JP2012210160A - Method for producing monosaccharide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing monosaccharides to produce the monosaccharides with higher yield and selectivity by effectively hydrolyzing polysaccharides.SOLUTION: The method for producing monosaccharides by hydrolyzing polysaccharides by using a homogeneous acid catalyst includes a heating step of raising the temperature of a mixture including the polysaccharides and water, and a hydrolyzation step of hydrolyzing the polysaccharides by heating the mixture to 200°C or higher and then adding the homogeneous acid catalyst thereto.

Description

The present invention relates to a method for producing monosaccharides. More specifically, the present invention relates to a method for producing monosaccharides by hydrolysis of polysaccharides using a homogeneous acid catalyst.

In recent years, when the price of crude oil has soared, technology for producing chemicals such as ethanol and lactic acid from biomass, which is a recycled resource, has attracted attention. Among them, lignocellulosic biomass containing polysaccharides such as cellulose and hemicellulose is enormous and is expected to be used, but its use is limited because of its difficulty in chemical conversion. . In particular, the key to chemical conversion of lignocellulosic biomass is the saccharification reaction of cellulose into glucose. Since cellulose has high crystallinity, it is difficult to undergo hydrolysis, and it is difficult to efficiently saccharify cellulose. Monosaccharides produced by saccharification are mainly used as raw materials for microbial fermentation, and finally converted into chemicals such as ethanol.

Cellulose saccharification methods being studied at the practical application stage include the “concentrated sulfuric acid method” in which cellulose is treated at a low temperature in 80% high-concentration sulfuric acid, and cellulose at high temperature and high pressure in a low concentration sulfuric acid aqueous solution. Examples include “diluted sulfuric acid method” for treating, and “enzymatic method” for treating cellulose using an enzyme such as cellulase as a catalyst (see, for example, Non-Patent Document 1 and Non-Patent Document 2). In particular, in the dilute sulfuric acid method, a reaction raw material such as cellulose is charged into a reactor, and a dilute sulfuric acid solution as a catalyst is circulated therein, a reaction raw material such as cellulose and water, a dilute sulfuric acid solution as a catalyst, and In addition, a method is known in which water vapor as a heat source is separately supplied to a reactor, and the reaction is performed by mixing them at the reactor inlet (see, for example, Non-Patent Document 1).
A method of hydrolyzing a polysaccharide using a homogeneous acid catalyst such as a heteropolyacid is also known (see, for example, Patent Document 1).

Japanese Patent No. 4603627 (page 1-2)

Latest technology of biomass energy utilization (2001, CMC Publishing) NEDO 2005 Results Report “Development of standard ethanol fermentation technology using cellulosic biomass / Development of pretreatment, saccharification, and ethanol fermentation technology”

As described above, various methods for saccharification of cellulose have been studied at the practical application stage. However, in the concentrated sulfuric acid method, since a large amount of sulfuric acid is used, it is necessary to recycle, and there is a problem in energy and equipment cost for recovery of sulfuric acid. The dilute sulfuric acid method has problems such as a large amount of by-products and a low yield of monosaccharides. In addition, the enzymatic method has problems such as a slow reaction rate and a high enzyme cost. As described above, each method has a problem that becomes a major obstacle to putting it to practical use, and development of a more effective method has been demanded.

One of the methods that have been studied from such needs is a hydrolysis method using a homogeneous acid catalyst such as the heteropolyacid of Patent Document 1 described above. This biomass saccharification method is a method capable of efficiently and economically producing monosaccharides from polysaccharides, and at a low energy cost, efficiently separating homogeneous acid catalysts from a solution containing homogeneous acid catalysts. Thus, the homogeneous acid catalyst can be recovered at a high recovery rate. The hydrolysis reaction performed therein is performed by mixing raw materials containing cellulose, a catalyst and water and heating. However, in such a hydrolysis reaction of cellulose, only the target cellulose hydrolysis reaction can be performed. In addition, it is known that side reactions such that furfurals are generated sequentially by further intramolecular dehydration of the target product glucose. And since the said side reaction is reaction which is easy to advance at low temperature compared with the hydrolysis reaction of a cellulose, after a temperature rise of the reaction mixture which consists of a raw material containing a cellulose, a catalyst, and water starts, a hydrolysis reaction becomes active As the time to reach the proceeding temperature becomes longer, the side reaction proceeds accordingly, and it becomes difficult to obtain a good reaction selectivity. Therefore, in the hydrolysis reaction of the cellulose, it is possible to obtain a favorable reaction selectivity by raising the reaction mixture comprising the raw material containing cellulose, the catalyst and water to a high temperature as quickly as possible to complete the reaction in a short time. This is ideal. However, due to economic and device design constraints, it is not easy to carry out the reaction under ideal conditions with a device suitable for industrial production, and by-products are generated during the hydrolysis reaction. Development of a production method capable of producing monosaccharides at a higher yield and selectivity from polysaccharides has been an issue.

The present invention has been made in view of the above situation, and provides a method for producing a monosaccharide capable of efficiently hydrolyzing a polysaccharide and producing a monosaccharide with a higher yield and selectivity. With the goal.

The present inventor has conducted various studies on a method for producing a monosaccharide by hydrolyzing a polysaccharide using a homogeneous acid catalyst, and the hydrolysis reaction of the polysaccharide is performed under non-catalytic conditions as compared with the presence of the catalyst. We focused on the very slow reaction rate. And, first, when the mixture containing the polysaccharide and water is heated to raise the temperature, and when the temperature reaches the optimum temperature for the hydrolysis reaction, the polysaccharide is hydrolyzed by adding the catalyst. Compared to the case where water and catalyst are mixed together in advance and then heated to increase the temperature, the side reaction during the temperature increase can be prevented from progressing. The inventors have found that the desired monosaccharide can be produced with higher yield and selectivity even under the conditions, and have arrived at the present invention by conceiving that the above problems can be solved brilliantly. It is a thing.

That is, the present invention is a method for producing a monosaccharide by hydrolyzing a polysaccharide using a homogeneous acid catalyst, wherein the production method comprises a heating step of raising the temperature of the mixture containing the polysaccharide and water, And a hydrolysis step of hydrolyzing the polysaccharide by adding a homogeneous acid catalyst after the mixture is heated to 200 ° C. or higher.
The present invention is described in detail below.

The method for producing a monosaccharide of the present invention includes a heating step of heating a mixture containing a polysaccharide and water, and a homogeneous acid catalyst is added after the mixture containing the polysaccharide and water is heated to 200 ° C. or higher. And hydrolyzing the polysaccharide. Any of these steps may be performed once or twice or more. Moreover, as long as these processes are included, other processes may be included.

