JP2018039778A - Production method of carboxylic acid ester or carboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of carboxylic acid ester or carboxylic acid, which can obtain carboxylic acid ester or carboxylic acid that is a target at a high yield while suppressing a side reaction and has excellent long term operation stability when producing the carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material.SOLUTION: When producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material, a production method of the carboxylic acid ester or carboxylic acid via a cyclic acetal intermediate is provided. The carboxylic acid ester or carboxylic acid having a furan skeleton is produced by producing the cyclic acetal intermediate and by undergoing its oxidation reaction step.SELECTED DRAWING: Figure 1

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 carboxylic acid ester or a carboxylic acid production method having a high yield and excellent long-term operational stability, and a furan having extremely excellent thermal stability, characterized by passing through a cyclic acetal intermediate. The present invention relates to a cyclic acetal having a skeleton.

  In recent years, countermeasures against the global environmental load problems such as fossil fuel depletion and increased carbon dioxide in the atmosphere are required. Due to such social demands, development of processes for producing various useful chemicals from biomass raw materials vegetated under the present global environment in the atmosphere has been attracting attention and has been vigorously pursued. The method of utilizing biomass raw materials as starting materials for chemical raw materials is, for example, made possible by the fact that plant raw material production can be dispersed and diversified in various places, so that the supply of raw materials is very stable and in the global environment of the atmosphere. Therefore, since the difference in the balance of carbon dioxide absorption and release is relatively balanced, there is the potential to have the feasibility of a recycling-oriented society including recycling that cannot be expected from fossil resource raw materials at all. The industrial utility value is extremely high.

Until now, as a technology for obtaining raw materials for chemicals as biomass raw materials, as a technology that greatly contributes to reducing CO ₂ emissions, biomass raw materials can be used as a raw material for general-purpose resins and as a raw material for the resins. Various techniques for guiding have been proposed. In addition, the development of a method for inducing from a biomass raw material to a high-functional chemical product by utilizing the structure of the biomass raw material is also active (Non-Patent Document 1).

  Biological conversion methods using biomass raw materials by fermentation, chemical conversion methods such as catalytic reactions, conversion methods using electrochemical methods, etc. have been developed as reactions to induce biomass materials into useful chemicals. . However, many of the technologies for substituting chemicals derived from these biomass raw materials with 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 therefrom generally contain a large amount of impurities such as nitrogen-containing compounds, sulfur-containing compounds, and metal salts that are specific to biomass raw materials. In addition, since it has many reactive functional groups such as a hydroxyl group and a carbonyl group, it is due to the fact that it tends to cause a side reaction during production. In other words, in a process in which biomass raw materials are applied as starting materials, the removal process of these impurities and by-products becomes essential, which complicates the manufacturing process and increases manufacturing costs as well as energy consumption during manufacturing. There are many problems in terms of economic efficiency and environmental impact.

  Therefore, in the derivatization reaction from the biomass raw material which is the subject of the present invention, it is required how efficient a conversion reaction process can be designed. Among the above conversion reactions, chemical conversion using a catalytic reaction in particular is required. The method is drawing 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 that derive useful chemicals from biomass raw materials, processes that involve compounds having a furan ring are particularly important from the viewpoints of functionality, versatility of use, environmental impact, and economic efficiency. Proposed as a process. For example, furandicarboxylic 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, Patent Document 4 proposes a method for producing hydroxymethylfurfural (HMF) from monosaccharides such as glucose and fructose in the presence of hydrous niobic acid. In addition, Patent Documents 5 and 6 and Non-Patent Document 2 have proposed a method for producing furandicarboxylic acid or an ester thereof by oxidation reaction of HMF.

  However, in the reaction for producing furandicarboxylic acid or its ester from the above biomass resources via HMF, HMF having reactive functional groups such as aldehyde group and hydroxyl group becomes an intermediate, and the heat of this reactive intermediate Due to the poor stability, HMF polymerization and ring-opening reaction proceed, and not only the reaction yield decreases due to the formation of oligomers such as humin and polymers and levulinic acid, but also by-produced oligomers and When the polymer adheres to the reactor or the pipe, there is a problem that the heat conduction efficiency of the reactor is reduced and the pipe is blocked, and stable long-term operation becomes difficult. In addition, these by-products are generally colored products, which are mixed in the product to cause coloration of the product, and further, by mixing these by-products into the product, the durability stability of the product is deteriorated. There is also a problem that this also leads to the generation of foreign matter inside. These are particularly prominent in the production of furandicarboxylic acid and esters thereof by increasing the concentration of HMF, and are a major issue in industrial processes that require economic efficiency during production. In other words, in industrial manufacturing processes, how to achieve long-term stable operation of manufacturing processes under high concentration conditions is an important issue in economic process design. The actual situation is that the manufacturing process of this chemical product that utilizes the above has not yet been solved. Therefore, in production processes that require raw materials for biomass, not only efficient conversion reaction processes with improved reaction yields, but also reaction process designs that improve the thermal stability and reaction stability of reaction intermediates. Has become an issue.

International Publication WO2011 / 036955 Japanese Patent No. 5894387 Japanese Patent No. 5823756 JP 2009-215172 A Japanese Patent No. 5217142 International Publication 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, In addition to being able to obtain the desired carboxylic acid ester or carboxylic acid in a high yield by suppressing side reactions, a method for producing a carboxylic acid ester or carboxylic acid that is excellent in long-term operational stability and intermediates thereof An object of the present invention is to provide a cyclic acetal having a significantly improved thermal stability.

As a result of intensive studies to solve the above problems, the present inventors have produced a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material by passing through a cyclic acetal intermediate, thereby The present inventors have found that the problem can be solved and have completed the present invention.
That is, the gist of the present invention resides in the following [1] to [9].

[1] In the method for 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, which passes through a cyclic acetal intermediate.

[2] The method for producing a carboxylic acid ester or carboxylic acid according to [1], wherein the carboxylic acid ester or carboxylic acid having the furan skeleton is produced by an 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 furan dicarboxylic acid ester or a furan dicarboxylic 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], comprising 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 generated by a reaction between an aldehyde having a furan skeleton and the diol.

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

(In the formula, R ¹ is a group represented by a hydrogen atom, —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. Group or an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent.)

[9] A method for producing a carboxylic acid ester or carboxylic acid, comprising producing a furan carboxylate 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. Thus, 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 product quality deterioration due to contamination of by-products, piping clogging due to by-product polymers, and reduction in heat transfer efficiency, and continuous production of carboxylic acid esters or carboxylic acids. Can be performed stably and efficiently. Furthermore, coloring of products derived from these carboxylic acid esters and carboxylic acids as raw materials and generation of foreign substances can be suppressed.

