Process for the production of glucose and catalyst therefor

Abstract

This invention provides a method for manufacturing glucose, the method comprising a step of contacting a liquid containing cellulose and water with a solid acid catalyst, wherein the solid acid catalyst comprises carbon, titanium, and silicon dioxide, and has sulfonyl groups as surface functional groups; and this invention also provides a solid acid catalyst for manufacturing glucose, the solid acid catalyst for manufacturing glucose comprising carbon, titanium, and silicon dioxide, and having sulfonyl groups as surface functional groups.

Description

Technical Field

[0001] This invention relates to a method for producing glucose and a solid acid catalyst for glucose production. Background Technology

[0002] To achieve carbon neutrality, bioethanol, as a raw material for materials with a low carbon footprint, has been extensively studied. In particular, the production of bioethanol from edible biomass, based on its dehydration reaction, olefination, and polymerization, has been investigated. Technologies for converting edible biomass into bioethanol have been established, and these methods are considered promising for use as raw materials in plastics products. However, edible biomass faces competition from food applications, and in recent years, the conversion of edible biomass to inedible biomass as a raw material for bioethanol production has been progressing.

[0003] Cellulose, an inedible biomass, can be broken down into glucose through enzymatic or sulfuric acid-based hydrolysis, and then ethanol can be obtained from glucose via microbial fermentation. However, the decomposition reaction into glucose is generally difficult due to the chemically stable structure of cellulose, resulting in reduced cellulose conversion and glucose yield.

[0004] In recent years, solid acid catalysts have attracted attention and been studied as hydrolysis catalysts in methods for producing glucose by hydrolyzing cellulose. For example, as a method for producing glucose from cellulose using a solid acid catalyst, Patent Document 1 describes "a method for producing a sugar-containing liquid with glucose as the main component, the method comprising the following steps: in at least one containing 800m 2 / g or more and 2500m 2 Cellulose or hemicellulose is hydrolyzed in the presence of a catalyst and water using a porous carbon material with a specific surface area of ​​less than / g and a phenolic hydroxyl content of 100 mmol / kg or more and 700 mmol / kg or less, thereby producing at least oligosaccharides and glucose. Furthermore, Non-Patent Literature 1 describes a method for producing sugars such as glucose by hydrolyzing cellulose using a sulfonated silica / carbon nanocomposite. Non-Patent Literature 1 suggests that this sulfonated silica / carbon nanocomposite exhibits high conversion efficiency to glucose in the hydrolysis reaction of cellulose.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2011 / 036955

[0008] Non-patent literature

[0009] Non-patent literature 1: Green Chem., 2010, 12, 1560-1563 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Even in the method described in Patent Document 1 and the method described in Non-Patent Document 1, which is considered to have high conversion efficiency to glucose, the glucose yield is insufficient. Furthermore, for the method described above for producing glucose from cellulose to achieve carbon neutrality, it is important to conduct research and development with industrialization in mind, and further improvements in glucose yield are required when considering industrial feasibility.

[0012] The objective of this invention is to provide a method for producing glucose from cellulose in high yield by utilizing the hydrolysis reaction of cellulose with a solid acid catalyst, and a solid acid catalyst for producing glucose from cellulose in high yield.

[0013] means for solving problems

[0014] That is, the objective of this invention is achieved through the following means.

[0015] <1> A method for manufacturing glucose, the method comprising a step of contacting a liquid containing cellulose and water with a solid acid catalyst, wherein the solid acid catalyst comprises carbon, titanium and silicon dioxide, and has sulfonyl groups as surface functional groups.

[0016] <2> according to <1> The manufacturing method wherein the silicon dioxide has mesopores.

[0017] <3> according to <1> or <2> In the manufacturing method described above, the carbon element is loaded onto the surface of the silicon dioxide.

[0018] <4> according to <1> ~ <3> The manufacturing method according to any one of the following, wherein the titanium element is contained in the silicon dioxide.

[0019] <5> A solid acid catalyst for glucose production, wherein the solid acid catalyst for glucose production comprises carbon, titanium and silicon dioxide, and has sulfonyl groups as surface functional groups.

[0020] <6> according to <5> The solid acid catalyst for glucose production, wherein the silica has mesopores.

[0021] <7> according to <5> or <6> In the manufacturing method described above, the carbon element is loaded onto the surface of the silicon dioxide.

[0022] <8> according to <5> ~ <7> The manufacturing method according to any one of the following, wherein the titanium element is contained in the silicon dioxide.

[0023] Invention Effects

[0024] The present invention provides a method for producing glucose from cellulose in high yield and a solid acid catalyst.

[0025] The above and other features and advantages of the present invention will become clearer from the following description. Attached Figure Description

[0026] Figure 1 This is an example of a chromatogram obtained by HPLC analysis of a cellulose decomposition solution. Detailed Implementation

[0027] In this invention and this specification, the numerical range indicated by “~” refers to the range that includes the values ​​recorded before and after “~” as the lower limit and upper limit.

[0028] Methods for producing glucose

[0029] The glucose manufacturing method of the present invention (hereinafter, sometimes referred to as "the manufacturing method of the present invention") is a glucose manufacturing method comprising the step of contacting a liquid containing cellulose and water with a solid acid catalyst. In the manufacturing method of the present invention, a solid acid catalyst containing carbon, titanium, and silicon dioxide, and having sulfonyl groups as surface functional groups (hereinafter, sometimes referred to as "the solid acid catalyst of the present invention") is used as the solid acid catalyst. By contacting the solid acid catalyst of the present invention with cellulose in a simple and safe step, glucose can be manufactured in high yield. This is believed to be because the hydrolysis reaction of cellulose is promoted by contacting it with the solid acid catalyst of the present invention, thus increasing the efficiency of the cellulose hydrolysis reaction. Therefore, the manufacturing method of the present invention and the solid acid catalyst of the present invention can effectively utilize cellulose, an inedible biomass that can avoid competition with food applications, while simultaneously manufacturing glucose in high yield, which is an important raw material for the production of bioethanol, an important material for achieving carbon neutrality, and also bringing industrialization into view. As a result, the manufacturing method of the present invention and the solid acid catalyst of the present invention are suitable for application in methods for producing bioethanol using inedible biomass.

[0030] First, the components used in the manufacturing method of the present invention will be described.

