JP2018090545A - Method for producing furfural - Google Patents

Abstract

The present invention provides an industrially and economically advantageous continuous production method of furfural that can stably and efficiently produce furfural from non-edible biomass resources.
SOLUTION: Using a non-edible biomass resource as a raw material, a reaction is carried out in a solvent in the presence of a catalyst to obtain a sugar solution containing C5 sugar, and the C5 sugar in the sugar solution is converted to furfural by a dehydration reaction. To obtain a reaction liquid containing furfural and circulate and use at least a part of the residual liquid after separating and removing the furfural from the reaction liquid as a circulating liquid in the reaction system, wherein the circulating liquid is an organic acid. Of 0.1 to 50% by weight and furfural in an aqueous solution of 40 to 200 ° C. containing furfural in an amount of 0.01 to 2% by weight.
[Selection figure] None

Description

  The present invention relates to a method for producing furfural using non-edible biomass resources as a raw material.

  Furfural that can be obtained from non-edible biomass resources can be used as a raw material for the production of furfuryl alcohol and tetrahydrofuran, and can be converted into plant-derived polymer raw materials such as furan resin and PTMG (polytetramethylene ether glycol), respectively. A compound.

  In order to produce furfural from a non-edible biomass resource, the non-edible biomass resource is reacted in the presence of a catalyst in a solvent to obtain a monosaccharide having 5 carbon atoms (such as xylose) and / or a monosaccharide having 5 carbon atoms. A sugar solution containing polysaccharides such as xylooligosaccharides is obtained, and the sugars in the sugar solution are hydrolyzed into xylose. As shown in the following formula, xylulose produced by isomerization of xylose is dehydrated. Let it convert to furfural. As the reaction solvent, water is usually used.

  In Patent Document 1, as a reaction solvent for producing furfural from a lignocellulose raw material, a hydrophobic organic solvent such as toluene, methyl isobutyl ketone, cyclohexane, and corn oil is used as a reaction solvent together with water, and the reaction is performed in a two-phase system. Have been described. In Patent Document 1, an excessive amount of a hydrophobic organic solvent is used with respect to water. Specifically, it is used in a ratio of organic solvent: aqueous solution = 170: 5 to 140: 20 (weight ratio), and the amount of the organic solvent used is about 7 to 34 times the weight of water.

  In order to recover furfural from a reaction liquid containing furfural generated by dehydration reaction (hereinafter sometimes referred to as “crude furfural”), the reaction liquid containing furfural is separated into two layers, an organic layer and an aqueous layer. The furfural is recovered, and the organic layer containing the furfural is further purified by distillation separation to obtain a product furfural.

  On the other hand, the separated aqueous layer is circulated to the reaction system. This is because the water layer contains water and a catalyst as a reaction solvent, and these are circulated to reuse them in the reaction system. There have been no studies on the temperature conditions and component contents when circulating and using.

International Publication 2012/115706 Pamphlet

  In the production of furfural from non-edible biomass resources, in the conventional method in which an aqueous layer containing a catalyst obtained by two-layer separation of crude furfural is circulated to the reaction system, the target furfural can be obtained by circulating the aqueous layer. There is a problem that loss occurs and the yield of furfural decreases.

  The present invention has been made in view of the above problems, and in producing furfural from non-edible biomass resources, the residual liquid after separation and removal of furfural from the dehydration reaction liquid containing furfural is recycled to the reaction system. An object of the present invention is to provide an industrially and economically advantageous continuous production method of furfural which can prevent the loss of furfural during the production and can produce the furfural stably and efficiently.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by controlling the organic acid concentration and the furfural concentration of the circulating liquid and the circulating liquid temperature, thereby completing the present invention. It came to.
That is, the gist of the present invention resides in the following [1] to [7].