6 is a graph showing the results of Experimental Example 1.

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

In the present invention, unless otherwise specified, “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 “oxidative esterification” and “oxidation” are collectively referred to as “oxidation reaction”.
In the present invention, “equivalent” means molar equivalent.

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

  In the following, the present invention will be described mainly by illustrating the case where a furan carboxylate or furan carboxylate is produced as a carboxylic acid ester having a furan skeleton or a carboxylic acid according to the present invention. The production method of furan carboxylic acid ester or furan carboxylic acid is not limited at all, and can be effectively applied to the production of furan monocarboxylic acid ester or furan monocarboxylic acid, for example. For example, when producing furan monocarboxylic acid ester or furan monocarboxylic acid, in the production of furandicarboxylic acid ester or furandicarboxylic acid described below, a biomass raw material containing a saccharide unit having 6 carbon atoms as a main component, or A raw material containing a saccharide having 6 carbon atoms produced from a biomass raw material through a saccharification step (hereinafter, “raw material containing saccharide” is referred to as “saccharide raw material”), and a biomass raw material containing a saccharide unit having 5 carbon atoms. Alternatively, furan monocarboxylic acid ester or furan monocarboxylic acid can be produced by changing to a saccharide raw material. Moreover, furan monocarboxylic acid ester or furan monocarboxylic 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 for producing a carboxylic acid having a furan skeleton via an aldehyde intermediate having a furan skeleton produced by a dehydration reaction from a saccharide raw material derived from a biomass raw material and / or a biomass raw material, It has been found that the above various problems occur due to the poor thermal stability of the aldehyde intermediate. Accordingly, the present inventors have repeatedly studied to solve these problems, and furfural (hereinafter abbreviated as “FRL”) produced by a dehydration reaction, hydroxymethylfurfural (hereinafter abbreviated as “HMF”), and the like. The aldehyde intermediate is immediately converted into a cyclic acetal by reaction with a diol, preferably acetalized simultaneously with the formation of a furan skeleton by a dehydration reaction, to obtain a cyclic acetal intermediate having high thermal stability. It has been found that the above various problems can be solved by producing a carboxylic acid ester or a carboxylic acid by an oxidation reaction. Moreover, the carboxylic acid made into the objective in this invention can be manufactured also by hydrolyzing the carboxylic acid ester manufactured through the said process.

  Hereinafter, the case where the aldehyde having a furan skeleton is HMF (the above reaction formula (A)) 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. In order to achieve this, a 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 preferred diol, and the thermal stability of the formed acetal is remarkably improved. -Propanediol (1,3-PD) is particularly preferred.

  Specifically, by making 1,3-propanediol (1,3-PD) or ethylene glycol (EG) exist in the dehydration reaction system, as shown in the following reaction formula, the HMF produced by the dehydration reaction is And immediately reacting with 1,3-propanediol (1,3-PD) or ethylene glycol (EG), and 1,3-propanediol acetalized product of HMF (hereinafter abbreviated as “PD-HMF”) or HMF. Into an ethylene glycol acetalized product (hereinafter abbreviated as “EG-HMF”).

As shown in Experimental Example 1 described later, since these cyclic acetals are superior in thermal stability compared to HMF, by passing through such a cyclic acetal intermediate,
(1) Oligomer and polymer formation due to HMF polymerization is suppressed.
(2) From the above (1), the reaction yield can be kept high.
(3) From (1) above, it is difficult for dirt caused by by-products to adhere to the reactor and piping, and troubles such as a decrease in thermal conductivity and blockage in the piping can be prevented and stable production can be achieved. Furthermore, it is possible to obtain a high-quality product by preventing the occurrence of coloring and foreign matters due to by-products.
Such an effect is produced.

  When HMF is cyclic acetalized, a diol may be added to the reaction system as described above. Furthermore, the cyclic acetal produced by the reaction between the diol added to the reaction system and 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 follows. Converted to a diester of furandicarboxylic acid.

  In addition, since the cyclic acetal of the present invention is stable even in water under basic conditions, as another aspect, oxidation is performed in an oxidizing reaction atmosphere containing oxygen gas or the like in the presence of a base as follows. , Converted to furandicarboxylic acid.

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

  In the above-mentioned Non-Patent Document 2, a methanol acetalization product of HMF (hereinafter abbreviated as “Me-HMF”) is produced as a by-product in the production of furan carboxylic acid dimethyl ester, which is immediately intended. However, as shown in Experimental Example 1 described later, an acetalized product of HMF, which is not a cyclic acetal, is inferior in thermal stability. The object of the invention cannot be achieved.

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

[Biomass raw material]
Biomass raw material in the present invention refers to a plant in which solar light energy is converted and stored in a form such as starch, cellulose, hemicellulose, etc. by the photosynthesis of plants, the body of animals that grow by eating plants, Includes products made from processed animals. Examples of biomass raw materials include 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 stover, corn fiber , Tapioca, bagasse, vegetable oil residue, persimmon, buckwheat, soybean, oil and fat, waste paper, papermaking residue, marine product residue, livestock excrement, sewage sludge, food waste and the like. Among them, wood, rice straw, rice husk, rice bran, old rice, corn, sugar cane, cassava, sago palm, cardon, switch grass, pine wood, poplar wood, maple wood, okara, corn cob, corn stover, corn fiber, tapioca, bagasse, Plant resources such as vegetable oil residue, persimmon, buckwheat, soybean, waste paper, papermaking residue are preferred, more preferably wood, rice straw, rice husk, old rice, corn, sugar cane, cassava, sago palm, cardon, switchgrass, pinewood, poplar Wood, maple wood, corn cob, corn stover, corn fiber, bagasse, straw, waste paper, papermaking residue, most preferably corn, sugar cane, cassava, sago palm, bagasse, cardon, switchgrass, pine wood, poplar wood, maple wood , Corn cob, corn stover, corn Is Aiba.

  In the present invention, for example, by using a known technique such as Green Chemisry 16 (2014) 4816-4838 and the literatures cited therein, these biomass raw materials are directly induced into FRL and HMF, and then the FRL In addition, the method of inducing the cyclic acetal by the reaction of the HMF and the diol is a preferable embodiment because it does not require a saccharification process from a biomass raw material and the number of reaction steps to the final target product is reduced. Alternatively, a biomass raw material and a diol may be allowed to coexist and be directly induced into a cyclic acetal form of FRL or HMF using this technique. From the viewpoint that the number of reaction steps is small and the reaction process is efficient, the latter method is preferred in which a biomass raw material and a diol coexist to directly obtain a cyclic acetal.

