JP6380018B2 - Method for producing furfural - Google Patents

Description

  The present invention relates to a method for producing furfural from sugar.

  Furfural using biomass resources as raw materials can be used as a raw material for producing furfuryl alcohol obtained by hydrogenation, furan obtained through decarbonylation reaction, and tetrahydrofuran, respectively, and furan resin and PTMG (polytetramethylene ether glycol). It is a useful compound that can be converted into a plant-derived polymer raw material.

  As a method for producing furfural, there has been known for a long time a method in which a raw material containing a saccharide such as pentose is reacted in the presence of an acid catalyst and obtained by dehydration. As an acid catalyst, a method using sulfuric acid (Patent Document 1), a method using an ion exchange resin (Patent Document 2), a method using a solid oxide (Non-Patent Document 1), an organic acid such as acetic acid is used. A method (Patent Document 3) is known.

International publication 2013/101999 pamphlet JP2013-253069A Japanese Patent Laid-Open No. 54-039071

Applied Catalysis B: Environmental 145 (2014) p.34

In the production method using sulfuric acid as the acid catalyst described in Patent Document 1, there is a problem that the acid catalyst after use becomes a large amount of acidic waste, and a great cost for disposal is required. Moreover, in the manufacturing method using the ion exchange resin and solid oxide described in Patent Literature 2 and Non-Patent Literature 1, there is a problem that the catalytic activity is reduced due to adhesion of insoluble substances such as humin and char generated during the reaction. was there. Furthermore, the ion exchange resin has a problem that the thermal stability is poor and the reaction temperature cannot be increased.
On the other hand, the organic acid described in Patent Document 3 is a catalyst that does not adhere insoluble substances and has a low catalyst treatment cost, but has a drawback that the yield of the target product is low.

  Therefore, an object of the present invention is to provide a method for efficiently producing a target product at a low catalyst processing cost when producing furfural from sugar in the presence of a catalyst.

As a result of intensive studies to solve the above-mentioned problems, the present inventors used a compound having two or more carboxyl groups in a liquid or solid state at 1 atm and 200 ° C. as a catalyst. As a result of the reaction, it was found that the treatment cost of the catalyst was reduced, and that furfural could be efficiently produced, and the present invention was completed.
That is, the gist of the present invention is as follows.

[1] A method for producing furfural having a process for producing furfural from sugar in the presence of a catalyst (hereinafter referred to as “FRL production process”), wherein the catalyst is in a liquid or solid state at 1 atm and 200 ° C., A method for producing furfural, which is a compound having two or more carboxyl groups.
[2] The method for producing furfural according to [1], wherein the catalyst is a compound having a pKa of 3.0 or more and 4.6 or less.
[3] The method for producing furfural according to [1] or [2], wherein the catalyst is fumaric acid, succinic acid, or terephthalic acid.
[4] The method for producing furfural according to any one of [1] to [3], wherein the catalyst is present in an amount of 0.02 to 50 wt% based on sugar.
[5] The method for producing furfural according to any one of [1] to [4], wherein the sugar is a polysaccharide having a monosaccharide having 5 carbon atoms or a monosaccharide having 5 carbon atoms as a constituent component.
[6] The method for producing furfural according to any one of [1] to [5], wherein the reaction temperature in the FRL production step is 100 ° C. to 250 ° C. [7] The reaction solvent in the FRL production step contains water, The manufacturing method of the furfural in any one of [1]-[6] whose density | concentration of the saccharide | sugar with respect to water is 0.1-50 wt%.
[8] The method for producing furfural according to any one of [1] to [7], wherein a reaction solvent in the FRL production step includes water and an organic solvent, and a ratio of the organic solvent to water is 10 to 5000 wt%.
[9] The method for producing furfural according to [8], wherein the organic solvent is selected from at least one of the group consisting of ether, ketone, ester, alcohol, aromatic hydrocarbon, and saturated aliphatic hydrocarbon.

  According to the method for producing furfural of the present invention, the processing cost of the catalyst used for producing furfural from sugar can be reduced. Moreover, it becomes possible to set reaction conditions for efficiently producing the target product, and a method for producing furfural with high yield is provided. In addition, by using a specific catalyst, the catalyst can be easily recycled and purified, and a process design with excellent production efficiency becomes possible.

