JP6057376B2 - Method for reducing hydroxymethylfurfural and / or furfural - Google Patents

Description

  The present invention relates to a method for reducing 5-hydroxymethyl-2-furfural (hydroxymethylfurfural) and / or furfural. Specifically, the present invention relates to a process for producing dimethylfuran and / or methylfuran by hydrogenation using these hydroxymethylfurfural and / or furfural as starting materials.

  In recent years, a method for synthesizing dimethylfuran (DMF), which has attracted attention as a biofuel, reduces hydroxymethylfurfural (HMF) obtained as a C6 route from fructose and glucose, which are biomass raw materials, to dihydroxymethylfuran (DHMF). And finally dimethylfuran (DMF) is synthesized by hydrogenolysis. In particular, since hydroxymethylfurfural (HMF) can be easily synthesized from sugar chains such as fructose and glucose, production methods using biomass as a raw material have been actively studied (Non-patent Document 1). Furthermore, methylfuran obtained by reduction from furfural obtained through the C5 route simultaneously with the C6 route is also expected to be used for biofuels and the like (see FIGS. 1 and 2).

  Hydroxymethylfurfural or the product obtained from the reduction of furfural is difficult to obtain dimethylfuran or methylfuran selectively from various compounds. In many cases, a compound having a furan skeleton and a hydrofuran skeleton (2,5-dihydroxymethyltetrahydrofuran: DHMTHF; 2-methyltetrahydrofuran-5-methanol: MTHFM; 2,5-dimethyltetrahydrofuran: DMTHF; 2- Methyltetrahydrofuran: MTHF; tetrahydrofuran: THF) was easily obtained, and it was difficult to selectively obtain dimethylfuran or methylfuran.

  Among them, several methods have been reported as a direct conversion method from hydroxymethylfurfural to dimethylfuran. In Patent Document 1, when dimethylfuran is obtained from hydroxymethylfurfural, formic acid is used as a hydrogen source, tetrahydrofuran is used as a solvent, Pd / C is used as a catalyst, and the reaction is performed by refluxing for 15 hours. The yield is 88%, which is a relatively good value. However, since sulfuric acid is used, post-treatment is necessary, tetrahydrofuran is used to remove the organic solvent, and formic acid is used. Therefore, there is a problem that the reaction is extremely slow. Patent Document 2 shows a high conversion rate by using Cu—Ru / C as a catalyst in a reaction in butanol. However, there is a problem that the selectivity of dimethylfuran is 71% at the maximum and the reaction time requires 10 hours or more.

  In Non-Patent Document 2, the yield of dimethylfuran is as low as about 25% by reaction in water. Although Non-Patent Document 3 is hydrogenated in supercritical methanol, the yield of dimethylfuran is about 50%. Furthermore, Non-Patent Document 4 is a reaction condition in which the yield of dimethylfuran is as good as 95%, but the hydrogen source is formic acid and sulfuric acid is the acid catalyst. Therefore, it is necessary to heat and reflux in an organic solvent (tetrahydrofuran) for 15 hours. Further, since formic acid is used as a reducing agent, a large amount of carbon dioxide is generated.

  On the other hand, the present inventors have proposed various methods for hydroreduction using supercritical carbon dioxide as a reaction medium (Patent Documents 3, 4, 5, and 6). Since supercritical carbon dioxide dissolves hydrogen infinitely, it can be adjusted to an arbitrary hydrogen concentration with respect to the conventional hydrogenation method. Thereby, since there are no problems such as gas-liquid equilibrium, it is possible to efficiently hydrogenate at a low temperature of 100 ° C. or lower. However, these hydrogenation reductions are hydrogenation-type reductions. For example, alcohols are synthesized by hydrogenation-type reduction of aldehydes, amines are produced by hydrogenation-type reduction of nitriles, and amines are produced by hydrogenation-type of nitro groups. Etc. are being considered.

