JP6648545B2 - Method for producing sugar liquid for furfural production raw material and method for producing furfural - Google Patents

Description

  The present invention relates to a method for producing a furfural raw material sugar liquid from a non-edible biomass resource, and a method for producing furfural from the produced furfural production raw material sugar liquid.

  Furfural, which can be obtained from non-edible biomass resources, can be used as a raw material for producing furfuryl alcohol and tetrahydrofuran, and can be converted into a plant-derived polymer material such as furan resin and PTMG (polytetramethylene ether glycol), respectively. Compound.

  To produce furfural from non-edible biomass resources, the non-edible biomass resources are reacted in a solvent in the presence of an acid catalyst to produce monosaccharides having 5 carbon atoms (such as xylose) or monosaccharides having 5 carbon atoms. A sugar solution containing a polysaccharide (xylan) as a constituent component is obtained, and as shown in the following formula, xylan in this sugar solution is hydrolyzed to xylose, and xylulose generated by isomerization of xylose is subjected to a dehydration reaction to furfural. Convert to

  As an acid catalyst, a method using sulfuric acid (Patent Document 1), a method using an ion exchange resin (Patent Document 2), and a method using an organic acid such as acetic acid (Patent Document 3) are known.

WO 2013/101999 pamphlet JP 2013-253069 A JP-A-54-039071

  In the conventional furfural production method, furfural cannot be stably produced at a high yield, and an improvement in the furfural yield is desired.

  The present invention has been made in view of the above problems, and when producing furfural from a non-edible biomass resource via a saccharide having 5 carbon atoms, furfural is produced stably and efficiently in high yield. An object of the present invention is to provide a method for producing a sugar liquid for furfural production raw material and a method for producing furfural.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the weight of a monosaccharide having 5 carbon atoms and a polysaccharide having a monosaccharide having 5 carbon atoms as constituent components in a sugar solution obtained from a non-edible biomass resource. By controlling the average molecular weight within a certain range, the inventors have found that the above problems can be solved, and have completed the present invention.
That is, the gist of the present invention resides in the following [1] to [12].

[1] In a reaction vessel, a non-edible biomass resource is used as a raw material, a reaction is performed in the presence of a solvent and a catalyst, and a sugar liquid is extracted from the obtained reaction liquid to produce a sugar liquid for furfural production raw material. The method for producing furfural, wherein the sugar solution comprises a monosaccharide having 5 carbon atoms and a polysaccharide having a monosaccharide having 5 carbon atoms as constituents, and the weight average molecular weight of the monosaccharide and the polysaccharide is 200 to 1,000. Method for producing sugar solution for use.
[2] The method for producing a sugar solution for furfural production raw materials according to [1], wherein the content of the monosaccharide having 5 carbon atoms in the sugar solution to be extracted is controlled to 0.05% by weight or more and 8% by weight or less. .
[3] controlling the content of 2 to 4 saccharides among the polysaccharides in the sugar solution to be extracted to 20% by weight or more based on the content of monosaccharide having 5 carbon atoms, [1] or [2] ] The method for producing a sugar liquid for furfural production raw materials according to [1] .
[4] The furfural according to any of [1] to [3], wherein the content of disaccharides among the polysaccharides in the sugar solution to be extracted is controlled to 0.01% by weight or more and 5% by weight or less. A method for producing a sugar liquid for production raw materials.
[5] The furfural according to any one of [1] to [4], wherein the content of tetrasaccharide among the polysaccharides in the sugar solution to be extracted is controlled to 0.005% by weight or more and 3% by weight or less. A method for producing a sugar liquid for a production raw material.
[6] The method for producing a sugar solution for furfural production raw materials according to any one of [1] to [5], wherein the non-edible biomass resource is bagasse.
[7] The method for producing a sugar liquid for furfural production raw materials according to any one of [1] to [6], wherein the catalyst is an organic acid.
[8] The method for producing a sugar solution for furfural as described in [7], wherein the organic acid is at least one of formic acid, acetic acid, and lactic acid.
[9] The method for producing a sugar solution for furfural production raw materials according to any one of [1] to [8], wherein the solvent is water.
[10] The method for producing a sugar liquid for furfural production raw materials according to any one of [1] to [8], wherein the solvent is a mixed solvent of water and an organic solvent.
[11] The method for producing a sugar liquid for furfural production raw materials according to [10], wherein the organic solvent is a hydrocarbon solvent.
[12] A method for producing furfural, using the sugar solution obtained by the method for producing a sugar solution for furfural production raw material according to any one of [1] to [11].

  According to the present invention, when producing furfural from a non-edible biomass resource via a saccharide having 5 carbon atoms, furfural can be produced stably and efficiently in a high yield.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist.

  The method for producing a sugar liquid for a furfural production raw material of the present invention comprises, in a reaction vessel, using a non-edible biomass resource as a raw material, performing a reaction in the presence of a solvent and a catalyst, and extracting the sugar liquid from the obtained reaction liquid. In the method for producing a sugar solution for furfural production raw material, the sugar solution is a monosaccharide having 5 carbon atoms and a polysaccharide having a monosaccharide having 5 carbon atoms as constituents (hereinafter, these may be referred to as “C5 saccharides”. And the weight average molecular weight of the monosaccharide and polysaccharide is 200 or more and 1000 or less.

