Method for extracting phenolic compounds from a lignocellulosic biomass

Abstract

The current invention relates to a method for extracting phenolic compounds from a lignocellulosic biomass, wherein said phenolic compounds are phenolic aldehydes, phenolic acids, and / or phenolic ketones, the method comprising the steps of: (i) mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies; and (ii) immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies, wherein said lignocellulosic biomass is derivable from one or more herbaceous crops, and wherein said dry base is a dry sodium or potassium base.

Description

[0001] METHOD FOR EXTRACTING PHENOLIC COMPOUNDS FROM A

[0002] LIGNOCELLULOSIC BIOMASS

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a method for extracting phenolic compounds from a lignocellulosic biomass. In another aspect, the present invention also relates to natural phenolic compounds.

[0005] BACKGROUND

[0006] In the field of chemical processing, the extraction of phenolic compounds from lignocellulosic biomass presents significant technical challenges. Existing methods are often characterized by high energy consumption, the use of hazardous chemicals, non-valorized waste streams and inefficiencies in selectively targeting and extracting the desired phenolic compounds.

[0007] EP2964600 discloses a method for the production of an oxidized reaction product, comprising the step of mechanocatalytically reacting an amount of a polymer containing material and an oxidation catalyst, the oxidation catalyst being a solid metal oxide comprising at least one of manganese oxides, cerium oxides, copper oxides, or silver oxides.

[0008] US2011180752 provides a process for direct liquification of cellulosic biomass. This document also discloses the need for transition metal oxides as catalysts, and temperatures of 150-400°C.

[0009] These known methods have multiple disadvantages or problems such as long reaction times, high reaction temperatures, the use of catalysts, and difficult dust control.

[0010] When phenolic compounds are extracted for food purposes, for example as flavors, traditional methods for extraction of phenolic compounds fall short in that they are not natural because they involve a feedstock contaminated by sulphite from paper pulping and chemical catalysts. Furthermore, for these extracts to be qualified as natural they have to fulfill certain process requirements, such as no higher temperature of 120°C under pressure. The aim of the invention is to provide an extraction method which eliminates those disadvantages.

[0011] SUMMARY OF THE INVENTION

[0012] The present invention and embodiments thereof serve to provide a solution to one or more of above-mentioned disadvantages. To this end, the present invention relates to a method for extracting phenolic compounds from lignocellulosic biomass according to claim 1. Preferred embodiments of the method are shown in any of the claims 2 to 15. In a second aspect, the present invention also relates to a use according to claim 16 and 17.

[0013] It has been found that by agglomerating lignocellulosic biomass with a dry base, the lignocellulosic biomass undergoes macroscopic modification under the pressure and heat of the agglomerated bodies, which results in improved availability and accessibility of the ligneous material in the extraction phase.

[0014] Furthermore, the method has the following advantages: agglomerating spontaneously cuts vanillin from the lignin polymer present in the lignocellulosic biomass; it is a convenient way to process the dusty lignocellulosic biomass; it makes a perfect suspension with the base; and it provides an intimate contact surface between the biomass and the dry base prior to the extraction phase.

[0015] By agglomerating the lignocellulosic biomass in a dry pretreatment step, the lignocellulosic biomass showed superior wettability and gave ideal release conditions for extraction.

[0016] The dry agglomeration ensures that the process temperature in the extraction phase can be reduced and work at a mild temperature (room temperature) with respect to other lignin-to-monomer extractive procedures.

[0017] The method according to the invention is advantageous because phenolic compounds can be extracted using physical (natural) extraction, without the use of catalysts or oxidative chemicals, resulting into natural products. Furthermore, a process is obtained wherein both product streams can be valorized. Phenolic compounds, such as vanillin, are obtained, as well as agglomerated body residues which can be used as soil improvement product. The invention provides for a less complex process for obtaining natural phenolic compounds, preferably phenolic aldehydes. The process has the object to minimize water consumption and operate within a closed-loop system by enhancing solvent recovery and reducing waste.

[0018] The process has the object to operate with low energy input and diminished alkaline usage (alkaline pressure boiling, for example, requires high amounts of alkali), factors that contribute to its cost-effectiveness and reduced environmental impact.

[0019] Additionally, the natural state of the extraction is maintained, eschewing the need for synthetic additives or harsh conditions. An advantageous product of this process is the resulting agglomerated body, enriched with for example potassium when a potassium salt is employed as the base, which finds a secondary use as a soil improver. This not only adds value to the leftover biomass but also aligns with sustainable practices by repurposing waste into beneficial agricultural inputs.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0022] As used herein, the following terms have the following meanings:

[0023] "Base" as used herein refers to a substance capable of accepting or neutralizing hydrogen ions. "Alkali" as used herein refers to a base that dissolves in water. Alkali refers to a basic, ionic salt of an alkali metal or an alkaline earth metal. "Potassium base" refers to a basic, ionic compound comprising potassium (K), such as potassium hydroxide, potassium carbonate and potassium oxide. "Sodium base" refers to a basic, ionic compound comprising sodium (Na), such as sodium hydroxide, sodium carbonate and sodium oxide.

[0024] "Dry" as used in herein refers to a substance which is in a solid state of matter or non-aqueous phase with a low moisture content such as a moisture content lower than 10 % by weight, preferably lower than 9 % by weight, preferably lower than 8 % by weight, preferably lower than 7 % by weight, preferably lower than 6 % by weight, preferably lower than 5 % by weight.

[0025] "Solid" as used herein refers to the solid state of matter, wherein the molecules in a solid are closely packed together and contain the least amount of kinetic energy.

