Method for producing purified wood vinegar

Abstract

To provide a method for producing purified wood vinegar.SOLUTION: A method for producing purified wood vinegar comprises: a first step of obtaining an upper layer liquid by contacting crude wood vinegar with a chlorine-containing organic solvent and performing liquid-liquid separation; and a second step of removing the dissolved chlorine-containing organic solvent from the upper layer liquid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing purified wood vinegar, which can be used for cosmetics, antibacterial agents, pharmaceuticals, processed foods, etc. [Background technology]

[0002] It has been common practice to obtain charcoal or activated carbon from raw materials such as driftwood, living wood, thinned wood, bamboo such as Madake bamboo and Moso bamboo, and plant-based materials (biomass) such as Tsushima bamboo and Kuma bamboo. Patent Document 1 discloses an apparatus developed for this purpose.

[0003] When plant materials are carbonized, the resulting vapor is cooled to obtain crude wood vinegar. Crude wood vinegar is a mixture of light oil, wood vinegar, and wood tar, and is an aqueous solution containing approximately 200 organic components, including carboxylic acids such as acetic acid, alcohols, esters, and phenols. Therefore, crude wood vinegar, either as is or after purification, can be used as a fertilizer, plant activator, soil conditioner, antibacterial agent, bath additive, deodorizer, etc.

[0004] Patent Document 2 describes a first contact step in which crude wood vinegar containing at least an active ingredient and a biohazardous substance is brought into contact with an organic solvent to transfer the active ingredient to the organic solvent, resulting in a two-phase state consisting of an organic solvent phase containing the active ingredient and an aqueous solution phase in which the biohazardous substance remains; In the method for producing purified wood vinegar, the method includes a separation and recovery step of separating and recovering the organic solvent phase, and an evaporation step of evaporating the organic solvent from the organic solvent phase to obtain an active ingredient-containing liquid containing the active ingredient, and a second contact step of contacting the active ingredient-containing liquid with camellia oil to obtain a mixed liquid. A method for producing purified wood vinegar is disclosed, which comprises a heating step of heating the mixed liquid.

[0005] However, the method described in Patent Document 2 is a method for extracting the active ingredients contained in crude wood vinegar into an organic solvent, and does not disclose the separation of wood tar while leaving behind components such as acetic acid contained in crude wood vinegar. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-338513 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-137834 Summary of the Invention [Problem to be solved by the invention]

[0007] Pyrovine vinegar can be separated from wood tar, an oily component, by leaving the crude wood vinegar to stand. Removal of wood tar from the wood vinegar is important because wood tar contains large amounts of aromatic compounds that pose safety concerns.

[0008] However, in liquid-liquid separation, the separability at the interface between the wood vinegar, which forms the aqueous phase, and the wood tar, which forms the oil layer, is extremely low. Therefore, it takes a very long time to separate the wood vinegar and the wood tar by leaving them to stand, and in normal separation procedures, components of the wood tar often become mixed into the aqueous phase consisting of the wood vinegar. This is a major problem in the industrial production of wood vinegar.

[0009] Extraction methods using solvents have also been proposed, but when using a toluene solvent, for example, acetic acid easily dissolves in the solvent layer, so acetic acid, a useful component contained in wood vinegar, is lost from the wood vinegar during the extraction process.

[0010] In view of the above circumstances, the present invention provides a method for producing purified wood vinegar by removing wood tar from crude wood vinegar with good operability. [Means for solving the problem]

[0011] The present invention provides a method for producing purified wood vinegar, which comprises a first step of contacting crude wood vinegar with a chlorine-containing organic solvent, followed by liquid-liquid separation to obtain a supernatant liquid, and a second step of distilling off the dissolved chlorine-containing organic solvent from the supernatant liquid. As the chlorine-containing organic solvent, dichloromethane and chloroform are preferred, with dichloromethane being particularly preferred. [Effects of the Invention]

[0012] The production method of the present invention has the excellent effect of easily removing wood tar from crude wood vinegar and preventing the loss of acetic acid components contained in the wood vinegar, thereby enabling the production of purified wood vinegar with useful applications. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a simplified diagram of the tube furnace test apparatus used in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The crude wood vinegar used as the raw material is a mixture of a liquid produced when plant-based material (biomass) is carbonized and a liquid obtained by cooling the resulting vapor. Woody materials are suitable as plant-based materials, and examples of woody materials include wood scraps, wood flour, and sawdust. White pellets are preferably prepared by pulverizing wood and compressing it under pressure into cylindrical shapes with a diameter of 6 to 8 mm and a length of 5 to 40 mm. The biomass can be carbonized under any conditions that block oxygen, such as under a nitrogen or argon flow. The dried biomass is then heat-treated at a maximum temperature of 250°C to 700°C.