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

The production method of the present invention includes a step of producing furfural (FRL) from sugar in the presence of a catalyst (FRL production step), wherein the catalyst is in a liquid or solid state at 1 atm and 200 ° C., and two or more It is a compound having a carboxyl group.
Hereinafter, it explains in detail according to each requirement.

(Furfural (FRL) manufacturing process)
The FRL production process performed by the production method of the present invention is a process for producing a furfural by dehydrating a sugar such as a polysaccharide or a monosaccharide in the presence of a catalyst.
The synthesis reaction of furfural from sugar is mainly dehydration reaction from pentose sugar. 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.

(sugar)
The sugar used in the present invention is not particularly limited as long as it can produce furfural, and so-called general sugars such as monosaccharides and polysaccharides can be used.
Specific examples of monosaccharides include monosaccharides having 5 carbon atoms (pentose) such as ribose, lyxose, xylose, arabinose, deoxyribose, xylulose, ribulose; allose, talose, gulose, glucose, altrose, mannose, galactose, Examples thereof include monosaccharides having 6 carbon atoms (hexose) such as idose, fucose, fucose, rhamnose, psicose, fructose, sorbose, and tagatose; monosaccharides having 7 carbon atoms (heptose) such as cedoheptulose. Among these monosaccharides, hexose and pentose are preferred because they are abundant because they are constituents of nature and plants, and the raw materials are easily available. From the viewpoint of yield, these are monosaccharides having 5 carbon atoms. Some pentoses are most preferred.

  As said hexose, glucose, fructose, mannose, and galactose are preferable, and glucose is more preferable. As pentose, xylose and arabinose are preferable, and xylose is more preferable. Glucose and xylose are preferable in terms of easy availability of raw materials because they are the main constituents of nature and plants.

  Specific examples of polysaccharides include disaccharides such as sucrose, lactose, maltose, trehanose, tulanose, and cellobiose; trisaccharides such as raffinose, melezitose, and maltotriose; oligosaccharides such as fructo-oligosaccharide, galactooligosaccharide, and manna-oligosaccharide; Examples include polysaccharides such as starch, dextrin, cellulose, hemicellulose, and glucan. Among these polysaccharides, sucrose, cellulose and hemicellulose are preferable, hemicellulose having a high pentose content is more preferable, and pentose containing pentose such as xylan and araban is particularly preferable.

The sugar used in the present invention may contain one of the above monosaccharides and polysaccharides alone, or may contain two or more kinds.
Since the synthesis reaction of furfural is mainly a dehydration reaction from a pentose sugar, the sugar used in the present invention is a polysaccharide having a monosaccharide having 5 carbon atoms and / or a monosaccharide having 5 carbon atoms as a constituent component. Is preferred.

(Biomass raw material)
The aforementioned sugars are mainly contained in biomass raw materials, and it is preferable to use sugars obtained from these biomass raw materials. The biomass raw material is not particularly limited as long as it contains a polysaccharide having the above-mentioned saccharide as a constituent component, and specifically, a plant containing cellulose or hemicellulose, a starch saccharified solution, or molasses is also used. For example, sugar solution extracted from plants such as sugarcane, sugar beet, sugar maple and the like can be mentioned.

The biomass raw materials can be classified into “edible biomass raw materials” and “non-edible biomass raw materials” from the viewpoint of whether or not they can be edible.
Examples of edible biomass materials include sugarcane, starch, sugar beet, corn, potato, cassava, and sugar maple.
Specific examples of non-edible biomass materials include bagasse, switchgrass, napiergrass, Eliansus, corn stover, rice straw, straw, rice bran, trees, wood, vegetable oil residue, sasa, bamboo, pulp, waste paper, Examples include food waste, marine product residues, and livestock waste. 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.
Of these, non-edible biomass raw materials, unlike edible biomass raw materials, do not compete with edible uses and are usually discarded or incinerated, so stable supply and effective use of resources Is preferable in that it can be achieved. These biomass raw materials can be used as they are, or can be used after pretreatment such as acid treatment or hydrothermal treatment.

(Sugar concentration)
In the furfural production process, the concentration of sugar contained in the reaction solvent is not particularly limited, but the reaction solvent preferably contains water, and the sugar concentration relative to water is 0.1 wt% to 50 w.
It is preferable that it is t%, More preferably, it is 1 wt%-30 wt%, More preferably, it is 5 wt%-25 wt%. When the sugar concentration is at least the lower limit value, the separation efficiency between furfural and the solvent tends to be high, and when the sugar concentration is at most the upper limit value, side reactions can be suppressed and the yield of furfural tends to be high.
When water and an organic solvent are included as the reaction solvent, in addition to the above range, the sugar concentration relative to water is more preferably 10 wt% or more, and particularly preferably 15 wt% or more. In the case of using an organic solvent, it is considered that the generated furfural can be suppressed from dissolving and decomposing in the organic solvent, so that the sugar concentration with respect to water can be set in a relatively high range.