  Furthermore, the present inventors have proposed a dehydration-type reduction method instead of a hydrogenation-type reduction. For example, a technique for selectively obtaining alkanes by reducing hydroxymethylfurfural and hydroxymethylfurfural derivatives in supercritical carbon dioxide has been proposed (Patent Document 7). This is a technique for completing reduction by using hydroxymethylfurfural or a hydroxymethylfurfural derivative as a raw material, finally opening a furan ring by hydrogenation, and further obtaining alkanes by dehydration. By using this method, it is an epoch-making technology that can quickly obtain fuel with high octane number such as gasoline. However, since it is a technique that completes multi-stage reduction at once, it is considered that there are a plurality of reaction routes. Therefore, it is difficult to selectively obtain dimethylfuran even if the reduction is stopped halfway in this method.

  Patent Document 8 proposes hydrogenation of furans in water. At that time, it was reported that hydrogenation was promoted by adding carbon dioxide, but the reaction was promoted too much and no formation of dimethylfuran was observed, and the most reduced tetrahydrofuran was produced. The reaction has not been sufficiently controlled.

  For this reason, the synthesis method of dimethylfuran (DMF) and methylfuran, which are attracting attention not only as biofuels but also as various intermediate raw materials, can be used without using strong acids, strong bases, or various organic solvents, and waste liquid after reaction. If it can be easily produced without any problem of processing, it is useful as a clean and energy-saving production method, and establishment of production technology is desired.

US Publication No. 2011/163880 International Publication No. 2007/146636 Pamphlet JP 2011-225502 A JP 2010-241691 A JP 2005-289875 A JP 2006-137740 A JP 2010-047543 A JP 2012-51853 A

Yuriy Roman-Leshkov et al., "Production of dimethylfuran for liquid fuels from biomass-derived carbohydrates". Nature 2007,447 (7147): p.982-986. Jean Marcel R. Gallo et al., Green Chemistry, 2013, vol. 15, p. 85-90. Thomas S. Hansen et al., Green Chemistry, 2012, vol. 14, p. 2457-2461. Todsapon Thananatthanachon et al., Angewandte Chemie, International Edition, 2010, vol. 49, p. 6616-6618.

  The present invention has been made in view of the above circumstances, and the method of synthesizing dimethylfuran (DMF) and methylfuran without using a strong acid, a strong base, or various organic solvents, and the problem of waste liquid treatment after the reaction. An object of the present invention is to provide a clean and energy-saving production method that can be easily produced without any problems.

  Therefore, the present inventors have studied various conditions in the reduction reaction using supercritical carbon dioxide as a medium, and as a result, have found that the presence of a small amount of water greatly changes the selectivity, and have reached the present invention. That is, in the absence of water, the desired product is hardly obtained, and even in the presence of a large amount of water, hydrolysis and the like are likely to occur, and side reactions are likely to occur. In addition, since the reaction mechanism is completely different when water itself becomes a medium, the product is different and the desired product cannot be obtained.

  In the present invention, supercritical carbon dioxide is used as a reaction medium, and in the presence of a solid catalyst, hydrogenation-type reduction of olefins is suppressed by a small amount of water dissolved in a mixed solution of supercritical carbon dioxide and a substrate. By facilitating the reduction of dimethylfuran, it was possible to selectively obtain dimethylfuran (DMF) or methylfuran while suppressing overreaction.

That is, the present invention
[1] In a method for producing 2,5-dimethylfuran and / or 2-methylfuran by hydrogenation in the presence of a solid catalyst using hydroxymethylfurfural and / or furfural as a starting material,
2,5-dimethylfuran and / or 2 characterized in that supercritical carbon dioxide is used as a reaction solvent, and an amount of water dissolved in a mixed solution of the starting material and supercritical carbon dioxide is added to the reaction system. -Method for producing methyl furan.
[2] The 2,5-dimethylfuran and / or 2-methylfuran according to the above [1], wherein the amount of water added is 1% by volume or more and 8% by volume or less based on the volume of the supercritical carbon dioxide. Manufacturing method.
[3] The 2,5-dimethylfuran and / or 2-methyl according to the above [1] or [2], wherein the pressure of the supercritical carbon dioxide is a critical pressure or 7.3 MPa to 16 MPa. A manufacturing method for furan.
[4] The 2,5-dimethylfuran and / or 2-methylfuran according to any one of the above [1] to [3], wherein the hydrogen pressure is 0.2 MPa or more and 2 MPa or less. Manufacturing method.
[5] The above [1] to [4], wherein the solid catalyst is a solid catalyst in which palladium is supported on carbon, a solid catalyst in which platinum is supported on carbon, or a solid catalyst in which rhodium is supported on carbon. The method for producing 2,5-dimethylfuran and / or 2-methylfuran according to any one of the above.
[6] The 2,5-dimethylfuran and / or 2-methylfuran according to any one of [1] to [5] above, wherein the reaction temperature is 50 ° C. or higher and 100 ° C. or lower. Production method.

