JP7141707B2 - Method for producing sugar-containing cellulose hydrolyzate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a saccharide-containing cellulose hydrolyzate. More specifically, it relates to a method for producing a glucose-containing cellulose hydrolyzate or a sorbitol-containing cellulose hydrolyzate.
Cross-reference to Related Applications This application claims priority from Japanese Patent Application No. 2017-004847 filed on January 16, 2017, the entire description of which is specifically incorporated herein by reference as disclosure.

A method for producing a sugar-containing liquid by hydrolyzing cellulose or hemicellulose using a solid catalyst is known (Patent Documents 1 and 2). For the decomposition of cellulose and biomass, a ball mill method (Non-Patent Document 1) is used as a pretreatment for amorphization of cellulose. However, this pretreatment requires a large amount of energy, which is an obstacle to practical use. A method using inexpensive phosphoric acid is also known for dissolving cellulose and making it amorphous (Non-Patent Document 2). However, since the cellulose solution has a high viscosity, it is difficult to handle, and in order to extract the cellulose from the phosphoric acid, a large amount of water must be added to precipitate the cellulose. There is a problem that a large amount of energy is required.

Recently, we reported a method for decomposing cellulose with a solid catalyst using a ball mill method (Non-Patent Document 3).

Patent Document 1: WO2011/036955
Patent Document 2: WO2014/007295

Non-Patent Document 1: Energy Fuels., 2006, 20, 807
Non-Patent Document 2: Biomacromolecules, 2006, 7, 644
Non-Patent Document 3: ACS Catal., 2013, 3, 581
The entire disclosures of Patent Documents 1, 2 and Non-Patent Documents 1, 2, 3, respectively, are specifically incorporated herein by reference.

In the method described in Non-Patent Document 3, a solid catalyst composed of a carbon material with a weak acid site has the ability to hydrolyze cellulose, but in order to synthesize glucose in a high yield, the carbon material and cellulose must be combined. It needs to be ball milled and the above problems have not been overcome.

The purpose of this pretreatment is the amorphization of cellulose and the contact formation of carbon materials and cellulose, and the development of a low-energy pretreatment method that achieves the same effect and the hydrolysis of cellulose using this pretreatment method. Therefore, a method for synthesizing glucose with high yield is desired.

An object of the present invention is to provide a new method for hydrolyzing cellulose to synthesize glucose using a solid catalyst.

The present inventors have found that after dissolving cellulose with phosphoric acid, adding a solid catalyst composed of a carbon material to the solution further causes the interaction between cellulose and carbon to produce solubilized cellulose containing partially hydrolyzed cellulose and non-soluble cellulose. It has been found that adsorption of crystalloid cellulose occurs, followed by heating in the presence of a small amount of water, which can accelerate hydrolysis of the cellulose.

In particular, when cellulose is partially hydrolyzed in phosphoric acid, it becomes easier to adsorb to the carbon material, and the viscosity of the solution is dramatically reduced, so that the solubilized cellulose and the carbon material in the solution. It has been found that the amount of water used in the process of adsorbing amorphous cellulose and separating the carbon material after adsorption from the solution can be further reduced.
The present invention was completed based on these findings.

The present invention is as follows.
[1]
a step of dissolving cellulose in an acid aqueous solution (1);
step (2) of mixing a cellulose hydrolysis solid catalyst with an acid aqueous solution in which cellulose is dissolved;
Step (3) of adsorbing at least part of cellulose on a solid catalyst, and heating the solid catalyst with adsorbed cellulose in the presence of water to hydrolyze cellulose to obtain a hydrolyzate containing sugars. step (4),
A method for producing a saccharide-containing cellulose hydrolyzate containing.
[2]
The production according to [1], wherein during and/or after step (1), at least part of the cellulose is at least partially hydrolyzed in an acid aqueous solution, and the product after dissolution is subjected to step (2). Method.
[3]
The production method according to [2], wherein the partial hydrolysis is performed at a temperature of 40 to 80°C.
[4]
The production method according to any one of [1] to [3], wherein at least part of the cellulose used in step (1) has a type I crystal structure.
[5]
The production method according to any one of [1] to [4], wherein the acid in the aqueous acid solution used in step (1) is at least one acid selected from the group consisting of phosphoric acid, sulfuric acid and hydrochloric acid.
[6]
The production method according to [5], wherein the acid aqueous solution used in step (1) is an orthophosphoric acid aqueous solution.
[7]
The production method according to [6], wherein the orthophosphoric acid aqueous solution used in step (1) has a phosphoric acid concentration of 75% or more.
[8]
The production method according to any one of [1] to [7], wherein the adsorption of cellulose onto the solid catalyst in step (3) is performed by adding water to the acid aqueous solution.
[9]
The production according to any one of [1] to [8], wherein the cellulose-adsorbed solid catalyst obtained in step (3) is separated from the acid aqueous solution and subjected to step (4) after removing the acid. Method.
[10]
The cellulose adsorbed on the solid catalyst in step (3) includes at least one selected from the group consisting of partially hydrolyzed cellulose, amorphous cellulose and cellulose II according to any one of [1] to [9]. manufacturing method.
[11]
The production method according to any one of [1] to [10], wherein the cellulose hydrolysis solid catalyst is at least one catalyst selected from the group consisting of carbon catalysts, boron nitride and transition metal-supported catalysts.
[12]
The production method according to [11], wherein the carbon catalyst is a porous carbon material, and the porous carbon material can be activated carbon or carbon black.
[13]
The production method according to [11], wherein the transition metal-supported catalyst is a catalyst in which a transition metal is supported on a solid support, and the solid support is at least one material selected from the group consisting of carbonaceous materials and boron nitride. .
[14]
The production method according to any one of [1] to [13], wherein the mass ratio of cellulose to catalyst in the cellulose-adsorbed solid catalyst is in the range of 100:1 to 10,000.
[15]
The production method according to any one of [1] to [14], wherein the cellulose used in step (1) is plant biomass.

