JP2009291143A - Method for saccharifying and separating vegetable fiber material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the recovery of cluster acid of a cellulose hydrolysis catalyst to provide a highly pure sugar aqueous solution. <P>SOLUTION: Provided is a method for saccharifying and separating the vegetable fiber material, characterized by having a hydrolysis process for hydrolyzing cellulose contained in the vegetable fiber material with a cluster acid catalyst, the first solid-liquid separation process for separating into an organic solvent solution containing the cluster acid catalyst and a solid content containing sugars and cluster acid catalyst residues through a process for mixing a mixture containing the cluster acid catalyst and the sugars produced in the hydrolysis process with the first organic solvent, the second solid-liquid separation process for mixing water with the solid content obtained in the first solid-liquid separation process or a solid content after the elusion of the cluster acid catalyst obtained in a compression process, and then separating the vegetable fiber residues from the aqueous solution, and a compression process for impregnating the solid content obtained in the first solid-liquid separation process or the vegetable fiber residues obtained in the second solid-liquid separation process with the second organic solvent, and then compressing the product. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing sugar by saccharification and separation of plant fiber materials.

Decompose plant fibers that are biomass, such as sugarcane residue (bagasse) and wood fragments, to produce sugars, mainly glucose and xylose, from cellulose and hemicellulose, and use the resulting sugars as food or fuel It has been proposed and put into practical use. In particular, a technique for fermenting sugars obtained by decomposing plant fibers and generating alcohol such as ethanol as fuel has attracted attention.
Conventionally, various methods for decomposing cellulose or hemicellulose to produce sugars such as glucose have been proposed. As a general method, cellulose is hydrolyzed using sulfuric acid such as dilute sulfuric acid or concentrated sulfuric acid, or hydrochloric acid. The method (patent document 1) is mentioned.
JP-A-8-299000

  However, the method of decomposing cellulose using an acid such as sulfuric acid has a problem that it is difficult to separate the acid and the sugar. This is because glucose and acid, which are the main components of the decomposition product, are both water-soluble. Acid removal by neutralization or ion exchange is not only labor and costly, but it is difficult to completely remove the acid, and the acid often remains in the ethanol fermentation process. As a result, even in the ethanol fermentation process, even when the pH is adjusted to the optimum pH for the yeast activity, the yeast activity decreases due to the increase in the salt concentration, resulting in a decrease in fermentation efficiency.

In particular, when concentrated sulfuric acid is used, it is very difficult to remove the sulfuric acid to such an extent that the yeast is not inactivated, and a great deal of energy is required. In contrast, when dilute sulfuric acid is used, sulfuric acid can be removed relatively easily, but cellulose must be decomposed under high temperature conditions, and energy is required.
Furthermore, acids such as sulfuric acid and hydrochloric acid are very difficult to separate, recover and reuse. Therefore, using these acids as a catalyst for producing glucose is one of the causes for raising the cost of bioethanol.

As a result of intensive studies on the saccharification of cellulose, the present inventors have found that the cluster acid in a pseudo-molten state has excellent catalytic activity for hydrolysis of cellulose and can be easily separated from the produced sugar. The patent application has already been filed (Japanese Patent Application No. 2007-115407). According to this method, unlike the conventional concentrated sulfuric acid method or dilute sulfuric acid method, it is possible to recover and reuse the hydrolysis catalyst, and from the hydrolysis of cellulose to the recovery of aqueous sugar solution and the recovery of hydrolysis catalyst. The energy efficiency of the process can be improved.
The above patent application also proposes a method for separating a saccharide produced by hydrolysis of a plant fiber material and a cluster acid catalyst. Specifically, after hydrolysis, the cluster acid is dissolved by adding an organic solvent to the reaction mixture containing the generated saccharide, the cluster acid catalyst, and the residue. A method of separating from a cluster acid organic solvent is described.

  The present inventors have further studied on the saccharification of cellulose using the cluster acid catalyst, and succeeded in obtaining a high-purity aqueous sugar solution by improving the separation between the produced sugar and the cluster acid catalyst. That is, the present invention has been accomplished through the above-described research, and aims to increase the recovery rate of cluster acid, which is a hydrolysis catalyst for cellulose, and to provide a high-purity sugar aqueous solution. is there.

  The saccharification / separation method for plant fiber material of the present invention includes a hydrolysis step of hydrolyzing cellulose contained in the plant fiber material using a cluster acid catalyst to produce a sugar mainly composed of glucose, Through a process of mixing the saccharide produced in the hydrolysis step and the mixture containing the cluster acid catalyst with a first organic solvent that is a poor solvent for the saccharide and a good solvent for the cluster acid catalyst. The first solid-liquid separation step for separating the organic solvent solution containing the cluster acid catalyst into the solid content containing the sugar and cluster acid catalyst residue, and the solid obtained in the first solid-liquid separation step Or a second solid-liquid separation step for separating the solid content after elution of the cluster acid catalyst obtained in the pressing step, which is a subsequent step, with water, and then separating into a plant fiber residue and an aqueous solution, The solid content obtained in the first solid-liquid separation step or the plant fiber residue obtained in the second solid-liquid separation step is a poor solvent for sugar and good for the cluster acid catalyst. It is characterized by having a pressing step of eluting the cluster acid catalyst remaining in the solids or the pores in the plant fiber residue by squeezing after impregnating the second organic solvent as a solvent. To do.