The heating step in the present invention is a step of raising the temperature of the mixture containing polysaccharide and water, but the mixture may contain other components as long as it contains polysaccharide and water. However, in the present invention, the mixture containing the polysaccharide and water but not containing the homogeneous acid catalyst is first heated and heated, and when the temperature reaches the optimum temperature for the hydrolysis reaction, the homogeneous acid catalyst is added. By carrying out the hydrolysis reaction of the polysaccharide, it has a technical feature in that the progress of the side reaction during the temperature rise can be suppressed. Therefore, the mixture is homogeneous before reaching 200 ° C. It is preferable that the acid catalyst is not substantially contained. Here, in a form in which the mixture does not substantially contain a homogeneous acid catalyst, in addition to a form in which no homogeneous acid catalyst is contained in the mixture before the mixture reaches 200 ° C., The homogeneous acid catalyst is contained in a small amount in the mixture before reaching the target, but the side reaction caused by the inclusion of the small amount of homogeneous acid catalyst in the mixture is caused by the monosaccharide that is the target product. Also included are forms that do not significantly affect the yield and selectivity and have the same effect as a form in which no homogeneous acid catalyst is contained in the mixture.
The mixture is more preferably a form containing no homogeneous acid catalyst before reaching 200 ° C., that is, a form containing polysaccharide and water excluding the homogeneous acid catalyst.

In the present invention, the side reaction proceeds very slowly because the mixture reaches 200 ° C. and is in a non-catalytic state in which the homogeneous acid catalyst is not substantially added to the reaction system until the hydrolysis step is started. . Accordingly, the temperature raising conditions in the heating step are not particularly limited unless the temperature rises so slowly that the generation of by-products due to the decomposition of the polysaccharide in the non-catalytic state becomes a problem. .3 ° C./second is preferred. More preferably, the lower limit is 0.5 ° C./second, and more preferably 0.7 ° C./second. Moreover, as an upper limit of the said temperature rising conditions, 50 degree-C / sec is preferable.

The hydrolysis step in the present invention is a step of performing a hydrolysis reaction of the polysaccharide by adding a homogeneous acid catalyst to the mixture after the mixture containing the polysaccharide and water is heated to 200 ° C. or higher by the heating step. It is.
The addition form of the homogeneous acid catalyst is not particularly limited as long as the homogeneous acid catalyst and the polysaccharide come into contact with each other in the presence of water, but the aqueous solution containing the homogeneous acid catalyst is a polysaccharide. The form added to the mixture containing water and water is preferred. The addition may be performed in a lump or may be divided into a plurality of times, but is preferably performed in a lump in order to increase the yield and selectivity of monosaccharides.
Examples of the reactor type in the hydrolysis step include a batch reactor, a continuous reactor, and a semi-continuous reactor. Among these, a continuous reactor is preferable.
Further, an organic solvent may be mixed during the reaction, and examples of such an organic solvent include ethanol, butanol, and acetone.

In the hydrolysis step, the homogeneous acid catalyst is added to the mixture after the mixture containing the polysaccharide and water is heated to 200 ° C. or higher in the heating step. Even if the temperature of the mixture is too high, it is difficult to control the subsequent hydrolysis reaction, which may be disadvantageous economically. More preferably, it is 210-270 degreeC, More preferably, it is 220-260 degreeC, Most preferably, it is 230-250 degreeC.
In addition, since the longer the time from when the temperature of the mixture becomes 200 ° C. or more to the addition of the homogeneous acid catalyst, the longer the non-catalytic reaction with a lower reaction selectivity proceeds, the temperature of the mixture It is preferable to add the homogeneous acid catalyst at the same time as the temperature reaches the temperature at which the hydrolysis step is carried out.

As the concentration of the homogeneous acid catalyst in the hydrolysis step, the mass ratio of the homogeneous acid catalyst to water present in the reaction system (homogeneous acid catalyst: water) is 0.1: 99.9 to 50: 50 is preferable. By setting such a catalyst concentration, the reaction and the recycling of the catalyst can be made more efficient and economical. More preferably, it is 0.5: 99.5-30: 70 as a density | concentration of a homogeneous acid catalyst, More preferably, it is 1: 99-20: 80.
In addition, the water said here means the total amount of the water which exists in a reaction system, and includes all the water etc. which are added to the water | moisture content which a raw material contains and a mixture. The amount of water can be changed by adding or removing water, but here it is defined as the amount of water at the start of the hydrolysis reaction.
Moreover, the density | concentration of a homogeneous acid catalyst will be 50% when it represents with mass ratio 50:50. In the present invention, unless otherwise specified,% represents mass%.

The mixture provided for the production method of the present invention may contain, in addition to polysaccharides, water, a homogeneous acid catalyst, an organic solvent described later, etc., but the total of polysaccharides and water with respect to 100% by mass of the entire mixture. The mass is preferably 80% by mass or more. By using such a mixture, monosaccharides can be obtained with higher yield and selectivity. More preferably, it is 90 mass% or more, More preferably, it is 95 mass% or more.
Furthermore, the concentration of the polysaccharide in the hydrolysis step is preferably 1 to 70%, more preferably 5 to 60%, and more preferably 10 to 50%, as the mass% of the polysaccharide with respect to the total amount of the mixture containing polysaccharide and water. % Is more preferable.
Here, the total amount of the mixture containing the polysaccharide and water means a mass including all of the polysaccharide, water, a homogeneous catalyst, and other solvents such as the organic solvent, etc. that are subjected to the hydrolysis step. Moreover, the mass of a polysaccharide means a dry body mass.

The hydrolysis reaction in the hydrolysis step is preferably performed at 200 to 300 ° C.
The higher the temperature, the higher the hydrolysis reaction rate and the maximum yield of monosaccharides, but the hydrolysis reaction is preferably carried out at 200 to 300 ° C. in consideration of production costs and the like. More preferably, it is 210-270 degreeC, More preferably, it is 220-260 degreeC, Most preferably, it is 230-250 degreeC.
Moreover, it is preferable that the reaction pressure in the said hydrolysis process is 0.01-100 Mpa, 0.03-70 Mpa is more preferable, 0.05-50 Mpa is still more preferable. The method for setting the reaction pressure to such a pressure is not particularly limited, but in the case of a pressurized state, it is preferable to introduce an inert gas such as nitrogen or argon into the reaction vessel.
The reaction solution pH is preferably pH 4 or lower, more preferably pH 3 or lower, and still more preferably pH 2 or lower.

The reaction time in the hydrolysis step is preferably 0.1 to 1000 minutes. If the reaction time is shorter than 0.1 minutes, the hydrolysis of the monosaccharide cannot be sufficiently advanced, and the yield of the monosaccharide may not be sufficient. On the other hand, if the reaction time is longer than 1000 minutes, the monosaccharide is excessively decomposed, and the selectivity for the monosaccharide may be reduced. In particular, when the reaction temperature of the hydrolysis reaction is high, the maximum yield of monosaccharide increases, but the reaction rate of monosaccharide overdegradation also increases, so that the monosaccharide overdegradation proceeds in a shorter time, yield, The selectivity will be reduced. More preferably, it is 0.2-200 minutes, More preferably, it is 0.3-60 minutes.

