JP6900801B2 - Method for producing carboxylic acid ester or carboxylic acid - Google Patents

Description

The present invention relates to a method for producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material, and more specifically, producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material. A method for producing a carboxylic acid ester or carboxylic acid having a high yield and excellent long-term operational stability, which is characterized by passing through a cyclic acetal intermediate, and a furan having extremely excellent thermal stability. Regarding cyclic acetals having a skeleton.

In recent years, it has become necessary to take measures against the problem of fossil fuel depletion and the problem of global environmental load such as the increase of carbon dioxide in the atmosphere. Due to such social demands, the development of a process for producing various useful chemicals from biomass raw materials vegetated in the current global environment of the atmosphere has been attracting attention and is being energetically promoted. The method of utilizing biomass raw materials as starting materials for chemical raw materials is, for example, because the production of plant raw materials can be dispersed and diversified in various places, so that the raw material supply is very stable and that it is done in the global environment of the atmosphere. Therefore, since the difference in the material balance between absorption and release of carbon dioxide is relatively balanced, it has the advantage of potentially possessing the feasibility of a recycling-oriented society including recycling, which cannot be expected from fossil resource raw materials at all. It has extremely high industrial utility value.

Until now, as a technology for seeking a raw material for chemicals from a biomass raw material, as a technology _{that greatly contributes to the reduction of CO 2} emissions, a method of using the biomass raw material itself as a raw material for a general-purpose resin or a biomass raw material for a monomer that is a raw material for the resin has been used. Various methods for inducing have been proposed. In addition, the development of a method for inducing a high-performance chemical product from a biomass raw material by utilizing the structure of the biomass raw material is also active (Non-Patent Document 1).

As reactions for inducing useful chemicals from biomass raw materials, biological conversion methods by fermentation methods for biomass raw materials, chemical conversion methods typified by catalytic reactions, conversion methods using electrochemical methods, etc. have been developed. .. However, in reality, many of the technologies for substituting chemicals derived from these biomass raw materials for chemicals derived from fossil resources or applying them to general-purpose materials have not yet been generalized or popularized. is there. The main reason for this is that, compared to raw materials derived from fossil resources, biomass raw materials and raw materials derived from them generally contain a large amount of impurities such as nitrogen-containing compounds, sulfur-containing compounds, and metal salts peculiar to biomass raw materials. In addition, since it has many reactive functional groups such as a hydroxyl group and a carbonyl group, it is likely to cause a side reaction during production. That is, in the process of applying the biomass raw material as a starting material, the process of removing these impurities and by-products is indispensable, the manufacturing process becomes complicated, the manufacturing cost rises, and the energy consumption during manufacturing also rises. It has many problems from the viewpoint of economic efficiency and environmental load.

Therefore, in the derivatization reaction from the biomass raw material targeted in the present invention, how an efficient conversion reaction process can be designed is required, and among the above conversion reactions, a chemical conversion using a catalytic reaction is particularly required. The method is attracting attention. For example, as such an efficient conversion technique, a monosaccharide or sugar alcohol conversion technique from cellulose using a catalytic reaction has been proposed in Patent Documents 1 to 3 and the like.

On the other hand, in a series of catalytic reactions for deriving useful chemicals from biomass raw materials, the process via a compound having a furan ring is particularly important from the viewpoint of its functionality, versatility of use, environmental load and economy. Proposed as a process. For example, the flange carboxylic acid and its ester, which are one of the production targets of the present invention, are generally produced by the following reaction.

As a specific production method, for example, a method for producing hydroxymethylfurfural (HMF) from monosaccharides such as glucose and fructose in the presence of hydrous niobium has been proposed in Patent Document 4. Further, Patent Documents 5 and 6 and Non-Patent Document 2 have proposed a method for producing a flange carboxylic acid or an ester thereof by an oxidation reaction of HMF.

However, in the reaction for producing a flange carboxylic acid or an ester thereof from the above-mentioned biomass resource via HMF, HMF having a reactive functional group such as an aldehyde group and a hydroxyl group serves as an intermediate, and the heat of this reactive intermediate is used. Due to the poor stability, polymerization of HMF, ring-opening reaction, etc. proceed, and not only the reaction yield decreases due to the formation of oligomers such as fumin, polymers, levulinic acid, etc., but also oligomers produced as by-products When the polymer adheres to the inside of the reactor or the pipe, there is a problem that the heat conduction efficiency of the reactor is lowered and the inside of the pipe is blocked, which makes stable long-term operation difficult. In addition, these by-products are generally colored substances, and are mixed in the product to cause coloring of the product. Furthermore, the mixing of these by-products into the product impairs the durability and stability of the product, and the product There is also a problem that it leads to the factor of foreign matter generation inside. These are particularly remarkable when the concentration of HMF is increased to produce a flange carboxylic acid or an ester thereof, which is a big problem in an industrial process in which economic efficiency at the time of production is required. In other words, in the industrial manufacturing process, how to achieve long-term stable operation of the manufacturing process under high concentration conditions is an important issue in economical process design, but this essential issue is the biomass raw material. The fact is that the manufacturing process of this chemical product has not yet been resolved. Therefore, in the manufacturing process in which the raw material is a biomass raw material, not only the design of an efficient conversion reaction process with improved reaction yield, but also the design of a reaction process that improves the thermal stability and reaction stability of the reaction intermediate. Is an issue.

International release WO2011 / 036955 Japanese Patent No. 5894387 Japanese Patent No. 5823756 Japanese Unexamined Patent Publication No. 2009-215172 Japanese Patent No. 5217142 International release WO2015 / 155784

Green Chemistry 15 (2013) 1740-1763 Journal of Catalysis 265 (2009) 109-116

The present invention has been made in view of the above problems, and in producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material, even if it is produced under high concentration conditions, the above-mentioned invention is made. A method for producing a carboxylic acid ester or carboxylic acid, which not only makes it possible to suppress side reactions to obtain the desired carboxylic acid ester or carboxylic acid in a high yield, but also has excellent long-term operational stability, and intermediates thereof. It is an object of the present invention to provide a cyclic acetal which becomes a body and has significantly improved thermal stability.

As a result of diligent studies to solve the above problems, the present inventors have made the above-mentioned by passing through a cyclic acetal intermediate when producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material. We have found that the problem can be solved and have completed the present invention.
That is, the gist of the present invention lies in the following [1] to [9].

[1] A method for producing a carboxylic acid ester or carboxylic acid, which comprises passing through a cyclic acetal intermediate in a method for producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material.

[2] The method for producing a carboxylic acid ester or carboxylic acid according to [1], which comprises producing the carboxylic acid ester or carboxylic acid having the furan skeleton by the oxidation reaction of the cyclic acetal intermediate.

[3] The method for producing a carboxylic acid ester or carboxylic acid according to [1] or [2], wherein the carboxylic acid ester or carboxylic acid having a furan skeleton is a flange carboxylic acid ester or a flange carboxylic acid. ..

[4] The method for producing a carboxylic acid ester or carboxylic acid according to any one of [1] to [3], wherein the cyclic acetal intermediate is produced using a mixed solvent of water and an organic solvent.

[5] The method for producing a carboxylic acid ester or carboxylic acid according to any one of [1] to [4], wherein the biomass raw material is a saccharide raw material.

[6] The method for producing a carboxylic acid ester or carboxylic acid according to any one of [1] to [5], which comprises a step of adding a diol to the reaction system.

[7] The method for producing a carboxylic acid ester or carboxylic acid according to [6], wherein the cyclic acetal intermediate is produced by the reaction of an aldehyde having a furan skeleton with the diol.

[8] A cyclic acetal represented by the following formula (1).

(In the formula, R ¹ is a hydrogen atom, a group represented by _{-CH 2} OH, -CH ₂ OR ² or -CH ₂ O (C = O) R ^{2 , and R 2} is an alkyl having 1 to 6 carbon atoms. Represents an aryl group having 6 to 12 carbon atoms which may have a group or an alkyl substituent.)

[9] A method for producing a carboxylic acid ester or carboxylic acid, which comprises producing a flange carboxylic acid ester or carboxylic acid from the cyclic acetal according to [8].

According to the production method of the present invention, when producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material, the thermal stability of the reaction intermediate is improved by passing through a cyclic acetal intermediate. Therefore, side reactions such as polymerization of the reaction intermediate and ring-opening reaction can be suppressed, and the yield of the target carboxylic acid ester or carboxylic acid can be improved. In addition, by suppressing side reactions, it is possible to prevent operational troubles such as deterioration of product quality due to contamination of by-products, blockage of pipes due to by-product polymers, and reduction of heat transfer efficiency, and continuous production of carboxylic acid esters or carboxylic acids. Can be performed stably and efficiently. Furthermore, it is possible to suppress the coloring of products derived from these carboxylic acid esters and carboxylic acids as raw materials and the generation of foreign substances.

It is a graph which shows the result of Experimental Example 1.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

In the present invention, unless otherwise specified below, "oxidation esterification" means a reaction in which a carboxylic acid ester is produced from a cyclic acetal, and "oxidation" means a reaction in which a carboxylic acid is produced from a cyclic acetal. These "oxidation esterification" and "oxidation" are collectively referred to as "oxidation reaction".
Further, in the present invention, "equivalent" means a molar equivalent.

