JP2012044880A - Method for saccharifying cellulose - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for saccharifying cellulose which is capable of increasing a conversion ratio of the cellulose, yield of the saccharides and selectivity of the saccharides, and further, enhancing content ratio of glucose in the saccharides, while suppressing excessive decomposition of the saccharides due to a pressurized hydrothermal treatment.SOLUTION: The method of saccharifying cellulose by hydrolyzation includes: performing an alkali treatment of bringing a cellulose-containing material into contact with an alkaline solution; bringing the cellulose-containing material into contact with an aqueous solvent after cleaning the cellulose-containing material with water and/or an acid solution; applying a heating treatment and pressurizing treatment to the mixture; and obtaining an aqueous solution containing water-soluble oligosaccharide or glucose.

Description

  The present invention relates to a cellulose saccharification method. More specifically, the present invention relates to a method for saccharifying cellulose by hardly hydrolyzing a cellulosic polysaccharide that is promising as biomass and generating almost no excessively decomposed product.

  In recent years, saccharides obtained by saccharifying woody biomass have attracted attention as raw materials for producing useful substances such as ethanol and polylactic acid. Cellulose contained in woody biomass is a polysaccharide in which 1000 or more glucoses are connected by β-glycoside bonds. By hydrolyzing cellulose, in addition to glucose, which is a monosaccharide, water-soluble oligosaccharides (cellooligosaccharides) in which 2 to 6 glucoses are connected can be obtained. Among these water-soluble saccharides, glucose is useful for production of ethanol and lactic acid by fermentation using microorganisms, and therefore, a saccharification technique capable of efficiently producing glucose from cellulose is desired.

Conventional methods for saccharifying cellulose include thermal decomposition, acid catalysis using sulfuric acid as a catalyst (for example, alkenol method), enzymatic reaction using hydrolysis by enzymatic reaction, hydrolysis in supercritical or subcritical aqueous solution. A pressurized hot water method (for example, Patent Document 1) is known.
The conventional thermal decomposition method is a method of cleaving cellulose molecular chains with thermal energy, and can reduce the molecular weight of cellulose. However, since it is a thermal reaction, the selectivity of the reaction is poor and the yield of glucose is low.
In the acid catalyst method, cellulose is hydrolyzed with high-concentration sulfuric acid and then post-treated with dilute sulfuric acid to obtain glucose. However, there are processes such as sulfuric acid-containing residue treatment and sulfuric acid recovery along with the problem of equipment corrosion due to acid. Necessary. For this reason, practicality is currently reduced.

  The enzyme reaction method is a method of treating with cellulose hydrolase called cellulase, and is characterized by being able to be treated under mild reaction conditions (room temperature to 50 ° C.). In recent years, many domestic and overseas manufacturers have made efforts to develop new cellulases using gene manipulation technology. However, in general, cellulase itself is expensive, and it takes a long time of several days to one week to completely hydrolyze high molecular weight cellulose, which is a raw material, to glucose, resulting in poor productivity. . This is presumably because the reaction with cellulase becomes a solid-liquid reaction because the cellulose is in a solid state and is crystalline, and the reaction rate is low. For these reasons, a route for converting a glucose solution obtained from a cellulose raw material by an enzyme reaction method to ethanol by fermentation then has a significant problem in terms of cost.

  On the other hand, the use of supercritical water and subcritical water has the following advantages. That is, it is known that water in a subcritical state behaves as an acidic aqueous solution as its ionic product increases. Therefore, if this is used, cellulose can be efficiently and rapidly hydrolyzed without adding an acid catalyst. For example, according to Patent Document 1, glucose can be obtained from cellulose in a yield of 20% or more by using supercritical water or subcritical water. Furthermore, the yield is improved to some extent by controlling the temperature and pressure conditions and adding a small amount of acid. However, if the hydrolysis conditions are too high, the produced glucose undergoes a thermal decomposition reaction, and the yield decreases. Furthermore, it is known that the production of furfurals that are inhibitors of the ethanol fermentation process is also increased.

  Patent Document 2 proposes a method that combines the advantages of the above two methods. That is, this is a method in which cellulose is temporarily solubilized with supercritical water or subcritical water, and hydrolysis is performed with cellulase while the reaction product is dissolved in the solution. This reports the highest yield of 74.3% glucose production. However, this yield is a record of an enzyme treatment time of 5 days (50 ° C.) and does not necessarily lead to a reduction in enzyme saccharification time. Moreover, considering that the supercritical water treatment, which is a pretreatment, is a flow type of slurry, and that the reaction conditions are 320 to 500 ° C. and the pressure is 20 to 50 MPa, the equipment cost and energy cost are low. This is expected, and it seems that the reality is low as a mass production device.