In the hydrolysis step, the hydrolysis reaction may be performed in multiple stages. In particular, when lignocellulose is used as the polysaccharide, it is preferably performed in multiple stages. This is because the decomposition temperature ranges of hemicellulose and cellulose contained in lignocellulose are different. That is, it is preferable to decompose hemicellulose which can be decomposed under relatively weak conditions in the first stage and to decompose cellulose under more severe conditions in the second stage. The homogeneous acid catalyst used in the first stage and the second stage may be the same or different.

Examples of the polysaccharide used in the present invention include lignocellulose, cellulose, hemicelluloses such as xylan, arabinan, mannan, and galactan, chitin, chitosan, agarose, alginic acid, carrageenan, β-glucan, and starch. . Lignocellulose, cellulose and hemicellulose are preferable, and lignocellulose and cellulose are more preferable.
Lignocellulose is a cellulosic and hemicellulosic material containing lignin, and is a biomass present in large quantities in plants.

As the origin of the polysaccharide, plants such as conifers, hardwoods, herbs, palms, algae, seaweeds, and biomass derived from microorganisms are preferable. Specifically, waste wood or waste paper derived from conifers, hardwoods, sugarcane (bagasse, leaves), corn (core, leaves), rice straw, wheat straw, switchgrass, oil palm (stems, leaves, empty fruit bunches, fruit squeezes Biomass) such as seaweed, algae (cell wall, intracellular solids), seaweed (cell wall, intracellular solids), etc., more preferably palm stems such as oil palm, leaves, empty fruit bunches, fruit squeezes Dust and algae cell walls and intracellular solids, more preferably empty fruit bunch of palms and algae cell walls and intracellular solids. The empty fruit bunch of palms is easily obtained because it is discarded in large quantities, and the algae has the merit of being easily decomposed because it does not contain lignin. The polysaccharide may be used for the reaction after pretreatment such as grinding and drying.

The salts, lignin or hemicellulose present in the raw material polysaccharide is preferably used after being removed in the pretreatment step. The process of removing such salts, lignin, or hemicellulose is defined as a desalting process, a delignification process, and a dehemicellulose process, respectively. Natural biomass such as lignocellulose generally contains a variety of salts, and when these salts are mixed with a homogeneous acid catalyst, salt exchange occurs. Since salt exchange causes a change in catalyst species, a decrease in acid strength, and the like, it is preferable to remove salts as much as possible.
In particular, when the heteropolyacid described later is used as the homogeneous acid catalyst, the homogeneous acid catalyst is insolubilized by salt exchange and the activity is extremely reduced. In order to avoid this, it is preferable to use a polysaccharide that has undergone a desalting step.

In addition, since lignin may adsorb a homogeneous acid catalyst, the presence of lignin in the reaction raw material may cause the yield of monosaccharides to decrease or the catalyst recovery rate to decrease. By removing lignin in the delignification step before the hydrolysis reaction, the yield of monosaccharides by the hydrolysis reaction can be improved, and the recovery rate of the catalyst after the hydrolysis reaction can be increased.
Furthermore, since lignin may be reduced in molecular weight and cause fermentation inhibition, fermentation inhibition can be avoided by removing lignin.

Moreover, hemicellulose contained in biomass such as lignocellulose decomposes at a lower temperature than crystalline cellulose. Therefore, in the case where the present invention is carried out for the purpose of decomposing cellulose, if hemicellulose is present in the raw material polysaccharide, a by-product such as furfural is generated by overdecomposition. Since this causes a decrease in the yield of monosaccharides derived from hemicellulose and fermentation inhibition due to furfural or the like, it is preferable to remove hemicellulose in advance.

Examples of the desalting step include a method of elution and removal with a solvent such as water, a method of further adding an acid or alkali to the solvent, and elution and removal with acid decomposition or alkali decomposition. Elution may be promoted by heating. A method of elution and removal in hot water is preferred, and a method of elution and removal in hot water to which an acid or alkali is added. One of these methods may be performed, or two or more methods may be combined.

The acid used in the desalting step is preferably a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, polyacid, or carbonic acid, or an organic acid such as acetic acid or sulfonic acid, and the alkali is sodium hydroxide or hydroxide. Potassium, calcium hydroxide, magnesium hydroxide, ammonia and the like are preferable. Among these, sulfuric acid, carbonic acid, hydrochloric acid, sodium hydroxide, and ammonia are more preferable, and sulfuric acid and sodium hydroxide are more preferable.

In the desalting step, it is preferable to elute the salt at a temperature of 10 to 200 ° C. after adding a solvent to the raw material polysaccharide. By treating at such a temperature, the salt can be sufficiently eluted. More preferably, it is 20-150 degreeC, More preferably, it is 50-120 degreeC.
Moreover, it is preferable that the time of the process which elutes a salt is 0.01 to 10 hours. More preferably, it is 0.05-3 hours, More preferably, it is 0.1-1 hour.

In the desalting step, it is preferable to remove 50% or more of the salts present in the raw material before the desalting step, more preferably 80% or more, and still more preferably 90% or more.
The salt content can be determined by ash content measurement, fluorescent X-ray measurement, ion chromatography, ICP (inductively coupled plasma) emission spectrometry, or the like.

As the delignification step, a method of removing by eluting with an alkaline aqueous solution or a method of removing by eluting with a solution containing an organic solvent is preferable. An acid or an alkali may be added to the organic solvent. By adding an acid or an alkali, decomposition of lignin can be promoted. Further, elution and decomposition may be promoted by heating.

The acid or alkali used in the delignification step can be the same as that used in the desalting step. As the organic solvent used in the delignification step, acetone, ethanol, butanol, methanol, propanol, methyl ethyl ketone, tetrahydrofuran, hexane, toluene and the like can be used. Among these, acetone, ethanol, butanol are preferable, and acetone is more preferable. preferable.

In the delignification step, the solution is preferably added to the raw material polysaccharide and then treated at a temperature of 10 to 200 ° C. By treating at such a temperature, lignin can be sufficiently eluted. More preferably, it is 50-180 degreeC, More preferably, it is 80-150 degreeC. Moreover, as processing time, it is preferable that it is 0.01 to 10 hours, More preferably, it is 0.05 to 5 hours, More preferably, it is 0.1 to 2 hours.

In the delignification step, it is preferable to remove 50% or more of the lignin present in the raw material before the delignification step, more preferably 80% or more, and still more preferably 90% or more.
The content of lignin can be determined, for example, by the method described in Analytical Chemistry Handbook 4th Edition (1991, Maruzen).