[0026] "Agglomeration" as used in herein refers to the mechanical process of compressing primary solid particles or solid material under pressure to form larger multiparticle entities.

[0027] "Phenolic compounds" as used herein refers to both phenolic compounds such as hydroxy acetophenones (phenolic ketones), hydroxybenzoic acids (phenolic acids), and hydroxybenzaldehydes (phenolic aldehydes).

[0028] "Agglomerated body" as used herein refers to a multiparticle entity formed when primary solid particles or solid material are compressed under pressure and are made to adhere to form larger multiparticle entities, examples of agglomerated bodies are pellets, extrudates, granulates, granules, tablets, and the like.

[0029] "A", "an", and "the" as used herein refers to both singular and plural referents unless the context clearly dictates otherwise. By way of example, "a compartment" refers to one or more than one compartment.

[0030] "Comprise", "comprising", and "comprises" and "comprised of" as used herein are synonymous with "include", "including", "includes" or "contain", "containing", "contains" and are inclusive or open-ended terms that specifies the presence of what follows e.g. component and do not exclude or preclude the presence of additional, non-recited components, features, element, members, steps, known in the art or disclosed therein.

[0031] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order, unless specified. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that range, as well as the recited endpoints.

[0032] The expression "% by weight", "weight percent", "%wt" or "wt%", here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation.

[0033] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any >3, >4, >5, >6 or >7 etc. of said members, and up to all said members.

[0034] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, definitions for the terms used in the description are included to better appreciate the teaching of the present invention. The terms or definitions used herein are provided solely to aid in the understanding of the invention.

[0035] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0036] In a first aspect, the invention provides a method for extracting phenolic compounds from a lignocellulosic biomass. The phenolic compounds preferably are phenolic aldehydes, phenolic acids, and / or phenolic ketones. In one embodiment, the phenolic compounds may comprise at least one of vanillin, syringaldehyde, apocynin, vanillic acid, acetosyringenone and syringic acid. In an embodiment the phenolic compounds comprise vanillin, syringaldehyde, apocynin, vanillic acid, acetosyringenone, syringic acid, or a mixture thereof. In a preferred embodiment the phenolic compounds comprise vanillin, apocynin, vanillic acid, or a mixture thereof, most preferred vanillin.

[0037] In another or further embodiment, the phenolic compounds are vanillin, syringaldehyde, or a mixture or derivatives thereof. In another or further embodiment, the phenolic compounds are phenolic aldehydes, preferably chosen from vanillin, syringaldehyde, or a mixture thereof.

[0038] In a particularly preferred embodiment, the method comprises the steps of: i. mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies; and ii. immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies.

[0039] In a further embodiment, the dry base is a dry alkali, such as a dry alkali oxide, a dry alkali hydroxide, or a mixture thereof.

[0040] In another or further embodiment, the dry base is a dry potassium or sodium base, such as a dry potassium or sodium oxide, a dry potassium or sodium hydroxide, or a mixture thereof.

[0041] The inventors have unexpectedly observed that by agglomerating lignocellulosic biomass with a dry base, the lignocellulosic biomass undergoes macroscopic modification under the pressure and heat of the agglomerated bodies, which results in improved availability and accessibility of the ligneous material during subsequent extraction. It has been found that the agglomeration allows for simple subsequent extraction, resulting in phenolic compounds, preferably phenolic aldehydes, as desired product, but also residual agglomerated bodies enriched with alkali, such as potassium or sodium, which can serve as soil improvers.

[0042] In an embodiment, said immersing is carried out at a temperature between 15 and 25°C, and preferably at a pressure of 1 atm. The dry agglomeration ensures that the process temperature during the subsequent extraction can be reduced and be carried out at room temperature with respect to other lignin-to-monomer extractive procedures. No addition of oxidative chemicals is necessary.

[0043] In another embodiment, said immersing is carried out at elevated temperature, such as between 25 and 60°C, or between 25 and 50°C. A higher temperature could lead to faster extraction.

[0044] In an embodiment, said immersing is carried out for a duration between 1 and 48 hours, preferably between 5 and 48 hours.

[0045] It is preferential, in terms of process efficiency, to keep the immersion as short as possible. However, it was found that when immersion was done for 1 hour, the full yield was not achieved. It has been found that longer immersion / extraction times promote extraction efficiency. Advantageously it was found that despite the longer immersion period, the integrity of the agglomerated bodies was not affected. Even after being immersed in the alcohol for several days, the agglomerated bodies are still intact after filtration (such as decanting).

[0046] In an embodiment, the agglomerated bodies and the alcohol are stirred or shaken during said immersing step. Preferred is shaken, as it is advantageously less aggressive mixing.

[0047] Preferably said alcohol is chosen from: methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, or a mixture thereof. These low alcohols have been found to be able to extract the phenolic compounds, preferably phenolic aldehydes, from the agglomerated bodies.

[0048] In a preferred embodiment, the alcohol is ethanol. It was found that ethanol was especially advantageous, because it more selectively extracted the phenolic compounds than methanol, which also extracted other lignin fractions. Ethanol also showed higher extraction yields than isopropyl alcohol.

[0049] The alcohol is preferably at least 90% pure, preferably at least 91% pure, preferably at least 92% pure, preferably at least 93% pure, preferably at least 94% pure, preferably at least 95% pure, preferably at least 96% pure, or even 97% pure, preferably at least 98% pure, preferably at least 99% pure.

