90°-shifted square sine-bell apodization window and 1024 x 1024 data points. The data were Fourier transformed, and the baseline was corrected in both the1H and13C dimensions by a Bernstein polynomial fit of the third order. Solubility: Samples were evaluated by addition of 10 mg of per mL of solvent.

[0161] Results

[0162] Results from size-exclusion chromatography are summarized in the table below.

[0163] Table 2. Weight average molecular weight (Mw), number average molecular weight (Mn) and dispersity (D) was determined by size-exclusion chromatography.

[0164]

[0165] Figure 1 depicts reflectance as a function of wavelength for primary lignin according to Example 2 (2ndcurve from top at 750 nm), Example 3 (3rdcurve from top at 750 nm), Example 4 (top curve at 750 nm), Comparative Example 2 (4thfrom top at 750 nm), and Comparative Example 3 (5thfrom top at 750 nm), respectively.

[0166] As seen in Figure 1, the reflectance at for example 750 nm of lignin extracted in accordance with the first aspect of the present invention (Example 2, Example 3, and Example 4) is higher than lignin extracted in the comparative examples (Comparative Example 2, Comparative Example 3).

[0167] Figure 2 depicts a photograph of primary lignin (left) according to example 1 and a secondary lignin (right) according to example 1.

[0168] UV absorption of the lignin from Example 1 (i.e. Lignin H) was 0.56 at 280 nm (UVB) and 0.21 at 340 nm (UVA). UV absorption of the lignin from Example 2 (i.e. Lignin M) was 0.62 at 280 nm (UVB) and 0.30 at 340 nm (UVA). UV absorption of the lignin from Example 3 (i.e. Batch High) was 0.38 at 280 nm (UVB) and 0.20 at 340 nm (UVA). UV absorption of the lignin from Example 4 (i.e. Batch Low) was 0.45 at 280 nm (UVB) and 0.20 at 340 nm (UVA). UV absorption of the lignin from Comparative Example 2 was 0.58 at 280 nm (UVB) and 0.28 at 340 nm (UVA). UV absorption of the lignin from Comparative Example 3 was 0.76 at 280 nm (UVB) and 0.31 at 340 nm (UVA). Results from UV absorption are summarized in the table below. The primary lignin from example 1 (i.e. Lignin H) exhibited a scavenging activity of 51% according to the DPPH assay, which is indicative of potent antioxidant properties. The primary lignin from example 2 (i.e. Lignin M) exhibited a scavenging activity of 62% according to the DPPH assay, which is indicative of potent antioxidant properties. Results from antioxidant activity are summarized in the table below. The primary lignin from example 1 (i.e. Lignin H) exhibited 3.78 mmol / g of aliphatic hydroxyl groups, 1.62 mmol / g phenolic hydroxyl groups, 0.09 mmol / g carboxylic acid groups, i.e. a total amount of 5.50 mmol / g of hydroxyl groups. The primary lignin from example 2 (i.e. Lignin M) exhibited 2.93 mmol / g of aliphatic hydroxyl groups, 2.20 mmol / g phenolic hydroxyl groups, 0.16 mmol / g carboxylic acid groups, i.e. a total amount of 5.29 mmol / g of hydroxyl groups. Results from31P NMR are summarized in the table below. The primary lignin from example 1 (i.e. Lignin H) exhibited 40 p-O-4' per 100 aromatic units ( / 100 Ar). The primary lignin from example 2 (i.e. Lignin M) exhibited 17 p-O-4' / 100 Ar. Results from HSQC NMR are summarized in the table below.

[0169] The purity of the primary lignin according to example 1 was >99% and the purity of the primary lignin according to example 2 was >99% based on acid hydrolysis and HSQC NMR. Ta b le 3. Summarized results from UV absorption, antioxidant activity,31P NMR and HSQC NMR for the prima ry lignin according to Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and

[0170] Comparative Example 2, respectively.

[0171]

[0172] Table 4. Summarized results of metal content for lignin according to Example 1 and Example 2.

[0173] < <

[0174]

[0175] Table 5. Results from Example 5.

[0176]

[0177] As seen in Table 5, the yield was surprisingly higher for lignin extracted as a primary lignin in accordance with example 5 employing cycles than for lignin extracted in accordance with example 5 employing batch.

[0178] Table 6. Results from Example 6.

[0179]

[0180] As seen in Table 6, the yield of lignin extracted as a primary lignin in accordance with example 6 is dependent of the amount of water added to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution.

[0181] Surprisingly, it was also found that the color of the extracted lignin was dependent on the amount of water added to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary precipitate. When the amount of water added to the extract was between 0.5 to 2 times the amount of extract, the yield of lignin was between 0.7565 g and 0.8918 g and the color was lighter, wherein the lightest color was obtained when the amount of water was equal to the amount of extract. When the amount water exceeded 2 times the amount of extract, the color of the lignin was darker than when the amount of water was around 1 times the amount of extract, and when the amount of water was less than 0.5 times the amount of extract the color of the lignin was darker than when the amount of water was around 1 times the amount of extract.