The dehemicellulose step can be carried out in the same manner as the desalting step, but requires stricter conditions than the desalting step. That is, the processing temperature is preferably 50 to 250 ° C, more preferably 100 to 200 ° C, and still more preferably 120 to 180 ° C. Moreover, as processing time, it is preferable that it is 0.01 to 10 hours, More preferably, it is 0.05 to 5 hours, More preferably, it is 0.1 to 2 hours.

In the dehemicellulose process, it is preferable to remove 50% or more, more preferably 80% or more, and still more preferably 90% or more of the hemicellulose present in the raw material before the dehemicellulose process. The content of hemicellulose can be determined, for example, by the method described in Analytical Chemistry Handbook 4th Edition (1991, Maruzen).
The desalting step, the delignification step, and the dehemicellulose step may be performed separately or simultaneously.
The pretreatment step preferably includes a desalting step, or includes a dehemicellulose step, more preferably includes a desalting step and a dehemicellulose step, and a dehemicellulose step. And a delignification step, and more preferably a desalting step and a dehemicellulose step.

The homogeneous acid catalyst used in the present invention is a homogeneous acid catalyst and refers to an acid catalyst that is uniformly dissolved in a reaction solution. The homogeneous acid catalyst preferably has higher acidity from the viewpoint of hydrolysis activity. As a specific index, the pH of the aqueous solution when the acid catalyst is dissolved in water at a concentration of 5% by mass is preferably a pH of 4 or less, more preferably a pH of 3 or less, and a pH of 2 More preferably, the following is shown.

The molecular weight of the homogeneous acid catalyst is preferably 200 to 500,000. When the molecular weight of the homogeneous acid catalyst is less than 200, after the hydrolysis step in the present invention, an operation of separating the homogeneous acid catalyst and the monosaccharide to be produced with a molecular sieve membrane (separation membrane) as will be described later. When performing, since the molecular weight of the produced monosaccharide is about 150 to 200, there is a possibility that it cannot be sufficiently separated, but by making it 200 or more, catalyst separation can be performed more efficiently and economically. It becomes possible. More preferably, it is 300-300000 as a molecular weight of a homogeneous acid catalyst, More preferably, it is 300-100000.
Further, when performing the operation of separating the homogeneous acid catalyst and the monosaccharide to be produced by a molecular sieve membrane (separation membrane), the difference between the molecular weight of the homogeneous acid catalyst and the molecular weight of the molecular sieve membrane is 100. It is preferably above, more preferably 1000 or more, still more preferably 3000 or more.

Specific examples of the homogeneous acid catalyst include organic compounds having a sulfonic acid group, organic compounds having a carboxylic acid group, and polyacids such as homopolyacid and heteropolyacid. Among them, organic compounds having a sulfonic acid group having a high acid strength (sulfonic acid group-containing compound) and heteropolyacids are preferable, and heteropolyacids are more preferable. That is, it is one of the preferred embodiments of the present invention that the homogeneous acid catalyst contains a heteropolyacid.
The sulfonic acid-containing compound has various molecular weights, and the heteropolyacid has an advantage that the molecular weight is uniform. In addition, heteropolyacids exhibit higher selectivity than other catalysts such as sulfuric acid in the hydrolysis reaction of polysaccharides at a low catalyst concentration of 50% or less, and in particular, phosphotungstic acid described later exhibits higher selectivity. There is an advantage of showing. Another advantage of the heteropolyacid is that it is an acid, but the corrosivity of the metal is extremely low. This is because an oxide film is formed on the metal surface by the oxidizing power of the heteropolyacid. Since the corrosiveness is low, there is an advantage that the apparatus cost can be reduced.

The organic compound having a sulfonic acid group is an organic compound having at least one sulfonic acid group in the molecule. Specific examples include naphthalene sulfonic acid, pyrene sulfonic acid, lignin sulfonic acid and the like. The sulfonic acid group may have one or more, and has a substituent other than the sulfonic acid group. May be. Polymers obtained by polymerizing sulfonic acid group-containing monomers such as vinyl sulfonic acid, styrene sulfonic acid, sulfomaleic acid, allyloxy-hydroxy-propane sulfonic acid, or copolymerizing with monomers such as acrylic acid and maleic acid Also included. Alternatively, polymers obtained by sulfonating a polymer such as polystyrene, polyethylene, polypropylene, and polyvinyl alcohol are also included. Among these, lignin sulfonic acid and various sulfonic acid group-containing polymers are preferable, and various sulfonic acid group-containing polymers are more preferable. The sulfonic acid group-containing polymer is preferably a polymer obtained by polymerizing vinyl sulfonic acid and styrene sulfonic acid, or a polymer obtained by copolymerizing vinyl sulfonic acid and styrene sulfonic acid with acrylic acid or maleic acid. .
Moreover, it may have a salt structure in which a part of protons is substituted with a cation species. In that case, the cation species is not particularly limited, and examples thereof include sodium, magnesium, ammonium and the like.
The organic compound having a sulfonic acid group may be used alone or in combination of two or more.

Examples of the heteropolyacid include phosphotungstic acids such as Keggin phosphotungstic acid (H ₃ PW ₁₂ O ₄₀ ) and Dawson phosphotungstic acid (H ₆ P ₂ W ₁₈ O ₆₂ ), and Keggin silicotungstic acid (H ₄ SiW). ₁₂ O ₄₀ ), silicotungstic acid, Keggin-type borotungstic acid (H ₅ BW ₁₂ O ₄₀ ), etc. Examples thereof include acids, cavernadotungstic acid, and metal-substituted heteropolyacids. From the viewpoint of catalytic activity in various reactions, among these, phosphotungstic acid, silicotungstic acid, borotungstic acid, phosphomolybdic acid, and silicomolybdic acid are preferred, phosphotungstic acid and silicotungstic acid are more preferred, and phosphotungstic acid is preferred. Further preferred.
Moreover, it may have a salt structure in which a part of protons is substituted with a cation species. In that case, the cation species is not particularly limited, and examples thereof include sodium, magnesium, ammonium and the like.
The heteropolyacids and salts thereof may be used alone or in combination of two or more.
Thus, it is also one preferred embodiment of the present invention that the homogeneous acid catalyst is phosphotungstic acid.

The monosaccharides produced by the method for producing monosaccharides of the present invention are obtained by hydrolyzing the polysaccharides used in the present invention described above. Specifically, glucose, xylose, arabinose, mannose, galactose , Uronic acid, glucosamine, and their anhydrous sugars such as levoglucosan. Glucose, mannose, xylose, and levoglucosan are preferable.