  In the method for saccharification and separation of plant fiber material having such a structure, in the pressing step, the cluster acid catalyst is eluted by eluting the cluster acid catalyst remaining in the solids or the pores in the plant fiber residue. The recovery rate can be improved. Moreover, since the saccharification separation method of the plant fiber material of this invention can reduce the residual amount of the said cluster acid catalyst in saccharide | sugar as much as possible, saccharide | sugar with high purity can be obtained.

  In the method for saccharification and separation of plant fiber material of the present invention, the hydrolysis step is preferably carried out at 140 ° C. or lower under conditions of normal pressure to 1 MPa.

  The saccharification / separation method of the plant fiber material having such a configuration can be performed under relatively mild reaction conditions, and saccharification / separation excellent in energy efficiency can be achieved.

  In the method for saccharification and separation of plant fiber material of the present invention, the cluster acid catalyst is preferably a heteropolyacid.

  The saccharification / separation method of the plant fiber material having such a configuration can achieve reliable hydrolysis of cellulose in the hydrolysis step by using a heteropolyacid having strong oxidizing power and acid strength.

  In the saccharification / separation method for a plant fiber material of the present invention, the solubility of the sugar in the first organic solvent is preferably 1 g / 100 ml or less in the first solid-liquid separation step.

  In the saccharification / separation method of the plant fiber material having such a configuration, in the first solid-liquid separation step, there is a sufficient difference between the solubility of the sugar in the first organic solvent and the solubility of the cluster acid catalyst. By separating the cluster acid catalyst from the saccharide as much as possible, the solid content containing a high-purity saccharide can be obtained.

  In the method for saccharification and separation of plant fiber material of the present invention, it is preferable to use at least one selected from ethers and alcohols as the first organic solvent in the first solid-liquid separation step.

  In the saccharification / separation method of the plant fiber material having such a structure, in the first solid-liquid separation step, ethers which are a poor solvent for the sugar and a good solvent for the cluster acid catalyst In addition, by using at least one of alcohol and the alcohol as the first organic solvent, the cluster acid catalyst can be separated from the sugar as much as possible to obtain the solid component containing high-purity sugar.

  In the method for saccharification and separation of plant fiber materials of the present invention, it is preferable that alcohols are used as the second organic solvent in the pressing step.

  In the saccharification / separation method of the plant fiber material having such a configuration, the cluster acid catalyst can be eluted from the solid material or the plant fiber residue as much as possible in the pressing step.

  According to the present invention, in the pressing step, the recovery of the cluster acid catalyst can be improved by eluting the cluster acid catalyst remaining in the pores in the solid content or the plant fiber residue. . In addition, according to the present invention, since the residual amount of the cluster acid catalyst in the sugar can be reduced as much as possible, a highly pure sugar can be obtained.

  The saccharification / separation method for plant fiber material of the present invention includes a hydrolysis step of hydrolyzing cellulose contained in the plant fiber material using a cluster acid catalyst to produce a sugar mainly composed of glucose, Through a process of mixing the saccharide produced in the hydrolysis step and the mixture containing the cluster acid catalyst with a first organic solvent that is a poor solvent for the saccharide and a good solvent for the cluster acid catalyst. The first solid-liquid separation step for separating the organic solvent solution containing the cluster acid catalyst into the solid content containing the sugar and cluster acid catalyst residue, and the solid obtained in the first solid-liquid separation step Or a second solid-liquid separation step for separating the solid content after elution of the cluster acid catalyst obtained in the pressing step, which is a subsequent step, with water, and then separating into a plant fiber residue and an aqueous solution, The solid content obtained in the first solid-liquid separation step or the plant fiber residue obtained in the second solid-liquid separation step is a poor solvent for sugar and good for the cluster acid catalyst. It is characterized by having a pressing step of eluting the cluster acid catalyst remaining in the solids or the pores in the plant fiber residue by squeezing after impregnating the second organic solvent as a solvent. To do.

In the above-mentioned patent application (Japanese Patent Application No. 2007-115407), the inventors of the present invention have both a water-soluble saccharide mainly composed of glucose and a cluster acid, but a cluster acid in an organic solvent in which the saccharide is hardly soluble or insoluble. Have been found to be soluble, and by utilizing this difference in solubility properties, it has been reported that cluster acids and sugars can be separated. That is, after hydrolyzing a plant fiber material using a cluster acid catalyst, a hydrolysis mixture (hereinafter simply referred to as a hydrolysis mixture) containing residues such as sugar, cluster acid catalyst, and unreacted cellulose as a product. When the specific organic solvent is added, the cluster acid catalyst is dissolved in the organic solvent. On the other hand, since sugar does not dissolve in the organic solvent, the sugar present in the solid state in the hydrolysis mixture does not dissolve in the organic solvent and can be separated from the cluster acid organic solvent solution by a solid-liquid separation method such as filtration. it can.
As a result of further intensive studies, the present inventors have found that the saccharide produced in the hydrolysis step precipitates and crystal grows, or when the cluster acid catalyst agglomerates with other precipitated saccharides. It was found that.

  Then, the cluster acid catalyst remains in the pores in the plant fiber residue obtained after the hydrolysis step, and the remaining cluster acid catalyst is impregnated with an organic solvent and then squeezed to be eluted. Thus, it has been found that the recovery rate of the cluster acid catalyst can be improved.