  As described above, in the conventional method for obtaining glucose by hydrolyzing cellulose, restrictions on the reaction yield, cost, and production equipment are large, and drastic improvement has been demanded for practical use.

In recent years, attempts have been made to conduct a hydrolysis reaction of cellulose in the presence of an oxidizing agent.
For example, in Patent Document 3, in order to lower the molecular weight of cellulose, first, pretreatment is performed at 50 to 150 ° C. with oxidized water containing an oxidizing substance, and then the solution is adjusted to be acidic and the conditions are 100 to 200 ° C. Shows how to perform the hydrolysis. This is because the hydroxyl group of cellulose is partially oxidized by the above pretreatment to weaken the cohesive force between the cellulose chains and solubilize the cellulose. By applying this treatment, subsequent hydrolysis with dilute acid Is going to be promoted. Certainly, only 0.9% of cellulose is solubilized in a system that does not use an oxidizing agent, but a maximum solubilization rate of 66.7% is achieved using this method. However, the glucose yield is as low as 30.3% at the maximum, and has not reached the practical level.

  Moreover, in patent document 4, hydrolysis is accelerated | stimulated by making polysaccharides, such as a cellulose, contact with pressurized hot water in presence of oxidizing agents, such as a metal salt, and it can convert rapidly into an oligosaccharide or a monosaccharide. It is shown. According to this method, glucose was produced from crystalline cellulose in a yield of 30 to 40% at a reaction temperature of 250 ° C. However, there is a problem that 5-HMF (5-hydroxymethylfurfural), which is a sugar decomposition product and an inhibitor of fermentation, is produced in a yield of about 5 to 9%.

JP-A-5-31000 JP 2001-95594 A JP 2006-320261 A JP 2007-20555 A

  Thus, in the saccharification methods other than the enzyme reaction method of the conventional method, there is a problem that the conversion from cellulose to saccharide is low and the glucose content in the converted saccharide is further low. In addition, there is a problem in that water-insoluble aggregates and saccharide hyperdegradation products are generated as by-products. On the other hand, in addition to the problem of enzyme cost, the enzyme reaction method has an essential problem that it takes a long time for enzyme saccharification unless an appropriate pretreatment is used. If supercritical water / subcritical water treatment is applied as a pretreatment, the final glucose yield may exceed 70%. However, the reaction conditions for pretreatment are severe and the device must be devised. There is a problem that becomes high.

  The present invention has been made in view of the above circumstances, while suppressing the excessive decomposition of saccharides by pressurized hot water treatment, it is possible to increase the conversion rate of cellulose, the yield of saccharides, and the selectivity of saccharides, Furthermore, it aims at providing the cellulose saccharification method which can raise the glucose content rate in this saccharide | sugar.

In the cellulose saccharification method according to claim 1 of the present invention, an alkali treatment in which a cellulose-containing material and an alkaline aqueous solution are brought into contact is performed, and the cellulose-containing material is washed with water and / or an acidic aqueous solution, An aqueous solution containing a water-soluble oligosaccharide or glucose is obtained by contacting with an aqueous solvent, heat treatment and pressure treatment.
The cellulose saccharification method according to claim 2 of the present invention is characterized in that, in claim 1, the heat treatment is in a temperature range of 100 ° C to 300 ° C.
The cellulose saccharification method according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the pressure treatment is in a pressure range of 0.1 MPa to 30 MPa.
The cellulose saccharification method according to claim 4 of the present invention is the cellulose saccharification method according to any one of claims 1 to 3, wherein the cellulose aqueous solution is 0.1 to 20 N in a temperature range of -10 ° C to 50 ° C. The inclusion is contacted for a time range of 0.1 to 120 minutes.
The cellulose saccharification method according to a fifth aspect of the present invention is the method according to any one of the first to fourth aspects, in which the cellulose-containing material and the aqueous solvent are brought into contact with each other, the heat treatment and the pressure treatment, and the The operation for obtaining an aqueous solution containing a water-soluble oligosaccharide or glucose is carried out simultaneously and continuously.
The cellulose saccharification method according to claim 6 of the present invention is characterized in that, in any one of claims 1 to 5, cellulose in the cellulose-containing material constitutes cotton or paper.
The cellulose saccharification method according to claim 7 of the present invention is the cellulose saccharification method according to any one of claims 1 to 6, wherein the alkali treatment is performed in a saccharification treatment reactor.
The cellulose saccharification method according to claim 8 of the present invention is the cellulose saccharification method according to any one of claims 1 to 7, wherein the alkali treatment, the dehydration treatment, and the It is characterized by performing washing.