The production method of the present invention is characterized in that a cyclic acetal intermediate is used in a method for producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material.

In the following, the present invention will be described mainly by exemplifying the case where a carboxylic acid ester or carboxylic acid having a furan skeleton is produced as a carboxylic acid ester or carboxylic acid according to the present invention. , The method for producing a flange carboxylic acid ester or a flange carboxylic acid is not limited, and for example, it can be effectively applied to the production of a furanmonocarboxylic acid ester or a furanmonocarboxylic acid. For example, in the case of producing a furanmonocarboxylic acid ester or a furanmonocarboxylic acid, a biomass raw material containing a saccharide unit having 6 carbon atoms as a main component or a biomass raw material in the production of the furanmonocarboxylic acid ester or the furanmonocarboxylic acid described below. A raw material containing a saccharide having 6 carbon atoms produced from a biomass raw material through a saccharification process (hereinafter, "raw material containing saccharide" is referred to as "sugar raw material") is a biomass raw material containing a saccharide unit having 5 carbon atoms. Alternatively, a furanmonocarboxylic acid ester or a furanmonocarboxylic acid can be produced by changing to a sugar raw material. Further, the furanmonocarboxylic acid ester or furanmonocarboxylic acid can also be produced from a saccharide having 6 carbon atoms by appropriately changing the catalyst and / or solvent used.

[mechanism]
In the conventional method, the present inventors produce a carboxylic acid having a furan skeleton via an aldehyde intermediate having a furan skeleton produced by a dehydration reaction from a biomass raw material and / or a saccharide raw material derived from the biomass raw material. It has been found that the various problems described above occur due to the poor thermal stability of the aldehyde intermediate. Therefore, the present inventors have repeatedly studied to solve these problems, such as furfural (hereinafter abbreviated as "FRL") and hydroxymethylfurfural (hereinafter abbreviated as "HMF") produced by a dehydration reaction. The aldehyde intermediate of No. 1 is immediately converted to cyclic acetal by reaction with diol, preferably at the same time as the formation of a furan skeleton by dehydration reaction to obtain a cyclic acetal intermediate having high thermal stability. It has been found that the above-mentioned various problems can be solved by producing a carboxylic acid ester or a carboxylic acid by an oxidation reaction. The carboxylic acid of interest in the present invention can also be produced by hydrolyzing the carboxylic acid ester produced through the above steps.

Hereinafter, the case where the aldehyde having a furan skeleton is HMF (reaction formula (A) above) will be described as an example. HMF produced by a dehydration reaction from a biomass raw material and / or a saccharide raw material derived from the biomass raw material is a cyclic acetal. To make it, the diol may be present in the reaction system. As the diol to be used, 1,3-propanediol (1,3-PD) or ethylene glycol (EG) is selected as a preferable diol, and 1,3 for the reason that the thermal stability of the acetal formed is remarkably improved. -Propanediol (1,3-PD) is particularly preferred.

Specifically, by allowing 1,3-propanediol (1,3-PD) or ethylene glycol (EG) to be present in the dehydration reaction system, the HMF produced by the dehydration reaction can be obtained as shown in the reaction formula below. , Immediately react with 1,3-propanediol (1,3-PD) or ethylene glycol (EG) to produce HMF 1,3-propanediol acetal (hereinafter abbreviated as "PD-HMF") or HMF. Is converted to ethylene glycol acetal compound (hereinafter abbreviated as "EG-HMF").

As shown in Experimental Example 1 described later, these cyclic acetals are superior in thermal stability as compared with HMF. Therefore, by passing through such a cyclic acetal intermediate, these cyclic acetals can be used.
(1) The formation of oligomers and polymers due to the polymerization of HMF is suppressed.
(2) The reaction yield can be maintained higher than that of (1) above.
(3) From (1) above, it is difficult for dirt caused by by-products to adhere to the reactor and piping, and stable production can be achieved by preventing problems such as a decrease in thermal conductivity and blockage in the piping. Furthermore, it is possible to obtain a high-quality product by preventing the generation of coloring and foreign substances caused by by-products.
The effect is played.

When the HMF is formed into a cyclic acetal, a diol may be added to the reaction system as described above. Further, the cyclic acetal produced by the reaction of the diol added to the reaction system with the HMF is immediately subjected to an oxidative esterification reaction in an oxidizing reaction atmosphere containing oxygen gas or the like in the presence of alcohol, as described below. It is converted to a diester of frangylcarboxylic acid.

Further, since the cyclic acetal of the present invention is stable in water under basic conditions, as another embodiment, the cyclic acetal of the present invention is oxidized in water in an oxidizing reaction atmosphere containing oxygen gas or the like in the presence of a base as follows. , Converted to frangylcarboxylic acid.

That is, in the present invention, oxidative esterification is continuously performed when producing a carboxylic acid ester, and oxidation is continuously performed when producing a carboxylic acid through a dehydration / cyclic acetalization step from a biomass raw material and / or a saccharide raw material. And do it. According to this method, a series of reactions can be carried out in the same reaction system, and an efficient carboxylic acid ester or carboxylic acid can be produced.

In addition, in the above-mentioned non-patent document 2, in the production of dimethylesterfurfuralcarboxylic acid, a methanol acetal product of HMF (hereinafter abbreviated as “Me-HMF”) is produced as a by-product, and this product is immediately intended. Although it has been shown that it is converted to the carboxylic acid ester of HMF, as shown in Experimental Example 1 described later, even if it is an acetal product of HMF, that is not a cyclic acetal is inferior in thermal stability, and the present invention. The object of the invention cannot be achieved.

Hereinafter, preferred embodiments of the present invention will be described in detail.

[Biomass raw material]
The biomass raw material in the present invention is stored by converting the solar energy into starch, cellulose, hemicellulose, etc. by the photosynthetic action of plants, the body of an animal that grows by eating a plant, the body of a plant, or the like. Includes products made by processing animal bodies. Biomass raw materials include, for example, wood, rice straw, rice husk, rice bran, old rice, corn, sugar cane, cassava, sago palm, cardon, switchgrass, pine wood, poplar wood, maple wood, okara, corn cob, corn stove, corn fiber. , Tapioca, bagasse, vegetable oil residue, potato, buckwheat, soybean, fat, waste paper, papermaking residue, marine product residue, livestock excrement, sewage sludge, food waste and the like. Among them, wood, rice straw, rice husks, rice bran, old rice, corn, sugar cane, cassaba, sago palm, cardon, switch glass, pine wood, poplar wood, maple wood, okara, corn cob, corn stover, corn fiber, tapioca, bagasse, Plant resources such as vegetable oil residue, potatoes, buckwheat, soybeans, used paper, and papermaking residues are preferable, and more preferably wood, rice straw, rice husks, old rice, corn, sugar cane, cassava, sago palm, cardon, switchgrass, pine, poplar. Wood, maple wood, corn cob, corn stober, corn fiber, bagasse, potatoes, waste paper, paper residue, most preferably corn, sugar cane, cassaba, sago palm, bagasse, cardon, switchgrass, pine wood, poplar wood, maple wood , Corn Cobb, Corn Stover, Corn Fiber.

In the present invention, for example, using known methods such as Green Chemisry 16 (2014) 4816-4838 and the documents described in the cited references thereof, direct induction from these biomass raw materials to FRL or HMF is performed, and then the FRL is derived. The method of inducing the cyclic acetal by the reaction of the HMF with the diol is preferable because it does not need to go through the saccharification step from the biomass raw material and the number of reaction steps to the final target is reduced. Further, the biomass raw material and the diol may coexist and be directly induced into the cyclic acetal form of FRL or HMF by using the method. In terms of a small number of reaction steps and an efficient reaction process, the latter method of coexisting a biomass raw material and a diol to directly obtain a cyclic acetal is preferable.

[Saccharification]
In the present invention, there is no particular limitation other than the method of directly inducing FRL, HMF and their cyclic acetals from the above-mentioned biomass raw material, but for example, the biomass raw material is chemically treated with an acid or alkali, or a microorganism is used. Through known pretreatment and saccharification steps such as biological treatment and physical treatment, polysaccharides contained in biomass raw materials are decomposed (saccharified) into saccharides, which are the constituent units of the polysaccharides, and oligosaccharides, disaccharides and monosaccharides. A method of obtaining a sugar solution containing the above-mentioned substances, obtaining FRL or HMF from the sugar solution, and reacting the sugar solution with a diol to induce them into a cyclic acetal form can also be preferably used. By using this method, it is possible to avoid a decrease in the reaction yield of the acetalization reaction and the purity of the produced acetal compound due to foreign substances and impurities contained in the biomass raw material.

The method for saccharifying the biomass raw material is not particularly limited, and for example, known methods such as Green Chemisry 16 (2014) 4816-4838 and the documents described in the cited references can be used.

