JP3581868B2 - Cellulose solubilization method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for efficiently hydrolyzing cellulose or a cellulose-containing substance in a natural polymer compound to convert it into a water-soluble component containing a water-soluble oligosaccharide and hexose useful as a functional food material. .
[0002]
[Prior art]
Industrial and domestic waste contains a large amount of natural polymer compounds such as cellulose components, but most of them are actually discarded without being reused. However, these compounds can be valuable chemical raw materials and energy resources, and it is desired to develop a technology for treating them in large quantities and effectively utilizing them.
[0003]
By the way, cellulose, which is a typical natural polymer compound, is a compound in which glucose is polymerized in a higher dimension. Oligosaccharides are those in which a plurality of monosaccharides are linked, and are also called oligosaccharides with respect to polysaccharides. The number of constituent monosaccharides usually refers to those having 2 to 6, but recently those having 10 or more are also called oligosaccharides. Sometimes.
[0004]
Oligosaccharides, which have various physiological activities such as sweetness, moisturizing properties, and growth of bifidobacteria, are attracting attention as functional food materials. And soybean oligosaccharides are practically used. And these oligosaccharides, except for the soybean oligosaccharides, are produced mainly by allowing enzymes to act on raw materials.
[0005]
On the other hand, as a method for producing a monosaccharide that can be alcohol-fermented from cellulose, for example, an acid hydrolysis method, an enzymatic decomposition method, a decomposition method using rot fungi, and the like are known. However, in the acid hydrolysis method, there are problems of corrosion of the reactor and waste liquid treatment, and in the decomposition method using enzymes and rot bacteria, there is a disadvantage that the saccharification rate is extremely slow due to the strong crystal structure of cellulose. . Therefore, in the latter method, explosion treatment or grinding treatment is considered as a pretreatment to loosen the crystal structure of cellulose, but in this case, sugar is lost due to over-decomposition or energy is consumed in large amounts. There is a drawback that must be done. Recently, in order to solve the above problems, a method has been proposed in which cellulose is hydrolyzed using water in a supercritical state or subcritical state to produce glucose as a monosaccharide (JP-A-5-31000). JP-A-10-327900), there is a problem in efficiency, and it has not yet been put to practical use.
[0006]
[Problems to be solved by the invention]
Under such circumstances, the present invention uses a cellulosic resource as a raw material, does not corrode the reactor, and is hydrolyzed under a relatively mild condition in a short time to obtain a functional food material or the like. It is intended to provide a method for converting into water-soluble components, including useful water-soluble oligosaccharides and alcohol-fermentable monosaccharides.
[0007]
[Means for Solving the Problems]
The present inventors have conducted intensive studies in order to develop a method for solubilizing cellulose or a cellulose-containing substance with high conversion efficiency and rapidly, and as a result, they are hydrolyzed by contact with pressurized hot water. At that time, it was found that the object can be achieved by the presence of a lanthanoid ion as a catalyst, and the present invention has been accomplished based on this finding.
[0008]
That is, the present invention is characterized in that cellulose or cellulose-containing substance powder is hydrolyzed by contact with pressurized hot water heated to 220 to 270 ° C. in the presence of a lanthanoid ion supplying substance. It provides a method.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Materials that can be solubilized by the method of the present invention are cellulose and cellulose-containing substances. The cellulose may be derived from plants, or may be derived from animals or bacteria. There is no particular limitation on the number of constituent glucose units, and any of the generally known ranges of 2000 to 26000 can be used.
Furthermore, a part of the constituent glucose units may be etherified or esterified.
[0010]
Next, examples of the cellulose-containing substance include wood and agricultural waste containing cellulose.
In the method of the present invention, these raw materials are used as powders in order to improve the hydrolysis rate. The particle size of this powder is desirably as small as possible, but is selected in the range of 10 to 200 μm, preferably 20 to 100 μm in consideration of the formation of secondary aggregates and ease of handling.
[0012]
The method of the present invention needs to be performed in the presence of a substance capable of supplying a lanthanoid ion as a catalyst. Due to the presence of the lanthanoid ion, the hydrolysis rate of cellulose is remarkably increased, and the cellulose or the cellulose-containing substance can be solubilized in a short time.