  In the furfural production process, any reaction solvent may be used as long as it does not inhibit the furfural production reaction. Specifically, inorganic acid ions such as sulfate ions and nitrate ions as components contained in non-edible biomass materials; halogen elements such as chlorine and fluorine; alkali metal elements such as potassium and sodium; alkalis such as magnesium and calcium It includes compounds other than sugars derived from non-edible biomass, such as earth metal elements; silicon elements; and lignin. Here, the form in which the above-described elements are present in the reaction solvent is not particularly limited, and may be, for example, a part of the elements constituting the compound or ions.

(catalyst)
In the furfural production method of the present invention, a polycarboxylic acid that is in a liquid or solid state at 1 atm and 200 ° C. and has two or more carboxyl groups is used as a catalyst.
Since organic carboxylic acid has a higher acid dissociation constant pKa than inorganic acids such as sulfuric acid, it is necessary to increase the reaction temperature to obtain a furfural in a high yield by performing a reaction using this as a catalyst. According to the study by the present inventors, it has been clarified that an organic acid having low thermal stability is decomposed under a high temperature condition, and the furfural yield is lowered. In addition, when an organic acid that decomposes under high temperature conditions is used as a catalyst, it cannot be recovered and recycled after the reaction, leading to a decrease in productivity. In the furfural production method of the present invention, at 1 atm and 200 ° C., by using a polycarboxylic acid that is in a liquid or solid state as a catalyst, it becomes possible to produce furfural stably with high efficiency at a high reaction temperature. Since the catalyst can be easily recycled, it is possible to design a process with excellent production efficiency.

In addition, polycarboxylic acid that is in a liquid or solid state at 1 atm and 200 ° C. is usually solid at room temperature and can be purified by crystallization after being recovered from the reaction solution. Furthermore, there is no concern of corroding the reactor like formic acid or hydrochloric acid.
Here, a polycarboxylic acid that is in a liquid or solid state at 1 atm and 200 ° C. in this specification is a compound having two or more carboxyl groups that is not vaporized or decomposed at 1 atm and 200 ° C. is there. Therefore, it can be said that it is a polycarboxylic acid having a boiling point and a sublimation point of 200 ° C. or higher, or a decomposition temperature of 200 ° C. or higher, which is a temperature at which a solid or liquid becomes a gas.

Specific examples of compounds that are in a liquid or solid state at 1 atm and 200 ° C. and have two or more carboxyl groups include 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, trans-1,2-cyclopentanedicarboxylic acid, cis-1,3-cyclopentanedicarboxylic acid, trans-1,3-cyclo Pentanedicarboxylic acid, cis-1,2-cyclohexanedicarboxylic acid, trans-1,2-cyclohexanedicarboxylic acid, cis-1,3-cyclohexanedicarboxylic acid, trans-1,3-cyclohexanedicarboxylic acid, cis-1,4- Cyclohexanedicarboxylic acid, trans- Aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, aliphatic tricarboxylic acids such as 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, trimesic acid And aromatic polycarboxylic acids such as trimellitic acid, hemimellitic acid, merophanic acid, prenitic acid, pyromellitic acid, benzenepentacarboxylic acid, and mellitic acid. Moreover, the salt which neutralized at least one part of these acids can also be used.
The catalyst used in the present invention may contain the above polycarboxylic acid alone or may contain two or more kinds.

Among these, the acid dissociation constant pKa is preferably 3.0 or more and 4.6 or less from the viewpoint of furfural yield. For example, pKa3.03 fumaric acid, pKa4.19 succinic acid, pKa3.51 terephthalic acid. , PKa3.12 trimesic acid and pKa4.6 sebacic acid. From the viewpoint of obtaining raw materials, fumaric acid, succinic acid, and terephthalic acid are particularly preferable.
Here, the acid dissociation constant pKa of the polycarboxylic acid used as a catalyst in the present invention is a numerical value when the dissociation stage is 1. That is, 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 understood as pKa of succinic acid.