[0015] Crude wood vinegar is an aqueous mixture containing wood tar and a small amount of diesel fuel. The chemical components of crude wood vinegar vary slightly depending on the raw material to be carbonized and the carbonization conditions, but the main substances are acetic acid, propionic acid, acetone, furfural, maltol, phenol, cresol, tannins, methanol, and formaldehyde. Of these, acetic acid is a useful component in applications. Therefore, when purifying crude wood vinegar, it is important not to remove the acetic acid but to leave it in the wood vinegar.

[0016] In the first step of the present invention, crude wood vinegar is contacted with a chlorine-containing organic solvent and subjected to liquid-liquid separation to obtain an upper layer liquid. The operation of contacting crude wood vinegar with a chlorine-containing organic solvent and performing liquid-liquid separation can be performed by a method known as an extraction operation. Although it can be performed by a batch operation, continuous operation is preferable industrially. A known method can be used for liquid-liquid separation. It is preferably performed at a temperature above the freezing point and below the boiling point of the extraction solvent, more preferably 10°C to 30°C. Furthermore, from the viewpoint of promoting liquid-liquid separation, it is preferable to leave the mixture to stand for a certain period of time after the contact. For example, it is preferable to leave it to stand for 1 minute or more, but it may also be left to stand for 2 minutes or more, 3 minutes or more, 5 minutes or more, or 10 minutes or more.

[0017] The chlorine-containing organic solvent acts as an extraction solvent to extract wood tar contained in the crude wood vinegar in a suspended or dissolved state. The amount of the chlorine-containing organic solvent used relative to the crude wood vinegar is preferably 1:5 to 30:1, more preferably 1:1 to 10:1, in terms of volume ratio (solvent / crude wood vinegar).

[0018] The wood tar contained in crude wood vinegar usually has a relatively higher specific gravity than water. Therefore, by using a chlorine-containing organic solvent having a significantly higher specific gravity than water, the wood tar is easily extracted into a lower layer consisting of the chlorine-containing organic solvent together with a small amount of light oil components. This allows the wood tar to be removed from the upper layer of wood vinegar by good liquid-liquid separation without disturbing the interface.

[0019] The first step of the present invention is characterized in that the acetic acid component contained in the aqueous phase is unlikely to migrate to the organic phase consisting of the chlorine-containing organic solvent. This is another advantage of using a chlorine-containing organic solvent as an extraction solvent in the purification of wood vinegar.

[0020] As the chlorine-containing organic solvent for extracting the oily component, dichloromethane and chloroform are preferable because they are relatively safe and easily available. A mixed solvent of dichloromethane and chloroform may also be used. In particular, using dichloromethane as the chlorine-containing organic solvent is preferable because it facilitates the second step of distilling off the solvent.

[0021] The chlorine-containing organic solvent is recovered from the lower layer liquid consisting of the organic phase obtained by liquid-liquid separation, preferably by distillation. The recovered chlorine-containing organic solvent can be reused in the first step for producing new crude wood vinegar. The wood tar remaining in the distillation process contains aromatic hydrocarbons and phenols and can be used as is or after fractionation in antiseptic paints and chemicals.

[0022] In the second step, the chlorine-containing organic solvent dissolved in a small amount in the supernatant liquid separated in the first step is distilled off. The distillation is carried out by aerating or heating the supernatant liquid to volatilize the chlorine-containing organic solvent. In this step, dichloromethane and chloroform can be easily distilled off. Dichloromethane is particularly preferred as it has a low boiling point of about 40°C and can be more easily distilled off.