[1] A sugar solution containing a non-edible biomass resource as a raw material and reacting in a solvent in the presence of a catalyst and containing a monosaccharide having 5 carbon atoms and / or a monosaccharide having 5 carbon atoms as a constituent component To obtain a reaction liquid containing furfural by converting a monosaccharide having 5 carbon atoms and / or a polysaccharide having a monosaccharide having 5 carbon atoms as a constituent component into furfural by a dehydration reaction. A method for producing furfural in which at least a part of a residual liquid after separation and removal of furfural is recycled as the solvent, wherein at least a part of the residual liquid to be circulated (hereinafter referred to as “circulating liquid”). A method for producing furfural, which is an aqueous solution of 40 ° C. or more and 200 ° C. or less containing 0.1 to 50% by weight of organic acid and 0.01 to 2% by weight of furfural.
[2] The method for producing furfural according to [1], wherein the formic acid concentration in the circulating liquid is 10 ppm by weight or more and 8000 ppm by weight or less.
[3] The method for producing furfural according to [1] or [2], wherein the concentration of acetic acid in the circulating fluid is 100 ppm to 2% by weight.
[4] The method for producing furfural according to any one of [1] to [3], wherein the solvent contains an organic solvent having 3 to 12 carbon atoms.
[5] The method for producing furfural according to any one of [1] to [4], wherein the solvent contains a hydrophobic hydrocarbon solvent.
[6] The method for producing furfural according to any one of [1] to [5], wherein the non-edible biomass resource is bagasse.
[7] The method for producing furfural according to any one of [1] to [6], wherein the temperature of the circulating liquid is 80 ° C. or higher and 180 ° C. or lower.

  According to the present invention, when producing furfural from non-edible biomass resources, the organic acid concentration, the furfural concentration and the temperature of the circulating liquid, that is, the remaining liquid after separating and removing the furfural from the dehydration reaction solution, are within a predetermined range. By controlling in this manner, the furfural loss can be reduced and the furfural can be produced stably and efficiently, and an industrially and economically advantageous continuous production method of furfural is provided.

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

  In the method for producing furfural of the present invention, a non-edible biomass resource is used as a raw material, a reaction is performed in a solvent in the presence of a catalyst, and a monosaccharide having 5 carbon atoms and / or a monosaccharide having 5 carbon atoms is used as a constituent component. Obtaining a sugar solution containing the polysaccharides (hereinafter, these may be referred to as “C5 saccharides”), converting the C5 saccharides in the sugar solution to furfural by dehydration reaction, obtaining a reaction solution containing furfural, A method for producing furfural in which at least a part of a residual liquid after separation and removal of furfural from a reaction liquid is recycled as the solvent, wherein at least a part of the residual liquid to be circulated (hereinafter referred to as “circulating liquid”). )) Is an aqueous solution having an organic acid content of 0.1 wt% or more and 50 wt% or less and a furfural content of 0.01 wt% or more and 2 wt% or less and having a temperature of 40 ° C. or more and 200 ° C. or less. To do.

  In addition, the method for producing furfural from non-edible biomass resources includes a sugar solution production process for obtaining a sugar solution containing C5 saccharide from non-edible biomass resources, and a furfural for obtaining furfural by dehydration reaction of C5 saccharide in the sugar solution. Although there are manufacturing processes, in the present invention, the sugar liquid manufacturing process and the furfural manufacturing process may be performed in one reactor, or may be performed in separate reactors.

<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 constituent component. Specifically, bagasse, switchgrass, napiergrass, Eliansus, Miscanthus, kenaf, Corn stover, corn cob, beet pulp, palm empty fruit bunch, rice straw, straw, rice bran, tree, wood, vegetable oil residue, sasa, bamboo, pulp, waste paper, food waste, seafood residue, livestock waste, etc. . Also, the molasses remaining after the sugar is recovered from the molasses generated in the sugar production process can be used as a non-edible biomass raw material. Among these, bagasse, corn stover, corn cob, and rice straw are preferable from the viewpoint of raw material availability and cost, bagasse and corn cob are more preferable, and bagasse is particularly preferable. Non-edible biomass resources, unlike edible biomass resources, do not compete with edible uses, and are usually discarded or incinerated, so stable supply and effective use of resources are possible. 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. Moreover, these non-edible biomass resources may be used individually by 1 type, and may be used in combination of 2 or more type. 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 grain from the viewpoints of handleability and reaction efficiency. Moreover, 50 mm or less is preferable, 25 mm or less is more preferable, and 10 mm or less is especially preferable.

<C5 sugar>
The C5 saccharide used in the present invention is not particularly limited as long as it is derived from non-edible biomass resources and can produce furfural by dehydration reaction.