Examples of the use of the monosaccharide include use as a fermentation raw material, a chemical reaction raw material, a fertilizer, and a feed, and preferably a fermentation raw material. As fermentation raw material applications, monosaccharides are alcohols such as ethanol, butanol and 1,3-propanediol, organic acids such as acetic acid, lactic acid, itaconic acid, malic acid, citric acid, acrylic acid and 3-hydroxypropionic acid, It can be used for conversion to various amino acids such as aspartic acid, glutamic acid and lysine. Among these, ethanol, butanol, and acrylic acid and 3-hydroxypropionic acid are preferably used.

As a method for producing the monosaccharide of the present invention, after the hydrolysis step, a solid-liquid separation step for solid-liquid separation of the homogeneous acid catalyst-containing solution and the hydrolysis reaction residue is further performed. It is preferable to perform a catalyst separation step of separating the homogeneous acid catalyst from the separated homogeneous acid catalyst-containing solution and / or hydrolysis reaction residue. Thus, by separating and recovering the catalyst, the production cost of monosaccharides can be reduced. In particular, since heteropolyacids are much more expensive than sulfuric acid, it is important to recover and reuse the catalyst by performing such a catalyst separation step.
In the catalyst separation step, (A) the homogeneous acid catalyst-containing solution after the solid-liquid separation step is subjected to a membrane separation treatment of a homogeneous acid catalyst using a molecular sieve membrane of an organic polymer membrane to obtain a homogeneous acid. A step of separating the catalyst, (B) a step of subjecting the hydrolysis reaction residue after the solid-liquid separation step to thermal decomposition of the organic matter to separate the homogeneous acid catalyst, and (C) after the solid-liquid separation step At least one step selected from the group consisting of: separating the homogeneous acid catalyst by subjecting the hydrolysis reaction residue to an elution treatment of the homogeneous acid catalyst using an alkaline solution or an organic solvent-containing solution. It is preferable to include, and two or more of these steps may be included. In order to further increase the separation efficiency of the homogeneous acid catalyst, it is more preferable to include two or more of (A) to (C). More preferably, (A) and (B) are included.
Thus, after the hydrolysis step, the solid-liquid separation step for separating the homogeneous acid catalyst-containing solution and the hydrolysis reaction residue, and the homogeneous acid catalyst-containing solution separated by the solid-liquid separation step and A catalyst separation step of separating the homogeneous acid catalyst from the hydrolysis reaction residue, wherein the catalyst separation step includes at least one step selected from the group consisting of the following (A) to (C): The manufacturing method is also one of the preferred embodiments of the present invention.
(A) A step of separating the homogeneous acid catalyst by subjecting the homogeneous acid catalyst-containing solution to a membrane separation treatment of a homogeneous acid catalyst using a molecular sieve membrane of an organic polymer membrane.
(B) A step of separating the homogeneous acid catalyst by subjecting the hydrolysis reaction residue to which a part of the homogeneous acid catalyst is adsorbed to a thermal decomposition treatment of organic substances in the residue.
(C) The process of performing the elution process of the homogeneous acid catalyst using an alkaline solution or an organic solvent containing solution with respect to the hydrolysis reaction residue which a part of homogeneous acid catalyst adsorbed, and isolate | separating a homogeneous acid catalyst.

The solid-liquid separation step is a step of separating the reaction solution after the hydrolysis step into a homogeneous acid catalyst-containing solution and a hydrolysis reaction residue. As a method for performing such a solid-liquid separation step, Without being limited, pressure filtration (filter press etc.), suction filtration, squeeze separation (screw press etc.), centrifugation, sedimentation separation (decantation etc.), etc. can be used. Among these, pressure filtration and squeeze separation are preferable from the viewpoint of processing speed.

In the solid-liquid separation step, it is preferable that the reaction residue obtained by performing solid-liquid separation by filtration or the like is further washed with water. Thereby, the monosaccharide which remains in the reaction residue can be recovered in the water used for washing, and the yield of the monosaccharide can be increased.

The reaction residue contains an organic substance such as undegraded polysaccharide and a catalyst. In the step (B), the organic acid catalyst is subjected to a thermal decomposition treatment to separate the homogeneous acid catalyst.
The temperature of the thermal decomposition treatment is preferably 300 to 2000 ° C. If it is lower than 300 ° C., the organic substance may not be sufficiently decomposed and removed. If it is higher than 2000 ° C, the catalyst may be decomposed. More preferably, it is 350-1000 degreeC, More preferably, it is 400-800 degreeC.
Moreover, what is necessary is just to set the time of a thermal decomposition process suitably according to the quantity of the reaction residue, However, It is preferable that it is 1-1000 minutes. If it is shorter than 1 minute, the organic substance may not be sufficiently removed. If it is longer than 1000 minutes, the efficiency of the separation process is lowered. More preferably, it is 5-500 minutes, More preferably, it is 10-200 minutes.

In addition, when a hydrolysis process is performed using a heteropolyacid as a homogeneous acid catalyst, and a catalyst separation process is performed by the thermal decomposition treatment of (B) above, a decrease in the catalytic activity of the separated heteropolyacid may be observed. . In that case, it is preferable to recover the catalytic activity by hydrothermal treatment or catalyst restructuring treatment.
The hydrothermal treatment is to treat an aqueous catalyst solution prepared by adding water to the homogeneous acid catalyst separated in the catalyst separation step by thermal decomposition treatment (B) at a high temperature. As processing temperature, it is preferable that it is 150-350 degreeC, and it is more preferable that it is 200-300 degreeC. The hydrothermal treatment time may be set as appropriate while looking at the degree of recovery of the catalyst activity, but is preferably 1 to 1000 minutes, more preferably 5 to 100 minutes.
In addition, the catalyst restructuring process is to solubilize the homogeneous acid catalyst separated in the catalyst separation step by the thermal decomposition process of (B) in an alkaline aqueous solution, and to add the components of the homogeneous acid catalyst, It converts to the acid form. As an example, when phosphotungstic acid is used as the homogeneous acid catalyst, an alkaline aqueous solution is added to the residue after the thermal decomposition treatment to solubilize the phosphotungstic acid component (mainly tungsten oxide), The phosphotungstic acid is converted to the acid form by adding and further treating with an ion exchange resin or the like. By such treatment, the heteropolyacid catalyst having reduced catalytic activity is reconstructed and exhibits activity equivalent to that in the initial stage (before being subjected to the hydrolysis step). In this way, the heteropolyacid is used as the homogeneous acid catalyst, the catalyst separation step after the solid-liquid separation step is performed by the thermal decomposition treatment of (B), and the catalyst is reconstructed on the separated homogeneous acid catalyst. Application is also one of the preferred embodiments of the present invention.
In addition, as said alkaline aqueous solution, aqueous solutions, such as sodium hydroxide, lithium hydroxide, calcium hydroxide, sodium carbonate, can be used, for example. Among these, it is preferable to use an aqueous solution of sodium hydroxide or calcium hydroxide. More preferred is an aqueous solution of sodium hydroxide.

