Method for producing hydrothermally treated furfural and lignocellulosic biomass

Abstract

This invention provides a method for producing furfural from hemicellulose in lignocellulosic biomass, and further for producing a hydrothermal treatment product of lignocellulosic biomass that can be used as a raw material for power generation. [Solution] The present invention provides a method for producing furfural from hemicellulose in lignocellulosic biomass and a hydrothermally treated lignocellulosic biomass, comprising the step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C.

Description

Technical Field

[0001] The present invention relates to a method for producing furfural and a hydrothermal treatment product of lignocellulosic biomass. Preferably, the present invention relates to a method for producing furfural from hemicellulose in lignocellulosic biomass and a method for producing a hydrothermal treatment product of lignocellulosic biomass from lignocellulosic biomass.

Background Art

[0002] Furfural is a useful compound used as a raw material for furan resins, a raw material for tetrahydrofuran known as a reaction solvent, a resin solvent, and an adhesive. Furfural is not usually produced from petrochemical raw materials but is produced from plant-derived saccharides as raw materials.

[0003] Patent Document 1 discloses a method for producing furfural from a biomass raw material containing a cellulose component and a hemicellulose component, which comprises a first step of hydrolyzing the hemicellulose component in the biomass raw material with an aqueous acid solution and separating the solution containing the decomposition components from the solid content by solid-liquid separation, and a second step of subjecting the separated solution to pressurized heating to produce furfural. Here, when producing furfural, it is preferable to dry and pulverize the biomass raw material into powder. In the examples, it is disclosed that the corn cob was dried, pulverized, and sieved through an 80-mesh sieve to obtain a powder.

[0004] On the other hand, it is known that lignocellulosic biomass can be used as a power generation raw material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] However, as described in Patent Document 1, furfural is usually produced by crushing lignocellulosic biomass, and the use of the residue is not envisioned.

[0007] The present inventors have now discovered that when producing furfural from hemicellulose in lignocellulosic biomass, including a step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C, it is possible to produce a hydrothermally treated lignocellulosic biomass product that can be used as a raw material for power generation, along with furfural. The present invention is based on this finding.

[0008] Therefore, the present invention aims to produce furfural from hemicellulose in lignocellulosic biomass, and further to produce hydrothermally treated lignocellulosic biomass that can be used as a raw material for power generation.

[0009] The present invention encompasses the following [1] to

[11] . [1] A method for producing furfural from hemicellulose in lignocellulosic biomass and a hydrothermally treated lignocellulosic biomass from lignocellulosic biomass, comprising the step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C. [2] A method for producing a hydrothermal product of furfural and lignocellulosic biomass according to [1], wherein the mixture does not contain a solid catalyst. [3] A method for producing a hydrothermally treated product of furfural and lignocellulosic biomass according to [1] or [2], wherein the mixture further comprises a solvent that is incompatible with water. [4] The method for producing a hydrothermal product of furfural and lignocellulosic biomass according to [3], wherein the water-incompatible solvent is at least one water-incompatible solvent selected from the group consisting of toluene, cyclopentyl methyl ether, 4-methyltetrahydropyran, hexane, and xylene. [5] A method for producing hydrothermally treated furfural and lignocellulosic biomass according to any one of [1] to [4], wherein the hydrothermal treatment is carried out under pressure of 0.1 to 4 MPa. [6] A method for producing furfural and hydrothermally treated lignocellulosic biomass according to any one of [1] to [5], wherein the content of solids with a longest part length of 2 mm or more is 50% by mass or more of the total amount of the hydrothermally treated lignocellulosic biomass. [7] A method for producing furfural and hydrothermally treated lignocellulosic biomass according to any one of [1] to [6], further comprising the step of removing powder with a longest part length of less than 2 mm from hydrothermally treated lignocellulosic biomass to obtain solid material of hydrothermally treated lignocellulosic biomass. [8] The method for producing furfural and hydrothermally treated lignocellulosic biomass according to [6] or [7], wherein the amount of heat generated per unit weight of the solids in the hydrothermally treated lignocellulosic biomass is greater than the amount of heat generated in the lignocellulosic biomass before hydrotherm treatment. [9] A method for producing furfural and hydrothermally treated lignocellulosic biomass according to any one of [6] to [8], wherein the sodium content of the solids of the hydrothermally treated lignocellulosic biomass is reduced compared to the sodium content of the lignocellulosic biomass before hydrotherm treatment.

[10] A method for producing furfural and hydrothermally treated lignocellulosic biomass according to any one of [6] to [9], wherein the potassium content of the solids of the hydrothermally treated lignocellulosic biomass is lower than the potassium content of the lignocellulosic biomass before hydrotherm treatment.

[11] A method for producing furfural and hydrothermally treated lignocellulosic biomass according to any one of [6] to

[10] , wherein the chlorine content of the solids of the hydrothermally treated lignocellulosic biomass is reduced compared to the chlorine content of the lignocellulosic biomass before hydrotherm treatment.