  Specific examples of the monosaccharide having 5 carbon atoms (pentose) include ribose, lyxose, xylose, arabinose, deoxyribose, xylulose, ribulose and the like. Among these monosaccharides, they are abundant because they are constituents of nature and plants, and xylose and arabinose are preferred, and xylose is more preferred from the viewpoint of availability of raw materials and yield.

  Specific examples of polysaccharides having the above monosaccharides having 5 carbon atoms include disaccharides such as xylobiose and arabinobiose; trisaccharides such as xylotriose and arabinotriose, the above disaccharides and 3 Examples include oligosaccharides such as xylo-oligosaccharides and arabino-oligosaccharides containing saccharides, and polysaccharides such as xylan, araban, and hemicellulose. Among these polysaccharides, xylo-oligosaccharide, xylan, and hemicellulose are preferable from the viewpoint of yield, and xylo-oligosaccharide is particularly preferable. Here, the xylo-oligosaccharide is mainly composed of disaccharides and trisaccharides and further contains 4 to 6 sugars.

In the sugar liquid obtained from non-edible biomass resources, only one kind of these monosaccharides and polysaccharides may be contained, or two or more kinds may be contained.
In the sugar solution, monosaccharides such as glucose and polysaccharides such as glucan having different carbon numbers from C5 saccharides may coexist.

<Production reaction of sugar solution>
The reaction for producing the sugar solution containing the C5 saccharide from the non-edible biomass resource is a reaction for generating a C5 saccharide by hydrolyzing the hemicellulose content 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 C5 saccharide and improving the purity of the obtained C5 saccharide.

  Hereinafter, the production reaction of the sugar solution will be described.

(Non-edible biomass concentration)
In the production reaction of the sugar solution from the non-edible biomass resource, the concentration of the non-edible biomass contained in the solution is not particularly limited, but the ratio of the non-edible biomass to the solvent is 0.1 to 200% by weight. Is preferable, more preferably 5 to 40% by weight, still more preferably 10 to 30% by weight. Here, the “solution” refers to a reaction solution containing a reaction solvent, a non-edible biomass raw material, and a catalyst described later. If the ratio of non-edible biomass to the solvent is equal to or higher than the above lower limit value, the energy required for solvent separation tends to be low, and further, the capacity of the reaction system can be reduced to reduce the construction cost of the equipment. There is a tendency. When the ratio of non-edible biomass to the solvent is not more than the above upper limit value, side reactions can be suppressed, and the yield of C5 saccharides and further furfural tends to increase, which is preferable.

(catalyst)
The catalyst used in the production reaction of sugar liquid from non-edible biomass resources is not particularly limited as long as it is a catalyst capable of producing C5 saccharides from non-edible biomass, but inorganic such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, etc. Examples thereof include acid catalysts such as acids, carboxylic acids, organic acids such as sulfonic acids, and heteropoly acids. Among these, organic acids are preferable from the viewpoints of stability, corrosivity, waste treatment, and unit price, and carboxylic acids are particularly preferable.

Specific examples of the carboxylic acid 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, trans-1,4-cyclohexanedicarboxylic acid; 1,2,4-cyclohexanetricarboxylic acid, 1,3,4 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, hemimellitic acid, melophanoic acid, prenitic acid And aromatic polycarboxylic acids such as pyromellitic acid, benzenepentacarboxylic acid, and mellitic acid; and heterocyclic carboxylic acids such as furancarboxylic acid and furandicarboxylic acid. Moreover, the salt which neutralized at least one part of these acids can also be used.
Among these, formic acid, acetic acid, lactic acid, and levulinic acid, which are acids obtained from non-edible biomass, are preferable.

  Particularly from the viewpoint of the yield of C5 saccharide, among the above carboxylic acids, those having an acid dissociation constant pKa of 3 to 5 and particularly 3.0 to 4.6 are preferred. Here, the acid dissociation constant pKa is a value when the dissociation stage is 1. That is, in the case of a carboxylic acid having two or more carboxyl groups, it means the acid dissociation constant pKa when at least one hydrogen ion of 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 with a dissociation stage of 1 and 5.48 with a dissociation stage of 2. In this specification, 4.19 with a dissociation stage of 1 is used. It is set as pKa of succinic acid.

  Said carboxylic acid may be used individually by 1 type, and may use 2 or more types together.