[0050] In a further embodiment, the method comprises further the step of: iii. separating the alcohol from the agglomerated bodies to obtain a liquid phase comprising said alcohol enriched in phenolic compounds and a solid phase comprising said agglomerated bodies with reduced content of phenolic compounds.

[0051] The separation can be carried out by decantation or filtration, decantation is preferred.

[0052] The liquid phase comprises said alcohol enriched in phenolic compounds. The alcohol in the liquid phase can be recovered in subsequent work-up of the liquid phase, wherein the crude phenolic compounds are obtained.

[0053] It has been found that the in the liquid (alcohol) phase, the phenolic compounds are present in their salt form (Na or K salt, depending on the base). It was unexpectedly found that only these phenolic components were selectively dissolved as salts in an alcohol phase. In cases a work-up of the liquid phase can be advantageous to release the free phenolic aldehydes.

[0054] To liberate phenolic aldehydes from their salt form in an alcoholic (preferably ethanolic) liquid phase, an acid treatment may be used. This process involves protonating the alkali salts of the phenolic compounds, preferably the phenolic aldehydes, releasing the free phenolic compounds, preferably the phenolic aldehydes.

[0055] The liquid phase can be characterized based on color and UV spectrum. With methanol, the color becomes amber to brown, with ethanol it goes from yellow to orange. On UV, a spectrum can be recorded with absorption from 400 nm, with a maximum at 280 nm attributed to phenol functions. The spectrum coincides with that of a generic lignin system. The presence of phenolic aldehydes (as salts) can be established by the presence of a clear absorption band at 350 nm.

[0056] The solid phase comprises said agglomerated bodies with reduced content of phenolic compounds. The solid phase can be subjected to evaporation to remove any residual alcohol. After evaporation agglomerated bodies enriched in alkali, such as potassium or sodium, are obtained, which can be used as soil improver.

[0057] The invention could be described as a method for optimizing a lignocellulosic biomass. Fibrous lignocellulosic biomass, such as flax, cannot be readily applied to soil because i / the stalks are poorly biodegradable due to the high lignin content and ii / the remaining fibers can clog the wheels, plows, and shovels of machinery. Current agricultural use includes open field burning of the stalks to yield char and ashes for fertilization. This treatment is a significant source of air pollution and gives rise to health concerns. It has now been found that agglomerating the fibrous cellulosic biomass with a dry base partially breaks the fibers and increases lignin bioavailability, which makes the agglomerated bodies suitable for use on land. Furthermore, the alkali enrichment, such as potassium, is advantageous as these are key for plant growth. Potassium, for example, regulates various physiological processes, including water uptake, enzyme activation, and photosynthesis. It helps in the development of strong roots and resistance to environmental stress, such as drought and disease.

[0058] The term "lignocellulosic biomass", as used in the text, refers to plant biomass containing cellulose, hemicelluloses, and lignin. Typically, in such a lignocellulosic biomass, the cellulose, hemicellulose, and lignin are bound together in a complex macromolecular structure along with small quantities of extractives, pectin, protein, and ash. A substantial benefit of the presently disclosed and / or claimed inventive concept(s) is that the lignin does not have to be separated away from the cellulose and / or hemicellulose prior to the pretreatment, nor the possible subsequent extraction, thereby eliminating a significant portion of the waste component from the process and eliminating the need to purify the lignocellulosic biomass before pretreatment of extraction. Any quantity of lignin-containing material may be provided and used in the presently disclosed and / or claimed inventive concept(s).

[0059] The nature or origin of the lignocellulosic biomass should not be considered to be constraining to the processes and methods disclosed herein, i.e., the lignocellulosic biomass is source and composition independent and one of ordinary skill in the art, given the present disclosure, would appreciate that the origin and composition of the lignocellulosic biomass could be tailored or blended in such a manner to provide any number of different phenolic compounds using the conditions disclosed herein. Indeed, the inventors have found to date that a wide variety of lignin-containing materials that have been tested are suitable and appropriate for the processes and methods disclosed herein.

[0060] During mechanochemical reaction in step (i), the dry base functions in the same phase as the lignocellulosic biomass and, pursuant to the presently disclosed concept(s), the dry base is in the solid phase as is the lignocellulosic biomass. In a preferred embodiment, the lignocellulosic biomass is derivable from one or more herbaceous crops. In an even more preferred embodiment, the lignocellulosic biomass is one or more herbaceous crops.

[0061] The terms "herbaceous crops" and "herbaceous plants", as used in the text, are synonyms and refer to vascular plants that have no persistent woody stems above ground. These can be perennial herbaceous plants, annual herbaceous plants, or biennial herbaceous plants.

[0062] In a further preferred embodiment, the herbaceous crop is chosen from the list of annual herbaceous crops, biennial herbaceous crops, or a mixture thereof. In an even more preferred embodiment, the herbaceous crop is chosen from the list of: Linum sp. (flaxes), Poaceae sp. (grasses), Cannabis sp (Hemp), or a mixture thereof.

[0063] Examples of grasses are: barley; maize; oats; rice; rye; sorghum; wheat; millet; bamboo; marram grass; meadow-grass; reeds; ryegrass; sugarcane; bahiagrass; bentgrass; bermudagrass; bluegrass; buffalograss; centipede grass; fescue ryegrass; st. Augustine grass; zoysia; calamagrostis spp.; cortaderia spp.; deschampsia spp.; festuca spp.; melica spp.; muhlenbergia spp.; stipa spp. Grasses also includes processed grasses or byproducts thereof such as straw, which is defined as the dry stalks of cereal plants after the grain and chaff have been removed.

