JP2013103921A - Method for producing levulinic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce levulinic acid from fructose in a high yield by performing a reaction under a mild condition.SOLUTION: The method for producing levulinic acid includes a reaction step for heating an aqueous solvent containing a solid catalyst and fructose to produce levulinic acid. The solid catalyst is a sulfo group-containing polymer. The reaction step is performed at <150°C. One example of the solid catalyst is a polymer containing a plurality of types of constituent units derived from a plurality of types of vinyl aromatic compounds, and the plurality of the types of the constituent units comprise a constituent unit derived from divinylbenzene and a constituent unit derived from styrene in which a sulfo group is introduced into a benzene ring.

Description

  The present invention relates to a method for producing levulinic acid.

  Levulinic acid can be used as a very important chemical raw material such as 2-methylterolahydrofuran, acrylic acid, 1,4-pentanediol. Until now, levulinic acid has been synthesized from sugars and carbohydrates using homogeneous catalysts such as hydrochloric acid, sulfuric acid and phosphoric acid. On the other hand, levulinic acid synthesis using a solid acid catalyst such as an ion exchange resin has also been studied (Patent Document 1 and Non-Patent Document 1).

European Patent Application Publication No. 2233477

R. A. Schraufnagel, H. F. Rase, Ind. End. Chem. Prod. RD. 1975, 14, 40.

  Homogeneous catalysts such as hydrochloric acid, sulfuric acid, and phosphoric acid are easily available, and levulinic acid can be synthesized in a yield of 60 to 70%. However, these homogeneous catalysts are difficult to separate from the reactants and difficult to reuse. In addition, when these catalysts are discarded, a large amount of basic substances are required, and there is a disadvantage that a large amount of waste salt is generated.

  In the method of Non-Patent Document 1 using an ion exchange resin as a catalyst, sucrose is converted into levulinic acid and hydroxymethyl fructose (HMF), but it requires a very long reaction time, and the yield of the product is also high not high. In the method of Patent Document 1, the reaction is performed at a high temperature (for example, 150 ° C.).

  In such a situation, an object of the present invention is to provide a method for easily producing levulinic acid from fructose in a high yield by performing the reaction under mild conditions.

  As a result of studies to achieve the above object, the present inventors have found that levulinic acid can be easily produced from fructose at a high yield by using a predetermined ion exchange resin. The present invention is based on this new knowledge.

  That is, the method of the present invention for producing levulinic acid includes a reaction step of producing levulinic acid by heating an aqueous solvent containing a solid catalyst and fructose, and the solid catalyst is a polymer having a sulfo group. Yes, the reaction step is carried out at a temperature below 150 ° C.

  According to the present invention, levulinic acid can be easily produced from fructose in a high yield by carrying out the reaction under mild conditions.

It is a graph which shows the result of < ¹ > H-NMR of the reaction product synthesize | combined in (a) Experiment 1 and (b) commercially available levulinic acid. It is a graph which shows the ¹³ C-NMR result of the reaction product synthesize | combined in Experiment 1 and (b) commercially available levulinic acid. It is a figure which shows the reaction mechanism anticipated in the method of this invention. (A) It is a figure which shows a partial structure of the amber list | wrist 15, and (b) a partial structure of Nafion NR50. It is a graph which shows the relationship between the frequency | count of regeneration of a catalyst, and catalyst activity.

  Embodiments of the present invention will be described below. Note that the present invention is not limited to the following embodiments and examples. In the following description, specific numerical values and specific materials may be exemplified, but other numerical values and other materials may be applied as long as the effects of the present invention are obtained.

The process of the present invention for producing levulinic acid comprises a reaction step of producing levulinic acid by heating an aqueous solvent comprising a solid catalyst and fructose. The solid catalyst used in this method is a polymer having a sulfo group (—SO ₃ H). This polymer is a resin in one aspect. And the said reaction process is implemented at the temperature below 150 degreeC.

  The solid catalyst is a polymer (resin) that does not dissolve in an aqueous solvent, and is used, for example, in a particulate form. By using a particulate solid catalyst, it becomes easy to separate and reuse the catalyst from the reaction solution after completion of the reaction.

  A preferred example of the solid catalyst is a polymer containing a structural unit derived from a vinyl aromatic compound, and a sulfo group bonded to a benzene ring derived from the vinyl aromatic compound. A vinyl aromatic compound is a compound containing an aromatic ring and a vinyl group bonded to the aromatic ring. Examples of vinyl aromatic compounds include styrene and dinivirbenzene.

  A particularly preferred example of the solid catalyst is a polymer containing a plurality of structural units derived from a plurality of types of vinyl aromatic compounds, wherein the plurality of structural units are a structural unit derived from divinylbenzene and a benzene ring. And a structural unit derived from styrene having a sulfo group introduced therein. The structural unit derived from divinylbenzene forms a crosslinked structure in the polymer (in the resin). Examples of such solid catalysts include Amberlyst-15, a Dow Chemical cation exchange resin.