  The method for producing furfural of the present invention is characterized in that furfural is produced using the sugar solution for furfural production raw materials produced by this method.

  The method for producing furfural from non-edible biomass resources is a method for producing a sugar solution containing C5 saccharides from non-edible biomass resources, and a method for producing furfural by dehydrating C5 saccharides in the sugar solution. Although there is a production step, in the present invention, the sugar liquid production step and the furfural production step may be performed in one reactor, or may be performed in separate reactors.

<Action mechanism>
The present inventors have conducted the following investigations on the cause of the inability to obtain furfural stably with a high yield in the conventional method.
That is, in the conventional method, a sugar solution containing a monosaccharide having 5 carbon atoms and a polysaccharide having a monosaccharide having 5 carbon atoms obtained from a non-edible biomass resource is obtained, and the monosaccharide having 5 carbon atoms in the sugar solution is obtained. Is hydrolyzed to monosaccharide having 5 carbon atoms, and then subjected to a furfural production process as a furfural production raw material sugar liquid.
However, monosaccharides easily produce high-boiling compounds by polymerization, and the reaction rate of this high-boiling reaction is high. For this reason, there are many saccharides contained in the monosaccharide state in the sugar solution for furfural production raw materials, and if the saccharides are kept in the monosaccharide state for a long time, they can become a raw material of furfural due to the high boiling of the monosaccharides. However, this results in a decrease in the furfural yield.

Even if the proportion of polysaccharide in the sugar solution is large and the amount of monosaccharide converted to furfural by the dehydration reaction is small, consumption of monosaccharide due to high boiling can be prevented, whereas if oligosaccharide is used, the conversion to monosaccharide is reduced. Since the hydrolysis rate is high, the monosaccharide is hydrolyzed in the reaction system, and furfural can be obtained by a dehydration reaction of the monosaccharide generated by hydrolysis of the oligosaccharide.
Therefore, monosaccharides and polysaccharides are contained as sugars in the sugar solution so that the weight-average molecular weight thereof is within a predetermined range. By suppressing the reaction, the selectivity of furfural can be increased, and as a result, the yield of furfural can be increased. In addition, since high-molecular-weight saccharides are hydrolyzed into low-molecular-weight saccharides, a preferable balance between monosaccharides and polysaccharides can be well expressed by using the weight-average molecular weight as an index.

  The present inventors have found that furfural can be stably obtained at a high yield by the above-mentioned action mechanism when the weight average molecular weight is 200 or more and 1000 or less, and completed the present invention.

<Non-edible biomass resources>
The non-edible biomass resource used in the present invention is not particularly limited as long as it contains a polysaccharide having a saccharide as a component.Specifically, bagasse, switchgrass, napier grass, Elianthus, Miscanthus, kenaf, Corn stover, corn cob, beet pulp, palm empty fruit bun, rice straw, straw, rice bran, tree, wood, vegetable oil scum, sasa, bamboo, pulp, waste paper, food waste, marine products residue, livestock waste, etc. . Further, molasses remaining after collecting sugar from molasses generated in the process of producing sugar can also be used as a non-edible biomass raw material. Among these, bagasse, corn stover, corn cob, and rice straw are preferred from the viewpoint of raw material availability and cost, bagasse and corn cob are more preferred, and bagasse is particularly preferred. Non-edible biomass resources differ from edible biomass resources in that they do not compete with edible uses and are usually discarded or incinerated, so that stable supply and effective use of resources can be achieved. preferable.

  These non-edible biomass resources can be used as they are, or can be used after pretreatment such as acid treatment or hydrothermal treatment. These non-edible biomass resources may be used alone or in combination of two or more. The non-edible biomass resource may be supplied to the reactor in a solid state, or may be supplied in a slurry state by mixing with a solvent such as water.

  The weight-average diameter of the non-edible biomass is preferably 0.5 mm or more, more preferably 1 mm or more, and particularly preferably 2 mm or more, as the length of the longest part of the grains, from the viewpoint of handleability and reaction efficiency. Further, it is preferably 50 mm or less, more preferably 25 mm or less, and particularly preferably 10 mm or less.

<C5 saccharide>
The C5 saccharide contained in the sugar solution for furfural production raw material produced in the present invention is not particularly limited as long as it is derived from a non-edible biomass resource and can produce furfural by a dehydration reaction.

  Specific examples of the monosaccharide having 5 carbon atoms (pentose) include ribose, lyxose, xylose, arabinose, deoxyribose, xylulose, and ribulose. Among these monosaccharides, xylose and arabinose are preferable, and xylose is more preferable, from the viewpoints of availability of raw materials and yield, because these monosaccharides are abundant in natural and plant components.