Claims

Claims1. A method to extract a primary lignin from lignocellulosic biomass comprising lignin, wherein the method comprises:Providing a lignocellulosic biomass and a solvent in a reactor,wherein the solvent is a mixture of alcohol, water and optionally mineral acid; Maintaining a temperature between 110°C and 180°C in the reactor to allow at least a part of the lignin to be dissolved to form an extract;Removing at least a part of the extract from the reactor;Adding water to the removed extract to allow at least a part of the dissolved lignin to precipitate to form a primary suspension comprising a primary lignin and a secondary solution;Separate the primary lignin from the secondary solution.

2. A method according to claim 1, wherein the extract is filtered prior to the addition of water to the removed extract, preferably wherein the extract is filtered through a filter with at least 28 mesh, more preferably wherein the extract is filtered through a filter with at least 35 mesh.

3. A method according to claim 1 or 2, wherein the amount of alcohol in the solvent is between 30 wt% and 70 wt%, preferably between 35 wt% and 65 wt%, more preferably between 40 wt% and 60 wt%, and / or wherein the mineral acid is hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or a mixture thereof, preferably wherein the mineral acid is sulfuric acid.

4. A method according to any of the preceding claims, wherein the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 7, preferably between 2 and 6, more preferably between 2.5 and 5.

5. A method according to any of the preceding claims, wherein while the temperature in the reactor is maintained between 110°C and 180°C the pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 bar and 12 bar, to allow at least a part of the lignocellulosic biomass to be dissolved to form the extract.

6. A method according to any of the preceding claims, wherein the amount of extract removed from the reactor is between 5 wt% and 50 wt% compared to the mass of solvent in the reactor, preferably the amount of extract removed from the reactor is between 10 wt% and 30 wt%.

7. A method according to any of the preceding claims, wherein the primary lignin is separated from the secondary solution by sedimentation, centrifugation and / or filtration.

8. A method according to any of the preceding claims, wherein the amount of water added to the removed extract is between 3 and 0.2 times the amount of the removed extract by volume, preferably wherein the amount of water added to the removed extract is between 2.6 and 0.4 times the amount of the removed extract by volume.

9. A method according to any of the preceding claims, wherein the method comprises:After removing the at least a part of the extract from the reactor, adding additional solvent to the reactor;After the addition of additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract; andRemoving at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved.

10. A method according to any of the preceding claims, wherein the method comprises:After removing the at least a part of the extract from the reactor, adding at least a part of the secondary solution and additional solvent to the reactor;After the addition of at least a part of the secondary solution and additional solvent, maintaining a temperature between 110°C and 180°C in the reactor, to allow at least another part of the lignin to be dissolved to form the extract; andRemoving at least another part of the extract from the reactor wherein the extract was formed by allowing the at least another part of the lignin to be dissolved.

11. A method according to claim 9 or 10, wherein while the temperature in the reactor is maintained between 110°C and 180°Cthe pressure in the reactor is maintained between 2 bar and 14 bar, preferably wherein the pressure in the reactor is maintained between 4 barand 12 bar, to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

12. A method according to claim 9, 10 or 11, wherein the amount of alcohol in the sum of at least a part of the secondary solution and the additional solvent added to the reactor is between 30 wt% and 70 wt%, preferably between 35 wt% and 65 wt%, more preferably between 40 wt% and 60 wt%.

13. A method according to any one of the preceding claims, wherein the temperature is maintained between 110°C and 180°C in the reactor for a duration of less than 120 minutes, preferably a duration of less than 110 minutes, more preferably for a duration of less than 100 minutes,wherein the duration is measured between the addition of solvent or the addition of at least a part of the second solution and additional solvent in the reactor and the removal of at least a part of the extract from the reactor.

14. A method according to any one of claims 9 to 13, wherein, after the addition of additional solvent, the mass ratio between the solvent compared to the dry weight of lignocellulosic biomass in the reactor is between 1 and 8, preferably between 2 and 7, more preferably between 3 and 6.

15. A method according to any one of the preceding claims, wherein the temperature is maintained between 120°C and 175°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract, preferably wherein the temperature is maintained between 120°C and 160°C in the reactor, to allow at least a part and / or to allow at least another part of the lignocellulosic biomass to be dissolved to form the extract.

16. A method according to any one of the preceding claims, wherein the method comprises the steps of:Evaporate the alcohol from the secondary solution to allow at least another part of the dissolved lignin to precipitate forming a secondary suspension comprising a secondary lignin and a third solution;Separate the secondary lignin from the third solution.

17. A method according to claim 15, wherein the secondary lignin is separated from the third solution by sedimentation and / or filtration.

18. An isolated lignin obtained by the method as a primary lignin according to any one of the preceding claims.

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