[0010] According to the present invention, when producing furfural from hemicellulose in lignocellulosic biomass, the process includes a step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C. This allows for the production of a hydrothermally treated lignocellulosic biomass product that can be used as a power generation fuel along with furfural. Furthermore, the present invention is advantageous in that the resulting hydrothermally treated lignocellulosic biomass product is easy to handle when used as a power generation fuel. Moreover, the present invention is advantageous in that it can improve the amount of furfural produced when producing furfural from hemicellulose in lignocellulosic biomass. Specific description of the invention

[0011] The present invention provides a method for producing furfural from hemicellulose in lignocellulosic biomass and for producing a hydrothermally treated product of lignocellulosic biomass, characterized in that it includes a step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C.

[0012] <Method for producing hydrothermally treated furfural and lignocellulosic biomass products> The present invention provides a method for producing furfural and hydrothermally treated lignocellulosic biomass products, which includes a step of hydrothermal treatment. Depending on the circumstances, the method may also include a biomass preparation step, a solid-liquid separation step, a purification step, and a step of obtaining solid material from the hydrothermally treated lignocellulosic biomass. Each step will be described below.

[0013] In this specification, "furfural" refers to an aromatic aldehyde having a furan ring, represented by the molecular formula C5H4O2, also known as furfural aldehyde. Furfural can be obtained by dehydrating pentoses, which are obtained by hydrolyzing hemicellulose. Typically, it is obtained by the dehydration reaction of xylose, which is obtained by hydrolyzing xylan in hemicellulose.

[0014] (hydrothermal treatment process) The "hydrothermal treatment process" is a process in which a mixture containing lignocellulosic biomass and water is subjected to hydrothermal treatment.

[0015] Lignocellulose is a substance that makes up the cell walls of plants, and its main components are cellulose, hemicellulose, and lignin. It is especially abundant in the woody parts of woody plants.

[0016] "Cellulose" has the molecular formula (C6H 10 O5) n It is a polysaccharide represented by , a compound in which β-glucose is polymerized in a linear chain by glycosidic bonds, and is present in lignocellulose as the main component of plant cell walls and plant fibers, making up about 40-50%.

[0017] "Hemicellulose" is a general term for insoluble polysaccharides other than cellulose. Examples include xylan, mannan, glucuronoxylan, and glucomannan. In the method for producing furfural according to the present invention, hemicellulose, and in particular xylan, serves as the direct raw material for furfural. The proportion of hemicellulose in lignocellulose varies depending on the plant from which it is derived, but is usually about 15-35%, and in the case of PKS (Palm Kernel Shell), it is about 25%.

[0018] Lignin is a high-molecular-weight phenol that, in lignocellulose, acts as an adhesive, attaching to and solidifying cellulose and hemicellulose. The proportion of lignin in lignocellulose, like that of hemicellulose, varies depending on the plant and part of the plant from which it originates, but is usually around 15-35%, and in the case of PKS, it is about 50%. In parts such as leaves that have not yet undergone lignification, the amount is usually even lower.

[0019] In this specification, "lignocellulosic biomass" refers to organic resources that contain lignocellulose as a main component, preferably containing 90% or more by mass of lignocellulose in a dry state. Examples of lignocellulosic biomass include woody biomass, woody waste, herbaceous biomass, and herbaceous waste. Specifically, examples include forest residues, thinned wood, unused trees, short-cycle cultivated wood, sawmill residues, pruned wood from street trees and parks, construction waste, seed husks, grain hulls, leaves, stems, and cores.

[0020] The type of lignocellulosic biomass used in this invention is not particularly limited, and any lignocellulosic biomass, including the examples above, may be used. Preferably, it is woody waste and herbaceous waste, which are discharged in large quantities as industrial waste. If it is woody waste, for example, it may be seed husks, forest residues, thinned wood, sawmill residues, construction waste, agricultural residues, or any combination thereof. The woody waste may be palm kernel shells, woody waste derived from hardwoods, or woody waste derived from conifers, but from the viewpoint of being used as a raw material for power generation, having a low moisture content and a high calorific value, palm kernel shells and woody waste derived from conifers are preferred. The type of conifer is not particularly limited, but examples include species belonging to the genus Cryptomeria, species belonging to the genus Chamaecyparis, and species belonging to the genus Pine. Specific examples of species belonging to the genus Cryptomeria include Japanese cedar (Cryptomeria japonica), and examples of species belonging to the genus Chamaecyparis include Japanese cypress (Chamaecyparis obtusa).

[0021] According to one embodiment of the present invention, a hydrothermal treatment is performed on a mixture containing the lignocellulosic biomass as a raw material and water. The mixture may contain components other than the lignocellulosic biomass and water. Such a component is preferably a solvent immiscible with water. The ratio of the lignocellulosic biomass to the total of water and the water-immiscible solvent in the mixture (lignocellulosic biomass / total of water and water-immiscible solvent) is not particularly limited, and examples thereof include 0.1 to 10 (mass / volume)%, preferably 0.5 to 5 (mass / volume)%, more preferably 1 to 3 (mass / volume)%. When the mixture does not contain components other than the lignocellulosic biomass and water, the total of water and the water-immiscible solvent described above refers to the amount of only water.

[0022] The above water-immiscible solvent is not particularly limited as long as it does not prevent the effects of the present invention. Here, a solvent immiscible with water is a solvent that separates into two phases when an equal volume of water and the solvent are mixed. Examples of the water-immiscible solvent include organic solvents such as toluene, cyclopentyl methyl ether, 4-methyltetrahydropyran, hexane, and xylene, and preferably toluene and cyclopentyl methyl ether. The ratio (volume ratio) of water to the water-immiscible solvent in the above mixture (water: water-immiscible solvent) is not particularly limited, and examples thereof include 1:0.1 to 10, preferably 1:0.2 to 7, more preferably 1:0.3 to 5, and even more preferably 1:1 to 3.