[Saccharification]
In the present invention, there is no particular limitation other than the method of directly deriving from the above biomass raw material to FRL, HMF, and their cyclic acetals, 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 processes such as biological treatment and physical treatment, polysaccharides contained in biomass raw materials are decomposed (saccharified) into saccharides, which are constituent units, and then oligosaccharides, disaccharides and monosaccharides. A method of obtaining a cyclic acetal form by obtaining FRL or HMF from the sugar liquid and reacting with a diol as described above can be suitably 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 body due to foreign matters and impurities contained in the biomass raw material.

  The method for saccharification of the biomass raw material is not particularly limited, and for example, known methods such as Green Chemisry 16 (2014) 4816-4838 and the literatures cited therein can be used.

  The process is not particularly limited, but usually includes a refinement process by pretreatment such as chipping, scraping, or crushing biomass raw material. If necessary, a grinding process by a grinder or a mill is further included. The refined biomass raw material is further subjected to a pretreatment and saccharification step to produce a saccharose. Specific methods include acid treatment with a strong acid such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, and alkali treatment. , Chemical methods such as ammonia freezing steam explosion method, solvent extraction, subcritical fluid treatment, supercritical fluid treatment, oxidant treatment, and physical methods such as fine grinding, steam explosion method, microwave treatment, electron beam irradiation, Biological treatment such as hydrolysis by microorganisms or enzyme treatment, or a combination thereof.

  As sugars derived from the above biomass raw materials, usually hexoses such as glucose, mannose, galactose, fructose, sorbose, tagatose, pentoses such as arabinose, xylose, ribose, xylulose, ribulose, pentose, xylan, saccharose, starch, Disaccharides such as cellulose, oligosaccharides and polysaccharides are used, and among these, glucose, fructose and xylose are preferable. Among these, fructose and xylose are particularly preferable because of high reaction yield. On the other hand, cellulose and hemicellulose are preferable as the saccharide derived from the plant resource in a broader sense.

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

The total concentration of saccharides 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. 1% by mass or more, preferably 3% by mass or more, more preferably 5% by mass or more. On the other hand, the upper limit is usually preferably 60% by mass or less, and more preferably 50% by mass or less. This sugar solution may be used for the next step as it is, and, if necessary, a method of distilling off water under reduced pressure, a method of distilling off water by heating, or the nanostructure described in International Publication WO2010 / 067875. Using a method of filtering through a filtration membrane and / or a reverse osmosis membrane, etc., a concentrated sugar solution in which the sugar component is concentrated may be obtained and used for the next step. In particular, the method of concentrating the sugar solution is preferable in terms of improving the productivity of the entire process in the subsequent dehydration reaction and acetalization reaction.

  In addition, as another means, a method of separating monosaccharides such as glucose, fructose, xylose and the like from a sugar solution using a known method, and supplying the separated monosaccharide to the next step reduces the amount of impurities in the raw material. This makes it possible to improve the reaction yield of the subsequent reaction process and to reduce the amount of fluctuation between lots, and is the most preferable aspect in that stable long-term operation is possible. These monosaccharides are currently available on an industrial scale. In the present invention, an isolated monosaccharide may be additionally added in order to obtain a sugar solution having a high sugar component content.

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

  In addition, 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 the biomass raw material and / or a saccharide raw material, and FRL and / or HMF The cyclic acetal body may be produced through two steps (hereinafter referred to as “two-stage method”), and FRL and / or HMF produced from the biomass raw material and / or saccharide raw material You may carry out by 1 process so that it may convert into a cyclic acetal body immediately (this method is hereafter called a "one-step method"). That is, in the presence of a diol for cyclic acetalization 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 a dehydration reaction from biomass raw material or saccharide raw material By allowing the diol for cyclic acetalization to be present in the reaction system for producing FRL and / or HMF to be produced, a cyclic acetal intermediate having high thermal stability can be formed in the same reaction system. As a result, not only the reaction yield of the intermediate is improved, but it is also possible to reduce the production of by-products such as colored products and polymerized products, which is industrially advantageous in that mixing into these products is suppressed. It becomes a manufacturing process. In particular, the effect of the present invention becomes remarkable by adopting a production process via an HMF acetal intermediate.

  In the case of producing a cyclic acetal intermediate by a two-stage method, the once produced FRL and / or HMF is isolated and / or purified (hereinafter referred to as “isolation / purification”) in a separate reaction vessel. Cyclic acetalization may be performed, and 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 saccharide raw material, and further its cyclic acetal body, is preferably carried out in a solvent in the presence of a catalyst. The catalyst is not particularly limited as long as it can produce FRL or HMF from a biomass raw material or a saccharide raw material, and further a cyclic acetal product thereof. Usually, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boron Inorganic acids such as acids and metal salts such as alkali metals or alkaline earth metals thereof, sulfonic acids such as p-toluenesulfonic acid and metal salts such as alkali metals and alkaline earth metals thereof, amberlist, amberlite, Acid cation exchange resin such as diamond ion, 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 -W _{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 2 or the like of a metal oxide, metal Examples include composite oxides, clays, sulfuric acid immobilization catalysts such as sulfated ZrO ₂ , phosphoric acid immobilization catalysts such as titania and niobium treated with phosphoric acid, and heteropolyacids.

  In addition, aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, caproic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, aconitic acid, itaconic acid , Oxaloacetic acid, fumaric acid, maleic acid, cyclopentanedicarboxylic acid, aliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid, aliphatic tricarboxylic acid such as cyclohexanetricarboxylic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, Aromatic acids such as trimellitic acid, hemimellitic acid, merophanic acid, prenitic acid, pyromellitic acid, benzenepentacarboxylic acid, melittic acid, organic acids such as hydroxycarboxylic acid such as lactic acid, malic acid, citric acid, tartaric acid, and Neutralized at least part of these organic acids Alkali metal or salts of alkaline earth metals and the like can also be used as catalysts.