[0031] [A liquid containing cellulose and water]

[0032] The manufacturing method of this invention uses a liquid (sometimes referred to as a "reaction solution") containing cellulose and water. This reaction solution only needs to contain cellulose and water, but may also contain other components. These other components can be anything that does not hinder the hydrolysis reaction of cellulose, and examples include: hemicellulose, lignocellulose, fatty acids, high-molecular-weight surfactants, aluminum sulfate, etc.

[0033] The cellulose content in the reaction solution is not particularly limited, but considering the cellulose hydrolysis efficiency (hereinafter sometimes simply referred to as "hydrolysis efficiency") and glucose yield (hereinafter sometimes referred to as "glucose yield"), it is preferably 0.01 kg to 1 kg relative to 1 L of water, more preferably 0.05 kg to 0.5 kg. In this invention, when using a mixture such as waste paper pulp as the cellulose source, the cellulose content in the reaction solution refers to the actual cellulose content (cellulose equivalent).

[0034] The reaction solution is typically obtained as a suspension or dispersion by mixing cellulose with water.

[0035] Cellulose

[0036] The cellulose used in the manufacturing method of this invention only needs to be of the molecular formula (C6H12H2O). 10 O5) n The carbohydrates (polysaccharides) shown may be used, including hemicellulose and lignocellulose in addition to cellulose. The cellulose used in the manufacturing method of this invention may be a mixture of cellulose, hemicellulose, and / or lignocellulose. However, when using lignocellulose or when lignocellulose is included, it is preferable to perform the lignin removal step described later.

[0037] The cellulose can be synthetic or commercially available, derived from inedible biomass, or its waste or recyclables. Examples of cellulose derived from inedible biomass include: cellulose from plants such as trees, thinnings, or timber (lignocellulose), and cellulose obtained by appropriately alkali-treating chemical pulp obtained by bleaching plant-based defatting powders. Considering the substitutability of edible biomass such as bioethanol, the cellulose used in the manufacturing method of this invention is preferably derived from inedible biomass. Plants are representative examples of inedible biomass, but from the perspective of efficient resource utilization and cost reduction, their waste or recyclables are preferred. Examples of inedible biomass include: wood flour or sawdust from trees, thinnings, or timber, various types of pulp (unused products), and board pulp or pulp sludge discharged during the papermaking or pulp manufacturing process, as well as waste pulp such as pulp recovered from waste diapers. The recycling volume of waste pulp, such as pulp sludge and pulp recovered from waste diapers, is abundant, which can effectively utilize resources (and reduce costs). Moreover, even without implementing the lignin removal process described later, poisoning of solid acid catalysts caused by lignin can be avoided, which is particularly advantageous.

[0038] Cellulose typically exhibits crystallinity through hydrogen bonding between two or more cellulose molecules. The manufacturing method of the present invention can use crystalline cellulose (sometimes referred to as "crystalline cellulose"), or cellulose whose crystallinity has been reduced by conventional methods (sometimes referred to as "low-crystallinity cellulose" or "microcrystalline cellulose"). Low-crystallinity cellulose can be obtained by partially reducing the crystallinity of crystalline cellulose, or by completely eliminating crystallinity. There are no particular limitations on the method for reducing crystallinity, but a method that can cleave the aforementioned hydrogen bonds to at least partially generate single-chain cellulose molecules is preferred. The hydrolysis efficiency of cellulose containing at least partially single-chain cellulose molecules is significantly improved. Specifically, various methods described in Patent Document 1 can be cited as methods for reducing crystallinity, among which physical methods such as air jet milling, hammer milling, ball milling, and bead milling are preferred.

[0039] The shape of the cellulose used in the manufacturing method of the present invention is not particularly limited, but from the perspective of hydrolysis reaction efficiency and glucose yield, it is preferred to be in particulate, powder, or flake form. The size of the cellulose is not particularly limited and can be appropriately determined considering hydrolysis reaction efficiency and glucose yield.

[0040] <Water>

[0041] The water used in the manufacturing method of the present invention is not particularly limited, and industrial water, well water, municipal water, ion-exchange water, purified water, (ultra)pure water, etc. can be used, with ion-exchange water, purified water, (ultra)pure water being preferred.

[0042] [Solid acid catalyst]

[0043] The solid acid catalyst used in the manufacturing method of the present invention is a solid acid catalyst containing carbon, titanium, and silicon dioxide, and having sulfonyl groups as surface functional groups. By contacting this solid acid catalyst with cellulose in water, glucose can be produced in high yield. This solid acid catalyst, when used for the aforementioned application of producing glucose from cellulose, is specifically referred to as a solid acid catalyst for glucose production. This solid acid catalyst contains carbon, titanium, and sulfonyl groups (-SO3H) in a matrix (also called a "silica matrix") with silicon dioxide (silica) as the main component.

[0044] The shape of the solid acid catalyst is not particularly limited, but from the perspective of hydrolysis reaction efficiency and glucose yield, it is preferred to be in particulate, powder, or flake form. The size (average particle size) of the solid acid catalyst is not particularly limited, but is preferably 0.1 μm to 10000 μm. The average particle size is a value determined by the method described in the examples below.

[0045] From the perspective of improving the efficiency of hydrolysis reaction and glucose yield, the matrix is ​​preferably a porous matrix (porous body), more preferably a porous body with mesopores (mesoporous body), and even more preferably mesoporous silica.

[0046] In this invention, a mesopore refers to a pore with an average pore diameter of 2 nm to 50 nm.

[0047] When the matrix is ​​porous, its properties or physical characteristics, such as average pore size, specific surface area, and total pore volume, are not particularly limited and can be appropriately determined. For example, considering the hydrolysis reaction efficiency and glucose yield, an average pore size of 2 nm to 10 nm is preferred, and more preferably 2 nm to 5 nm. Considering the hydrolysis reaction efficiency and glucose yield, a specific surface area of ​​10 nm is preferred. 2 / g~3000m 2 / g, more preferably 100m 2 / g~2000m 2 / g. The total pore volume, considering hydrolysis efficiency and glucose yield, is preferably 0.1 mL / g to 2 mL / g, more preferably 0.2 mL / g to 1 mL / g. The average pore size, specific surface area, and total pore volume of the porous matrix are values ​​determined by the methods described in the examples below.