First, a hydrolysis process in which cellulose contained in a plant fiber material is hydrolyzed to produce a sugar mainly composed of glucose will be described.
Although the description here mainly focuses on the process of producing glucose from cellulose, the plant fiber material contains hemicellulose in addition to cellulose, and the product is not limited to glucose but other simple substances such as xylose. There are sugars, and these cases are also included in the scope of the present invention.
The plant-based fiber material is not particularly limited as long as it contains cellulose or hemicellulose. A cellulosic biomass is mentioned. Further, cellulose or hemicellulose separated from the biomass, or artificially synthesized cellulose or hemicellulose itself may be used.

  These fiber materials are usually used in the form of powder from the viewpoint of dispersibility in the reaction system. As a method for forming a powder, a general method may be used. From the viewpoint of mixing with the cluster acid catalyst and improving the reaction opportunity, it is preferable to form a powder having a diameter of several μm to 200 μm.

Moreover, the fiber material may dissolve the lignin contained by performing a cooking process beforehand as needed. By dissolving and removing lignin, it is possible to improve the chance of contact between the cluster acid catalyst and cellulose in the hydrolysis step, and at the same time, the amount of residue contained in the hydrolysis reaction mixture can be reduced. It is possible to suppress a decrease in sugar yield and a decrease in cluster acid recovery rate due to mixing of the generated sugar and cluster acid. When cooking is performed, the degree of pulverization of the plant fiber material can be made relatively small (the pulverization is rough), so that the labor, cost and energy for making the fiber material into powder can be reduced. is there.
Examples of the cooking process include alkalis and salts such as NaOH, KOH, Ca (OH) ₂ , Na ₂ SO ₃ , NaHCO ₃ , NaHSO ₃ , Mg (HSO ₃ ) ₂ , Ca (HSO ₃ ) _2, and aqueous solutions thereof. and what was further mixed SO ₂ solution, a gas such as NH _3, and a method of contacting the plant fiber material chips (number cm~ number mm). Specific conditions include a reaction temperature of 120 to 160 ° C. and a reaction time of several tens of minutes to about 1 hour.

  In the present invention, the cluster acid used as a catalyst for hydrolysis of plant fiber materials is a condensed product of a plurality of oxo acids, that is, a so-called polyacid. Many polyacids are often oxidized to the maximum oxidation number because the central element is bonded to multiple oxygen atoms, exhibit excellent properties as oxidation catalysts, and are known to be strong acids. It has been. For example, the acid strength (pKa = −13.16) of phosphotungstic acid that is a heteropolyacid is stronger than the acid strength (pKa = −11.93) of sulfuric acid. That is, for example, even under mild conditions such as 50 ° C., cellulose and hemicellulose can be decomposed into monosaccharides such as glucose and xylose.

  The cluster acid used in the present invention may be an isopolyacid or a heteropolyacid, but a heteropolyacid is preferred because of its strong oxidizing power and acid strength. The heteropolyacid is not particularly limited, and HwAxByOz (A: heteroatom, B: polyatom serving as a skeleton of polyacid, A: heteroatom, w: composition ratio of hydrogen atom, x: composition ratio of heteroatom, y: And those represented by the general formula of (composition ratio of poly atoms, z: composition ratio of oxygen atoms). Examples of the poly atom B include atoms such as W, Mo, V, and Nb that can form a polyacid. Examples of the hetero atom A include atoms such as P, Si, Ge, As, and B that can form a heteropolyacid. One or more polyatoms and heteroatoms may be contained in one heteropolyacid molecule.

From the balance between the strength of the acid strength and the oxidizing power, phosphotungstic acid H ₃ [PW ₁₂ O ₄₀ ] and silicotungstic acid H ₄ [SiW ₁₂ O ₄₀ ], which are tungstates, are preferable. Next, phosphomolybdic acid H ₃ [PMo ₁₂ O ₄₀ ], which is a molybdate, can be preferably used.

Here, Keggin: shows ^{_{[X n + M 12 O 40}} X = P, Si, Ge, As , etc., M = Mo, W, etc.] The structure of heteropoly acid (phosphotungstic acid) in Figure 1. A tetrahedron XO ₄ exists in the center of a polyhedron composed of ₆ units of octahedron MO, and has a lot of crystal water around the structure. The structure of the cluster acid is not particularly limited, and may be, for example, a Dawson type other than the Keggin type.
Here, water that is hydrated or coordinated with a clustered cluster acid catalyst composed of a crystalline cluster acid catalyst and a clustered acid catalyst of several molecules is referred to as “crystal water” that is generally used. Use terms instead. This crystal water contains anion water hydrogen-bonded to the anion constituting the cluster acid catalyst, coordinated water coordinated to the cation, lattice water not coordinated to the cation and anion, and OH group. Is also included.
The clustered cluster acid catalyst is an aggregate composed of several molecules (about 1 to several molecules) of cluster acid, and is different from a crystal. A cluster state can be obtained even in a solid state, a pseudo-molten state, or a state dissolved (colloidal) in a solvent.

  The cluster acid catalyst as described above is in a solid state at room temperature, but when heated and the temperature rises, it becomes a pseudo-molten state. Here, the pseudo-molten state is apparently melted, but is not a completely melted liquid state, but a state close to a colloid (sol) in which cluster acids are dispersed in the liquid, This is a state showing fluidity. Whether or not the cluster acid is in a pseudo-molten state can be confirmed by visual observation, or in the case of a homogeneous system, can also be confirmed by a DTG (differential scanning calorimeter) or the like.