  In the present invention, a method for synthesizing dimethylfuran (DMF) and methylfuran can be easily produced without using a strong acid, a strong base, or various organic solvents, and without the problem of waste liquid treatment after the reaction. An energy-saving synthesis method can be provided. In addition, by using supercritical carbon dioxide, the reaction time is short, the reaction temperature can be significantly lowered, the product can be easily separated and purified, and the conversion rate and yield can be increased.

The reaction diagram which shows the synthetic | combination path | route C6 from biomass raw material to biomass fuel. The reaction diagram which shows the synthetic | combination path | route C5 from biomass raw material to biomass fuel. It is a GC chart and a mass spectrum which 2,5-dimethylfuran which is a product in reaction time 2 hours of Example 1 shows. It is the GC chart and mass spectrum which the standard substance of 2, 5- dimethylfuran shows.

  The present invention uses a small amount of hydroxymethylfurfural (HMF) and / or furfural as a starting material, dissolved in a mixed solution of supercritical carbon dioxide and the starting material in the presence of a solid catalyst using supercritical carbon dioxide as a medium. By water, hydrogenation-type reduction of olefins is suppressed, and dehydration-type reduction is facilitated, so that dimethylfuran (DMF) or methylfuran is selectively obtained while suppressing overreaction. The reaction from the starting material to the final product is as follows:

  Hydroxymethyl furfural and / or furfural used as a raw material in the present invention can be produced by any origin and method. In particular, it is preferable to use a raw material produced from fructose, glucose or the like which is a biomass raw material.

  The present invention uses supercritical carbon dioxide as the reaction medium. Supercritical carbon dioxide is carbon dioxide present at a critical temperature of 31 ° C. and a critical pressure of 7.38 MPa, and at temperatures and pressures above this. The supercritical carbon dioxide used in the present invention can be used in any state as long as it has a temperature and pressure above the critical point. Usually, the temperature is selected from the range of 31 ° C. to 200 ° C., and the pressure is selected from the range of 7 MPa to 27 MPa. Preferably, the temperature is 35 ° C. or more and 100 ° C. or less, and the pressure is 7 MPa or more and 16 MPa or less. More preferably, the temperature is 50 ° C. or more and 100 ° C. or less, and the pressure is a temperature or pressure of carbon dioxide of 7.3 MPa or more and 16 MPa or less.

  In the present invention, by using supercritical carbon dioxide as a reaction medium, carbon dioxide is gasified only by releasing the supercritical state of carbon dioxide after the reaction to normal temperature and normal pressure, and the product and the solid catalyst are separated. Separation makes it possible to separate and recover the product and the catalyst, and it is easy to reuse the catalyst. Moreover, it can synthesize | combine easily, without using the strong acid and strong base which were used conventionally, or various organic solvents, and the problem of the waste liquid treatment after reaction. Thereby, it is not necessary to use a material having high corrosion resistance as a material for a reactor as a reaction apparatus and peripheral equipment, and it can be made inexpensive.

  In the present invention, in order to obtain a target reaction product in the presence of a supercritical carbon dioxide medium and a solid catalyst, an amount of water that is dissolved in a mixed solution of the starting material and supercritical carbon dioxide is required. It is. In the absence of water, the desired product is hardly obtained. On the other hand, when the amount of water is large, the starting material dissolves well in water, so that hydrolysis and the like easily occur. In addition, side reactions are likely to occur, and water itself becomes a medium, so that the reaction mechanism using supercritical carbon dioxide as a medium is lost. For this reason, the reaction cannot be controlled and the desired product cannot be obtained. In the present invention, the hydrogenation-type reduction of olefins is suppressed and the dehydration-type reduction is facilitated by a small amount of water of about several to tens of percent dissolved in a mixed solution of supercritical carbon dioxide and a starting material. As a result, it was possible to selectively obtain a product while suppressing overreaction.