The step (C) is a step of adding an alkaline solution or an organic solvent-containing solution to the reaction residue separated by solid-liquid separation to elute the homogeneous acid catalyst. Any one of the alkaline solution and the organic solvent-containing solution may be used, or an alkaline solution and an organic solvent-containing solution may be mixed and used.

As the solution used in the step of eluting the homogeneous acid catalyst, either an alkaline solution or an organic solvent-containing solution may be used, but an organic solvent-containing solution is preferably used. When an organic solvent-containing solution is used, the acid catalyst can be separated as it is without being neutralized. When an alkaline solution is used, the acid catalyst is neutralized, but the catalyst can be separated with a high recovery rate.

When the homogeneous acid catalyst is eluted, the amount of the solution used is preferably 10 to 10,000% by mass with respect to 100% by mass (solid content) of the reaction residue. If the solution is less than 10% by mass, the catalyst may not be sufficiently eluted. When the amount of the solution is more than 10,000% by mass, the catalyst concentration is extremely lowered. More preferably, it is 50-1000 mass%, More preferably, it is 100-500 mass%.

The said alkaline solution can use the 1 type, or 2 or more types of solution of alkaline compounds, such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide. Among these, sodium hydroxide and calcium hydroxide are preferable. More preferred is sodium hydroxide.

As the organic solvent used in the organic solvent-containing solution, one or more of acetone, ethanol, butanol, propanol, methanol, diethyl ether, tetrahydrofuran, methyl ethyl ketone, hexane and the like can be used. Among these, acetone, ethanol, butanol, and diethyl ether are preferable. More preferably, it is acetone.

The alkaline solution may contain other components other than the alkaline compound as long as it is an alkaline solution. Examples of other components include water and organic solvents. Examples of the organic solvent include those described above. The organic solvent-containing solution may also contain other components as long as it contains an organic solvent. Other components include water.
In the alkaline solution, the content of the alkaline compound is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass when the entire alkaline solution is 100% by mass.
In the organic solvent-containing solution, the content of the organic solvent is preferably 10 to 100% by mass and more preferably 30 to 80% by mass when the entire organic solvent-containing solution is 100% by mass.

The homogeneous acid catalyst-containing solution obtained by the solid-liquid separation step contains a monosaccharide, a catalyst, and the like that are target products. In the step (A), monosaccharides and the homogeneous acid catalyst are separated by membrane separation using a molecular sieve membrane of an organic polymer membrane.
The membrane separation in the present invention is to separate a catalyst and a product monosaccharide using a separation material (separation membrane) having a membrane shape. Separation membranes can be classified according to their separation principles, for example, those based on molecular weight differences, those based on ionic differences, those based on hydrophilicity / hydrophobicity differences, etc. The separation membranes used in the present invention are based on molecular weight differences. Is. In other words, the separation membrane based on the molecular weight difference is a molecular sieve membrane, and the separation membrane used in the present invention is a molecular sieve membrane. Molecular sieve membranes are porous membranes that separate compounds according to their pore size.

The parameters representing the properties of the molecular sieve membrane include the molecular weight cut off and the pore diameter. The molecular weight cut off represents the lowest molecular weight that the separation membrane can block. In the present invention, the molecular weight of the molecule that is 90% blocked by the separation membrane is defined as the molecular weight cutoff. In the present invention, the molecular weight cutoff of the separation membrane is preferably 500,000 or less in terms of separation efficiency. More preferably, it is 300000 or less, More preferably, it is 100000 or less, and the range of 200-100000 is the most preferable. The average pore size of the separation membrane is preferably 0.01 to 1000 nm, more preferably 0.05 to 500 nm, and still more preferably 0.1 to 100 nm.

Examples of the molecular sieve membrane include ultrafiltration membranes, dialysis membranes, nanofiltration membranes (nanofiltration membranes), and reverse osmosis membranes, preferably ultrafiltration membranes, nanofiltration membranes (nanofiltration membranes). Most preferably a nanofiltration membrane (nanofiltration membrane).

The molecular sieve film is an organic polymer film, and the material thereof is carbon film, regenerated cellulose, cellulose acetate, nitrocellulose, polyvinylidene fluoride, polytetrafluoroethylene, polysulfone, polyethersulfone, polyacrylonitrile, poly Examples thereof include vinyl chloride, aramid, polyimide, aromatic polyamide, hydrophilized polyamide, polyester, polyethylene oxide, polyvinyl alcohol, polyethylene, polyvinyl acetate, polyamino acid, and those having a cation exchange group introduced thereto. Among them, those having high stability against acid, heat, and pressure are preferable, preferably carbon membrane, regenerated cellulose membrane, cellulose acetate membrane, polysulfone membrane, polyethersulfone membrane, aromatic polyamide membrane, hydrophilic polyamide membrane, In addition, a cation exchange group is introduced into them. Furthermore, a regenerated cellulose membrane, a cellulose acetate membrane, a polysulfone membrane, a polyethersulfone membrane, an aromatic polyamide membrane, a hydrophilic polyamide membrane, and those having a cation exchange group introduced therein are more preferable because of their particularly high stability. As these molecular sieve films, one kind may be used, or two or more kinds may be used.

Examples of the shape of the molecular sieve membrane include a tubular shape, a bag shape, a hollow fiber shape, a flat membrane shape, and a spiral shape, and preferably a tubular shape, a flat membrane shape, a hollow fiber shape, and a spiral shape. More preferably, it has a spiral shape. The thickness of the film is preferably 10 mm or less, more preferably 1 mm or less, and still more preferably 0.1 mm or less.

Specific examples of the molecular sieve film include the following. Pul ultrafiltration membranes: Omega series, Alpha series, Asahi Kasei Chemicals ultrafiltration membranes: Microza AP series, Microza SP series, Microosa AV series, Microosa SW series, Microosa KCV series, Nitto Denko Ultrafiltration membrane manufactured by NIT Corporation: NTU-2120, RS50, nanofiltration membrane manufactured by Nitto Denko Corporation: NTR-7250, NTR-7259, NTR-7410, NTR-7450, reverse osmosis membrane manufactured by Nitto Denko Corporation: NTR-70 , NTR-759, ES-40, ES-20, ES-15, ES-10, LES90, LF-10, manufactured by Millipore Ultrafiltration membrane: Biomax membrane, Ultracell membrane, manufactured by Daisen Membrane Systems Outer membrane: NADIR UH series, NADIR UP series, NAD RUS series, NADIR UC series, NADIR UV series, nanofiltration membrane manufactured by Daisen Membrane Systems: NADIR NP010, NADIR NP030, reverse osmosis membrane manufactured by Daisen Membrane Systems: NADIR SW, nanofiltration manufactured by Toray Industries, Inc. Membrane: SU series, Toray's reverse osmosis membrane: SU series, SUL series, SC series, GE Water & Process Technologies ultrafiltration membrane: G series membrane, P series membrane, MW series membrane, GE water -Nanofiltration membrane manufactured by And Process Technologies: DESAL series; Nanofiltration membrane manufactured by Cork Membrane: MPT series, MPS series.

