JP6372925B2 - Method for producing lignophenol - Google Patents

Description

  The present invention relates to a method for producing lignophenol, in which lignophenol is obtained by reacting lignin contained in a lignocellulosic material such as a woody material with phenols.

  Conventionally, a method for producing lignophenol is known in which a woody material containing lignin, an inorganic acid such as sulfuric acid, and phenols are brought into contact with each other to produce lignophenol in which lignin and phenols have reacted.

  This type of lignophenol production method includes a reaction step in which a wood material, a sulfuric acid aqueous solution and a phenol are brought into contact with each other to obtain a solution containing lignophenol, and a sodium carbonate solution or a potassium carbonate solution is added to the solution after the reaction step. An alkali neutralization step in which an aqueous solution of alkali metal carbonate such as is added to neutralize, and then separated into a solution portion and an insoluble portion, and an insoluble portion obtained in the alkali neutralization step is in a range of 0.1N to 1N. And an acid treatment step of separating and purifying insoluble lignophenols by dispersing in an acid solution and stirring, and then washing with water (Patent Document 1).

  However, the production method described in Patent Document 1 has a problem that the obtained lignophenol contains a relatively large amount of inorganic components derived from inorganic acids as impurities.

Japanese Patent No. 3956047

  This invention makes it a subject to provide the manufacturing method of lignophenol which can obtain lignophenol which has comparatively few inorganic components as an impurity in view of said problem.

In order to solve the above problems, a method for producing lignophenol according to the present invention comprises a reaction step of bringing lignin, sulfuric acid, and phenols into contact with each other to obtain lignophenol in which lignin and phenols have reacted; A solid salt of the sulfuric acid and the alkaline earth metal is generated by mixing a lignophenol solution in which the lignophenol is dissolved in the first solvent to be dissolved and an alkaline earth metal hydroxide. A salt generation step, and a precipitation step of precipitating lignophenol by mixing a lignophenol solution from which the generated salt has been removed and a second solvent having a lower lignophenol solubility than the first solvent. It is characterized by that.
In the method for producing lignophenol having the above structure, a solid inorganic salt can be produced by the salt production step. Thereby, solid inorganic salt and lignophenol in a dissolved state can be separated. The amount of inorganic components can be reduced as much as the solid inorganic salt is separated. Therefore, lignophenol having relatively few inorganic components as impurities can be obtained.

In the method for producing lignophenol of the present invention, it is preferable that the pH of the lignophenol solution after mixing the alkaline earth metal hydroxide is adjusted to be acidic in the salt generation step.
Thereby, there is an advantage that a solid inorganic salt can be generated more reliably, and lignophenol having fewer inorganic components as impurities can be obtained.

In the method for producing lignophenol of the present invention, after the salt production step, the lignophenol solution from which the produced salt has been removed is mixed with a second solvent having a lower lignophenol solubility than the first solvent. The method further comprises a precipitation step of precipitating lignophenol . Thereby, solid lignophenol can be obtained .

  As described above, the method for producing lignophenol of the present invention has an effect that lignophenol having relatively few inorganic components as impurities can be obtained.

The figure which represents an example of reaction in the reaction process typically. The flowchart which shows the process in an Example. The graph showing the total sulfur concentration contained in each manufactured lignophenol.

  Hereinafter, an embodiment of a method for producing lignophenol according to the present invention will be described in detail.

  The method for producing lignophenol according to the present embodiment includes a reaction step of bringing lignin, an inorganic acid, and phenols into contact with each other to obtain lignophenol in which lignin and phenols have reacted, and a first solvent that dissolves the lignophenol. A salt generation step of generating a solid salt of the inorganic acid and the alkaline earth metal by mixing a lignophenol solution in which the lignophenol is dissolved and an alkaline earth metal hydroxide; Is provided.

  Preferably, the method for producing lignophenol of the present embodiment includes the reaction step, the salt generation step, a salt removal step of removing the salt generated by the salt generation step from the lignophenol solution, and the salt removal step of the salt. A precipitation step of precipitating lignophenol by mixing the lignophenol solution after removing the lignophenol and a second solvent having a lower lignophenol solubility than the first solvent.

The inorganic acid used in the reaction step is preferably at least one selected from the group consisting of sulfuric acid, hydrochloric acid, and phosphoric acid, and sulfuric acid is used . Hereinafter, the case where sulfuric acid is used as the inorganic acid will be described in detail.