  According to the cellulose saccharification method of the present invention, it is possible to increase the conversion rate of cellulose, the yield of saccharides, and the selectivity of saccharides while suppressing the excessive decomposition of saccharides by pressurized hot water treatment. The glucose content in can be increased. The obtained high-purity glucose is useful as a raw material for ethanol fermentation or lactic acid fermentation.

It is an example of the apparatus which can be used for the cellulose saccharification method of this invention. It is a schematic diagram of the belt conveyor which can be used for the cellulose saccharification method of this invention.

The present invention will be described in detail below.
The cellulose saccharification method of the present invention is a method of hydrolyzing cellulose to saccharify, and is performed in the order of a pretreatment step and a reaction step.
In the pretreatment step, an alkali treatment is performed in which the cellulose-containing material (raw material) is brought into contact with an alkaline aqueous solution, and a washing treatment is performed in which the cellulose-containing material is washed with water and / or an acidic aqueous solution.
In the reaction step, the cellulose-containing material that has undergone the pretreatment step and an aqueous solvent are brought into contact with each other, and heat treatment and pressure treatment are performed to obtain an aqueous solution containing a water-soluble oligosaccharide or glucose.

  In the reaction step, an operation (operation A) for bringing the cellulose-containing material that has undergone the pretreatment step into contact with the aqueous solvent, a heat treatment and a pressure treatment (operation B), an aqueous solution containing a water-soluble oligosaccharide or glucose. The operations to be obtained (operation C) are not necessarily performed in this order. Operation A, operation B, and operation C may be performed in this order, and operation A, operation B, and operation C may be performed simultaneously and continuously.

  The cellulose saccharification method of the present invention may have operations or treatments other than those included in the pretreatment step and the reaction step.

<Preprocessing step>
In the pretreatment step, the method for bringing the cellulose-containing material into contact with the alkaline aqueous solution is not particularly limited. For example, a method of immersing the cellulose-containing material in the alkaline aqueous solution and bringing the cellulose-containing material into contact may be adopted, or the cellulose-containing material may be left in contact with the alkaline aqueous solution.

The cellulose-containing material in the present invention is preferably a cellulose-containing fiber and more preferably a fiber containing cotton because the effects of the present invention can be sufficiently obtained.
The cellulose-containing fiber is not particularly limited as long as it is a fibrous material containing cellulose. For example, cotton, hemp (linax, flax, manila hemp, zaiza hemp, kenaf hemp used as a fiber for clothing, etc. Etc.), Tencel, rayon, cupra, and the like, and paper products such as copy paper, wrapping paper, and cardboard are preferred. Further, the fiber of the clothing or the like may be a fiber blended with a synthetic fiber such as polyester or a fiber not containing cellulose such as silk.
The form of the cellulose-containing fiber is not particularly limited, and those processed into a cotton shape, a thread shape, a rope shape, a cloth shape, a flat surface, a solid shape, or the like can be used.

The length of the cellulose-containing fiber is preferably 1 mm or more and 1 m or less, more preferably 5 mm or more and 50 cm or less, and further preferably 1 cm or more and 30 cm or less.
When the length is within this range, the cellulose-containing fiber can be easily handled.

  From the viewpoint of increasing the conversion rate from cellulose to saccharide, it is preferable that the cellulose-containing product contains as little impurities as possible to inhibit the saccharification reaction. That is, the higher the cellulose content of the cellulose-containing material used in the present invention, the better.

  The aqueous alkali solution in the pretreatment step is not particularly limited as long as it can swell by increasing the water absorption of the cellulose-containing material, and examples thereof include sodium hydroxide and aqueous ammonia.

  By subjecting cellulose-containing fibers such as cotton fibers to an alkali treatment with sodium hydroxide or the like, the cellulose-containing fibers can swell and the amorphous region of cellulose can increase three times or more. Further, since the size of the crystal lattice of cellulose measured by X-ray diffraction also changes, it is considered that the intermolecular interaction of cellulose is changed by the alkali treatment. As the factor, for example, it is conceivable that the hydrogen bond between the hydroxyl groups of cellulose is broken by the adsorption of Na ions, and the bonding force between molecules is reduced.