Specific examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid, and the like. Moreover, the salt which neutralized at least one part of these acids can also be used.
Said sulfonic acid may be used individually by 1 type, and may use 2 or more types together.

Specific examples of the heteropolyacid include phosphotungstic acid, silicotungstic acid, phosphomolybdic acid, silicomolybdic acid, phosphovanadmolybdic acid, and caivanadomolybdic acid. Moreover, the salt which neutralized at least one part of these acids can also be used.
Said heteropolyacid may be used individually by 1 type, and may use 2 or more types together.

  Moreover, you may use the said carboxylic acid, sulfonic acid, and heteropoly acid, mixing 2 or more types in arbitrary ratios. The catalyst is preferably separated and recycled for use in the process.

  The amount of catalyst used in the sugar liquid production reaction can be appropriately set based on the type of catalyst and reaction conditions, and is not particularly limited, but is preferably 0.01 to 50% by weight with respect to 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 non-edible biomass raw material, and a catalyst described later. When the amount of catalyst is not less than the above lower limit, the reaction rate tends to increase and the productivity of C5 saccharide tends to improve. It is preferable that the amount of catalyst is not more than the above upper limit value because side reactions are suppressed and the selectivity of C5 saccharide tends to be improved.

(Reaction solvent)
The reaction solvent used in the reaction for producing the sugar liquid from the non-edible biomass resource is water or a mixed solvent of water and an organic solvent. That is, the reaction can be performed only with 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 that is a two-phase system of an aqueous phase and an organic phase can also be used.

  The organic solvent is not particularly limited, and examples thereof include 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-C12 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, others, sulfolane, isosorbide, isosorbide Examples include dodimethyl ether and propylene carbonate.

Of these organic solvents, a hydrophobic hydrocarbon solvent is preferable from the viewpoint of separating the furfural present in a small amount in the reaction system from the acid catalyst to prevent successive reactions.
On the other hand, an oxygen-containing solvent having 3 to 12 carbon atoms is preferable from the viewpoint of improving the extraction rate of saccharides.

As the hydrophobic hydrocarbon solvent, toluene, xylene, diethylbenzene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene (tetralin), 1-methylnaphthalene, cyclohexane, isododecane are preferable, and particularly toluene, xylene, diethylbenzene, Aromatic hydrocarbon solvents such as trimethylbenzene, 1,2,3,4-tetrahydronaphthalene (tetralin) and 1-methylnaphthalene are particularly preferred.
Examples of the oxygen-containing solvent having 3 to 12 carbon atoms include ethers such as tetrahydrofuran, alcohols, lactones, glycols, glycol ethers, sulfolane, isosorbide, isosorbide dimethyl ether, and propylene carbonate.

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

  In the present invention, the organic solvent is preferably used in an amount of 0.1% by weight to 100% by weight with respect to water. When the amount of the organic solvent used is not less than the above lower limit, the effect of the present invention by using the organic solvent can be effectively obtained, and the loss of furfural can be suppressed and it can be produced industrially advantageously. . When the amount of the organic solvent used is not more than the above upper limit, the cost of the organic solvent is reduced, and the amount of the solvent entrained with the solid content during the solid-liquid separation of the non-edible biomass residue is reduced, which is economically advantageous. A sugar solution can be produced. The amount of the organic solvent used is preferably 0.2% by weight to 50% by weight and more preferably 0.3% by weight to 5% by weight with respect to water.

(Reaction conditions)
Although the reaction temperature of the sugar liquid production reaction is not particularly limited, specifically, it is preferably 100 ° C or higher, more preferably 120 ° C or higher, further preferably 160 ° C or higher, and 250 ° C or lower. Preferably, it is 230 degrees C or less. When the reaction temperature is equal to or higher than the above lower limit, the progress of the reaction tends to be accelerated, and the productivity of C5 saccharide production is improved. It is preferable for the reaction temperature to be equal to or lower than the above upper limit value because there is a tendency to suppress the sequential reaction and decomposition of C5 saccharide and improve the yield of C5 saccharide.

  The heating method is not particularly limited, but there are a method of raising the temperature of the reaction liquid with a heat exchanger, a method of directly introducing steam into the reaction liquid, a method of heating using heat recovered from the liquid in a high temperature process, etc. A method of heating using heat recovered from a liquid in a high temperature process is particularly preferable from the viewpoint of efficiently using thermal energy. The heating method may be a single method or a combination of a plurality of methods.