[0048] Solid acid catalysts typically contain carbon in their matrix. In this invention, "carbon in the matrix" means that carbon is present on the surface and / or inside the matrix. Examples include: carbon loaded or adsorbed on the surface of the matrix (carbon-loaded matrix), carbon contained inside the matrix (the matrix is ​​formed from a complex of silica and carbon), and carbon present on both the surface and inside the matrix. Regarding the morphology (structure) of the carbon in the solid acid catalyst, from the perspective of enabling the surface functional groups (described later) to bond or immobilize on the surface, thereby improving the hydrolysis reaction efficiency and glucose yield, a carbon-loaded or adsorbed matrix is ​​preferred.

[0049] In this invention, the surface of the substrate generally refers to the outer surface, but when the substrate is porous, it includes the inner surface of the pores in addition to the outer surface. On the other hand, the interior of the substrate refers to the portion that is not exposed to the surface.

[0050] There is no particular limitation on the carbon content of the solid acid catalyst. However, considering the potential to improve the efficiency of the hydrolysis reaction and the yield of glucose, the carbon content of the solid acid catalyst (excluding the mass of the sulfonium group) is preferably 1% to 70% by mass, more preferably 5% to 50% by mass. The carbon content in the solid acid catalyst is the value determined by the determination method described in the examples below.

[0051] The solid acid catalyst used in the manufacturing method of this invention typically has a titanium matrix. In this invention, a titanium matrix means that titanium is present on the surface and / or inside the matrix. Examples include: titanium being loaded or adsorbed on the surface of the matrix (titanium-loaded matrix), titanium being contained inside the matrix (the matrix being formed from a composite of silica and titanium), and titanium being present on both the surface and inside the matrix. In solid acid catalysts, when the matrix has titanium on its surface and / or inside, the efficiency of the hydrolysis reaction and the glucose yield can be improved.

[0052] There is no particular limitation on the titanium content in the solid acid catalyst. However, considering the potential to improve the efficiency of the hydrolysis reaction and the glucose yield, the titanium content (excluding the mass of carbon atoms and sulfonyl groups) of the solid acid catalyst is preferably 0.1% to 10% by mass, more preferably 0.5% to 5% by mass. The carbon content in the solid acid catalyst is a value determined by the method described in the examples below.

[0053] Solid acid catalysts containing carbon and titanium elements can be appropriately combined in the manner described above. However, from the perspective of improving hydrolysis reaction efficiency and glucose yield, it is preferable to combine a method in which titanium elements are contained on the surface and / or inside the matrix with a method in which carbon elements are loaded or adsorbed on the surface of the matrix (the solid acid catalyst of this manner is also called a carbon-supported silica-titanium composite mesoporous body).

[0054] The solid acid catalyst used in the manufacturing method of this invention has a sulfonyl group as a surface functional group. In this invention, the solid acid catalyst having a sulfonyl group as a surface functional group means that the sulfonyl group is chemically bonded to the surface of the matrix and / or carbon element. As long as it can promote the hydrolysis reaction of cellulose, some or all of the sulfonyl group can become a salt.

[0055] There is no particular limitation on the content of sulfonyl groups in the solid acid catalyst. However, considering the potential to improve the efficiency of the hydrolysis reaction and the yield of glucose, the amount present per 1g of solid acid catalyst is preferably 0.01mmol / g to 2mmol / g, more preferably 0.05mmol / g to 1mmol / g. The content of sulfonyl groups in the solid acid catalyst is a value determined by the determination method described in the examples below.

[0056] Commercially available solid acid catalysts can be used, but due to the presence of carbon and titanium elements and sulfonyl groups, it is preferable to use appropriately synthesized substances.

[0057] There are no particular limitations on the method of introducing carbon into the matrix, and various known methods can be used. For example, as a method of loading or adsorbing carbon onto the surface of the matrix, methods of mixing the matrix and a carbon source and then carbonizing the carbon source can be listed. Specifically, the method described in Non-Patent Document 1 can be listed. As for the carbon source, there are no particular limitations as long as it is a compound containing carbon atoms. Organic compounds are usually used, such as sugars like sucrose, alcohols like furfuryl alcohol, hydrocarbon compounds, and epoxides.

[0058] There are no particular limitations on the method of introducing titanium into the matrix, and various known methods can be used. For example, as a method for loading or adsorbing titanium onto the surface of the matrix, methods similar to those described above for loading or adsorbing carbon can be used, except for the use of titanium-containing compounds. On the other hand, as a method for containing titanium in the interior or both the interior and surface of the matrix, methods such as forming the matrix using a mixture of a silica precursor compound (described later) and a titanium-containing compound (described later), such as the sol-gel method (described later), can be used.

[0059] There are no particular limitations on the method of introducing sulfonyl groups into the matrix, and various known methods can be used. For example, methods that treat the matrix with sulfuric acid, preferably a matrix on which carbon elements are loaded or adsorbed, can be cited. Specifically, the method described in Non-Patent Document 1 can be cited.

[0060] Methods for manufacturing porous silica bodies as the matrix of solid acid catalysts include: the sol-gel method (also known as the "molecular template method" or "template method") using a silica source (silica precursor compound) and an amphiphilic compound as a template.

[0061] The following explanation uses the sol-gel method to illustrate a method for manufacturing carbon-supported silica-titanium composite mesoporous bodies with sulfonyl groups as surface functional groups, suitable for use as solid acid catalysts.

[0062] A typical sol-gel method involves, for example, subjecting a silica precursor compound to a sol-gel reaction (hydrolysis and condensation) around self-assembled micelle particles formed by a cationic surfactant to form an inorganic-organic nanocomposite, followed by calcination or acid treatment (to remove the cationic surfactant).

[0063] Regarding the suitable solid acid catalyst described above, firstly, a silica-titanium composite mesoporous body containing titanium elements on the surface and / or inside the matrix is ​​manufactured using the sol-gel method described above. At this time, except that the titanium precursor compound described later is used together with the silica precursor compound (so that the silica precursor compound and the titanium precursor compound coexist), the process can be carried out in the same manner as the conventional sol-gel method. Therefore, the types of steps, operations, and reaction conditions in each step of the sol-gel method used in manufacturing the silica-titanium composite mesoporous body can be appropriately determined with reference to the conventional sol-gel method. For example, refer to the method described in Non-Patent Document 1, and the series of steps, operations, and reaction conditions in the synthesis method of the examples described later.

