Solubilization treatment method for biomass raw material, and extract

Abstract

This solubilization treatment method for a biomass raw material includes: a heating and pulverization step for heating and pulverizing a biomass raw material containing an oligosaccharide and lignin; and an extraction step for adding water to a pulverized product obtained in the heating and pulverization step to extract a water-soluble component from the pulverized product. In the heating and pulverization step, a biomass raw material having a water content of 50 mass% or less is heated and pulverized under heating at a temperature of 60°C or higher but lower than 300°C without adding a catalyst.

Description

Solubilization method for biomass raw materials and extracts

[0001] The present disclosure relates to a solubilization method and extract of biomass feedstock.

[0002] In recent years, technology for producing biomass fuel from non-food biomass (cellulosic biomass) such as wood, grass, and rice straw has been attracting attention as an alternative to food biomass such as sugarcane and corn.

[0003] Patent Document 1 describes a method for producing biomass fuel in which a biomass raw material containing cellulose is pulverized under heating at a temperature of 100° C. or higher but lower than 300° C., and water-soluble components are extracted with water.

[0004] JP 2013-111034 A

[0005] Cellulosic biomass raw materials contain hemicellulose, oligosaccharides, and lignin in addition to cellulose. Patent Document 1 describes a method for solubilizing cellulose, but does not describe a method for solubilizing hemicellulose or lignin. Because hemicellulose and lignin have different structures from cellulose, it was difficult to apply the above-mentioned solubilization methods.

[0006] Therefore, there is a demand for a method for solubilizing biomass materials containing oligosaccharides and lignin.

[0007] The solubilization treatment method for biomass raw materials according to the present disclosure comprises a heating and grinding step of heating and grinding a biomass raw material containing oligosaccharides and lignin, and an extraction step of adding water to the ground product obtained in the heating and grinding step and extracting water-soluble components from the ground product. The heating and grinding step is characterized in that the biomass raw material, which has a moisture content of 50% by mass or less, is heated and ground at a temperature of 60°C or higher but lower than 300°C without the addition of a catalyst.

[0008] It is known that when biomass raw materials containing cellulose, hemicellulose, lignin, etc. are heated and crushed, the polymers such as cellulose are decomposed into smaller molecules and become water-soluble. However, in a solubilized solution in which such small molecules are dissolved in water, a precipitate forms upon heating. Because the precipitate is a water-insoluble component, if such a precipitate forms during the heat-crushing process, it cannot be recovered as a water-soluble component (extract) in the subsequent extraction process. Furthermore, this precipitate is thought to be the result of a reaction between the water contained in the biomass raw material and the decomposed cellulose, lignin, etc.

[0009] Therefore, according to the present invention, by heating and grinding biomass raw materials with a moisture content of 50% by mass or less, the formation of precipitates can be suppressed, and components that cannot be recovered as water-soluble components using conventional heating and grinding processes can be recovered as water-soluble components. This improves the yield of water-soluble components. Furthermore, because heating and grinding is performed at a relatively low temperature of 60°C or higher but lower than 300°C without adding a catalyst, the manufacturing process is safe and production costs can be reduced. Therefore, water-soluble components can be efficiently obtained from biomass raw materials containing hemicellulose, oligosaccharides, and lignin.

[0010] 1 is a process block diagram of a solubilization treatment of a biomass raw material. 2 is a graph showing the solubilization rate according to an example.

[0011] Hereinafter, embodiments of the solubilization method for biomass feedstock according to the present disclosure will be described with reference to the drawings. Note that the embodiments described below are examples for explaining the present disclosure and are not intended to limit the present disclosure to these embodiments. Therefore, the present disclosure can be implemented in various forms without departing from the spirit and scope of the present disclosure.

[0012] The solubilization method for biomass feedstock according to the present disclosure will be described with reference to FIG. 1 . The biomass feedstock according to the present disclosure comprises a biomass feedstock containing cellulose, oligosaccharides, and lignin. Examples of such biomass feedstocks include grass or plant biomass such as rice straw, wheat straw, and bagasse; thinning materials such as bamboo and bamboo grass; wood processing waste such as sawdust, chips, and scraps; woody biomass such as roadside tree pruning materials, wooden construction waste, bark, and driftwood; and cellulose products such as waste paper. Sludge, livestock manure, agricultural waste, and urban waste can also be used as long as they contain cellulose, lignin, oligosaccharides, and other elements sufficient to be used as biomass feedstocks. These biomass feedstocks may be used alone or in combination with multiple different types. For example, in addition to lignin and oligosaccharides, they may also contain polysaccharides such as starch, hemicellulose, and pectin.

