Method for producing cellulose material

Abstract

This method for producing a cellulose material comprises: a hydrothermal treatment step for subjecting a plant biomass to a hydrothermal treatment in an acid aqueous solution; and a bleaching hydrothermal treatment step for subjecting the plant biomass, which has been subjected to the hydrothermal treatment step, to a hydrothermal treatment in an alkaline aqueous solution containing a bleaching agent.

Description

Method for producing cellulose materials

[0001] The present invention relates to a method for producing cellulosic material from plant biomass.

[0002] Cellulose is the most abundant renewable substance and has been used continuously from ancient times to modern technological societies. Cellulose, a plant-derived fiber, has a low environmental impact and is a sustainable resource. It also has excellent properties, such as a high modulus of elasticity, high strength, and a low coefficient of linear expansion. Therefore, it is used in a wide range of applications, such as materials for paper, films, and sheets, and as a resin composite material (e.g., a reinforcing agent for resins).

[0003] Although there are conventional methods for producing cellulose materials from plant biomass, there is a need for the development of a faster and simpler method. For example, one example of a method for producing such cellulose materials is a method that includes a step of cutting trees with the bark still attached to obtain chips and a step of chemically pulping the obtained chips (see, for example, Patent Document 1).

[0004] JP 2015-190095 A

[0005] An object of the present invention is to provide a method for easily and quickly producing a cellulose material from plant biomass.

[0006] The present inventors have discovered that cellulose materials can be obtained easily and in a short time by hydrothermally treating plant biomass in an aqueous acid solution and then in an aqueous alkaline solution containing a bleaching agent, and have thus completed the present invention.

[0007] That is, the present invention provides the following: [1] A method for producing a cellulose material, comprising: a hydrothermal treatment step of hydrothermally treating plant biomass in an acid aqueous solution; and a bleaching hydrothermal treatment step of hydrothermally treating the plant biomass that has undergone the hydrothermal treatment step in an alkaline aqueous solution containing a bleaching agent. [2] A method for producing a cellulose material, comprising: a bleaching hydrothermal treatment step of hydrothermally treating woody biomass in an alkaline aqueous solution containing a bleaching agent; and a hydrothermal treatment step of hydrothermally treating the woody biomass that has undergone the bleaching hydrothermal treatment step in an acid aqueous solution. [3] A method for producing a cellulose material according to [1] or [2] above, wherein the treatment temperature in the hydrothermal treatment step is 120 to 140°C. [4] A method for producing a cellulose material according to any of [1] to [3] above, wherein the treatment time in the hydrothermal treatment step is 20 to 40 minutes. [5] A method for producing a cellulose material according to any of [1] to [4] above, wherein the treatment temperature in the bleaching hydrothermal treatment step is 120 to 140°C. [6] The method for producing a cellulose material according to any one of [1] to [5] above, wherein the treatment time in the bleaching hydrothermal treatment step is 20 to 40 minutes. [7] The method for producing a cellulose material according to any one of [1] and [3] to [6] above, wherein the plant biomass is bamboo or wood. [8] The method for producing a cellulose material according to any one of [1] to [7] above, wherein the produced cellulose material contains 70 mass% or more of cellulose.

[0008] [9] A method for separating and recovering a plant biomass component, comprising an acid-hydrothermal-treated biomass component recovery step and an alkaline-hydrothermal-treated biomass component recovery step, for separating and recovering plant biomass components from plant biomass, characterized by comprising: an acid-hydrothermal-treated biomass component recovery step of hydrothermally treating the plant biomass or a product of the alkaline-hydrothermal-treated biomass component recovery step in an acid aqueous solution to precipitate insoluble components of the acid-hydrothermal-treated biomass, and separating and recovering the insoluble and soluble components of the acid-hydrothermal-treated biomass; and an alkaline-hydrothermal-treated biomass component recovery step of hydrothermally treating the plant biomass or a product of the acid-hydrothermal-treated biomass component recovery step in an alkaline aqueous solution containing a bleaching agent to precipitate insoluble components of the alkaline-hydrothermal-treated biomass, and separating and recovering the insoluble and soluble components of the alkaline-hydrothermal-treated biomass.