  As described above, in the cellulose-containing material such as cotton fiber that has been swollen by the alkali treatment and increased in water absorption, water molecules attack the β-1,4 glycoside bond of cellulose in the cellulose-containing material in the subsequent reaction step. Since it becomes easy, it is thought that the efficiency of the hydrolysis reaction of cellulose can be remarkably improved.

In the pretreatment step, when the alkaline aqueous solution is a sodium hydroxide aqueous solution, the concentration (normality) is preferably 0.1 to 20N, more preferably 0.5 to 10N, and further preferably 1 to 5N. .
When the amount is not less than the lower limit and not more than the upper limit of the above range, the swelling and water absorption of cellulose (cellulose crystals) in the cellulose-containing material can be increased, and the subsequent hydrolysis reaction can be performed more efficiently.
On the other hand, when the amount is less than the lower limit and exceeds the upper limit of the above range, the cellulose swelling and water absorption in the cellulose-containing material tend to decrease.

In the pretreatment step, the temperature at which the cellulose-containing material and the alkaline aqueous solution are brought into contact is preferably −10 to 50 ° C., more preferably −5 to 30 ° C.
When the amount is not less than the lower limit and not more than the upper limit of the above range, the cellulose swelling and water absorption in the cellulose-containing material can be increased, and the subsequent hydrolysis reaction can be performed more efficiently.
On the other hand, when the amount is less than the lower limit and exceeds the upper limit of the above range, the cellulose swelling and water absorption in the cellulose-containing material tend to decrease.

In the pretreatment step, the treatment time when contacting the cellulose-containing material and the alkaline aqueous solution can be 0.1 to 120 minutes, preferably 0.1 to 60 minutes, preferably 1 minute to 30 minutes is more preferable.
When the amount is not less than the lower limit and not more than the upper limit of the above range, the cellulose swelling and water absorption in the cellulose-containing material can be increased, and the subsequent hydrolysis reaction can be performed more efficiently.
On the other hand, when the amount is less than the lower limit of the above range, the cellulose swelling and water absorption in the cellulose-containing material tend to decrease. In addition, when the alkali treatment is performed for more than 120 minutes, although depending on the alkali concentration, the degree of change generally decreases, and the swelling and water absorption tend to reach a peak.

In the present invention, the alkali treatment and / or the washing treatment is preferably performed in a saccharification treatment reactor. Here, the “saccharification treatment reactor” refers to a container in which the cellulose-containing material that has undergone the pretreatment step and the aqueous solvent are put into contact in the reaction step described later. As this container, the reaction tank 2 in the cellulose saccharification apparatus 1 mentioned later is mentioned, for example.
By performing the alkali treatment and / or the washing treatment in the saccharification treatment reactor, the reaction step described later can be continuously performed in the same saccharification treatment reactor without moving the cellulose-containing material after the treatment. Therefore, the cellulose saccharification process can be shortened.

  In the pretreatment step, as the method for washing the cellulose-containing material subjected to the alkali treatment with water and / or an acidic aqueous solution, alkali can be washed out from the cellulose-containing material with water and / or an acidic aqueous solution. If there is no particular limitation. For example, a method of washing the cellulose-containing material by immersing it in deionized water and / or an acidic aqueous solution may be adopted, or the cellulose-containing material may be allowed to stand, and deionized water and / or acidic aqueous solution may be used. You may let it pass and wash.

The acidic aqueous solution is not particularly limited as long as it does not inhibit the subsequent hydrolysis reaction. For example, sulfuric acid or the like is preferably used.
The concentration of the acidic aqueous solution is appropriately adjusted depending on the concentration of alkali in the alkali treatment.

  The alkali remaining in the cellulose-containing material after washing with the water and / or acidic aqueous solution is as small as possible so that the pH of the water or acidic aqueous solution contained in the cellulose-containing material is in the vicinity of acidic to neutral. It is desirable that However, when an aqueous alkali solution is used as the aqueous solvent in the subsequent hydrolysis reaction, the alkali may remain.

The following operation can be illustrated as a more specific preprocessing step.
First, in an alkali-resistant container (cheese dyeing machine), 1 kg of cotton is mixed with water and then dehydrated, and 9 L of 4N (15.8 mass%) aqueous sodium hydroxide solution is added to perform the alkali treatment. After a period of time, the aqueous sodium hydroxide solution is drained. Next, deionized water is added and washed with water for 8 hours.