[0064] In the above sol-gel method, by changing the type of silica precursor compound, especially the type of amphiphilic compound, or the preparation conditions such as solvent composition, temperature, and time, the properties or physical properties of the porous body, such as the size (average pore diameter) and shape of the mesopores, as well as the skeletal shape of the porous body, can be adjusted or changed, which is the same as the general sol-gel method.

[0065] As the amphiphilic compound used as the template, compounds commonly used in conventional sol-gel methods can be used without particular limitation. Amphiphilic surfactants are commonly used, with cationic surfactants and block copolymers being preferred. In this invention, considering the ability to set a smaller average pore size of the mesopores and further improve the hydrolysis reaction efficiency and glucose yield, cationic surfactants are preferred as the template. As the cationic surfactant, surfactants commonly used as templates in sol-gel methods can be used without particular limitation, such as ammonium cationic surfactants. As ammonium cationic surfactants, alkyl ammonium salts are preferred, tetraalkyl ammonium salts are preferred, ammonium salts containing long-chain (6 or more carbon atoms) straight-chain alkyl groups are more preferred, and mono-long-chain straight-chain alkyl tri-short-chain (4 or less carbon atoms) alkyl ammonium salts are particularly preferred. The anion forming the quaternary ammonium salt is not particularly limited, and inorganic anions such as hydroxide ions, halide ions, and perhalate ions can be included.

[0066] It should be noted that, as a representative of silica mesoporous bodies prepared by the sol-gel method using cationic surfactants, examples include MCM-41, etc., and as a representative of silica porous bodies prepared by the sol-gel method using block copolymers, examples include SBA-15, etc.

[0067] As a precursor compound for silica, compounds commonly used in conventional sol-gel methods can be used without particular limitation, such as silicon halides, hydroxides, alkoxides, etc., with silicon alkoxides and / or alkyl alkoxides being preferred. The number of carbon atoms in the alkyl group forming the alkyl alkoxide is not particularly limited, but is preferably 1 to 6, more preferably 1 to 3.

[0068] In the above sol-gel method, a titanium-containing compound is used together with a silica precursor compound. Examples of titanium-containing compounds include titanium precursor compounds that are converted into titanium element by the sol-gel method together with a silica precursor compound. Preferred titanium precursor compounds are titanium halides, hydroxides, alkoxides, etc., and more preferably titanium alkoxides and / or titanium alkyl alkoxides (alkoxytitanium). The number of carbon atoms in the alkyl group forming the alkyl alkoxide is not particularly limited, but is preferably 1 to 6, and more preferably 1 to 3.

[0069] Next, carbon elements are loaded or adsorbed onto the surface of the resulting silica-titanium composite mesoporous body. There are no particular limitations on the method for loading or adsorbing carbon elements, as described above.

[0070] Sulfonyl groups are introduced as surface functional groups onto the carbon-loaded silica-titanium composite mesoporous bodies obtained in this manner. The method of introducing sulfonyl groups is not particularly limited, as described above.

[0071] Silica-titanium composite mesoporous bodies, carbon-supported silica-titanium composite mesoporous bodies, and / or carbon-supported silica-titanium composite mesoporous bodies with introduced sulfonyl groups can also be appropriately crushed or broken.

[0072] [The process of contacting a liquid containing cellulose and water with a solid acid catalyst]

[0073] The manufacturing method of the present invention includes a step of contacting a liquid (reaction solution) containing cellulose and water with the solid acid catalyst of the present invention. Through this contact, cellulose can be hydrolyzed in the presence of the solid acid catalyst, thereby converting it into glucose.

[0074] The components used in this contact process can be one type or two or more types.

[0075] Regarding the hydrolysis of cellulose occurring in the contact process, it is generally believed that hydrolysis occurs from cellulose to oligosaccharides and from oligosaccharides to glucose. Therefore, in the contact process, as a hydrolysis treatment (saccharification treatment) of cellulose, a sugar-containing solution (also called "saccharified solution" or "cellulose decomposition product") containing glucose is obtained. This sugar-containing solution typically contains glucose as the main component, in addition to water and a solid acid catalyst, and also contains other components. Other components that may be present in the sugar-containing solution include: partial hydrolysis products of cellulose, reaction products of glucose, etc., such as: oligosaccharides of tetramer or higher, cellotriose, cellobiose, mannose, fructose, L-glucan, and other sugars, as well as 5-hydroxymethylfurfural, furfural, etc. It should be noted that in this invention, the main component refers to the component with the highest mass among the contained components.

[0076] In the contact process using the solid acid catalyst of the present invention, the hydrolysis of cellulose is highly efficient, and various side reactions that occur relative to the hydrolysis reaction that produces glucose are suppressed or promoted, thus enabling glucose to be obtained with high selectivity and high yield. Therefore, the sugar-containing solution obtained in the contact process contains glucose as the main component and other components in low amounts. For example, an example of a sugar-containing solution can be described as one containing glucose as the main component and containing cellobiose, fructose, L-glucan, 5-hydroxymethylfurfural (HMF), and furfural in low total amounts.

[0077] The suitable sugar-containing solution obtained in the contact process has the following composition: when supplied for LC analysis with a differential refractive index detector, the total area of ​​peaks from components with molecular weights lower than glucose is 0.01 to 0.2 times that of peaks from glucose. It is known that when the area ratio of the total area value to the area of ​​peaks from glucose (hereinafter, sometimes referred to as the "component area ratio") is 0.01 to 0.2 times, cellulose can be converted to glucose with high selectivity in the contact process. With the improved composition and properties of this suitable sugar-containing solution, by using it as a feedstock for the ethanol fermentation of glucose, side reactions can be suppressed or promoted, thereby allowing the ethanol fermentation of glucose to proceed preferentially as the main reaction. Furthermore, even in the presence of acetic acid bacteria, their proliferation and acetic acid fermentation can be highly inhibited, further improving the yield and selectivity (content) of ethanol in the ethanol fermentation. From the perspective of further improving the efficiency of ethanol fermentation and further inhibiting the proliferation of acetic acid bacteria and acetic acid fermentation, thereby enabling the production of ethanol with high yield and high selectivity, the above-mentioned component area ratio is preferably 0.05 to 0.2 times, more preferably 0.1 to 0.2 times. Here, the above-mentioned component area ratio is a value determined by the method described in the examples described later.

