JP2010150159A - New method for producing levulinic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing levulinic acid from 3-carboxymuconolactone as a starting substance. <P>SOLUTION: This method for producing the levulinic acid represented by formula (2) comprises alkali-hydrolyzing 3-carboxymuconolactone in an alkali aqueous solution and then acidifying the obtained hydrolysis solution with a strong acid into acidity of ≤pH 1 to perform decarbonation and keto-enol tautomerization. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing levulinic acid as a final product by decarboxylation by alkaline hydrolysis and acidic treatment and ketoenol tautomerization using 3-carboxymuconolactone as a starting material.

  Today, various polymers such as polyethylene, polypropylene, polyvinyl chloride, and polyethylene terephthalate are widely used for molded products such as various containers, garbage bags, packaging bags, and the like. However, since these polymers are mainly made from petroleum, if they are incinerated at the time of disposal, they increase carbon dioxide in the atmosphere and contribute to global warming. On the other hand, when landfilled without incineration, there are many things that are hardly decomposed in the natural environment, so they remain in the ground semipermanently.

  In recent years, plant-derived polymers obtained through plant-derived raw materials and metabolism by microorganisms have attracted attention. Because these polymers are environmentally-circulating materials that do not use petroleum as a raw material, carbon dioxide fixed in plants is returned to the atmosphere. I won't let you. Even if landfilled without incineration, it is decomposed by microorganisms in the soil, so there is no risk of environmental destruction. Examples of such plant-derived polymers include polylactic acid, polyhydroxybutyric acid, and the like, and development of uses for various molded products is being promoted as a biodegradable material with future potential. However, such a plant-derived polymer has a problem of competing with food in supply when the raw material is food that is a grain containing starch or the like. This is a problem from the viewpoint of a stable supply of food to mankind.

  By the way, lignin, a plant-derived aromatic polymer compound, is a biomass resource that is universally contained in plant cell walls, but its chemical structure is composed of various components and has a complex polymer structure. Therefore, effective utilization technology has not been developed yet. Therefore, for example, lignin produced as a by-product in a large amount in the paper industry is not effectively used but is incinerated as an alternative fuel for heavy oil.

  In recent years, plant-derived aromatic components such as lignin have been converted into several small molecules by chemical decomposition methods such as hydrolysis, oxidative decomposition, solvolysis, or physicochemical decomposition methods using supercritical water or supercritical organic solvents. Methods have been developed to convert to a mixture of compounds to produce a single compound, 3-carboxymuconolactone. For example, an international publication WO 2008/018640 pamphlet (hereinafter referred to as Patent Document 1), a low molecular weight mixture containing vanillin, vanillic acid, and protocatechuic acid obtained by chemically decomposing a plant raw material containing lignin through a multi-stage enzymatic reaction. And a method for producing 3-carboxy-Cis, Cis-muconic acid and / or 3-carboxymuconolactone, which are single compounds.

  A lignin-containing plant that does not compete with food in supply if 3-carboxymuconolactone, a single compound thus obtained, can be used as a raw material for biodegradable plastics and various chemical products. The raw material (biomass) can be used effectively. However, a method for utilizing 3-carboxymuconolactone derived from lignin-containing biomass has not yet been established.

  By the way, levulinic acid is a chemical substance also called β-acetylpropionic acid and exists on a colorless plate or leaf-like crystals. Levulinic acid is a basic chemical substance that serves as a raw material for various useful chemical substances, and is a useful compound that is expected to have a large demand in the future. Levulinic acid is, for example, diphenolic acid used as a plastic raw material, succinic acid used as a food additive or polymer raw material, bioactive substance, herbicide, hair restorer, aminolevulinic acid, fuel additive, etc. It is used as a starting material for producing methyltetrahydrofuran used as an alternative fuel for gasoline and the like (refer to Patent Document 2 and Patent Document 3 below).

  Currently, levulinic acid is produced from carbohydrates such as sugar, starch and glucose as raw materials. For example, a method for producing levulinic acid by hydrolyzing sugar in the presence of an acid catalyst has been known for a long time ( (See Non-Patent Document 1 below). In addition, a method for producing a lembric acid ester by reacting a carbohydrate and an alcohol in the presence of a heteropoly acid is also known (see Patent Document 4 below).