  The reaction time of the sugar liquid production reaction varies depending on the amount and type of raw materials and catalyst used, and the reaction temperature, but is specifically preferably 0.02 hours or more, more preferably 0.1 hours or more, and particularly preferably 0.8. It is 2 hours or more, preferably 5 hours or less, more preferably 2 hours or less, and particularly preferably 1 hour or less. When the reaction time is not less than the above lower limit, the progress of the reaction is promoted and the yield of C5 saccharide tends to be improved, and when the reaction time is not more than the above upper limit, decomposition of C5 saccharide or sequential reaction It is preferable because it tends to suppress C5 and improve the yield of C5 saccharide.

  The preferable 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 mode of the sugar liquid production reaction is not particularly limited, and may be a batch type, a semi-batch type, a continuous type, or a combination of these. From the viewpoint of improving productivity, semi-batch reaction and continuous reaction are preferable, and from the viewpoint of easy operation, batch reaction is preferable. Moreover, a rotary reactor is preferable from the viewpoint of solid-liquid contact. One reactor may be used, or a plurality of reactors may be combined.

(Solid-liquid separation)
The solid-liquid separation method for separating the reaction residue of non-edible biomass resources from the reaction liquid after the production reaction of the sugar liquid is not particularly limited, but filter press, belt filter, screw press, roll press, conveyor dryer, oliver filter, precoat Filters, disk filters, belt presses, Gina centrifugal separators, rotary pressure dehydrators, multiple disk dehydrators, hollow fiber membrane filtration devices, cross-flow centrifugal filtration dehydrators, etc. can be preferably used. Filter presses, belt filters A roll press is more preferable, and a roll press is particularly preferable. Solid-liquid separation may be performed after the production of the sugar liquid, may be performed after the production of furfural by dehydration reaction, or may be performed during the production of the sugar liquid or furfural.

<Furfural production reaction>
The furfural production reaction carried out in the present invention is a reaction for producing a furfural by dehydrating the C5 saccharide in the sugar solution obtained by the sugar solution production reaction in the presence of a catalyst. This dehydration reaction is preferably performed 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 in sugar solution)
The concentration of C5 saccharide in the sugar solution produced from the non-edible biomass resource as described above and used for the dehydration reaction for furfural production is not particularly limited, but the ratio of C5 saccharide to the reaction solution is 0.1. It is preferable that it is -50 weight%, More preferably, it is 1-30 weight%, More preferably, it is 4-10 weight%. When the content of the C5 saccharide in the sugar solution is not less than the above lower limit value, the energy required for separation of furfural and the solvent tends to be low after the dehydration reaction, and the capacity of the reaction system is further reduced. Construction costs tend to be reduced. When the C5 saccharide concentration is not more than the above 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 above-mentioned sugar liquid production reaction from non-edible biomass resources. The preferred catalyst is the same as in the above-mentioned reaction for producing a sugar solution from non-edible biomass resources.

  The amount of catalyst used in the furfural production reaction can be appropriately set based on the type of catalyst and reaction conditions, and is not particularly limited, but is preferably 0.01 to 50% by weight with respect to the solution amount. More preferably, it is 0.1-30 weight%, Most preferably, it is 0.2-10 weight%. Here, the “solution” refers to a reaction solution containing a reaction solvent, a C5 saccharide, and a catalyst described later. When the amount of catalyst is not less than the lower limit, the reaction rate tends to increase and the furfural productivity tends to improve. Further, since furfural has a property of polymerizing under acidic conditions, it is preferable that the amount of catalyst is not more than the above-mentioned upper limit because 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 sugar liquid production reaction from non-edible biomass resources, it is possible to perform the reaction only with water, but it is also possible to perform the reaction 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.

  Although the reaction can be carried out with a homogeneous mixed solvent by adding an organic solvent, it suppresses the polymerization and decomposition reaction of furfural and improves the yield of furfural. It is preferable to use it.

  The organic solvent to be used and the amount of the organic solvent to be used are not particularly limited, but any of the organic solvents used in the sugar liquid production reaction from non-edible biomass resources can be used. Hydrophobic hydrocarbon solvents are preferred from the viewpoint of separating furfural from the acid catalyst and preventing sequential reaction. On the other hand, an oxygen-containing solvent having 3 to 12 carbon atoms is also preferable from the viewpoint of improving the selectivity by reducing the saccharide and furfural concentration in the reaction field.