Among the above molecular sieve membranes, preferably Omega series, Microza AV series, Microza SW series, RS50, NTR-7250, NTR-7259, NTR-7410, NTR-7450, Biomax membrane, NADIR UH series, NADIR UP Series, NADIR US series, NADIR UC series, NADIR UV series, NADIR NP010, NADIR NP030, SU series, G series film, P series film, MW series film, DESAL series, MPS series, more preferably NTR-7410, NTR-7450, NADIR NP010, NADIR NP030, G series membrane, DESAL series, MPS series, more preferably NTR-7410, NTR-745 , G series film, DESAL series, is the MPS series.

In the present invention, the molecular weight of the homogeneous acid catalyst, the molecular weight of the separation membrane, and the molecular weight of the monosaccharide are: molecular weight of the homogeneous acid catalyst> fractionation molecular weight of the separation membrane> molecular weight of the monosaccharide. . When the homogeneous acid catalyst-containing solution contains a solute other than the homogeneous acid catalyst, the molecular weight of the homogeneous acid catalyst> the molecular weight of the separation membrane> the molecular weight of the solute other than the homogeneous acid catalyst. A relationship is preferred. When membrane separation is performed under such conditions, the catalyst does not permeate the membrane but remains on the stock solution side (concentrate side), and solutes and solvents other than the homogeneous acid catalyst permeate the membrane and move to the permeate side. Since the catalyst on the concentration side is difficult to be diluted with a solvent such as water, the catalyst can be recovered at a high concentration and a high recovery rate can be achieved. Further, when it is necessary to concentrate the catalyst, it can be concentrated with low energy by membrane separation as it is.

Examples of the method for performing the membrane separation treatment include a method of pressurizing the stock solution side (concentrate side), a method of reducing the pressure of the permeate side, a method of diffusing by osmotic pressure, a method of centrifugation, and a method of utilizing a potential difference. However, a method of pressurizing the stock solution side and a method of diffusing by osmotic pressure are preferable, and a method of pressurizing the stock solution side is more preferable. In the case of the method of pressurizing the stock solution side, the pressure (gauge pressure) at the time of membrane separation is preferably 0.01 MPa to 10 MPa, more preferably 0.03 MPa to 5 MPa, and most preferably 0.05 MPa to 4 MPa. .

In the membrane separation process, both the dead-end format and the cross-flow format can be applied as the filtration format at the time of membrane separation. However, in the step of separating the homogeneous acid catalyst in the present invention, the homogeneous acid catalyst-containing solution has a high concentration. However, since it is possible to perform the separation of the homogeneous acid catalyst with high efficiency, the cross flow type is preferable.
Cross-flow membrane separation can be performed, for example, by a method of obtaining a permeated liquid by applying pressure to a spiral separation membrane module while feeding a separation target liquid with a liquid feed pump.
The temperature during the membrane separation is preferably 0 ° C to 100 ° C, more preferably 0 ° C to 80 ° C, and most preferably 5 ° C to 50 ° C.
For the membrane separation, any of batch, continuous and semi-continuous methods can be used, but batch and continuous methods are preferred. In order to improve the yield of monosaccharides, membrane separation may be performed while adding water to the concentrate.

The monosaccharides separated by the membrane separation treatment can be used for the fermentation step through a neutralization step as necessary. In the present invention, since the monosaccharide and the acid catalyst are separated by membrane separation, it is also an advantage that the necessity of neutralizing the sugar solution is low. That is, it is one of the preferred embodiments of the present invention that the method for producing monosaccharides includes a recycling step of collecting and recycling the homogeneous acid catalyst separated in the catalyst separation step. Here, recycling means that the catalyst recovered by membrane separation is repeatedly used for the hydrolysis reaction.

The acid catalyst concentration of the catalyst solution recovered by the membrane separation treatment is preferably 0.8 times or more, more preferably 1.0 times or more of the acid catalyst concentration used in the hydrolysis step. Preferably it is 1.5 times or more. By separating the recovered acid catalyst concentration from the acid catalyst concentration at the time of hydrolysis (that is, recovering it to a concentration of 1.0 times or more), the separated catalyst solution can be immediately recycled. Thus, it is one of the preferred embodiments of the present invention to perform the recycling step immediately after the catalyst separation step. Immediately performing the recycling process means performing the hydrolysis process again without performing the dehydration process for concentration. Prior to hydrolysis, the concentration may be adjusted by adding water.

Moreover, as an acid catalyst density | concentration of the said catalyst liquid collect | recovered, an upper limit is 50%. Although depending on the balance with the acid catalyst concentration during hydrolysis, it is more preferably 30%, still more preferably 20%, and most preferably 10%. The recovery rate of the catalyst recovered by the membrane separation treatment is preferably 50% or more, more preferably 70% or more, further preferably 90% or more, and most preferably 99% or more. preferable.

Although it is desirable to reuse the recovered catalyst as it is, it is preferable to provide a catalyst regeneration step when the proton concentration is lowered due to cation exchange. Here, the regeneration step is to return the exchanged cations to the proton type again. As a regeneration method, a method using a cation exchanger is preferred. Specifically, a method in which a proton-type cation exchanger and a recovered acid catalyst solution are contacted using a column is preferable. As the cation exchanger, an organic substance such as a cation exchange resin or an inorganic substance such as zeolite can be used. A method using a cation exchange resin is preferred. The cation exchanger whose proton has been reduced by cation exchange can be regenerated and reused by passing strong acids such as sulfuric acid through it.

The method for producing monosaccharides of the present invention has the above-described configuration, and can efficiently hydrolyze polysaccharides and produce monosaccharides with higher yield and selectivity. Can be suitably used.

FIG. 1 is a schematic view of a reaction apparatus used in Examples and Comparative Examples.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Unless otherwise specified, “part” means “part by weight” and “%” means “mass%”.

The analysis methods and calculation methods used in Examples and Comparative Examples are shown below.
<Quantification of monosaccharides>
High performance liquid chromatography (HPLC) was performed. The column was detected with a refractometer (RI) using TSK-GEL Amide 80 manufactured by Tosoh Corporation. The yield of monosaccharide was calculated according to the following formula.
Yield of monosaccharide (mass%) = (total mass of produced monosaccharide / mass of raw material polysaccharide) × 100
Here, the mass of the raw material polysaccharide is the dry weight of the raw material cellulose in the case of cellulose, and the empty palm of the palm (the fruit bunch after removing the fruit of the palm, hereinafter referred to as palm EFB). It means dry mass.

