JP4277603B2 - Method for hydrolysis of polysaccharide substances - Google Patents

Description

【表２】

【００４８】
【発明の効果】
本発明の多糖類物質の加水分解方法によれば、キノン類化合物の存在により、多糖類の加水分解を促進し、オリゴ糖類の還元末端やグルコースの分解断片化などの副反応を有効に抑え、短時間で効率よく、また、酸加水分解の場合に見られる反応器の腐食なしに、グルコースなどの糖類を得ることができる。
【図面の簡単な説明】
【図１】 異なる圧力における水のイオン積（Ｋｗ）の温度依存性を示すグラフである。
【図２】 ４０ＭＰａの圧力における水のイオン積（Ｋｗ）の温度依存性を示すグラフである。
【図３】 超臨界水および亜臨界水処理における微結晶セルロース（アビセル）、セロビオースおよびグルコースの分解速度定数のアレニウスプロット（圧力は４０ＭＰａ）である。
【図４】 本発明を実施するために構成される装置例を示す概略説明図である。
【図５】 本発明の実施の実験フローチャートである。
【図６】 ベンゾキノン存在下でのセルロースの反応生成物の収率に対する反応時間および反応温度の影響を示すグラフである。
【図７】 ベンゾキノン無添加でのセルロースの反応生成物の収率に対する反応時間の影響を示すグラフである。
【図８】 実施例１および比較例１における水可溶分の高速液体クロマトグラムである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for converting a polysaccharide-containing substance existing in large quantities on the earth into a useful substance such as a monosaccharide in a high yield in a short time. More specifically, the present invention uses glucose in the subcritical state or supercritical state as a solvent, and selectively and efficiently hydrolyzes a polysaccharide substance such as cellulose to produce glucose and / or oligosaccharides in a high yield. On how to do.
[0002]
[Prior art]
Energy and environmental problems due to fossil resource depletion and global warming are the most serious problems in the 21st century. In order to solve these problems, it is necessary to find abundant resources that are environmentally friendly and oily. One of the most promising of these is biomass resources. Cellulose is the one that constitutes this biomass resource and boasts the largest amount on the earth, and there is greater expectation than ever for cellulose. That is, in addition to the use of cellulose as a chemical industrial raw material, various technological developments aimed at use as an energy resource have attracted attention. Among them, production of glucose from cellulose is extremely important for effective utilization of cellulose. For example, ethanol production from glucose, fermentation to lactic acid, and conversion to biodegradable polymers such as polylactic acid have recently attracted attention. There are basically three known methods for producing glucose from cellulose: acid hydrolysis, enzymatic hydrolysis, and recently developed hydrolysis using supercritical water. As will be described later, it is difficult to say that the method is effective as a method for efficiently and mass-producing glucose.
[0003]
The acid hydrolysis method is divided into a dilute acid method and a concentrated acid method depending on the acid concentration. In the dilute acid method, both the temperature and pressure are high, and there are problems such as equipment corrosion due to the added acid and removal of acid from the product. In order to avoid such inconvenience, if the acid concentration is suppressed, the glucose production rate Has the disadvantage of becoming lower. In the concentrated acid method, since the temperature and pressure are low, an inexpensive reactor material such as glass fiber FRP can be used and the yield of glucose is high, but the reaction time is long and economically effective acid recovery. There is a disadvantage that there is no method.
[0004]
The enzymatic hydrolysis method is not used as an industrial production technique because the reaction rate is slow and the price of the enzyme is high.
[0005]
On the other hand, recently, in order to solve the above problems, a method has been proposed in which cellulose is hydrolyzed using subcritical or supercritical water to produce oligosaccharide or monosaccharide glucose (Patent Document 1 and 2). This technology utilizes the characteristics of supercritical water, and can completely decompose cellulose into oligosaccharides and monosaccharides in a treatment time of seconds or less. However, the yield of useful glucose was only around 20%. This is because the oligosaccharides and monosaccharides produced by hydrolysis change into secondary products by various thermal decomposition reactions under high temperature reaction conditions. According to the experiments by the present inventors, when the reaction temperature is 350 ° C. or higher, the ionic product of water decreases, so that free radical reactions such as thermal decomposition increase. As a result, the reducing end of the oligosaccharide and glucose are decomposed and converted into a fragmented product such as glycol aldehyde, and the yield of glucose decreases. As a method for suppressing these side reactions, it was proposed to increase the pressure, but the cost of the apparatus increased, and the yield of glucose increased only slightly (see Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 5-31000
[Patent Document 2]
Japanese Patent Laid-Open No. 10-327900
[Problems to be solved by the invention]
The present invention has been made under these circumstances, and promotes the hydrolysis reaction of polysaccharides and suppresses side reactions, and efficiently produces useful sugars such as glucose from substances containing polysaccharides such as cellulose. It aims to provide a way to do.