[0023] According to one embodiment of the present invention, it is preferable that the mixture containing the lignocellulosic biomass and water used for the hydrothermal treatment does not contain a catalyst. Such catalysts include homogeneous catalysts and solid catalysts, and it is more preferable that solid catalysts (heterogeneous catalysts) are not included. Examples of the above solid catalysts include acid catalysts (i.e., solid acid catalysts).

[0024] In this specification, "hydrothermal treatment," also known as pressurized hot water treatment, refers to a method of hydrolyzing a target substance with an aqueous solution under high temperature and high pressure conditions. Water follows a saturated vapor pressure curve up to its critical point. Under high temperature and high pressure conditions slightly below the critical point, water maintains a subcritical state. Subcritical water acquires high hydrolytic ability due to an increase in the ion product of water. Hydrothermal treatment is a method that utilizes this property of subcritical water.

[0025] The temperature in the hydrothermal treatment is not particularly limited as long as it does not hinder the effects of the present invention, but for example, it can be 100°C to 280°C, preferably 120°C to 260°C, more preferably 140°C to 240°C, even more preferably 160°C to 220°C, and even more preferably 160°C to 200°C. By setting the above temperature, solid material can be efficiently obtained from the hydrothermal treatment. The pressure applied in the hydrothermal treatment is not particularly limited, but for example, it can be 0.1 to 6 MPa (1 to 60 atmospheres) in gauge pressure, preferably 0.1 to 4.0 MPa, and more preferably 0.5 to 1.4 MPa.

[0026] The duration of the hydrothermal treatment is not particularly limited, but for example, it can be 1 to 10 hours, preferably 2 to 8 hours, and more preferably 3 to 6 hours. This hydrothermal treatment duration is the holding time after reaching the temperature of 100°C to 280°C, and does not include the heating time required to reach that temperature.

[0027] In hydrothermal treatment, the mixture may be stirred to ensure uniform heating of the biomass raw material. Examples of such stirring speeds include 100 rpm or more and less than 2000 rpm, preferably 200 to 1500 rpm, more preferably 300 to 1000 rpm, and even more preferably 400 to 700 rpm.

[0028] This process requires pressurization and is therefore carried out in a pressure-resistant sealed container. During this process, the gas inside the container may be replaced with a less reactive inert gas, and the pressurized hot water treatment may be performed under that gas atmosphere. Examples of inert gases include nitrogen, as well as noble gases such as helium, neon, argon, and xenon. Nitrogen or argon are preferred.

[0029] (Biomass preparation process) The "biomass preparation step" is a step in which lignocellulosic biomass is treated to a suitable state for use in the pressurized hot water treatment step. This step is an optional step performed before the hydrothermal treatment step and may be performed as needed, but from the viewpoint of obtaining a larger amount of solid material from the hydrothermal treatment, i.e., improving the yield of the solid material, the biomass preparation step may be omitted. In particular, when utilizing cellulose in lignocellulosic biomass, it is necessary to crush the lignocellulosic biomass, but the crushing step is known to be costly. This crushing step can be omitted in order to utilize hemicellulose in lignocellulosic biomass and improve the yield of solid material from the hydrothermal treatment.

[0030] When carrying out this biomass preparation process, the process may include, for example, the pulverization (preferably coarse pulverization) of lignocellulosic biomass. The method for pulverizing the lignocellulosic biomass may be any known method and is not particularly limited. Generally, pulverization can be carried out using a pulverizer, crusher, ball mill, etc. The length of the longest part of the lignocellulosic biomass particles obtained after this process is not particularly limited, but for example, it may be 2 mm or more, preferably 3 mm or more, more preferably 5 mm or more, and even more preferably 10 mm or more. There is no particular upper limit, but for example, it may be 50 mm or less, preferably 40 mm or less, more preferably 30 mm or less, and even more preferably 20 mm or less.

[0031] Although lignocellulosic biomass can have a high water content depending on the type, the present invention does not necessarily require drying the lignocellulosic biomass because the following hydrothermal treatment step is carried out in the presence of water.

[0032] (solid-liquid separation process) The "solid-liquid separation process" is a process of separating the mixture after the hydrothermal treatment process into solid components (hereinafter also referred to as hydrothermal treated material) and liquid components. The mixture after the hydrothermal treatment process contains a liquid component which is an aqueous solution and / or a water-particle solvent containing pentose sugars such as xylose and arabinose produced by the hydrolysis of hemicellulose in lignocellulosic biomass, or furfural produced by their dehydration reaction, and a solid component (i.e., hydrothermal treated material) which contains undecomposed lignocellulosic biomass (including cellulose and lignin). The hydrothermal treated material contains solid matter with a maximum length of 2 mm or more.

[0033] Therefore, the objective of this process is to separate the mixture after the pressurized hot water treatment process into solid and liquid components, which are lignocellulosic biomass residues, and to recover the liquid and solid components (i.e., hydrothermal treated material) containing furfural.