  In the reaction step, for example, lignin, sulfuric acid, and phenols are brought into contact with each other by mixing a material containing lignin, an aqueous solution containing sulfuric acid, and phenols. Thereby, sulfuric acid becomes a catalyst and lignin and phenols react. In addition, hydrolysis reaction proceeds with sulfuric acid, and lignin is reduced in molecular weight. While the lignin is reduced in molecular weight, phenols are bonded to the α-position carbon of the phenylpropane unit which is a structural unit of lignin. An example of the reaction in the reaction step is schematically shown in FIG. In addition, a reaction process is normally implemented at room temperature.

  Lignin is a polymer compound having a phenylpropane unit (C6-C3 unit) as a basic skeleton, and the phenylpropane unit is randomly oxidatively polymerized by an enzyme. Lignin is a component constituting a plant cell wall, and is bound to cellulose or hemicellulose in the plant cell wall.

  The material containing lignin is usually a lignocellulosic material containing at least cellulose and lignin. The material containing lignin is, for example, a woody material or a herbaceous material. Examples of the woody material include coniferous trees such as pine, cedar and cypress, broad-leaved trees such as shii, oak and cherry, or tropical trees. Herbaceous materials include kenaf, ramie (flax), linen (flax), abaca (manila hemp), heneken (sisal hemp), jute (hemp), hemp (palm), palm, palm, mulberry, straw, bagasse, corn, etc. Is mentioned. The material containing lignin is used in various states such as powder and chips (for example, waste wood scraps).

The aqueous solution containing sulfuric acid usually contains 65 mass% or more and 98 mass% or less of H ₂ SO ₄ . The aqueous solution containing sulfuric acid preferably contains 72% by mass or more and 98% by mass or less of H ₂ SO ₄ .

  Phenols are compounds having a phenol structure in the molecule. Phenols include phenol, o (ortho) -cresol, m (meth) -cresol, p (para) -cresol, anisole, 2,4-dimethoxyphenol, 2,6-dimethoxyphenol, 2,4-dimethylphenol. 2,6-dimethylphenol, propylphenol, i-propylphenol, tert-butylphenol, catechol, resorcinol, pyrogallol, phloroglucinol, bisphenol, vanillin, syringol, guaiagol, ferulic acid, and coumaric acid At least one selected is preferred. As the phenol, cresol such as m (meth) -cresol or p (para) -cresol is preferable.

In the reaction step, the concentration of sulfuric acid (H ₂ SO ₄ ) in the mixed solution when the material containing lignin, the aqueous solution containing sulfuric acid, and the phenol are mixed may be 69% by mass or more and 75% by mass or less. preferable. When the concentration of sulfuric acid (H ₂ SO ₄ ) in the mixed solution is 69% by mass or more, hydrolysis reaction in the reaction process or addition reaction of phenols to the phenylpropane unit of lignin proceeds more reliably. There is an advantage of doing. When the concentration of sulfuric acid (H ₂ SO ₄ ) in the mixed solution is 75% by mass or less, sulfonation of lignin can be suppressed, and there is an advantage that the yield and quality of lignophenol become better.

In the reaction step, it is preferable to mix the material containing lignin and the aqueous solution containing sulfuric acid so that the mass ratio of sulfuric acid (H ₂ SO ₄ ) to lignin is 6 to 30 times. In the reaction step, the material containing lignin and the phenols are preferably brought into contact with each other so that the mass ratio of the phenols to lignin is 1 to 4 times.
The amount of lignin contained in the material containing lignin can be determined by the Klarson method (sulfuric acid method). For example, when the material containing lignin is a conifer, the mass ratio as described above is set by defining the lignin content of the conifer as 30% by mass. When the lignin-containing material is hardwood, the mass ratio as described above is set by defining the lignin content of hardwood as 20% by mass (reference: chemistry of lignin; Junzo Nakano, Uni Publication).

  Lignophenol obtained in the reaction step is a compound having a 1,1-bis (aryl) propane structure in which a phenol derivative is bonded to the C1 position of the phenylpropane skeleton of lignin. The molecular weight of lignophenol is usually 1,000 to 20,000. Lignophenol does not include only a single compound, but includes the above-mentioned compounds having different molecular weights.

  Specifically, in the reaction step, for example, wood powder from which oils and fats have been removed by being placed in an organic solvent such as acetone is used as a material containing lignin. Next, phenols such as cresol are sorbed onto the wood powder from which the oil and fat have been removed. Subsequently, about 70% by mass of concentrated sulfuric acid is added to the wood powder sorbed with phenols and mixed. Finally, the mixture is diluted with water to stop the hydrolysis reaction with sulfuric acid.

