JP2895087B2 - Method for separating lignocellulosic material into polyphenol and carbohydrate and polyphenolic material obtained by this method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wood or lignocellulosic material comprising carbohydrates and polyphenols such as lignin,
The present invention relates to a method for rapidly and quantitatively separating components into their constituents at room temperature without inactivating the components.

In recent years, interest in renewable biomass as a raw material for the chemical industry has increased due to reflection on the oil-dependent society. However, lignocellulosic materials, such as wood, are a complex of carbohydrates and lignins that have completely different structures and properties, and in order to achieve full effective utilization of the components, the wood must first be separated into its components. Is required. From this viewpoint, recently, an organosolve method, a solvolysis method, or a pretreatment method such as an explosion crushing method and an autohydrolysis method have been proposed as component separation techniques.
However, component separation by these methods requires high energy, and the separation does not proceed completely. This is due to the complex intertwining of carbohydrates and lignin at the molecular level in the cell wall. Therefore, to achieve complete component separation, it is necessary to disrupt the cell wall structure at the molecular level.

One method of destroying the wood tissue structure at the molecular level is treatment with concentrated acid. For example, the treatment with concentrated sulfuric acid causes the cellulose to swell, further causing partial hydrolysis and dissolution, resulting in the destruction of the cell wall structure. The method of hydrolyzing wood with concentrated sulfuric acid is almost established in the art, and the present method is a perfect and inexpensive method in terms of component separation. However, as a component separation method aiming at complete utilization of wood, acid hydrolysis method,
It has the serious disadvantage of inactivating lignin by condensation. This type of highly condensed lignin has a rigid molecule,
Usually, activation by structural modification or depolymerization thereof is difficult, which is one reason that the wood industry centering on acid hydrolysis has not been established until now.

The present invention provides a combination of destruction of tissue structure based on swelling of carbohydrates with concentrated acid and solvation of lignin with phenol derivatives, thereby inactivating lignin, which is a drawback of using wood by conventional acid hydrolysis treatment. Hold down,
The present invention relates to a technique for rapidly separating a lignocellulosic substance into its constituent components.

Lignin inactivation during the concentrated acid treatment process is based on the absence of a medium for lignin in the reaction system. Phenol derivatives, such as cresol, are good solvents for lignin, and their reactivity is similar to that of lignin aromatic nuclei. In addition, cresol does not mix with concentrated acids.

The wood flour is first treated with cresol, and cresol is sufficiently penetrated into the wood flour. Thereafter, the concentrated acid is added while the mixture is vigorously stirred at room temperature. Concentrated acids have a high affinity for carbohydrates, and cellulose swells quickly, which destroys the tissue structure. Cresol, on the other hand, has a high affinity for lignin and always coexists with lignin in the reaction system. In other words, the lignin is surrounded by cresol, which is always immiscible with the concentrated acid, thereby minimizing contact between the acid and the lignin. In addition, lignin is partially depolymerized in the treatment process, and the carbonium ion generated at that time is rapidly stabilized by cresol, and self-condensation of lignin is suppressed. After the treatment, the reaction mixture is quickly separated into a cresol layer and an aqueous layer by stopping the stirring. Lignin is contained in the cresol layer, and carbohydrates are present in the aqueous layer. By removing cresol, lignin which is lighter and more active than MWL (Milled Wood Lignin) can be obtained. On the other hand, the carbohydrate in the acid solution is converted into a monosaccharide useful as an industrial raw material by continuing the treatment.

 Hereinafter, the method of the present invention will be described in detail with reference to examples.

Example 1 10 and 20% of cresol and 72% sulfuric acid were added to wood flour.
(Ml / g), and the mixture was stirred at room temperature. As shown in Table 1, the lignin yield was already 10 minutes after the treatment.
Reaches 8% (vs. lignin). Moreover, the separated lignin is very bright and active, and easily dissolves in various solvents such as methanol and ethanol.

Example 2 When the addition ratio of cresol was changed to 20 to 3 (3 ml / g) under the conditions of 20% of sulfuric acid 20 (ml / g) and room temperature for 60 minutes with respect to wood powder (Table 2), cresol was added. At a rate of 5 or more, the lignin yield is almost constant. That is, with the addition of a small amount of cresol, the self-condensation of lignin is suppressed, and the separation proceeds efficiently.

Example 3 In the case where the 72% sulfuric acid addition rate was changed from 2 to 20 (ml / g) under the conditions of cresol 10 (ml / g), room temperature and 60 minutes for wood flour (Table 3), At a rate of 5 or more, there is no significant difference in lignin yield. That is, complete swelling and dissolution of the carbohydrate is not required for rapid separation.

Example 4 The blending ratio of cresol and sulfuric acid to wood flour, respectively
Under the conditions of 10 and 20 (ml / g), room temperature and 60 minutes,
When changed to 60-72% (Table 4), the lignin yield is very low at 60% temperature due to incomplete swelling of the carbohydrates. Lignin separation is promoted by 65% sulfuric acid,
The molecular weight of lignin is still high. Lignin yield is further increased by 72% sulfuric acid, and the molecular weight of lignin is also greatly reduced. That is, for rapid separation, it is important to loosen the association of the components by swelling of the carbohydrate and to partially depolymerize lignin.

In the treatment process according to the present method, lignin is depolymerized by cleavage of the ether bond, and cresol is introduced into the active position of the side chain, so that the reactivity of lignin as a phenolic compound is dramatically increased by separation.

Since the separation of the components of the lignocellulosic material by the present method involves the destruction of the tissue structure based on the swelling of the carbohydrate by the concentrated acid, the present method is applicable to any kind of biomass, and perfect separation is obtained.

Claims (5)

(57) [Claims] A method for separating a lignocellulosic material into a polyphenolic material and a carbohydrate by adding and mixing an acid to a lignocellulosic material to which a phenol derivative has been added. 2. The method according to claim 1, wherein said acid is 65% by weight or more of concentrated sulfuric acid. 3. The method according to claim 1, wherein the phenol derivative is cresol. 4. The method according to claim 1, wherein the mixing is performed without heating. 5. A polyphenol-based substance obtained by the method according to claim 1.