Moreover, the method of using a belt conveyor is mentioned as a pre-processing step. That is, in the cellulose saccharification method of the present invention, it is preferable to perform the alkali treatment, the dehydration treatment, and the washing treatment while loading and transporting the cellulose-containing material on a belt conveyor.
This will be described with reference to FIG. First, the cellulose-containing material 30 is loaded on a belt conveyor 31 and submerged in a first treatment tank 33 containing the alkaline solution 32 to perform the alkali treatment, and then the cellulose-containing material 30 is pulled up. The cellulose-containing material 30 is dehydrated by squeezing between the roller 34 and the roller 35, and then the cellulose-containing material 30 is submerged in the second treatment tank 37 containing the water or the acidic aqueous solution 36. The cellulose-containing material 40 that has undergone the alkali treatment and the washing treatment is obtained by pulling up the cellulose-containing material 30 and squeezing between the roller 38 and the roller 39.

According to the method of this pretreatment step, the alkali treatment and the washing treatment can be performed as a series of flow operations while smoothly transporting the cellulose-containing material. Further, by dehydrating the cellulose-containing material that has undergone the alkali treatment with a roller, the amount of the alkaline solution brought into the washing solution can be reduced, and an efficient washing treatment can be performed. At this time, since the composition of the cleaning solution (the water or the acidic aqueous solution) is difficult to change, the frequency of replacing the cleaning solution in the second treatment tank can be reduced. Moreover, if the dehydrated alkaline solution is returned to the first treatment tank and reused, the environmental load can be reduced.
Similarly, by dehydrating the cellulose-containing material that has undergone the washing treatment with a roller, the amount of the washing solution brought into the aqueous solvent in the subsequent reaction step can be reduced. Moreover, if the dehydrated cleaning solution is returned to the second treatment tank and reused, the environmental load can be reduced.

The cellulose-containing material 40 that has undergone the pretreatment step is used in the subsequent reaction step.
In addition, in FIG. 2, although the case where two processing tanks were connected by the belt conveyor was shown, when using multiple types of solutions in the said alkali treatment and the said washing | cleaning process, a processing tank is prepared about each solution. do it. According to the belt conveyor system, a necessary number of processing tanks can be connected. Therefore, the cellulose-containing material can be transported to each treatment tank and processed efficiently as a series of flow operations.

<Reaction step>
The aqueous solvent in the reaction step is preferably pure water or an aqueous solution having a pH of 7 or less. Examples of the aqueous solution having a pH of 7 or less include ozone water, hydrogen peroxide solution, low-concentration sulfuric acid, hydrochloric acid, and weak acids such as carbonated water and citric acid aqueous solution.
The ozone water and the hydrogen peroxide solution are finally decomposed into water and oxygen, and therefore, when these solutions are discarded, the environmental load is small, which is preferable.

Further, the aqueous solvent may be a low concentration alkaline aqueous solution.
The kind of the alkaline aqueous solution is not particularly limited, and examples thereof include sodium hydroxide and aqueous ammonia.
The concentration of the acid or aqueous alkali solution in the reaction step is preferably 0.001 to 1.0N, more preferably 0.005 to 0.3N, and still more preferably 0.01 to 0.1N.
When the concentration is in the above range, cellulose can be efficiently hydrolyzed. If it exceeds the upper limit of the above range, cellulose or glucose as a product may be excessively decomposed.

The concentration of the ozone water is preferably 1.0 ppm to 200 ppm, more preferably 5.0 to 100 ppm, and even more preferably 10 to 50 ppm.
Within the above range, cellulose can be efficiently hydrolyzed. If it exceeds the upper limit of the above range, cellulose or glucose as a product may be excessively decomposed.

The concentration of the hydrogen peroxide solution is preferably 0.1 wt% to 30 wt% (mass%), more preferably 0.5 wt% to 20 wt%, and even more preferably 1.0 wt% to 10 wt%.
Within the above range, cellulose can be efficiently hydrolyzed. If it exceeds the upper limit of the above range, cellulose or glucose as a product may be excessively decomposed.

  The method (operation A) for bringing the cellulose-containing material (pretreated cellulose-containing material) that has undergone the pretreatment step into contact with the aqueous solvent is not particularly limited. A method of stirring the pretreated cellulose-containing material and the aqueous solvent to obtain a mixture may be adopted, or the pretreated cellulose-containing material is allowed to stand, and the aqueous solvent is allowed to flow through and contact. May be. For example, when the cellulose saccharification apparatus shown in FIG. 1 is used, an appropriate amount of the pretreated cellulose-containing material is charged into the reaction tank 2, and the aqueous solvent 5 charged into the storage tank 4 is pumped up via the pump 6 and the liquid feeding pipe 7. By sending the solution to the reaction tank 2, the pretreated cellulose-containing material and the aqueous solvent 5 can be mixed in the reaction tank 2 to obtain a mixture 8.

