Method for producing lignophenol

Abstract

The objective is to provide a method for producing lignophenol that allows for rapid separation of lignophenol from an aqueous phase containing acid. [Solution] The problem is solved by a method for producing lignophenol, which includes the step of mixing a lignophenol-containing solution with a mixed solvent containing an alkane or cycloalkane having 5 to 10 carbon atoms and an alcohol, ketone, or ester having 5 to 10 carbon atoms to obtain a mixed solution.

Description

[Technical Field]

[0001] This invention relates to a method for producing lignophenols. [Background technology]

[0002] Lignocellulose, which makes up the cell walls of plants, is a polymer mixture formed by the bonding of polysaccharides such as cellulose and hemicellulose with lignin. Lignin, isolated from lignocellulose, is a high-molecular-weight phenolic compound with a three-dimensional network structure. Although lignin accounts for approximately 30% of wood by weight, effective utilization methods have not been established until now, and much of it has been discarded.

[0003] In recent years, methods for producing chemically stable lignophenols have been investigated by reacting lignocellulose materials containing lignin with phenols by adding an acid in a solubilized state. Patent Document 1 discloses a method for producing lignophenols comprising: a first mixing step of obtaining a first mixture by mixing a lignocellulose material, a phenol derivative, and an acid; a second mixing step of obtaining a second mixture containing lignophenol aggregates by mixing the first mixture and a solvent that is a poor solvent for lignophenol to cause lignophenol to aggregate; a filtration step of filtering the second mixture to remove the lignophenol aggregates from the second mixture; and a washing step of washing the lignophenol aggregates by adding water to the lignophenol aggregates filtered out in the filtration step. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-64533 [Overview of the project] [Problems that the invention aims to solve]

[0005] In the method described in Patent Document 1, obtaining the second mixture containing lignophenol aggregates was time-consuming and resulted in significant losses during separation. The object of this invention is to provide a method for producing lignophenol that allows for the rapid extraction of lignophenol from a lignophenol-containing solution. [Means for solving the problem]

[0006] As a result of diligent research by the inventors, it was discovered that by adding a specific mixed solvent to a lignophenol-containing solution, lignophenol and an aqueous phase containing acid can be rapidly separated, leading to the present invention.

[0007] In other words, the present invention is as follows: [1] A method for producing lignophenol, comprising the steps of mixing a lignophenol-containing solution with a mixed solvent containing an alkane or cycloalkane having 5 to 10 carbon atoms and an alcohol, ketone, or ester having 5 to 10 carbon atoms to obtain a mixed solution. [2] The lignophenol-containing solution is obtained by a step of mixing a lignin-containing raw material, a phenol compound, and an acid to obtain a lignophenol-containing solution, as described in [1]. [3] The mixture is allowed to stand and separated into a solid phase containing lignophenol, an organic phase, and an aqueous phase, and The manufacturing method according to [1] or [2], comprising the step of recovering the solid phase. [4] The manufacturing method according to any one of [1] to [3], wherein in the mixed solvent, the ratio of the alkane or cycloalkane having 5 to 10 carbon atoms to the alcohol, ketone, or ester having 5 to 10 carbon atoms is 8:1 to 1:5 by weight. [5] The solubility of water in the C5-C10 alcohol, ketone, or ester is 0.0001-5 mol / dm³ 3 The manufacturing method described in any of [1] to [4]. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a production method capable of rapidly extracting lignophenol from a lignophenol-containing solution.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the present invention will be described in detail by showing embodiments, examples, etc., but the present invention is not limited to the following embodiments, examples, etc., and can be arbitrarily modified and implemented without departing from the gist of the present invention. In this specification, the description of "XX or more and YY or less" or "XX to YY" representing a numerical range means a numerical range including the lower limit and the upper limit which are endpoints, unless otherwise specified. When numerical ranges are described stepwise, the upper and lower limits of each numerical range can be arbitrarily combined. Further, in the present disclosure, a description such as "at least one selected from the group consisting of XX, YY, and ZZ" means any one of XX, YY, ZZ, a combination of XX and YY, a combination of XX and ZZ, a combination of YY and ZZ, or a combination of XX, YY, and ZZ.