[0034] The solid-liquid separation method may be any known method capable of separating the solid and liquid components. Examples include filtration, centrifugation, static precipitation, or a combination thereof.

[0035] In the case of filtration, the filtration method is not particularly limited. For example, either a pressure-controlled method such as reduced-pressure filtration or a gravity-feed method may be used. Furthermore, the filters used for filtration may include metal mesh filters, plastic mesh filters, cloth filters, charcoal filters, filter paper (paper filters), membrane filters, hollow branched fiber membrane filters, microfilters, Celite filters, diatomaceous earth, or combinations thereof. The filters may be single-layer or multi-layer.

[0036] (purification process) The "purification process" is a process in which, for example, the aqueous layer and organic layer are separated from the liquid component consisting of two layers (a aqueous layer and an organic layer) after the solid-liquid separation process, and the furfural is concentrated and purified. Specifically, methods such as extraction and distillation can be applied, but there are no restrictions on the purification method, and any known purification method can be used. This process is optional and can be performed as needed.

[0037] The liquid component after the solid-liquid separation process contains pentoses such as xylose and arabinose, which are produced by the hydrolysis of hemicellulose along with furfural. By dehydrating these pentoses, more furfural can be obtained. The furfural produced in the aqueous layer moves to the organic layer, where overreactions such as decomposition and polymerization are suppressed.

[0038] For example, the aqueous layer and the organic layer may be dehydrated by distillation to concentrate and purify the furfural, and the distillation method is not particularly limited. Any known distillation method can be used. For example, batch distillation using a distillation column or continuous distillation can be used.

[0039] (Hydrothermally treated lignocellulosic biomass) As described above, the solid component obtained by removing the liquid component from the mixture after the hydrothermal treatment process of lignocellulosic biomass is called the hydrothermal treated product. The hydrothermal treated product of lignocellulosic biomass contains solid matter with a longest part length of 2 mm or more (hereinafter also simply referred to as solid matter) and powder with a longest part length of less than 2 mm. The content of solid matter with a longest part length of 2 mm or more relative to the total amount of the hydrothermal treated product (also referred to as the solid content in the hydrothermal treated product) is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, from the viewpoint of ease of handling as a raw material for power generation, and there is no particular upper limit, but it is 100% by mass or less, preferably 99% by mass or less.

[0040] (Process for obtaining solid material from hydrothermally treated lignocellulosic biomass) The "step for obtaining solid material from hydrothermally treated biomass" is a step for separating the hydrothermally treated lignocellulosic biomass into solid material with a longest part length of 2 mm or more and powder with a longest part length of less than 2 mm. The separation method may be any known method capable of separating the solid material and powder. Examples include filtration, centrifugation, sedimentation by standing, or a combination thereof.

[0041] In the case of filtration, the filtration method is not particularly limited as long as it can separate solid matter. For example, either a pressure-controlled method such as vacuum filtration or a gravity-feed method may be used. The filters used for filtration can be metal mesh filters, plastic mesh filters, or combinations thereof. The filters can be single-layer or multi-layer.

[0042] (Solid material from hydrothermally treated lignocellulosic biomass) According to one embodiment of the present invention, it is preferable that the solid material of hydrothermally treated lignocellulosic biomass has at least one of the following properties compared to the lignocellulosic biomass before hydrothermal treatment: higher calorific value, lower sodium content, lower potassium content, and lower chlorine content. Therefore, the solid material of hydrothermally treated lignocellulosic biomass having the above properties, or hydrothermally treated lignocellulosic biomass containing such solid material, can be suitably used as a raw material for biomass power generation. Furthermore, sodium and potassium are known to cause line clogging in biomass boilers. Therefore, since the sodium and potassium content of the solid material of hydrothermally treated lignocellulosic biomass is reduced compared to the sodium and potassium content of the lignocellulosic biomass before hydrothermal treatment, it is advantageous when using hydrothermally treated lignocellulosic biomass as a raw material for power generation from the viewpoint of reducing line clogging in biomass boilers. In addition, as described above, it is preferable that the longest part of the solid material of hydrothermally treated lignocellulosic biomass has a length of 2 mm or more. Therefore, solid materials from hydrothermally treated lignocellulosic biomass have an advantage when used as a raw material for biomass power generation because they are easy to handle (for example, easy to transport and store).

[0043] (Properties of solid material from hydrothermally treated lignocellulosic biomass) According to one embodiment of the present invention, it is preferable that the calorific value per unit weight of the solid material of the hydrothermally treated lignocellulosic biomass is higher than the calorific value of the lignocellulosic biomass before hydrothermal treatment. According to another embodiment of the present invention, the calorific value per unit weight of the solid material (after drying) of the hydrothermally treated lignocellulosic biomass is, for example, 15,000 J / g or more, preferably 18,000 J / g or more, more preferably 20,000 J / g or more, even more preferably 21,000 J / g or more, and even more preferably 22,000 J / g or more. The upper limit of the calorific value is not particularly limited, but for example, it is 30,000 J / g or less. The calorific value per unit weight of the solid material of the hydrothermally treated lignocellulosic biomass can be measured using a calorimeter. Such measurements can be easily performed using a commercially available calorimeter (for example, a Nenken-type automatic cylinder calorimeter (for example, manufactured by Shimadzu Corporation)) in accordance with the method described in JIS K 2279:2003.