  Specific examples of the polysaccharide having the above-mentioned monosaccharide having 5 carbon atoms as a constituent include disaccharides such as xylobiose and arabinobiose; trisaccharides such as xylotriose and arabinotriose; Oligosaccharides such as xylo-oligosaccharides and arabino-oligosaccharides containing saccharides, and polysaccharides of xylan, araban, and hemicellulose are exemplified. Among these polysaccharides, xylo-oligosaccharides, xylan, and hemicellulose are preferable from the viewpoint of yield, and among them, xylo-oligosaccharides are particularly preferable. Here, the xylo-oligosaccharide has disaccharides and trisaccharides as main components, and further contains 4 to 6 saccharides.

According to the present invention, the sugar liquid for furfural production raw materials produced from non-edible biomass resources contains these monosaccharides and one or more polysaccharides.
In the sugar solution, a monosaccharide such as glucose having a different carbon number from the C5 saccharide or a polysaccharide such as glucan may coexist.

<Sugar liquid production reaction>
The reaction for producing a sugar liquid containing a C5 saccharide from the non-edible biomass resource is a reaction for producing a C5 saccharide by hydrolyzing a hemicellulose component in the non-edible biomass resource. This reaction is performed using a reaction solvent and a catalyst from the viewpoint of improving the productivity of the C5 saccharide and improving the purity of the obtained C5 saccharide.

  Hereinafter, the reaction for producing the sugar solution will be described.

(Non-edible biomass concentration)
In the reaction for producing a sugar liquid from a non-edible biomass resource, the concentration of the non-edible biomass contained in the reaction solvent is not particularly limited, but the ratio of the non-edible biomass to the solvent is 0.1 to 200% by weight. It is preferably 5 to 40% by weight, more preferably 10 to 30% by weight. When the ratio of the non-edible biomass to the solvent is equal to or more than the lower limit, the energy required for separating the solvent tends to be low, and further, the capacity of the reaction system can be reduced and the construction cost of the equipment can be reduced. There is a tendency. When the ratio of the non-edible biomass to the solvent is equal to or less than the upper limit, side reactions can be suppressed, and the yield of C5 saccharides and furfural tends to increase, which is preferable.

(catalyst)
The catalyst used in the production reaction of the sugar liquid from the non-edible biomass resource may be any catalyst capable of producing C5 saccharides from the non-edible biomass, and is not particularly limited, and may be an inorganic catalyst such as sulfuric acid, phosphoric acid, nitric acid, and hydrochloric acid. Acid catalysts such as organic acids such as acids, carboxylic acids and sulfonic acids, and heteropolyacids are exemplified. Among these, organic acids are preferred from the viewpoints of stability, corrosiveness, waste treatment and unit price, and carboxylic acids are particularly preferred.

Specific examples of carboxylic acids include aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, levulinic acid, and lactic acid. Acids: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, aconitic acid, itaconic acid, oxaloacetic acid, fumaric acid, cis-1,2-cyclopentanedicarboxylic acid Acid, trans-1,2-cyclopentanedicarboxylic acid, cis-1,3-cyclopentanedicarboxylic acid, trans-1,3-cyclopentanedicarboxylic acid, cis-1,2-cyclohexanedicarboxylic acid, trans-1,2 -Cyclohexanedicarboxylic acid, cis-1,3-cyclohexanedicarboxylic acid aliphatic dicarboxylic acids such as trans-1,3-cyclohexanedicarboxylic acid, cis-1,4-cyclohexanedicarboxylic acid, and trans-1,4-cyclohexanedicarboxylic acid; 1,2,4-cyclohexanetricarboxylic acid, 1,3 Aliphatic tricarboxylic acids such as 5-cyclohexanetricarboxylic acid; aromatic carboxylic acids such as benzoic acid and naphthalenecarboxylic acid; phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, trimellitic acid, hemi-mellitic acid, melophanic acid, prenitic acid And aromatic polycarboxylic acids such as pyromellitic acid, benzenepentacarboxylic acid and melitic acid; and heterocyclic carboxylic acids such as furan carboxylic acid and furandicarboxylic acid. Also, salts obtained by neutralizing at least a part of these acids can be used.
Among these, formic acid, acetic acid, lactic acid, and levulinic acid, which are acids obtained from non-edible biomass, are preferable, and formic acid, acetic acid, and lactic acid are particularly preferable.

  In particular, from the viewpoint of the yield of C5 saccharide, among the above carboxylic acids, those having an acid dissociation constant pKa of 3 or more and 5 or less, particularly 3.0 or more and 4.6 or less are preferable. Here, the acid dissociation constant pKa is a numerical value when the dissociation stage is 1. That is, in the case of a carboxylic acid having two or more carboxyl groups, it means an acid dissociation constant pKa when at least one hydrogen ion among the two or more carboxyl groups is eliminated. For example, in the case of succinic acid having two carboxyl groups, the pKa is usually 4.19 at a dissociation stage of 1.19 and 5.48 at a dissociation stage of 2. PKa of succinic acid.

  One of the above carboxylic acids may be used alone, or two or more may be used in combination.

Specific examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, and naphthalenesulfonic acid. Also, salts obtained by neutralizing at least a part of these acids can be used.
One of the above sulfonic acids may be used alone, or two or more thereof may be used in combination.