[0009]
[Means for Solving the Problems]
The present invention has been made to achieve the above object, and is characterized in that a quinone compound is allowed to coexist in a reaction system in hydrolyzing a polysaccharide substance with subcritical or supercritical water. It relates to a method for the hydrolysis of substances.
[0010]
According to the method for hydrolyzing a polysaccharide substance of the present invention, the presence of a quinone compound further promotes the hydrolysis of the polysaccharide, and effectively suppresses side reactions such as the reducing end of the oligosaccharide and the degradation fragmentation of glucose. The yield of sugars such as glucose can be significantly increased.
[0011]
The polysaccharide substances targeted by the present invention include not only cellulose, which is a representative example of polysaccharides, but also lignocellulose resources and organic compounds containing polysaccharides such as hemicellulose, starch, chitin and chitosan, and wastes thereof. . These polysaccharides may be a combination of two or more.
[0012]
Oligosaccharides and / or monosaccharides can be produced by the polysaccharide substance hydrolysis method of the present invention, but it is preferable to produce monosaccharides, particularly glucose. According to the present invention, glucose can be obtained in a yield of up to 50% or more and close to 80% if conditions are selected. Furthermore, when cellobiose and oligosaccharides are also added, a saccharide product can be obtained with a yield of 97%.
[0013]
Among the quinone compounds used in the present invention, benzoquinone exhibits a great effect and is particularly preferable.
[0014]
The reaction temperature for the hydrolysis is preferably in the range of 150 to 500 ° C, more preferably 180 to 350 ° C. The reaction pressure for hydrolysis is preferably 1.0 to 100 MPa, more preferably 2 to 50 MPa.
[0015]
It is also preferred that an acid is allowed to coexist with the quinone compound in the reaction system. The coexistence of the acid can reduce the amount of quinone added and allows the reaction to proceed more rapidly.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a method for hydrolyzing a polysaccharide substance such as cellulose in the presence of a quinone compound with water in a subcritical state or a supercritical state to convert it into oligosaccharides and / or monosaccharides. It is.
[0017]
The theoretical basis for the action and effect of quinone in subcritical or supercritical water has not yet been elucidated, but can be considered as follows. Subcritical or supercritical water can easily and significantly change its dielectric constant and ionic product (Kw) by controlling temperature and pressure. FIG. 1 is a graph showing the temperature dependence of water ion product (Kw) at various pressures. The higher the pressure, the higher the ion product (Kw) is maintained up to a higher temperature region, and even at a considerably high temperature. It can be expected to form a region for good ionic reaction (hydrolysis reaction). However, if the pressure is constant, the ion product decreases with increasing temperature. When the pressure is 40 MPa, it can be seen that the ion product decreases rapidly when the temperature is 350 ° C. or higher (see FIG. 2). As a result, side reactions such as thermal decomposition become violent, and selectivity of glucoside bond cleavage is reduced. In FIG. 3, the pressure was fixed at 40 MPa, and glucose, cellobiose and microcrystalline cellulose (Avicel) were used as model compounds to examine cellulose solubilization reaction, glucoside bond cleavage reaction, oligosaccharide reducing end and glucose decomposition reaction, respectively. Results are shown. As can be seen from FIG. 3, when the temperature reached 350 ° C., the decomposition reaction of monosaccharide (glucose) or oligosaccharide showed a larger reaction rate constant than the cleavage reaction of glucoside. This is considered to be a cause of a decrease in glucose yield. Therefore, under normal supercritical water conditions, cellulose is greatly hydrolyzed, but at the same time, side reactions such as thermal decomposition proceed rapidly, so the yield of hydrolysis products such as glucose is not high. Therefore, it has been clarified in the present invention that the presence of a quinone compound can suppress side reactions such as thermal decomposition and increase the selectivity of hydrolysis.
[0018]
Polysaccharide substances that can be used in the present invention are not particularly limited, but polysaccharides that exist in nature, such as cellulose, hemicellulose, starch, chitin, chitosan, and other organic resources containing these polysaccharides, For example, wood, bamboo, kenaf, bagasse, rice straw, etc., which are lignocellulosic resources, and wood fibers, wood chips, veneer scraps, pulp, waste paper, etc., rice, wheat, corn, etc. Examples include cereals, potatoes, sweet potatoes such as sweet potatoes, and biomass materials contained in general household waste. Among them, cellulose and cellulose-containing materials such as wood, pulp, and waste paper are more preferable from the viewpoint of the abundance of raw materials. Cellulose is preferable in that it hardly causes by-products derived from non-sugar components such as lignin in the reaction product, and the separation step can be omitted.