The step is not particularly limited, but usually includes a miniaturization step by pretreatment such as chipping, shaving, and grinding the biomass raw material. If necessary, a grinding step using a grinder or a mill is further included. The biomass raw material refined in this way is further subjected to a pretreatment / saccharification step to produce a sugar solution. Specific methods thereof include acid treatment with a strong acid such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid, and alkali treatment. , Chemical methods such as ammonia freeze-steaming and blasting, solvent extraction, subcritical fluid treatment, supercritical fluid treatment, oxidant treatment, and physical methods such as fine pulverization, steaming and blasting, microwave treatment, electron beam irradiation, etc. Biological treatments such as hydrolysis by microbial or enzymatic treatments, or combinations thereof can be mentioned.

Examples of the saccharides derived from the above biomass raw materials include hexoses such as glucose, mannose, galactose, fructose, sorbose and tagatose, pentoses such as arabinose, xylose, ribose, xylose and ribulose, pentose, xylose, saccharose and starch. Disaccharides such as cellulose, oligosaccharides, and polysaccharides are used, of which glucose, fructose, and xylose are preferable. Among them, fructose and xylose are particularly preferable because of the high reaction yield. On the other hand, cellulose and hemicellulose are preferable as sugars derived from plant resources in a broader sense.

The sugar solution obtained by saccharification of the biomass raw material is usually an aqueous solution of saccharides, and may contain other components in addition to water and saccharides. The other components are not particularly limited, but may contain, for example, by-products other than saccharides produced when saccharides are obtained from the biomass raw material and impurities contained in the saccharide raw material. Specific examples of such impurities include carbonyl compounds other than saccharides, alcohol compounds such as aliphatic conjugated alcohols, lignin-derived phenol compounds, alkali metal compounds, alkaline earth metal compounds, nitrogen compounds, and sulfur compounds. Examples thereof include halogen compounds and inorganic compounds such as sulfate ions.

The total concentration of sugars contained in the sugar solution in the present invention (hereinafter referred to as "sugar concentration") varies greatly depending on the origin of the sugar solution, the type of sugar contained, and the like, and is not particularly limited, but the lower limit thereof is usually set. It is 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more, while the upper limit thereof is usually 60% by mass or less, more preferably 50% by mass or less. This sugar solution may be used as it is in the next step, and if necessary, a method of distilling water under reduced pressure, a method of heating and distilling water, or the nano described in International Publication WO2010 / 067785. A concentrated sugar solution in which a sugar component is concentrated may be obtained by using a method of filtering through a filtration membrane and / or a reverse osmosis membrane and used in the next step. In particular, the method of concentrating the sugar solution is preferable in that the productivity of the entire process is improved in the subsequent dehydration reaction and acetalization reaction.

Further, as another means, a method of separating monosaccharides such as glucose, fructose, and xylose from the sugar solution using a known method and subjecting the separated monosaccharides to the next step reduces the amount of impurities in the raw material. This is the most preferable embodiment in that stable long-term operation is possible because the reaction yield of the subsequent reaction step can be improved and the amount of fluctuation between lots can be reduced. These monosaccharides are currently available on an industrial scale. In the present invention, isolated monosaccharides may be additionally added in order to obtain a sugar solution having a high content of sugar components.

[Dehydration / cyclic acetalization]
In the production of the carboxylic acid ester or carboxylic acid via the cyclic acetal intermediate in the present invention, a method for directly producing the cyclic acetal intermediate from the biomass raw material, or a method of once inducing the cyclic acetal intermediate from the biomass raw material to the saccharide raw material through a saccharification step is performed. A method for producing a cyclic acetal intermediate from a saccharide raw material is used.

Further, in these methods, in order to produce a cyclic acetal intermediate from a biomass raw material and / or a saccharide raw material, a step of producing FRL and / or HMF from a biomass raw material and / or a saccharide raw material, and FRL and / or HMF The FRL and / or HMF produced from a biomass raw material and / or a saccharide raw material may be subjected to two steps, that is, a step of producing a cyclic acetal compound from the raw material (hereinafter, this method is referred to as a “two-step method”). It may be carried out in one step so as to be immediately converted into a cyclic acetal body (hereinafter, this method is referred to as a "one-step method"). That is, in the presence of the cyclic acetalization diol described later, FRL and / or HMF having low thermal stability is immediately converted into a cyclic acetal form of FRL and / or HMF, so that the biomass raw material or saccharide raw material is dehydrated. By allowing the cyclic acetalization diol to be present in the production reaction system of the produced FRL and / or HMF, a cyclic acetal intermediate having high thermal stability can be formed in the same reaction system. This not only improves the reaction yield of the intermediate, but also makes it possible to reduce the formation of colored substances and polymers produced as by-products, which is industrially advantageous in that contamination of these products is suppressed. It becomes a manufacturing process. In particular, the effect of the present invention becomes remarkable by adopting a manufacturing process via an HMF acetal intermediate.

When the cyclic acetal intermediate is produced by the two-step method, the once produced FRL and / or HMF is isolated and / or purified (hereinafter referred to as "isolation / purification") in another reaction vessel. Cyclic acetalization may be performed or cyclic acetalization may be performed in the same reaction vessel without isolating / purifying FRL and / or HMF.

The production of FRL or HMF from a biomass raw material and / or a saccharide raw material, and further its cyclic acetal form is preferably carried out in a solvent in the presence of a catalyst. The catalyst may be any as long as it can produce FRL or HMF from a biomass raw material or a sugar raw material, and further a cyclic acetal form thereof, and is not particularly limited, but is usually hydrochloric acid, sulfuric acid, phosphoric acid, nitrate, ore. Inorganic acids such as acids and their alkali metals or metal salts such as alkaline earth metals, sulfonic acids such as p-toluene sulfonic acid and their alkali metals or metal salts such as alkaline earth metals, amber list, amber light, Acidic cation exchange resin such as diamond, zeolite, Al ₂ O ₃ , TIO ₂ , ZrO ₂ , SiO _2- Al ₂ O ₃ , SiO _2- MgO, SiO _{2- TIO 2} , Nb ₂ O ₅ , YNbO ₄ , _{SnO 2, In 2 O 3,} Ga 2 O 3, WO 3, MoO 3, Ta 2 O 5, CeO 2, Nb 2 O 5 -WO 3, Nb 2 O 5 -MoO 3, TiO 2 -WO 3, TiO _{2 -MoO 3, SiO 2 -Nb 2} O 5, SiO 2 -Ta 2 O 5, SiO 2 -ZrO metal oxides and metal composite oxides such as _2, clays, sulfated fixed catalyst such as sulfated ZrO _2, Examples thereof include phosphoric acid immobilization catalysts such as titania and niobia treated with phosphoric acid, and heteropolyacids.

In addition, aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid and caproic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, pimeric acid, suberic acid, azelaic acid, sebacic acid, aconitic acid and itaconic acid. , Oxaloacetic acid, fumaric acid, maleic acid, cyclopentanedicarboxylic acid, cyclohexanedicarboxylic acid and other aliphatic dicarboxylic acids, cyclohexanetricarboxylic acid and other aliphatic tricarboxylic acids, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, Aromatic carboxylic acids such as trimellitic acid, hemmellitic acid, merophanic acid, prenitoic acid, pyromeritic acid, benzenepentacarboxylic acid and melitonic acid, organic acids such as hydroxycarboxylic acid such as lactic acid, malic acid, citric acid and tartrate acid and Salts such as alkali metals and alkaline earth metals in which at least a part of these organic acids are neutralized can also be used as a catalyst.

In the present invention, among the above catalysts, it is preferable to carry out the reaction in a non-uniform system using a solid catalyst insoluble in the reaction solvent because the continuous flow reaction is easy and the reaction selectivity is high. Specifically, among the above catalysts, acidic cation exchange resins such as amber list, amber light, and diamond ion, zeolite, Nb ₂ O ₅ , YNbO ₄ , Ta ₂ O ₅ , Nb ₂ O _5- WO ₃ , and so on. Metal oxides and metal composite oxides such as Nb ₂ O _5- MoO ₃ , TiO _2- WO ₃ , TiO _2- MoO ₃ , SiO _2- Nb ₂ O ₅ , SiO _2- Ta ₂ O _{5, clay, sulfated} Sulfate immobilization catalysts such as ZrO ₂ and phosphoric acid immobilization catalysts such as titania and niobia treated with phosphoric acid are preferable. _{Of these, zeolite, Nb 2} O ₅ , Nb ₂ O _5- WO ₃ , Nb ₂ O _5- MoO _{3, are more preferable, and zeolite, Nb 2} O, in particular, are particularly preferable in that only the acetalization reaction of HMF proceeds selectively. ₅ is preferable.

These catalysts may be used alone or in combination of two or more. When two or more types of catalysts are used, the combination thereof is not particularly limited, and even those in which each metal has catalytic activity (cocatalyst) can improve the catalytic activity of one or more types of metals (auxiliary catalyst). You may.

When the catalyst is soluble in a solvent, these catalysts usually have a lower limit of 0.001% by mass or more, preferably 0.005% by mass or more, more preferably 0, based on the biomass raw material or the saccharide raw material. 0.01% by mass or more, more preferably 0.05% by mass or more, while the upper limit thereof is 50% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less. Is. On the other hand, this does not apply to the case where a solid catalyst insoluble in the reaction solvent is used and a continuous reaction is carried out in a fixed bed reactor or a suspension bed reactor, for example.