Specific examples of the heteropolyacid include phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphanadomolybdic acid, and cisvanadomolybdic acid. Also, salts obtained by neutralizing at least a part of these acids can be used.
One of the above heteropoly acids may be used alone, or two or more thereof may be used in combination.

  Further, two or more of the above carboxylic acids, sulfonic acids, and heteropoly acids may be used as a mixture at an arbitrary ratio. Further, it is preferable that the catalyst be separated and recycled in the process.

  The amount of the catalyst used in the sugar liquid production reaction can be appropriately set based on the type of the catalyst, the reaction conditions and the like, and is not particularly limited, but is preferably 0.01 to 50% by weight based on the solution amount. Yes, more preferably 0.5 to 30% by weight, particularly preferably 1 to 20% by weight. Here, the “solution” refers to a reaction solution containing a reaction solvent, a non-edible biomass raw material, and a catalyst described below. When the amount of the catalyst is equal to or more than the lower limit, the reaction rate tends to be high, and the productivity of C5 saccharide tends to be improved. When the amount of the catalyst is equal to or less than the upper limit, side reactions are suppressed, and the selectivity of C5 saccharide tends to be improved.

(Reaction solvent)
The reaction solvent used in the production reaction of the sugar liquid from the non-edible biomass resources is water or a mixed solvent of water and an organic solvent. That is, the reaction can be performed using only water, but the reaction can also be performed by adding an organic solvent. When an organic solvent is used, the reaction can be carried out with a homogeneous mixed solvent, but an organic solvent which is a two-phase system of an aqueous phase and an organic phase can also be used. The amount of the organic solvent to be used is not particularly limited as long as the purpose of the present invention is not impaired, but is preferably from 10 to 5,000% by weight, particularly preferably from 10 to 1,000% by weight, based on water.

  Examples of the organic solvent include, but are not limited to, ethers having 4 to 20 carbon atoms such as tetrahydrofuran; alcohols having 3 to 20 carbon atoms such as 1-propanol and 2-propanol; pentane, hexane, C3-12 saturated aliphatic hydrocarbons such as cyclohexane, heptane, octane, nonane, decane, dodecane, isododecane; toluene, xylene, diethylbenzene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene (tetralin) , Aromatic hydrocarbons such as 1-methylnaphthalene, lactones such as γ-butyrolactone and γ-valerolactone, glycols such as polyethylene glycol, glycol ethers such as polyethylene glycol dimethyl ether, and others, sulfolane, isosorbide, and isosorbide. Dimethyl ether, propylene carbonate and the like.

  Among them, an aqueous solvent which is a homogeneous mixed solvent with water or a non-polar solvent in which the above-mentioned acid catalyst is difficult to dissolve is preferable. When the reaction is carried out in a two-phase system, toluene, xylene, diethylbenzene, trimethylbenzene, 1,2, Hydrocarbon solvents such as 3,4-tetrahydronaphthalene (tetralin), 1-methylnaphthalene, cyclohexane and isododecane are preferred, and in particular, toluene, xylene, diethylbenzene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene (tetralin), Aromatic hydrocarbon solvents such as 1-methylnaphthalene are particularly preferred.

  The above-mentioned organic solvent is preferably a single solvent in consideration of the recovery and reuse of the solvent, but two or more organic solvents may be used.

(Reaction conditions)
The reaction temperature of the sugar liquid production reaction is not particularly limited, but is specifically preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 160 ° C. or higher and 250 ° C. or lower. Preferably, it is 230 ° C. or less. When the reaction temperature is equal to or higher than the lower limit, the progress of the reaction tends to be fast, and the productivity of C5 saccharide production is improved. When the reaction temperature is lower than the above upper limit, the sequential reaction and decomposition of the C5 saccharide are suppressed, and the yield of the C5 saccharide tends to be improved, which is preferable.

  Although the heating method is not particularly limited, a method in which the temperature of the reaction solution is increased by a heat exchanger, a method in which steam is directly introduced into the reaction solution, and a method in which a solvent separated after the reaction is recycled is used in a high-temperature process. A method of heating using a liquid in a process having a high temperature is particularly preferable from the viewpoint of using thermal energy efficiently.

  The reaction time of the sugar liquid production reaction varies depending on the amounts and types of raw materials and catalysts used and the reaction temperature, but is specifically preferably 0.02 hours or more, more preferably 0.1 hour or more, and particularly preferably 0.1 hour or more. The time is preferably at least 2 hours and at most 5 hours, more preferably at most 2 hours, particularly preferably at most 1 hour. When the reaction time is longer than the above lower limit, the progress of the reaction is promoted, and the yield of C5 saccharide tends to be improved. When the reaction time is shorter than the above upper limit, the decomposition of C5 saccharide and the sequential reaction are performed. This is preferable since it tends to increase the yield of C5 saccharides.

  The preferred range of the reaction pressure varies depending on the reaction temperature, but is preferably 0.1 to 5.0 MPaG, more preferably 0.5 to 3.0 MPaG, and particularly preferably 1.0 to 2.5 MPaG.