According to the present invention, amorphous cellulose or the like is resistant to solid catalysts made of carbon materials and the like by pretreatment that uses less energy than the conventional phosphoric acid method (Non-Patent Document 2) without using the ball mill method. A contact state can be formed, and glucose can be obtained in high yield when hydrolysis conditions by heating are applied to this sample.

FIG. 1 shows the results of the hydrolysis reaction of cellulose pretreated with phosphoric acid. Figure 2 shows the results of size exclusion chromatography of the solution 0, 3, 7 and 9 days after initiation of stirring for partial hydrolysis of cellulose. FIG. 3 shows the effect of the presence or absence of adsorption of liquefied cellulose on the hydrolysis reaction. FIG. 4 shows the results of the hydrolysis reaction of cellulose when partial hydrolysis of the cellulose solution was carried out at 60°C. FIG. 5 shows the results of hydrolysis reaction of cellulose when the type of activated carbon is changed. FIG. 6 shows the results of hydrolysis reaction of cellulose when the quantitative ratio of activated carbon and cellulose is changed. FIG. 7 shows the results of hydrolysis reaction of cellulose when the solvent used for precipitation (adsorption) of partially hydrolyzed cellulose was changed.

The present invention relates to a method for producing a sugar-containing cellulose hydrolyzate, comprising the following steps (1) to (4).
Step (1): dissolving cellulose in an acid aqueous solution,
Step (2): mixing a cellulose hydrolysis solid catalyst with an acid aqueous solution in which cellulose is dissolved;
Step (3): adsorbing at least a portion of the cellulose on the solid catalyst;
Step (4): The cellulose-adsorbed solid catalyst is heated in the presence of water to hydrolyze the cellulose to obtain a saccharide-containing hydrolyzate.

Step (1)
Step (1) is a step of dissolving cellulose in an acid aqueous solution.
Cellulose used in step (1) can be, for example, plant biomass, and cellulose, which is the main component of plant biomass, exhibits crystallinity when two or more cellulose molecules are bound by hydrogen bonding. It has a type I crystal structure. In step (1), cellulose having such crystallinity can be used as it is as a raw material. However, the cellulose can also be one that has undergone crystallinity reduction and/or partial hydrolysis treatment before dissolution in the acid aqueous solution. However, even if crystalline cellulose is used as it is, it can be dissolved relatively easily, depending on the type and concentration of the acid aqueous solution. This is unnecessary and preferable.

The cellulose with reduced crystallinity may be one in which crystallinity has been partially reduced, or crystallinity has been completely or almost completely eliminated. The type of crystallinity-reducing treatment is not particularly limited, but it may be a crystallinity-reducing treatment capable of breaking the hydrogen bonds and at least partially generating single-stranded cellulose molecules. Dissolution in an acid aqueous solution can be accelerated by using cellulose as a raw material that contains at least partially single-stranded cellulose molecules.

Examples of methods for physically breaking hydrogen bonds between cellulose molecules include pulverization. The pulverizing means is not particularly limited as long as it has a function of pulverizing. For example, the system of the equipment may be either dry or wet, and the grinding system of the equipment may be either batchwise or continuous. Additionally, the comminution force of the device can be anything from impact, compression, shear, friction, and the like.

The acid of the aqueous acid solution used in step (1) is not particularly limited as long as it is an acid capable of dissolving cellulose in an aqueous solution, and may be an inorganic acid, preferably phosphoric acid, sulfuric acid and hydrochloric acid. At least one acid selected from the group. The aqueous phosphoric acid solution can be, for example, an aqueous orthophosphoric acid solution. The acid concentration of the acid aqueous solution used in step (1) is not particularly limited as long as it is a concentration capable of dissolving cellulose, and the concentration capable of dissolving cellulose varies depending on the type of acid. For example, in the case of an orthophosphoric acid aqueous solution, cellulose can be dissolved if the phosphoric acid concentration is 75% or more. From the viewpoint of facilitating the dissolution of cellulose, it is 80% or more, more preferably 85% or more. In the case of sulfuric acid, it is 60% or more, and in the case of hydrochloric acid, it is 30% or more, and cellulose can be dissolved.