As the solvent, water or an organic solvent is usually used, but it may be preferable to use a mixed solvent of water and an organic solvent. From the viewpoint of cost advantage, it is preferable to use a single solvent as the reaction solvent, and from the viewpoint of improving the yield of the cyclic acetal intermediate, it is preferable to use a mixed solvent of water and an organic solvent as the reaction solvent. In some cases. Depending on the selection of the organic solvent, the reaction can be carried out with a homogeneous mixed solvent, but since the polymerization and decomposition reactions of the produced FRL and HMF or their cyclic acetals are suppressed and the yield of the cyclic acetals is improved, the yield of the cyclic acetals is improved. It may be preferable to use an organic solvent having a two-layer system consisting of an aqueous layer and an organic layer. That is, by using this method, a continuous extraction reaction for extracting the produced FRL or HMF or its cyclic acetal form in an organic solvent can be carried out, and after the reaction, the reaction solution is separated into two layers to produce a product. Can be efficiently separated from the organic solvent layer.

The organic solvent used is not particularly limited as long as it does not inhibit the produced FRL, HMF, and their acetalization reaction, but is not particularly limited, and is, for example, diethyl ether, tetrahydrofuran (THF), tetrahydropyran, dipropyl. 4 carbon atoms such as ether, diisopropyl ether, methyl-tert-butyl ether, 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, etc. ~ 20 ethers; 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclohexanone, 4-methyl-2-pentanone, 2-heptanone, 5-methyl-2-hexanone, 2, 4-Dimethylpentanone, 5-Nonanone, 4-Decanone, 5-Decanone, 2-Undecanone, 4-Undecanone, 3-Dodecanone, 2-Tridecanone, 2-Tetradecanone, 4-Tetradecanone, 2-Pentadecanone, 3-Pentadecanone, 7-Pentadecanone, 2-hexadecanone, 3-hexadecanone, 4-hexadecanone, 6-hexadecanone, 2-heptadecanone, 4-heptadecanone, 9-heptadecanone, 3-octadecanone, acetophenone and other ketones having 4 to 20 carbon atoms; ethyl acetate , Ethers such as propyl acetate, butyl acetate; methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pen Tanol, 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-hexadecene-1-ol, 1-heptadecanol, 1-octadecanol, 16-methylheptadecene- 1-o Monoalcohols having 1 to 20 carbon atoms such as ru, nonadesyl alcohols and arachidyl alcohols; phenols having 6 to 12 carbon atoms such as phenols, methylphenols, ethylphenols, propylphenols and butylphenols; pentane, hexanes and cyclohexanes. , Heptane, octane, nonane, decane, dodecane, isododecane and other saturated aliphatic hydrocarbon compounds having 3 to 12 carbon atoms; toluene, xylene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene, 1-methylnaphthalene and the like. Aromatic hydrocarbons; lactones such as γ-butyrolactone and γ-valerolactone; halogenated hydrocarbons such as dichloromethane, chloroform, dichloroethane, tetrachloroethane, hexachloroethane; others, dimethylacetamide, N, N-dimethylformamide, N-Methylmorpholin, N-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphate triamide, tetramethylurea, dimethylsulfoxide, sulfolane, isosorbide, isosorbidodimethylether, propylene carbonate, and these. Examples thereof include a mixture of. Others, for example, pyrrolidinium salts such as 1-butyl-1-methylpyrrolidinium bromide; piperidinium salts such as 1-butyl-1-methylpiperidinium triflate; pyridinium salts such as 1-butylpyridinium tetrafluoroborate; 1- Imidazolium salts such as ethyl-3-methylimidazolium chloride; ammonium salts such as tetrabutylammonium chloride; phosphonium salts such as tetrabutylphosphonium bromide; sulfonium salts such as triethylsulfonium bis (trifluoromethanesulfonyl) imide, etc. A liquid may be used.

Among these, it is preferable that the organic solvent is selected from at least one of the group consisting of ethers, ketones, esters, alcohols, phenols, lactones, aromatic hydrocarbons, halogenated hydrocarbons and saturated aliphatic hydrocarbons. .. Among these, it is preferable to be selected from at least one of the group consisting of ethers, ketones, esters, alcohols, phenols, lactones, aromatic hydrocarbons, and saturated aliphatic hydrocarbons because of their low environmental impact. ..

Further, when the reaction is carried out in a two-layer system, the extraction efficiency of the cyclic acetal compound is high, and the amount of the organic solvent dissolved in water is small, so that methylethylketone, methylisobutylketone, acetophenone, cyclohexanone, 1-butanol, 2-butanol, 1-pentanol, 1-hexanone, propylphenol, butylphenol, butylphenol, toluene, xylene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene, 1-methylnaphthalene, cyclohexane, isododecane are preferable. Of these, methyl ethyl ketone, methyl isobutyl ketone, butyl phenol, cyclohexanone, and toluene are particularly preferable. It is preferable to use only one of these organic solvents in consideration of recovery and reuse of the solvent, but two or more of these organic solvents may be used.

In the present invention, the amount of the organic solvent used when using a mixed solvent of water and an organic solvent is not particularly limited as long as the gist of the present invention is not impaired, but is preferably 10 to 5000% by mass with respect to water. In particular, it is preferably 10 to 1000% by mass. If the amount of the organic solvent used is too small than the above range, the resulting FRL, HMF or their cyclic acetals are likely to undergo polymerization or decomposition reactions, and the yield of the acetal intermediates tends to decrease accordingly. If the amount is too large, it becomes necessary to remove a large amount of organic solvent when recovering the generated cyclic acetal intermediate, which not only reduces the recovery efficiency and complicates the process, but also increases the reaction equipment and is economical. It tends to be disadvantageous.

Therefore, when a sugar solution is used as the sugar raw material, it is preferable to add an organic solvent or water and an organic solvent to the water in the sugar solution so as to fall within the above range.

The diol added for cyclic acetalization of HMF (hereinafter, may be referred to as “cyclic acetalization diol”) is appropriately determined according to the type of cyclic acetal intermediate to be produced, and is used in the production of PD-HMF. Is a diol capable of forming a 6-membered ring skeleton acetal, and a diol capable of forming a 5-membered ring skeleton acetal is used for the production of EG-HMF. Specifically, 1,3-propanediol is exemplified for the production of PD-HMF, and ethylene glycol is exemplified for the production of EG-HMF, but the production is not limited to these. 2-Methyl-1,3-propanediol, neopentyl glycol, 1,3 having an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms as a substituent. -Butanediol, 1,3-pentanediol, 1-phenyl-1,3-propanediol, 2-phenyl-1,3-propanediol, 1,2-propanediol, 1,2-butanediol, 1,2 -Pentanediol, 1-phenyl-ethylene glycol and the like may be used. Catechol is also preferably used. Although it is possible to use two or more of these cyclic acetalization diols, one type is usually used. In the present invention, the above diol is used as a reaction reagent as the cyclic acetalizing agent, but the diol can also be used as the above organic solvent, which complicates the subsequent recovery and purification steps of the reaction solvent. The method of using the diol as a solvent and acetalizing agent is one of the preferred embodiments because the above can be avoided.

The amount of the biomass raw material and / or the saccharide raw material used with respect to the reaction solvent is not particularly limited when the reaction is carried out in a heterogeneous system.

When the raw material is dissolved in the reaction solvent and carried out in a uniform system, the lower limit of the concentration of the raw material with respect to the reaction solvent is usually 0.1% by mass or more, preferably 1% by mass or more, and more preferably 5% by mass. As mentioned above, it is more preferably 10% by mass or more, and particularly preferably 15% by mass or more. On the other hand, the upper limit is 50% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less. When the raw material concentration is at least the above lower limit, the separation efficiency between the cyclic acetal intermediate and the solvent tends to be high, and when the raw material concentration is at least the above upper limit, side reactions can be suppressed and the yield of the cyclic acetal is increased. It tends to be high and is preferable. In the case of the two-step method, the concentration of the raw material in the reaction solution when the reaction is carried out in a uniform system is the solvent used for the reaction (when a sugar solution is used, water in the sugar solution is included) and the catalyst. It is the ratio of the raw material to the total with the raw material, and in the case of the one-step method, it is the ratio of the raw material to the total to which the above-mentioned cyclic acetalizing diol is further added.

In the case of the two-step method, the reaction temperature of the dehydration reaction for obtaining HMF is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, preferably 250 ° C. or lower, and more preferably 230 ° C. or lower. Is. When the reaction temperature is equal to or higher than the above lower limit, the reaction tends to proceed faster, and the productivity of the product is improved. When the reaction temperature is not more than the above upper limit value, decomposition and polymerization of the product and the reaction intermediate tend to be suppressed, and the yield of the product tends to be improved, which is preferable. Further, in the case of the two-step method, after FRL and HMF are produced by a dehydration reaction, the produced FRL and HMF are isolated / purified, or the above-mentioned cyclic acetalization diol is added without isolation / purification. Further dehydration and cyclic acetalization may be carried out to obtain a cyclic acetal compound of FRL or HMF. The above-mentioned diol for cyclic acetalization used for cyclic acetalization may be equal to or greater than the expected production equivalent of FRL or HMF, and is usually used 1 to 10 times the expected production equivalent of FRL or HMF. , The case where the cyclic acetalization diol is used as a solvent is not particularly limited. The reaction during cyclic acetalization is preferably carried out at a temperature of 10 to 150 ° C.