  The amount of water that dissolves in the mixed solution of the starting material and supercritical carbon dioxide is an amount that does not cause hydrolysis or the like and is in a state where side reactions are unlikely to occur, or an amount that does not cause water itself to become a medium. is there. That is, as the amount of water to be dissolved, an amount of 0.1 volume% or more and 10 volume% or less is added with respect to the volume of supercritical carbon dioxide. Preferably, it is 1% by volume or more and 8% by volume or less.

  Hydrogen used for the reaction in the present invention may be introduced into the reaction system at a predetermined pressure. The hydrogen pressure is not particularly limited as long as it is 0.1 MPa or more, but if the hydrogen pressure is too high, the reduction reaction proceeds too much, so the upper limit is 3 MPa. The hydrogen pressure introduced into the reaction system is preferably 0.2 MPa or more and 2 MPa. More preferably, it is 0.2 MPa or more and 1.5 MPa.

  The solid catalyst used in the present invention uses a transition metal as a supported metal which is one of the catalytic active components, and the metal is an inorganic carrier such as alumina, silica, carbon or activated carbon, barium carbonate, diatomaceous earth, magnesia, titania, zirconia and the like. It is carried on. Among these, it is preferable to use a support of alumina, activated carbon, silica, mesoporous silica (MCM-41), aluminum or gallium-containing mesoporous silica (Al-MCM-41, Ga-MCM-41). The supported metal species that are one of the catalytically active components are vanadium, chromium, manganese, iron, nickel, copper, niobium, molybdenum, ruthenium, rhodium, palladium, silver, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold Preferably, chromium, nickel, palladium, platinum, rhodium, and ruthenium are used, and more preferably, palladium, platinum, rhodium, and ruthenium are used.

  Preferably, as a solid catalyst, palladium, platinum, rhodium, ruthenium is the main catalyst component, and supported on an inorganic carrier such as alumina, silica, mesoporous silica (MCM-41), activated carbon, barium carbonate, diatomaceous earth, magnesia, titania, zirconia. It is a thing. Among these, it is more preferable to use a solid catalyst in which palladium is supported on carbon, a solid catalyst in which platinum is supported on carbon, or a solid catalyst in which rhodium is supported on carbon.

  The shape of the solid catalyst is not particularly limited, but a pellet, a sphere, a ring, a granule, a powder, etc. can be used, and the catalyst particle size may be selected according to the inner diameter of the reaction tube. Not particularly restricted. The amount of the catalyst used is not particularly limited and can be determined in consideration of the reaction rate, heat removal, catalyst cost, etc., but is preferably an amount effective for catalyst activity and as small as possible.

  The solid catalyst can be produced by a conventionally known synthesis method. For example, sol-gel method, coprecipitation method, impregnation method and the like are exemplified. The amount of the solid catalyst used is preferably 0.01 to 1 part by weight, more preferably 0.1 to 1 part by weight with respect to 1 part by weight of the raw material. More preferably, it is 0.1 to 0.5 parts by weight.

  In the present invention, since a solid catalyst is used, post-treatment for separating the catalyst from the reaction system is easy. That is, since it is a solid catalyst, it can be easily recovered by filtration and can be reused with little decrease in catalyst activity. This solid catalyst does not use harmful metals or the like, and is a safe, inexpensive and highly selective catalyst system.

  The reaction mechanism for forming 2,5-dimethylfuran and / or 2-methylfuran from hydroxymethylfurfural and / or furfural in the present invention is a reduction reaction using carbon dioxide as a reaction medium in a supercritical state. That is, it is a dehydrogenation reaction to 2,5-dimethylfuran and / or 2-methylfuran by hydrogenation in the presence of a solid catalyst using hydroxymethylfurfural and / or furfural as a starting material. Using carbon dioxide as a reaction medium, the reaction from the raw material to the final product occurs in one step, and 2,5-dimethylfuran or 2-methylfuran is easily produced. Usually, formic acid is often used to form 2,5-dimethylfuran or 2-methylfuran from hydroxymethylfurfural or furfural. In the present invention, carbonic acid produced by water and carbon dioxide plays a role as formic acid. It is considered to have played.

  The reaction mechanism for forming 2,5-dimethylfuran (DMF) from hydroxymethylfurfural (HMF) in the present invention is a hydrogenation and dehydrogenation reaction in the presence of a solid catalyst.