  As described above, the cluster acid exhibits high catalytic activity for the hydrolysis reaction of cellulose even at a low temperature because of its strong acid strength. Moreover, since the diameter of a cluster acid is about 2 nm in diameter, it is excellent in mixing property with the plant fiber material which is a raw material, and can promote the hydrolysis of cellulose efficiently. Accordingly, cellulose can be hydrolyzed under mild conditions, energy efficiency is high, and environmental load is small. Furthermore, unlike the conventional cellulose hydrolysis method using an acid such as sulfuric acid, the method of the present invention using a cluster acid as a catalyst has a high separation efficiency of sugar and catalyst and can be easily separated.

  Moreover, since the cluster acid is in a solid state depending on the temperature, it can be separated from the product saccharide. Therefore, the separated cluster acid can be recovered and reused. Moreover, since the cluster acid catalyst in a pseudo-molten state also functions as a reaction solvent, the amount of the solvent as the reaction solvent can be greatly reduced as compared with the conventional method. This means that it is possible to separate the cluster acid from the product sugar and to improve the efficiency of the recovery of the cluster acid. That is, the present invention using cluster acid as a hydrolysis catalyst for cellulose can be made at low cost and has a small environmental load.

The cluster acid catalyst and the plant fiber material are preferably mixed and stirred in advance before heating. By mixing the cluster acid catalyst to some extent before it becomes a pseudo-molten state, the contact property between the cluster acid and the plant fiber material can be enhanced.
As described above, in the hydrolysis step, the cluster acid catalyst is in a pseudo-molten state and also functions as a reaction solvent. Therefore, in the present invention, the form of the plant fiber material (size, fiber state, etc.), cluster acid Although depending on the mixing ratio and volume ratio of the catalyst and the plant fiber material, water or an organic solvent as a reaction solvent may not be used in the hydrolysis step.

In the hydrolysis step, water for hydrolyzing cellulose is necessary. Specifically, (n-1) water molecules are required to decompose cellulose in which n glucoses are polymerized into n glucoses. Therefore, at least water necessary for hydrolyzing the total amount of cellulose contained in the plant fiber material into glucose is added to the reaction system. Preferably, a minimum amount of water necessary for hydrolyzing the total amount of cellulose charged as a plant fiber material into glucose is added. This is because when excessive water is added, the generated sugar and cluster acid are dissolved in excess water, and the sugar separation step becomes complicated.
On the other hand, when the cluster acid catalyst is used in a pseudo-molten state, the amount of crystal water necessary for the cluster acid catalyst to be in a pseudo-melt state at the reaction temperature and the total amount of cellulose charged are contained in the reaction system. In the absence of the total amount of water required to be hydrolyzed to glucose, the cluster acid catalyst water of crystallization is used for cellulose hydrolysis, the cluster acid catalyst water of crystallization is reduced, and the cluster acid is in a solidified state. turn into. That is, not only does the contact between the cluster acid catalyst and the plant fiber material decrease, but the viscosity of the mixture of the plant fiber material and the cluster acid catalyst increases, making it impossible to sufficiently mix the mixture.

  Therefore, in the hydrolysis step, in order to ensure the catalytic action of the cluster acid catalyst at the reaction temperature and the function as a reaction solvent, that is, to enable the cluster acid catalyst to maintain a pseudo-molten state, The water content is preferably as follows. That is, (a) crystallization water necessary for all of the cluster acid catalyst present in the reaction system to be in a pseudo-molten state at the reaction temperature in the hydrolysis step, and (b) the total amount of cellulose present in the reaction system It is preferable that the total amount of water necessary for hydrolysis into glucose is not less than the total amount. Particularly preferably, the total amount of the above (a) and (b) is added. This is because, by adding excessive water, the produced sugar and cluster acid are dissolved in excess water, and the separation process of sugar and cluster acid becomes complicated.

  In the hydrolysis process, the water in the reaction system is reduced and the amount of water of crystallization of the cluster acid catalyst is reduced, so that the cluster acid catalyst becomes solid and the contact property with the plant fiber material and the mixing property of the reaction system are improved. In the case of a decrease, the above problem can be avoided by raising the hydrolysis temperature so that the cluster acid catalyst is in a pseudo-molten state.

  The temperature conditions in the hydrolysis step may be appropriately determined in consideration of several factors (for example, reaction selectivity, energy efficiency, cellulose reaction rate, etc.), but energy efficiency, cellulose reaction rate, glucose yield From the balance of the rate, it is usually preferably 140 ° C. or lower, and particularly preferably 120 ° C. or lower. Depending on the form of the plant fiber material, a low temperature such as 100 ° C. or less is also possible, and in that case, glucose can be produced with particularly high energy efficiency.

  In addition, the pressure in the hydrolysis step is not particularly limited, but since the catalytic activity of the cluster acid catalyst for the hydrolysis reaction of cellulose is high, it can be efficiently performed even under mild pressure conditions such as atmospheric pressure (atmospheric pressure) to 10 MPa. Cellulose hydrolysis can proceed.