[0044] According to one embodiment of the present invention, the sodium content of the solid material of the hydrothermally treated lignocellulosic biomass is reduced compared to the sodium content of the lignocellulosic biomass before hydrothermal treatment. According to another embodiment of the present invention, the sodium content of the solid material of the hydrothermally treated lignocellulosic biomass is, for example, 100 ppm by mass or less, preferably 50 ppm by mass or less, more preferably 15 ppm by mass or less, and even more preferably 10 ppm by mass or less. The lower limit of the sodium content of the solid material of the hydrothermally treated material is not particularly limited, but for example, it is 0.1 ppm by mass or more. The sodium content of the solid material of the hydrothermally treated lignocellulosic biomass can be measured by inductively coupled plasma emission spectrometry. Such measurements can be easily performed using a commercially available ICP emission spectrometer (for example, manufactured by Hitachi High-Tech Science Corporation).

[0045] According to one embodiment of the present invention, the potassium content of the solids in the hydrothermally treated lignocellulosic biomass is reduced compared to the potassium content of the lignocellulosic biomass before hydrothermal treatment. According to another embodiment of the present invention, the potassium content of the solids in the hydrothermally treated lignocellulosic biomass is, for example, 700 ppm by mass or less, preferably 500 ppm by mass or less, more preferably 200 ppm by mass or less, and even more preferably 100 ppm by mass or less. The lower limit of the potassium content of the solids in the hydrothermally treated product is not particularly limited, but for example, it is 0.1 ppm by mass or more. The potassium content of the solids in the hydrothermally treated lignocellulosic biomass can be measured by inductively coupled plasma emission spectrometry. Such measurements can be easily performed using commercially available ICP emission spectrometers (e.g., Hitachi High-Tech Science Corporation).

[0046] According to one embodiment of the present invention, the chlorine content of the solid material of the hydrothermally treated lignocellulosic biomass is reduced compared to the chlorine content of the lignocellulosic biomass before hydrothermal treatment. According to another embodiment of the present invention, the chlorine content of the solid material of the hydrothermally treated lignocellulosic biomass is, for example, 600 ppm by mass or less, preferably 300 ppm by mass or less, more preferably 100 ppm by mass or less, and even more preferably 50 ppm by mass or less. The lower limit of the potassium content of the solid material of the hydrothermally treated product is not particularly limited, but for example, 1 ppm by mass or more. The chlorine content of the solid material of the hydrothermally treated lignocellulosic biomass can be measured by inductively coupled plasma emission spectrometry. Such measurements can be easily performed using a commercially available ICP emission spectrometer (for example, manufactured by Hitachi High-Tech Science Corporation).

[0047] The present invention provides a method for producing furfural and hydrothermally treated lignocellulosic biomass, which allows for the production of furfural from lignocellulosic biomass and, further, the production of hydrothermally treated lignocellulosic biomass that can be used as a raw material for power generation. The amount of furfural produced from lignocellulosic biomass is not particularly limited. The amount of furfural produced can be appropriately set depending on the type of biomass raw material used, but the amount produced per gram of raw material is, for example, more than 5 mg, preferably 5.5 mg or more, more preferably 10 mg or more, even more preferably 15 mg or more, particularly preferably 20 mg or more, and most preferably 30 mg or more. The upper limit of the amount of furfural produced per gram of raw material is not particularly limited, but for example, it is 300 mg or less, preferably 200 mg or less, and more preferably 100 mg or less. The amount of furfural produced can be calculated by measuring the furfural concentration in a mixture containing lignocellulosic biomass and water after hydrothermal treatment. If the mixture contains a water-incompatible solvent along with water, the concentration is determined as the sum of the furfural concentration in the water and the furfural concentration in the water-incompatible solvent.

[0048] The concentration of furfural in water, as described above, is measured by high-performance liquid chromatography (HPLC). Such measurements can be easily performed using commercially available equipment and columns (SUGAR SC1211 column (Shodex)). For example, the above measurement can be performed under the following conditions: Equipment: Prominence (Shimadzu Corporation), Detector: UV detector, HPLC measurement conditions: Column: SUGAR SC1211 column (Shodex), Mobile phase: 35% acetonitrile-water, Flow rate: 0.7 mL / min, Column temperature: 40°C.

[0049] Furthermore, the concentration of furfural in the water-incompatible solvent mentioned above is measured by gas chromatography-mass spectrometry (GC-MS). Such measurements can be easily performed using commercially available equipment and columns (CP-FFAP CB, 25m length x 0.32mm inner diameter, 0.30μm film thickness (Agilent Technologies)). The above measurement can be performed, for example, under the following conditions. Instrument: Agilent 6890N (Agilent Technologies), Detector: Flame Ionization (FID) detector, GC measurement conditions: Column: CP-FFAP CB, length 25m x inner diameter 0.32mm, film thickness 0.30μm (Agilent Technologies), Injection temperature: 250℃, Detection temperature: 220℃, Split ratio: 1 / 9, Gas flow rate: A mixture of hydrogen and air and helium (as a carrier gas) were used, with hydrogen 40mL / min, air 400mL / min, and helium 10mL / min, Heating: 70℃, held for 2 minutes, then heated to 250℃ at 6℃ / min, held at 250℃ for 8 minutes.