[10] The method for separating and recovering a plant biomass component according to [9] above, wherein the plant biomass is bamboo, the soluble component of the acid-hydrothermal-treated biomass in the acid-hydrothermal-treatment biomass component recovery step is a solution containing lignin material, the plant biomass to be treated in the alkaline hydrothermal-treatment biomass component recovery step is the insoluble component of the acid-hydrothermal-treatment biomass, the insoluble component of the alkaline hydrothermal-treatment biomass is a solution containing cellulose material, and the soluble component is a solution containing hemicellulose material.

[11] The method for separating and recovering a plant biomass component according to [9] above, wherein the plant biomass is wood, the soluble component of the acid-hydrothermal-treatment biomass in the acid-hydrothermal-treatment biomass component recovery step is a solution containing hemicellulose material, the plant biomass to be treated in the alkaline hydrothermal-treatment biomass component recovery step is the insoluble component of the acid-hydrothermal-treatment biomass, the insoluble component of the alkaline hydrothermal-treatment biomass is a solution containing cellulose material, and the soluble component is a solution containing lignin material.

[0009] According to the present invention, cellulose materials can be produced from plant biomass easily and in a short time.

[0010] FIG. 1 is a graph showing the lignin removal rate versus the concentration of the aqueous nitric acid solution used in the hydrothermal process.

[0011] <Method for producing a cellulose material> The method for producing a cellulose material of the present invention is characterized by comprising a hydrothermal treatment step of hydrothermally treating plant biomass in an acid aqueous solution, and a bleaching hydrothermal treatment step of hydrothermally treating the plant biomass that has undergone the hydrothermal treatment step in an alkaline aqueous solution containing a bleaching agent.

[0012] According to the production method of the present invention, cellulose material can be produced easily and in a short time from plant biomass by hydrothermally treating plant biomass in an acid aqueous solution and then hydrothermally treating it in an alkaline aqueous solution containing a bleaching agent.

[0013] Furthermore, the cellulose material obtained by the production method of the present invention is insoluble in an alkaline aqueous solution, and is therefore believed to maintain the crystalline structure of cellulose type I, which is the natural crystalline form of cellulose.

[0014] Plant biomass used in the production method of the present invention can include biomass derived from plants, such as herbaceous biomass and woody biomass. Examples of herbaceous biomass include bamboo, grains, beans, and sugarcane. Examples of woody biomass include trees such as broad-leaved trees and coniferous trees, and oil palm. These plant biomass species can be used alone or in combination. Examples of plant biomass parts include trunks (stem), branches, roots, and leaves, and these parts can be used in combination. Plant biomass can be in various forms, such as firewood, chips, pellets, particles, and powder. Bamboo is preferred as the herbaceous biomass of the present invention, with bamboo flour being particularly preferred. Wood is preferred as the woody biomass of the present invention, with wood flour being particularly preferred.

[0015] The cellulose material obtained by the production method of the present invention is a cellulose fiber obtained by removing lignin, hemicellulose, etc. from plant biomass, and preferably contains 70% by mass or more of cellulose. When using herbaceous biomass, it is preferable that it contains 80% by mass or more of cellulose, more preferably 85% by mass or more. When using woody biomass, it is preferable that it contains 70% by mass or more of cellulose, more preferably 74% by mass or more. Such a high-content cellulose material can be used for processed products such as cellulose nanofiber (CNF). Furthermore, the production method of the present invention can easily produce a high-content cellulose material.

[0016] Each step will be explained below. [Hydrothermal Treatment Step] The hydrothermal treatment step is a step in which plant biomass is hydrothermally treated in an acidic aqueous solution. In this step, for example, a container in which plant biomass is immersed in an acidic aqueous solution is placed in a high-pressure reactor such as an autoclave or a pressure cooker, and the container is heated to cause a reaction in the presence of high-temperature, high-pressure steam. The hydrothermal treatment in this step enables sufficient separation of the plant biomass into its components. Note that this step and the subsequent hydrothermal treatment do not require expensive, high-performance equipment and can be performed using a simple device such as a household pressure cooker.