In the present invention, among the above catalysts, it is preferable to carry out the reaction in a heterogeneous system using a solid catalyst insoluble in the reaction solvent in terms of easy continuous flow reaction and high reaction selectivity. Specifically, among the above catalysts, acidic cation exchange resins such as amberlist, amberlite, diamond ion, zeolite, Nb ₂ O ₅ , YNbO ₄ , Ta ₂ O ₅ , 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 or the like of a metal oxide, metal composite oxide, clay, sulfated A sulfuric acid immobilization catalyst such as ZrO ₂ and a phosphoric acid immobilization catalyst such as titania or niobium treated with phosphoric acid are preferred. Among them, in terms of selectively advancing only acetalization reaction of HMF, _zeolite, is _{Nb 2 O 5, Nb 2 O} 5 -WO 3, Nb 2 O 5 -MoO 3 more preferred, zeolites, _Nb 2 O ₅ is preferred.

  These catalysts may be used alone or in combination of two or more. When two or more types of catalysts are used, the combination is not particularly limited, and each metal has catalytic activity (co-catalyst), but can improve the catalytic activity of one or more types of metal (co-catalyst). May be.

  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 saccharide raw material when the catalyst is soluble in a solvent. 0.01 mass% or more, more preferably 0.05 mass% or more, while the upper limit is 50 mass% or less, preferably 30 mass% or less, more preferably 20 mass% or less, and even more preferably 10 mass% or less. It is. On the other hand, this is not the case when a continuous reaction is performed in a fixed bed reactor or suspension bed reactor using a solid catalyst insoluble in the reaction solvent.

  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. There is a case. Depending on the selection of the organic solvent, the reaction can be carried out with a homogeneous mixed solvent, but the polymerization and decomposition reaction of the produced FRL and HMF or their cyclic acetal bodies are suppressed, and the yield of the cyclic acetal bodies is improved. It may be preferable to use an organic solvent that is a two-layer system of an aqueous layer and an organic layer. That is, by using this technique, it is possible to carry out a continuous extraction reaction in which the produced FRL, HMF, or cyclic acetal product thereof is extracted into an organic solvent. Can be efficiently separated from the organic solvent layer.

  The organic solvent to be used is not particularly limited as long as it does not inhibit the generated FRL, HMF, and their acetalization reaction. 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 ~ 20 ethers; 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclohexanone, 4-methyl Til-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- C4-C20 ketones such as heptadecanone, 3-octadecanone, acetophenone; esters such as ethyl acetate, propyl acetate, butyl acetate; methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol 2-methyl- -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-heptadeca Nord, 1-octadecanol, 16-methylheptadecen-1-ol Monoalcohols having 1 to 20 carbon atoms such as nonadecyl alcohol and arachidyl alcohol; phenols having 6 to 12 carbon atoms such as phenol, methylphenol, ethylphenol, propylphenol and butylphenol; pentane, hexane, cyclohexane, heptane, C3-C12 saturated aliphatic hydrocarbon compounds such as octane, nonane, decane, dodecane, isododecane; aromatics such as toluene, xylene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene, 1-methylnaphthalene Hydrocarbons; Lactones such as γ-butyrolactone and γ-valerolactone; Halogenated hydrocarbons such as dichloromethane, chloroform, dichloroethane, tetrachloroethane, and hexachloroethane; Others, dimethylacetamide, N, N-di Tylformamide, N-methylmorpholine, N-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphoric triamide, tetramethylurea, dimethyl sulfoxide, sulfolane, isosorbide, isosorbide dimethyl ether, propylene carbonate And mixtures thereof. In addition, 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; Ionicity such as 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; A liquid may be used.

  Among these, the organic solvent is preferably selected from at least one of the group consisting of ether, ketone, ester, alcohol, phenol, lactone, aromatic hydrocarbon, halogenated hydrocarbon, and saturated aliphatic hydrocarbon. . Among these, it is preferably selected from at least one of the group consisting of ethers, ketones, esters, alcohols, phenols, lactones, aromatic hydrocarbons, and saturated aliphatic hydrocarbons because of its low environmental impact. .

  In addition, when the reaction is performed in a two-layer system, methyl ethyl ketone, methyl isobutyl ketone, acetophenone, cyclohexanone, 1-butanol, and the like, in that the extraction efficiency of the cyclic acetal body is high and the amount of the organic solvent dissolved in water is small. 2-butanol, 1-pentanol, 1-hexanol, propylphenol, butylphenol, butylphenol, toluene, xylene, trimethylbenzene, 1,2,3,4-tetrahydronaphthalene, 1-methylnaphthalene, cyclohexane and isododecane are preferred. Of these, methyl ethyl ketone, methyl isobutyl ketone, butylphenol, cyclohexanone and toluene are particularly preferred. These organic solvents are preferably used alone in consideration of solvent recovery / reuse, but two or more of them may be used.

  In the present invention, the amount of the organic solvent used in the case of 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, the content is preferably 10 to 1000% by mass. When the amount of the organic solvent used is less than the above range, polymerization and decomposition reaction of the generated FRL, HMF, or cyclic acetal thereof tends to occur, and the yield of the acetal intermediate tends to decrease accordingly. If the amount is too large, it is necessary to remove a large amount of the organic solvent when recovering the produced cyclic acetal intermediate, which reduces the recovery efficiency, complicates the process, and makes the reaction equipment larger and economical. Tend to be disadvantageous.

  Therefore, when a sugar solution is used as the saccharide raw material, it is preferable to add an organic solvent or water and an organic solvent so that the above range is satisfied with respect to the water in the sugar solution.

  The diol added for the cyclic acetalization of HMF (hereinafter sometimes referred to as “cyclic acetalization diol”) is appropriately determined according to the type of cyclic acetal intermediate to be produced, and is used for the production of PD-HMF. A diol capable of forming an acetal having a 6-membered ring skeleton is used, and a diol capable of forming an acetal having a 5-membered ring skeleton is used for the production of EG-HMF. Specifically, 1,3-propanediol is exemplified as a representative example for the production of PD-HMF, and ethylene glycol is exemplified as a typical example for the production of EG-HMF, but is not limited thereto. 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 which may have an alkyl substituent 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. Two or more kinds of these diols for cyclic acetalization can be used, but usually one kind is used. In the present invention, the above diol is used as a reaction reagent as a cyclic acetalizing agent, but the diol can also be used as the above organic solvent. Therefore, the technique of using a diol as a solvent and acetalizing agent is one preferred embodiment.