[0050] The present invention provides a method for producing furfural from hemicellulose in lignocellulosic biomass and for producing hydrothermally treated lignocellulosic biomass, which, along with furfural, can be used as a raw material for power generation. Therefore, the above production method can be used to produce hydrothermally treated lignocellulosic biomass for use as a raw material for power generation. Examples of such raw materials for power generation include those that are directly burned to generate electricity (biomass combustion power generation), those that are gasified and then burned to generate electricity (biomass gasification power generation), and those that generate biogas such as methane through microbial decomposition to generate electricity (biogas power generation). Preferably, the raw material is one that is directly burned to generate electricity. [Examples]

[0051] The present invention will be described in detail below with reference to examples and test examples, but the present invention is not limited to these examples and test examples. Unless otherwise noted, the units and measurement methods described herein are in accordance with Japanese Industrial Standards (JIS).

[0052] Method for measuring furfural concentration Method for measuring furfural concentration in aqueous layer (HPLC) The furfural concentration in the aqueous layer was determined by filtering with a syringe filter, and then analyzed and measured using HPLC (Prominence, Shimadzu Corporation) with a UV detector. The measurement conditions for HPLC are as follows: Column: SUGAR SC1211 column (manufactured by Shodex) Mobile phase: 35% acetonitrile-water Flow rate: 0.7mL / min Column temperature: 40℃

[0053] Method for measuring furfural concentration in a water-incompatible solvent layer (GC) The furfural concentration in the water-incompatible solvent layer was determined by filtration using a syringe filter, and then analyzed and measured using a flame ionization (FID) detector with a GC (Agilent 6890N, Agilent Technologies). The measurement conditions for GC are as follows: Column: CP-FFAP CB, length 25m x inner diameter 0.32mm, film thickness 0.30μm (manufactured by Agilent Technologies) Injection temperature: 250℃ Detection temperature: 220℃ Split ratio: 1 / 9 Gas flow rates: A mixture of hydrogen and air, along with helium (as a carrier gas), were used, with hydrogen flow rates of 40 mL / min, air flow rates of 400 mL / min, and helium flow rates of 10 mL / min. Heating: Heat to 70°C, hold for 2 minutes, then increase the temperature to 250°C at a rate of 6°C / minute, and hold at 250°C for 8 minutes.

[0054] Example 1: Hydrothermal treatment of palm kernel shells Palm kernel shells (PKS) were used as the lignocellulosic biomass. The PKS were subjected to hydrothermal treatment without any pretreatment such as drying or grinding. The longest part of the PKS used in the hydrothermal treatment was 15-25 mm in length. 1.00 g of PKS, 15 mL of water, and 30 mL of toluene were placed in a 100 mL autoclave (MMJ-100, OM Labtec Co., Ltd.) to obtain a mixture. The autoclave was sealed and purged with nitrogen, and then hydrothermal treatment was carried out at 180°C, a pressure of approximately 0.9 MPaG, and a stirring condition of 500 rpm for 6 hours. After the hydrothermal treatment, the obtained aqueous layer was analyzed by HPLC, and the obtained toluene layer was analyzed by GC to measure the amount of furfural produced. As a result, 7 mg / g-PKS of furfural was obtained from the aqueous layer, 51 mg / g-PKS of furfural was obtained from the toluene layer, for a total of 58 mg / g-PKS of furfural. The PKS residue after hydrothermal treatment was filtered by suction filtration (filter paper: Advantec No. 5B), washed with ethanol, and dried. The resulting solid (also called the hydrothermal treated material) was 0.61 g (61% by mass of the raw PKS). The obtained hydrothermal treated material was filtered through a metal mesh filter with a mesh size of 2 mm to remove powdery material, yielding 0.59 g (98% by mass of the obtained hydrothermal treated material) of solid material. The results obtained in Example 1 are shown in Table 1.

[0055] Example 2: Hydrothermal treatment of palm kernel shells (Hydrothermal treatment temperature: 160°C) Hydrothermal treatment was carried out in the same manner as in Example 1, except that the hydrothermal treatment temperature was set to 160°C, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0056] Example 3: Hydrothermal treatment of palm kernel shells (Hydrothermal treatment temperature: 170°C) Hydrothermal treatment was carried out in the same manner as in Example 1, except that the hydrothermal treatment temperature was set to 170°C, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0057] Example 4: Hydrothermal treatment of palm kernel shells (Hydrothermal treatment temperature: 200°C) Hydrothermal treatment was carried out in the same manner as in Example 1, except that the hydrothermal treatment temperature was set to 200°C, to obtain furfural, the hydrothermal treated product, and its solid form. The results obtained are shown in Table 1.

[0058] Example 5: Hydrothermal treatment of palm kernel shells (water-incompatible solvent: cyclopentyl methyl ether) Hydrothermal treatment was carried out in the same manner as in Example 1, except that cyclopentyl methyl ether was used instead of toluene as the water-immiscible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0059] Example 6: Hydrothermal treatment of palm kernel shells (water only) Hydrothermal treatment was carried out in the same manner as in Example 1, except that 45 mL of water was used instead of a water-incompatible solvent, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0060] Example 7: Hydrothermal treatment of palm kernel shells (acetic acid aqueous solution only) Hydrothermal treatment was carried out in the same manner as in Example 1, except that a water-incompatible solvent was not used for the hydrothermal treatment, and 45 mL of a 0.1 mol / L aqueous acetic acid solution was used. Furfural, the hydrothermal-treated product, and its solid form were obtained. The results obtained are shown in Table 1.