[0017] For example, when using herbaceous biomass, the hydrothermal treatment in this step can achieve sufficient delignification, i.e., the herbaceous biomass can be separated into insoluble components and soluble lignin-containing materials (lignin materials), and the lignin materials can be recovered as a solution containing the lignin materials.

[0018] Furthermore, when woody biomass is used, for example, the hydrothermal treatment of this step can achieve sufficient dehemicellulose removal. That is, the woody biomass can be separated into insoluble components and low-temperature decomposition products (hemicellulose material) containing soluble hemicellulose and its decomposition product, low-molecular-weight glucose, and the hemicellulose material can be recovered as a solution containing the hemicellulose material.

[0019] The treatment temperature is, for example, greater than 100 to 200°C. From the viewpoint of efficient treatment, 110 to 180°C is preferred, 120 to 160°C is more preferred, and 120 to 140°C is even more preferred. The pressure is saturated water vapor pressure. The treatment time, which varies depending on the temperature and pressure, is, for example, about 1 to 360 minutes, preferably about 1 to 60 minutes, more preferably 10 to 50 minutes, and even more preferably about 20 to 40 minutes. The present invention can achieve sufficient delignification and dehemicellulose of plant biomass in a short period of time. At the same time, lignin materials and hemicellulose materials can be separated and recovered.

[0020] Examples of the aqueous acid solution include aqueous solutions of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, etc. Two or more different aqueous acids may be mixed and used. Among these, aqueous nitric acid solution is preferred because it is relatively easy to handle and can more effectively exert the effects of the present invention.

[0021] The acid concentration of the aqueous acid solution is, for example, 0.05 to 5.0 M, and from the viewpoint of more effectively decomposing the plant biomass components, it is preferably 0.1 to 3.0 M, more preferably 0.2 to 2.0 M. In this step, when woody biomass is used, as described above, hemicellulose can be removed, and at the same time, the lignin removal rate can be controlled by controlling the acid concentration of the aqueous acid solution (see Figure 1). Therefore, the amount of lignin in the finally obtained cellulose material can be adjusted by adjusting the treatment in the hydrothermal bleaching step.

[0022] The amount of the aqueous acid solution to be added to the plant biomass is, for example, preferably 1 to 40 ml, more preferably 10 to 30 ml, and even more preferably 15 to 25 ml per 1 g of plant biomass.

[0023] The pH of the aqueous acid solution is, for example, 4.0 or less, preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 0.3 to 2.0.

[0024] [Bleaching Hydrothermal Treatment Step] The bleaching hydrothermal treatment step is a step in which the plant biomass that has undergone the hydrothermal treatment step is hydrothermally treated in an alkaline aqueous solution containing a bleaching agent. In this step, for example, a container in which the plant biomass that has undergone the hydrothermal treatment step is immersed in an alkaline aqueous solution containing added bleach is placed in a high-pressure reactor such as an autoclave or a pressure cooker, and heated to carry out a reaction in the presence of high-temperature, high-pressure steam. The hydrothermal treatment in this step can achieve sufficient component decomposition of the plant biomass that has undergone the hydrothermal treatment step.

[0025] For example, when using herbaceous biomass, the hydrothermal treatment in this step can dissolve hemicellulose materials in the solution and precipitate cellulose materials. That is, the hydrothermal treatment in this step separates the biomass into cellulose as an insoluble component and hemicellulose materials as a soluble component, and the cellulose materials and the hemicellulose materials can be recovered as a solution containing the hemicellulose materials, respectively.

[0026] Furthermore, for example, when woody biomass is used, the hydrothermal treatment in this step can dissolve the lignin material in the solution and precipitate the cellulose material. That is, the hydrothermal treatment in this step separates the cellulose as an insoluble component from the lignin material and other soluble components, and the cellulose material and the lignin material can be recovered as a solution containing the lignin material.