  In the production method of the present embodiment, a liquid hydrocarbon (a nonpolar solvent such as n-hexane) is added to the solution after the reaction step, and the mixture is allowed to stand for a long time (for example, 12 hours). It can be divided into a layer containing phenol (hereinafter also referred to as lignophenol-containing liquid) and an aqueous layer containing sulfuric acid. Thereby, most of the sulfuric acid can be distributed to the aqueous layer, and the amount of sulfuric acid contained in the lignophenol-containing liquid can be relatively reduced. Moreover, nonpolar components other than lignophenol can be distributed to said hydrocarbon layer. The lignophenol-containing liquid can be used in the subsequent salt generation step. In addition to lignophenol, the lignophenol-containing liquid may contain a relatively small amount of sulfuric acid and unreacted substances that have not reacted (such as carbohydrates such as cellulose).

  In the salt production step, a lignophenol solution containing a first solvent in which lignophenol is dissolved and lignophenol dissolved in the first solvent is prepared. Specifically, a lignophenol solution is prepared by mixing the first solvent and the above-described layer containing lignophenol obtained in the reaction step (lignophenol-containing liquid). In the salt generation step, an alkaline earth metal hydroxide is further added to the lignophenol solution and mixed. Thereby, a solid salt of sulfuric acid and alkaline earth metal is generated. In addition, a salt production | generation process is normally performed at room temperature.

  The first solvent is a solvent that dissolves lignophenol. The first solvent is not particularly limited as long as it is a solvent that dissolves lignophenol. The first solvent is preferably a compound represented by a molecular formula composed of C (carbon), H (hydrogen), and at least one of O (oxygen) and N (nitrogen). The first solvent is preferably a polar organic solvent. It is preferable that a 1st solvent is a solvent which mutually melt | dissolves in the arbitrary ratio with the 2nd solvent mentioned later.

  Examples of the first solvent include alkyl ketones, aprotic polar solvents, cyclic ethers, heterocyclic compounds, alcohols and the like. The first solvent is usually an organic solvent.

Examples of alkyl ketones include acetone and methyl ethyl ketone.
Examples of the aprotic polar solvent include dimethylformamide (DMF) and N-methylpyrrolidone (NMP).
Examples of cyclic ethers include tetrahydrofuran (THF), dioxane and the like.
Examples of the heterocyclic compound include pyridine.
Examples of alcohols include methanol, ethanol, cellosolve and the like.
As the first solvent, alcohols are preferable, and methanol as alcohols is more preferable.

  The first solvent is preferably at least one selected from the group consisting of methanol, ethanol, acetone, methyl ethyl ketone, dioxane, pyridine, tetrahydrofuran, and dimethylformamide.

  The lignophenol solution prepared in the salt generation step usually contains 10% by mass to 35% by mass of lignophenol. For example, the lignophenol solution can be prepared so that the lignophenol concentration is 10% by mass or more and 35% by mass or less. The lignophenol concentration can be calculated, for example, from the amount of lignophenol precipitated in the subsequent precipitation step.

  In the salt generation step, it is preferable to use 1 to 10 parts by mass of the first solvent with respect to 1 part by mass of lignophenol. By using 1 mass part or more of 1st solvent with respect to 1 mass part of lignophenol, there exists an advantage that lignophenol can be dissolved more fully. By using 10 mass parts or less of 1st solvent with respect to 1 mass part of lignophenol, there exists an advantage that said salt can be produced | generated without using the 1st solvent exceeding a required amount.

  Examples of the alkaline earth metal hydroxide include magnesium hydroxide and calcium hydroxide. As the alkaline earth metal hydroxide, magnesium hydroxide is preferable because impurities contained in the obtained lignophenol can be reduced.

In the salt generation step, the pH of the lignophenol solution after adding the alkaline earth metal hydroxide is preferably adjusted to be acidic, and more preferably adjusted to 2 or more and 4 or less. Acidity means that the pH is less than 6. By adjusting the pH after addition of the alkaline earth metal hydroxide to be acidic, there is an advantage that the above-mentioned salt can be generated while suppressing decomposition of lignophenol.
The pH can be adjusted by changing the amount of alkaline earth metal hydroxide added. Specifically, since the lignophenol solution contains sulfuric acid used in the reaction process, the pH of the lignophenol solution is adjusted by changing the amount of alkaline earth metal hydroxide (basic) added. it can. In addition, since a lignophenol solution contains the water | moisture content produced | generated by said reaction process, even if a 1st solvent is an organic solvent, predetermined pH is shown.