[0013]
As the lanthanoid ion supplying material, a lanthanoid metal, for example, a halide or chloride such as lanthanum, cerium, praseodymium, neodymium, samarium, holmium, thulium, ytterbium, or lutetium is used. The halide is preferably a fluoride or chloride, and the water-soluble salt is preferably a trifluoromethanesulfonate, that is, triflate.
[0014]
The lanthanoid ion supplying substance is used in an amount of 5 to 50 mmol based on the raw material cellulose. In many cases, when the amount is 10 mmol or more, the solubilization reaches a saturated state and the amount becomes larger. Since the generation of gas and volatile components rapidly increases, this amount is preferably about 10 mmol.
[0015]
In the present invention, the powder of the cellulose or the cellulose-containing substance is brought into contact with pressurized hot water containing a catalyst, and is hydrolyzed to be solubilized. At this time, the reaction system is not particularly limited, but for example, a fixed-bed reactor is filled with powder of cellulose or a cellulose-containing substance, and pressurized hot water containing a predetermined amount of a catalyst is continuously passed therethrough. In this manner, a form in which cellulose is hydrolyzed and a generated solubilized substance flows out of the system together with hot water or a form in which a slurry comprising cellulose or a cellulose-containing substance, a catalyst and water is continuously passed through a reactor is preferable. is there.
[0016]
At this time, it is necessary to use hot water heated to a temperature of 220 to 270 ° C. as the pressurized hot water. If this temperature is lower than 220 ° C., the hydrolysis rate is too slow to be practical, and if it is higher than 270 ° C., the production of gas and volatile components increases, and the production of soluble components does not increase so much. It is economically disadvantageous in terms of the reactor and energy consumption. The temperature of the pressurized hot water is preferably in the range of 240 to 260 ° C. in consideration of the hydrolysis rate, the production amount of the soluble component and the economic efficiency.
[0017]
Further, the contact time of the powder of cellulose or cellulose-containing substance and pressurized hot water varies depending on the molecular weight and crystallinity of cellulose present therein or the type of catalyst used, but generally the temperature of pressurized hot water is high. May be as short as possible. Usually, it is about 50 to 180 seconds if the hot water under pressure is in the range of 250 to 270 ° C, longer than 180 seconds if the temperature is lower than this, and longer than 50 seconds if the temperature is higher than this. Although shorter, it is generally in the range of 30 to 200 seconds. However, in the case of using a fixed bed type reactor through which hot water flows, it is necessary to pass water for several minutes in order to drive out soluble components out of the reaction system.
[0018]
It is desirable that the hot water flowing out of the reactor be cooled immediately in order to suppress the secondary decomposition of the soluble components contained therein. The pressure in the reactor is maintained at or above the saturated vapor pressure of the reaction temperature so that the hot water maintains a liquid state in the reactor.
The components solubilized by the method of the present invention contain water-soluble oligosaccharides and small amounts of monosaccharides and furfural.
[0019]
【Example】
Next, the present invention will be described in more detail with reference to examples.
[0020]
Example 1
0.5 g of dried microcrystalline cellulose (particle diameter: 100 to 120 μm), 3.0 g of distilled water, and 11.1 mg (30 μmol) of LaCl ₃ are charged into a stainless steel autoclave (internal volume: 6 ml), and heated to 250 ° C. under a nitrogen atmosphere. Solubilization was performed by shaking in a heated salt bath. The reaction time was changed within a range of 30 seconds to 300 seconds, and immediately after the predetermined reaction time had elapsed, the reactor was immediately cooled in a water bath (15 ° C.) to terminate the reaction. The internal temperature was monitored using a temperature measuring device DP-2MC (manufactured by Rika Kogyo Co., Ltd.). After the reaction, the gas in the reactor was exhausted, the contents were taken out into a beaker, filtered through a glass filter, and the filtrate was evaporated to obtain a water-soluble component (WS), yield (% by mass). I asked. Next, the water-insoluble component remaining on the glass filter is washed with 200 ml of methyl alcohol, and the methyl alcohol-soluble component (MS) and the methyl alcohol-insoluble component (MI) are recovered, and the respective yields (% by mass) are obtained. The yield (% by mass) of the gas and the volatile component (G) was calculated from the mass loss.
This result is shown in FIG. 1 as a graph.
[0021]
Comparative Example The experiment of Example 1 was repeated without using 11.1 mg of LaCl ₃ used in Example 1. This result is shown in FIG. 2 as a graph.