Cellulose dissolved in an acid aqueous solution undergoes hydrolysis under the action of acid and water. In step (1), during dissolution of cellulose (in parallel with dissolution of cellulose) and/or after dissolution of cellulose, at least a portion of cellulose is at least partially hydrolyzed in an acid aqueous solution to reduce the molecular weight of the aqueous solution. It is preferred to reduce the viscosity of Even if the cellulose dissolved in the aqueous acid solution is not hydrolyzed, it will be adsorbed by the solid catalyst in steps (2) and (3), but will undergo hydrolysis to become partially hydrolyzed cellulose. , the adsorption on the solid catalyst becomes easier, and the yield of saccharides by thermal hydrolysis in the subsequent step (4) can be improved. Depending on the conditions, the hydrolysis of cellulose by the acid in the acid aqueous solution may produce a small amount of sugar (glucose).

After dissolving the cellulose in the acid aqueous solution, it is preferable to allow at least partial hydrolysis of the cellulose to proceed by maintaining the acid aqueous solution in which the cellulose is dissolved, for example, for 1 minute to 10 days. The cellulose hydrolysis time at this stage can be appropriately determined in consideration of the type and concentration of the acid, the concentration of the cellulose, the treatment temperature, the desired degree of hydrolysis of the cellulose, and the like. The number of days is only an example and is not intended to be limited to this range. The treatment temperature can be, for example, normal temperature (0 to 40° C.), and heating can also promote dissolution and hydrolysis. Although the heating temperature is not particularly limited, it is, for example, in the range of 30°C to 100°C, preferably in the range of 40°C to 80°C. At room temperature, it is preferably kept for 1 day or more, more preferably 3 days or more. On the other hand, holding for too long may result in precipitation of dissolved cellulose and solid by-products, which may reduce the yield of glucose. At room temperature, it is preferable to keep the temperature for 9 days or less. In the range of 40 to 80° C., depending on the temperature, it can be in the range of 1 minute to 240 minutes, and in the case of 60° C., it can be in the range of 10 to 120 minutes. In any case, it can be appropriately determined in consideration of the final yield of glucose by hydrolysis.

The concentration of cellulose in the acid aqueous solution in which cellulose is dissolved takes into account the amount and state of cellulose adsorbed onto the solid catalyst in step (3), the progress of thermal hydrolysis of cellulose in subsequent step (4), and the like. can be determined as appropriate. The concentration of this cellulose can be, for example, in the range of 5-500 g/L, preferably in the range of 10-200 g/L, more preferably in the range of 15-100 g/L. However, these numerical ranges are examples and are not intended to be limiting.

Step (2)
A cellulose hydrolysis solid catalyst is mixed with the acid aqueous solution in which cellulose is dissolved in step (1). A cellulose hydrolysis solid catalyst will be described later. In the present invention, a solid catalyst is mixed with an acid aqueous solution in which cellulose is dissolved. Specifically, a solid catalyst is added to an acid aqueous solution in which cellulose is dissolved, and the mixture is further stirred to mix. Stirring is preferably carried out so that the solid catalyst is substantially uniformly dispersed in the acid aqueous solution. The amount of solid catalyst added to the aqueous acid solution depends on the type of solid catalyst, the concentration of cellulose in the aqueous acid solution, the amount and state of adsorption of cellulose on the solid catalyst in step (3), and the heating and hydration of cellulose in subsequent step (4). It can be determined as appropriate in consideration of the progress of decomposition. The amount of the solid catalyst added to the aqueous acid solution can be, for example, in the range of 2-500 g/L, preferably in the range of 5-200 g/L, and more preferably in the range of 10-100 g/L. However, these numerical ranges are examples and are not intended to be limiting.

Step (3)
At least part of the cellulose is adsorbed onto the solid catalyst mixed with the aqueous acid solution in step (2). Adsorption of cellulose onto the solid catalyst, when the acid is phosphoric acid, is partially adsorbed when the solid catalyst is added in step 2, but can be further accelerated by adding water to the acid aqueous solution. In an aqueous solution of phosphoric acid, the solubility of cellulose decreases as the concentration of phosphoric acid decreases, and as a result, cellulose (including partially hydrolyzed cellulose) in the aqueous solution is adsorbed onto the solid catalyst. A solid catalyst adsorbing cellulose (including partially hydrolyzed cellulose) can be obtained by separating the solid catalyst adsorbing cellulose (including partially hydrolyzed cellulose) from the acid aqueous solution and optionally removing the acid. . Sulfuric acid and hydrochloric acid can also be used in the same manner as phosphoric acid.

The cellulose adsorbed on the solid catalyst in step (3) can contain at least one selected from the group consisting of partially hydrolyzed cellulose, amorphous cellulose and cellulose II. The mass ratio of cellulose to catalyst in the cellulose-adsorbed solid catalyst is not particularly limited, but can range, for example, from 100:1 to 10,000. Considering the conditions of thermal hydrolysis in step (4), it can be, for example, in the range of 100:10 to 1000.

The solid catalyst with adsorbed cellulose can be washed with water, for example, to remove the acid. Although the acid is removed by water washing, a part of the acid may remain, and it is believed that the remaining acid promotes the hydrolysis of cellulose together with the solid catalyst during the thermal hydrolysis in step (4). However, the residual acid may contaminate the sugar-containing hydrolyzate obtained in step (4), and an excessive amount of residual acid is not preferable. The amount of acid remaining on the solid catalyst in step (3) can be appropriately adjusted in consideration of this point.