[0064] Examples of flaxes are: Linum africanum; Linum alatum (winged flax); Linum album; Linum alpinum; Linum arboreum (tree flax); Linum arenicola (sand flax); Linum aristatum (bristle flax); Linum australe (southern flax); Linum austriacum (Asian flax); Linum berlandieri (Berlandier's yellow flax); Linum bienne (pale flax); Linum campanulatum; Linum cariense; Linum carteri (Carter's flax); Linum catharticum (fairy flax); Linum compactum (Wyoming flax); Linum cratericola (Galapagos Islands flax); Linum dolomiticum; Linum elongatum (Laredo flax); Linum flavum (golden flax); Linum floridanum (Florida yellow flax); Linum grandiflorum (scarlet flax, flowering flax); Linum hirsutum (downy flax); Linum hudsonioides (Texas flax); Linum imbricatum (tufted flax); Linum intercursum (sandplain flax); Linum kingii (King's flax); Linum leoni; Linum lewisii (Lewis' blue flax, Lewis flax); Linum usitatissimum; Linum lundellii (Sullivan City flax); Linum macrocarpum (Spring Hill flax); Linum marginale (Australian native flax); Linum medium (stiff yellow flax); Linum monogynum (New Zealand linen flax); Linum narbonense (blue flax); Linum neomexicanum (New Mexico yellow flax); Linum perenne (perennial blue flax); Linum pratense (meadow flax); Linum puberulum (plains flax); Linum pubescens; Linum rigidum (stiffstem flax); Linum rupestre (rock flax); Linum schiedeanum (Schiede's flax); Linum strictum (ridged yellow flax); Linum subteres (Sprucemont flax, slenderfoot flax); Linum suffruticosum; Linum sulcatum (grooved flax); Linum tenuifolium; Linum trigynum (French flax); Linum ucranicum; Linum usitatissimum (common cultivated flax); Linum vernal (Chihuahuan flax); Linum virginianum (woodland flax); Linum westii (West's flax).

[0065] Examples of cannabis sp. are: Cannabis sativa; Cannabis indica; Cannabis ruderalis Janisch.

[0066] In a particularly preferred embodiment, the lignocellulosic biomass is flax, straw, or a mixture thereof. The heterogeneous nature of flax shives and straw (such as wheat straw) severely complicates use in available reactor systems. Different length of stalks, dust formation, the tendency to clog pipes or transfer lines, and the poor wettability were often heard concerns. The invention provides a valuable valorization for these difficult to handle crops.

[0067] Although the lignocellulosic biomass and / or the dry base may have an inherent moisture content, either inherently at harvest or due to wetting of the biomass to control dust or heating, to aid compaction, to improve internal transport, storage or for any other processing reason, it should be understood that the reactants, either alone or in combination, are still to be considered in a solid or non-aqueous phase. It should be understood, however, that the existence of such an amount of humidity in the components should not be interpreted to mean that the agglomeration occurs in an aqueous phase: rather, while some minor amount of water may be present inherently or from said wetting measures, the mechanochemical reaction between the lignocellulosic biomass and the dry base is carried out in a non-aqueous (and solvent-free) phase and the lignocellulosic biomass and the dry base should be understood to be in a solid form.

[0068] In an embodiment, the lignocellulosic biomass has a moisture content of maximum 25 % by weight prior to step (i). Preferably, the moisture content is maximum 20 % by weight prior step (i), more preferably maximum 15 % by weight prior to step (i).

[0069] Too much moisture causes a paste to form and clogs the die. In an embodiment, it may be needed to dry certain types of lignocellulosic biomasses, for example in rotary drum dryers, to reduce the moisture content. In another embodiment, it may be needed to add wetting agents to control dust or heating, to aid compaction, to improve internal transport, storage or for any other processing reason. Wetting agents, such as water, may be added in an amount of up to 20% by weight of the total of lignocellulosic biomass. Preferably wetting agents are added in an amount of up to 15% by weight, and more preferably in an amount of up to 10% by weight.

[0070] In such embodiments, the resulting wetted lignocellulosic biomass can have a moisture content of between 10 and 30% by weight prior to the step of agglomeration, preferably the resulting wetted lignocellulosic biomass can have a moisture content of between 15 and 30% by weight prior to the step of agglomeration, or even between 20 and 25% by weight prior to the step of agglomeration.

[0071] The terms "moisture content" and "water content", as used in the text, are synonyms and refer to the quantity of water contained in the lignocellulosic biomass or in the dry base expressed in % by weight of the total component at ambient temperature and ambient pressure. The moisture content can be measured by techniques known in the art, such as oven-dry method and moisture meter method.

[0072] The ratio of the lignocellulosic biomass to the dry base is in step (i) such that the depolymerization of the lignin and the release of the phenolics aldehyde is optimized. Generally, the efficiency is optimized by determining a ratio, wherein a surface interaction of lignocellulosic biomass and the dry base is maximized and the release of specified or targeted phenolic compounds is optimized. In one embodiment, but not by way of limitation, said lignocellulosic biomass is agglomerated with said dry base in a ratio by weight between 5 / 0,1 and 5 / 5, preferably in a ratio by weight between 5 / 0,25 and 5 / 4,5, more preferably in a ratio by weight between 5 / 0,5 and 5 / 4, even more preferably in a ratio by weight between 5 / 0,75 and 5 / 3,5, even more preferably in a ratio by weight between 5 / 1 and 5 / 3.