[0027] Furthermore, when wood from woody biomass is used as the plant biomass, the order of the hydrothermal treatment step and the bleaching / hydrothermal treatment step may be reversed. That is, another example of a method for producing a cellulose material of the present invention is a method comprising a bleaching / hydrothermal treatment step in which woody biomass is hydrothermally treated in an alkaline aqueous solution containing a bleaching agent, and a hydrothermal treatment step in which the woody biomass that has been subjected to the bleaching / hydrothermal treatment step is hydrothermally treated in an acidic aqueous solution.

[0028] The treatment temperature is, for example, greater than 100 to 200°C, and from the viewpoint of efficient treatment, 110 to 180°C is preferred, 120 to 160°C is more preferred, and 120 to 140°C is even more preferred. The pressure is saturated water vapor pressure. The treatment time, which varies depending on the temperature and pressure, is, for example, about 1 to 360 minutes, preferably about 1 to 60 minutes, more preferably 10 to 50 minutes, and even more preferably about 20 to 40 minutes. The present invention can achieve sufficient dehemicellulose and delignification of plant biomass in a short period of time. At the same time, cellulose material can be separated and recovered from hemicellulose material and lignin material.

[0029] Examples of bleaching agents include hydrogen peroxide, ozone, sodium percarbonate, sodium hypochlorite, potassium hypochlorite, sodium hyposulfite (hydrosulfite), and thiourea dioxide. Among these, oxygen-based bleaching agents are preferred, with common oxygen-based bleaching agents such as hydrogen peroxide and sodium percarbonate being more preferred, and hydrogen peroxide being particularly preferred. Use of oxygen-based bleaching agents can significantly reduce the environmental impact compared to the use of conventional chlorine-based bleaching agents.

[0030] For bleaches that do not themselves exhibit alkalinity, alkalis such as sodium silicate, sodium carbonate, sodium hydroxide, calcium hydroxide, potassium hydroxide, etc. may be added, or two or more different alkalis may be added. Among these, sodium metasilicate and sodium metasilicate hydrate are preferred, and their use in combination with oxygen-based bleaches such as hydrogen peroxide and sodium percarbonate is particularly preferred.

[0031] The amount of the alkaline aqueous solution added to the plant biomass that has been subjected to the hydrothermal treatment step is, for example, preferably 1 to 40 ml, more preferably 3 to 30 ml, and even more preferably 5 to 20 ml per 1 g of plant biomass.

[0032] The pH of the alkaline aqueous solution is, for example, preferably 9 to 12, and more preferably 9.5 to 11.5.

[0033] <Method for Separating and Recovering Plant Biomass Components> The method for separating and recovering plant biomass components of the present invention comprises an acid-hydrothermal-treated biomass component recovery step and an alkaline-hydrothermal-treated biomass component recovery step, and is a method for separating and recovering plant biomass components separately from plant biomass. The method is characterized by comprising an acid-hydrothermal-treated biomass component recovery step in which the plant biomass or the product of the acid-hydrothermal-treated biomass component recovery step is hydrothermally treated in an acidic aqueous solution to precipitate and separate the insoluble component of the acid-hydrothermal-treated biomass, and recovering the insoluble component and soluble component of the acid-hydrothermal-treated biomass; and an alkaline-hydrothermal-treated biomass component recovery step in which the plant biomass or the product of the acid-hydrothermal-treated biomass component recovery step is hydrothermally treated in an alkaline aqueous solution containing a bleaching agent to precipitate and separate the insoluble component of the alkaline-hydrothermal-treated biomass, and recovering the insoluble component and soluble component of the alkaline-hydrothermal-treated biomass. In the plant biomass component separation and recovery method of the present invention, the acid hydrothermal treatment biomass component recovery step corresponds to the hydrothermal treatment step in the above-mentioned cellulosic material production method, and the alkali hydrothermal treatment biomass component recovery step corresponds to the bleaching hydrothermal treatment step. Furthermore, each treatment has the same configuration as that described in the above-mentioned cellulosic material production method, and therefore, a description thereof will be omitted.

[0034] In the plant biomass component separation and recovery method of the present invention, the order of the acidic hydrothermal treatment biomass component recovery step and the alkaline hydrothermal treatment biomass component recovery step is not particularly limited, but it is preferable to perform the alkaline hydrothermal treatment biomass component recovery step after the acidic hydrothermal treatment biomass component recovery step.