<Cellulose hydrolysis solid catalyst>
The cellulose hydrolysis solid catalyst is not particularly limited as long as it can catalyze the hydrolysis of plant biomass. It preferably has the activity of hydrolyzing a glycosidic bond, as represented. Furthermore, it is suitable that the cellulose hydrolysis catalyst used in the present invention has adsorption ability for dissolved cellulose including amorphous cellulose in step (3). The catalyst adsorbing the regenerated cellulose containing amorphous cellulose in the step (3) is heated in the presence of water in the step (4) to efficiently hydrolyze the adsorbed cellulose to contain sugars. A hydrolyzate can be obtained. Details will be described later.

Catalysts having activity to hydrolyze glycosidic bonds and adsorbability to dissolved cellulose including amorphous cellulose include, for example, carbon materials, boron nitride (hexagonal h-BN), transition metal-supported catalysts, and the like. Carbon materials and boron nitride have both catalytic activity and adsorptive capacity, whereas in transition metal-supported catalysts, the transition metal mainly contributes to the catalytic activity and the catalyst carrier contributes to the adsorptive capacity. These catalysts can be used alone or in combination of two or more.

Examples of "carbon material" include activated carbon, carbon black, and graphite. These carbon materials may be used alone or in combination of two or more. The shape of the carbon material is preferably porous and/or fine particles in terms of improving reactivity by increasing the contact area with the substrate, and in terms of promoting hydrolysis by developing acid sites. It preferably has functional groups such as phenolic hydroxyl groups, carboxyl groups, lactone (COOR) groups, sulfo groups, and phosphoric acid groups on its surface. Porous carbon materials having functional groups on the surface include woody materials such as coconut shells, bamboo, pine, walnut shells, and bagasse, as well as coke, phenol, etc., which are processed at high temperatures using gases such as water vapor, carbon dioxide, and air. Examples include activated carbon prepared by a physical method that treats carbon dioxide, or a chemical method that uses chemicals such as alkalis and zinc chloride to treat at high temperatures. As specific examples of the “carbon material”, specific examples of the carbon-based support described later can be referred to.

When the carbon material has a phenolic hydroxyl group, a carboxyl group, or a lactone (COOR) group as functional groups on the surface, it can be specified by Boehm titration. The total amount of phenolic hydroxyl groups, carboxyl groups and lactone (COOR) groups on the surface of the carbon material determined by Boehm titration can range, for example, from 0.1 to 10 mmol/g. Furthermore, the amount of carboxyl groups can range from 0.01 to 5 mmol/g, and the sum of phenolic hydroxyl groups and lactone (COOR) groups can range, for example, from 0.01 to 5 mmol/g.

Examples of the carrier used for the "supported transition metal catalyst" include carbon-based carriers and inorganic material carriers. The carbon-based support is a support whose part on which the transition metal is supported is made of carbon, and at least a part of which is suitably made of a porous material. That is, the carbon-based support used in the catalyst of the present invention is suitably made of a porous carbon material at least on the surface of the portion where the transition metal is supported. Alternatively, the surface of a support made of a nonporous carbon material may be coated with a porous carbon material. The carrier support may consist of materials other than carbon and may be either porous or non-porous.