[0073] The inventors unexpectedly observed that adding said dry base to the lignocellulosic biomass and simultaneous agglomeration results in softer agglomerated bodies, which dissolve easier during extraction in step (ii). Furthermore, addition of said dry base raises the surface temperature of the agglomerated bodies, which is needed to release the phenolic compounds from said lignocellulosic biomass. The inventors observed that if too little of said dry base is added to said lignocellulosic biomass, the surface temperature of the agglomerated bodies is not raised enough.

[0074] The inventors observed that if too much of said dry base is added to said lignocellulosic biomass, the obtained agglomerated bodies will be too soft and will crumble. Furthermore, too much of said dry base can lead to high surface temperatures which can cause charring. Furthermore, at higher base amounts than 5 / 3 (such as 5 / 4 and 5 / 5), the process becomes economically unviable, for the cost of base dominates the process.

[0075] In another or further embodiment, said lignocellulosic biomass is agglomerated with said dry base in a ratio by weight between 50 / 1 and 1 / 1, preferably in a ratio by weight between 40 / 1 and 1 / 1, more preferably in a ratio by weight between 30 / 1 and 1 / 1, even more preferably in a ratio by weight between 20 / 1 and 1 / 1, even more preferably in a ratio by weight between 10 / 1 and 1 / 1, even more preferably in a ratio by weight between 5 / 1 and 1 / 1,

[0076] In a preferred embodiment, the surface temperature of said agglomerated bodies is higher than 70°C, preferably higher than 75°C, more preferably higher than 80°C, even more preferably higher than 85°C, even more preferably higher than 90°C, even more preferably higher than 95°C, even more preferably higher than 100°C, even more preferably higher than 105°C, even more preferably higher than 110°C. A minimum surface temperature is needed for the phenolic compounds to be released from the lignocellulosic biomass in the agglomerated bodies.

[0077] In another or further embodiment, the surface temperature of said agglomerated bodies is lower than 180°C, preferably lower than 175°C, more preferably lower than 170°C, even more preferably lower than 165°C, even more preferably lower than

[0078] 160°C, even more preferably lower than 155°C, even more preferably lower than

[0079] 150°C, even more preferably lower than 145°C, even more preferably lower than

[0080] 140°C. It was found that surface temperatures that were too high resulted in charring of the agglomerated bodies and gave rise to significant delignification and decomposition.

[0081] In another or further embodiment, the surface temperature of said agglomerated bodies is between 70 and 180°C, preferably between 75 and 175°C, more preferably between 80 and 170°C, even more preferably between 85 and 165°C, even more preferably between 90 and 160°C, even more preferably between 95 and 155°C, even more preferably between 100 and 150°C, even more preferably between 105 and 145°C, even more preferably between 110 and 140°C.

[0082] The heat and pressure that the agglomeration generates, plasticizes the lignin content and leads to improved contact between the base which promotes the digestion, solubility, and extraction of the agglomerated bodies in step (ii).

[0083] In an embodiment, the agglomerated body as a pH above or equal to 12. The alkaline environment is believed to improve the release of phenolic compounds from the lignocellulosic biomass.

[0084] In an embodiment, said dry base is a dry alkali. In an embodiment, said dry base is a dry inorganic oxide, dry inorganic hydroxide, or a mixture thereof

[0085] In a preferred embodiment said dry base is chosen from the list of: dry sodium hydroxide (NaOH), dry potassium hydroxide (KOH), dry calcium hydroxide (Ca(OH)2), dry calcium oxide (CaO), dry magnesium hydroxide (Mg(OH)2), dry magnesium oxide (MgO), or a mixture thereof, preferably dry NaOH, dry KOH, or a mixture thereof, more preferably KOH.

[0086] Alternatively, an inorganic carbonate can be used for agglomeration with the lignocellulosic biomass, such as dry sodium carbonate (Na2COs), or potassium carbonate (K2COs).

[0087] The dry base is in a solid phase, such as a powder, pellets, flakes, granules, granulates, extrudates, and the like. Preferably the dry base is in the form of pellets or granulates.

[0088] In a preferred embodiment, said lignocellulosic biomass and said dry base are agglomerated in step (i) by compressing them through a die.

[0089] The inventors found that agglomerating the lignocellulosic biomass with dry base generates pressure by increasing friction in the die.

[0090] In a first particularly preferred embodiment, said lignocellulosic biomass and said dry base are pelletized during agglomerating in step (i). The term "pelletizing", as used herein, is the process of compressing or molding a material into the shape of a pellet. In a further embodiment, the resulting agglomerated bodies are rounded, spherical, or cylindrical pellets.

[0091] In a further embodiment, the pelletizing is carried out by compressing the lignocellulosic biomass and the dry base through a die. The die can be a flat die or a ring die.

[0092] Flat dies are preferred because they are smaller in size and lightweight, easier to maintain and clean due to ready disassembly.

[0093] Ring dies are preferred because they have a high capacity, less wear and higher durability, and lower energy consumption.

[0094] In a further embodiment, the step of pelleting is repeated at least once, preferably at least twice. The inventors have found that sequential pelleting steps increase the surface temperature and contact pressure of the pellet which results in higher amounts of plasticized lignin, more energy in the biomass pellet, and leads to improved contact between the lignocellulosic biomass and the dry base which promotes further the digestion, oxidation, and solubility of lignocellulosic biomass.