  Also in the production reaction of furfural, the organic solvent is preferably a single solvent in consideration of solvent recovery and reuse, but two or more kinds may be used.

  A suitable amount of the organic solvent used is 0.1% by weight or more and 500% by weight or less based on water. When the amount of the organic solvent used is not less than the above lower limit, the effect of the present invention by using the organic solvent can be effectively obtained, and the loss of furfural can be suppressed and it can be produced industrially advantageously. . When the amount of the organic solvent used is not more than the above upper limit, the cost of the organic solvent is reduced, and the furfural can be produced economically advantageously without increasing the size of the reactor. The amount of the organic solvent used is preferably 5% by weight to 300% by weight and more preferably 30% by weight to 200% by weight with respect to water.

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

  The reaction time of the furfural production reaction varies depending on the sugar solution composition, the amount and type of catalyst used, and the reaction temperature. Specifically, it is preferably 0.02 hours or more, more preferably 0.1 hours or more, and particularly preferably 0. .5 hours or more, preferably 5 hours or less, more preferably 2 hours or less. When the reaction time is not less than the above lower limit, the progress of the reaction is promoted, and the conversion tends to improve the furfural yield. When the reaction time is not more than the above upper limit, the furfural is reduced. It is preferable because it tends to suppress decomposition and polymerization and improve the yield of furfural.

  The preferable 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 form of the furfural production reaction is not particularly limited, and may be a batch type, a semi-batch type, a continuous type, or a combination of these. A semi-batch reaction and a continuous reaction are preferable from the viewpoint of productivity improvement, and a batch reaction is preferable from the viewpoint of ease of operation, but a continuous system is preferable from the viewpoint of reducing the reactor cost. In the continuous reaction, a continuous tube reactor or a continuous tank reactor can be used. Moreover, the reactive distillation system which distills while producing the furfural which is a reaction product may be used. For example, as described in International Publication No. 2013/102027, a method for continuously extracting a mixture of furfural and water using a furfural production reactor as a reactive distillation format, or as described in International Publication No. 2012/115706. Alternatively, a method of continuously extracting furfural from the aqueous phase using an organic solvent can be used. In the case of the reactive distillation method, it may be carried out at reduced pressure or at normal pressure. One reactor may be used, or a plurality of reactors may be combined.

(Furfural collection)
In the present invention, furfural is separated and recovered from the reaction liquid (crude furfural) containing furfural obtained by dehydration reaction of C5 saccharide in the sugar liquid as described above. Specifically, the crude furfural is separated into two layers, an organic layer containing furfural and an aqueous layer, and the obtained aqueous layer is circulated into the reaction system as a circulating liquid, while the organic layer containing furfural is separated by distillation. Etc. to obtain the furfural of the product.

<Circulating fluid>
In the present invention, at least a part of the residual liquid after the furfural is separated and removed from the crude furfural by the above two-layer separation or the like is circulated to the reaction system.
The component content, temperature, etc. of the circulating fluid according to the present invention (hereinafter sometimes referred to as “the circulating fluid of the present invention”) will be described below.

(Organic acid concentration)
The organic acid concentration in the circulating fluid of the present invention is 0.1% by weight or more and 50% by weight or less. Here, the organic acid is an organic acid contained in a reaction solution as a catalyst or an organic acid by-produced when producing furfural from a non-edible biomass resource via C5 saccharide. When the organic acid concentration is equal to or higher than the lower limit, the furfural yield is improved. When the organic acid concentration is equal to or lower than the upper limit, the furfural loss can be reduced and the furfural yield can be maintained high. To keep the concentration of organic acid in the circulating fluid within the above range, control the amount of organic acid extracted from non-edible biomass resources, extract and remove organic acid in sugar solution, add alkali to add organic acid It is possible to adopt a method such as neutralizing water or adding an organic acid to the circulating liquid.
The organic acid concentration in the circulating fluid of the present invention is preferably 0.2% by weight to 40% by weight, more preferably 1% by weight to 30% by weight.