  In the salt generation step, it is preferable to mix more alkaline earth metal hydroxide than the upper limit amount dissolved in the lignophenol solution with the lignophenol solution. That is, it is preferable to add excess alkaline earth metal hydroxide to the lignophenol solution. The alkaline earth metal hydroxide is preferably in the form of particles having a particle size of about 1 μm. The amount of alkaline earth metal hydroxide added is excessive, and the alkaline earth metal hydroxide is in particulate form as described above. There is an advantage that the oxide can be easily removed from the lignophenol solution. In addition, it is preferable that the alkaline earth metal hydroxide has a smaller particle size in that the reactivity with sulfuric acid is further increased.

The salt produced in the salt production step is an alkaline earth metal salt (inorganic salt). Specifically, it is a sulfate such as magnesium sulfate or calcium sulfate.
By the salt production step, the above-mentioned salt is produced in the lignophenol solution. Such a salt is insoluble because it has very low solubility in the first solvent. Thereby, the lignophenol in a dissolved state can be separated from the inorganic salt (sulfate) that has become insoluble. As the solid sulfate is separated, the sulfuric acid component can be reduced. Further, the sulfate can be easily removed from the lignophenol solution by a salt removal step described later. In addition, since the salt produced | generated at a salt production | generation process is magnesium sulfate or calcium sulfate, a salt is produced | generated by the particle shape with a comparatively large particle size. Thereby, there exists an advantage that a sulfate can be more easily removed from a lignophenol solution by the salt removal process mentioned later.

  In the salt removal step, the produced solid salt is removed from the lignophenol solution. For example, the solid salt can be removed from the lignophenol solution by filtration, centrifugation, or the like.

  In the precipitation step, the dissolved lignophenol is mixed by mixing the lignophenol solution after removing the produced sulfate and the second solvent having a lower lignophenol solubility than the first solvent. In the liquid after mixing, it is precipitated. Thereby, solid lignophenol can be obtained.

  The second solvent has a lignophenol solubility lower than that of the first solvent lignophenol. The second solvent is not particularly limited as long as the solubility of lignophenol is a solvent as described above. The second solvent is preferably a compound represented by a molecular formula composed of C (carbon) and H (hydrogen). The second solvent is preferably a nonpolar organic solvent. The second solvent is preferably a solvent that dissolves in any proportion with the first solvent described above.

Examples of the second solvent include alkyl ethers, alkyl esters, cyclic hydrocarbons, linear hydrocarbons, and aqueous solutions containing 90% by mass or more of water.
Examples of alkyl ethers include tert-butyl methyl ether (TBME), cyclopentyl methyl ether (CPME), diethyl ether, dipropyl ether, and diisopropyl ether.
Examples of the alkyl esters include ethyl acetate and n-butyl acetate.
Examples of cyclic hydrocarbons include toluene, xylene, cyclohexane and the like.
Examples of linear hydrocarbons include n-hexane and pentane.
Examples of the aqueous solution containing 90% by mass or more of water include pure water and a sodium chloride aqueous solution having a concentration of 0.1% by mass to 10% by mass.

  The second solvent is preferably at least one selected from the group consisting of an aqueous solution containing 90% by mass or more of water, n-hexane, n-pentane, heptane, octane, cyclohexane, decalin, and benzene. The second solvent is preferably an organic solvent.

  In the precipitation step, it is preferable to use 100 parts by mass or more and 1000 parts by mass or less of the second solvent with respect to 100 parts by mass of the lignophenol solution from which the sulfate has been removed in the salt removal step. By using 100 parts by mass or more of the second solvent with respect to 100 parts by mass of the lignophenol solution, there is an advantage that lignophenol can be precipitated more reliably. By using 1000 parts by mass or less of the second solvent with respect to 100 parts by mass of the lignophenol solution, there is an advantage that lignophenol can be precipitated without using a second solvent exceeding the necessary amount.

  The lignophenol obtained by the production method of this embodiment is used in applications such as a flame retardant for plastics, a plywood adhesive, and an impregnating material.

  In the above description, the case where sulfuric acid is used as the inorganic acid in the reaction step has been described in detail. In the manufacturing method of this embodiment, hydrochloric acid or phosphoric acid can also be used as an inorganic acid in the reaction step. Even when hydrochloric acid or phosphoric acid is used as the inorganic acid in the reaction step, a solid chloride salt or phosphate can be generated in the salt generation step. Similarly, lignophenol having relatively few inorganic components as impurities can be obtained.