In the heat treatment and pressure treatment (operation B), the method for heat-treating the pretreated cellulose-containing material and the aqueous solvent is not particularly limited. For example, when the cellulose saccharification apparatus 1 shown in FIG. 1 is used, the mixture 8 in the reaction tank 2 can be heat-treated at a predetermined temperature by the heating unit 10 provided to heat the entire reaction tank 2.
Moreover, in the preheating part 11 provided in the middle of the liquid feeding pipe 7, the aqueous solvent 5 previously heated to a predetermined temperature is fed to the reaction tank 2 and added to the pretreated cellulose-containing material or mixture 8. Thus, the mixture 8 can be heat-treated.
As a heat source in the heating part 10 or the preheating part 11, a well-known thing using a heater (electric heater) or a boiler can be used.

As a temperature range of the said heat processing, 100-300 degreeC is preferable, 120-250 degreeC is more preferable, 140-200 degreeC is further more preferable.
When it is at least the lower limit of the above range, the conversion from cellulose to saccharide can be increased, and the glucose content in the saccharide can be increased.
When the amount is not more than the upper limit of the above range, excessive decomposition of saccharides can be reduced or suppressed. Moreover, since the burning of the raw material cellulose and the generation of tar-like substances can be reduced or suppressed, the saccharification reaction is continuously performed by sequentially adding the pretreated cellulose-containing material without washing the reaction tank 2. It can be carried out.

Here, in the specification of the present invention, the conversion rate of cellulose refers to the ratio of the mass of reacted cellulose to the mass of cellulose contained in the raw material. Moreover, the yield of saccharide means the ratio of the mass of the saccharide obtained by saccharification reaction with respect to the mass of the cellulose contained in a raw material. Moreover, the selectivity of saccharide means the ratio of the mass of the saccharide obtained by saccharification reaction with respect to the mass of the said reacted cellulose.
The cellulose saccharification method of the present invention produces water-soluble oligosaccharide and / or glucose. In the present invention, the water-soluble oligosaccharide obtained by hydrolyzing cellulose refers to a water-soluble cellooligosaccharide having a molecular structure in which about 2 to 20 molecules of glucose are condensed and connected. Cellulase may be added to the reaction product obtained in the present invention.

In the heat treatment and pressure treatment (operation B), the method for pressure treating the pretreated cellulose-containing material and the aqueous solvent is not particularly limited. For example, when the cellulose saccharification apparatus 1 shown in FIG. 1 is used, since the back pressure valve 13 is provided in the liquid feeding pipe 12 on the downstream side of the reaction tank 2, the aqueous solvent 5 is reacted via the pump 6 and the liquid feeding pipe 7. By sending the liquid to the tank 2, the inside of the reaction tank 2 can be increased to a predetermined pressure.
In addition, a pressure treatment for increasing the reaction tank 2 to the vapor pressure of the aqueous solvent 5 can be performed by performing a heat treatment with the heating unit 10 in a state where the reaction tank 2 is sealed.

The pressure range of the pressure treatment is preferably 0.1 MPa to 30 MPa, more preferably 0.5 MPa to 20 MPa, and further preferably 1.0 MPa to 10 MPa.
When it is at least the lower limit of the above range, the conversion from cellulose to saccharide can be increased, and the glucose content in the saccharide can be increased.
Moreover, the excessive decomposition of saccharide | sugar can be reduced or suppressed as it is below the upper limit of the said range.

As described above, by subjecting the pre-treated cellulose-containing material and the aqueous solvent to contact (mixture) by heat treatment and pressure treatment, the saccharification reaction of cellulose in the mixture is promoted and efficiently performed. Conversion from cellulose to sugar occurs to produce water-soluble oligosaccharides and / or glucose.
The time of the heat treatment and the pressure treatment varies depending on the combination of the amount ratio of the pretreated cellulose-containing material and the aqueous solvent, the temperature of the heat treatment, and the temperature of the pressure treatment, but the temperature range and the pressure If it is in the range, the cellulose contained in the raw material can be efficiently saccharified in about 0.5 minutes to 300 minutes.