[0078] A suitable sugar-containing solution may contain the partial hydrolysis products of cellulose, reaction products such as glucose, etc., but must satisfy the above-mentioned component area ratio of components with a molecular weight lower than glucose (sometimes called "low molecular weight components") as identified by LC analysis. As for low molecular weight components, they cannot be uniquely determined due to variations in the source and composition of cellulose used in the hydrolysis reaction, the contact conditions between glucose and the solid acid catalyst, etc. Generally, components with a molecular weight lower than glucose, such as the partial hydrolysis products of cellulose and reaction products such as glucose, can be listed. Examples include: L-glucan, HMF, furfural, etc., as well as components that cannot be identified; preferably, L-glucan, HMF, and furfural.

[0079] The glucose content in a suitable sugar-containing solution cannot be uniquely determined as described above, but it is at least 0.01 to 0.2 times the area ratio of the aforementioned components, and is within the preferred or more preferred range of the aforementioned component area ratio. From the perspective of efficiently producing ethanol, the glucose content in a suitable sugar-containing solution, based on the mass ratio of all components contained in the cellulose decomposition composition, is preferably 50% to 99% by mass, more preferably 83% to 99% by mass.

[0080] In the manufacturing method of the present invention, cellulose can undergo a highly efficient hydrolysis reaction to obtain glucose as the main component. The cellulose conversion rate and glucose selectivity (the mass ratio of glucose content to the content of other components) vary depending on the type of cellulose, the type or amount of solid acid catalyst used, and the hydrolysis reaction conditions, and therefore cannot be uniquely determined. However, at least the glucose yield can be 45% or higher.

[0081] In the manufacturing method of the present invention, a liquid (reaction solution) containing cellulose and water is brought into contact with a solid acid catalyst under appropriate reaction conditions, typically under heating.

[0082] The contact method can be any method that allows the three components—cellulose, water, and the solid acid catalyst—to come into contact. Examples include: contacting a pre-prepared reaction solution with the solid acid catalyst; and contacting cellulose, water, and the solid acid catalyst without pre-preparing a reaction solution (such as contacting cellulose with the solid acid catalyst in the presence of water). In the contacting process of this invention, when contacting or adding the reaction solution to the solid acid catalyst, methods include contacting or adding cellulose and water separately to the solid acid catalyst instead of the reaction solution.

[0083] As a contact step, heating is performed, for example, after adding the reaction solution and solid acid catalyst to a sealed container. The heating temperature (reaction temperature) for the hydrolysis reaction is not particularly limited, and can be set to, for example, 110°C to 200°C. From the perspective of improving the efficiency of cellulose hydrolysis and suppressing the byproducts of other components, thereby increasing the glucose yield, the heating temperature is preferably 120°C to 180°C, more preferably 120°C to 150°C. The heating time (reaction time) can be appropriately determined according to the heating temperature, the efficiency (conversion rate) of the cellulose hydrolysis reaction, the glucose yield, etc., and can be set to, for example, 1 hour to 48 hours. The sealed container under heating can be at atmospheric pressure, typically a pressurized state with a water vapor partial pressure, for example, exceeding 0.1 MPa. In this invention, the hydrolysis reaction can also be carried out under an actively pressurized environment. There are no particular limitations on this pressure, for example, it can be greater than 0.1 MPa and less than 20 MPa, preferably 0.1 MPa to 10 MPa. The reaction environment (atmosphere) is not particularly limited, and can be an inactive gas atmosphere, an air atmosphere, or a water vapor atmosphere. For industrial manufacturing purposes, the reaction environment is preferably an air atmosphere and / or a water vapor atmosphere.

[0084] There are no particular limitations on the amount of reaction solution and solid acid catalyst used, but the amount of water in the reaction system (the amount of water present) must be at least the amount required for the hydrolysis of cellulose. Considering the mixability (stirring ability), operability, hydrolysis efficiency, and glucose yield of the reaction system, the amount of water in the reaction system relative to the amount of cellulose is preferably 0.1 to 1000 times by mass, more preferably 1 to 100 times by mass. It should be noted that in the contacting process, water can also be added separately from the reaction solution. The aforementioned amount of water in the reaction system refers to the amount of water from the reaction solution; however, in the case of added water, it is the total amount of water from the reaction solution and the added water.

[0085] The amount of solid acid catalyst used can be appropriately determined by taking into account the reaction conditions, hydrolysis efficiency and glucose yield, etc. For example, it is preferably 0.01 to 10 times the mass of cellulose, and more preferably 0.1 to 5 times the mass of cellulose.

[0086] The contact process can be carried out batchwise using a closed container such as an autoclave, or continuously using a reaction tube filled with a solid acid catalyst. In the batch process, considering the hydrolysis efficiency and glucose yield, it is preferable to mix the reaction solution and the solid acid catalyst by appropriate methods such as stirring or shaking. As for the continuous process, for example, a method of passing the reaction solution continuously or intermittently through a heated reaction tube can be cited.

[0087] As described above, cellulose is hydrolyzed in the presence of a solid acid catalyst to obtain a mixture (also known as a reaction mixture) of a sugar solution containing glucose as the main component and a solid acid catalyst.

[0088] [Post-processing steps]

[0089] In the manufacturing method of the present invention, the reaction mixture can be post-processed after the above-described contact step to obtain glucose. Examples of post-processing of the reaction mixture include: a step of cooling the reaction mixture and a step of performing solid-liquid separation on the reaction mixture.

[0090] The reaction mixture can also be separated into solid and liquid components without cooling, but cooling is preferred to inhibit further glucose reactions, or for workability and safety reasons. Cooling of the reaction mixture can be natural cooling or cooling using various cooling media. There are no particular limitations on the cooling temperature of the reaction mixture; it can generally be set below 100°C. From the perspective of inhibiting further glucose reactions while maintaining a high glucose yield, it is preferably below 80°C. Considering workability and safety, it is preferably near room temperature (e.g., 15°C to 40°C). As a lower limit for the cooling temperature, for example from a workability perspective, it can be set above 0°C, preferably above 15°C. The cooling rate can be appropriately determined, preferably decreasing by 0.1°C to 10°C per minute. The cooling time can be appropriately determined based on the heating temperature and cooling rate.