  The amount of the catalyst used in the furfural production process can be appropriately set based on the type of catalyst, reaction conditions, etc., and is not particularly limited, but is preferably 0.02 to 50 wt% with respect to the sugar, more Preferably it is 0.05-30 wt%, More preferably, it is 0.1-20 wt%. When the catalyst amount is at least the lower limit value, the reaction rate tends to increase and the furfural productivity tends to improve. It is preferable that the amount of the catalyst is not more than the upper limit because side reactions are suppressed and the selectivity of furfural tends to be improved.

  In the production method of the present invention, it is necessary to use a polycarboxylic acid that is in a liquid or solid state at 1 atm and 200 ° C. as the main catalyst, but other carboxylic acids may be used as long as the effects of the present invention are not impaired. May be contained in a trace amount. For example, it may contain carboxylic acids such as lactic acid, oxalic acid, formic acid, acetic acid, benzoic acid, propionic acid, butyric acid, caproic acid, maleic acid, malic acid, citric acid, tartaric acid, and in particular at 1 atm and 200 ° C. Carboxylic acids such as lactic acid, benzoic acid and caproic acid which are in a solid or liquid state are preferred. When these are included, you may include in 0.01-30 wt% with respect to the whole quantity of a catalyst.

(Reaction solvent)
The reaction solvent used in the furfural production process is preferably water or an organic solvent. Usually, the reaction can be performed only with water, but the reaction can also be performed 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, the polymerization and decomposition reaction of furfural is suppressed, and the yield of furfural is improved. It is preferable to use it. The amount of the organic solvent to be used is not particularly limited as long as the gist of the present invention is not impaired, but it is preferably 10 to 5000 wt%, particularly preferably 10 to 1000 wt% with respect to water.

The organic solvent is not particularly limited as long as it does not inhibit the furfural synthesis reaction from the sugar. For example, diethyl ether, tetrahydrofuran, tetrahydropyran, dipropyl ether, diisopropyl ether, methyl-tert-butyl ether , Ethers having 4 to 20 carbon atoms such as butyl ether, pentyl ether, hexyl ether, octyl ether, nonyl ether, decyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether; 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclohexanone, 4-methyl-2-pentanone, 2-heptanone, 5- Til-2-hexanone, 2,4-dimethylpentanone, 5-nonanone, 4-decanone, 5-decanone, 2-undecanone, 4-undecanone, 3-dodecanone, 2-tridecanone, 2-tetradecanone, 4-tetradecanone, Carbon number 4 such as 2-pentadecanone, 3-pentadecanone, 7-pentadecanone, 2-hexadecanone, 3-hexadecanone, 4-hexadecanone, 6-hexadecanone, 2-heptadecanone, 4-heptadecanone, 9-heptadecanone, 3-octadecanone, acetophenone ~ 20 ketones; esters such as ethyl acetate, propyl acetate, butyl acetate; 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol 1-pentanol, 2 -Pentanol, 3-pentanol, 3-methyl-1-butanol, 2,2-dimethyl-1-propanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 1- Heptanol, 2-heptanol, 1-octanol, 2-octanol, 3-octanol, 2-ethyl-1-hexanol, 1-nonanol, 1-decanol, 1-undecyl alcohol, 1-lauryl alcohol, 1-tridecyl alcohol 1-tetradecanol, 1-pentadecyl alcohol, 1-hexadecanol, cis-9-hexadecen-1-ol, 1-heptadecanol, 1-octadecanol, 16-methylheptadecen-1-ol , Nonadecyl alcohol, arachidyl alcohol, etc. Saturated aliphatic hydrocarbon compounds having 3 to 12 carbon atoms such as pentane, hexane, cyclohexane, heptane, octane, nonane, decane, dodecane, isododecane; toluene, xylene, trimethylbenzene, 1, 2, 3, 4 -Aromatic hydrocarbons such as tetrahydronaphthalene and 1-methylnaphthalene. The organic solvent is preferably selected from at least one of the group consisting of ethers, ketones, esters, alcohols, aromatic hydrocarbons, and saturated aliphatic hydrocarbons.
Among these, when the reaction is carried out in a two-layer system, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, 1-butanol, 2-butanol, 1-pentanol, from the viewpoint of the extraction efficiency of furfural and the amount of organic solvent dissolved in water, 1-hexanol, toluene, xylene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene, 1-methylnaphthalene, cyclohexane and isododecane are preferred. The organic solvent is preferably a single solvent in consideration of solvent recovery / reuse, but two or more types may be used.