[0019]
According to the method of the present invention, polysaccharides such as cellulose can be converted into oligosaccharides and / or monosaccharides in a short time and with good selectivity. It is particularly preferable because it is a raw material for chemicals, polymer materials and bioenergy.
[0020]
The quinone compound is not particularly limited, and examples thereof include p-benzoquinone, o-benzoquinone, 2-meso-6-mesyl-1,4-benzoquinone, and plastoquinone. Among them, p-benzoquinone is more preferable because it has particularly large effects of promoting hydrolysis reaction and suppressing thermal decomposition reaction.
[0021]
The addition amount of the quinone compound is preferably 0.001 to 5 wt%, more preferably 0.01 to 2 wt%, and still more preferably 0.05 to 1 wt% with respect to the total reaction system. If the amount added is less than 0.001 wt%, the effect of suppressing thermal decomposition is insufficient, and even if it exceeds 5 wt%, there is no change in effect, which is unnecessary.
[0022]
In the present invention, when a polysaccharide or a polysaccharide-containing substance is hydrolyzed with water in a subcritical state or a supercritical state in the presence of a quinone compound, and converted to an oligosaccharide or / and a monosaccharide, The method and apparatus are not particularly limited, and known methods and apparatuses can be applied. For example, a batch-type reaction method in which a polysaccharide substance, water and quinones are put into an autoclave reactor and heated, and a fixed-bed reactor is filled with a polysaccharide substance, which contains a predetermined amount of a quinone compound. It consists of a fixed-bed type reaction method in which pressurized hot water is continuously passed through to hydrolyze the polysaccharide, and the resulting reaction product flows out of the system together with hot water, including a polysaccharide substance, a quinone compound, and water. Examples include a flow reaction method in which the slurry is continuously passed through the reactor. Among them, the flow-type reaction method is more preferable because the reaction time can be easily controlled.
[0023]
The subcritical or supercritical water used in the present invention has a temperature of 150 to 500 ° C. and a pressure of 1.0 to 100 MPa. Water in the range of temperature: 180 to 350 ° C. and pressure: 2 to 50 MPa is more preferable. If the temperature and pressure are too low, the polysaccharide hydrolysis reaction rate is low and the production efficiency is low. If the temperature and pressure are too high, reaction control is difficult and the yield tends to decrease.
[0024]
In the present invention, an acid such as sulfuric acid, hydrochloric acid or oxalic acid, or an acidic salt substance such as copper sulfate or aluminum chloride can be added to subcritical or supercritical water in a concentration range of 1% or less. . This is effective in reducing the required amount of quinone compound and improving the hydrolysis reaction rate. Considering the corrosion of the equipment, the effect of addition, post-treatment, etc., a concentration of 0.01% or less is more preferable.
[0025]
The reaction time of the polysaccharide material with water in the subcritical or supercritical state varies depending on the reactor, reaction temperature, molecular weight and crystallinity of the polysaccharide material, and the type and amount of quinone used, In some cases, if the pressurized hot water is in the range of 250 to 350 ° C., it is about 0.3 to 300 seconds. However, when using a fixed bed reactor through which hot water is circulated, it is necessary to pass water for several minutes in order to drive out the water-soluble component out of the reaction system. When a batch type reactor is used, the reaction time may be longer because the heating time to a predetermined temperature depends on the size of the reactor.
[0026]
The hot water flowing out from the reactor is desirably cooled immediately in order to suppress secondary decomposition of water-soluble components such as glucose and oligosaccharides contained therein.
[0027]
FIG. 4 is a schematic explanatory diagram showing an example of an apparatus configured to carry out the present invention. The suction side of the high-pressure feed pump (12) is connected to the distilled water tank (10) that stores distilled water. The discharge port of the high-pressure feed pump (12) is connected to a conduit that reaches the reaction tube (18) through the heater (16). High-pressure hot water heated to a predetermined temperature by the heater (16) is introduced into the reaction tube (18).
[0028]
On the other hand, in the slurry tank (20), distilled water, a polysaccharide substance such as cellulose, benzoquinone, and the like are mixed in a predetermined amount and made into a slurry by stirring. The obtained slurry is sent to a circulation line by a slurry pump (22a). The slurry in the circulation line is circulated by two circulation pumps (22c). This circulation prevents sedimentation of the slurry inside the line and keeps the slurry in a uniform state. The circulation line has a slurry feed pump (22b), and extrudes the slurry introduced into the pump (22b) at a predetermined pressure by moving the piston.