Further, in the case of the one-step method, a solvent is added to the monosaccharide or the sugar solution so that the concentration of the monosaccharide in the reaction solution and the amount of the organic solvent in the reaction solvent are within the above-mentioned ranges, and the above-mentioned diol for cyclic acetalization is further added. Is added 1 to 10 times as much as the expected amount of FRL or HMF produced, and the lower limit of the reaction temperature is usually 100 ° C. or higher, preferably 120 ° C. or higher, while the upper limit thereof is. It is preferable to carry out the dehydration and cyclic acetalization reaction at 250 ° C. or lower, preferably 230 ° C. or lower.

The reaction solution in which the cyclic acetal intermediate is produced by the two-step method or the one-step method in this manner is used as it is in an oxidative esterification step in the presence of alcohol or in the presence of water according to the following target products. It may be subjected to an oxidation step, or the produced cyclic acetal intermediate may be isolated / purified and then subjected to the oxidative esterification step or the oxidation step.

[Oxidative esterification and oxidation]
In the present invention, a carboxylic acid ester or a carboxylic acid is produced by oxidative esterification or oxidation through a dehydration / cyclic acetalization step from a biomass raw material and / or a saccharide raw material, respectively.
The oxidative esterification or oxidation of the cyclic acetal intermediate is preferably carried out in the presence of a catalyst, and the oxidative esterification catalyst and the oxidation catalyst are not limited as long as they are a metal or a metal compound having an oxidizing ability, for example. Periodic Table of Platinum, Palladium, Nickel, Iron, Luthenium, Cobalt, etc. Group 8-10 Metals and their compounds, Periodic Table of Copper, Silver, Gold, etc. Group 11 Metals and their compounds, Periodic Table Group 12 of zinc, etc. Metals and their compounds, Periodic Table Group 13 metals and their compounds such as indium, Periodic Table Group 14 metals and their compounds such as tin and lead, Periodic Table Group 7 metals and their compounds such as manganese and renium, Chromium, Periodic Table Group 6 metals and their compounds such as molybdenum, Periodic Table Group 5 metals and their compounds such as niobium and tantalum, Periodic Table Group 4 metals and their compounds such as zirconium, Periodic Table Group 3 metals such as scandium And their compounds, Group 2 metals of the Periodic Table such as magnesium and calcium and their compounds, Group 1 metals of the Periodic Table such as cesium and their compounds, and mixtures (including alloys) of these metals. In particular, metals of Groups 6 to 12 of the Periodic Table and their compounds and mixtures thereof (including alloys) are preferable, and metals of Groups 7 to 11 of the Periodic Table and their compounds are more preferable, and among them, platinum, palladium and renium are particularly preferable. , Magnesium, copper, silver, gold, zinc, manganese, cobalt and compounds thereof are preferred, and platinum, palladium, renium, copper, silver, gold, cobalt, manganese and compounds thereof are most preferably used. Examples of the compound include oxides of these metals, alkoxy compounds, alkyl compounds, organic acid salts and the like, but metal elements and oxides of metals are preferable. Further, these metal catalysts are preferably used as metal-supporting catalysts supported on various carriers. Examples of the carrier include natural minerals such as carbon, silica, alumina, titania, zirconia, niobia, ceria, tungsten oxide, silicon-carbide, boron-carbide, titanium-carbide, diatomaceous earth, and layered silicate. Of these, carbon, titania, and ceria are preferable in terms of ease of catalyst preparation and activity. These catalysts may be used alone, in combination of two or more, or may be additionally used later.

Metal-bearing catalysts include gold / carbon, gold / titania, gold / zirconia, gold / ceria, platinum / carbon, platinum / titania, platinum / ceria, palladium / carbon, palladium / silica, palladium / alumina, renium / carbon, Renium / silica, renium / alumina, cobalt / carbon, cobalt / titania, cobalt / ceria are preferred, gold / carbon, gold / titania, gold / zirconia, gold / ceria, platinum / carbon, palladium / carbon, palladium / silica, Renium / carbon, renium / silica, cobalt / carbon, cobalt / titania, and cobalt / ceria are more preferable, among which gold / titania, gold / zirconia, gold / ceria, and cobalt / carbon have high reactive activity and are used metals. Is particularly preferable in that it is easy to recover.

The amount of the oxidation esterification catalyst or the oxidation catalyst used is preferably 0.002 mass ppm or more and 100,000 mass ppm or less as a metal equivalent amount with respect to the raw material. The lower limit of the amount of the oxidation esterification catalyst or the oxidation catalyst used is more preferably 0.02 mass ppm, more preferably 0.2 mass ppm, and 2 mass ppm as the metal equivalent amount with respect to the raw material. Most preferred. The upper limit of the amount of the oxidation esterification catalyst or the oxidation catalyst used is more preferably 50,000 mass ppm in terms of metal with respect to the raw material, more preferably 20,000 mass ppm, and most preferably 10,000 mass ppm. If the amount of the catalyst used is less than 0.002 mass ppm, the reaction time will be too long and inefficient, and if it is more than 100,000 mass ppm, the cost of the catalyst will be high, which is uneconomical and the post-treatment load will be high. It is disadvantageous in that it becomes large and the product is easily colored.

In the oxidation reaction of cyclic acetals of HMF and FRL, the presence of a base improves the stability of the cyclic acetals and suppresses side reactions such as polymerization of reaction intermediates and ring-opening reactions. Since the yield of the carboxylic acid ester or the carboxylic acid may be improved, the oxidation reaction may be carried out in the presence of a base. Examples of such bases include inorganic bases such as sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, potassium hydroxide, potassium carbonate and potassium hydrogencarbonate, and organic bases such as triethylamine, but the removal efficiency from the product is high. Of these, inorganic bases are preferred for good reasons.

The amount of the base used when carrying out the oxidation reaction in the presence of the base is not particularly limited, but the lower limit thereof is 0.01 equivalent or more, preferably 0.1 equivalent or more with respect to the cyclic acetal of HMF or FRL. Yes, the upper limit is 10 equivalents or less, preferably 5 equivalents or less, more preferably 3 equivalents or less. By adopting such an amount, the stability of the cyclic acetal can be improved and side reactions such as polymerization of reaction intermediates and ring-opening reaction can be suppressed, and at the same time, the target carboxylic acid ester or carboxylic acid can be used. The yield can be improved.

In the oxidation reaction of cyclic acetals of HMF and FRL, when the reaction is carried out in the presence of a metal catalyst, the reaction is carried out while passing a gas through the reactor. Preferably, oxygen is contained in the gas.

The oxygen source used in the oxidation reaction is not particularly limited, such as an oxygen-containing organic compound, an inorganic peroxide, and an oxygen-containing gas, but an oxygen-containing gas such as oxygen or air, which is a gas that does not need to be separated and purified after the reaction is completed, is used. , It is preferable to carry out the operation while circulating the oxygen-containing gas in the reactor.

When an oxygen-containing gas is used, the oxygen content in the oxygen-containing gas is preferably 20% by volume or more, more preferably 50% by volume or more, and it is particularly preferable to use pure oxygen (99% or more). Oxygen may be introduced into the gas phase or blown into the reaction solution, but it is more preferable to blow oxygen into the reaction layer.

The reaction temperature when carrying out the oxidation reaction of the cyclic acetal is preferably room temperature or higher and 200 ° C. or lower, but the lower limit of the reaction temperature is more preferably 30 ° C., further preferably 40 ° C., and most preferably 60 ° C. The upper limit is more preferably 180 ° C, even more preferably 150 ° C, and most preferably 130 ° C. If the reaction temperature is too low, a long reaction time is required, and if the reaction temperature is too high, the reaction becomes too vigorous, which makes control difficult or causes coloring, which is not preferable.

The time for circulating the oxygen-containing gas starts from the time when the oxygen-containing gas to be circulated is first introduced into the reactor, and is usually 10 minutes to 30 hours, preferably 30 minutes to 20 hours, more preferably 1 hour to. It is 10 hours, more preferably 1 to 5 hours. If this time is too short, the reaction will be too violent and it will be difficult to control the reaction temperature, and if it is too long, the manufacturing cost will be high, which is not preferable. When the oxidation reaction is continuously carried out, the reaction time is not limited to this.

The rate at which the oxygen-containing gas is circulated through the reactor is usually 1 mL / min to 100 L / min, preferably 10 mL / min to 10 L / min, more preferably 100 mL / min to 5 L / min, and even more preferably 500 mL / min to 500 mL / min. It is 1 L / min. If this time is too slow, the reaction rate will be slow, the production efficiency will be poor, and the production cost will be high, which is not preferable. Further, if it is too fast, the oxygen consumption efficiency is poor and the amount of oxygen used increases, which increases the cost and is not preferable.