Specific examples of carbon-based solid supports include activated carbon and carbon black. As the activated carbon, for example, activated carbon manufactured by Wako Pure Chemical Industries, Ltd. (for chromatography, crushed 0.2 to 1 mm, crushed 2 to 5 mm, granular, powder, powder acid wash, powder alkaline, powder neutral , rod), activated carbon (granular, powder) manufactured by Kanto Kagaku Co., Ltd., activated carbon manufactured by Tokyo Kasei Co., Ltd. (for oxidation catalyst), activated carbon granule 4-14 mesh manufactured by Sigma-Aldrich Japan Co., Ltd., Norit Japan Co., Ltd. ) PK, PKDA 10x30 MESH (MRK), ELORIT, AZO, DARCO, HYDRODARCO 3000/4000, DARCO LI, PETRODARCO, DARCO MRX, GAC, GAC PLUS, DARCO VAPURE, GCN, C GRAN, ROW/ROY, RO, ROX , RB/W, R, R.EXTRA, SORBONORIT, GF 40/45, CNR, ROZ, RBAA, RBHG, RZN, RGM, SX, SX Ultra, SA, D10, VETERINAIR, PN, ZN, SA-SW, W, GL, SAM, HB PLUS, A/B/C EUR/USP, CA, CN, CG, GB, CAP/CGP SUPER, S-51, S-51A, S-51HF, S-51FF, DARCO GFP, HDB/HDC/HDR/HDW, GRO SAFE, DARCO INSUL, FM-1, DARCO TRS, DARCO FGD/FGL/Hg/Hg-LH, PAC 20/200, Shirasagi (A , C, DO-2, DO-5, DO-11, FAC-10, M, P, PHC, Element DC), Ardenite, Carborafin, Carborafin DC, Honeycomb Carb Shirasagi, Morcebon, Strong Shirasagi, Purified Shirasagi , Special Egret, X-7000/X-7100, X-7000-3/X-7100-3, LPM006, LPM007, Granular Egret (APRC, C2c, C2x, DC, G2c, G2x, GAAx, GH2x, GHxUG, GM2x , GOC, GOHx, GOX, GS1x, GS2x, GS3x, GTx, GTsx, KL, LGK-100, LGK-400, LGK-700, LH2c, MAC, MAC-W, NCC, S2x, SRCX, TAC, WH2c/W2c , WH2x, WH5c/W5c, WHA, X2M (Morcivon 5A, XRC), Spherical Shirasagi (X7000H/X7100H, X7000H-3/X7100H-3, DX7-3), Kuraray Chemical Co., Ltd. GG/GS/ GA, gas-phase activated carbon GW/GL/GLC/KW/GWC, powdered activated carbon PW/PK/PDX, Diahope manufactured by Calgon Carbon Japan (006, 006S, 007, 008, 008B, 008S, 106, 6D, 6MD, 6MW, 6W, S60, C, DX, MM, MZ, PX, S60S, S61, S70, S80, S80A, S80J, S80S, S81, ZGA4, ZGB4, ZGN4, ZGR3, ZGR4, ZS, ZX-4, ZX-7), Diasoap (F, G4-8, W 8-32, W 10-30, XCA-C, XCA-AS, ZGR4-C), Calgon (AG 40, AGR, APA, AP3-60, AP4-60, APC, ASC, BPL, BPL 4x10, CAL, CENTAUR 4x6, CENTAUR 8x30, CENTAUR 12x40, CENTAUR HSV, CPG 8x30, CPG 12x40, F-AG 5, Filtrasorb 300, Filtrasorb 400, GRC 20, GRC 20 12x40 , GRC 22, HGR, HGR-LH, HGR-P, IVP 4x6, OL 20x50, OLC 20x50, PCB, PCB 4x10, RVG, SGL, STL 820, URC, WS 460, WS 465, WS 480, WS490, WSC 470 ), Ajinomoto Fine-Techno Co., Inc. BA, BA-H, CL-H, CL-K, F-17, GS-A, GS-B, HF, HG, HG-S, HN, HP, SD, Y -180C, Y-4, Y-4S, Y-10S, Y-10SF, YF-4, YN-4, YP, ZN, Cataler A series, BC-9, BFG series, CT series, DSW series, FM-150, FW, FY series, GA, PG series, WA series, etc. Examples of carbon black include CRX 1444, CRX 4210, CRX 1346, REGAL 300, STERLING NS, STERLING NS-1, STERLING SO, STERLING VH, STERLING V, SPHERON 5000, and SPHERON manufactured by Cabot Corporation. 6000, Black Pearls 2000, VULCAN 10H, VULCAN 1391, VULCAN 3, VULCAN 3H, VULCAN 6, VULCAN 7H, VULCAN 9, VULCAN J, VULCAN M, VULCAN XC72, VULCAN XC72R, VULCAN XC500, VULCAN XC200, VULCAN XC605, VULCAN XC305 etc.

In addition, mesoporous carbon typified by CMK produced using mesoporous silica as a template, and porous carbon materials obtained by heat-treating coke, phenol, or coconut shell and activating with alkali or water vapor can be used. The specific surface area of these porous carbon materials is preferably 300-2500 m ² /g, more preferably 500-2000 m ² /g.

The shape and form of the solid carrier are not particularly limited, but examples thereof include powder, particles, granules, pellets, honeycombs, rings, cylinders, extruded ribs, and rib rings. The powdery, particulate, granular, or pellet-like carrier can consist of, for example, the above porous carbon material alone. On the other hand, the honeycomb-structured support may be obtained by coating the surface of a support made of a non-porous material, such as cordierite, with the aforementioned porous carbon material. Also, as mentioned above, the support may be made of another porous material.

Examples of transition metals include ruthenium, platinum, rhodium, palladium, iridium, nickel, cobalt, iron, copper, silver, and gold. These transition metals may be used alone or in combination of two or more. From the viewpoint of high catalytic activity, it is preferably selected from platinum group metals such as ruthenium, platinum, rhodium, palladium and iridium. Furthermore, the transition metal selected from ruthenium, platinum, palladium and rhodium is particularly preferred from the viewpoint of high cellulose conversion rate and glucose selectivity. Ruthenium is most preferable from the viewpoint of high catalytic activity.

The amount of the transition metal supported on the solid support is appropriately determined in consideration of the difference in activity depending on the type of transition metal. , more preferably 0.01 to 10% by mass.