[0013] The biomass raw material may be coarsely pulverized to about 1 mm to 100 mm in a coarse pulverization step before being heated and pulverized in the heating and pulverization step 1. Coarse pulverization allows the biomass raw material to be formed into a shape that is easy to handle. In the coarse pulverization step, a pulverization method can be selected depending on the form of the biomass raw material, and for example, a general-purpose pulverizer such as a hammer mill, cutter mill, vibration mill, ball mill, rod mill, roller mill, colloid mill, disk mill, or jet mill can be used. Furthermore, the pulverization treatment in the coarse pulverization step can be either a dry or wet method, but dry pulverization is preferable in terms of reducing the crystallinity of cellulose.

[0014] Furthermore, the biomass raw material may be dried in a drying step before being heated and pulverized in the heating and pulverization step 1. Whether or not to perform the drying step may be determined by measuring the moisture content of the biomass raw material and determining the moisture content. The moisture content of the biomass raw material in the heating and pulverization step 1 is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 10% by mass or less. Therefore, the biomass raw material may be dried in the drying step so that the moisture content of the biomass raw material in the heating and pulverization step 1 reaches the above-mentioned value. The drying step may be performed by natural drying, or by heating the biomass raw material with hot air drying or an electric heater, etc. Note that the coarse pulverization step may be performed after the moisture content of the biomass raw material is reduced to the above-mentioned value or less. By performing dry pulverization on biomass raw material with a low moisture content, the crystallinity of cellulose and lignin can be efficiently reduced.

[0015] The biomass raw material that has been coarsely pulverized in the coarse pulverization step or whose moisture content has been adjusted in the drying step is heated and pulverized in the heating and pulverization step 1. In the heating and pulverization step 1, the heating and pulverization treatment is carried out at a temperature of 60°C or higher but lower than 300°C. There are no particular limitations on the heating method for the biomass raw material, and the container can be heated using an electric heater, high frequency, microwaves, steam, or the like. The pulverization may also be carried out using a ball mill such as a planetary ball mill. When a ball mill is used, the biomass raw material is subjected to a pulverization force from the balls, which can significantly increase the mechanochemical effect of pulverization.

[0016] In the heating and grinding step 1, the decomposition of the biomass raw material can be accelerated by obtaining a mechanochemical effect through heating and grinding. That is, after the biomass raw material is decomposed into components such as cellulose, hemicellulose, and lignin, the frictional heat generated by the ball mill is thought to activate the molecular motion of the cellulose, etc., accelerating the reduction in crystallinity and the breakdown of the biomass raw material into smaller molecules.

[0017] The heating and grinding step 1 is preferably carried out while removing moisture generated during the heating and grinding step 1. The removal of water may be carried out by placing a moisture adsorbent such as a dehumidifier in the ball mill, or by cooling a portion of the ball mill to remove moisture as water droplets. The atmosphere during the heating and grinding step 1 may be atmospheric pressure or any atmosphere selected from the group consisting of oxygen, nitrogen, argon, and rare gases. However, from the viewpoint of removing moisture, it is preferable to connect a vacuum pump to the grinding container and carry out the heating and grinding step under negative pressure or vacuum. Specifically, the pressure within the ball mill may be 0.01 MPa or less, preferably 1 kPa or less. This allows the water generated during the heating and grinding step 1 to be sucked out of the grinding container by the vacuum pump, thereby removing the moisture.

[0018] When water is generated in the heating and grinding step 1, water-soluble components of the low-molecular-weight biomass raw material dissolve in water, producing a solubilized solution. When the solubilized solution produced in this way is heated, a water-insoluble precipitate is produced. Here, "insoluble" refers to components that are not extracted as an aqueous solution when the precipitate is washed with water. This precipitate is thought to be produced by the reaction of low-molecular-weight cellulose, lignin, etc. with water. Therefore, by removing the water generated in the heating and grinding step 1, the generation of precipitates in the heating and grinding step 1 can be suppressed, and components that cannot be recovered as water-soluble components in a normal heating and grinding process can be recovered as water-soluble components. This makes it possible to improve the yield of water-soluble components (extracts).