  The amount of the biomass raw material and / or 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 in a homogeneous system, the lower limit of the concentration of the raw material relative to the reaction solvent is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass. As mentioned above, More preferably, it is 10 mass% or more, Most preferably, it is 15 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. If the raw material concentration is not less than the above lower limit value, the separation efficiency between the cyclic acetal intermediate and the solvent tends to be high, and if the raw material concentration is not more than the above upper limit value, side reactions can be suppressed and the yield of the cyclic acetal body can be increased. It tends to be high, which is preferable. In the case of the two-stage method, the concentration of the raw material in the reaction solution when the reaction is carried out in a homogeneous system is the solvent used for the reaction (in the case of using a sugar solution, including water in the sugar solution), the catalyst, It is the ratio of the raw material to the total with the raw material, and in the case of the one-stage method, it is the ratio of the raw material to the total with the above-mentioned cyclic acetalization diol added.

  In the case of the two-stage method, the reaction temperature of the dehydration reaction to obtain HMF is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and preferably 250 ° C. or lower, more preferably 230 ° C. or lower. It is. When the reaction temperature is equal to or higher than the above lower limit, the progress of the reaction tends to be accelerated, and the productivity of the product is improved. It is preferable for the reaction temperature to be equal to or lower than the above upper limit value because it tends to suppress the decomposition and polymerization of the product and the reaction intermediate and improve the yield of the product. In the case of the two-stage method, after the FRL and HMF are produced by the 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 product of FRL or HMF. The above-mentioned diol for cyclic acetalization used for cyclic acetalization may be equal to or higher than the expected FRL or HMF production equivalent, and is usually used in an amount of 1 to 10 equivalents relative to the expected production of FRL or HMF. The diol for cyclic acetalization is not particularly limited when used as a solvent. The reaction during the cyclic acetalization is preferably performed at a temperature of 10 to 150 ° C.

  In the case of the one-stage 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 ranges, and further the above-mentioned cyclic acetalization diol. The reaction temperature is usually 100 ° C. or higher, preferably 120 ° C. or higher, while the upper limit of the reaction temperature is 1 to 10 equivalents to the amount of FRL or HMF produced. The dehydration and cyclic acetalization reactions are preferably carried out usually at 250 ° C. or lower, preferably 230 ° C. or lower.

  In this way, the reaction solution in which the cyclic acetal intermediate is produced by the two-stage method or the one-stage method is used as it is in the presence of oxidative esterification in the presence of alcohol or in the presence of water according to the following target product. You may use for an oxidation process, and after isolating / purifying the produced | generated cyclic acetal intermediate body, you may use for this oxidative esterification process or this oxidation process.

[Oxidative esterification and oxidation]
In the present invention, a carboxylic acid ester or a carboxylic acid is produced by oxidative esterification or oxidation, respectively, through a dehydration / cyclic acetalization step from a biomass raw material and / or a saccharide raw material.
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 metals or metal compounds having an oxidizing ability. Periodic table Group 8-10 metals such as platinum, palladium, nickel, iron, ruthenium, cobalt and their compounds, Group 11 metals and their compounds such as copper, silver, gold, etc., Group 12 of the periodic table such as zinc Metals and compounds thereof, periodic table group 13 metals and compounds such as indium, periodic table group 14 metals and compounds such as tin and lead, periodic table group 7 metals and compounds such as manganese and rhenium, chromium, Periodic table Group 6 metals and compounds such as molybdenum, periodic table Group 5 metals and compounds such as niobium and tantalum, periodic table Group 4 metals such as zirconium and the like Periodic table group 3 metals such as scandium and compounds thereof, magnesium, calcium and other periodic table group 2 metals and compounds thereof, periodic table group 1 metals such as cesium and compounds thereof, and mixtures of these metals (Including alloys). In particular, metals in Group 6 to 12 of the periodic table and compounds thereof and mixtures thereof (including alloys) are preferable, and metals and compounds in Groups 7 to 11 of the periodic table are more preferable, and among them, platinum, palladium, rhenium are particularly preferable. Magnesium, copper, silver, gold, zinc, manganese, cobalt and their compounds are preferred, and platinum, palladium, rhenium, copper, silver, gold, cobalt, manganese and their compounds are most preferably used. Examples of the compound include oxides of these metals, alkoxy compounds, alkyl compounds, organic acid salts, and the like, and metal elements and metal oxides are preferable. These metal catalysts are preferably used as metal-supported 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. Among these, carbon, titania, and ceria are preferable in terms of ease of preparation of the catalyst and activity. These catalysts may be used alone or in combination of two or more, or may be added later.

  Metal supported catalysts include gold / carbon, gold / titania, gold / zirconia, gold / ceria, platinum / carbon, platinum / titania, platinum / ceria, palladium / carbon, palladium / silica, palladium / alumina, rhenium / carbon, Rhenium / silica, rhenium / alumina, cobalt / carbon, cobalt / titania, cobalt / ceria are preferred, gold / carbon, gold / titania, gold / zirconia, gold / ceria, platinum / carbon, palladium / carbon, palladium / silica, Rhenium / carbon, rhenium / silica, cobalt / carbon, cobalt / titania, and cobalt / ceria are more preferable, and gold / titania, gold / zirconia, gold / ceria, and cobalt / carbon have high reaction activity, and metals after use. It is particularly preferable in that it can be easily recovered.

  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 conversion amount with respect to the raw material. The lower limit of the amount of the oxidative esterification catalyst or the oxidation catalyst used is more preferably 0.02 mass ppm, more preferably 0.2 mass ppm, more preferably 2 mass ppm, as a metal conversion amount relative to the raw material. Most preferred. The upper limit of the amount of the oxidative esterification catalyst or oxidation catalyst used is more preferably 50000 mass ppm in terms of metal relative to the raw material, more preferably 20000 mass ppm, and most preferably 10000 mass ppm. If the amount of the catalyst used is less than 0.002 mass ppm, the reaction time is excessively inefficient, and if it is more than 100,000 ppm, the cost for the catalyst becomes high and uneconomical. This is disadvantageous in that it becomes large and the product is easily colored.

  In the oxidation reaction of HMF or FRL cyclic acetal, the presence of a base improves the stability of the cyclic acetal and can suppress side reactions such as polymerization of the reaction intermediate and ring-opening reaction. Since the yield of carboxylic acid ester or carboxylic acid may be improved, the oxidation reaction may be performed in the presence of a base. Examples of such bases include inorganic bases such as sodium hydroxide, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, potassium carbonate, and potassium hydrogen carbonate, and organic bases such as triethylamine. Of these, inorganic bases are preferred for good reasons.