A solid catalyst in which a transition metal is supported on a carbon-based carrier used in the present invention can be prepared as follows, for example, by an impregnation method, with reference to a conventional method for producing a metal-supported solid catalyst. The carbon-based support is vacuum dried at 150° C. for 1 hour. Next, water is added and dispersed, and an aqueous solution containing a predetermined amount of metal salt is added thereto and stirred for 15 hours. After that, water is distilled off under reduced pressure, and the obtained solid is reduced at 400° C. for 2 hours under a hydrogen stream, and the resulting solid is used as a catalyst. Specific examples of metal salts include commercially available ruthenium chloride (RuCl ₃ .3H ₂ O), ruthenium nitrosyl nitrate Ru(NO)(NO ₃ ) ₃ , chloroplatinic acid (H ₂ PtCl ₆ .6H ₂ O), diammine dinitro. platinum Pt( _NH3 ) ₂ (NO2) ₂ , palladium chloride ( _PdCl2 ), rhodium chloride ( _RhCl3.3H2O ), iridium chloride _{( IrCl3.3H2O} ), chloroauric _{acid ( HAuCl4.4H 2} O), cobalt nitrate (Co(NO ₃ ) _{2.6H 2 O} ), and the like. However, it is not intended to be limited to these. Since PdCl ₂ is insoluble in water, it can be used as an H ₂ PdCl ₄ aqueous solution by adding 4 equivalents of hydrochloric acid to Pd. Similarly, IrCl ₃ .3H ₂ O can be used by dissolving it in hydrochloric acid.

Step (4)
The hydrolysis in the step (4) is carried out by heating the cellulose-adsorbed solid catalyst in the presence of water, preferably at a temperature at which pressure is applied. A suitable heating temperature for the pressurized state is, for example, a range of 110 to 380.degree. A relatively high temperature is preferred from the viewpoint of rapid hydrolysis of cellulose and suppression of conversion of the product glucose to other sugars. For example, the maximum heating (reaction) temperature is 170 to 320°C. , more preferably 170 to 200°C, more preferably 170 to 190°C. Moreover, the holding time at the temperature is preferably 0 to 120 minutes.

Since the hydrolysis of cellulose is usually carried out in a closed vessel such as an autoclave, even if the pressure is normal at the start of the reaction, the reaction system will be pressurized when heated at the above temperature. Furthermore, the reaction can be carried out by pressurizing the closed container before or during the reaction. The applied pressure is, for example, 0.1 to 30 MPa, preferably 1 to 20 MPa, more preferably 2 to 10 MPa. Alternatively, the reaction can be carried out by heating and pressurizing while circulating the reaction solution with a high-pressure pump, other than in a sealed container.

The amount of water present for hydrolysis is at least an amount that can hydrolyze the entire amount of cellulose. Preferably, the amount can be 2 to 200 times higher.

The hydrolysis atmosphere is not particularly limited. Although it is industrially preferable to conduct the reaction in an air atmosphere, it may be conducted in an atmosphere of a gas other than air, such as oxygen, nitrogen, hydrogen, or a mixture thereof.

The heating for the hydrolysis is terminated when the conversion by hydrolysis of cellulose is between 10% and 100% and the selectivity for glucose is between 20% and 90%. It is preferable in terms of enhancement. When the conversion rate by hydrolysis of cellulose is between 10% and 100% and the selectivity for glucose is between 20% and 90%, the heating temperature, the type and amount of solid catalyst used, and the amount of water (relative to cellulose ratio), the type of cellulose, the stirring method and conditions, etc., so it can be determined experimentally after determining these conditions. The heating time is, under normal conditions, from the start of heating for the hydrolysis reaction, for example, in the range of 5 to 60 minutes, preferably in the range of 5 to 30 minutes, but is not limited to this range. . In addition, the heating for hydrolysis is such that the conversion rate by hydrolysis of cellulose is preferably in the range of 30 to 100%, more preferably in the range of 40 to 100%, still more preferably in the range of 50 to 100%, and most preferably in the range of 30 to 100%. is in the range 55-100% and the selectivity for glucose is preferably in the range 25-90%, more preferably in the range 30-90%, most preferably in the range 40-90% is appropriate.

The type of hydrolysis reaction may be batch type or continuous type. The reaction is preferably carried out while stirring the reaction mixture.

In the present invention, a sugar-containing liquid containing glucose as a main component and containing less overlysates such as 5-hydroxymethylfurfural can be produced by a hydrolysis reaction at a relatively high temperature for a relatively short period of time.

After heating, it is preferable to cool the reaction solution from the viewpoint of suppressing the conversion of glucose to other sugars and increasing the yield of glucose. From the viewpoint of increasing the glucose yield, the cooling of the reaction solution is preferably carried out under conditions that maintain the glucose selectivity in the range of 20 to 90%, more preferably 25 to 90%, and 30 to 90%. is more preferred, and the range of 40-90% is most preferred.

From the viewpoint of increasing the yield of glucose, the reaction solution is preferably cooled as quickly as possible to a temperature at which conversion of glucose to other sugars does not occur. at a rate preferably in the range of 10-150° C./min. A temperature at which conversion of glucose to other sugars does not occur is, for example, 150° C. or lower, preferably 110° C. or lower. That is, the reaction solution is cooled to a temperature of 150° C. or less at a rate of 1 to 200° C./min, preferably 10 to 150° C./min. It is more suitable to carry out in the range of -200°C/min, preferably in the range of 10-150°C/min.

In the production method of the present invention, the cellulose hydrolysis solid catalyst can be a carbon catalyst, boron nitride or transition metal-supported solid catalyst, and the sugar-containing cellulose hydrolyzate can be a glucose-containing cellulose hydrolyzate. In the present invention, the reaction mechanism of hydrolysis of cellulose using, for example, activated carbon as a solid catalyst is not intended to be limited to this mechanism, but is considered as follows.