[0019] Furthermore, by performing the heating and grinding step 1 under negative pressure or vacuum, it is possible to reduce the heating temperature. This is because the saturated vapor pressure of water is low under vacuum, and water evaporates at a low temperature. This allows the heating temperature in the heating and grinding step 1 to be set low, thereby reducing the production cost.

[0020] It is also possible to suppress the generation of water in the heating and grinding step 1 by reducing the moisture content of the biomass raw material to be heated and ground in the heating and grinding step 1. This suppresses the generation of precipitates, and makes it possible to recover as water-soluble components components that cannot be recovered as water-soluble components in a normal heating and grinding process. This makes it possible to improve the yield of water-soluble components.

[0021] The rotation speed in the heating and grinding step 1 is preferably in the range of 200 rpm to 2000 rpm. The higher the rotation speed, the more easily carbonization progresses, but a rotation speed of more than 300 rpm and less than 1500 rpm is preferred in terms of balancing production energy and equipment load. The ball diameter and ball weight can be set to any value, but in order to grind the biomass raw material to 10 mm or less, if the vessel capacity of the ball mill is 2 L, it is recommended to set them to 1 mmφ to 30 mmφ and 1 kg to 8 kg.

[0022] The heating and grinding process is preferably carried out for 10 minutes or more. Since the longer the processing time, the faster the reaction of depolymerization progresses, a long processing time is desirable; however, in order to efficiently obtain water-soluble components, processing for approximately 10 minutes to 2 hours is preferable. As described above, by obtaining the mechanochemical effect, solubilization processing of biomass raw materials containing hemicellulose, lignin, etc. can be carried out at low temperatures and in a short time. Furthermore, since no solvents or catalysts are used in the heating and grinding process 1, the process is safe and production costs can be reduced.

[0023] Subsequently, in extraction step 2, water-soluble components are extracted from the pulverized product that has been heated and pulverized in heating and pulverization step 1. In extraction step 2, it is desirable to add and mix water in an amount 0.1 to 500 times the amount of water as the pulverized product obtained in heating and pulverization step 1, and then perform solid-liquid separation in a solid-liquid separator to obtain water-soluble components (extract) and a residue. Examples of solid-liquid separators include devices that use gravity sedimentation, centrifugation, membrane separation, coagulation separation, flotation separation, etc.

[0024] The solubilized solution obtained in extraction step 2 may be subjected to total organic carbon measurement, sugar component analysis, NMR, GC-MS, etc., to identify its components. Alternatively, the solubilization rate may be determined from the total organic carbon measurement. The solubilization rate is the ratio of the amount of carbon contained in the solubilized solution to the amount of carbon contained in sugars such as cellulose, hemicellulose, and oligosaccharides contained in the biomass feedstock (amount of water-soluble organic carbon / amount of carbon contained in the sugars contained in the feedstock). A solubilization rate of more than 100% means that components other than sugars contained in the biomass feedstock have been extracted as water-soluble components. Therefore, in this case, it is estimated that in addition to monosaccharides or polysaccharides derived from sugars such as cellulose, lignin, a component other than sugars, is contained in the water-soluble components.

[0025] The solubilized solution may be mixed with a solid acid catalyst and stirred to hydrolyze it, producing a saccharified solution containing monosaccharides such as glucose as the main component. The saccharified solution thus obtained can be fermented or distilled to produce ethanol, a biomass fuel. Furthermore, the lignin contained in the solubilized solution may be chemically modified and used as a plastic material.

[0026] According to the present disclosure, biomass raw materials containing oligosaccharides and lignin can be solubilized at low temperature in a short time by undergoing the heating and crushing step 1 and the extraction step 2. Furthermore, according to the present disclosure, biomass raw materials can be solubilized by a simple method without using a solvent or catalyst, which reduces the production energy required and makes the process safe.

[0027] Examples Examples of the present disclosure will be described below, but the present disclosure is not limited to the descriptions of these examples.

[0028] In the following examples, the solubilized solution was evaluated using the solubilization rate, which was determined by measuring the sugar content of the biomass raw material calculated by constituent sugar analysis and the total organic carbon content of the solubilized solution using a TOC (total organic carbon) meter as the amount of water-soluble organic carbon.