The acidity function H ₀ (Hammett acidity function H ₀ ) of the solid catalyst may be about −2. Further, the specific surface area of the solid catalyst may be about 50 m ² / g.

  The reaction is carried out in an aqueous solvent. The aqueous solvent is a solvent containing water, and is typically water.

  The reaction proceeds by adding a solid catalyst and fructose and heating in an aqueous solvent. The reaction temperature is less than 150 ° C, and may be in the range of 100 to 140 ° C, for example. The reaction time is not particularly limited, but may be 8 hours or longer in order to increase the yield of levulinic acid, for example, 8 to 48 hours or 8 to 24 hours.

A preferred example of the present invention satisfies the following conditions.
(1) A polymer in which the solid catalyst includes a plurality of types of structural units derived from a plurality of types of vinyl aromatic compounds, the plurality of types of structural units including a structural unit derived from divinylbenzene and a sulfone group on the benzene ring. And a structural unit derived from styrene into which a group has been introduced (an example of this solid catalyst includes Amberlyst 15). A typical example of a solid catalyst is comprised only by these two types of structural units.
(2) The solvent is an aqueous solvent (for example, water).
(3) The reaction temperature is less than 150 ° C.

Hereinafter, the present invention will be described in more detail with reference to examples. Amberlyst® 15 (Amberlyst-15), Nafion®, and NR50 (Nafion NR 50) and P123 used in the following examples were purchased from Sigma-Aldrich. P123 is a block copolymer having a structure of poly (ethylene oxide) -poly (propylene oxide) -poly (ethylene oxide), and a formula of (ethylene oxide) ₂₀ (propylene oxide) ₇₀ (ethylene oxide) ₂₀ Is a copolymer having a molecular weight of 5800. Nafion NR50 is a solid catalyst mainly composed of an ether group, a sulfo group, and a perfluoro chain (fluorocarbon chain).

(Production of SBA-SO ₃ H)
A solid catalyst SBA-SO ₃ H was prepared by the following method. First, 2 g of P123 was dissolved in 50 mL of 2M (2 mol / L) hydrochloric acid at 313 K (40 ° C.) over 2 hours. To the resulting solution was added 4 mL of 98% tetraethoxysilane (TEOS). After an 8 hour pre-hydrolysis period, 1 mL of 3-mercaptopropyltrimethylsilane (95%) was added to the solution. Twelve hours later, the mixture was placed in an autoclave and heated at 373 K for 24 hours. P123 used as a template was removed by refluxing with ethanol. The solid thus obtained was treated with 80 mL of 5% H ₂ O ₂ to oxidize the thiol group (—SH) to a sulfo group (—SO ₃ H). The solid catalyst thus obtained was centrifuged, washed and dried at 333 K for 24 hours. In this way, a solid catalyst (SBA-SO ₃ H) was obtained. The specific surface area of the resulting SBA-SO ₃ H was measured by the BET method, was 425m ² / g.

(Experiment 1)
In Experiment 1, levulinic acid was synthesized from fructose using Amberlyst 15 as a catalyst.

  First, 0.3 g (1.67 mmol) of fructose and a predetermined amount (0.1 to 0.4 g) of Amberlyst 15 were placed in a capped glass tube together with 6 mL of water. Next, the reaction was allowed to proceed by heating the mixture in an oil bath at different temperatures (373K to 413K: 100 to 140 ° C.) while stirring. The heating time (reaction time) was 8 hours or 24 hours. After the reaction, the glass tube was taken out from the oil bath and immediately cooled with cooling water to stop the reaction. Next, the mixed solution after the reaction was diluted 10 times and filtered through a 0.2 μm filter. A reaction product was thus obtained. The amount of the reaction product was measured by high performance liquid chromatography (HPLC).

In order to identify the reaction product, ¹ H-NMR and ¹³ C-NMR were measured after purification of the reaction product. For comparison, the same measurement was performed for commercially available levulinic acid (obtained from Tokyo Chemical Industry Co., Ltd.). About ¹ H-NMR, the measurement result of the reaction product is shown in FIG. 1 (a), and the measurement result of commercially available levulinic acid is shown in FIG. 1 (b). Moreover, about < ¹³ > C-NMR, the measurement result of a reaction product is shown to Fig.2 (a), and the measurement result of commercially available levulinic acid is shown to FIG.2 (b). As shown in FIGS. 1 and 2, the NMR spectrum of the reaction product was in good agreement with the NMR spectrum of commercially available levulinic acid, indicating that levulinic acid was synthesized.