  The amount of the base used in the oxidation reaction in the presence of a base is not particularly limited, but the lower limit is 0.01 equivalents or more, preferably 0.1 equivalents or more with respect to the cyclic acetal of HMF or FRL. The upper limit is 10 equivalents or less, preferably 5 equivalents or less, more preferably 3 equivalents or less. By adopting such a use amount, the stability of the cyclic acetal can be improved and side reactions such as polymerization of the reaction intermediate and ring-opening reaction can be suppressed, and the target carboxylic acid ester or carboxylic acid can be prevented. The yield can be improved.

  In the oxidation reaction of HMF or FRL cyclic acetal, when the reaction is carried out in the presence of a metal catalyst, the reaction is carried out while allowing a gas to flow 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, inorganic peroxide, oxygen-containing gas, etc., but oxygen-containing gas such as gaseous oxygen or air that does not require separation and purification after the reaction is used. It is preferable that the oxygen-containing gas be passed through 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 particularly preferably pure oxygen (99% or more). Although oxygen may be introduced into the gas phase or blown into the reaction solution, it is more preferred to blow it into the reaction layer.

  The reaction temperature for carrying out the oxidation reaction of the cyclic acetal is preferably from room temperature to 200 ° C., 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, further preferably 150 ° C, and most preferably 130 ° C. If the reaction temperature is too low, a reaction time is required for a long time, and if the reaction temperature is too high, the reaction becomes so intense that it becomes difficult to control or causes coloring, which is not preferable.

  The time during which the oxygen-containing gas is circulated 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 10 hours, more preferably 1 to 5 hours. If this time is too short, the reaction is too intense and it is difficult to control the reaction temperature, and if it is too long, the production cost increases, which is not preferable. In addition, when performing an oxidation reaction continuously, reaction time is not this limitation.

  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 1 L / min. If this time is too slow, the reaction rate is slow, the production efficiency is poor and the production cost is high, which is not preferable. On the other hand, if the speed is too high, the consumption efficiency of oxygen is poor and the amount of oxygen used increases, resulting in an increase in cost.

Further, examples of the flow method include a method of blowing into the liquid layer of the reactor, a method of blowing into the gas 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 circulated continuously or intermittently, but is preferably a method of continually flowing. When intermittently circulating, it is preferable to prepare the interval of intermittent circulation so as not to be too long so that oxygen is not insufficient.
Further, the oxygen-containing gas may be supplied into the reaction vessel so as to be pressurized, and the oxidation reaction may be performed. 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, Particularly preferably, it is 1 MPa or less. In general, increasing the reaction pressure is preferable because the reaction rate is improved. On the other hand, in order to carry out the reaction at a high reaction pressure, equipment such as a reactor having a particularly high pressure resistance is required, as well as oxidation. The side reaction may become remarkable due to the increased ability.

The reaction solvent in the oxidative esterification is not particularly limited as long as it is a solvent that dissolves the raw material cyclic acetal, and the same reaction solvent as in the above-described dehydration / cyclic acetalization or the above-mentioned diol can be used. . When the oxidative esterification is carried out after isolating the cyclic acetal intermediate, the solvent is not necessarily a mixed solvent, and a single solvent of alcohol such as monoalcohol or diol may be used.
The reaction solvent in the oxidation is not particularly limited as long as it contains water that dissolves the raw material cyclic acetal, and the above-mentioned mixed solvent of reaction solvent and water in the dehydration / cyclic acetalization described above and the above-described diol and water. A mixed solvent or a water solvent can be used. When the oxidation is carried out after isolating the cyclic acetal intermediate, the solvent is not necessarily a mixed solvent, and an aqueous solvent may be used. Here, the content of water when using a mixed solvent with water is not particularly limited as long as it is 1 equivalent or more with respect to the cyclic acetal intermediate, but as a volume ratio, the lower limit is usually 1% by volume or more. Preferably, it is 10 volume% or more, More preferably, it is 50 volume% or more, and there is no restriction | limiting in an upper limit.

  The amount of the reaction solvent used is not particularly limited, but the lower limit is usually 1 or more, preferably 2 or more, more preferably 3 or more, and still more preferably 4 times in terms of mass ratio with respect to the raw material cyclic acetal. Above, 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. When the amount of the solvent used is too large, the reaction vessel becomes too large, which is not preferable as an industrial process in which production efficiency is lowered and 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 undesirable. However, the acetal intermediate of the present invention is excellent in thermal stability and polymerization stability, and in the oxidation reaction, it has a feature that oligomers such as humin and polymers, levulinic acid and the like are hardly generated even under high concentration conditions. It is possible to produce carboxylic acid esters and carboxylic acids under reduced solvent usage, that is, under higher concentration conditions.

  In the present invention, when the cyclic acetal intermediate is oxidatively esterified, an alcohol ester of furandicarboxylic acid is produced by the presence of alcohol in the reaction system. If the coexisting alcohol is a cyclic acetalization diol added in the dehydration / cyclic acetalization step in the previous step, as described above, a hydroxyalkyl ester of furandicarboxylic acid is produced, but the monool is not a diol. If it coexists, an alkyl ester of furandicarboxylic acid can be produced. In addition, 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 furandicarboxylic acid may be produced, and if it is less than 2 equivalents, a monoester may be produced.

  In the carboxylic acid ester production method of the present invention, preferably, the oxidative esterification step is performed subsequent to the above-described dehydration / cyclic acetalization step. In many cases, it is an unreacted residue of the cyclic acetalization diol added for the cyclic acetalization reaction. In this case, a hydroxyalkyl ester of furandicarboxylic acid is formed.

  When the cyclic acetal intermediate is isolated / purified after the dehydration / cyclic acetalization step and oxidative esterification is newly performed on the cyclic acetal intermediate in the presence of an alcohol, The diol for cyclic acetalization is not limited to the above-mentioned diol for cyclic acetalization, but is 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-octane Nord, 2-ethyl-1-hexanol, 1-nonanol, 1-decanol, 1-undecyl alcohol, 1-lauryl alcohol, 1-tridecyl alcohol, 1-tetradecanol, 1-pentadecyl alcohol, 1-hexa 1 to 20 carbon atoms such as decanol, cis-9-hexadecen-1-ol, 1-heptadecanol, 1-octadecanol, 16-methylheptadecen-1-ol, nonadecyl alcohol, arachidyl alcohol, etc. It may be an aliphatic diol having 4 to 8 carbon atoms such as aliphatic monoalcohol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol and the like.

  In oxidative esterification or oxidation, the reaction solution is preferably stirred in order to increase the contact efficiency between the raw material, the catalyst and oxygen. Stirring can be used as long as it is a stirrer used for a normal reaction such as a magnetic stirrer, a mechanical stirrer, a stirrer motor provided with a stirrer blade, or the like. When the scale becomes large, a stirring motor having a stirring blade is used in terms of power. Stirring is preferably started before the reaction is performed, the stirring is continuously performed during the reaction, and the stirring is preferably performed while the reaction liquid after cooling is cooled.