  In the present invention, the reaction mechanism for forming 2,5-dimethylfuran is the reduction of hydroxymethylfurfural (HMF) as a starting material through 2,5-dihydroxymethylfuran (DHMF) by reduction, and 2-methyl-furan by hydrogenolysis. A reaction pathway for producing 2,5-dimethylfuran (DMF) via 5-hydroxymethylfuran (HMMF), and 2-methyl-5-methylfurfural (HMF) through 5-methylfurfural (MF). There are two possible reaction routes for producing 2,5-dimethylfuran (DMF) via hydroxymethylfuran (HMMF). According to the present invention, 2,5-dimethylfuran (DMF) can be generated from the raw material in a short time by any reaction route.

  The reaction mechanism for forming 2-methylfuran from furfural in the present invention is a reaction in which hydroxymethylfuran (MFA) is formed by reduction in the presence of a solid catalyst to dehydrogenate hydroxymethylfuran. Shown in In one step, 2-methylfuran can be produced in a short time from furfural as a starting material.

  As the reaction apparatus in the present invention, a batch reaction apparatus or a continuous reaction apparatus can be used. In the continuous type, for example, a fixed bed flow type reaction apparatus, a fluidized bed type reaction apparatus or the like can be used.

  In the present invention, the reaction product 2,5-dimethylfuran or 2-methylfuran can be easily separated using separation techniques that exist in the past as separation and purification from the reaction system. For example, the separation can be performed using a distillation method using a difference in boiling points.

  2,5-Dimethylfuran or 2-methylfuran produced in the present invention is about 40% higher in energy density than ethanol as a biofuel and is similar to gasoline. When isolating 2,5-dimethylfuran after production, because it is chemically stable and does not mix with water, it does not absorb moisture in the air and its boiling point is 14 ° C higher than ethanol. The energy required for this is only 1/3 of that required for ethanol isolation and is useful. In addition, it can be used as various intermediate materials.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

<Analytical means (GC / MS)>
Qualitative and quantitative analysis of the product was performed using a gas chromatograph / mass spectrometer GC / MS (GC3800-Saturn2200) manufactured by Bruker Daltonics and a gas chromatograph / flame ionization detector GC / FID (GC-2010) manufactured by Agilent. . The column is DB-5 manufactured by Shimadzu GL Corporation, the injection volume is 1.0 μL, the vaporization chamber temperature is set to 250 ° C., the column oven temperature is set to 40 ° C., the column temperature is held at 40 ° C. for 5 minutes, and 10 The temperature was raised to 150 ° C. at a rate of ° C./min, held for 5 min and analyzed. After confirming that the retention time of the peak considered to be the target product matches that of the standard substance, the peak part is analyzed by mass spectrum, and the molecular weight of the main part and the pattern of decomposition products are those of the standard substance. Qualitative analysis was performed by agreeing with.

The conversion rate refers to the ratio of the amount of the starting material consumed by reaction with respect to the charged amount of the starting material, and the selectivity refers to the ratio of the target product amount to the total product amount. Determined by
Conversion% (mol%) = Consumption of raw material (mol) / Amount of raw material used (mol) × 100
Selectivity% (mol%) = product amount (mol) / total product amount (mol) × 100

[Example 1]
A 50 mL autoclave was charged with 0.02 g of catalyst and 0.1 g of hydroxymethylfurfural (HMF: Aldrich) at a weight ratio of 1: 5, and further with 1 mL of water, and the container was heated to a temperature of 80 ° C. Next, hydrogen was introduced to a predetermined pressure (1 MPa), and then carbon dioxide was introduced using a pump. When the pressure reached 10 MPa, the reaction was started by stirring with a stirrer. After 2 hours, the reaction vessel was ice-cooled, and the carbon dioxide was slowly returned to normal pressure. After the reaction, the compound remaining in the autoclave was extracted with acetone or chloroform, the catalyst was filtered, qualitative analysis was performed by GC-MS, and quantitative analysis was performed by GC. The catalyst was changed as shown in Table 1 to give Examples 1-1 to 1-6, respectively. The results are shown in Table 1.