[0035] When herbaceous biomass is used as the plant biomass, a specific example can be mentioned in which the plant biomass is bamboo, the soluble component of the acid-hydrothermal-treated biomass in the acid-hydrothermal-treated biomass component recovery step is a solution containing lignin material, the plant biomass to be treated in the alkaline-hydrothermal-treated biomass component recovery step is the insoluble component of the acid-hydrothermal-treated biomass, the insoluble component of the alkaline-hydrothermal-treated biomass contains cellulose material, and the soluble component is a solution containing hemicellulose material.

[0036] When woody biomass is used as the plant biomass, a specific example can be mentioned in which the plant biomass is wood, the soluble component of the acid-hydrothermal-treated biomass in the acid-hydrothermal-treated biomass component recovery step is a solution containing hemicellulose material, and the plant biomass subjected to treatment in the alkaline-hydrothermal-treated biomass component recovery step is the insoluble component of the acid-hydrothermal-treated biomass, the insoluble component of the alkaline-hydrothermal-treated biomass containing cellulose material, and the soluble component is a solution containing lignin material.

[0037] As the separation treatment of insoluble components (precipitates) in each step, a conventionally known solid-liquid separation treatment can be used, for example, a treatment by suction filtration using a vacuum pump. Furthermore, as the washing treatment of the precipitate that has undergone the solid-liquid separation treatment, a conventionally known washing treatment can be used. As the washing treatment of the precipitate of the acid hydrothermal treated biomass, it is preferable to adjust the pH to about 6 to 7 at the same time as washing. A specific example is washing using water. It is preferable that the precipitate that has undergone the washing treatment is dried. As the drying treatment, a conventionally known drying treatment can be used, for example, a method using a dryer or natural drying can be used.

[0038] The method for separating and recovering plant biomass components of the present invention allows for easy separation and recovery of cellulose materials, lignin materials, and hemicellulose materials. Specifically, when herbaceous biomass is used as the plant biomass, the method for separating and recovering plant biomass components of the present invention allows for the hydrothermal treatment in the acid hydrothermal treatment biomass component recovery step to recover lignin materials as a solution containing lignin materials, and also allows the hydrothermal treatment in the alkaline hydrothermal treatment biomass component recovery step to recover cellulose materials as a precipitate and hemicellulose materials as a solution containing hemicellulose materials. Furthermore, when woody biomass is used as the plant biomass, the hydrothermal treatment in the acid hydrothermal treatment biomass component recovery step to recover hemicellulose materials as a solution containing hemicellulose materials, and also allows the hydrothermal treatment in the alkaline hydrothermal treatment biomass component recovery step to recover cellulose materials as a precipitate and lignin materials as a solution containing lignin materials.

[0039] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0040] <Production of Cellulose Material> Cellulose materials were produced using plant biomass.

[0041] [Preparation of pulverized plant biomass] Chips of bamboo culms from moso bamboo and wood chips from thinned coniferous trees, including cedar, were prepared as plant biomass. All plant biomass was dried in an oven for 48 hours to reduce the initial moisture content, and then pulverized to a particle size of 500 μm or less using a grinder (DC-HOUSE 15 kg / h 110 V electric grinder) to obtain pulverized biomass. The obtained pulverized biomass was stored at room temperature in a sealed plastic bag.

[0042] [Hydrothermal treatment with an acid solution] 12.5 g of weighed pulverized biomass was added to a 500 mL Erlenmeyer flask and mixed with 250 mL of 0.5 M nitric acid solution. Subsequently, the mouth of the Erlenmeyer flask was closed with aluminum foil, and the biomass mixture was treated for 30 minutes under high-pressure steam at 132 ° C using an autoclave (AS ONE Science Autoclave NCC-1701). The treated pulverized biomass was then filtered, rinsed with distilled water, and washed multiple times until the pH reached 6 to 7. After washing, it was dried overnight in an oven at 80 ° C to obtain nitric acid autoclave-treated biomass.