[0010] One embodiment of the present invention includes a step of mixing a lignophenol-containing solution and a mixed solvent containing an alkane or cycloalkane having 5 to 10 carbon atoms and an alcohol, ketone, or ester having 5 to 10 carbon atoms to obtain a mixed liquid, and is a method for producing lignophenol.

[0011] The lignophenol-containing solution contains lignophenol. The solvent is not particularly limited, but is usually water. The lignophenol-containing solution can be obtained by a step of mixing a lignin-containing raw material, a phenolic compound, and an acid to obtain a lignophenol-containing solution. By mixing the lignin-containing raw material, the phenolic compound, and the acid, lignin is hydrolyzed and reduced in molecular weight in the presence of an acid catalyst, and lignin reacts with the phenolic compound in the presence of an acid catalyst to produce lignophenol. That is, the lignophenol-containing solution may contain lignin, a phenolic compound, and an acid in addition to lignophenol.

[0012] Lignin is generally a polymer with a crosslinked structure having hydroxyphenylpropane units as basic units. Lignophenol means a polymer containing diphenylpropane units in which phenols (phenolic compounds) are introduced at the α-position of the side chain of the phenylpropane unit of lignin by a C-C bond.

[0013] The lignin-containing raw material is a material containing lignin, and preferably a lignocellulosic material. A lignocellulosic material is a material containing lignin, cellulose, and hemicellulose. Examples of lignocellulosic materials include woody materials and herbaceous materials. Examples of woody materials include conifers (pine, cedar, cypress, etc.), broad-leaved trees (oak, persimmon, cherry, etc.), tropical trees, etc. Examples of herbaceous materials include kenaf, ramie, linen (flax), abaca (Manila hemp), henequen (sisal hemp), jute, hemp, coconut, palm, mulberry, straw (rice straw, wheat straw, etc.), bagasse, corn, etc. Lignocellulosic materials are used in various states such as powdery and chip-like (such as the ends of waste wood). and the like.

[0014] Further, the lignocellulosic material may be one obtained by performing a degreasing treatment on the above-mentioned woody material and herbaceous material. The degreasing treatment can be performed by a known method. For example, 2 kg to 10 kg of acetone is added to 1 kg of the lignocellulosic material and filtered to obtain a lignocellulosic material subjected to the degreasing treatment.

[0015] The phenol compound is not particularly limited, but examples include at least one phenol compound selected from the group consisting of p-cresol, m-cresol, o-cresol, anisole, 2-naphthol, 2,4-dimethylphenol, 2,6-dimethylphenol, 2-methoxyphenol, 2,4-dimethoxyphenol, 2,6-dimethoxyphenol, n-propylphenol, isopropylphenol, tert-butylphenol, catechol, resorcinol, homocatechol, pyrogallol, phloroglucinol, bisphenol, vanillin, syringol, and guaiacol. Among these, p-cresol is preferred. As an example, lignophenol obtained by introducing p-cresol into lignin includes a substructure represented by the following formula (1).

[0016] [ka]

[0017] The amount of phenol compound is not particularly limited, but typically 0.3 kg to 10 kg of phenol compound is used per 1 kg of lignin-containing raw material.

[0018] Examples of the aforementioned acid include inorganic acids and organic acids. Examples of the aforementioned inorganic acid include sulfuric acid, phosphoric acid, and hydrochloric acid. Examples of the aforementioned organic acid include p-toluenesulfonic acid, trifluoroacetic acid, trichloroacetic acid, and formic acid. Sulfuric acid is particularly preferred as the acid.

[0019] The amount of acid is not particularly limited, but typically 8 kg to 33 kg of an acidic aqueous solution containing acid is used per 1 kg of lignin-containing raw material. The acidic aqueous solution typically contains 65% to 98% by weight of acid, preferably 72% to 98% by weight.

[0020] The temperature at which the lignin-containing raw material, phenol compound, and acid are mixed and reacted is not particularly limited, but may be between 20°C and 40°C, or between 25°C and 35°C. In one example, the reaction temperature is 30°C.