[0095] In a further embodiment, the pellet dies have hole diameters of between 1 and 20 mm, preferably of between 2 and 15 mm, even more preferably of between 3 and 12 mm. In another or an even further embodiment, the pellet dies have a stroke length of between 5 and 100 mm, preferably of between 10 and 80 mm. In another or an even further embodiment, the ratio of the stroke length to the hole diameter is at least 0.5, preferably at least 0.8, more preferably at least 1. In another or an even further embodiment, the ratio of the stroke length to the hole diameter is at most 100, preferably at most 50, more preferably at most 30. In another or an even further embodiment, the ratio of the stroke length to the hole diameter lies between 0.5 and 100, preferably between 0.8 and 50, more preferably between 1 and 30. The inventors have found that the relation of hole diameter to stroke length of the die holes is inversely proportional to the energy content of the lignocellulosic biomass, and that a high ratio of stroke length to hole diameter significantly increases the digestion, oxidation, and solubility of lignocellulosic biomass.

[0096] In a second particularly preferred embodiment, said lignocellulosic biomass and said dry base are extruded during agglomeration in step (i). In this embodiment, said lignocellulosic biomass and said dry base may be grinded and mixed prior to extrusion, combined with subsequent extrusion of the mixed product, or said lignocellulosic biomass and said dry base may be co-extruded.

[0097] The terms "extrusion" and "extrude", as used in the text, refer to the process of pushing one or more materials through a single die of the desired cross-section to create objects of a fixed cross-sectional profile.

[0098] The terms "co-extrusion" and "co-extrude", as used in the text, refer to the process of pushing two or more materials through a single die of the desired cross-section to create objects of a fixed cross-sectional profile.

[0099] Extrusion has the advantage that higher shear forces can be reached. Extrusion also allows for longer and smaller agglomerated bodies that can be obtained. Furthermore, extrusion allows for more pressure and temperature control.

[0100] In an embodiment, the lignocellulosic biomass can be processed or cleaned prior to agglomeration in step (i) to eliminate contaminants such as stones, for example with a destoner, and metal particles, for example by magnetic clearing. It can be important depending on the material's origin, as to prevent mechanical failure of the agglomeration equipment.

[0101] In some embodiments, the lignocellulosic biomass is milled prior to the agglomeration steps, for example to reduce the size of the lignocellulosic biomass.

[0102] In a preferred embodiment, the agglomerated bodies formed during agglomeration comprises between 0.01 and 10% by weight of total amount of phenolic compounds, preferably between 0.025 and 7.5% by weight of total amount of phenolic compounds, more preferably between 0.05 and 5% by weight of total amount of phenolic compounds.

[0103] In a particularly preferred embodiment, the method comprises the steps of: i. mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies; and ii. immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies, wherein said lignocellulosic biomass is derivable from one or more herbaceous crops, and wherein the phenolic compounds comprise at least one of vanillin, apocynin, vanillic acid, syringaldehyde, acetosyringone, syringic acid, or a mixture thereof.

[0104] In another or further particularly preferred embodiment, the method comprises the steps of: i. mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies; and ii. immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies, wherein said lignocellulosic biomass is flax, straw, or a combination thereof, preferably flax.

[0105] In a most preferred embodiment, the method comprises the steps of: i. mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies, wherein said dry base is potassium hydroxide or potassium oxide; and ii. immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies, wherein said lignocellulosic biomass is flax, and wherein the phenolic compounds comprise at least vanillin.

[0106] In an aspect, the invention relates to phenolic compounds which are extracted non- catalytically. The phenolic compounds are preferably extracted according to the method according to the first aspect of the invention. In another aspect, the invention relates to a composition comprising an alcohol and phenolic compounds, preferably in an amount of between

[0107] In another aspect the invention relates to agglomerated bodies comprising lignocellulosic biomass, preferably flax, and an alkali, preferably potassium.

[0108] The agglomerated bodies with reduced content of phenolic compounds, comprise preferably between 5 and 30 wt.% of potassium, more preferred between 10 and 30 wt.%. The invention could be described as a method for optimizing a lignocellulosic biomass. Fibrous lignocellulosic biomass, such as flax, cannot be readily applied to soil because i / the stalks are poorly biodegradable due to the high lignin content and ii / the remaining the fibers can clog the wheels, plows, and shovels of machinery. Current agricultural use includes open field burning of the stalks to yield char and ashes for fertilization. This treatment is a significant source of air pollution and gives rise to health concerns. It has now been found that agglomerating the fibrous cellulosic biomass with a dry base partially breaks the fibers and increases lignin bioavailability, which makes the agglomerated bodies suitable for use on land. Furthermore, the alkali enrichment, such as potassium, is advantageous as these are key for plant growth. Potassium, for example, regulates various physiological processes, including water uptake, enzyme activation, and photosynthesis. It helps in the development of strong roots and resistance to environmental stress, such as drought and disease.

[0109] The present invention will be now described in more details, referring to examples that are not limitative.

[0110] EXAM PLES

[0111] Comparative example 1

[0112] Flax shives (500 g) with a moisture content of 15% by weight are transferred to the inlet of a flat die pelletizing machine, equipped with 2 mechanical rollers. The metal die plate contains holes of 6 mm diameter and die thickness is 3 cm. A cutting blade installed under the die plate cuts pellets of at a length of between 1 and 2 cm. The pellets obtained are green and have a temperature of between 50-70°C when leaving the pelletizer. Upon storage, the pellets stay intact, without color change.

[0113] Example 2

[0114] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 300 g of sodium hydroxide pellets, to obtain an even distribution of sodium hydroxide pellets. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 1. The pellets obtained are rust brown and have a distinct smell reminiscent of amine compounds. The surface temperature of the pellets is between 135 °C and 150 °C when leaving the pelletizer. Example 3

[0115] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 300 g of potassium hydroxide flakes, to obtain an even distribution of potassium hydroxide flakes. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 1. The pellets obtained are rust brown and have a distinct smell reminiscent of amine compounds. The surface temperature of the pellets is between 140 °C and 160 °C when leaving the pelletizer.