In addition, examples of the distribution method include a method of blowing into the liquid layer of the reactor, a method of blowing into the air layer portion of the reactor, and the like, and a method of blowing into the liquid layer of the reactor is preferable.
The oxygen-containing gas may be continuously or intermittently distributed, but it is preferably a method of continuously distributing the gas. In the case of intermittent distribution, it is preferable to prepare so that the interval of intermittent distribution is not too long so as not to run out of oxygen.
Further, the oxygen-containing gas may be supplied into the reaction vessel so as to be pressurized to carry out the oxidation reaction. The reaction pressure at that time is usually 0.1 MPa or more, preferably 0.3 MPa or more, more preferably 0.4 MPa or more, usually 15 MPa or less, preferably 10 MPa or less, more preferably 5 MPa or less, still more preferably 3 MPa or less. Especially preferably, it is 1 MPa or less. In general, increasing the reaction pressure improves the reaction rate, which is a preferable embodiment. On the other hand, in order to carry out at a high reaction pressure, equipment such as a reactor with specially increased pressure resistance is required, and oxidation Vaccine reactions can be prominent due to increased capacity.

The reaction solvent in the oxidative esterification is not particularly limited as long as it is a solvent that dissolves the cyclic acetal as a raw material, and the same solvent as the reaction solvent in the dehydration / cyclic acetalization described above or the diol described above can be used. .. When the cyclic acetal intermediate is isolated and then oxidatively esterified, the solvent does not necessarily have to be a mixed solvent, and a single solvent of an alcohol such as monoalcohol or diol may be used.
The reaction solvent in the oxidation is not particularly limited as long as it is a solvent containing water that dissolves the cyclic acetal as a raw material, and the above-mentioned mixed solvent of the reaction solvent and water in the dehydration / cyclic acetalization and the above-mentioned diol and water A mixed solvent of the above or an aqueous solvent can be used. When the cyclic acetal intermediate is isolated and then oxidized, the solvent does not necessarily have to be a mixed solvent, and an aqueous solvent may be used. Here, the content of water when a mixed solvent with water is used is not particularly limited as long as it is 1 equivalent or more with respect to the cyclic acetal intermediate, but usually, as a volume ratio, the lower limit is 1 volume% or more. It is preferably 10% by volume or more, more preferably 50% by volume or more, and there is no upper limit.

The amount of the reaction solvent used is not particularly limited, but the lower limit of the mass ratio with respect to the cyclic acetal of the raw material is usually 1 time or more, preferably 2 times or more, more preferably 3 times or more, still more preferably 4 times. As mentioned above, it is most preferably 5 times or more, while the upper limit is usually 100 times or less, preferably 50 times or less, more preferably 30 times or less, still more preferably 20 times or less, and most preferably 8 times or less. If the amount of the solvent used is too large, the reaction vessel becomes too large, the production efficiency is lowered, and it is not preferable as an industrial process in which economic efficiency is required. On the other hand, if the amount is too small, the reaction rate tends to decrease and the reaction time tends to be long, which may be unfavorable. However, the acetal intermediate of the present invention is excellent in thermal stability and polymerization stability, and has a characteristic that oligomers such as fumin and by-products such as polymers and levulinic acid are less likely to occur in the oxidation reaction even under high concentration conditions. It is possible to produce carboxylic acid esters and carboxylic acids under higher concentration conditions, that is, the amount of solvent used is further reduced.

In the present invention, when the cyclic acetal intermediate is oxidatively esterified, an alcohol coexists in the reaction system to produce an alcohol ester of a flange carboxylic acid. If the alcohol coexisting here is a cyclic acetalizing diol added in the dehydration / cyclic acetalization step of the previous step, a hydroxyalkyl ester of the flange carboxylic acid is produced as described above, but monool is produced instead of the diol. When coexisting, an alkyl ester of a flange carboxylic acid can be produced. Further, if the diol or monool is present in an amount of 2 equivalents or more with respect to the cyclic acetal intermediate, a diester of a flange carboxylic acid may be formed, and if it is less than 2 equivalents, a monoester may be formed.

In the method for producing a carboxylic acid ester of the present invention, an oxidative esterification step is preferably carried out following the above-mentioned dehydration / cyclic acetalization step, so that the alcohol existing in this oxidative esterification reaction system is dehydrated. In many cases, it is an unreacted residue of the cyclic acetalification diol added for the cyclic acetalization reaction, in which case a hydroxyalkyl ester of the flange carboxylic acid is produced.

When the cyclic acetal intermediate is isolated / purified after the dehydration / cyclic acetalization step and the cyclic acetal intermediate is newly oxidatively esterified in the presence of alcohol, the alcohol to be added is Not limited to the above-mentioned diols for cyclic acetalization, methanol, ethanol, 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-pen Tanol, 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-hexadecene-1-ol, 1-heptadecanol, 1-octadecanol, 16-methylheptadecene Aliphatic monoalcohols having 1 to 20 carbon atoms such as -1-ol, nonadecil alcohol, and araxyl alcohol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4- It may be an aliphatic diol having 4 to 8 carbon atoms such as cyclohexanedimethanol.

In oxidative esterification and oxidation, the reaction solution is preferably agitated to increase the contact efficiency of the raw material with the catalyst and oxygen. The stirring can be performed by any stirring device used for a normal reaction such as a magnetic stirrer, a mechanical stirrer, and a stirring motor equipped with a stirring blade. When the scale becomes large, a stirring motor equipped with a stirring blade is used in terms of power. It is preferable that the stirring is started before the reaction is carried out, the stirring is continuously carried out during the reaction, and the stirring is carried out while the reaction solution is cooled after the reaction is completed.

In the present invention, the carboxylic acid ester having the furan skeleton derived as described above is hydrolyzed in the presence of an acid catalyst to induce the furanmonocarboxylic acid and the furancarboxylic acid as follows. You can also.

[Product recovery method]
The product obtained in each of the above steps may be isolated and / or purified and recovered after the reaction is completed, or used as a raw material for the next step without going through the isolation and / or purification step. You may.

When used as a raw material for the next step without isolation / purification, the reaction may be carried out by a batch reaction, and the reaction solution after completion of the reaction may be directly introduced into the reactor of the next step, or the reaction may be completed. The product may be extracted from the subsequent reaction solution using a different organic solvent and the extract solution may be introduced into the reactor in the next step. When the reaction is carried out by a flow reaction, the reaction solution may be directly flowed to the reactor in the next step under the flow reaction process, and the reaction solution is brought into contact with a different organic solvent to extract the product. After that, the extract may be introduced into the reactor in the next step.

On the other hand, when the product obtained in each step is isolated / purified, it depends on the physical properties of the product, but usually, a solvent distillation method, a solvent distillation and then extraction with an organic solvent, a distillation method, etc. The product can be recovered by a sublimation method, a crystallization method, or a chromatographic method. Here, for example, when a carboxylic acid is obtained by oxidizing a cyclic acetal compound in the presence of a base, the carboxylic acid salt as a product is treated with a mineral acid such as hydrochloric acid or sulfuric acid to induce the carboxylic acid, and then the recovery method is performed. Carboxylic acid can be isolated / purified using.
Among these, particularly when the product is a liquid under the handling temperature condition, a method of recovering the product while purifying it by a distillation method is preferable, and when the product is a solid under the handling temperature condition, crystallization is performed. A method of recovering the product while purifying the product by a method is preferable. At that time, a method of purifying the obtained solid product by washing is a preferable embodiment.

[Circular acetal]
A particularly preferable cyclic acetal in the present invention is a 1,3-propanediol acetal product of FRL or HMF represented by the following formula (2) (hereinafter, may be referred to as “cyclic acetal (2)”), which is described above. Is produced by using 1,3-propanediol as the diol for cyclic acetalization in the dehydration and cyclic acetalization of the above.

(In the formula, A represents a hydrogen atom or -CH ₂ OH.)

As shown in Experimental Example 1 described later, this cyclic acetal has excellent thermal stability, and can be used as a raw material for the above-mentioned oxidative esterification to industrially advantageous carboxylic acid ester or carboxylic acid according to the present invention. Can be manufactured.

Further, this cyclic acetal (2) has a hydroxyl group of carboxylic acid anhydride ((R ² CO) ₂ O (R ² is an alkyl group having 1 to 6 carbon atoms _{) when A is a −CH 2 OH group.} Alternatively, it can be converted into an ester group by reaction with an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent, or an alcohol (R ² OH (R ² has 1 to 6 carbon atoms). It represents an aryl group having 6 to 12 carbon atoms which may have an alkyl group or an alkyl substituent.)) By converting to an ether group by reaction, it is further represented by the following formula (3). It can be induced to an acetal intermediate with excellent thermal stability. The acetal intermediate represented by the following formula (3) uses an HMF hydroxyl group as a carboxylic acid anhydride ((R ² CO) ₂ O (R ² is an alkyl group having 1 to 6 carbon atoms or an alkyl substituent). Represents an aryl group having 6 to 12 carbon atoms which may have an ester group, or an alcohol (R ² OH (R ² is an alkyl group having 1 to 6 carbon atoms) or It represents an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent.)) It may be derived by a reaction with a propanediol after being converted into an ether group by a reaction with)).