[0021] The reaction time when mixing a lignin-containing raw material, a phenol compound, and an acid and allowing them to react is not particularly limited, but examples include 5 minutes to 72 hours, 10 minutes to 24 hours, or 30 minutes to 2 hours. From the viewpoint of reducing unreacted lignin, a longer reaction time is preferable, while from the viewpoint of reducing manufacturing costs, a shorter reaction time is preferable.

[0022] The amount of lignophenol contained in the lignophenol-containing solution is not particularly limited, but is usually 0.5% to 10% by weight, and preferably 1% to 5% by weight. The lignophenol-containing solution may contain unreacted phenol compounds because the above reaction did not proceed. The amount of phenol compounds included is not particularly limited, for example, 0% to 60% by weight, preferably 0.1% to 30% by weight, and more preferably 1% to 10% by weight. The amount of acid contained in the lignophenol-containing solution is not particularly limited, but is usually 0% to 95% by weight, preferably 20% to 95% by weight, and more preferably 40% to 80% by weight.

[0023] In this embodiment, C5-C10 alkanes or cycloalkanes are used. The C5-C10 alkanes may be chain-like or branched, and are preferably chain-like. Specifically, examples include pentane, hexane, heptane, octane, nonane, and decane. Here, pentane is not limited to n-pentane and includes isomers. The same applies to hexane, heptane, octane, nonane, and decane. That is, the C5-C10 alkanes may be branched alkanes such as 2-methylpentane. n-hexane is preferred as the C5-C10 alkane. Examples of cycloalkanes having 5 to 10 carbon atoms include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, and cyclodecane. Cyclopentane or cyclohexane are preferred as the cycloalkane having 5 to 10 carbon atoms. Alternatively, ligroin may be used as the alkane or cycloalkane having 5 to 10 carbon atoms. Ligroin is a mixture mainly composed of alkanes having 7 carbon atoms and cyclohexane.

[0024] The solubility of water in the alkane or cycloalkane having 5 to 10 carbon atoms is preferably low. When the solubility of water is low, lignophenol and the aqueous phase can be efficiently separated. The solubility of water in the alkane or cycloalkane having 5 to 10 carbon atoms is 0.01 mol / dm 3 or less, preferably, and more preferably 0.005 mol / dm 3 or less. The lower limit is not particularly limited, but examples thereof include 0.0001 mol / dm 3 or more and 0.001 mol / dm 3 or more. That is, the solubility of water in the alkane or cycloalkane having 5 to 10 carbon atoms may be 0.0001 mol / dm 3 or more and 0.01 mol / dm 3 or less, or 0.001 mol / dm 3 or more and 0.005 mol / dm 3 or less.

[0025] In the present specification, the solubility of water in an organic solvent such as the above alkane can be measured, for example, as follows. Put 15 mL each of an organic solvent and an aqueous phase (0.1 mol / dm 3 HClO4) into a 50 mL centrifuge tube with a stopper. Shake and mix at 150 times / min for 1 hour in a constant temperature bath at 25°C. After centrifuging at 3000 rpm for 5 minutes, let stand in a constant temperature bath at 25°C for about 1 hour. Take an appropriate amount of the organic phase and measure the concentration of water in the organic solvent by Karl Fischer coulometric titration.

[0026] In this embodiment, C5-C10 alcohols, ketones, or esters are used. The C5-C10 alcohol may be monohydric or polyhydric, and is preferably a monohydric alcohol. Specifically, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol This includes one or more substances selected from the group consisting of tanol, 3-octanol, 1-nonanol, 2-nonanol, and 3-nonanol.

[0027] Examples of ketones having 5 to 10 carbon atoms include one or more selected from the group consisting of 2-pentanone, 3-pentanone, 2-hexanone, 2-octanone, 4-methyl-2-pentanone, and 5-methyl-2-hexanone. Examples of esters having 5 to 10 carbon atoms include one or more selected from the group consisting of propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, heptyl acetate, octyl acetate, ethyl propionate, propyl propionate, butyl propionate, pentyl propionate, hexyl propionate, methyl butyrate, butyl butyrate, pentyl butyrate, and hexyl butyrate. Preferably, propyl acetate, butyl acetate, pentyl acetate, or hexyl acetate.