[0116] Example 4

[0117] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 300 g of potassium hydroxide flakes, to obtain an even distribution of potassium hydroxide flakes. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 1. The pellets obtained are rust brown and have a distinct smell reminiscent of amine compounds. The surface temperature of the pellets is between 135 °C and 150 °C when leaving the pelletizer. The pellets are cooled open to the atmosphere until temperature is below 90°C and are fed to the inlet of the flat die pelletizing machine for a second pelletizing step. The surface temperature of the pellets is between 125 °C and 135 °C when leaving the pelletizer.

[0118] Example 5

[0119] The pellets from Example 4 are cooled open to the atmosphere until temperature is below 90°C and are fed to the inlet of the flat die pelletizing machine for a third pelletizing step. The surface temperature of the pellets is between 115 °C and 125 °C when leaving the pelletizer. The pellets obtained are rust to dark brown and have a distinct smell reminiscent of amine compounds.

[0120] Example 6

[0121] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 200 g of sodium hydroxide pellets, to obtain an even distribution of sodium hydroxide pellets. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 1. The pellets obtained are rust brown and have a distinct smell reminiscent of amine compounds. The surface temperature of the pellets is between 140 °C and 150 °C when leaving the pelletizer. Example 7

[0122] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 300 g of potassium hydroxide flakes, to obtain an even distribution of potassium hydroxide flakes. The mixture is left to rest for 90 minutes. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 1. The pellets obtained are rust brown and have a distinct smell reminiscent of amine compounds. The surface temperature of the pellets is between 90 °C and 110 °C when leaving the pelletizer.

[0123] Example 8

[0124] Flax shives (500 g) with a moisture content of 15% by weight are homogenized with 300 g of potassium hydroxide flakes, to obtain an even distribution of potassium hydroxide flakes. This mixture is transferred to the inlet of a flat die pelletizing machine. The metal die plate contains holes of 4 mm diameter and die thickness is 4 cm. A cutting blade installed under the die plate cuts pellets of at a length of between 1 and 2 cm. The pellets obtained are dark brown and have a temperature of 150°C and higher when leaving the pelletizer. The pellets obtained are dark brown to black and some smoke formation is observed.

[0125] Example 9

[0126] Flax shives (500 g) with a moisture content of 15% by weight are mixed with 50 g water and left to rest for 90 minutes. Just before pelletizing, the wetted flax is homogenized with 300 g of potassium hydroxide flakes, to obtain an even distribution of potassium hydroxide flakes. This mixture is transferred to the inlet of a flat die pelletizing machine and pellets are produced in the manner as described for comparative example 8. The pellets obtained are rust to dark brown and have a temperature between 125°C and 140°C when leaving the pelletizer. The pellets obtained are dark brown to black and some smoke formation is observed.

[0127] Example 10

[0128] The obtained pellets from example 9 (60 g) were immersed in ethanol for 12 hours. After sufficient contact time, the mixture is decanted to separate the liquid phase containing the extracted phenolic compounds from the solid biomass. The alcohol solution is bright yellow. The alcohol is then recovered by distillation, leaving behind the phenolic-rich extract as an orange-brown resinous, oily substance. The remaining phase is subjected to neutralization by diluted aqueous sulfuric acid to pH 6 to release free phenolic compounds, which can be worked up via liquid-liquid extraction with ethyl acetate, followed by evaporation and drying. Example 11

[0129] The obtained pellets from example 9 (60 g) were immersed in methanol for 12 hours. After sufficient contact time, the mixture is decanted to separate the liquid phase containing the extracted phenolic compounds from the solid biomass. The alcohol solution is amber to brown-coloured. The alcohol is then recovered by distillation, leaving behind the phenolic-rich extract as a brown oily substance. The remaining phase is subjected to neutralization by diluted aqueous sulfuric acid to release free phenolic compounds, which can be worked up via liquid-liquid extraction with ethyl acetate, followed by evaporation and drying.

[0130] Example 12

[0131] The obtained pellets from example 9 (60 g) were immersed in isopropyl alcohol for 12 hours. After sufficient contact time, the mixture is decanted to separate the liquid phase containing the extracted phenolic compounds from the solid biomass. The alcohol solution is light yellow-coloured. The alcohol is then recovered by distillation, leaving behind the phenolic-rich extract as an orange resin. The remaining phase is subjected to neutralization by diluted aqueous sulfuric acid to release free phenolic compounds, which can be worked up via liquid-liquid extraction with ethyl acetate, followed by evaporation and drying.

[0132] All three alcohols were effective in extracting vanillin. When methanol was used, a higher extract mass is obtained with lower purity due to methanol also extracting other lignan fractions. Ethanol extraction gave a higher yield than isopropyl alcohol. Detailed analysis via HPLC with UV detection demonstrated that ethanol extract was selective to phenolic aldehyde extraction, with vanillin as major compound in the extract. Methanol was equally effective in extracting phenolic aldehydes as ethanol, but a lower selectivity was obtained due to co-extraction of lignans or lignin oligomeric fractions. Isopropyl alcohol was equally selective in extracting phenolic aldehydes as ethanol, but a lower effectivity was obtained.