[0091] The reaction mixture, after appropriate cooling, undergoes solid-liquid separation to separate a sugar-containing liquid (cellulose decomposition liquid) with glucose as the main component as the liquid phase and at least a solid acid catalyst and unreacted cellulose as the solid phase. There are no particular limitations on the method for solid-liquid separation; examples include filtration, centrifugation, and precipitation.

[0092] [Other processes]

[0093] In the manufacturing method of the present invention, steps other than the contact step and post-processing step described above may also be performed. For example, steps such as separating and purifying glucose from the separated and recovered sugar-containing solution; separating solid acid catalyst and unreacted cellulose from the separated and recovered solid phase; washing and regenerating the separated solid acid catalyst; removing impurities, inclusions, etc. from the waste when the above-mentioned waste is used as a cellulose source; and removing lignin from the cellulose are also steps.

[0094] The separation and purification of glucose can be achieved using any known separation and purification methods without particular limitations. Furthermore, the solid acid catalyst used in this invention can be reused in its separated and recovered state (e.g., as a mixture with unreacted cellulose) without requiring separation, cleaning, or regeneration steps. However, the catalytic activity of the solid acid catalyst typically decreases gradually with repeated use; therefore, cleaning and / or regeneration of the solid acid catalyst may be considered, taking into account factors such as decreased catalyst activity, hydrolysis efficiency, or glucose yield. There are no particular limitations on the cleaning and regeneration methods.

[0095] The manufacturing method of the present invention, through a simple and safe process of contacting the reaction solution with the solid acid catalyst of the present invention, enables the production of glucose from cellulose in a relatively short time and at a high yield. Furthermore, the post-processing step after the contacting process is also simple and safe, allowing the reuse of the separated and recovered solid acid catalyst. In addition, during the hydrolysis reaction of cellulose, various side reactions can be suppressed and promoted, thus enabling the production of glucose with high selectivity (high purity). As a result, the manufacturing method and the solid acid catalyst of the present invention are suitable as a method for producing bioethanol from inedible biomass. Moreover, when using waste paper pulp as the cellulose source, the efficiency of the cellulose hydrolysis reaction and the glucose yield can be further improved, and inedible biomass resources can be effectively utilized. Therefore, the manufacturing method and the solid acid catalyst of the present invention enable the low-cost and efficient production of glucose from cellulose, and are also suitable for the industrialization of cellulose hydrolysis reactions (glucose production methods) and bioethanol production methods.

[0096] Example

[0097] The present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0098] [Preparation of solid acid catalysts]

[0099] <Experimental Example 1-1. Preparation of a solid acid catalyst (i) for the production of glucose containing Ti>

[0100] (1) Preparation of porous silica (i)

[0101] (First process)

[0102] A 16% (w / w) aqueous solution of hexadecyltrimethylammonium hydroxide (625.5 g) was stirred, and a mixed solution of 9.25 g tetraisopropyl titanate and 50.0 g 2-propanol was added dropwise at room temperature (25 °C). After stirring for 30 minutes, 190.5 g tetramethyl orthosilicate was added dropwise. Then, 5.0 g 2-propanol was added, and stirring continued for 3 hours, resulting in the formation of a precipitate.

[0103] (Second process)

[0104] The precipitate was filtered and separated, and then washed with 5 L of ion-exchanged water. The resulting cleaned solid was dried under reduced pressure at 100 °C for 5 hours.

[0105] (Third process)

[0106] 20g of the dried solid obtained in the second step was placed in a flask, and a mixed solution of 200mL methanol and 10g concentrated hydrochloric acid (36% by mass) was added (acid treatment). While stirring, the mixture was heated at reflux temperature for 1 hour. After natural cooling, the liquid phase was removed by filtration. The same operation was repeated using a mixture of 200mL methanol and 5g concentrated hydrochloric acid. Finally, the mixture was refluxed with 200mL methanol for 1 hour, and the final filtered solid was dried under reduced pressure at 120℃ and 10mmHg for 1.5 hours.

[0107] (Fourth process)

[0108] The solid obtained in the third process was heat-treated (calcined) at 600°C for 3 hours under air circulation.

[0109] (Fifth process)

[0110] The calcined solid obtained in the fourth step was pulverized eight times using a hammer mill to obtain a powdered porous silica body (i) with an average particle size of 10 μm.

[0111] The average particle size was measured using a laser diffraction / scattering particle size distribution measuring device (LA-950 manufactured by Horiba Corporation) with ion-exchanged water as the dispersion medium, and calculated on a volume basis.

[0112] The powdered silica porous body (i) prepared as described above is a silica-titanium composite mesoporous body with a specific surface area of ​​1160 m². 2 / g, total pore volume is 0.60mL / g, and average pore size is 2.1nm.

[0113] It should be noted that the specific surface area and total pore volume were determined by measuring the nitrogen adsorption isotherm at liquid nitrogen temperature using a BELS0RP MINI X (manufactured by Microtrac BEL) after vacuum degassing the silica porous body (i) at 120°C for 2 hours, based on the BET method and the value of nitrogen adsorption near the relative pressure (P / P0=0.96). Furthermore, the average pore size was calculated from the total pore volume and specific surface area using the following (Equation 1).

[0114] (Equation 1): Average pore size (nm) = 4 × total pore volume (mL / g) / specific surface area (m²) 2 / g)×1000 The Ti concentration in the powdered porous silica (i) prepared as described above was analyzed by XRF and found to be 1.5% by mass.

[0115] (2) Preparation of silica porous-carbon composite (i)

[0116] In 2.5 g of porous silica (i), furfuryl alcohol (FA), serving as a carbon source, was vacuum impregnated into the pores of the porous silica at room temperature. After impregnation, the FA on the outer surface of the porous silica was cleaned with mesitylene, and then heated at 150 °C for 24 hours to polymerize the FA within the pores. After polymerization, the filtered solid was dried under reduced pressure at 120 °C for 12 hours. The resulting solid was then heat-treated at 550 °C for 3 hours under a nitrogen atmosphere to carbonize the polymerized FA within the pores, thus preparing a porous silica-carbon composite (i) serving as the mesoporous body of a carbon-supported silica-titanium composite.