[0029] Example 1: 25 g of sorghum, a grass plant containing cellulose, hemicellulose, oligosaccharides, and lignin, was used as the biomass raw material. A drying step was performed before the heating and grinding step 1 to reduce the moisture content to 3%, and then heating and grinding was performed using a heater-equipped ball mill (ball 5 mmφ, 7.5 kg) at 120°C, 700 rpm, and under vacuum. Heating and grinding was performed for 30 minutes and 1 hour in the heating and grinding step 1. Each of the resulting ground products was mixed with 10 times the amount of water, and the mixture was subjected to solid-liquid separation using a solid-liquid separator to obtain a solubilized solution.

[0030] Figure 2 is a graph plotting the solubilization rate versus heating and grinding time. Because heating and grinding began when the heating temperature reached 120°C, the heating and grinding time was set to 0 when the temperature increase ended (when the heating temperature reached 120°C). As shown in Figure 2, the solubilization rate in Example 1 was 77% when the heating and grinding time was 30 minutes, and 132% when the heating and grinding time was 1 hour. It is believed that the solubilization rate exceeded 100% after the solubilization treatment because not only the sugars contained in cellulose, etc., but also lignin, a component other than sugar, was solubilized.

[0031] Example 2 A solubilized solution was obtained in the same manner as in Example 1, except that the drying step was not performed. The water content of the biomass raw material heated and pulverized in the heating and pulverization step 1 was 4 to 10%. The solubilization rate in Example 2 was 107% when the heating and pulverization time was 30 minutes, 113% when the heating and pulverization time was 1 hour and 15 minutes, 116% when the heating and pulverization time was 1 hour and 30 minutes, and 73% when the heating and pulverization time was 1 hour and 45 minutes.

[0032] (Example 3) A solubilized solution was obtained in the same manner as in Example 1, except that the heating and grinding step 1 was carried out under normal pressure, i.e., atmospheric pressure. The solubilization rate in Example 3 was 74% when the heating and grinding time was 30 minutes, and 115% when the heating and grinding time was 1 hour.

[0033] Example 4 A solubilized solution was obtained in the same manner as in Example 1, except that the drying step was not performed and heating and grinding step 1 was performed under normal pressure, i.e., atmospheric pressure. The water content of the biomass raw material heated and ground in heating and grinding step 1 was 4 to 10%. The solubilization rate in Example 4 was 61% when the heating and grinding time was 30 minutes, 93% when the heating and grinding time was 1 hour, 99% when the heating and grinding time was 1 hour and 15 minutes, and 79% when the heating and grinding time was 1 hour and 30 minutes.

[0034] When the heating and grinding time was 30 minutes, the solubilized solution obtained under the conditions of Example 2 showed the highest solubilization rate. On the other hand, it was found that in Example 2, the production rate of water-soluble components decreased when the heating and grinding time exceeded 30 minutes, and the solubilization rate decreased when the heating and grinding time exceeded 1 hour and 30 minutes. In Example 4, the solubilization rate did not exceed 100% even when the heating and grinding time was increased, and the solubilization rate decreased when the heating and grinding time exceeded 1 hour and 15 minutes.

[0035] In Examples 1 and 3, the solubilization rate was highest when the heating and grinding time was 1 hour. Furthermore, the rate of production of water-soluble components did not change significantly even when the heating and grinding time exceeded 30 minutes. In particular, the solubilization rate was the highest at 130% when the heating and grinding time was 1 hour in Example 1, suggesting that lignin, a component other than sugar, was extracted as a water-soluble component. Furthermore, when the solubilization rate exceeded 100%, it was suggested that oligosaccharides, which are sugars contained in the biomass raw material, were also extracted as water-soluble components.

[0036] These results demonstrate that the lower the moisture content of biomass raw materials, the shorter the time required for processing to maximize the solubilization rate. Furthermore, it was found that the rate of production of water-soluble components can be increased by performing the heating and grinding process while removing moisture. Furthermore, in Examples 1 to 3, the solubilization rate exceeded 100% by adjusting the heating and grinding time, suggesting that lignin, a component other than sugar, was extracted as a water-soluble component.

[0037] The above-described embodiment may include the following configurations: (1) A method for solubilizing a biomass raw material, comprising: a heating and grinding step 1 in which a biomass raw material containing oligosaccharides and lignin is heated and ground; and an extraction step 2 in which water is added to the ground product obtained in the heating and grinding step 1 and water-soluble components are extracted from the ground product, wherein the heating and grinding step 1 involves heating and grinding a biomass raw material having a moisture content of 50% by mass or less at a temperature of 60°C or higher but lower than 300°C without adding a catalyst.