[0029]
Thus, at the inlet of the reaction tube (18), the high-temperature and high-pressure hot water that has passed through the heater (16) and the slurry from the slurry feed pump (22b) merge.
[0030]
When the mixture of pressurized hot water and slurry passes through the inside of the reaction tube (18), a reaction in a high temperature and high pressure state occurs. As a result, the polysaccharide is hydrolyzed and a water-soluble product such as glucose is obtained.
[0031]
The high-temperature reaction solution coming out of the reaction tube (18) is combined with the room-temperature distilled water fed from the distilled water tank (30) by the three high-pressure feed pumps (32), and further passes through the cooler (19). Is cooled quickly. The cooler (19) is composed of a heat exchanger that circulates cooling water through a jacket covering a conduit through which the reaction liquid from the reaction tube (18) flows.
[0032]
The reaction solution coming out of the cooler (19) is guided to the sample reservoir (40) through the back pressure adjusting valve (38), and the pressure of the reaction system is adjusted by adjusting the back pressure adjusting valve (38).
[0033]
This device includes a pressure gauge (P) for measuring the pressure of the inlet of the heater (16), the slurry circulation line, and the cooling water feed line, the inlet and outlet of the reaction tube (18), and the cooler (19). Thermometers (T) are provided to measure the temperature at the outlet of each, and these measurement data are sent to a control unit (not shown) formed by a microcomputer, etc., and the control unit responds to these measurement results To control the reaction temperature and the reaction pressure, respectively.
[0034]
By adjusting the flow rate and the temperature of the heated water, the temperature in the reaction tube (18) is maintained at 180 to 500 ° C., and the pressure is adjusted to 1 to 50 MPa by adjusting the back pressure adjustment valve (38). Maintained. The residence time in the reaction tube (18) can be arbitrarily adjusted by changing the volume of the tube (18) or changing the flow rate.
[0035]
The reaction solution is not only mixed with distilled water at room temperature at the outlet of the reaction tube (18) but also cooled by heat exchange in the cooler (19). The amount of distilled water mixed with the reaction solution is in the range of 2 to 5 times that of the reaction solution. It is preferable that the temperature of the reaction liquid discharged from the reactor (18) rapidly decreases to about 100 ° C.
[0036]
The slurry residence time τ in the reaction tube (18) is expressed as follows: the capacity of the reaction tube (18) is V, the mass flow rate at room temperature is F, the water density at the reaction temperature / reaction pressure is ρ (T, P). If
τ = V · ρ (T, P) / F
It is given by
[0037]
Here, the method for producing glucose according to the present embodiment will be described with reference to the flowchart of FIG. A slurry is prepared by mixing microcrystalline cellulose (Avicel) as a raw material and benzoquinone as an additive in distilled water at a predetermined concentration. By bringing this slurry into contact with supercritical or subcritical water in a reaction tube for a predetermined time, cellulose hydrogen bonds are partially broken, crystals break down in supercritical or subcritical water, and hydrolysis occurs. The reaction proceeds.
[0038]
In the presence of benzoquinone, it is possible to produce glucose in a short time and in a high yield by suppressing side reactions such as thermal decomposition of the generated oligosaccharide and glucose and accelerating the hydrolysis reaction.
[0039]
After a predetermined reaction time has elapsed, the obtained reaction solution is discharged from the reaction tube, combined with cooling water, and stopped by external cooling through the cooling tube, and then discharged through a back pressure adjustment valve. Return to normal pressure.
[0040]
The reaction solution is allowed to stand at normal pressure at room temperature or lower for a predetermined time. When a white precipitate is formed, the precipitate is separated by filtration or the like and dried, and then the yield is obtained.
[0041]
On the other hand, the water-soluble part identifies and quantitatively analyzes the product by high performance liquid chromatography (HPLC). Thereby, the yield of each product is determined.
[0042]
【Example】
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples. Hereinafter, the results of actual processing performed by the apparatus shown in FIG. 4 will be described. The volume of the reaction tube 18 (inner diameter 0.2 cm, length 1.9 cm) is 0.238 cm ³ , the flow rate of pressurized hot water is 5 × Q, and the flow rate of cooling water with respect to the flow rate Q of slurry. Is 25 × Q.