  Levulinic acid is obtained by acid hydrolysis of cellulose-containing biomass or sugar derived therefrom, and such acid decomposition methods are described in, for example, International Publication WO89 / 10362, International Publication WO96 / 40609, US Pat. Nos. 892,107 and 6,054,611. When such an acid hydrolysis method is used, an aqueous mixture containing levulinic acid, formic acid, furfural (when C5 sugar-containing hemicellulose is present in the starting material), and an inorganic acid used as a hydrolysis catalyst is obtained. Generate. Also known is a method of separating and producing a levulinic acid ester from a levulinic acid-containing aqueous mixture by a reactive extraction method in which an aqueous mixture containing levulinic acid is contacted with a liquid alcohol (see Patent Document 5 below). )

  On the other hand, plant-based resources (lignocellulose) mainly composed of lignocellulose such as woody materials such as wood, bark and waste paper, agricultural products such as rice straw, fir and bagasse, and their wastes in organic solvents. A solvolysis reaction is also known in which the organic solvent used is treated and decomposed while binding to lignocellulose (see Patent Document 6 below). Also known is a method for suppressing the purification of the polycondensation compound by using ethylene glycol as a solvolysis reagent in a high proportion.

However, a method for producing levulinic acid using 3-carboxymuconolactone, which is a single compound derived from lignin-containing biomass, as a starting material is not yet known.
WO 2008/018640 pamphlet Japanese Patent Laid-Open No. 2003-226641 Special table 2007-510787 gazette JP 2006-206579 A JP-T-2007-518778 JP 2004-83482 A TR Frost and FF Kruth, TAPPI, 34, 80 (1951)

  The problem to be solved by the present invention is to provide a method for producing levulinic acid as a final product by decarboxylation and ketoenol tautomerization by alkaline hydrolysis and acid treatment using 3-carboxymuconolactone as a starting material. That is.

As a result of repeating experiments and intensive studies to solve the above-mentioned problems, the present inventor has finally obtained 3-carboxymuconolactone as a starting material by alkaline hydrolysis and decarboxylation by acidic treatment and ketoenol tautomerism. The actual levulinic acid was manufactured, the manufacturing method was established, and the present invention was completed.
That is, the present invention is the following [1] to [5]:

で表される３−カルボキシムコノラクトンを、アルカリ水溶液中でアルカリ加水分解し、次いで、得られた加水分解溶液を強酸でｐＨ１以下の酸性にして、脱炭酸及びケトエノール互変異性化することにより、以下の式（２）：

で表されるレブリン酸を、製造する方法。 [1] The following formula (1):

3-carboxymuconolactone represented by the following formula: The following formula (2):

The method to manufacture the levulinic acid represented by these.

[2] The method according to [1], wherein the alkaline aqueous solution is a 1N aqueous sodium hydroxide solution.

[3] The method according to [1] or [2], wherein the alkali hydrolysis is performed in a temperature range of 60 to 105 ° C. and in an air atmosphere.

[4] The method according to any one of [1] to [3], wherein the strong acid is HCl.

[5] The method according to any one of [1] to [4], further comprising: extracting the levulinic acid as a final product with an ethyl acetate solution after acidifying the hydrolyzed solution with a strong acid to pH 1 or lower. the method of.

Hereinafter, the present invention will be described in more detail.
The reaction scheme of the method for producing levulinic acid according to the present invention is shown below:

  The method for obtaining 3-carboxymuconolactone as a starting material is not limited, but 3-carboxymuconolactone contains, for example, vanillin, vanillic acid, protocatechuic acid, etc. as disclosed in Patent Document 1 described above. A multi-stage culture of a transformant into which a benzaldehyde dehydrogenase gene (ligV gene), a vanillate dimethylase gene (vanAB gene), and a protocatechuate 3,4-dioxygenase gene (pcaHG gene) were introduced from a plant-derived low molecular weight compound mixture The 3-carboxy-Cis, Cis-muconic acid is obtained through the enzymatic reaction, and can be obtained by treating with a strong acid and ring-closing.

  In the first step of the above reaction, 3-carboxymuconolactone, which is a starting material, is dissolved in an aqueous alkali solution and stirred in a temperature range of about 60 to 105 ° C. and in an air atmosphere to give 3-carboxymuconolactone. The lactone is alkali hydrolyzed. The alkali used for the alkali hydrolysis is an inorganic alkali or organic alkali such as sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, ammonia, hydrazine, sodium bicarbonate, sodium borate, etc. Can do. The organic alkali is preferably one that can be easily separated from the reaction product levulinic acid. The aqueous alkaline solution can preferably be a 1N aqueous sodium hydroxide solution. The amount of alkali used for the alkali hydrolysis can be sufficient to make the pH of the alkaline aqueous solution of 3-carboxymuconolactone 10 or more.