[0038] It is known that when biomass raw materials containing cellulose, hemicellulose, oligosaccharides, lignin, etc. are heated and crushed, the polymers such as cellulose are degraded and become water-soluble. However, in a solubilized solution in which such low-molecular-weight compounds are dissolved in water, a precipitate forms upon heating. Since the precipitate is an unnecessary component in water, if such a precipitate forms in the heat-crushing step 1, it cannot be recovered as a water-soluble component (extract) in the subsequent extraction step 2. Furthermore, this precipitate is thought to be the result of a reaction between the water contained in the biomass raw material and the degraded cellulose, lignin, etc.

[0039] Therefore, according to the present invention, by heating and grinding biomass raw materials with a moisture content of 50% by mass or less, the formation of precipitates can be suppressed, and components that cannot be recovered as water-soluble components using conventional heating and grinding processes can be recovered as water-soluble components. This improves the yield of water-soluble components. Furthermore, because heating and grinding is performed at a relatively low temperature of 60°C or higher but lower than 300°C without adding a catalyst, the manufacturing process is safe and production costs can be reduced. Therefore, water-soluble components can be efficiently obtained from biomass raw materials containing hemicellulose, oligosaccharides, and lignin.

[0040] (2) In the method for solubilizing a biomass raw material described in (1), the heating and pulverizing step 1 preferably involves heating and pulverizing a biomass raw material having a moisture content of 10% by mass or less.

[0041] According to this configuration, since the moisture content of the biomass raw material is 10% by mass or less, it is possible to further suppress the formation of precipitates, and as a result, it is possible to obtain a saccharified solution that can be used as biomass fuel with high yield.

[0042] (3) In the carbon compound material of (1) or (2), the heating and pulverizing step 1 is preferably carried out while removing water generated in the heating and pulverizing step 1.

[0043] According to this configuration, since the heating and grinding step 1 can be performed in the absence of water, the formation of precipitates can be suppressed. Therefore, by solubilizing the biomass raw material after heating and grinding in water, the water-soluble components can be obtained in good yield.

[0044] (4) In the carbon compound material of (3), the heating and crushing step 1 is preferably carried out under vacuum.

[0045] According to this configuration, by performing the heating and grinding step 1 under vacuum, it is possible to remove the water generated during the heating and grinding step 1. This suppresses the formation of precipitates and improves the yield of water-soluble components. Furthermore, by performing the heating and grinding step 1 under vacuum, the saturated water vapor pressure of water is lowered, allowing water to evaporate at a low temperature, allowing the heating temperature to be lowered. As a result, it is also possible to reduce the cost of solubilizing the biomass raw material.

[0046] (5) An extract having a solubilization rate in water of more than 100%, extracted by the solubilization treatment method for biomass raw materials according to any one of (1) to (4).

[0047] The solubilization rate refers to the ratio of the carbon content of the water-soluble components to the carbon content of the sugars contained in the biomass feedstock. According to this configuration, not only the sugars contained in cellulose, etc. but also the components contained in lignin can be converted into water-soluble components, so the water solubilization rate can be made to exceed 100%.

[0048] The present disclosure is applicable to a solubilization method and extract of biomass materials containing oligosaccharides and lignin.

[0049] 1: Heating and grinding process, 2: Extraction process

Claims

1. A method for solubilizing a biomass raw material, comprising: a heating and grinding step of heating and grinding a biomass raw material containing oligosaccharides and lignin; and an extraction step of adding water to the ground material obtained in the heating and grinding step and extracting water-soluble components from the ground material, wherein the heating and grinding step heats and grinds the biomass raw material, which has a moisture content of 50% by mass or less, at a temperature of 60°C or higher but lower than 300°C without adding a catalyst.

2. The solubilization method for biomass raw materials according to claim 1, wherein the heating and grinding step heats and grinds the biomass raw materials having a moisture content of 10% by mass or less.

3. The method for solubilizing biomass raw materials according to claim 1, wherein the heating and pulverizing step is carried out while removing water generated during the heating and pulverizing step.

4. The method for solubilizing biomass raw materials according to claim 3, wherein the heating and crushing step is carried out under vacuum.

5. An extract having a solubilization rate in water of more than 100%, extracted by the solubilization treatment method for biomass raw materials according to any one of claims 1 to 4.

Images