[0043]
Example 1
A slurry composed of microcrystalline cellulose (25 g), benzoquinone (5 g) and distilled water (800 ml) and 5 times pressurized hot water were mixed, and the residence time was 0.3 under the conditions of a temperature of 350 ° C. and a pressure of 40 MPa. The treatment was performed while changing the time from 0.4, 0.5, 0.6, and 0.7 seconds. Five treatment liquids having different treatment times were obtained. The results of analyzing the treatment liquid are shown in FIG. The horizontal axis in FIG. 6 is the treatment time (seconds), and the vertical axis is the product yield (%) based on the starting amount of microcrystalline cellulose. As apparent from FIG. 6, under the processing conditions of a temperature of 350 ° C. and a pressure of 40 MPa, the highest glucose yield (80.2%) was obtained with a processing time of 0.6 seconds. It was also confirmed that the cellulose almost disappeared in a short time of 0.3 seconds.
[0044]
Comparative Example 1
The treatment was performed under exactly the same conditions as in Example 1 except that benzoquinone was not used. The obtained analysis results are shown in FIG. Compared to Example 1, when benzoquinone was not added, the amount of glucose produced was only 15% or less regardless of changes in treatment temperature and time. In addition, cellulose was found not to react until a treatment time of 0.5 seconds.
[0045]
Example 2
The treatment was performed under exactly the same conditions as in Example 1 except that the treatment temperature was 327 ° C. and the treatment time was 1.0 second. The obtained analysis results are shown in Table 1. Although the treatment speed was reduced by lowering the treatment temperature, a high glucose yield was obtained by extending the time.
[0046]
FIG. 8 is a high-performance liquid chromatogram of water-soluble components obtained in Example 1 and Comparative Example 1. As shown in this figure, the water-soluble part is composed of secondary decomposition products such as oligosaccharides, glucose, levoglucosan and 5-hydroxymethylfurfural (5-HMF). Under the same processing conditions, when benzoquinone was not added, oligosaccharides and fragmentation products were considerably increased. From the above results, it has been clarified that the presence of benzoquinone suppresses secondary decomposition of oligosaccharides and glucose and accelerates hydrolysis, and as a result, glucose can be obtained in high yield.
[0047]
[Table 1]

[Table 2]

[0048]
【The invention's effect】
According to the method for hydrolyzing a polysaccharide substance of the present invention, the presence of a quinone compound promotes the hydrolysis of the polysaccharide, and effectively suppresses side reactions such as the reducing end of the oligosaccharide and the degradation fragmentation of glucose, Sugars such as glucose can be obtained efficiently in a short time and without the corrosion of the reactor seen in the case of acid hydrolysis.
[Brief description of the drawings]
FIG. 1 is a graph showing the temperature dependence of the ionic product (Kw) of water at different pressures.
FIG. 2 is a graph showing the temperature dependence of the ion product (Kw) of water at a pressure of 40 MPa.
FIG. 3 is an Arrhenius plot (pressure is 40 MPa) of decomposition rate constants of microcrystalline cellulose (Avicel), cellobiose and glucose in supercritical water and subcritical water treatment.
FIG. 4 is a schematic explanatory diagram showing an example of an apparatus configured to carry out the present invention.
FIG. 5 is a flowchart of an experiment for carrying out the present invention.
FIG. 6 is a graph showing the influence of reaction time and reaction temperature on the yield of a reaction product of cellulose in the presence of benzoquinone.
FIG. 7 is a graph showing the effect of reaction time on the yield of a reaction product of cellulose without addition of benzoquinone.
8 is a high-performance liquid chromatogram of a water-soluble component in Example 1 and Comparative Example 1. FIG.

Claims (8)

A method for hydrolyzing a polysaccharide substance, comprising causing a quinone compound to coexist in a reaction system when hydrolyzing a polysaccharide substance with water in a subcritical state or a supercritical state. The method for hydrolyzing a polysaccharide substance according to claim 1, wherein the polysaccharide substance is cellulose, hemicellulose, starch, chitin or a substance containing at least one of them. The method for hydrolyzing a polysaccharide substance according to claim 1 or 2, wherein the oligosaccharide and / or monosaccharide is produced by hydrolysis. The method for hydrolyzing a polysaccharide substance according to claim 3, wherein the monosaccharide is glucose. The method for hydrolyzing a polysaccharide substance according to any one of claims 1 to 4, wherein the quinone compound is benzoquinone. The method for hydrolyzing a polysaccharide substance according to any one of claims 1 to 5, wherein the reaction temperature is in the range of 150 to 500 ° C. The method for hydrolyzing a polysaccharide substance according to any one of claims 1 to 6, wherein the reaction pressure is in the range of 1.0 to 100 MPa. The method for hydrolyzing a polysaccharide substance according to any one of claims 1 to 7, wherein an acid is allowed to coexist.

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