(In the formula, B may have -CH ₂ OR ² or -CH ₂ O (C = O) R ² (R ² may have an alkyl group having 1 to 6 carbon atoms or an alkyl substituent. Represents an aryl group having 6 to 12 carbon atoms.) Represents.)
In the case ^{where R 2} is an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent, examples of the alkyl substituent include an alkyl group having 1 to 6 carbon atoms.

That is, in consideration of the above formulas (2) and (3), in the present invention, the cyclic acetal represented by the following formula (1) is mentioned as a preferable cyclic acetal intermediate.

In formula (1), R ¹ is a hydrogen atom, a group represented by _{-CH 2} OH, -CH ₂ OR ² or -CH ₂ O (C = O) R ^{2 , and R 2} has 1 to 6 carbon atoms. Represents an aryl group having 6 to 12 carbon atoms which may have an alkyl group or an alkyl substituent. When R ² has an alkyl substituent, a preferable substituent includes an alkyl group having 1 to 6 carbon atoms.

Hereinafter, the present invention will be described in more detail with reference to Experimental Examples and Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

[Experimental Example 1-1: Evaluation of thermal stability of HMF and HMF acetal]

The thermal stability of HMF (manufactured by Sigma Aldoch) and three types of HMF acetals (PD-HMF, EG-HMF, Me-HMF) obtained by the method of Experimental Example 7 described later are as follows. Evaluation was performed.
A 3 to 4 mg sample was introduced into a pressure-resistant NMR tube and treated at room temperature under vacuum exhaust for 2 hours to remove water contained in the sample. Then, the tube was placed in an oven, the temperature was raised from room temperature to 200 ° C. at 10 ° C./min, and the temperature was maintained at 200 ° C. for 2 hours. 1 mL of CDCl ₃ and an internal standard (benzoic acid, 1 mg) were added to the heated sample, and the residual rate of the sample was analyzed by ^{1 H NMR to evaluate the thermal stability.} The higher the residual rate, the better the thermal stability. The results are shown in FIG.

From FIG. 1, HMF cyclic acetals such as EG-HMF and PD-HMF are superior in thermal stability to HMF, but even in acetal form, acyclic Me-HMF is more thermally stable than HMF. It turns out to be bad.

[Experimental Example 1-2: Evaluation of thermal stability of FRL and FRL acetal]

Results of evaluation of thermal stability of FRL (manufactured by Sigma-Aldrich) and FRL acetal (PD-FRL) obtained by the method of Experimental Example 7 described later by the same method as in Experimental Example 1-1. The residual rate after 2 hours was 12% in the case of FRL, whereas it was remarkably improved to 80% in the case of PD-FRL, and it was found that the thermal stability of the cyclic acetal was high.

[Experimental Example 1-3: Evaluation of thermal stability of ester and ether of PD-HMF]

The ester (PD-HMF-acetate) and ether (PD-HMF-ether) of HMF acetal (PD-HMF) obtained by the method of Experimental Example 7 described later were subjected to the same method as in Experimental Example 1-1. As a result of evaluating the thermal stability, the residual rates after 2 hours were 76% and 74%, respectively, and it was found that the thermal stability was superior to that of HMF.

[Experimental example 2: Temperature dependence of thermal decomposition of HMF acetal]
^{In Experimental Example 1, the residual ratio of the heated sample was analyzed by 1} H NMR in the same manner as in Experimental Example 1 except that PD-HMF was held at 150 ° C. or 180 ° C. for 2 hours, and the results were obtained in Experimental Example. It is shown in Table 1 below together with the result of heating at 200 ° C. in 1.

From Table 1, it can be seen that there is no correlation between the heating temperature and the residual rate. Of the decomposition products of PD-HMF, about 50% was HMF, which is a hydrolyzate of acetal form due to the moisture brought into the solvent.

[Experimental Examples 3-1 to 3-8: Evaluation of yield of PD-HMF from HMF]
HMF (manufactured by Sigma-Aldrich, 50 mg), 1,3-propanediol (75 μL), and a catalyst were added to 2.5 mL of various solvents and stirred to carry out a reaction to obtain PD-HMF. .. The catalyst and solvent used, the reaction temperature, and the reaction time are as shown in Table 2. The β-zeolites used in Experimental Examples 3-4 to 3-7 were calcined in the air at 550 ° C. for 8 hours before use. Chlorobenzene was added to the solution after the reaction as an internal standard, and the produced PD-HMF was quantified by column gas chromatography (manufactured by Shimadzu Corporation: GC2025) to determine the yield of PD-HMF. As the column, DB-FFAP (manufactured by Agilent Technologies Co., Ltd.) was used. The results obtained are shown in Table 2.

[Experimental Example 4: Synthesis of HMF acetal from monosaccharides derived from biomass raw material I]
An experiment was conducted in which HMF acetal was synthesized from glucose by changing the amount of catalyst using _{Nb 2} O ₅ obtained by calcining hydrous niobate (“HY-340” manufactured by CBMM) at 400 ° C. for 4 hours. ..

100 mg or 200 mg of Nb ₂ O ₅ and 20 mg of glucose were placed in a pressure-resistant glass container, and 1.8 mL of THF, 0.2 mL of water and 0.2 mL of 1,3-propanediol were added thereto and sealed. The glass container was placed in an oil bath preheated to 125 ° C. and heated for 1 hour with stirring. After 1 hour of heating and stirring, the container was immediately introduced into cold water to stop the reaction, 25 μL of chlorobenzene was added as an internal standard, and the produced HMF and PD-HMF were gas chromatographed (manufactured by Shimadzu Corporation: GC-). 2025, column: DB-FFAP), the yield was determined with respect to glucose, and the results are shown in Table 3.

From Table 3, No. 1 with a catalyst amount of 100 mg. No. 1 was 200 mg rather than 1. It can be seen that the yield of PD-HMF is higher in No. 2.

[Experimental Example 5: Synthesis of HMF acetal from monosaccharide II]
An experiment was conducted in which the following catalysts were used and the catalyst was changed to synthesize HMF acetal from glucose.

_{Nb 2} O _5: Nb obtained hydrous niobate (CBMM Co. "HY-340") was calcined for 4 hours at 400 ° C. 2 _{O 5}
H-BEA-25: Acid-type β-zeolite catalyst "H-BEA-25" manufactured by Clariant Catalysts, Inc.
Amberlyst-15: Strong cation exchange resin "Amberlyst-15" manufactured by Sigma-Aldrich.
TiO ₂ : Titanium oxide "JRC-TIO-11 (Catalyst Society, reference catalyst)" manufactured by Showa Titanium Co., Ltd.

200 mg of the catalyst shown in Table 4 and 20 mg of glucose were placed in a pressure-resistant glass container, and 1.4 mL of THF, 0.6 mL of water, and 0.2 mL of 1,3-propanediol were added thereto and sealed. The glass container was placed in an oil bath preheated to 125 ° C. and heated for 1 hour with stirring. After heating and stirring for 1 hour, the container was immediately introduced into cold water to stop the reaction, and the produced HMF and PD-HMF were quantified by gas chromatography in the same manner as in Experimental Example 4, and the yield with respect to glucose was determined. The results were obtained and the results are shown in Table 4.

From Table 4, it can be seen that _{Nb 2} O _{5 is particularly preferable as the catalyst.}

[Experimental Example 6: Synthesis of HMF acetal from monosaccharide III]
An experiment was conducted in which HMF acetal was synthesized by changing the monosaccharides of the raw material using _{Nb 2} O ₅ obtained by calcining hydrous niobate (“HY-340” manufactured by CBMM) at 400 ° C. for 4 hours as a catalyst. ..

200 mg of Nb ₂ O ₅ and 20 mg of glucose or fructose were placed in a pressure-resistant glass container, and 1.8 mL of THF, 0.2 mL of water and 0.2 mL of 1,3-propanediol were added thereto and sealed. The glass container was placed in an oil bath preheated to 125 ° C. and heated for 2 hours with stirring. After heating and stirring for 2 hours, the container was immediately introduced into cold water to stop the reaction, and the produced HMF and PD-HMF were quantified by gas chromatography in the same manner as in Experimental Example 4, and the yield with respect to glucose or fructose was obtained. The rates were calculated and the results are shown in Table 5.

[Experimental Example 7: Synthesis of other samples]
<Synthesis of Me-HMF>
HMF (manufactured by Sigma-Aldrich) and paratoluenesulfonic acid were added to methanol, and the mixture was heated and stirred at 60 ° C. The catalyst was separated from the solution after the reaction and purified by column chromatography to obtain Me-HMF in a yield of 78%.

<Synthesis of HMF acetate body>
To an acetonitrile solution (0.1 mol / L) in which HMF (manufactured by Sigma Aldrich) is dissolved, 1.5 molar equivalents of anhydrous acetic acid and 2 molar equivalents of triethylamine are added, and the mixture is stirred at room temperature for 1 hour. The hydroxyl group of HMF was converted to acetonitrile. The obtained product was purified by column chromatography to obtain an HMF acetate compound.

<Synthesis of EG-HMF>
The HMF acetate obtained by the above method was dissolved in a dichloromethane solution (HMF acetate concentration: 0.1 mol / L), and a catalytic amount (0.01 equivalent) of indium trifluoromethanesulfonate (In (OTf) ₃ ) was added thereto. Excess amounts of trimethyl orthoformate and ethylene glycol were added, and the mixture was stirred at room temperature to convert the aldehyde moiety bound to the furan ring into a cyclic acetal. Finally, the product was reacted with sodium carbonate in a methanol solution to decompose the acetate moiety to obtain the desired ethylene glycol-HMF acetal (EG-HMF).