<Quantification of by-products>
Performed by HPLC. The column was detected by using an ultraviolet spectrophotometer (UV) and RI using TSK-GEL ODS-100V manufactured by Tosoh Corporation. The selectivity for monosaccharides in the saccharification reaction (production selectivity) was calculated according to the following formula.
Selectivity (mass%) = (total mass of produced monosaccharides / total mass of products (monosaccharides and by-products)) × 100
By-products are furfural, hydroxymethylfurfural, formic acid, levulinic acid, and acetic acid that are generated by monodegradation of monosaccharides.

Example 1
A saccharification reaction was carried out as follows using a reaction apparatus comprising a reaction vessel, a tank (catalyst solution tank) for holding a catalyst solution connected to the reaction vessel, and other accessory parts as shown in FIG.
A reaction vessel (1) was charged with 1.5 g of cellulose powder (trade name “Avicel”, manufactured by Merck KGaA) and 12.0 g of water, nitrogen gas was introduced from the valve (5) and prepressurized to 3 MPa. Further, 1.5 g of a 10 wt% aqueous solution of phosphotungstic acid (manufactured by Nippon Inorganic Chemical Co., Ltd.) was charged into the tank (2), and nitrogen gas was introduced from the valve (6) and pre-pressurized to 7 MPa. The reaction vessel was immersed in a heating medium bath maintained at 275 ° C. and heated to start the reaction. When the internal temperature reaches 240 ° C. after 300 seconds, the valves (7) and (8) are opened and the catalyst solution is pumped into the reaction vessel to continue the reaction. The reaction was terminated by removing from the medium bath and immersing in water at room temperature to quench. As a result of analyzing the reaction liquid from which unreacted cellulose was removed by filtration by high performance liquid chromatography, it was found that monosaccharides composed of glucose, mannose or levoglucosan were produced. As a result of changing the reaction time from the start of the temperature rise to the start of the rapid cooling as a result of changing the reaction time from the start of the temperature rise to the start of the rapid cooling, the yield of the monosaccharide was 64%. The highest value was shown, and the selectivity at that time was 88%.

(Example 2)
As a result of carrying out the reaction and analysis in the same manner as in Example 1 except that the catalyst was added when the internal temperature reached 225 ° C. after 180 seconds from the start of the reaction, the monosaccharides were collected when the reaction time was 340 seconds. The rate showed the highest value of 63%, and the selectivity at that time was 86%. In Example 2, the time for adding the catalyst was fixed at 180 seconds from the start of temperature increase.

(Example 3)
Results of carrying out the reaction and analysis in the same manner as in Example 1 except that instead of cellulose powder, a dried body of palm EFB that had been desalted and dehemicellulose treated in advance by the method described in Japanese Patent No. 4603627 was used. When the reaction time was 380 seconds, the yield of monosaccharides showed a maximum value of 52%, and the selectivity at that time was 71%.

(Comparative Example 1)
The reaction and analysis were performed in the same manner as in Example 1 except that the catalyst was added when the internal temperature reached 190 ° C. after 105 seconds from the start of the reaction. The rate showed the highest value of 58%, and the selectivity at that time was 83%. In Comparative Example 1, the time for adding the catalyst was fixed at 105 seconds from the start of temperature increase.

(Comparative Example 2)
The reaction and analysis were performed in the same manner as in Example 1 except that the catalyst was added at the start of the reaction to start the temperature increase. As a result, the yield of monosaccharides showed a maximum value of 58% when the reaction time was 300 seconds, The selectivity at that time was 82%. In Comparative Example 2, the catalyst was constantly added by adding it at the start of the reaction.

The following was found from the results of Examples and Comparative Examples.
When producing a monosaccharide by hydrolyzing a polysaccharide using a homogeneous acid catalyst, the temperature of the mixture containing the polysaccharide and water is first raised, and the mixture is heated to 200 ° C. or higher and then the homogeneous acid catalyst. It was proved that monosaccharides can be obtained with higher yield and selectivity by conducting hydrolysis reaction of polysaccharides by adding. On the other hand, a homogeneous acid catalyst is added when the temperature of the mixture containing the polysaccharide and water is less than 200 ° C., or a homogeneous acid catalyst is added at the start of temperature increase of the mixture containing the polysaccharide and water. In this case, it was confirmed that both the yield and selectivity of monosaccharides decreased.
In the above examples, examples of hydrolysis using a specific homogeneous acid catalyst and polysaccharide are shown, but the mechanisms for hydrolyzing polysaccharide using a homogeneous catalyst are all the same. Therefore, from the results of the above-mentioned Examples and Comparative Examples, the present invention can be applied in various technical forms of the present invention and in various forms disclosed in the present specification, and exhibit advantageous effects. Can be said.

1: Reaction vessel 2: Catalyst tank 3: Pressure gauge 4: Safety valve 5, 6, 7, 8: Cut-off valve 9: Thermocouple 10: Stirrer

Claims (5)

A method for producing a monosaccharide by hydrolyzing a polysaccharide using a homogeneous acid catalyst,
The production method includes a heating step of heating a mixture containing a polysaccharide and water, and a hydrolysis step of hydrolyzing the polysaccharide by adding a homogeneous acid catalyst after the mixture is heated to 200 ° C. or higher. And a method for producing a monosaccharide. The method for producing a monosaccharide according to claim 1, wherein the production method has a hydrolysis reaction temperature in the hydrolysis step of 200 to 300 ° C. The method for producing a monosaccharide according to claim 1 or 2, wherein the homogeneous acid catalyst contains a heteropolyacid. The method for producing a monosaccharide according to claim 3, wherein the homogeneous acid catalyst is phosphotungstic acid. The production method further includes a solid-liquid separation step of separating the homogeneous acid catalyst-containing solution and the hydrolysis reaction residue after the hydrolysis step, and a homogeneous acid catalyst-containing solution separated by the solid-liquid separation step And / or a catalyst separation step of separating the homogeneous acid catalyst from the hydrolysis reaction residue,
The method for producing a monosaccharide according to any one of claims 1 to 4, wherein the catalyst separation step includes at least one step selected from the group consisting of the following (A) to (C).
(A) A step of separating the homogeneous acid catalyst by subjecting the homogeneous acid catalyst-containing solution to a membrane separation treatment of a homogeneous acid catalyst using a molecular sieve membrane of an organic polymer membrane.
(B) A step of separating the homogeneous acid catalyst by subjecting the hydrolysis reaction residue to which a part of the homogeneous acid catalyst is adsorbed to a thermal decomposition treatment of organic substances in the residue.
(C) The process of performing the elution process of the homogeneous acid catalyst using an alkaline solution or an organic solvent containing solution with respect to the hydrolysis reaction residue which a part of homogeneous acid catalyst adsorbed, and isolate | separating a homogeneous acid catalyst.

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