  Among the organic acids in the circulating fluid of the present invention, the formic acid concentration is preferably 10 ppm by weight or more and 8000 ppm by weight or less. Formic acid is contained in the reaction solution as a catalyst, and is by-produced in the process of producing furfural from non-edible biomass resources via C5 sugars. Formic acid is particularly corrosive among carboxylic acids and corrodes equipment. Therefore, the formic acid concentration in the circulating liquid is preferably 8000 ppm by weight or less. Therefore, when formic acid is used as the catalyst, it is preferably used in such an amount that the total concentration with formic acid produced by the reaction is not more than the above upper limit value. It is difficult to suppress the amount of formic acid produced so that the formic acid concentration in the circulating fluid is less than 10 ppm by weight, and the formic acid concentration in the circulating fluid is usually 10 ppm by weight or more. The formic acid concentration in the circulating fluid is preferably 20 ppm by weight to 5000 ppm by weight, particularly preferably 100 ppm by weight to 4000 ppm by weight.

  Moreover, it is preferable that the acetic acid density | concentration is 100 weight ppm or more and 2 weight% or less among the organic acids in the circulating liquid of this invention. Acetic acid is contained in the reaction solution as a catalyst, and is by-produced in the process of producing furfural from non-edible biomass resources via C5 sugars, but the acetic acid concentration is higher than the above lower limit, improving the furfural yield. To do. On the other hand, when the acetic acid concentration is less than or equal to the above upper limit, the amount of furfural loss can be reduced and the furfural yield can be maintained high. Therefore, the amount of organic acid extracted from non-edible biomass resources is controlled so that the concentration of acetic acid in the circulating fluid is within the above range, the organic acid in the sugar solution is extracted and removed, and the organic acid is added with alkali. It is preferable to add an organic acid to the circulating liquid. The concentration of acetic acid in the circulating liquid is particularly preferably 0.1% by weight or more and 1.5% by weight or less, and particularly preferably 0.5% by weight or more and 1% by weight or less.

(Furfural concentration)
The furfural concentration in the circulating fluid of the present invention is 0.01% by weight or more and 2% by weight or less. When the furfural concentration is above the lower limit, the purification cost of the circulating fluid can be reduced, and when the furfural concentration is lower than the upper limit, the amount of furfural contained in the circulating fluid is lost and the furfural yield is increased. Can do. In order to keep the furfural concentration in the circulating fluid within the above range, it is possible to use a method that uses a solvent having a high furfural extraction efficiency, increases the amount of solvent, or uses multistage extraction in the aforementioned two-layer separation. it can. The furfural concentration in the circulating fluid of the present invention is preferably 0.02 wt% or more and 1 wt% or less, more preferably 0.05 wt% or more and 0.7 wt% or less.

(temperature)
The temperature of the circulating fluid of the present invention is preferably 40 ° C. or higher and 200 ° C. or lower. The temperature of the circulating liquid is related to the temperature in the above-described two-layer separation, and when the circulating liquid is 40 ° C. or higher, when the circulating liquid is circulated through the reaction system, the temperature of the reaction system is excessively increased. The amount of heating energy required for the reaction system can be suppressed without being reduced. On the other hand, if the temperature of the circulating liquid is 200 ° C. or lower, there is no need to separate the two layers at a high temperature during the two-layer separation, and the contamination amount in the system is reduced by reducing the amount of organic pollutants mixed in the water layer. In addition, the corrosion in the system can be suppressed, and the extraction efficiency of furfural into an organic solvent can be increased, so that efficient two-layer separation can be performed. The temperature of the circulating liquid is preferably 80 ° C. or higher and 180 ° C. or lower, more preferably 100 ° C. or higher and 160 ° C. or lower.

  The C5 saccharide concentration of the circulating fluid of the present invention is 0.001% to 2% by weight, particularly 0.005% to 1% by weight, particularly 0.01% to 0.5% by weight. Preferably there is.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded.

In the following Examples, moisture analysis was performed using the Karl Fischer method (measured by CA-21 manufactured by Mitsubishi Chemical). Analysis of the furfural of the crude furfural, the furfural of the circulating liquid, and the organic acid (excluding formic acid) was performed by gas chromatography (GC) and calculated by an internal standard method (using dioxane as an internal standard substance).
C5 saccharides in the circulating fluid and sugar solution were analyzed by liquid chromatography (LC) under the following conditions.
Device name: Waters Alliance 2690 Tosoh CO-8010
Analytical 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 a water-based chromatodisc (0.45 μm), and the filtrate was used for measurement.