  In the present invention, the carboxylic acid ester having a furan skeleton derived as described above is derived into furan monocarboxylic acid and furandicarboxylic acid as follows by hydrolysis in the presence of an acid catalyst. You can also.

[Product recovery method]
After completion of the reaction, the product obtained in each of the above steps may be recovered by isolation and / or purification, or used as a raw material for the next step without passing through the isolation and / or purification step. May be.

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

On the other hand, when isolating / purifying the product obtained in each step, depending on the physical properties of the product, the solvent distillation method, the method of extracting with an organic solvent after solvent removal, the distillation method, The product can be recovered by a sublimation technique, a crystallization technique, or a chromatographic technique. Here, for example, when a carboxylic acid is obtained by oxidation of a cyclic acetal in the presence of a base, the product carboxylate is treated with a mineral acid such as hydrochloric acid or sulfuric acid to obtain a carboxylic acid, and then the recovery method is used. Can be used to isolate / purify the carboxylic acid.
Among these, in particular, when the product is liquid under the handling temperature condition, a method of recovering the product while purifying it by a distillation technique 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 technique is preferred. At that time, the method of purifying the obtained solid product by washing is a preferred embodiment.

[Cyclic acetal]
A particularly preferred cyclic acetal in the present invention is a 1,3-propanediol acetalized product of FRL or HMF represented by the following formula (2) (hereinafter sometimes referred to as “cyclic acetal (2)”), which is described above. In the dehydration and cyclic acetalization, 1,3-propanediol is used as the cyclic acetalization diol.

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

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

Furthermore, when this cyclic acetal (2) is a —CH ₂ OH group, the hydroxyl group is converted to a carboxylic acid anhydride ((R ² CO) ₂ O (R ² is an alkyl group having 1 to 6 carbon atoms, Or an ester group by reaction with an aryl group which may have an alkyl substituent (which represents an aryl group having 6 to 12 carbon atoms)) or an alcohol (R ² OH (R ² is a C 1-6 carbon atom). An alkyl group or an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent is represented by the reaction with an alkyl group, and further represented by the following formula (3). It can be derived into an acetal intermediate having excellent thermal stability. The acetal intermediate represented by the following formula (3) is a carboxylic anhydride ((R ² CO) ₂ O (R ² is an alkyl group having 1 to 6 carbon atoms) or an alkyl substituent. 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 reaction with propanediol after conversion to an ether group by reaction with)).

(In the formula, B is —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.)
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, a cyclic acetal represented by the following formula (1) is mentioned as a preferred cyclic acetal intermediate.

In Formula (1), R ¹ is a group represented by a hydrogen atom, —CH ₂ OH, —CH ₂ OR ² or —CH ₂ O (C═O) R ² , and R ² has 1 to 6 carbon atoms. Or an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent. As the preferred substituents when R ² an alkyl substituent include alkyl group having 1 to 6 carbon atoms.

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

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

Regarding HMF (manufactured by Sigma Alducci) and three types of HMF acetals (PD-HMF, EG-HMF, Me-HMF) obtained by the method of Experimental Example 7 described later, the thermal stability is as follows. Evaluation was performed.
3-4 mg of a sample was introduced into a pressure-resistant NMR tube and treated for 2 hours under vacuum evacuation at room temperature to remove moisture contained in the sample. Thereafter, the tube was put in an oven, heated from room temperature to 200 ° C. at 10 ° C./min, and held 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 thermal stability was evaluated by analyzing the residual rate of the sample by ¹ H NMR. The greater 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. However, even if it is an acetal body, acyclic Me-HMF is more thermally stable than HMF. I know it ’s bad.

[Experimental Example 1-2: Thermal Stability Evaluation of FRL and FRL Acetal]

  Results of evaluating 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 Experimental Example 1-1 As a residual rate after 2 hours, it was 12% in the case of FRL, while it was significantly 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 PD-HMF Ester and Ether]

  About the ester body (PD-HMF-acetate) and ether body (PD-HMF-ether) of HMF acetal (PD-HMF) obtained by the method of Experimental Example 7 described later, the same method as in Experimental Example 1-1 was used. As a result of evaluating the thermal stability, the residual ratio after 2 hours was 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, except that PD-HMF was held at 150 ° C. or 180 ° C. for 2 hours, the residual rate of the heated sample was analyzed by ¹ H NMR in the same manner as in Experimental Example 1, and the result was shown as Experimental Example The results are shown in Table 1 below together with the results of heating at 200 ° C.

  Table 1 shows that there is no correlation between the heating temperature and the residual rate. In addition, about 50% of the decomposition products of PD-HMF were HMF which is a hydrolyzate of an acetal body due to water brought into the solvent.

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

[Experimental Example 4: Synthesis of HMF acetal from monosaccharides derived from biomass raw materials I]
An experiment was conducted to synthesize HMF acetal from glucose using Nb ₂ O ₅ obtained by calcining hydrous niobic acid (“HY-340” manufactured by CBMM) at 400 ° C. for 4 hours as a catalyst. .

100 mg or 200 mg of Nb ₂ O ₅ and 20 mg of glucose were placed in a pressure-resistant glass container, and THF 1.8 mL, water 0.2 mL, and 1,3-propanediol 0.2 mL 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 vessel 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 relative to glucose was determined, and the results are shown in Table 3.

  From Table 3, No. with a catalyst amount of 100 mg. No. 1 was 200 mg. 2 shows that the yield of PD-HMF is higher.

[Experimental Example 5: Synthesis of HMF acetal from monosaccharide II]
Using the following as the catalyst, an experiment was conducted to synthesize HMF acetal from glucose by changing the catalyst.

_{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 Catalyst
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 THF 1.4 mL, water 0.6 mL, and 1,3-propanediol 0.2 mL 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 vessel 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 relative to glucose was determined. The results are shown in Table 4.

Table 4 shows 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 to synthesize HMF acetal by changing raw material monosaccharides using Nb ₂ O ₅ obtained by calcining hydrous niobic acid (“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 THF 1.8 mL, water 0.2 mL, and 1,3-propanediol 0.2 mL 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 vessel was immediately introduced into cold water to stop the reaction, and the generated HMF and PD-HMF were quantified by gas chromatography in the same manner as in Experimental Example 4 to obtain the yield for glucose or fructose. The rate was determined 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>
By adding 1.5 molar equivalents of acetic anhydride and 2 molar equivalents of triethylamine to an acetonitrile solution (0.1 mol / L) in which HMF (Sigma Aldrich) is dissolved, the mixture is stirred at room temperature for 1 hour. The hydroxyl group of HMF was converted to acetate. The obtained product was purified by column chromatography to obtain an HMF acetate form.