The ratio of the plant fiber material to the cluster acid catalyst varies depending on the properties (for example, size) and type of the plant fiber material to be used, the stirring method and the mixing method in the hydrolysis step, and the like. Therefore, it may be determined appropriately according to the implementation conditions, but it is preferably within the range of cluster acid catalyst: plant fiber material (weight ratio) = 2: 1 to 6: 1, and usually 2: 1. About 4: 1 may be sufficient.
Since the mixture containing the cluster acid catalyst and the plant fiber material in the hydrolysis step has high viscosity, for example, a heating ball mill is advantageous as the stirring method, but a general stirrer may be used.

  The time of the hydrolysis step is not particularly limited, and may be set as appropriate depending on the shape of the plant fiber material to be used, the ratio of the plant fiber material and the cluster acid catalyst, the catalytic ability of the cluster acid catalyst, the reaction temperature, the reaction pressure, and the like. .

  When the temperature of the reaction system is lowered after the hydrolysis is completed, the sugar produced in the hydrolysis process is not dissolved in the hydrolysis mixture containing the residue (unreacted cellulose) and the cluster acid catalyst. As an aqueous sugar solution, when there is no dissolved water, it precipitates and is contained in a solid state. Some of the produced sugars may be contained in the mixture in the form of a sugar aqueous solution and the rest in a solid state. Since the cluster acid catalyst is also water-soluble, the cluster acid catalyst is also dissolved in water depending on the water content of the mixture after the hydrolysis step.

Next, a separation step for separating the sugar (mainly glucose) produced in the hydrolysis step and the cluster acid catalyst will be described. The separation step includes (1) a first solid-liquid separation step in which a mixture containing a saccharide and a cluster acid catalyst and a first organic solvent are mixed to separate a solid component and an organic solvent solution component, 2) The solid content obtained in the first solid-liquid separation step or the solid content obtained after elution of the cluster acid catalyst obtained in the subsequent pressing step is mixed with water and then separated into a plant fiber residue and an aqueous solution. Second solid-liquid separation step (3) The solid component obtained in the first solid-liquid separation step or the vegetable fiber residue obtained in the second solid-liquid separation step is impregnated with the second organic solvent, and then pressed. By doing so, there are at least three steps of the squeezing step for eluting the cluster acid catalyst remaining in the pores in the solid or plant fiber residue.
Of these, (2) the second solid-liquid separation step and (3) the pressing step may be performed first.
Hereinafter, each separation step will be described in order.

The first solid-liquid separation step (1) includes at least a mixture containing the saccharide produced in the hydrolysis step and the cluster acid catalyst, and a poor solvent for the saccharide and a good solvent for the cluster acid catalyst. This is a process of separating into an organic solvent solution containing a cluster acid catalyst and a solid containing a residue of sugar and cluster acid catalyst through a process of mixing a first organic solvent.
When the clustered acid catalyst is mixed into the solidified sugar, the purity of the resulting sugar is decreased and the recovery rate of the clustered acid catalyst is decreased.
Therefore, by adding the first organic solvent in which the sugar is difficult to dissolve and the cluster acid catalyst is easy to dissolve to the mixture containing the sugar and the cluster acid catalyst, most of the cluster acid catalyst added during the hydrolysis is dissolved. It can be separated into a solvent solution and a solid containing the sugar and cluster acid catalyst residue.

In the first solid-liquid separation step, the first organic solvent that dissolves the cluster acid catalyst is a poor solvent for sugar, but a good solvent for the cluster acid catalyst. Although not particularly limited, in order to precipitate the sugar efficiently, the solubility of the sugar in the organic solvent is preferably 1 g / 100 ml or less, particularly preferably 0.06 g / 100 ml or less. At this time, in order to efficiently precipitate only the sugar as a solid component, the solubility of the cluster acid in the organic solvent is preferably 50 g / 100 ml or more, particularly preferably 100 g / 100 ml or more, and more preferably 500 g / 100 ml or more. Most preferred.
Thus, in the first solid-liquid separation step, the cluster acid catalyst is separated from the sugar as much as possible by providing a sufficient difference between the solubility of the sugar in the first organic solvent and the solubility of the cluster acid catalyst. In addition, a solid content containing high-purity sugar can be obtained.

Specific examples of the first organic solvent include alcohols such as ethanol, methanol and n-propanol, and ethers such as diethyl ether and diisopropyl ether. Alcohols and ethers can be preferably used, and ethanol and diethyl ether are particularly preferable. Diethyl ether is one of the most suitable solvents for separating the saccharide and the cluster acid catalyst because saccharides such as glucose are insoluble and the solubility of the cluster acid is high. On the other hand, ethanol is one of the most suitable solvents because sugars such as glucose are hardly soluble and the solubility of the cluster acid catalyst is high. Diethyl ether is advantageous in distillation compared to ethanol, which has the advantage that it is more readily available than diethyl ether and that the solubility of the cluster acid catalyst is very high.
Thus, in the first solid-liquid separation step, by using a poor solvent for sugar and a good solvent for the cluster acid catalyst as the first organic solvent, the cluster acid is converted from the sugar. The catalyst can be separated as much as possible to obtain a solid containing high-purity sugar.

  Since the amount of the first organic solvent used varies depending on the solubility characteristics of the organic solvent in the sugar and the cluster acid catalyst, an appropriate amount may be determined so that the cluster acid can be efficiently recovered.