(Reaction format)
The reaction format of the sugar liquid production reaction is not particularly limited, and may be a batch system, a semi-batch system, a continuous system, or a combination of these. From the viewpoint of improving productivity, a semi-batch reaction and a continuous reaction are preferable, and from the viewpoint of simplicity of operation, a batch reaction is preferable. From the viewpoint of solid-liquid contact, a rotary reactor is preferred. A single reactor may be used, or a plurality of reactors may be combined.

(Solid-liquid separation)
After the production reaction of the sugar solution, the solid-liquid separation method for separating the reaction residue of the non-edible biomass resource from the reaction solution is not particularly limited, but may be a filter press, a belt filter, a screw press, a roll press, a conveyor dryer, an Oliver filter, a precoat. A filter, a disc filter, a belt press, a Guina centrifugal separator, a rotary pressure dehydrator, a multiple disc dehydrator, a hollow fiber membrane filter, a cross-flow centrifugal filter dehydrator, and the like can be preferably used. , A roll press is more preferable, and a roll press is particularly preferable. The solid-liquid separation may be performed after the production of the sugar liquid, may be performed after the production of furfural by a dehydration reaction, or may be performed during the production of the sugar liquid or furfural.

(Weight average molecular weight of saccharide and content of saccharide)
In the present invention, a sugar solution having a weight average molecular weight of 200 to 1,000 is obtained by the above sugar solution production reaction. That is, the reaction conditions are controlled so that a sugar solution having a weight average molecular weight of the C5 saccharide of 200 to 1,000 is obtained.
The weight average molecular weight is more preferably 220 or more and 800 or less, and particularly preferably 250 or more and 500 or less. When the weight average molecular weight is not less than the above lower limit, the polymerization of monosaccharides is suppressed, and the furfural yield tends to be improved.When the weight average molecular weight is not more than the above upper limit, the dehydration reaction rate is increased. , The furfural yield tends to be improved.

  The content of the monosaccharide having 5 carbon atoms in the sugar solution is not particularly limited as long as it satisfies the above-mentioned range of the weight average molecular weight, but may be controlled to be 0.05% by weight or more and 8% by weight or less. Preferably, the control is performed so as to be 0.1% by weight or more and 5% by weight or less, and it is particularly preferable that the control is performed so as to be 0.1% by weight or more and 3% by weight or less. In particular, it is preferable to control so that xylose is contained in the above range as a monosaccharide having 5 carbon atoms. When the number of monosaccharides having 5 carbon atoms is equal to or more than the lower limit, the dehydration reaction rate tends to increase, and the yield of furfural tends to be improved. , And the furfural yield tends to be improved.

  The content of the 2 to 4 saccharides among the polysaccharides having 5 carbon atoms in the sugar solution as a component is not particularly limited as long as the weight average molecular weight is in the above range. Is preferably controlled to be at least 20% by weight, more preferably at least 30% by weight, and particularly preferably at least 50% by weight. . On the other hand, the total content of the 2 to 4 saccharides is preferably 500% by weight or less, particularly 300% by weight or less, particularly preferably 200% by weight or less based on the monosaccharide having 5 carbon atoms. When the content of the 2 to 4 saccharides is equal to or more than the lower limit, the monosaccharide constituent ratio decreases, so that the polymerization of the monosaccharide tends to be suppressed and the furfural yield tends to be improved.

  The content of disaccharides among the polysaccharides having a monosaccharide having 5 carbon atoms as a component in the sugar solution is not particularly limited as long as the above-mentioned range of the weight average molecular weight is satisfied. %, Preferably 0.05% to 4% by weight, more preferably 0.1% to 3% by weight. Is particularly preferred. When the content of the disaccharide is equal to or more than the lower limit, the monosaccharide constituent ratio is reduced, so that the polymerization of the monosaccharide is suppressed, and the yield of furfural tends to be improved. When the content of the disaccharide is equal to or less than the upper limit, the rate of dehydration reaction is increased, and the yield of furfural tends to be improved.

  The content of the trisaccharide among the polysaccharides having a monosaccharide having 5 carbon atoms as a component in the sugar solution is not particularly limited as long as the weight average molecular weight is in the above-mentioned range, but the content is 0.01% by weight or more and 4% by weight. %, More preferably 0.05% to 3% by weight, more preferably 0.1% to 2% by weight. Is particularly preferred.

  The content of the tetrasaccharide in the polysaccharide having the monosaccharide having 5 carbon atoms as a constituent component in the sugar solution is not particularly limited as long as it satisfies the above-mentioned range of the weight average molecular weight, but is 0.005% by weight or more and 3% by weight. %, Preferably at least 0.01% by weight and at most 2% by weight, more preferably at least 0.1% by weight and at most 1% by weight. Is particularly preferred. When the content of the tetrasaccharide is equal to or more than the above lower limit, the monosaccharide constituent ratio decreases, so that the polymerization of the monosaccharide tends to be suppressed and the furfural yield tends to be improved. When the content of the tetrasaccharide is equal to or less than the above upper limit, the rate of the dehydration reaction is increased, and the furfural yield tends to be improved.