<Synthesis of PD-HMF>
The HMF acetate obtained by the above method was dissolved in a dichloromethane solution (HMF acetate concentration: 0.1 mol / L), and a catalytic amount (0.01 equivalent) of indium trifluoromethanesulfonate (In (OTf) ₃ ) was added thereto. Excess amounts of trimethyl orthoformate and 1,3-propanediol were added and stirred at room temperature to convert the aldehyde moiety bound to the furan ring into cyclic acetals. Finally, the desired propanediol-HMF acetal (PD-HMF) was obtained by reacting the product with sodium carbonate in a methanol solution to decompose the acetate moiety.

<Synthesis of PD-HMF-ether>
In a mixed solution of HMF (Sigma-Aldrich, 50 mg), methanol (2 mL), and 1,3-propanediol (0.1 mL), 0.01 molar equivalent of In (OTf) ₃ and excess amount with respect to HMF. Trimethyl orthoformate was added, and the mixture was stirred at room temperature for 3 hours. The catalyst was separated from the solution after the reaction and further purified by column chromatography to obtain the desired PD-HMF-ether.

<Synthesis of PD-HMF-acetate>
In a dichloromethane solution (HMF acetate concentration: 0.1 mol / L) in which the HMF acetate compound obtained by the above method is dissolved, 0.01 molar equivalent of In (OTf) ₃ and an excess amount with respect to the HMF acetate compound. Trimethyl orthostate and 1,3-propanediol were added, and the solution was stirred at room temperature for 3 hours. The catalyst was separated from the solution after the reaction and further purified by column chromatography to obtain the desired PD-HMF-acetate.

<Synthesis of PD-FRL>
Proton beta zeolite (50 mg), furfural (0.1 mmol), and 1,3-propanediol (75 μL) were added to 2 mL of dichloromethane and stirred at room temperature for 3 hours. The solid catalyst was separated by filtration and then purified by column chromatography to obtain the desired PD-FRL.

[Example 1: Production of carboxylic acid ester from PD-HMF derived from biomass raw material]
As described below, PD-HMF was oxidatively esterified using a gold catalyst (Au / CeO ₂ ) supported on cerium oxide to produce a flange carboxylic acid ester.
The cerium oxide carrier was prepared by the liquid phase precipitation method. Specifically, the white precipitate formed by adding aqueous ammonia to pH = 10 in an aqueous solution in which cerium nitrate hexahydrate is dissolved is recovered by filtration and dried in an oven at 80 ° C. for about 10 hours. Was used as a cerium oxide carrier. Next, a 0.2 mol / L NaOH aqueous solution was added to a 160 mL aqueous solution in which gold chloride acid (manufactured by Wako Pure Chemical Industries, Ltd., 350 mg) was dissolved to adjust the pH to 10, and 4 g of cerium oxide was dispersed therein. A 50 mL aqueous solution was added, and a 0.2 mol / L NaOH aqueous solution was added again to adjust the pH of the aqueous solution to 10. The aqueous solution was stirred at room temperature for 24 hours, and then the solid recovered by filtration was repeatedly washed with distilled water until no chloride ions remained. The residual chloride ion was confirmed by the formation of a precipitate with an aqueous _{AgNO 3 solution.} The washed solid sample was dried in an oven at 80 ° C. for about 10 hours and used as _{Au / CeO 2.} The amount of Au carried by the catalyst was estimated by high frequency inductively coupled plasma emission spectroscopy (ICP-AES) and found to be 2.1 to 2.7% by mass.

As a substrate, 100 mg of PD-HMF obtained by the method of Experimental Example 7, 2 equivalents of Na ₂ CO ₃ , 1 mL of methanol, and _{50 mg of Au / CeO 2} described above were added to a pressure-resistant container, and oxygen gas was filled up to 5 atm. Then, the solution was heated and stirred at 120 ° C. for 15 hours. After the pressure-resistant container was rapidly cooled to room temperature, the substrate and product were qualitatively and quantified by ^{1 1 H NMR.} As a result, the flange carboxylic acid diester was produced in a high yield, and the product yield was 85%. It was confirmed that almost no solid by-products were produced in the reaction solution after the reaction was completed. In addition, no dirt deposits were found in the autoclave.

[Examples 2-1 to 2-7: Production of carboxylic acid from PD-HMF derived from biomass raw material]
As a substrate, PD-HMF obtained by the method of Experimental Example 7, a base, 5 mL of distilled water, and 1 equivalent of Au / CeO ₂ catalyst with respect to the substrate were added to a pressure resistant container, and oxygen gas was filled to 5 atm. Frangicarboxylic acid was produced by heating and stirring the solution at 130 ° C. for 15 hours. In Examples 2-1 to 2-7, as shown in Table 6, the base mass, the substrate concentration, the base used, and the amount of the base added thereof were changed. After the reaction, the pressure-resistant container was cooled to room temperature, and then the substrate and the product were qualitatively and quantified by ^{1 H NMR.} The results are shown in Table 6. In each system, it was confirmed that flange carboxylic acid (FDCA) was produced in a high yield, and that almost no solid by-products were produced in the reaction solution after the reaction was completed. In addition, no dirt deposits were found in the autoclave.

[Comparative Example 1: Production of Carboxylic Acid Ester from HMF Derived from Biomass Raw Material]
The reaction was carried out under the conditions described in Example 1 except that HMF (manufactured by Sigma-Aldrich) was used instead of PD-HMF. After the reaction, the pressure-resistant vessel was rapidly cooled to room temperature, and then the substrate and product were qualitatively and quantified by ^{1 1 H NMR.} The yield of the target product, the frangylcarboxylic acid methyl ester, was as low as 6%, and a large amount of solid by-products were produced in the reaction solution after the reaction was completed.

[Comparative Example 2: Production of Carboxylic Acid from HMF Derived from Biomass Raw Material]
The reaction was carried out under the conditions described in Example 2-1 except that HMF was used instead of PD-HMF _{and the reaction was carried out with respect to HMF in the presence of 2 equivalents of Na 2} CO _3. After cooling the pressure vessel to room temperature, the substrate and product were qualitatively and quantified by ^{1 1 H NMR.} The yield of the target product, flange carboxylic acid, was as low as 28%, and a large amount of solid by-products were produced in the reaction solution after the reaction was completed.

The carboxylic acid ester and carboxylic acid obtained by the present invention are industrially useful as resin raw materials such as polyester resins, and in particular, the flange carboxylic acid ester provides a resin having excellent heat resistance due to its furan skeleton. Therefore, its industrial value is extremely high.

Claims (13)

A method for producing a biomass material or Raka carboxylic acid ester or carboxylic acid, the carboxylic acid ester or carboxylic acid, furan carboxylic acid esters, furandicarboxylic acid esters, furan carboxylic acid, or flange carboxylic acid, furfural annular A method for producing a carboxylic acid ester or carboxylic acid, which comprises passing through acetal or cyclic acetal of hydroxymethylfurfural as an intermediate. The cyclic acetal of furfural or the cyclic acetal of hydroxymethylfurfural is 1,3-propanediol, ethylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,3, together with furfural or hydroxymethylfurfural. -Butanediol, 1,3-pentanediol, 1-phenyl-1,3-propanediol, 2-phenyl-1,3-propanediol, 1,2-propanediol, 1,2-butanediol, 1,2 The method for producing a carboxylic acid ester or carboxylic acid according to claim 1, wherein the cyclic acetal is produced by reacting with a diol selected from the group of -pentanediol, 1-phenyl-ethylene glycol, and catechol. Method for producing a carboxylic acid ester or carboxylic acid according to claim 1 or 2 by oxidation reactions of prior SL during body, characterized in that to produce the carboxylic acid ester or carboxylic acid. Before hear carboxylic acid esters or carboxylic acids, method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 3, characterized in that the flange-carboxylic acid ester or flange carboxylic acid. Method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 4, wherein the produced using a mixed solvent of the previous SL during body water and an organic solvent. The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 5 , wherein the biomass raw material is a saccharide raw material. The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 6 , which comprises a step of adding a diol to the reaction system. Furfural or method for producing a carboxylic acid ester or carboxylic acid according to claim 7, characterized in that to produce a pre-SL during body reaction with hydroxymethylfurfural and the diol. The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 3 to 8, wherein the oxidation reaction is carried out in the presence of a base. The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 3 to 9, wherein the oxidation reaction is carried out in the presence of water or a solvent containing 50% by volume or more of water. The carboxylic acid ester or carboxylic acid according to any one of claims 3 to 10, wherein the oxidation reaction is carried out in the presence of a solvent, and the mass ratio of the solvent to the intermediate is 1 or more and 50 or less. Method of producing acid. Circular acetals represented by the following formulas (1A) to (1D).

Method for producing a carboxylic acid having a carboxylic acid ester or furan skeleton having a furan skeleton cyclic acetals described as raw material in claim 12.

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