[0028] Among these, propyl acetate, butyl acetate, pentyl acetate, hexyl acetate, 2-hexanone, 2-octanone, 4-methyl-2-pentanone, 5-methyl-2-hexanone, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, or 1-nonanol are preferred, and 2-octanone, 1-hexanol, propyl acetate, or 4-methyl-2-pentanone are particularly preferred.

[0029] The ratio of a C5-C10 alkane or cycloalkane to a C5-C10 alcohol, ketone, or ester in the mixed solvent is not particularly limited, but is preferably 8:1-1:5 by weight, more preferably 6:1-1:4, even more preferably 5:1-1:1, and particularly preferably 5:1-3:1. When the ratio is within this range, lignophenols can be extracted efficiently.

[0030] The solubility of water in the aforementioned C5-C10 alcohol, ketone, or ester is preferably low. Low solubility of water allows for efficient separation of lignophenol from the aqueous phase. The solubility of water in the aforementioned C5-C10 alcohol, ketone, or ester is 5 mol / dm³. 3 The following is preferable: 4 mol / dm 3 It is more preferable that the following is the case: 3.5 mol / dm 3 It is even more preferable that the following conditions apply: 1 mol / dm 3 The following is particularly preferable. Furthermore, the lower limit is not particularly limited, but is 0.0001 mol / dm³. 3 More than 0.001mol / dm 3 More than 0.01mol / dm 3 The above can be stated. That is, the solubility of water in the aforementioned C5-C10 alcohols, ketones, or esters is 0.0001 mol / dm³. 3 More than 5mol / dm 3 The following is acceptable: 0.001 mol / dm³ 3 More than 4mol / dm 3 The following is acceptable: 0.01 mol / dm³ 3 More than 3.5mol / dm 3 The following is acceptable: 0.01 mol / dm³ 3 More than 1mol / dm 3 The following is acceptable:

[0031] The E of the aforementioned C5-C10 alcohol, ketone, or ester TThe value is not particularly limited, but is preferably 35 kcal / mol or more and 60 kcal / mol or less, and more preferably 40 kcal / mol or more and 55 kcal / mol or less. T The value represents the solvation ability of the solvent to the negative charge, and is 2,6-diphenyl-4-(2,4,6-triphenylpyridio)phenolate (E T 30) is the value calculated by dividing by 28591 by the absorption maximum wavelength of the intramolecular charge transfer absorption band when used as the substrate molecule. T If the value is within the above range, solvation of lignophenol is possible.

[0032] The mixing ratio of the lignophenol-containing solution to the mixed solvent is preferably 5:1 to 1:10 by weight, more preferably 4:1 to 1:5, and particularly preferably 3:1 to 1:1. A larger amount of mixed solvent facilitates separation, while a smaller amount of mixed solvent reduces costs.

[0033] By mixing a lignophenol-containing solution with a mixed solvent and allowing the resulting mixture to stand, it rapidly separates into an organic phase containing the mixed solvent and an aqueous phase containing acid, cellulose, etc., and a solid phase containing lignophenol precipitates at the interface between the organic and aqueous phases. The solid phase containing lignophenol can be extracted from the lignophenol-containing solution by recovering the solid phase using known methods such as a separatory funnel, centrifugation, and filtration. Furthermore, the manufacturing method of this embodiment can reduce costs compared to prior art such as Patent Document 1 because it allows for the extraction of the solid phase containing lignophenol without centrifugation.In addition, in prior art such as Patent Document 1, lignophenol forms sticky aggregates during separation, which may cause clogging during filtration.However, in the manufacturing method of this embodiment, lignophenol is recovered as a solid phase, thus suppressing clogging during filtration. In other words, the manufacturing method of this embodiment may include the steps of letting the mixture stand and separating it into a solid phase containing lignophenol, an organic phase, and an aqueous phase, and recovering the solid phase. The solid phase may also be subjected to a washing step in which water is added and filtered to obtain a solid phase, and / or a drying step such as vacuum drying.