Usually, most of the polysaccharides in the sugar solution are oligosaccharides having 6 or less saccharides.
The total content of the polysaccharide having a monosaccharide having 5 carbon atoms as a constituent component in the sugar solution is not particularly limited as long as it satisfies the above-mentioned range of the weight average molecular weight. %, Preferably 0.5% by weight or more and 5% by weight or less, more preferably 0.7% by weight or more and 3% by weight or less. Is particularly preferred.

The weight average molecular weight of the C5 saccharide and the content of monosaccharides and 2 to 4 saccharides contained in the sugar liquid can be appropriately controlled by the reaction conditions when producing the sugar liquid from non-edible biomass resources.
That is, when the reaction temperature is increased, hydrolysis proceeds to produce more monosaccharides, and as a result, the weight average molecular weight decreases. Conversely, when the reaction temperature is lowered, the progress of hydrolysis is slowed, and a large amount of polysaccharide remains, resulting in an increase in the weight average molecular weight.
Further, when the reaction time is lengthened, a large amount of monosaccharide is generated due to the progress of hydrolysis, and as a result, the weight average molecular weight is reduced. Conversely, if the reaction time is short, hydrolysis is not sufficiently performed, and a large amount of polysaccharide remains, so that the weight average molecular weight increases.
In addition, the weight-average molecular weight can be controlled by adjusting the rate of progress of hydrolysis depending on the amount of catalyst used, the type of catalyst used, and the like.
Furthermore, when the weight average diameter of the raw material is reduced, the solid-liquid contact efficiency is improved and the rate of progress of the hydrolysis is increased, so that the weight average molecular weight is reduced. Conversely, if the weight average diameter of the raw material is large, the hydrolysis rate becomes slow, and a large amount of polysaccharide remains, so that the weight average molecular weight increases.
Accordingly, the weight average molecular weight of the C5 saccharide contained in the obtained sugar solution and each The sugar content can be controlled.

  The weight average molecular weight in the sugar solution is determined by liquid chromatography analysis of the sugar solution to determine the content of each C5 saccharide, and is calculated from the content and molecular weight of each C5 saccharide, as described in Examples below. Can be.

<Furfural production reaction>
The furfural production reaction performed in the present invention is a reaction in which C5 saccharides in the sugar solution obtained in the above sugar solution production reaction are dehydrated in the presence of a catalyst to produce furfural. This dehydration reaction is preferably carried out using a reaction solvent and a catalyst from the viewpoint of improving the productivity of furfural and improving the purity of the obtained furfural.

(C5 sugar concentration of sugar solution)
The concentration of the C5 saccharide in the saccharide liquid produced according to the method for producing a sugar liquid for furfural production raw materials of the present invention described above and subjected to a dehydration reaction for producing furfural is not particularly limited, but the ratio of the C5 saccharide to the sugar liquid Is preferably 0.1 to 50% by weight, more preferably 1 to 30% by weight, and still more preferably 4 to 10% by weight. When the content of the C5 saccharide in the sugar solution is equal to or more than the above lower limit, the energy required for separating furfural and the solvent after the dehydration reaction tends to decrease, and further, the capacity of the reaction system decreases, Construction costs also tend to be reduced. When the C5 saccharide concentration is equal to or lower than the upper limit, side reactions can be suppressed, and the yield of furfural tends to increase, which is preferable.

(catalyst)
The catalyst used in the furfural production reaction of the present invention is not particularly limited as long as it is an acid catalyst capable of producing furfural from C5 saccharides, and is the same as the catalyst used in the sugar liquid production reaction from the non-edible biomass resources described above. The preferred catalyst is also the same as in the above-mentioned reaction for producing a sugar solution from non-edible biomass resources.

  The amount of the catalyst used in the furfural production reaction can be appropriately set based on the type of the catalyst, the reaction conditions, and the like, and is not particularly limited, but is preferably 0.01 to 50% by weight based on the solution amount. , More preferably 0.5 to 30% by weight, particularly preferably 1 to 20% by weight. Here, the “solution” refers to a reaction solution containing a reaction solvent, a C5 saccharide and a catalyst described below. When the amount of the catalyst is equal to or more than the lower limit, the reaction rate tends to be high, and the productivity of furfural tends to be improved. Further, since furfural has a property of polymerizing under acidic conditions, it is preferable that the amount of the catalyst be equal to or less than the above upper limit, since side reactions are suppressed and the selectivity of furfural tends to be improved.

(Reaction solvent)
The reaction solvent used in the furfural production reaction is preferably water or a mixed solvent of water and an organic solvent. That is, as in the case of the sugar liquid production reaction from non-edible biomass resources, the reaction can be carried out only with water, but the reaction can also be carried out by adding an organic solvent. From the viewpoint of cost advantage, it is preferable to use only water as the reaction solvent, and from the viewpoint of improving the yield of furfural, it is preferable to use water and an organic solvent as the reaction solvent.