  The temperature in the first solid-liquid separation step is preferably in the range of room temperature to 60 ° C., although it depends on the boiling point of the first organic solvent. In the first solid-liquid separation step, the aqueous solution is preferably sufficiently stirred and mixed. A specific stirring method is not particularly limited, and a general method may be used. From the viewpoint of the cluster acid recovery efficiency, the stirring method is preferably a stirring method capable of pulverizing solid components such as a ball mill.

  In the first solid-liquid separation step, the organic solvent solution containing the cluster acid catalyst and the solid containing the sugar and cluster acid catalyst residue are separated. Specific separation methods are not particularly limited, and general solid-liquid separation methods such as filtration and decantation can be employed.

FIG. 3 is a diagram showing a typical example of the first solid-liquid separation step of the present invention.
First, the first organic solvent is added to the mixture containing the saccharide produced in the hydrolysis step and the cluster acid catalyst and stirred. The amount of the first organic solvent is not particularly limited as long as the mixture wets the whole, and the temperature is preferably room temperature to 50 ° C. and the stirring time is preferably 10 to 30 minutes.
Next, it is separated by filtration into a solid content (filtrate) and a filtrate. In the filtrate at this time, it is considered that most of the cluster acid catalyst added at the time of hydrolysis is dissolved. Therefore, the cluster acid catalyst can be regenerated by drying under reduced pressure and removing the solvent.
Subsequently, the first organic solvent is added again to the solid obtained by the first filtration and stirred. The amount of solvent, the stirring temperature and the stirring time at this time are preferably the same as in the first time. The filtrate obtained by the second filtration is used for the separation of the cluster acid catalyst from the next time, together with other mixtures. However, the cluster acid catalyst may be regenerated by mixing with the filtrate obtained by the first filtration.
Furthermore, the first organic solvent is added again to the solid content obtained by the second filtration and stirred. It is preferable to use a new organic solvent because the cluster acid catalyst concentration decreases as the filtration is repeated. The amount of solvent, the stirring temperature and the stirring time at this time are preferably the same as in the first time. The solid content obtained by the third filtration is used in the subsequent cluster acid catalyst removal step. In addition, the filtrate obtained by the third filtration may be used again for the separation of the cluster acid catalyst in combination with other mixtures as in the filtrate obtained by the second filtration, or obtained by the first filtration. The cluster acid catalyst may be regenerated by mixing with the obtained filtrate.

  In the second solid-liquid separation step (2), after mixing the solid content obtained in the first solid-liquid separation step or the solid content obtained after elution of the cluster acid catalyst obtained in the pressing step described later with water, plant fibers This is a step of separating the residue into an aqueous solution.

FIG. 4 is a diagram showing a typical example of the second solid-liquid separation step of the present invention.
First, distilled water is added to the solid content obtained in the first solid-liquid separation step or the solid content obtained after elution of the cluster acid catalyst obtained in the pressing step and stirred. The sugar concentration in the aqueous solution is adjusted by the amount of distilled water.
Next, it separates into a vegetable fiber residue and aqueous solution by filtration. Since it is considered that most of the sugar obtained in the hydrolysis step described above is dissolved in the aqueous solution at this time, sugar crystals can be obtained by drying under reduced pressure and removing water.

  The pressing step (3) is a poor solvent for sugars in the solid content obtained in the first solid-liquid separation step described above or the plant fiber residue obtained in the second solid-liquid separation step described above and is a cluster. In this step, the acid catalyst is impregnated with a second organic solvent, which is a good solvent, and then squeezed to elute the cluster acid catalyst remaining in the pores of the solid or plant fiber residue.

Wood contains components that are not hydrolyzed, such as lignin, and thus a residue containing lignin and the like is obtained after hydrolysis using a cluster acid catalyst. In the residue, cellulose or hemicellulose reacts in the hydrolysis reaction and falls out, resulting in pores. It is considered that the cluster acid catalyst remaining in the pores cannot be sufficiently recovered in the first and second solid-liquid separation steps.
Therefore, in the pressing step, by eluting the cluster acid catalyst remaining in the pores in the plant fiber residue, the cluster acid catalyst remaining in the pores that could not be sufficiently recovered until now can be recovered.

Specific examples of the pressing method include a method using a screw type decanter and a method using a press plate type decanter.
The screw-type decanter is an apparatus that presses and removes a sample by utilizing the rotation of a screw in a liquid removal chamber provided with an inner cylinder screw in an outer cylinder screen. In particular, the outer cylinder screen is always rotated at a lower speed than the conventional screw type decanter with the outer cylinder screen fixed, and the inner cylinder screw is differentially rotated in the same rotational direction at a higher speed than the outer cylinder screen. It is preferable to use a differential rotary screw type decanter for performing the liquid because of high efficiency.
A press plate type decanter is a device that continuously presses with a press plate to separate a solid and a liquid. In particular, it is preferable that a screw mechanism for conveying the pressed solid is attached.

Specific examples of the second organic solvent include alcohols such as ethanol, methanol, and n-propanol. Alcohols can be preferably used, and ethanol is particularly preferable. Ethanol is one of the most suitable solvents because the solubility of the cluster acid catalyst is very high.
Thus, by using alcohol as the second organic solvent, the cluster acid catalyst can be eluted as much as possible from the solid matter or the plant fiber residue in the pressing step.