(Reaction form)
The reaction form of the furfural production process 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, semicircular reaction and continuous reaction are preferable, and batch reaction is preferable from the viewpoint of easy operation. Moreover, the reactive distillation system which distills while producing the furfural which is a reaction product may be used. In the case of the reactive distillation method, it may be carried out at reduced pressure or at normal pressure.

(Reaction conditions)
Although the reaction temperature in the furfural production process is not particularly limited, specifically, it is 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, it is 230 degrees C or less. When the reaction temperature is equal to or higher than the lower limit, the progress of the reaction tends to be faster, and the productivity of furfural is improved. It is preferable for the reaction temperature to be equal to or lower than the upper limit value because it suppresses the decomposition and polymerization of furfural and the raw material sugar and improves the yield of furfural.
According to the production method of the present invention, since a polycarboxylic acid that is in a liquid or solid state at 1 atm and 200 ° C. is used as a catalyst, the reaction temperature can be set to a relatively high temperature of 160 ° C. or more, and the reaction proceeds efficiently. Can be made.

  The reaction time of the furfural production process varies depending on the amount of raw materials and catalyst used, the type, and the reaction temperature. Is more preferable, and more preferably 10 hours or less. When the reaction time is equal to or higher than the lower limit, the progress of the reaction is promoted, and the conversion tends to improve the furfural yield. When the reaction time is lower than the upper limit, the furfural is decomposed. It is preferable because it tends to suppress polymerization and improve the yield of furfural.

(Separation and purification process)
After completion of the reaction, the furfural obtained in the furfural production process can be separated from the reaction solution through general separation / purification operations such as concentration, extraction, distillation, and the like, and then purified to the desired purity. Further, the purity can be further improved by using a precision distillation method or a column chromatography separation and purification method.

(Catalyst recycling)
The catalyst used in the furfural production process may be recovered and recycled in the separation / purification process. Specific separation / purification methods include distillation, solvent extraction, and crystallization. These separation / purification methods can also be used in combination.

(Furfural yield)
The yield of furfural obtained by the production method of the present invention is not particularly limited and varies greatly depending on the raw materials, but is usually 15% or more, preferably 20% or more, and the upper limit is not particularly limited, usually 100% or less.
The yield was calculated by the following calculation formula.
Yield (%) = (Furfural after reaction (mol) / Stage raw material saccharide compound (mol)) ×
100

  Hereinafter, the present invention will be described more specifically with reference to examples.

The measurement conditions of the high performance liquid chromatography (henceforth, HPLC) of the reaction mixture obtained in the Example are shown below.
<High performance liquid chromatography analysis>
(Measurement conditions for sugars and organic acids)
Pump: LC-20AD manufactured by Shimadzu Corporation
Column oven: CTO-10A manufactured by Shimadzu Corporation
UV detector: Shimadzu Corporation SPD-10A
RI detector: Shimadzu Corporation RID-10A
Column: ULTRON PS-80H 300L × 8.0 mm ID (manufactured by Shinwa Kako) Eluent: 0.0108% HClO ₄ aq. .
Column temperature: 60 ° C
Flow rate: 1.0 mL / min
Injection volume: 10 μL
Detection: RI
(Furfural measurement conditions)
Apparatus: 1200 Series made by Agilent Technologies
Column: Develosil C30
4.6mm x 100mmL. 3μm (Nomura Chemical)
_{Eluent: A-0.054% HClO 4 aq} . B-acetonitrile
A / B = 95/5 → 0/100
Column temperature: 40 ° C
Flow rate: 1.0 mL / min
Injection volume: 10 μL
Detector: UV (280 nm, 210 nm)