<Synthesis of EG-HMF>
The HMF acetate obtained by the above-mentioned 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 ) and An excess amount of trimethyl orthoformate and ethylene glycol were added, and the mixture was stirred at room temperature to convert the aldehyde moiety bonded 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, thereby obtaining the desired ethylene glycol-HMF acetal (EG-HMF).

<Synthesis of PD-HMF>
The HMF acetate obtained by the above-mentioned 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 ) and An excess amount of trimethyl orthoformate and 1,3-propanediol were added, and the mixture was stirred at room temperature to convert the aldehyde moiety bonded 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, thereby obtaining the desired propanediol-HMF acetal (PD-HMF).

<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 relative to HMF Of trimethyl orthoformate was added and stirred at room temperature for 3 hours. The target PD-HMF-ether was obtained by separating the catalyst from the solution after the reaction and further purifying it by column chromatography.

<Synthesis of PD-HMF-acetate>
In a dichloromethane solution (HMF acetate concentration: 0.1 mol / L) in which the HMF acetate 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. Of trimethyl orthoformate 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 target PD-HMF-acetate.

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

[Example 1: Production of carboxylic acid ester from PD-HMF derived from biomass material]
As described below, PD-HMF was oxidatively esterified using a gold catalyst (Au / CeO ₂ ) supported on cerium oxide to produce a furan carboxylate ester.
The cerium oxide support was prepared by a liquid phase precipitation method. Specifically, a white precipitate formed by adding ammonia water to an aqueous solution in which cerium nitrate hexahydrate is dissolved until pH = 10 is collected by filtration, and dried in an oven at 80 ° C. for about 10 hours. The cerium oxide support was used. Next, 0.2 mol / L NaOH aqueous solution was added to 160 mL aqueous solution in which chloroauric acid (manufactured by Wako Pure Chemical Industries, 350 mg) was dissolved to adjust pH to 10 and 4 g of cerium oxide was dispersed therein. 50 mL of aqueous solution was added, and 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 the solid collected by filtration was washed repeatedly with distilled water until no chloride ions remained. Residual chloride ions were confirmed by precipitation with an aqueous AgNO ₃ solution. The solid sample after washing was dried in an oven at 80 ° C. for about 10 hours and used as Au / CeO ₂ . The amount of Au supported on 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.

100 mg of PD-HMF obtained by the method of Experimental Example 7 as a substrate, 2 equivalents of Na ₂ CO ₃ , 1 mL of methanol, and 50 mg of the above Au / CeO ₂ were added to a pressure vessel, and oxygen gas was charged to 5 atm. Thereafter, the solution was heated and stirred at 120 ° C. for 15 hours. After the pressure vessel was quickly cooled to room temperature, the substrate and the product were qualitatively and quantified by ¹ H NMR. As a result, furandicarboxylic 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 completion of the reaction. Also, no dirt deposits in the autoclave were confirmed.

[Examples 2-1 to 2-7: Production of carboxylic acid from PD-HMF derived from biomass material]
As a substrate, PD-HMF obtained by the method of Experimental Example 7, base, 5 mL of distilled water, 1 equivalent of Au / CeO ₂ catalyst with respect to the substrate was added to a pressure vessel, and oxygen gas was charged to 5 atm. Furandicarboxylic 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 substrate mass, the substrate concentration, the base to be used, and the addition amount thereof were changed. After the reaction, the pressure vessel was cooled to room temperature, and then the substrate and product were qualitatively and quantified by ¹ H NMR. The results are shown in Table 6. In all the systems, furandicarboxylic acid (FDCA) was produced in a high yield, and it was confirmed that solid by-products were hardly produced in the reaction solution after the reaction was completed. Also, no dirt deposits in the autoclave were confirmed.

[Comparative Example 1: Production of carboxylic acid ester from biomass-derived HMF]
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 vessel was quickly cooled to room temperature, and then the substrate and product were qualitatively and quantified by ¹ H NMR. The yield of furandicarboxylic acid methyl ester, which is the target product, was as low as 6%, and a large amount of solid by-product was produced in the reaction solution after completion of the reaction.

[Comparative Example 2: Production of carboxylic acid from biomass-derived HMF]
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 in the presence of 2 equivalents of Na ₂ CO _{3 with} respect to HMF. After the pressure vessel was cooled to room temperature, the substrate and product were qualitatively and quantified by ¹ H NMR. The yield of furandicarboxylic acid as the target product was as low as 28%, and a large amount of solid by-product was produced in the reaction solution after the completion of the reaction.

  The carboxylic acid ester and the carboxylic acid obtained by the present invention are industrially useful as a resin raw material such as a polyester resin. 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 (9)

  A method for producing a carboxylic acid ester or carboxylic acid having a furan skeleton derived from a biomass raw material, wherein the carboxylic acid ester or carboxylic acid is passed through a cyclic acetal intermediate.   The method for producing a carboxylic acid ester or carboxylic acid according to claim 1, wherein the carboxylic acid ester or carboxylic acid having the furan skeleton is produced by an oxidation reaction of the cyclic acetal intermediate.   The method for producing a carboxylic acid ester or a carboxylic acid according to claim 1 or 2, wherein the carboxylic acid ester or carboxylic acid having a furan skeleton is a furan dicarboxylic acid ester or a furan dicarboxylic acid.   The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 3, wherein the cyclic acetal intermediate is produced using a mixed solvent of water and an organic solvent.   The method for producing a carboxylic acid ester or carboxylic acid according to any one of claims 1 to 4, 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 5, further comprising a step of adding a diol to the reaction system.   The method for producing a carboxylic acid ester or a carboxylic acid according to claim 6, wherein the cyclic acetal intermediate is produced by a reaction between an aldehyde having a furan skeleton and the diol. The cyclic acetal represented by following formula (1).

(In the formula, R ¹ is a group represented by a hydrogen atom, —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. Group or an aryl group having 6 to 12 carbon atoms which may have an alkyl substituent.)   A method for producing a carboxylic acid ester or a carboxylic acid, comprising producing a furan carboxylate or a carboxylic acid from the cyclic acetal according to claim 8.

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