Carbon materials such as activated carbon are considered to adsorb hydrophobic groups (-CH) of cellulose to aromatic rings present on the surface thereof due to CH-π interaction, as shown below.

Furthermore, it is presumed that an acid site such as a carboxyl group becomes an active site and promotes hydrolysis.

Therefore, it is preferable that the solid catalyst is a carbon material such as activated carbon having an aromatic ring, and has acid sites such as carboxyl groups on its surface as described above.

If the method of the present invention can efficiently and preferentially produce glucose from cellulose, it can also be converted into fuels and chemicals.

Hereinafter, the present invention will be described in more detail based on examples. However, the examples are illustrative of the present invention, and the present invention is not intended to be limited to the examples.

Example 1
After moistening unground microcrystalline cellulose (324 mg, Avicel PH101) with distilled water (0.9 mL), add 85% phosphoric acid (16.2 mL, Wako Pure Chemical Industries) and stir to dissolve the cellulose. rice field. Cellulose was completely dissolved in about 10 minutes. The solution was stirred at room temperature (approximately 22° C.) for several days (0-9 days) to partially hydrolyze the cellulose. As a solid catalyst, activated carbon (BA-Air, BA (Ajinomoto Fine-Techno Co., Ltd., specific surface area: 1230 m ² /g)) was air-oxidized in an electric furnace at 425°C for 10 hours (Carboxyl groups, etc., which act as weak acid sites on the surface). 324 mg of Oxygen-containing functional group introduced)) was added and stirred for 10 minutes. 30 mL of distilled water was added, and the partially hydrolyzed cellulose was adsorbed in a state in which the partially hydrolyzed cellulose was in good contact with the carbon (a state in which the cellulose was adsorbed on the carbon). This was filtered using a membrane filter (pore size: 0.1 μm) and washed with water (300 ml) to remove phosphoric acid in the solid. 40 mL of water was added to this sample, and the mixture was reacted in an autoclave at 180° C. for 20 minutes to hydrolyze cellulose. Incidentally, the pH was 2.0 to 2.2 when 40 mL of water was added to the above sample. From this, it is possible that phosphoric acid remained in the sample and that the remaining phosphoric acid also acted as a catalyst for hydrolysis. After reaction, the solution was analyzed by HPLC.

Comparative example 1
In order to confirm the effect of the phosphoric acid treatment in Example 1, a hydrolysis reaction was performed under the same conditions as in Example 1 using cellulose not subjected to phosphoric acid treatment.

The results of the hydrolysis reaction of Example 1 and Comparative Example 1 are shown in FIG. Hydrolysis of non-phosphatized cellulose yields only 3% glucose, whereas with phosphate-pretreated cellulose, glucose yield increases with the number of days of phosphatization. , up to 70%. This result shows the effectiveness of the phosphoric acid treatment. Results of size exclusion chromatography of the solution 0 days, 3 days, 7 days and 9 days after the start of stirring for partial hydrolysis of cellulose (0 days after the start of stirring means 0 days of partial hydrolysis, cellulose was dissolved in phosphoric acid and water was immediately added to precipitate cellulose), along with the results of size exclusion chromatography of the aqueous dispersion of microcrystalline cellulose (Avicel PH101), which is the raw material, are shown in Fig. 2 shown in It can be seen that the molecular weight of cellulose decreased to about 1/2 due to partial hydrolysis 7 days and 9 days after the start of stirring.

Example 2
Experiments were also conducted to clarify the effectiveness of the adsorption of liquid cellulose on the carbon catalyst. The results were obtained when cellulose was adsorbed on the carbon surface in the same manner as in Example 1, with the cellulose being treated with phosphoric acid for 6 days.

Comparative example 2
After dissolving cellulose in phosphoric acid in the same manner as in Example 1, stirring was continued at room temperature for 6 days. Distilled water (30 mL) was added thereto to precipitate cellulose, followed by filtration and washing with water to remove phosphoric acid. Activated carbon similar to that used in Example 1 was added to this cellulose, and a hydrolysis reaction was carried out under the same conditions as in Example 1. (This is a method without the step of liquid cellulose being adsorbed on activated carbon.)

FIG. 3 shows the results of hydrolysis with and without liquid cellulose adsorbed on the activated carbon surface (Example 2) (Comparative Example 2).

From the results shown in FIG. 3, it was clarified that adsorption of liquid cellulose (solubilized cellulose including partially hydrolyzed cellulose and amorphous cellulose) to the carbon catalyst increases the hydrolysis reactivity.

From the above results, it can be said that it is effective to dissolve the cellulose with phosphoric acid and perform the hydrolysis reaction in a state where the liquid cellulose is adsorbed on the carbon catalyst.

Example 3
Cellulose was hydrolyzed in the same manner as in Example 1, except that the cellulose solution was changed to room temperature and stirred at 60°C for 60 minutes to partially hydrolyze cellulose. The results are shown in FIG. 4 (results for 60 minutes in the figure). By performing the partial hydrolysis of cellulose at 60°C, the cellulose hydrolysis result is almost the same as when it is performed at room temperature (about 25°C) (DAY 7 (7 days) in Fig. 1) in a shorter time (60 minutes). Got.