  The chromatogram and mass spectrum results of the qualitative analysis and quantitative analysis of the reaction product are shown in the figure. The upper part of FIG. 3 is a GC chromatogram of the product after 2 hours of reaction time, the horizontal axis is the retention time, the lower part is a mass spectrum with a retention time RT of 1.9 minutes, and the horizontal axis indicates the molecular weight. ing. The upper part of FIG. 4 is a GC chromatogram of the pure substance 2,5-dimethylfuran as a standard substance, the horizontal axis is the retention time, the lower part is the mass spectrum, and the horizontal axis indicates the molecular weight. From the above results, it was confirmed that 2,5-dimethylfuran was produced.

  In this example, Pd / C (Palladium on activated carbon, 5% metal supported by Aldrich), Pd / Al-MCM-41 (AIST: adjusted by the inventor, hereinafter referred to as “inventor adjusted”) Pd / Ga-MCM-41 (adjusted by the inventor), Pt / C (Platinum on carbon, metal loading 5%, Aldrich), Rh / C (Rhodium on carbon, metal loading 5) %, Manufactured by Aldrich) and Ru / MCM-41 (adjusted by the inventor), conversion of 2,5-dimethylfuran from 100% to 32.7% and selectivity from 100% to 1.7% I was able to. More preferable solid catalysts include Pd / C, Pt / C, and Rh / C. The Pd / C catalyst had good conversion rate of 100% and selectivity of 100%. In addition, 2-methyl-5-hydroxymethylmethylfuran (HMMF) and 5-methylfurfural (MF) are reactants in the middle of the hydrocracking reaction. Although it becomes an impurity with respect to dimethylfuran, only 2,5-dimethylfuran can be separated by separation and purification. The above-mentioned catalyst can be prepared by the method described in “Catalyst Preparation Handbook” (NTS, April 20, 2011, p.272-273).

[Comparative Examples 1 and 2]
In Example 1-1, Comparative Example 1 was performed under the same conditions as Example 1-1 except that 1 mL of water was not added and carbon dioxide was not introduced. In Example 1-1, Comparative Example 2 was performed under the same conditions as Example 1-1 except that 1 mL of water was not added and the reaction time was 4 hours. Table 2 shows the conversion and selectivity at that time. When water was not used, 2,5-dimethylfuran (DMF) was not produced.

[Example 2, Comparative Example 3]
In a 50 mL autoclave, 0.02 g of catalyst Pd / C (Palladium on activated carbon, 5% metal supported by Aldrich) and 0.1 g of hydroxymethylfurfural (HMF: Aldrich) were used at a ratio of 1: 5 by weight. After adding 1 mL of water, the container was heated to a temperature of 80 ° C. Next, hydrogen is introduced to a predetermined pressure (1 MPa), and then the introduction amount of carbon dioxide is introduced from 0 to 16 MPa using a pump. When the pressure reaches the predetermined pressure, the reaction is started by stirring with a stirrer. I let you. After 2 hours, the reaction vessel was ice-cooled, and the carbon dioxide was slowly returned to normal pressure. After the reaction, the compound remaining in the autoclave was extracted with acetone or chloroform, the catalyst was filtered, qualitative analysis was performed by GC-MS, and quantitative analysis was performed by GC. Those having a carbon dioxide pressure of 0 MPa to 16 MPa were designated as Comparative Example 3 and Example 2-1 to Example 2-6, respectively. Table 3 shows the carbon dioxide pressure, conversion rate, and selectivity at that time.

  When carbon dioxide was not introduced, the conversion rate of 2,5-dimethylfuran was 4% and the selectivity was very low, and Comparative Example 3 was used. In particular, when the carbon dioxide pressure was 10 to 12 MPa, the conversion rate and selectivity could be 100%, and the yield of 2,5-dimethylfuran was very good.

[Example 3]
In Example 1-1, Example 3-1 to Example 3-5 were performed under the same conditions as Example 1-1 except that hydrogen was changed to a pressure of 0.2 MPa to 2 MPa. Table 4 shows the hydrogen pressure, conversion rate, and selectivity at that time. If the hydrogen pressure was 0.2 MPa or more, 2,5-dimethylfuran could be obtained sufficiently. On the other hand, when the hydrogen pressure was 2 MPa, the reduction reaction proceeded too much and the conversion rate was lowered.