[0061] Example 8: Hydrothermal treatment of palm kernel shells (Hydrothermal treatment temperature: 220°C) Hydrothermal treatment was carried out in the same manner as in Example 1, except that the hydrothermal treatment temperature was set to 220°C, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0062] Example 9: Hydrothermal treatment of palm kernel shells (Hydrothermal treatment temperature: 240°C) Hydrothermal treatment was carried out in the same manner as in Example 1, except that the hydrothermal treatment temperature was set to 240°C, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0063] Example 10: Hydrothermal treatment of palm kernel shells (water-soluble solvent: ethanol) Hydrothermal treatment was carried out in the same manner as in Example 1, except that ethanol was used instead of toluene, to obtain furfural, the hydrothermal treated product, and its solid form. The results obtained are shown in Table 1.

[0064] Example 11: Hydrothermal treatment of palm kernel shells (water-compatible solvent: γ-valerolactone) Hydrothermal treatment was carried out in the same manner as in Example 1, except that γ-valerolactone was used instead of toluene, to obtain furfural, the hydrothermal-treated product, and its solid form. The results obtained are shown in Table 1.

[0065] [Table 1]

[0066] Test Example 1: Measurement of the calorific value of solids from hydrothermally treated palm kernel shells, as well as the content of Na, K, and Cl. The solid hydrothermal treated PKS obtained in Example 1 was dried together with the raw PKS at 130°C for 1 hour. The calorific value of the hydrothermal treated PKS solid and the raw PKS was measured in accordance with JIS K 2279:2003 using a Nuclear Energy Research Institute automatic cylinder calorimeter (CA-4AJ, Shimadzu Corporation). The Na, K, and Cl content was measured using an ICP emission spectrometer (PS3520UVDDII, Hitachi High-Tech Science Corporation) by inductively coupled plasma emission spectroscopy. The results are shown in Table 2. The calorific value of the hydrothermal treated PKS solid obtained in Examples 2 to 11, as well as the Na, K, and Cl content, were measured in the same manner as in Example 1. The calorific value of the hydrothermal treated PKS solid obtained in Examples 2 to 11, as well as the Na, K, and Cl content, were similar to those of the hydrothermal treated PKS solid obtained in Example 1.

[0067] [Table 2]

[0068] Example 12: Hydrothermal treatment of Japanese cedar Japanese cedar (Cryptomeria japonica) was used as the lignocellulosic biomass. Coarsely ground cedar, approximately 5 mm square, was used. No pretreatment such as drying was performed, and it was subjected to hydrothermal treatment as is. 0.33 g of cedar, 20 mL of water, and 20 mL of toluene were placed in a 100 mL autoclave (TVS-1, manufactured by Taikaku Glass Industry Co., Ltd.). The autoclave was sealed, purged with nitrogen, and hydrothermal treatment was carried out at 160°C, a pressure of approximately 0.6 MPaG, and a stirring condition of 1000 rpm for 4 hours. After hydrothermal treatment, the obtained aqueous layer was analyzed by HPLC, and the obtained toluene layer was analyzed by GC to measure the amount of furfural produced. 0.1 mg / g-cedar was obtained from the aqueous layer, 5.4 mg / g-cedar from the toluene layer, for a total of 5.5 mg / g-cedar furfural was obtained. The cedar residue after hydrothermal treatment was filtered by suction filtration (filter paper: Advantec No. 5B), washed with ethanol, and dried. The obtained solid (also called hydrothermally treated material) was 0.22 g (67% by mass of the raw cedar material (i.e., recovery rate of hydrothermally treated material)). The obtained hydrothermally treated material was filtered through a metal mesh filter with a mesh size of 2 mm to remove powdered material, and 0.21 g of solid material was obtained (96% by mass of the obtained hydrothermally treated material (i.e., solid content relative to the total amount of hydrothermally treated material)). The results obtained in Example 12 are shown in Table 3.

[0069] Example 13: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 170℃) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 170°C, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained (amount of furfural produced) are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the solid content relative to the total amount of hydrothermal-treated product in Example 13 were similar to those of the hydrothermal-treated product and the solid content relative to the total amount of hydrothermal-treated product in Example 12.

[0070] Example 14: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 180℃) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 180°C, to obtain furfural, hydrothermal treated material, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal treated material and the solid content relative to the total amount of hydrothermal treated material in Example 14 were similar to those of the hydrothermal treated material and solid content relative to the total amount of hydrothermal treated material in Example 12.

[0071] Example 15: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200℃) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C, to obtain furfural, hydrothermal treated material, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal treated material and the solid content relative to the total amount of hydrothermal treated material in Example 15 were similar to those of the hydrothermal treated material and solid content relative to the total amount of hydrothermal treated material in Example 12.

[0072] Example 16: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 220℃) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 220°C, to obtain furfural, hydrothermal treated material, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal treated material and the solid content relative to the total amount of hydrothermal treated material in Example 16 were similar to those of the hydrothermal treated material and solid content relative to the total amount of hydrothermal treated material in Example 12.