  The method of operation (operation C) for obtaining an aqueous solution containing a water-soluble oligosaccharide or glucose is not particularly limited. For example, when the cellulose saccharification apparatus 1 shown in FIG. 1 is used, unreacted cellulose-containing material and produced water-soluble oligosaccharide and / or glucose are contained in the reaction tank 2 that has undergone the operations A and B. Aqueous solutions may be present. At this time, when the aqueous solvent 5 is fed from the storage tank 4 to the reaction tank 2 via the pump 6 and the liquid feeding pipe 7, the pressure in the reaction tank 2 is controlled by the back pressure valve 13 provided downstream of the reaction tank 2. The aqueous solution containing the product in the reaction tank 2 can be separated from the unreacted cellulose-containing material and extracted from the discharge port 14 to the recovery tank 15 while maintaining a predetermined value. At this time, the unreacted cellulose-containing material is prevented from flowing out to the discharge port 14 by the filter 16 provided on the downstream side of the reaction tank 2. Similarly, a filter 16 is provided on the upstream side of the reaction tank 2 to prevent the unreacted cellulose-containing material or the mixture 8 from flowing backward. The aqueous solution containing the product extracted through the filter 16 on the downstream side of the reaction tank 2 is cooled by the cooling unit 18. Thereby, it can prevent that a product is kept at high temperature unnecessarily and is overdecomposed. The cooling method is not particularly limited, and a known method using a reciprocating compressor or the like can be applied.

  When the cellulose saccharification apparatus 1 as shown in FIG. 1 is used, the pretreated cellulose-containing material and the aqueous solvent 5 are mixed, and for the reaction tank 2 in which the heat treatment and the pressure treatment are performed, Furthermore, the aqueous solution 17 containing the water-soluble oligosaccharide or glucose can be obtained from the reaction tank 2 by flowing out through the filter while introducing the aqueous solvent 5. That is, for example, by using the cellulose saccharification apparatus 1 shown in FIG. 1, a continuous cellulose saccharification method in which the operation A, the operation B, and the operation C are performed simultaneously and continuously can be performed.

  More specifically, the aqueous solvent 5 is pumped from the storage tank 4 by the pump 6, heated by the preheating part 11, then sent to the reaction tank 2 and subjected to pressure treatment, and heated by the heating part 10. Process. At the same time, the aqueous solution 17 containing the product obtained by hydrolyzing cellulose is discharged from the reaction tank 2 through the filter 16 while controlling the back pressure valve 13 to maintain the pressure in the reaction tank 2 at a predetermined level. Thus, it can be recovered from the discharge port 14.

  Further, in FIG. 1, only one reaction tank 2 is provided, but by providing two reaction tanks 2 and 2 ′ in parallel downstream of the preheating unit 11, the cellulose saccharification reaction is performed in one reaction tank 2. In this case, the other reaction tank 2 ′ is temporarily removed from the line by switching the valve, etc., and re-filled with the pretreated cellulose-containing material, and the reaction tank 2 ′ is connected to the line again. The cellulose saccharification reaction in the cellulose saccharification apparatus 1 can be continued even when the pretreated cellulose-containing material is filled. According to this continuous method, the operation A, the operation B, and the operation C can be performed simultaneously and continuously.

When the continuous system is used as described above, the product does not stay in the reaction tank 2 for a long time (for example, more than 1 hour), so that it is possible to reduce or suppress the product from being excessively decomposed. . On the other hand, in the case of a so-called batch system instead of a continuous system, the operation A, the operation B, and the operation C are performed in this order. The saccharide produced at the initial stage of the reaction may be exposed to excessive heat treatment and pressure treatment, and the rate of overdecomposition may increase. As a by-product generated by the excessive decomposition, for example, 5-hydroxymethylfurfural (5-HMF) can be mentioned.
Therefore, the cellulose saccharification method of the present invention is preferably the continuous method from the viewpoint of reducing or suppressing the excessive decomposition of the product saccharide.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these examples.

[Example 1]
50 g of cotton containing cellulose and 2 kg of 4N (15.8 mass%) sodium hydroxide aqueous solution were mixed in a glass beaker (3 L) and contacted at 20 ° C. for 30 minutes.
Subsequently, the sodium hydroxide aqueous solution was removed from the beaker, the deionized water was added and the alkali-treated cellulose-containing material was washed with water and allowed to stand for 8 hours.
Next, the cellulose saccharification apparatus shown in FIG. 1 was used to continuously saccharify the cellulose contained in the cotton. First, 10.0 g of the alkali-treated cotton was put into the reaction tank 2, and the pure water prepared in the storage tank 4 was filled in the apparatus path and the reaction tank 2, and then pure water was supplied through the liquid feeding pipe 7. The liquid was fed into the reaction tank 2 by the pump 6 at a rate of 20 ml / min, and the back pressure valve 13 was controlled to adjust the pressure in the reaction tank 2 to 5 MPa. Then, the heater 10 and the preheating part 11 were controlled so that the inside of the reaction tank 2 might be 220 degreeC, and the heating was started.
After reaching the set temperature (220 ° C.), while adjusting the back pressure valve 13 and maintaining the pressure in the reaction tank 2, pure water is sent to the reaction tank 2 at 3 ml / min by the pump 6, while being discharged from the outlet 14. An aqueous solution containing the product was collected for 300 minutes.