[Example 4]
In Example 1-1, Example 4-1 to Example 4-4 were performed under the same conditions as in Example 1-1 except that the reaction temperature was changed from 35 ° C. to 100 ° C. Table 5 shows the reaction temperature, conversion rate, and selectivity at that time.

At a reaction temperature of 80 ° C., the conversion and selectivity of 2,5-dimethylfuran were 100%, and the yield was very good. The reaction proceeded even at 35 ° C., the lower limit of the supercritical temperature. In addition, it was found that the reaction proceeded sufficiently under the temperature conditions up to 100 ° C. compared to the conventional reaction temperatures exceeding 120 ° C. and 220 ° C.

[Example 5]
In Example 1-1, Examples 5-1 to 5-4 were performed under the same conditions as Example 1-1 except that the amount of water added was changed from 0.5 mL to 4.0 mL. Table 6 shows the amount of water added, the conversion rate, and the selectivity.

  The amount of water added corresponds to 1% to 8% by volume with respect to the volume of supercritical carbon dioxide. Among these, the addition amount of 0.5 to 1.0 mL is optimal, and this amount corresponds to 1% by volume to 2% by volume with respect to the volume of supercritical carbon dioxide.

[Example 6]
In Example 1-1, Examples 6-1 to 6 were carried out under the same conditions as Example 1-1 except that the weight ratio of the solid catalyst and the raw material was changed from 1: 2 to 1:10. -3. Table 7 shows the ratio of the solid catalyst to the raw material, the conversion rate, and the selectivity.

  The weight ratio of the starting material to the solid catalyst is 0.1 to 0.5 with respect to the starting material 1. In any amount of the solid catalyst in this range, the yield of 2,5-dimethylfuran was optimum.

[Example 7]
Using 50 g of autoclave as raw material with 0.1 g of furfural (Aldrich) and 0.02 g of Pd / C (Palladium on activated carbon, 5% metal loading, Aldrich) as the solid catalyst, hydrogen pressure 0 The reaction was conducted at 2 MPa, a carbon dioxide pressure of 10 MPa, and a reaction temperature of 80 ° C. The reaction time of 10 minutes and 15 minutes was designated as Example 7-1 and Example 7-2. Table 8 shows the conversion and selectivity at that time. The reaction was short, and the conversion and selectivity were very good at a reaction time of 15 minutes.

  The synthesis method of dimethylfuran and methylfuran, which are attracting attention as biofuels and various intermediate raw materials, can be easily produced without the use of strong acids, strong bases, or various organic solvents, and without the problem of waste liquid treatment after the reaction. It is useful as a clean and energy-saving manufacturing method.

Claims (6)

In a method for producing 2,5-dimethylfuran and / or 2-methylfuran by hydrogenation in the presence of a solid catalyst using hydroxymethylfurfural and / or furfural as a starting material,
2,5-dimethylfuran and / or 2 characterized in that supercritical carbon dioxide is used as a reaction solvent, and an amount of water dissolved in a mixed solution of the starting material and supercritical carbon dioxide is added to the reaction system. -Method for producing methyl furan.   2. The method for producing 2,5-dimethylfuran and / or 2-methylfuran according to claim 1, wherein the amount of water to be added is 1% by volume or more and 8% by volume or less based on the volume of the supercritical carbon dioxide.   The method for producing 2,5-dimethylfuran and / or 2-methylfuran according to claim 1 or 2, wherein the pressure of supercritical carbon dioxide is a critical pressure or 7.3 MPa to 16 MPa.   The method for producing 2,5-dimethylfuran and / or 2-methylfuran according to any one of claims 1 to 3, wherein the hydrogen pressure is 0.2 MPa or more and 2 MPa or less.   5. The solid catalyst according to claim 1, wherein a solid catalyst in which palladium is supported on carbon, a solid catalyst in which platinum is supported on carbon, or a solid catalyst in which rhodium is supported on carbon is used as the solid catalyst. The manufacturing method of 2, 5- dimethyl furan and / or 2-methyl furan of description.   The method for producing 2,5-dimethylfuran and / or 2-methylfuran according to any one of claims 1 to 5, wherein the reaction temperature is 50 ° C or higher and 100 ° C or lower.

Images