<Example 1>
In a 70 mL micro autoclave, 0.10 g of xylan (manufactured by SIGMA-ALDRICH) as a sugar, 1.9 g of demineralized water as a reaction solvent, and 0.02 g of fumaric acid as a catalyst were sealed, and after the container was sealed, the internal space was Replaced with nitrogen. While stirring the contents, the temperature was raised to 200 ° C., and the reaction was conducted by heating and stirring at 200 ° C. for 1 hour.
After completion of the reaction, the mixture was allowed to cool to room temperature while maintaining stirring, and the entire reaction solution in the autoclave was recovered. 0.10 g of the obtained reaction solution was diluted with 1.02 g of demineralized water, filtered through a 0.45 μm filter, and subjected to HPLC analysis under the above conditions.
Based on the result of the HPLC analysis, the furfural (FRL) yield and the xylose yield were determined by the following formula. The yield of xylan was calculated as a unit of (C ₅ H ₈ O ₄ ) n.
FRL yield (%) = (FRL amount after reaction (mol) / Feed sugar (xylan) amount (mol
)) X 100
Xylose yield (%) = (Amount of xylose after reaction (mol) / Amount of charged sugar (xylan) (mol)) × 100
The FRL concentration in the reaction solution was 1.33 wt%, the xylose concentration was 0.931 wt%, the FRL yield was 36.2%, and the xylose yield was 1.62%.
The results are shown in Table 1.

<Example 2>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that terephthalic acid was used as a catalyst in Example 1.
The FRL concentration in the reaction solution was 0.909 wt%, the xylose concentration was 0.280 wt%, the FRL yield was 24.5%, and the xylose yield was 0.483%.
The results are shown in Table 1.

<Example 3>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that succinic acid was used as a catalyst in Example 1.
The FRL concentration in the reaction solution was 0.891 wt%, the xylose concentration was 0.499 wt%, the FRL yield was 24.5%, and the xylose yield was 0.878%.
The results are shown in Table 1.

<Example 4>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that trimesic acid was used as a catalyst in Example 1.
The FRL concentration in the reaction solution was 1.24 wt%, the xylose concentration was 0.835 wt%, the FRL yield was 34.0%, and the xylose yield was 1.47%.
The results are shown in Table 1.

<Example 5>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that trimet acid was used as a catalyst in Example 1.
The FRL concentration in the reaction solution was 1.31 wt%, the xylose concentration was 1.808 wt%, the FRL yield was 36.2%, and the xylose yield was 3.20%.
The results are shown in Table 1.

<Comparative Example 1>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that 0.0538 g of xylan, 0.95 g of demineralized water, and 0.02 g of acetic acid were used as a catalyst.
The FRL concentration in the reaction solution was 0.371 wt%, and the xylose concentration was 0.393 wt%. The FRL yield was 9.61% and the xylose yield was 0.635%.
The results are summarized in Table 1.

<Comparative example 2>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that oxalic acid was used as a catalyst and the reaction was performed at 160 ° C. for 4 hours.
The FRL concentration in the reaction solution was 0.797 wt%, and the xylose concentration was 1.43 wt%. The FRL yield was 22.1% and the xylose yield was 25.3%. Moreover, as a result of carrying out HPLC measurement after the reaction, the oxalic acid concentration was 0.282 wt%, which was reduced to about 25% of 1.14 wt%, which is the calculated value of the charge, so oxalic acid was decomposed during the reaction. I guess it was.
The results are summarized in Table 1.

In comparison between Examples 1 to 5 and Comparative Examples 1 and 2, when a compound having two or more carboxyl groups in a liquid or solid state at 1 atm and 200 ° C. is used as a catalyst, the temperature is as high as 200 ° C. It can be seen that furfural can be stably produced even when the reaction is carried out with a sufficiently high furfural yield. Further, since the reaction can be completed without decomposing the catalyst, it can be seen that the catalyst can be easily recovered and recycled.
In this example, when a compound having two or more carboxyl groups in a liquid or solid state at 1 atm and 200 ° C. is used as a catalyst, furfural can be stably generated in a high yield, This shows that the process has excellent production efficiency.

<Example 6>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that the reaction was performed at 160 ° C. for 4 hours in Example 1.
The FRL concentration in the reaction solution was 0.877 wt%, the xylose concentration was 1.43 wt%, the FRL yield was 24.4%, and the xylose yield was 25.5%.
The results are shown in Table 2.

<Example 7>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that the reaction was performed at 160 ° C. for 6 hours in Example 1.
The FRL concentration in the reaction solution was 1.10 wt%, the xylose concentration was 0.597 wt%, the FRL yield was 29.4%, and the xylose yield was 10.3%.
The results are shown in Table 2.

<Example 8>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that the reaction was performed at 160 ° C. for 8 hours in Example 1.
The FRL concentration in the reaction solution was 1.26 wt%, the xylose concentration was 0.430 wt%, the FRL yield was 34.5%, and the xylose yield was 7.55%.
The results are shown in Table 2.