[0133] The pellets recovered after decantation were dried till constant mass. Pellets after alcohol extraction had lower mass than before extraction. Mass losses were higher when methanol was the extraction solvent than when ethanol was the extraction solvent. Mass losses were higher when ethanol was the extraction solvent than when isopropyl alcohol was the extraction solvent. For all extraction solvents, the pellets collected after decantation remained structurally intact and were lighter in colour than before extraction. Submersion of these pellets in water produced gradual swelling of the pellets with slow disintegration of pellet structure. The aqueous phase became brown-coloured. The pH of the aqueous phase was > 10.

[0134] Example 13

[0135] The alcoholic extract obtained after extraction of a 5 / 3 flax / KOH pellet is analyzed via UV Vis spectrophotometry and via reversed phase HPLC. For the UV Vis spectrophotometry, the extract is diluted in demineralized water. The absorption at 350 nm indicates the presence of phenolic aldehydes, present as potassium salt. The spectrum is given in figure 1.

[0136] For HPLC analysis, an aliquot of the alcoholic extract is neutralized by an equal volume of a 2M aqueous hydrochloric acid solution. This mixture is further diluted in a 1 : 1 solution of 0.1% aqueous formic acid and acetonitrile. The analysis is performed on a standard HPLC chromatograph (Shimadzu Nexera XR) using a gradient elution method and with a 3 pm C18 column (Shim-pack GISS-HP, 3.0 x 100 mm). A gradient protocol was applied with a flow rate of 1 ml / min, starting at 90% aqueous phase (0.1% formic acid) and 10% organic phase (acetonitrile) for 2 min, increasing to 90% organic phase in 5 min, and remaining for 3 min. Detection was done via UV analysis (310 nm).

[0137] The chromatogram given in figure 2 obtained after extraction with ethanol and after extraction with methanol shows vanillin as the major compound in the chromatogram. The chromatogram shows that after extraction with ethanol the vanillin compound is more pure compared to the chromatogram after extraction with methanol. The extraction with ethanol is more selective towards phenolic aldehydes like vanillin.

[0138] Analysis (figure 3) of the chromatogram obtained after extraction with ethanol, methanol and isopropyl alcohol shows that after extraction with methanol for 1 hour, more vanillin compound is present compared to extraction with ethanol. The extraction with isopropyl alcohol is less efficient towards phenolic aldehydes like vanillin when compared to ethanol and methanol. The chromatograms also show that after extraction with acetone, almost no vanillin compound is extracted.

[0139] Analysis (figure 4) of the chromatogram obtained after extraction with ethanol and methanol shows that after extraction with methanol for 1 hour, less vanillin compound is present compared to extraction with methanol for 25 hours. The chromatograms show also that after extraction with ethanol for 1 hour, less vanillin compound is present compared to extraction with ethanol for 25 hours.

Claims

CLAIMS1. A method for extracting phenolic compounds from a lignocellulosic biomass, wherein said phenolic compounds are phenolic aldehydes, phenolic acids, and / or phenolic ketones, the method comprising the steps of: i. mechanochemically reacting said lignocellulosic biomass with a dry base, thereby agglomerating said lignocellulosic biomass with said dry base under pressure to form agglomerated bodies; and ii. immersing said agglomerated bodies in an alcohol for a period of time sufficient to extract phenolic compounds from said agglomerated bodies, wherein said lignocellulosic biomass is derivable from one or more herbaceous crops, and wherein said dry base is a dry sodium or potassium base.

2. Method according to claim 1, wherein said dry sodium or potassium base is a dry potassium or sodium oxide, a dry potassium or sodium hydroxide, or mixture thereof.

3. Method according to claim 1 or 2, wherein said dry sodium or potassium base is dry potassium hydroxide (KOH) or dry potassium oxide (K2O).

4. Method according to any of the previous claims, wherein said immersing is carried out at a temperature between 15 and 25°C, and preferably at a pressure of 1 atm.

5. Method according to any of the previous claims, wherein said alcohol is chosen from: methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, or a mixture thereof.

6. Method according to any of the previous claims, wherein said alcohol is ethanol.

7. Method according to any of the previous claims, wherein the method comprises further the step of: iii. separating the alcohol from the agglomerated bodies to obtain a liquid phase comprising said alcohol enriched in phenolic compounds and a solid phase comprising said agglomerated bodies with reduced content of phenolic compounds.

8. Method according to claim 7, wherein said separation is a decantation or filtration.

9. Method according to any of the previous claims, wherein said immersing is carried out for a duration between 5 and 48 hours.

10. Method according to any of the previous claims, wherein said phenolic compounds are at least one of vanillin, syringaldehyde, apocynin, vanillic acid, acetosyringenone and syringic acid.

11. Method according to any of the previous claims, wherein said phenolic compounds are vanillin, syringaldehyde, or a mixture thereof.

12. Method according to any of the previous claims, wherein said lignocellulosic biomass is flax.

13. Method according to any of the previous claims, wherein said lignocellulosic biomass is reacted mechanochemically with said dry base in a ratio by weight between 5 / 3 and 5 / 1.

14. Method according to any of the previous claims, wherein the surface temperature of said agglomerated bodies is higher than 90°C.

15. Method according to any of the previous claims, wherein during agglomerating said lignocellulosic biomass and said dry base are pelletized into rounded, spherical, or cylindrical pellets.

16. Method according to any of the previous claims 1-14, wherein during agglomerating said lignocellulosic biomass and said dry base are co-extruded.

17. Method according to any of the previous claims, wherein step (i) is repeated at least once, preferably twice.

18. Use of agglomerated bodies with reduced content of phenolic compounds in soil improvement products, wherein said agglomerated bodies comprise lignocellulosic biomass and an alkali.

19. Use according to claim 18, wherein the lignocellulosic biomass is flax, and wherein the alkali is potassium.

Images