[0023] The aeration operation is carried out by passing a gas such as air through the upper layer liquid. The heating operation is carried out by applying heat to the upper layer liquid. In this case, it is preferable to liquefy and recover the evaporated chlorine-containing organic solvent by cooling. The recovered chlorine-containing organic solvent can be reused as the extraction solvent to be used in the first step.

[0024] The purified wood vinegar obtained by the present invention is substantially free of wood tar and effectively contains acetic acid, and therefore can be used in cosmetics, antibacterial agents, pharmaceuticals, processed foods, etc. [Example]

[0025] Example 1 A plate containing 100 parts by weight of white pellets obtained by drying wood chips at 110°C for 1 hour was placed in the center of the quartz tube of the tubular furnace test apparatus shown in Figure 1, and both ends were secured with quartz wool. After purging the quartz tube with nitrogen, the center of the quartz tube was heated from room temperature to 600°C at a rate of 10°C per minute using an electric heater while nitrogen was flowing at a rate of 100 mL / min. After reaching 600°C, the temperature was maintained for 5 minutes. The nitrogen was then cooled in a collection bottle immersed in an ice-water bath to condense the organic components, after which it was released. After cooling to room temperature, the liquid oil mixture consisting of the mixture of the water phase and the oil phase was collected from the quartz tube and the collecting bottle and combined, and the solid char was collected from the quartz tube.

[0026] The resulting oil mixture was added with an equal volume of dichloromethane as an extraction solvent, and the mixture was shaken and left to stand in a separatory funnel for 10 minutes, resulting in the formation of a clear interface between the upper aqueous phase and the lower organic phase. The liquid-liquid separation was successful, yielding a lower organic phase and an upper aqueous phase. A small amount of dissolved dichloromethane was distilled off by passing air bubbles through the resulting aqueous phase, to obtain purified wood vinegar. The lower organic phase was heated under reduced pressure to remove dichloromethane and obtain wood tar.

[0027] The purified wood vinegar and wood tar obtained were qualitatively analyzed for their components using gas chromatography / mass spectrometry (GC / MS). Among the components, furfural and hydroxyacetone were quantified using the internal standard method using a gas chromatograph. Formic acid and acetic acid were quantified using an ion chromatograph (ICS-90, manufactured by DIONEX). Water content was quantified using Karl Fischer volumetric titration (JIS K 2275-2). The results are summarized in Table 1.

[0028] Example 2 Except for using the same volume of chloroform instead of dichloromethane as the extraction solvent, the same operation as in Example 1 was carried out. A clear interface was formed between the upper aqueous phase and the lower organic phase, and the liquid-liquid separation operation was successfully carried out. Next, purified pyroligneous acid, wood tar, and char were obtained by the same procedures as in Example 1, and the contents of each component were determined. The results are summarized in Table 1.

[0029] Comparative Example 1 Except for using the same volume of toluene instead of dichloromethane as the extraction solvent, the same operation as in Example 1 was carried out. The interface between the upper organic phase and the lower aqueous phase was not clear, and the liquid-liquid separation operation could not be carried out satisfactorily. Next, purified pyroligneous acid, wood tar, and char were obtained by the same procedures as in Example 1, and the contents of each component were determined. The results are summarized in Table 1.

[0030] [Table 1]

[0031] When dichloromethane or chloroform was used as the extraction solvent, the acetic acid component was retained in the purified wood vinegar more than when toluene was used. In addition, the interface between the aqueous and organic phases was clear, and the liquid-liquid separation operation was performed smoothly. [Industrial Applicability]

[0032] The method of the present invention can be used to produce purified wood vinegar.

Claims

1. A method for producing purified wood vinegar comprising a first step of contacting crude wood vinegar with a chlorine-containing organic solvent and then obtaining a supernatant liquid by liquid-liquid separation, and a second step of distilling off the dissolved chlorine-containing organic solvent from the supernatant liquid.

2. 2. The method for producing purified wood vinegar according to claim 1, wherein the chlorine-containing organic solvent is dichloromethane or chloroform.

3. 2. The method for producing purified wood vinegar according to claim 1, wherein the chlorine-containing organic solvent is dichloromethane.

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