<Example 9>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that the reaction was performed at 180 ° C. for 4 hours in Example 1.
The FRL concentration in the reaction solution was 1.21 wt%, the xylose concentration was 0.140 wt%, the FRL yield was 33.1%, and the xylose yield was 2.47%.
The results are shown in Table 2.

<Example 10>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that xylose was used as the sugar in Example 1 and the amount of fumaric acid as a catalyst was 0.004 g.
In addition, the yield of FRL at the time of using xylose as a raw material as sugar was computed with the following formula | equation.
FRL yield (%) = (FRL amount after reaction (mol) / Feed sugar (xylose) amount (mo
l)) x 100
The FRL concentration in the reaction solution was 1.32 wt%, the xylose concentration was 0.773 wt%, the FRL yield was 40.1%, and the xylose yield was 39.6%.
The results are shown in Table 2.

<Example 11>
A reaction solution was obtained and analyzed in the same manner as in Example 1 except that the amount of fumaric acid as a catalyst in Example 1 was 0.004 g.
The FRL concentration in the reaction solution was 0.692 wt%, the xylose concentration was 0.924 wt%, the FRL yield was 19.0%, and the xylose yield was 1.63%.
The results are shown in Table 2.

<Example 12>
A reaction solution was obtained in the same manner as in Example 1 except that 0.40 g of xylan was used as the sugar in Example 1, 7.6 g of demineralized water was used as the reaction solvent, and 0.08 g of fumaric acid was used as the catalyst. Analysis was carried out.
The FRL concentration in the reaction solution was 1.30 wt%, the xylose concentration was 0.229 wt%, the FRL yield was 36.0%, and the xylose yield was 4.06%.
The results are shown in Table 2.

<Example 13>
A reaction solution was obtained in the same manner as in Example 1 except that 0.80 g of xylan as a sugar, 15.2 g of demineralized water as a reaction solvent, and 0.16 g of fumaric acid as a catalyst in Example 1, Analysis was carried out.
The FRL concentration in the reaction solution was 1.33 wt%, the xylose concentration was 0.154 wt%, the FRL yield was 36.7%, and the xylose yield was 2.73%.

<Example 14>
A reaction solution was obtained and analyzed in the same manner as in Example 2 except that the amount of terephthalic acid as a catalyst in Example 1 was 0.004 g.
The FRL concentration in the reaction solution was 0.643 t%, the xylose concentration was 0.280 wt%, the FRL yield was 17.6%, and the xylose yield was 0.49%.
The results are shown in Table 2.

  According to the method for producing furfural of the present invention, the processing cost of the catalyst used for producing furfural from sugar can be reduced. Moreover, it becomes possible to set reaction conditions for efficiently producing the target product, and a method for producing furfural with high yield is provided. In addition, by using a specific catalyst, the catalyst can be easily recycled and purified, and a process design with excellent production efficiency becomes possible.

Claims (9)

  A method for producing furfural comprising a step of producing furfural from sugar in the presence of a catalyst (hereinafter referred to as “furfural manufacturing step”), wherein the catalyst is in a liquid or solid state at 1 atm and 200 ° C. A method for producing furfural, which is a compound having the above carboxyl group.   The method for producing furfural according to claim 1, wherein the catalyst is a compound having a pKa of 3.0 or more and 4.6 or less.   The method for producing furfural according to claim 1 or 2, wherein the catalyst is fumaric acid, succinic acid, or terephthalic acid.   The method for producing furfural according to any one of claims 1 to 3, wherein the catalyst is present in an amount of 0.02 to 50 wt% with respect to the sugar.   The method for producing furfural according to any one of claims 1 to 4, wherein the sugar is a monosaccharide having 5 carbon atoms or a monosaccharide having 5 carbon atoms as a constituent component.   The manufacturing method of the furfural of any one of Claims 1-5 whose reaction temperature in the said furfural manufacturing process is 100 to 250 degreeC.   The method for producing furfural according to any one of claims 1 to 6, wherein a reaction solvent in the furfural production step contains water, and a sugar concentration relative to water is 0.1 to 50 wt%.   The manufacturing method of the furfural of any one of Claims 1-7 whose reaction solvent in the said furfural manufacturing process contains water and an organic solvent, and the ratio of the organic solvent with respect to water is 10-5000 wt%.   The method for producing furfural according to claim 8, wherein the organic solvent is selected from at least one of the group consisting of ethers, ketones, esters, alcohols, aromatic hydrocarbons, and saturated aliphatic hydrocarbons.