As a result of the experiment, 1.0 g of cotton remained after the saccharification reaction (the mass of cotton remaining after the saccharification reaction was 1.0 g). That is, the conversion rate of cellulose (conversion rate of cellulose (mass%) = reacted cellulose mass / raw material cellulose mass) was 90%. Moreover, the product contained in the obtained sample solution was analyzed by HPLC.
Table 1 shows the yields of saccharides, aldehydes, furans, and organic acids (weight ratio of raw material to product).

  As a result of HPLC analysis, 90% of the obtained saccharides were glucose. That is, the selectivity for saccharides was 90%.

[Comparative Example 1]
The experiment was performed in the same manner as in Example 1 except that the alkali treatment in Example 1 was not performed and 10.0 g of untreated cotton was used as a raw material.

As a result of the experiment, 9.0 g of cotton remained after the saccharification reaction. That is, the conversion rate of cellulose was 10%. Moreover, the product contained in the obtained sample solution was analyzed by HPLC.
Table 2 shows the yields of saccharides, aldehydes, furans, and organic acids (raw material to product weight ratio%).

It is clear that the cellulose conversion is very low when the alkali treatment is not performed.
As a result of HPLC analysis, most of the obtained saccharides were glucose. Moreover, the selectivity of saccharides was 100%.

  From the above results, the cellulose saccharification method according to the present invention has a higher cellulose conversion rate, saccharide (glucose) yield, and saccharide selectivity than the method of Comparative Example 1, and the glucose content in the saccharide is higher. It was confirmed that it was extremely high.

  The cellulose saccharification method of the present invention can be widely used for producing saccharides from raw materials containing cellulose.

DESCRIPTION OF SYMBOLS 1 ... Cellulose saccharification apparatus, 2 ... Reaction tank, 4 ... Storage tank, 5 ... Aqueous solution, 6 ... Pump, 7 ... Liquid feeding pipe, 8 ... Mixture, 10 ... Heating part, 11 ... Preheating part, 12 ... Liquid feeding pipe, DESCRIPTION OF SYMBOLS 13 ... Back pressure valve, 14 ... Discharge port, 15 ... Collection tank, 16 ... Filter, 17 ... Aqueous solution containing a product, 18 ... Cooling part.

Claims (8)

A method of hydrolyzing cellulose to saccharify,
An alkali treatment is performed in which the cellulose-containing material is brought into contact with an aqueous alkali solution, and the cellulose-containing material is washed with water and / or an acidic aqueous solution, and then the cellulose-containing material is brought into contact with an aqueous solvent, followed by heat treatment and pressure treatment. A cellulose saccharification method comprising obtaining an aqueous solution containing a water-soluble oligosaccharide or glucose.   The cellulose saccharification method according to claim 1, wherein the heat treatment is in a temperature range of 100C to 300C.   The cellulose saccharification method according to claim 1 or 2, wherein the pressure treatment is in a pressure range of 0.1 MPa to 30 MPa.   In the alkali treatment, the cellulose-containing material is brought into contact with the alkaline aqueous solution of 0.1 to 20 N in a temperature range of −10 ° C. to 50 ° C. for a time range of 0.1 to 120 minutes. The cellulose saccharification method as described in any one of Claims 1-3.   The operation of bringing the cellulose-containing material into contact with the aqueous solvent, the heat treatment and pressure treatment, and the operation of obtaining an aqueous solution containing the water-soluble oligosaccharide or glucose are performed simultaneously and continuously. The cellulose saccharification method as described in any one of claim | item 1 -4.   The cellulose saccharification method according to any one of claims 1 to 5, wherein cellulose in the cellulose-containing material constitutes cotton or paper.   The cellulose saccharification method according to any one of claims 1 to 6, wherein the alkali treatment is performed in a saccharification treatment reactor. The cellulose saccharification method according to any one of claims 1 to 7, wherein the alkali treatment, the dehydration treatment, and the washing are performed while the cellulose-containing material is loaded and transported on a belt conveyor.

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