[0043] [Bleaching Treatment with Alkaline Aqueous Solution] (Preparation of Bleaching Solution) 3.5 g of sodium metasilicate, 17.1 mL of 30% hydrogen peroxide solution, and 300 mL of tap water were mixed together. The mixture was stirred without applying heat.

[0044] (Bleaching treatment using an autoclave) Next, the prepared bleaching solution and 28 g of the nitric acid autoclaved biomass obtained by the hydrothermal treatment were added to a beaker, the beaker was closed with aluminum foil, and the biomass was treated for 30 minutes under high-pressure steam at 132 °C using an autoclave. The treated pulverized biomass was then filtered, rinsed with distilled water, and washed multiple times until the bleaching solution was removed. After washing, the biomass was dried overnight in an oven at 80 °C to obtain a bleached cellulose material.

[0045] (Analysis of Cellulose Materials) The components contained in the cellulose materials produced from the pulverized moso bamboo biomass (Example 1) and the cellulose material produced from pulverized conifer biomass (Example 2) were analyzed by the TAPPI method. The results are shown in Tables 1 and 2. For comparison, the results are also shown for bamboo powder biomass that underwent hydrothermal treatment only (Comparative Example 1), bamboo powder biomass that underwent hydrothermal treatment after bleaching hydrothermal treatment (Comparative Example 2), bamboo powder biomass that underwent only bleaching hydrothermal treatment (Comparative Example 3), untreated bamboo powder biomass (Comparative Example 4), wood powder biomass that underwent hydrothermal treatment only (Comparative Example 5), and untreated wood powder biomass (Comparative Example 6).

[0046]

[0047]

[0048] As shown in Tables 1 and 2, it was confirmed that the manufacturing method of the present invention can easily produce cellulose materials containing very high proportions of cellulose, approximately 88% in the case of bamboo and approximately 74% in the case of wood, under mild conditions and in a short time, namely, two 30-minute autoclave treatments at approximately 130°C.

[0049] Next, a cellulose material was produced using the pulverized moso bamboo biomass under modified conditions. Specifically, a cellulose material (Example 3) was produced using the same production procedure as the cellulose material (Example 1) except that the autoclave was replaced with a pressure cooker and the temperature was set to 130°C. Furthermore, a cellulose material (Example 4) was produced using the same production procedure as the cellulose material (Example 1) except that the reaction times for the hydrothermal treatment and bleaching hydrothermal treatment were each changed to 60 minutes.

[0050]

[0051] As shown in Table 3, it was confirmed that the cellulose material of the present invention can be produced using a pressure cooker instead of an autoclave according to the production method of the present invention (top row). It was also confirmed that the proportion of cellulose can be increased by extending the treatment time of the hydrothermal treatment with an aqueous nitric acid solution (bottom row).

[0052] Furthermore, a cellulose material (Example 5) was produced using the above-mentioned pulverized coniferous biomass under modified conditions. Specifically, a cellulose material (Example 5) was produced using the same production procedure as the above-mentioned cellulose material (Example 2), except that the order of the hydrothermal treatment with an acid aqueous solution and the bleaching treatment with an alkaline aqueous solution was reversed.

[0053]

[0054] As shown in Table 4, it was confirmed that, according to the manufacturing method of the present invention, when wood flour (woody biomass) is used, a cellulose material with a high content can be produced even when the order of the hydrothermal treatment with an acid aqueous solution and the bleaching treatment with an alkaline aqueous solution is reversed.

[0055] The cellulose material of the present invention produced as described above is insoluble in an alkaline aqueous solution, and is therefore considered to be cellulose type I, which exhibits high mechanical properties, rather than cellulose type II, which is alkali-soluble.

[0056] <Effect of Nitric Acid Aqueous Solution Concentration> The effect of the concentration of the nitric acid aqueous solution in the acid aqueous solution hydrothermal treatment (hydrothermal process) on the lignin removal rate was investigated using wood flour. The manufacturing procedure was the same as that for the cellulose material manufactured from the above-mentioned pulverized coniferous biomass (Example 2), except for the concentration of the nitric acid aqueous solution. Specifically, measurements were performed by changing the concentration of the nitric acid aqueous solution to 0.25 mol / L, 0.5 mol / L, 0.75 mol / L, 1.0 mol / L, and 1.25 mol / L.