  The formic acid concentration in the circulating liquid was measured by diluting 50 times with an aqueous isopropanol solution by capillary electrophoresis (API-3300 manufactured by Otsuka Electronics Co., Ltd.).

  The organic acid in the circulating liquid is mainly composed of formic acid, acetic acid, and lactic acid used as a catalyst.

[Example 1]
<Manufacture of crude furfural>
After putting 8.8 g of bagasse (weight average diameter 3 mm) into a 100 mL micro autoclave, adding an aqueous solution containing 25% by weight of lactic acid and sealing the container, the inner space was replaced with nitrogen, and the pressure was maintained at 0.3 MPaG with nitrogen. did. The autoclave was heated to 190 ° C., and the reaction was performed by heating and stirring at 1.4 MPaG for 30 minutes.

  After completion of the reaction, the reaction solution was allowed to cool to room temperature while maintaining stirring, and the entire reaction solution in the autoclave was recovered, and then the bagasse residue was separated from the reaction solution by solid-liquid separation.

<Manufacture of circulating fluid>
63 g of the above crude furfural was placed in a 250 mL extraction tank, 42 g of tetralin was mixed, stirred at 80 ° C. for 60 minutes, allowed to stand for 30 minutes, and then separated into two layers.

<Circulating circulating fluid>
After putting 8.8 g of bagasse (weight average diameter 3 mm) in a 100 mL micro autoclave and sealing the container, the internal space was replaced with nitrogen, and the pressure was maintained at 0.3 MPaG with nitrogen. The aqueous layer obtained by the above two-layer separation was put as a circulating liquid in a 100 mL autoclave different from the above, the internal space was replaced with nitrogen, and the pressure was maintained at 0.19 MPaG with nitrogen. The autoclave containing the circulating liquid was heated to 130 ° C., the pressure was set to 0.9 MPaG, and 60 g of the circulating liquid was pumped to the autoclave containing bagasse. The autoclave was heated to 190 ° C., and the reaction was performed by heating and stirring at 1.4 MPaG for 30 minutes.
The results are shown in Table 1.

[Comparative Example 1]
In Example 1, it implemented similarly except having set the temperature of the circulating liquid to 25 degreeC, and the result was shown in Table 1.

  From Table 1, it can be seen that furfural can be stably obtained in a high yield by controlling the concentration of furfural and organic acid in the circulating fluid and the temperature of the circulating fluid within a predetermined range.

Claims (7)

Using a non-edible biomass resource as a raw material, a reaction is performed in a solvent in the presence of a catalyst to obtain a sugar solution containing a polysaccharide having a monosaccharide having 5 carbon atoms and / or a monosaccharide having 5 carbon atoms as a constituent component,
A reaction liquid containing furfural is obtained by converting a monosaccharide having 5 carbon atoms and / or a polysaccharide having a monosaccharide having 5 carbon atoms into a furfural by dehydration reaction in the sugar liquid,
A method for producing furfural, wherein at least a part of the residual liquid after separating and removing furfural from the reaction liquid is recycled as the solvent,
At least a part of the residual liquid to be circulated (hereinafter referred to as “circulating liquid”) contains 0.1% by weight to 50% by weight of organic acid and 0.01% by weight to 2% by weight of furfural. The manufacturing method of a furfural which is 40 to 200 degreeC aqueous solution containing% or less.   The manufacturing method of the furfural of Claim 1 whose formic acid density | concentration in the said circulating liquid is 10 weight ppm or more and 8000 weight ppm or less.   The method for producing furfural according to claim 1 or 2, wherein the concentration of acetic acid in the circulating fluid is 100 ppm to 2% by weight.   The manufacturing method of the furfural of any one of Claims 1-3 in which the said solvent contains a C3-C12 organic solvent.   The method for producing furfural according to any one of claims 1 to 4, wherein the solvent contains a hydrophobic hydrocarbon solvent.   The method for producing furfural according to any one of claims 1 to 5, wherein the non-edible biomass resource is bagasse.   The manufacturing method of the furfural of any one of Claims 1-6 whose temperature of the said circulating liquid is 80 to 180 degreeC.