[0034] The manufacturing method of this embodiment may include a step of obtaining a lignophenol extract by adding an extraction solvent to a solid phase containing lignophenol and filtering it. This makes it possible to remove components insoluble in the extraction solvent from the solid phase containing lignophenol. Examples of components insoluble in the extraction solvent include carbohydrates such as hemicellulose. The extraction solvent is not limited to any solvent in which lignophenol is soluble, and examples include one or more selected from the group consisting of alcohols (methanol, ethanol, etc.), ketones (acetone, methyl ethyl ketone, etc.), dioxane, pyridine, tetrahydrofuran, and dimethylformamide. Acetone or methyl ethyl ketone is preferred as the extraction solvent. The amount of extraction solvent to be added is not particularly limited, but it can range from 5 kg to 15 kg per 1 kg of solid phase containing lignophenol.

[0035] The manufacturing method of this embodiment may include a step of obtaining solid lignophenol by adding an aqueous sodium chloride solution to an acetone solution containing lignophenol, crystallizing the lignophenol, and then filtering it. Lignophenols are highly protic due to the OH groups in their phenol skeleton, resulting in high water solubility. However, the aqueous solution of lignophenols becomes less soluble in the presence of sodium chloride. Specifically, when an aqueous sodium chloride solution is added to an acetone solution containing lignophenol, the lignophenol crystallizes.

[0036] The sodium chloride concentration of the added sodium chloride aqueous solution is not particularly limited, but is typically between 0.01% and 1% by weight, preferably between 0.06% and 0.3% by weight, and more preferably between 0.15% and 0.2% by weight.

[0037] The amount of sodium chloride aqueous solution to be added is not particularly limited, but it can range from 5 kg to 20 kg per 1 kg of lignophenol extract.

[0038] The temperature during crystallization is not particularly limited and may be between 3°C and 30°C, for example, 25°C.

[0039] The resulting solid lignophenol can be subjected to a drying process as needed. It may also be further purified by known methods. [Examples]

[0040] The present invention will be described in more detail by examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0041] 5 g of wood flour was mixed with 5 g of p-cresol (Wako) and 160 g of 72% sulfuric acid (Wako), and the mixture was reacted at 30°C for 1 hour. As a result, lignin was separated from the wood flour and reacted with p-cresol to produce lignophenol, yielding a lignophenol-containing solution.

[0042] The solvents listed in Table 1 were mixed in the proportions shown in Table 2 to obtain a mixed solvent. 36 g of the mixed solvent was added to 13 g of a lignophenol-containing solution, gently stirred, and then allowed to stand. The time required for the organic phase and aqueous phase to separate visually is shown in Table 2. [Table 1] [Table 2]

[0043] As shown in Table 2, Comparative Example 1, in which no solvent was added during separation, required a long time for separation. In Comparative Example 2, in which hexane was added during separation, separation took 30 minutes, and the phase containing lignophenol formed a viscous aggregate, making recovery difficult. In contrast, in Examples 1 to 8, in which a mixed solvent was added, the solid phase containing lignophenol separated between the organic phase and the aqueous phase and could be easily recovered by filtration.

Claims

1. A method for producing lignophenol, comprising the steps of mixing a lignophenol-containing solution with a mixed solvent containing an alkane or cycloalkane having 5 to 10 carbon atoms and an alcohol, ketone, or ester having 5 to 10 carbon atoms to obtain a mixed solution.

2. The manufacturing method according to claim 1, wherein the lignophenol-containing solution is obtained by a step of mixing a lignin-containing raw material, a phenol compound, and an acid to obtain a lignophenol-containing solution.

3. The process involves allowing the mixture to stand and separating it into a solid phase containing lignophenol, an organic phase, and an aqueous phase, and The manufacturing method according to claim 1 or 2, comprising the step of recovering the solid phase.

4. The manufacturing method according to claim 1 or 2, wherein in the mixed solvent, the ratio of the alkane or cycloalkane having 5 to 10 carbon atoms to the alcohol, ketone, or ester having 5 to 10 carbon atoms is 8:1 to 1:5 by weight.

5. The solubility of water in the aforementioned C5-C10 alcohols, ketones, or esters is 0.0001-5 mol / dm ３ The manufacturing method according to claim 1 or 2.

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