FIG. 5 is a diagram showing a typical example of the pressing process of the present invention.
First, the solid content obtained in the first solid-liquid separation step or the vegetable fiber residue obtained in the second solid-liquid separation step is dried and then impregnated in the second organic solvent. The amount of the second organic solvent may be such that the solid content or the vegetable fiber residue is wetted throughout.
Next, it isolate | separates into a vegetable fiber residue and a cluster acid catalyst solution by pressing. For the compression, any of the above-described screw type decanter and press plate type decanter can be used.
Then, it is determined whether it was able to fully squeeze. An example of the determination method is weight reduction before and after pressing. When it determines with not being able to fully squeeze, it impregnates in a 2nd organic solvent and squeezes again. Depending on the criteria, it is preferable to squeeze about three times.

As described above, either (2) the second solid-liquid separation step or (3) the pressing step may be performed first. FIG. 6 is a diagram showing a typical example of the saccharification / separation method of the present invention, and is a process diagram performed in the order of the first solid-liquid separation process, the second solid-liquid separation process, and the pressing process.
In this typical example, based on the solid content (filtrate 3) obtained in the first solid-liquid separation step, the plant fiber residue and the aqueous solution are separated in the second solid-liquid separation step. About the obtained plant fiber residue, the cluster acid catalyst which remained in the pore in a plant fiber residue is collect | recovered through a pressing process.

FIG. 7 is a diagram showing a second typical example of the saccharification / separation method of the present invention, and is a process diagram performed in the order of the first solid-liquid separation step, the pressing step, and the second solid-liquid separation step. In the second typical example, the first solid-liquid separation step is described by changing the number of times of filtration to two.
In the second typical example, the solid content (filtrate 2) obtained in the first solid-liquid separation step is further subjected to a pressing step, whereby the cluster acid remaining in the pores in the solid content is obtained. The catalyst is recovered and separated into a vegetable fiber residue and an aqueous solution in the second solid-liquid separation step based on the solid content after elution of the cluster acid catalyst.

  According to the present invention, the cluster acid catalyst remaining in the pores in the solid content obtained in the first solid-liquid separation step or the plant fiber residue obtained in the second solid-liquid separation step is obtained in the pressing step. By elution, the recovery rate of the cluster acid catalyst can be improved. In addition, according to the present invention, since the residual amount of the cluster acid catalyst in the sugar can be reduced as much as possible, a highly pure sugar can be obtained.

1. Saccharification / separation of plant fiber material The saccharification / separation of plant fiber material was performed by the methods of Examples 1 and 2 described below.
The cluster acid was identified and quantified by ICP (Inductively Coupled Plasma).

[Example 1]
Distilled water was put in the sealed container in advance, the temperature was raised to a predetermined reaction temperature (70 ° C.), the inside of the container was brought into a saturated vapor pressure state, and water vapor was adhered to the inner surface of the container.
Next, as shown in FIG. 2, 1 kg of heteropolyacid (a crystallization water amount has been measured in advance), which is a type of cluster acid catalyst, and water and cellulose required to make the crystallization water amount of the heteropolyacid 100% hydrolyze. Into the container, distilled water (35 g) of a deficiency from the total amount of water necessary to become glucose (55.6 g) (excluding the moisture at the saturated vapor pressure at 70 ° C.) is put into a container and heated. Stirring was continued, and stirring was continued for another 5 minutes after the temperature in the container reached 70 ° C.
Subsequently, 0.5 kg of ground cedar as a plant fiber material was placed in the container, and stirring was continued at 70 ° C. for 2 hours. Thereafter, the heating was stopped, and the container was cooled to room temperature while opening the container and discharging excess water vapor (the hydrolysis step).
Next, the obtained mixture was separated in the order of the first solid-liquid separation step, the second solid-liquid separation step, and the pressing step as in the typical example shown in FIG.
In the first solid-liquid separation step, as shown in FIG. 6, 500 ml of ethanol used for washing twice is added to the mixture and stirred for 30 minutes, followed by filtration to obtain filtrate 1 and filtrate 1. It was. Filtrate 1 (heteropolyacid ethanol solution) was recovered. On the other hand, the filtrate 1 was further added with 500 ml of ethanol used for washing once, stirred for 30 minutes, and then filtered to obtain a filtrate 2 and a filtrate 2. 500 ml of new ethanol was added to the filtrate 2 and stirred for 30 minutes, followed by filtration to obtain a filtrate 3 and a filtrate 3.
In the second solid-liquid separation step, 300 mL of distilled water was added to the filtrate 3 obtained in the first solid-liquid separation step, followed by filtration and separation into a vegetable fiber residue and an aqueous solution.
In the pressing step, 500 mL of ethanol was used as the second organic solvent, and after impregnating the plant fiber residue obtained in the second solid-liquid separation step at room temperature for 30 minutes, the above-described press plate decanter was used. The pressing liquid containing heteropoly acid was obtained from the plant fiber residue by pressing. The said pressing liquid was dried under reduced pressure and the heteropoly acid was obtained.
The total amount of heteropolyacid recovered was 98.7% of the amount used for hydrolysis.