  The reaction can be carried out in a homogeneous mixed solvent by the addition of an organic solvent.However, since the polymerization and decomposition reaction of furfural is suppressed and the yield of furfural is improved, an organic solvent that is a two-phase system of an aqueous phase and an organic phase is used. Preferably, it is used. The amount of the organic solvent to be used is not particularly limited as long as the purpose of the present invention is not impaired, but is preferably from 10 to 5,000% by weight, particularly preferably from 10 to 1,000% by weight, based on water.

The organic solvent used is not particularly limited, and any of the organic solvents used in the sugar liquid production reaction from the non-edible biomass resources can be used, and the same applies to a suitable organic solvent. is there.
In the production reaction of furfural, a single solvent is preferred as the organic solvent in consideration of the recovery and reuse of the solvent, but two or more organic solvents may be used.

(Reaction conditions)
Although the reaction temperature of the furfural production reaction is not particularly limited, it is specifically preferably 100 ° C or higher, more preferably 120 ° C or higher, still more preferably 160 ° C or higher, and preferably 250 ° C or lower. , More preferably 230 ° C or lower. When the reaction temperature is higher than the lower limit, the reaction rate tends to increase, and the furfural productivity is improved. When the reaction temperature is lower than the above upper limit, the decomposition and polymerization of furfural and raw material saccharides are suppressed, and the yield of furfural tends to be improved, which is preferable.

  The reaction time of the furfural production reaction varies depending on the composition of the sugar solution, the amount of the catalyst used, the type, and the reaction temperature, but is specifically preferably 0.02 hours or more, more preferably 0.1 hour or more, and particularly preferably 0 hour or more. 0.5 hours or more, preferably 5 hours or less, more preferably 2 hours or less. When the reaction time is at least the lower limit, the furfural yield tends to be improved by accelerating the progress of the reaction and improving the conversion, and when the reaction time is at most the upper limit, furfural is reduced. It is preferable because the decomposition and polymerization are suppressed and the yield of furfural tends to be improved.

  The preferred range of the reaction pressure varies depending on the reaction temperature, but is preferably 0.1 to 5.0 MPaG, more preferably 0.5 to 3.0 MPaG, and particularly preferably 1.0 to 2.5 MPaG.

(Reaction format)
The reaction format of the furfural production reaction is not particularly limited, and may be a batch system, a semi-batch system, a continuous system, or a combination of these. From the viewpoint of improving productivity, a semi-batch reaction and a continuous reaction are preferable, and from the viewpoint of simplicity of operation, a batch reaction is preferable. In the continuous reaction, a continuous tube reactor or a continuous tank reactor can be used. Further, a reactive distillation method in which distillation is performed while producing a furfural as a reaction product may be used. For example, as described in WO2013 / 102027, a method for continuously extracting a mixture of furfural and water by using a furfural production reactor as a reactive distillation system, or as described in WO2012 / 115706. A method of continuously extracting furfural from an aqueous phase using an organic solvent can also be used. In the case of the reactive distillation method, it may be carried out under reduced pressure or at normal pressure. A single reactor may be used, or a plurality of reactors may be combined.

(Recovery furfural)
As described above, in order to recover furfural from the reaction solution containing furfural obtained by the dehydration reaction of the C5 saccharide in the sugar solution, the dehydration reaction solution is usually separated into an organic layer containing furfural and an aqueous layer. After separation into two layers, furfural contained in the organic layer is purified by distillation or the like to obtain furfural as a product.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist.

  In the following examples, the analysis of moisture was carried out by the Karl Fischer method (measured by Mitsubishi Chemical Corporation CA-21). The analysis of the amount of furfural (FRL) in the crude furfural was performed by gas chromatography (GC) and calculated by an internal standard method (using dioxane as an internal standard substance).

The content of each sugar in the sugar solution was analyzed by liquid chromatography (LC) under the following conditions.
Equipment name: Waters Alliance 2690 Tosoh CO-8010
Analysis column: Shodex Sugar KS-801 300 mm x 8.0 mm + Shodex Sugar KS-802 300 mm x 8.0 mm
Mobile phase: water Detector: RI
The sample was filtered with an aqueous chromato disk (0.45 μm), and the filtrate was used for measurement.
In addition, the molecular weight of the xylo-oligosaccharide of 2-4 saccharides calculated the weight average molecular weight as trisaccharide.

[Example 1]
<Manufacture of sugar liquid>
6.0 g of bagasse (weight average diameter 1 to 3 mm), 27.1 g of demineralized water as a reaction solvent, and 0.93 g of lactic acid as a catalyst were placed in a 100 mL micro autoclave, and the vessel was sealed. Replaced. The contents were heated to 190 ° C. over 8 minutes while stirring the contents in a 240 ° C. oil bath (attained pressure: 1.3 MPa), and the container was taken out. After the vessel was cooled, it was opened, 6.0 g of bagasse (weight average diameter 1 to 3 mm) was charged again, the vessel was sealed, and the internal space was replaced with nitrogen. The contents were heated to 190 ° C. over 8 minutes while stirring the contents in a 240 ° C. oil bath (attained pressure: 1.3 MPa), and the container was taken out.