  In addition, it can replace with the said alkali hydrolysis and can also use acid hydrolysis. The acid used for the acid hydrolysis can be an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, or an organic acid. The organic acid is preferably one that can be easily separated from the reaction product levulinic acid. The amount of the acid used for the acid hydrolysis may be sufficient to bring the pH of the acidic aqueous solution of 3-carboxymuconolactone to about 3.

  The reaction temperature can be a reflux temperature, for example, about 80 ° C. The reaction atmosphere can be an air atmosphere. The alkali hydrolysis time can be 1 to 12 hours, for example, about 3 to 6 hours.

  In the second stage of the above reaction, the resulting hydrolysis solution is acidified with a strong acid to pH 1 or lower, whereby decarboxylation and ketoenol tautomerization are performed, and an alkaline hydrolysis product of 3-carboxymuconolactone Is converted to levulinic acid. As a strong acid to be used, for example, HCl can be mentioned.

  The inventors of the present invention do not wish to be bound by a specific theory, but one molecule of 3-carboxymuconolactone hydrolyzate undergoes two molecules of decarboxylation and keto isomerization. Presumed to be converted to levulinic acid. However, it cannot be denied that one molecule of decarboxylation has already been carried out in the hydrolysis of the first stage, and the remaining one molecule of decarboxylation has been carried out during acidification at a pH of 1 or less with a strong acid in the second stage. . In any case, as demonstrated in the following examples, 3-carboxymuconolactone is converted to levulinic acid through alkaline hydrolysis, acidification at pH 1 or lower with a strong acid, and a two-step reaction. .

  In some cases, in the third stage of the above reaction, the hydrolyzed solution can be acidified with a strong acid to pH 1 or less, and then the final product, levulinic acid, can be extracted with an ethyl acetate solution.

  The extraction solvent may be any solvent as long as it can dissolve and purify levulinic acid, and examples thereof include chloroform and diethyl ether.

The invention will now be illustrated by non-limiting examples.
Example 1
To a 100 ml flask, 1.00 g (9 mmol) of 3-carboxymuconolactone was added, and 100 ml of 1N sodium hydroxide aqueous solution was added to 3-carboxymuconolactone and stirred to obtain a solution. After confirming that 3-carboxymuconolactone was completely dissolved in the sodium hydroxide solution, an alkaline hydrolysis reaction was performed for 6 hours while refluxing at 80 ° C. in an air atmosphere. Next, after the obtained hydrolysis solution was adjusted to pH 1 or less with HCl, ethyl acetate was added thereto, and extraction with an ethyl acetate solution was performed three times. The obtained ethyl acetate solution phase was dehydrated with magnesium sulfate, and then ethyl acetate was distilled off to obtain 690 mg of levulinic acid (yield 92.8%).

It was confirmed by GC-MASS, ¹ H-NMR, and ¹³ C-NMR measurement that the final product of the reaction was levulinic acid having a molecular weight of 116.
(1) GC-MASS measurement results: m / z = 188, 173, 145, 75
The molecular weight of 3-carboxymuconolactone is 158 and the molecular weight of levulinic acid is 116. Since the molecular weight of TMS-levulinic acid is 188, the presence of levulinic acid was confirmed by the presence of m / z = 188.
(2) ¹ H-NMR (500 MHz, DMSO-d ₆ ) δ (ppm): 2.09 (1H, s), 2.37 (3H, m), 2.65 (4H, m)
(3) ¹³ C-NMR (500 MHz, DMSO-d ₆ ) δ (ppm): 28.2, 30.3, 38.2, 174.3, 207.5

  Since the method for producing levulinic acid according to the present invention uses 3-carboxymuconolactone as a starting material, it contributes to effective utilization of lignin-containing biomass that does not compete with food.

Claims (5)

The following formula (1):

3-carboxymuconolactone represented by the following formula: The following formula (2):

The method to manufacture the levulinic acid represented by these.   The method according to claim 1, wherein the alkaline aqueous solution is a 1N sodium hydroxide aqueous solution.   The method according to claim 1 or 2, wherein the alkaline hydrolysis is performed in a temperature range of 60 to 105 ° C and in an air atmosphere.   The method according to any one of claims 1 to 3, wherein the strong acid is HCl.   The method according to any one of claims 1 to 4, further comprising the step of extracting the final product levulinic acid with an ethyl acetate solution after acidifying the hydrolysis solution with a strong acid to a pH of 1 or less.