As can be seen by comparing FIG. 1 and FIG. 2, in the system to which the catalyst was added (FIG. 1), the methyl alcohol insoluble component (MI) decreased with the reaction time, and the minimum value of 20 mass was obtained in the reaction time of 180 to 240 seconds. %showed that. In addition, the water-soluble component (WS) increased accordingly, and reached 56% by mass in 180 seconds. Then, after 180 seconds, when the water-soluble component (WS) started to decrease, the methyl alcohol-soluble component (MS) and the gas and volatile components (G) increased. In the system without addition of the catalyst (FIG. 2), only 13.3% by mass of cellulose was decomposed even when the reaction time was 300 seconds, which indicates that the addition of lanthanoid ions accelerates the decomposition of cellulose. You.
The water-soluble component (WS) produced here is produced by hydrolysis of water-soluble polysaccharides such as glucose and cellobiose, and 5-hydroxymethylfurfural and 5-hydroxymethylfurfural generated by conversion of glucose. It is levulinic acid. At a reaction time of 150 seconds when the water-soluble component (WS) was the largest, the amount of each decomposed product was 5.8% by mass of glucose, 0.2% by mass of cellobiose, and 5-hydroxymethylfurfural 19 with respect to the charged amount of cellulose. 0.2% by mass and 2.3% by mass levulinic acid.
[0022]
Example 2
The experiment of Example 1 was repeated using a raw material mixture in which the concentration of LaCl ₃ was changed in the range of 1 to 50 mmol, and the temperature of the salt bath was 250 ° C., and the reaction time was 90 seconds. A graph showing the relationship between the water-soluble component (WS), the methyl alcohol-soluble component (MS), the methyl alcohol-insoluble component (MI), the yield of the gas and the volatile component (G) (mass%) obtained at this time. 3 is shown.
As can be seen from this figure, the methyl alcohol-insoluble component (MI) rapidly decreases with an increase in the catalyst concentration, and the water-soluble component (WS) is generated more as the catalyst concentration increases, but becomes saturated at 10 mM or more. Reached. On the other hand, the methyl alcohol-soluble component (MS) is hardly generated, but the gas and the volatile component (G) increase as the catalyst concentration increases. This indicates that the amount of the catalyst is preferably about 10 mM.
[0023]
Example 3
The experiment of Example 1 was repeated at a salt bath temperature in the range of 200 to 375 ° C., a catalyst concentration of 10.0 mmol, and a reaction time of 90 seconds. FIG. 4 is a graph showing the relationship between the salt bath temperature and the yield (% by mass) of each component at this time.
As can be seen from this figure, the methyl alcohol insoluble component (MI) sharply decreases at 225 to 275 ° C., and the decomposition of cellulose proceeds in this temperature range. Further, the methyl alcohol insoluble component (MI) takes a minimum value at 275 ° C. and thereafter increases. On the other hand, due to the decomposition of cellulose, the water-soluble component (WS) increases, reaches a maximum at 250 ° C., and thereafter decreases. As the water-soluble component (WS) decreases, the methyl alcohol-soluble component (MS) and the gas and volatile components (G) increase. At 300 ° C. or higher, no significant change is observed in the decomposition product generation behavior.
[0024]
【The invention's effect】
According to the present invention, cellulose or a cellulose-containing substance can be efficiently water-solubilized at a relatively low temperature and in a short time without corrosion of a reactor as in the case of acid hydrolysis.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the reaction time and the yield of each component in the method of the present invention.
FIG. 2 is a graph showing the relationship between the reaction time and the yield of each component when no catalyst is used.
FIG. 3 is a graph showing the relationship between the catalyst concentration and the yield of each component in the method of the present invention.
FIG. 4 is a graph showing the relationship between the reaction temperature and the yield of each component in the method of the present invention.

Claims (3)

A method for solubilizing cellulose, comprising: bringing a powder of cellulose or a cellulose-containing substance into contact with hot pressurized water heated to 220 to 270 ° C in the presence of a lanthanoid ion supplying substance to hydrolyze the cellulose. The method for solubilizing cellulose according to claim 1, wherein the lanthanoid ion supplying substance is a halide of a lanthanoid metal or trifluoromethanesulfonic acid. 3. The method for solubilizing cellulose according to claim 1, wherein the cellulose is contacted with hot pressurized water for 30 to 200 seconds.

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