  After the completion of the reaction, the vessel was allowed to cool to room temperature, and the entire reaction solution in the autoclave was recovered. The bagasse residue was separated from the reaction solution by solid-liquid separation. The total content of saccharides (hereinafter, referred to as “monosaccharides”) and 2 to 4 saccharides (hereinafter, referred to as “2 to 4 saccharides”) composed of monosaccharides having 5 carbon atoms was determined by LC analysis. Then, the total ratio (percentage) of 2 to 4 sugars to monosaccharide (hereinafter referred to as “2 to 4 sugars / monosaccharide”) was calculated. From the analysis results of monosaccharides and total saccharides in the sugar solution, the weight average molecular weight of the monosaccharide having 5 carbon atoms and the polysaccharide containing the monosaccharide having 5 carbon atoms (hereinafter referred to as “C5 sugar average molecular weight”). ) Was calculated. Table 1 shows the results.

<Manufacture of furfural>
Of the above separated liquid (sugar liquid), 20.1 g was put into a 100 mL micro autoclave, 4.9 g of lactic acid and 20.1 g of tetralin as a solvent were added, the vessel was sealed, and the internal space was replaced with nitrogen. . The content was heated to 190 ° C. while stirring, and the reaction was carried out by heating and stirring at 190 ° C. and 1.3 MPaG for 30 minutes.
After the completion of the reaction, the mixture was allowed to cool to room temperature while maintaining the stirring, and the entire reaction liquid in the autoclave was collected to obtain crude furfural.

  The amount of FRL in the crude furfural was measured, and the molar fraction (percentage) of furfural relative to the total amount of C5 saccharides in the sugar solution subjected to the dehydration reaction was calculated as a C5 sugar-based FRL yield. The mole fraction (percentage) of furfural with respect to the amount of bagasse provided in Example 1 was calculated as a bagasse-based FRL yield. Table 1 shows the results.

<Comparative Example 1>
In Example 1, 16.0 g of bagasse (weight average diameter 1 to 3 mm) was placed in a 100 mL micro autoclave, 29.0 g of demineralized water was used as a reaction solvent, and 8.3 g of lactic acid was used as a catalyst to produce a sugar solution, and furfural was produced. The production of sugar solution and the production of furfural were carried out in the same manner except that lactic acid was not added at times, and the results are shown in Table 1.

  From Table 1, it can be seen that by controlling the weight average molecular weight of the C5 saccharide in the sugar solution within the range of the present invention, furfural can be obtained in a high yield and is useful in industrial production of furfural. .

Claims (12)

In a reaction tank, a non-edible biomass resource is used as a raw material, a reaction is performed in the presence of a solvent and a catalyst, and a sugar liquid is extracted from the obtained reaction solution, in a method for producing a sugar liquid for furfural production raw material,
A ratio of the non-edible biomass to the solvent is 0.1 to 40% by weight,
The sugar solution for furfural production raw material, wherein the sugar solution contains a monosaccharide having 5 carbon atoms and a polysaccharide having a monosaccharide having 5 carbon atoms as constituents, and the weight average molecular weight of the monosaccharide and the polysaccharide is 200 to 1,000. Manufacturing method.   The method for producing a sugar solution for furfural production raw material according to claim 1, wherein the content of the monosaccharide having 5 carbon atoms in the sugar solution to be extracted is controlled to be 0.05% by weight or more and 8% by weight or less.   The furfural according to claim 1 or 2, wherein the content of 2 to 4 saccharides among the polysaccharides in the extracted sugar solution is controlled to 20% by weight or more based on the content of monosaccharide having 5 carbon atoms. A method for producing a sugar liquid for production raw materials.   The sugar liquid for furfural production raw materials according to any one of claims 1 to 3, wherein the content of disaccharides among the polysaccharides in the sugar liquid to be extracted is controlled to 0.01% by weight or more and 5% by weight or less. Manufacturing method.   The sugar liquid for furfural production raw materials according to any one of claims 1 to 4, wherein the content of tetrasaccharides among the polysaccharides in the extracted sugar liquid is controlled to 0.005% by weight or more and 3% by weight or less. Manufacturing method.   The method according to any one of claims 1 to 5, wherein the non-edible biomass resource is bagasse.   The method for producing a sugar liquid for furfural production raw materials according to any one of claims 1 to 6, wherein the catalyst is an organic acid.   The method for producing a sugar liquid for furfural production raw materials according to claim 7, wherein the organic acid is at least one of formic acid, acetic acid, and lactic acid.   The method for producing a sugar solution for a furfural production raw material according to any one of claims 1 to 8, wherein the solvent is water.   The method according to any one of claims 1 to 8, wherein the solvent is a mixed solvent of water and an organic solvent.   The method according to claim 10, wherein the organic solvent is a hydrocarbon solvent. A furfural production method for producing furfural using the sugar liquid obtained by the method for producing a furfural production raw material sugar liquid according to any one of claims 1 to 11.
Manufacturing method.