[0057] The results are shown in Figure 1. As shown in Figure 1, it was confirmed that the lignin removal rate can be controlled by controlling the concentration of the nitric acid aqueous solution. Hemicellulose was sufficiently removed even with a low concentration nitric acid aqueous solution.

[0058] The present invention is industrially useful because it enables the production of cellulose materials.

Claims

1. A method for producing a cellulose material, comprising: a hydrothermal treatment step of subjecting plant biomass to hydrothermal treatment in an aqueous acid solution; and a bleaching hydrothermal treatment step of subjecting the plant biomass that has undergone the hydrothermal treatment step to hydrothermal treatment in an aqueous alkaline solution containing a bleaching agent.

2. A method for producing a cellulose material, comprising: a bleaching hydrothermal treatment step of subjecting lignocellulose biomass to hydrothermal treatment in an aqueous alkaline solution containing a bleaching agent; and a hydrothermal treatment step of subjecting the lignocellulose biomass that has undergone the bleaching hydrothermal treatment step to hydrothermal treatment in an aqueous acid solution.

3. The method for producing a cellulose material according to claim 1 or 2, wherein the treatment temperature in the hydrothermal treatment step is 120 to 140 °C.

4. The method for producing a cellulose material according to claim 1 or 2, wherein the treatment time in the hydrothermal treatment step is 20 to 40 minutes.

5. The method for producing a cellulose material according to claim 1 or 2, wherein the treatment temperature in the bleaching hydrothermal treatment step is 120 to 140 °C.

6. The method for producing a cellulose material according to claim 1 or 2, wherein the treatment time in the bleaching hydrothermal treatment step is 20 to 40 minutes.

7. The method for producing a cellulose material according to claim 1, wherein the plant biomass is bamboo or wood.

8. The method for producing a cellulose material according to claim 1 or 2, wherein the produced cellulose material contains 70% by mass or more of cellulose.

9. A method for separating and recovering plant biomass components, comprising an acid hydrothermal treatment biomass component recovery step and an alkaline hydrothermal treatment biomass component recovery step, and separating and recovering plant biomass components from plant biomass. The acid hydrothermal treatment biomass component recovery step comprises subjecting plant biomass or the treated product in the alkaline hydrothermal treatment biomass component recovery step to hydrothermal treatment in an aqueous acid solution to precipitate the insoluble components of the acid hydrothermal treatment biomass, and separating and recovering the insoluble and soluble components of the acid hydrothermal treatment biomass. The alkaline hydrothermal treatment biomass component recovery step comprises subjecting plant biomass or the treated product in the acid hydrothermal treatment biomass component recovery step to hydrothermal treatment in an aqueous alkaline solution containing a bleaching agent to precipitate the insoluble components of the alkaline hydrothermal treatment biomass, and separating and recovering the insoluble and soluble components of the alkaline hydrothermal treatment biomass.

10. The plant biomass is bamboo, the soluble component of the acid hydrothermal-treated biomass in the acid hydrothermal treatment biomass component recovery step is a solution containing a lignin material, the plant biomass to be treated in the alkali hydrothermal treatment biomass component recovery step is the insoluble component of the acid hydrothermal-treated biomass, the insoluble component of the alkali hydrothermal-treated biomass contains a cellulose material, and the soluble component is a solution containing a hemicellulose material. The method for separating and recovering plant biomass components according to claim 9, characterized in that.

11. The plant biomass is wood, the soluble component of the acid hydrothermal-treated biomass in the acid hydrothermal treatment biomass component recovery step is a solution containing a hemicellulose material, the plant biomass to be treated in the alkali hydrothermal treatment biomass component recovery step is the insoluble component of the acid hydrothermal-treated biomass, the insoluble component of the alkali hydrothermal-treated biomass contains a cellulose material, and the soluble component is a solution containing a lignin material. The method for separating and recovering plant biomass components according to claim 9, characterized in that.

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