[0117] (3) Preparation of solid acid catalyst (i)

[0118] 1 g of a porous silica-carbon composite (i) and 20 mL of 95% sulfuric acid were added to an autoclave, and the mixture was treated at 150 °C for 15 hours. After treatment, the mixture was washed with water at 50 °C until the pH of the washing solution showed the same value as purified water. After washing, the filtered solid was dried under reduced pressure at 120 °C for 12 hours to obtain 1 g of a solid acid catalyst (i) consisting of a carbon-supported porous silica-titanium composite with sulfonyl groups as surface functional groups.

[0119] <Experimental Example 1-2. Preparation of Ti-free solid acid catalyst (ii)>

[0120] (1) Preparation of silica porous-carbon composite (ii)

[0121] A solid acid catalyst (ii) was prepared using the same method as described in Non-Patent Literature 1 (average pore size of 6 nm to 8 nm (literature value)).

[0122] The preparation method is shown below.

[0123] 6.4 g of Pluronic F127 (a reagent manufactured by Fujifilm and Kojun Pharmaceutical Co., Ltd.) as a template surfactant was added to a solution obtained by mixing 32 g of ethanol and 0.3 g of concentrated hydrochloric acid, and the mixture was ultrasonically treated for 1 hour. Next, 8.32 g of tetraethoxysilane (TEOS) as a silica source and 10 g of sucrose aqueous solution as a carbon source were added, and the mixture was ultrasonically treated again for 1 hour. The mass ratio of Si in TEOS to C in sucrose was Si:C = 33:66. Then, the mixture was heated at 40°C for 20 hours to evaporate the ethanol, and then heated at 160°C for 24 hours to induce thermal polymerization. After thermal polymerization, the resulting solid was carbonized by heat treatment at 550°C for 3 hours in an electric furnace under a nitrogen atmosphere, thus preparing a silica porous-carbon composite (ii).

[0124] (2) Preparation of solid acid catalyst (ii)

[0125] 1 g of a porous silica-carbon composite (ii) and 20 mL of 95% sulfuric acid were added to an autoclave, and the mixture was treated at 150 °C for 24 hours. After treatment, the mixture was washed with water at 50 °C until the pH of the washing solution showed the same value as purified water. After washing, the filtered solid was dried under reduced pressure at 120 °C for 12 hours to obtain the solid acid catalyst (ii).

[0126] <Experimental Examples 1-3. Preparation of Ti-free solid acid catalysts (iii)>

[0127] (1) Preparation of silica porous-carbon composite (iii)

[0128] Commercially available MCM-41 (a reagent manufactured by Sigma-Aldrich, Ti-free, with an average pore size of 2.1 nm to 2.7 nm (catalog value)) was used as the silica porous material. Furfuryl alcohol (FA), serving as the carbon source, was vacuum impregnated into the pores of MCM-41 at room temperature in 2.5 g of MCM-41. After impregnation, the FA on the outer surface of MCM-41 was cleaned with mesitylene, and then heated at 150 °C for 24 hours to polymerize the FA within the pores. After polymerization, the filtered solid was dried under reduced pressure at 120 °C for 12 hours. The resulting solid was then heat-treated at 550 °C for 3 hours under a nitrogen atmosphere to carbonize the polymerized FA within the pores, thus preparing the silica porous material-carbon composite (iii).

[0129] (2) Preparation of solid acid catalyst (iii)

[0130] 1 g of a porous silica-carbon composite and 20 mL of 95% sulfuric acid were added to an autoclave, and the mixture was treated at 150 °C for 24 hours. After treatment, the mixture was washed with water at 50 °C until the pH of the washing solution showed the same value as purified water. After washing, the filtered solid was dried under reduced pressure at 120 °C for 12 hours to obtain the solid acid catalyst (iii).

[0131] <Experimental Example 2. Determination of Carbon Content in Silica Porous-Carbon Composites>

[0132] The carbon content of the silica porous carbon composites (i) to (iii) was determined by the weight loss rate obtained by thermogravimetric analysis. Thermogravimetric analysis was performed by increasing the furnace temperature to 1000°C at a rate of 5°C / min in an air atmosphere. The results are shown in Table 1.

[0133] [Table 1]

[0134] <Experimental Example 3. Determination of Sulfonyl Content in Solid Acid Catalysts>

[0135] The sulfonyl content of solid acid catalysts (i) and (ii) was determined by titration using an automatic potentiometric titration apparatus (Kyoto Electronics). 50 mg of each solid acid catalyst was measured into a screw-top flask, and 30 mL of a 0.05 N NaCl aqueous solution was added using a full-volume pipette. The mixture was stirred for 15 hours. After stirring, the solution in the screw-top flask was filtered, and 10 mL of the filtrate was transferred to a 50 mL beaker using a full-volume pipette. Two drops of phenolphthalein solution were added to the 50 mL beaker using a Pasteur pipette, followed by titration with 0.1 mL of a 0.005 N NaOH aqueous solution added dropwise. The Na+ content was calculated based on the equivalent point of the titration results. + The amount of exchange was used to determine the sulfonium content. The results are shown in Table 2.

[0136] [Table 2]

[0137] <Example 1>

[0138] (1) Hydrolysis of cellulose

[0139] The cellulose used as the reaction substrate was cellulose that had undergone the following treatment.

[0140] 1 kg of zirconia balls (1 cm in diameter) and 5 g of microcrystalline cellulose (Avicel PH-101, a reagent manufactured by Sigma-Aldrich) were added to a ceramic jar mill. The mill was placed on the rotary table of a benchtop jar mill and milled at 200 rpm for 120 hours.

[0141] In an autoclave equipped with a stirrer, 50 mg of ball-milled cellulose, 50 mg of solid acid catalyst (i), and 5 mL of purified water were added. While stirring at 300 rpm, the temperature was increased from room temperature to 150 °C over approximately 30 minutes, and then the cellulose hydrolysis reaction was carried out at 150 °C for 24 hours (internal pressure 0.5 MPa). After the reaction was completed, the autoclave was cooled to room temperature. The reaction solution was then filtered to separate the liquid and solid, yielding the cellulose decomposition solution (i) and solid residue (i).