The method for producing lignophenol of the present embodiment is as illustrated above, but the present invention is not limited to the above-described examples.
Moreover, the various aspects used in the manufacturing method of general lignophenol can be employ | adopted in the range which does not impair the effect of this invention.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

(Example)
A method for producing lignophenol was carried out as follows. Specifically, lignophenol was produced using a wood material containing lignin and cellulose. The process flow is shown in FIG.
-Pretreatment In order to remove the oil and fat contained in the softwood (cedar) wood flour, the wood flour was put in acetone. Acetone was volatilized from the wood flour by drying. Thus, the wood powder from which the oil and fat content was removed was prepared. After adding p-cresol (7.5 g) and acetone (33 g) to the wood flour (7.5 g) from which the oil and fat have been removed, the acetone is distilled off by drying under reduced pressure, and p-cresol is sorbed onto the wood flour. I let you.
-Reaction process 61 g of 72 mass% sulfuric acid aqueous solution was added to 15 g of wood flour in a state where p-cresol was sorbed and stirred vigorously for 1 hour.
The reaction process was stopped by adding 12.8 g of water.
105 g of n-hexane was added to the liquid after the reaction step, and after vigorous stirring, the mixture was allowed to stand overnight, and separated into three layers of an n-hexane layer, a lignophenol layer, and a sulfuric acid layer due to the difference in specific gravity. After removing the n-hexane layer and the sulfuric acid layer, the lignophenol layer was taken out.
-Salt production | generation process Lignophenol layer and methanol (55g) as a 1st solvent were mixed, and lignophenol was dissolved in methanol. Insoluble matter not dissolved in methanol was removed by suction filtration to obtain 50 g of lignophenol solution. The pH was adjusted to 3.08 by adding an excessive amount of magnesium hydroxide (powder having an average particle diameter of 1 μm) to this lignophenol solution. As a result, solid sulfate (magnesium sulfate) was produced in the lignophenol methanol solution.
-Salt removal process Excess magnesium hydroxide and the produced sulfate were removed by suction filtration.
-Precipitation process The lignophenol solution from which the sulfate and excess magnesium hydroxide have been removed is dropped into a 0.5 mass% saline solution (second solvent) 5 times the mass of the lignophenol solution to precipitate lignophenol. It was. The precipitated lignophenol was separated by suction filtration using a filter paper and dried at 50 ° C. overnight to produce a solid lignophenol.

(Comparative Example 1)
In the salt production step, lignophenol was produced in the same manner as in Example, except that instead of using powdered magnesium hydroxide, the pH of the lignophenol solution was adjusted to 2.9 using an aqueous 15N potassium hydroxide solution. did.

(Comparative Example 2)
In the salt production step, lignophenol was used in the same manner as in the above example except that instead of using powdered magnesium hydroxide, the pH of the lignophenol solution was adjusted to 3.0 using a 15N aqueous sodium hydroxide solution. Manufactured.

<Analysis of impurities in lignophenol>
The total sulfur concentration (correlated with the sulfate ion concentration) in the solid lignophenol obtained by drying was measured by ion chromatography after pretreatment by tubular furnace combustion.
Moreover, each of the lignophenol solution before pH adjustment (before magnesium hydroxide addition), the lignophenol solution after pH adjustment, and the lignophenol solution after removing magnesium hydroxide and the produced sulfate in the salt generation step, respectively. The sulfate ion concentration was measured by the electrocapillary method.
The particle size of lignophenol precipitated in the precipitation step was measured by laser diffraction / scattering particle size distribution measurement.
The analysis results are shown in Table 1. Moreover, the analysis result of the total sulfur concentration is shown in FIG.

  As can be seen from the above results, lignophenol having relatively few sulfuric acid components (inorganic components) as impurities can be obtained by the method for producing lignophenol of the examples.

  The method for producing lignophenol of the present invention can be suitably used to obtain, for example, a relatively high purity lignophenol. The lignophenol obtained in the present invention can be suitably used as an additive to plastics, an adhesive or an impregnating material for building materials.

Claims (2)

A reaction step of bringing lignin, sulfuric acid and phenols into contact with each other to obtain lignophenol in which lignin and phenols have reacted;
By mixing a lignophenol solution in which the lignophenol is dissolved in a first solvent in which the lignophenol is dissolved, and an alkaline earth metal hydroxide, a solid state of the sulfuric acid and the alkaline earth metal is mixed. A salt production step for producing a salt;
A precipitation step of precipitating lignophenol by mixing the lignophenol solution from which the generated salt has been removed and a second solvent having a lower lignophenol solubility than the first solvent;
A process for producing lignophenol. The method for producing lignophenol according to claim 1, wherein in the salt generation step, the pH of the lignophenol solution after mixing the alkaline earth metal hydroxide is adjusted to be acidic.