  Although the details of the reaction mechanism of Experiment 1 are not clear, it is considered that the reaction shown in FIG. This reaction includes a dehydration reaction from fructose to hydroxymethylfurfural (HMF) and a hydration reaction from HMF to levulinic acid. This reaction produces a molar amount of formic acid that is approximately equal to levulinic acid. The reaction conditions, reaction rate, and yield of Experiment 1 are shown in Table 1.

  As shown in Table 1, by using Amberlyst 15 as a catalyst, levulinic acid could be synthesized in a high yield under mild reaction conditions.

(Experiment 2)
In Experiment 2, the experiment was performed in the same manner as in Experiment 1 except that the catalyst was changed. However, in Experiment 2, for the solid catalyst, the catalyst amount was 0.4 g, the reaction temperature was 393 K, and the reaction time was 12 hours or 24 hours.

In Experiment 2, as catalyst, was used Amberlyst 15, Nafion NR50, SBA-SO ₃ H, sulfuric acid 0.1M (0.1mol / L). The amount of sulfuric acid used was 1.2 mmol in terms of H ⁺ . Experimental conditions and experimental results are shown in Table 2. Table 2 also shows the results of measuring the ion exchange capacity (mmol H ⁺ / g) of Amberlyst 15, Nafion NR50, and SBA—SO ₃ H by a titration method. Reference numeral 17 is a control experiment using no catalyst.

  As shown in Table 2, by using Amberlyst 15, levulinic acid could be synthesized with a particularly high yield. Note that levulinic acid can be synthesized with high yield by using sulfuric acid as a catalyst, but the use of sulfuric acid has the above-mentioned problems.

  As shown in Table 2, Amberlyst 15 had higher catalytic activity than Nafion NR50. Amberlist 15 and Nafion NR50 have the structures shown in FIGS. 4A and 4B, respectively, and both contain a sulfo group. However, as shown in Table 2, their ion exchange capacities (acid group amounts) are different. Moreover, as shown in Table 3 below, the specific surface area and acidity function of the two are different. These differences in physical properties may affect the difference in catalyst activity.

(Experiment 3)
In Experiment 3, a reaction for synthesizing levulinic acid was performed under the same conditions as in Experiment 1 (however, the amount of Amberlyst 15 was 0.4 g and the reaction temperature was 393 K). Then, Amberlyst 15 separated by filtration after the reaction was washed three times with 5 mL of water and then twice with 5 mL of acetone to remove organic compounds adhering to the catalyst. Thereafter, it was washed again with 5 mL of water and immersed in 2.5 mL of 1 M (1 mol / L) sulfuric acid at 318 K (45 ° C.) for 4 hours. Finally, it was washed twice with 5 mL of water and dried overnight at 318K. In this way, the amber list 15 was reproduced, and levulinic acid was synthesized six times using the same amber list 15. The fructose reaction rate and the yields of levulinic acid and HMF at that time are shown in FIG. As shown in FIG. 5, the amber list 15 showed sufficient catalytic activity by being regenerated by a simple regeneration method.

  The present invention can be used for the production of levulinic acid. Fructose is abundant in woody biomass (which is synthesized from sunlight, water and carbon dioxide). The method for producing levulinic acid of the present invention that does not use enzymes or microorganisms is considered to open up the possibility of chemical synthesis from biomass and contribute to the construction of a society that does not depend on petroleum.

R. A. Schraufnagel, H. F. Rase, Ind. Eng. Chem., Prod. Res. Dev., 1975, Vol. 14, p.40-44

In the method of Non-Patent Document 1 using an ion exchange resin as a catalyst, sucrose is converted into levulinic acid and hydroxymethylfurfural (HMF), but it requires a very long reaction time, and the yield of the product is also high. not high. In the method of Patent Document 1, the reaction is performed at a high temperature (for example, 150 ° C.).

Claims (5)

A method for producing levulinic acid, comprising:
Comprising a reaction step of producing levulinic acid by heating an aqueous solvent comprising a solid catalyst and fructose,
The solid catalyst is a polymer having a sulfo group;
A method for producing levulinic acid, wherein the reaction step is performed at a temperature of less than 150 ° C.   The production method according to claim 1, wherein the reaction step is performed at a temperature in the range of 100 to 140 ° C.   The production according to claim 1 or 2, wherein the solid catalyst is a polymer containing a structural unit derived from a vinyl aromatic compound, and a sulfo group is bonded to a benzene ring derived from the vinyl aromatic compound. Method. The solid catalyst is a polymer including a plurality of structural units derived from a plurality of vinyl aromatic compounds,
The manufacturing method according to claim 1 or 2, wherein the plural types of structural units include a structural unit derived from divinylbenzene and a structural unit derived from styrene having a sulfo group introduced into a benzene ring.   The manufacturing method of any one of Claims 1-4 whose said aqueous solvent is water.

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