[0142] (2) High-performance liquid chromatography (HPLC) analysis

[0143] Cellulose decomposition solution (i) was subjected to HPLC analysis, and the glucose concentration (mass %) in the cellulose decomposition solution (i) was quantified using an absolute calibration curve method with glucose reagent. HPLC analysis was performed under the following conditions: LC-20A (Shimadzu Corporation) was used, with a Shodex SP0810 column (Resonac Corporation, 8 mm inner diameter, 300 mm length) as the column, purified water (0.5 mL / min) as the mobile phase, a differential refractive index detector (RID-20A) as the detector, a column temperature of 70 °C, an injection volume of 20 μL, an analysis time of 70 min, and a sampling rate of 100 ms.

[0144] (3) Determination of solid residue

[0145] The mass of unreacted cellulose is obtained by subtracting the mass of the added solid acid catalyst from the mass of the solid residue (i) measured after drying at 100°C for 12 hours.

[0146] (4) Calculation of glucose yield

[0147] Based on the amount of glucose obtained and the amount of cellulose input calculated by Equation 2 below, the glucose yield is obtained by Equation 3 below.

[0148] (Equation 2): Glucose yield (mg) = (mass of glucose breakdown solution (i)) × (glucose concentration) / 100 Here, the glucose concentration used in (Equation 2) is the glucose concentration (mass %) determined in (2) above.

[0149] (Equation 3): Glucose yield (%) = (Glucose obtained) / (Cellulose input) × 100 The component area ratio of the cellulose decomposition solution was calculated using the chromatogram obtained from HPLC analysis of the cellulose decomposition solution, as described below.

[0150] An example of a chromatogram obtained by HPLC analysis of a cellulose decomposition solution is shown below. Figure 1 Regarding the component area ratio of the cellulose decomposition solution, chromatograms were used to identify the types of each component in the cellulose decomposition products. Specifically, the components detected in the chromatograms were identified by comparing, for example, the retention times of the compounds in the aforementioned Shodex SP0810 column.

[0151] Next, the peak area values ​​of glucose and the components with lower molecular weights eluted after the retention time of glucose in the obtained chromatogram were obtained by processing with the following waveform processing parameters. Regarding the waveform processing parameters used in peak detection, the area values ​​were calculated under the conditions of a slope of 200 μV / min, a width of 5 seconds, and a minimum area counted as 1000 (minimum area / height).

[0152] Using the area values ​​of each component obtained in this way, the component area ratio is calculated by dividing the peak area value from glucose by the sum of the peak area values ​​from low molecular weight components.

[0153] The component area ratio of the cellulose decomposition liquid (i) calculated by the above method is in the range of 0.01 to 0.2 times.

[0154] <Comparative Example 1>

[0155] Except that the hydrolysis of cellulose was carried out without the addition of a solid acid catalyst, the procedure was the same as in Example 1, and the glucose yield was determined.

[0156] <Comparative Example 2>

[0157] Except that a solid acid catalyst (ii) was used instead of a solid acid catalyst (i), the procedure was the same as in Example 1, and the glucose yield was determined.

[0158] <Comparative Example 3>

[0159] Except that a solid acid catalyst (iii) was used instead of a solid acid catalyst (i), the procedure was the same as in Example 1, and the glucose yield was determined.

[0160] The results of the hydrolysis of cellulose in Example 1 and Comparative Examples 1-3 are shown in Table 3.

[0161] [Table 3]

[0162] It can be seen that Comparative Example 1, which did not use a solid acid catalyst, and Comparative Examples 2 and 3, which used solid acid catalysts (ii) or (iii) that did not contain Ti, had low glucose yields and were not suitable for industrial use.

[0163] In contrast, Example 1, which used a solid acid catalyst (i) containing Ti, achieved a glucose yield as high as 70%. Although Example 1 used commercially available cellulose for the hydrolysis reaction, the results show that similar results can be obtained even when using cellulose from waste paper pulp. In this invention, although the detailed reasons for obtaining a high glucose yield are not yet clear, it is conceivable that the carbon coating formed during the preparation of the silica porous-carbon composite (i) is a structure suitable for the hydrolysis reaction of cellulose due to the catalytic effect of the Ti element contained in the silica porous body (i).

[0164] It is evident that the manufacturing method and solid acid catalyst of the present invention, through a simple and safe process, enable the production of glucose at low cost and with sufficiently high yield, preferably with high selectivity (high purity), even in industrial manufacturing. Therefore, the manufacturing method and solid acid catalyst of the present invention are suitable as a method and solid acid catalyst for producing bioethanol from inedible biomass, and are suitable for the industrial production of cellulose hydrolysis and bioethanol manufacturing processes.

[0165] The invention has been described together with its embodiments, but it is understood that, unless otherwise stated, no detail in the description is intended to limit the invention, and it should be interpreted broadly without departing from the spirit and scope of the invention as shown in the appended claims.

[0166] This application claims priority based on Japanese Patent Application No. 2024-000266 filed in Japan on January 4, 2024, the contents of which are incorporated herein by reference as part of the description herein.

Claims

1. A method for producing glucose, said glucose production method comprising a step of contacting a liquid containing cellulose and water with a solid acid catalyst, wherein, This solid acid catalyst contains carbon, titanium, and silicon dioxide, and has sulfonyl groups as surface functional groups.

2. The manufacturing method according to claim 1, wherein, The silicon dioxide has mesopores.

3. The manufacturing method according to claim 1 or 2, wherein, The carbon element is loaded onto the surface of the silicon dioxide.

4. The manufacturing method according to claim 1 or 2, wherein, The titanium element is contained in the silicon dioxide.

5. The manufacturing method according to claim 3, wherein, The titanium element is contained in the silicon dioxide.

6. A solid acid catalyst for glucose production, wherein, The solid acid catalyst for glucose production contains carbon, titanium, and silicon dioxide, and has sulfonyl groups as surface functional groups.

7. The solid acid catalyst for glucose production according to claim 6, wherein, The silicon dioxide has mesopores.

8. The solid acid catalyst for glucose production according to claim 6 or 7, wherein, The carbon element is loaded onto the surface of the silicon dioxide.

9. The solid acid catalyst for glucose production according to claim 6 or 7, wherein, The titanium element is contained in the silicon dioxide.

10. The solid acid catalyst for glucose production according to claim 8, wherein, The titanium element is contained in the silicon dioxide.

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