[Example 2]
Similarly to Example 1, 0.5 kg of cedar ground product is subjected to hydrolysis according to the process shown in FIG. 2 using 1 kg of heteropolyacid which is a kind of cluster acid catalyst, and then contains sugar and heteropolyacid. A mixture was obtained.
Next, the obtained mixture was separated in the order of the first solid-liquid separation step, the pressing step, and the second solid-liquid separation step, as in the second typical example shown in FIG. .
In the first solid-liquid separation step, as shown in FIG. 7, 500 ml of ethanol used for one-time washing is added to the mixture and stirred for 30 minutes, followed by filtration to obtain filtrate 1 and filtrate 1. It was. Filtrate 1 (heteropolyacid ethanol solution) was recovered. On the other hand, 500 ml of new ethanol was further added to the filtrate 1 and stirred for 30 minutes, followed by filtration to obtain a filtrate 2 and a filtrate 2.
In the pressing step, 300 mL of ethanol is used as the second organic solvent, the solid content obtained in the first solid-liquid separation step is impregnated at room temperature for 30 minutes, and then the pressing using the press plate type decanter described above. Thereby, the pressing liquid containing heteropoly acid was obtained from the vegetable fiber residue. The said pressing liquid was dried under reduced pressure and the heteropoly acid was obtained.
In the second solid-liquid separation step, 500 mL of distilled water was added to the solid content after the elution of the cluster acid catalyst obtained in the pressing step, followed by filtration and separation into a vegetable fiber residue and an aqueous solution.
The total amount of heteropolyacid recovered was 98.7% of the amount used for hydrolysis.

[Comparative example]
Similarly to Example 1, 0.5 kg of cedar ground product is subjected to hydrolysis according to the process shown in FIG. 2 using 1 kg of heteropolyacid which is a kind of cluster acid catalyst, and then contains sugar and heteropolyacid. A mixture was obtained.
Next, the obtained mixture was separated in the order of the first solid-liquid separation step and the second solid-liquid separation step as in the step shown in FIG. In addition, the pressing process which is one of the characteristics of this invention was not performed.
In the first solid-liquid separation step, the solid-liquid separation was performed three times in the same manner as in Example 1 described above to obtain the filtrate 3 and the filtrate 3.
In the second solid-liquid separation step, 300 mL of distilled water was added to the filtrate 3 obtained in the first solid-liquid separation step, followed by filtration and separation into a vegetable fiber residue and an aqueous solution.
The total amount of recovered heteropolyacid was 96.7% of the amount used for hydrolysis.

2. Effects of Examples By comparing the results of Examples 1 and 2 with the results of Comparative Examples, by introducing a pressing step for eluting the heteropolyacid from the plant fiber residue or solid content, the recovery rate of the heteropolyacid is increased from 96.7% to 98 It was found that it can be improved to 7%. Moreover, by comparing the results of Examples 1 and 2, it was found that the same effect can be obtained regardless of the stage of the saccharification / separation method of the present invention.

It is a figure which shows the Keggin structure of heteropoly acid (phosphotungstic acid) which is 1 type of a cluster acid catalyst. It is the figure which showed an example of the hydrolysis process of this invention. It is the figure which showed the typical example of the 1st solid-liquid separation process of this invention. It is the figure which showed the typical example of the 2nd solid-liquid separation process of this invention. It is the figure which showed the typical example of the pressing process of this invention. It is the figure which showed the typical example of the saccharification separation method of this invention, and is a process figure at the time of performing in order of a 1st solid-liquid separation process, a 2nd solid-liquid separation process, and a pressing process. It is the figure which showed the 2nd typical example of the saccharification separation method of this invention, and is a process figure at the time of performing in order of a 1st solid-liquid separation process, a pressing process, and a 2nd solid-liquid separation process. It is the figure which showed the process of the comparative example.

Claims (6)

Hydrolyzing cellulose contained in the plant fiber material using a cluster acid catalyst to produce a sugar mainly composed of glucose,
At least a mixture of the saccharide produced in the hydrolysis step and the cluster acid catalyst is mixed with a first organic solvent that is a poor solvent for the saccharide and a good solvent for the cluster acid catalyst. A first solid-liquid separation step for separating the organic solvent solution containing the cluster acid catalyst and the solid containing the sugar and cluster acid catalyst residue through the process;
The solid content obtained in the first solid-liquid separation step or the solid content after elution of the cluster acid catalyst obtained in the subsequent pressing step is mixed with water, and then separated into a plant fiber residue and an aqueous solution. A second solid-liquid separation step;
The solid content obtained in the first solid-liquid separation step, or the plant fiber residue obtained in the second solid-liquid separation step, is a poor solvent for sugar and for the cluster acid catalyst It is characterized by having a pressing step of eluting the cluster acid catalyst remaining in the pores in the solid content or the plant fiber residue by pressing after impregnating the second organic solvent which is a good solvent. A method for saccharification and separation of plant fiber materials.   The saccharification / separation method according to claim 1, wherein the hydrolysis step is performed at 140 ° C. or lower under conditions of normal pressure to 1 MPa.   The saccharification and separation method according to claim 1 or 2, wherein the cluster acid catalyst is a heteropolyacid.   The saccharification and separation method according to any one of claims 1 to 3, wherein in the first solid-liquid separation step, the solubility of the sugar in the first organic solvent is 1 g / 100 ml or less.   5. The saccharification and separation method according to claim 1, wherein in the first solid-liquid separation step, at least one selected from ethers and alcohols is used as the first organic solvent.   The saccharification and separation method according to any one of claims 1 to 5, wherein an alcohol is used as the second organic solvent in the pressing step.

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