[0073] Example 17: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 250℃) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 250°C, to obtain furfural, hydrothermal treated material, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal treated material and the solid content relative to the total amount of hydrothermal treated material in Example 17 were similar to those of the hydrothermal treated material and solid content relative to the total amount of hydrothermal treated material in Example 12.

[0074] Example 18: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 180°C, water-incompatible solvent: hexane) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 180°C and hexane was used instead of toluene as the water-immiscible solvent used in the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 18 were about the same as the recovery rate of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 12.

[0075] Example 19: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200°C, water-incompatible solvent: hexane) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C, hexane was used instead of toluene as the water-incompatible solvent for the hydrothermal treatment, and 30 mL of water and 10 mL of hexane were used. Furfural, hydrothermal treated product, and its solids were obtained. The results are shown in Table 3. Furthermore, the recovery rate of the hydrothermal treated product and the solid content relative to the total amount of hydrothermal treated product in Example 19 were similar to those in Example 12.

[0076] Example 20: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200°C, water-incompatible solvent: cyclopentyl methyl ether) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C and cyclopentyl methyl ether was used instead of toluene as the water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 20 were about the same as the recovery rate of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 12.

[0077] Example 21: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200°C, water-incompatible solvent: 4-methyltetrahydropyran) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C and 4-methyltetrahydropyran was used instead of toluene as the water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 21 were similar to those of the hydrothermal-treated product and the content of solids relative to the total amount of hydrothermal-treated product in Example 12.

[0078] Example 22: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 180°C, water only) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 180°C and 40 mL of water was used instead of a water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 22 were similar to those of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 12.

[0079] Example 23: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 190°C, water only) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 190°C and 40 mL of water was used instead of a water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 23 were similar to those of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 12.

[0080] Example 24: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200°C, water only) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C and 40 mL of water was used instead of a water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 24 were similar to those of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 12.

[0081] Example 25: Hydrothermal treatment of Japanese cedar (Hydrothermal treatment temperature: 200°C, water only) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C and 60 mL of water was used instead of a water-incompatible solvent for the hydrothermal treatment, to obtain furfural, the hydrothermal-treated product, and its solids. The results obtained are shown in Table 3. Furthermore, the recovery rate of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 25 were similar to those of the hydrothermal-treated product and the solid content relative to the total amount of the hydrothermal-treated product in Example 12.

[0082] Comparative Example 1: Hydrothermal treatment of Japanese cedar (water-incompatible solvent: toluene) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C, water was not used in the hydrothermal treatment, and 40 mL of toluene was used as a water-incompatible solvent, to obtain furfural, the hydrothermal treated product, and its solid form. The results obtained are shown in Table 3.

[0083] Comparative Example 2: Hydrothermal treatment of Japanese cedar (water-incompatible solvent: hexane) Hydrothermal treatment was carried out in the same manner as in Example 12, except that the hydrothermal treatment temperature was set to 200°C, water was not used in the hydrothermal treatment, and 40 mL of hexane was used as a water-incompatible solvent, to obtain furfural, the hydrothermal treated product, and its solid form. The results obtained are shown in Table 3.

[0084] [Table 3]

Claims

1. A method for producing furfural from hemicellulose in lignocellulosic biomass and a hydrothermally treated lignocellulosic biomass from lignocellulosic biomass, comprising the step of hydrothermally treating a mixture containing lignocellulosic biomass and water at a temperature of 100°C to 280°C.

2. A method for producing a hydrothermally treated product of furfural and lignocellulosic biomass according to claim 1, wherein the mixture does not contain a solid catalyst.

3. A method for producing a hydrothermally treated product of furfural and lignocellulosic biomass according to claim 1 or 2, wherein the mixture further comprises a solvent that is immiscible with water.

4. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 3, wherein the water-incompatible solvent is at least one water-incompatible solvent selected from the group consisting of toluene, cyclopentyl methyl ether, 4-methyltetrahydropyran, hexane, and xylene.

5. A method for producing hydrothermally treated furfural and lignocellulosic biomass according to claim 1, wherein the hydrothermal treatment is carried out under pressure of 0.1 to 4 MPa.

6. A method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 1 or 2, wherein the content of solids with a longest part length of 2 mm or more is 50% by mass or more of the total amount of the hydrothermally treated lignocellulosic biomass.

7. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 6, further comprising the step of removing powder with a longest part length of less than 2 mm from hydrothermally treated lignocellulosic biomass to obtain solid material of the hydrothermally treated lignocellulosic biomass.

8. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 6, wherein the amount of heat generated per unit weight of the solids in the hydrothermally treated lignocellulosic biomass is greater than the amount of heat generated in the lignocellulosic biomass before hydrotherm treatment.

9. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 6, wherein the sodium content of the solids in the hydrothermally treated lignocellulosic biomass is reduced compared to the sodium content of the lignocellulosic biomass before hydrotherm treatment.

10. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 6, wherein the potassium content of the solids in the hydrothermally treated lignocellulosic biomass is reduced compared to the potassium content of the lignocellulosic biomass before hydrotherm treatment.

11. The method for producing furfural and hydrothermally treated lignocellulosic biomass according to claim 6, wherein the chlorine content of the solids in the hydrothermally treated lignocellulosic biomass is reduced compared to the chlorine content of the lignocellulosic biomass before hydrothermal treatment.

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