Example 4
Cellulose was hydrolyzed in the same manner as in Example 3, except that the cellulose solution was stirred at 60° C. for 0, 30, or 90 minutes. The results are shown in FIG. By carrying out partial hydrolysis of cellulose at 60°C, almost the same cellulose hydrolysis results as those carried out at room temperature (approximately 25°C) (for 7 days) were obtained even for 30 and 90 minutes.

Example 5
BA ((Ajinomoto Fine-Techno Co., Inc., specific surface area: 1230 m ² /g)), Norit (Cabot Corporation, specific surface area: 1210 m ² /g)), Air oxi Cellulose was hydrolyzed in the same manner as in Example 3, except that Norita was replaced with Norit (carbon air-oxidized in an electric furnace at 425°C for 10 hours). The results are shown in FIG. As a reference example (blank) in FIG. 5, cellulose was made into a phosphoric acid solution, 25 mL of water was added without adding a solid catalyst to precipitate the cellulose, the cellulose was washed with 300 mL of water, and 40 mL of water was added. The results of hydrolyzing cellulose by reacting in an autoclave at 180°C for 20 minutes are also shown. Table 1 shows the results of Boehm titration of each activated carbon. Boehm titration was performed by a conventional method.

COOR indicates a lactone, and assumes, for example, the structure of the lower left portion of the following chemical formula.

Example 5
Cellulose was hydrolyzed in the same manner as in Example 3, except that the amount of activated carbon BA-Air as a solid catalyst was changed from 324 mg to 218 mg and 109 mg. The results are shown in FIG.

Example 6
Activated charcoal (BA-Air) was added to the partially hydrolyzed cellulose, and after stirring for 10 minutes, instead of adding 25 mL of distilled water, ethanol, acetone, or 1-propanol (both 25 mL) was used to partially hydrolyze the cellulose. Cellulose was hydrolyzed in the same manner as in Example 3, except that precipitation on activated carbon and adsorption were performed. The results are shown in FIG. The yield of glucose was high when water was used for precipitation and adsorption of partially hydrolyzed cellulose.

INDUSTRIAL APPLICABILITY The present invention is useful in the field of production of sugars such as glucose by hydrolysis of cellulose.

Claims (14)

a step of dissolving cellulose in an acid aqueous solution (1 A );
a step (1B) of holding an acid aqueous solution in which cellulose is dissolved and at least partially hydrolyzing the cellulose;
dissolving the cellulose and mixing the at least partially hydrolyzed acid aqueous solution with a cellulose hydrolysis solid catalyst (2);
Step (3) of adsorbing at least part of cellulose onto the solid catalyst, and heating the solid catalyst with adsorbed cellulose in the presence of water to hydrolyze the cellulose to obtain a hydrolyzate containing glucose . step (4),
A method for producing glucose, comprising: The production method according to claim 1 , wherein the partial hydrolysis in step (1B) is performed at a temperature of 40 to 80°C. 3. The production method according to any one of claims 1 to 2 , wherein at least part of the cellulose used in step ( 1A ) has a type I crystal structure. The production method according to any one of claims 1 to 3 , wherein the acid in the aqueous acid solution used in step ( 1A ) is at least one acid selected from the group consisting of phosphoric acid, sulfuric acid and hydrochloric acid. The production method according to claim 4 , wherein the acid aqueous solution used in step ( 1A ) is an orthophosphoric acid aqueous solution. The production method according to claim 5 , wherein the orthophosphoric acid aqueous solution used in step ( 1A ) has a phosphoric acid concentration of 75% or more. The production method according to any one of claims 1 to 6 , wherein the adsorption of cellulose onto the solid catalyst in step (3) is performed by adding water or a water-soluble organic solvent to the acid aqueous solution. The production method according to any one of claims 1 to 7 , wherein the cellulose-adsorbed solid catalyst obtained in step (3) is separated from the acid aqueous solution and subjected to step (4) after the acid is removed. The production according to any one of claims 1 to 8 , wherein the cellulose adsorbed on the solid catalyst in step (3) contains at least one selected from the group consisting of partially hydrolyzed cellulose, amorphous cellulose and cellulose II. Method. The production method according to any one of claims 1 to 9 , wherein the cellulose hydrolysis solid catalyst is at least one catalyst selected from the group consisting of carbon catalysts, boron nitride and transition metal-supported catalysts. 11. The manufacturing method according to claim 10 , wherein the carbon catalyst is a porous carbon material, and the porous carbon material can be activated carbon or carbon black. The production method according to claim 10 , wherein the transition metal-supported catalyst is a catalyst in which a transition metal is supported on a solid support, and the solid support is at least one material selected from the group consisting of carbonaceous materials and boron nitride. . The production method according to any one of claims 1 to 12 , wherein the mass ratio of cellulose to catalyst in the cellulose-adsorbed solid catalyst is in the range of 100:1 to 10,000. The production method according to any one of claims 1 to 13 , wherein the cellulose used in step (1) is plant biomass.

Images