JP2017189741A - Lignin flocculant, production method of the same and lignin recovery method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a more efficient lignin flocculant by a lignin production method and a lignin recovery method.SOLUTION: In a lignin flocculant containing cationized lignin in which a lignin part and a cationization agent part are essential: lignin is a lignin derivative obtained by the solvolysis of lignocellulose with at least one digestion solvent selected from among polyethylene glycol, diethylene glycol, ethylene glycol, glycerol and polyglycerol, enzyme lignin obtained by the enzyme saccharification of the lignocellulose or alkali lignin obtained by the alkali digestion of the lignocellulose; and a cationization agent is glycidyltrimethylammonium chloride. The lignin flocculant, a production method of the same and a lignin recovery method using the same are provided.SELECTED DRAWING: None

Description

  The present invention relates to a lignin flocculant for aggregating lignin and a method for producing the same. The present invention also relates to a lignin recovery method using a lignin flocculant.

  Lignin is one of the three major components of biomass and is the second most abundant organic compound on the ground. Although it is separated in the chemical pulping process and the bioethanol pretreatment process, it is produced as a by-product in paper pulp production and bioethanol production. However, there are few effective utilization methods other than heat sources, and the effective utilization method is being sought.

  Research and development of biorefinery using lignocellulose as a resource is underway. For example, in the plant scale, atmospheric pressure acid solvolysis using lignocellulose using a highly safe glycol-based drug such as polyethylene glycol (PEG) A method for decomposing by PEG cooking and separating pulp and lignin has been proposed (Non-patent Document 1). The lignin obtained by this method is a glycol lignin derivatized with a glycol-based drug, and retains the original properties of lignin and is imparted with thermal processability. Therefore, engineering plastics, various thermoplastic resins, films It can be used as a raw material for high value-added materials such as electronic substrates, fiber reinforcements, various adhesives, carbon fibers, activated carbon fibers, various carbon materials, chemical admixtures for concrete, dispersants, various surfactants, etc. . Therefore, the atmospheric pressure acid solvolysis method is also a method for producing a lignin derivative.

  In the normal pressure acid solvolysis method, lignin is contained in the filtrate recovered from the cooking step. For example, in a lab scale, lignin that is insoluble in water is precipitated as a precipitate by an operation such as dropping the filtrate into water. However, there is a need for more efficient lignin recovery methods on the plant scale.

Summary of the 2015 Lignin debate p104-105

  In the lignin production method, a more efficient lignin recovery method is required.

The present inventors have found that the cationized lignin obtained from lignin has an excellent lignin aggregation effect, and completed the present invention. That is, the present invention relates to the following.
1. It is a lignin flocculant containing a cationized lignin that essentially comprises a lignin site and a cationizing agent site.
2. The lignin is obtained by enzymatic saccharification of lignocellulose, a lignin derivative obtained by solvolysis of lignocellulose with at least one cooking solvent selected from polyethylene glycol, diethylene glycol, ethylene glycol, glycerin and polyglycerin. 2. The lignin flocculant according to 1 above, which is an alkaline lignin obtained by alkaline digestion of enzyme lignin or lignolrose.
3. 3. The lignin flocculant according to 1 or 2 above, wherein the cationizing agent is glycidyl trimethyl ammonium chloride.
4). A method for producing a lignin flocculant containing a cationized lignin, comprising reacting a lignin and a cationizing agent to obtain a cationized lignin.
5. It is a method for recovering lignin, which comprises aggregating lignin by adding the lignin flocculant described in 1-4 above to a solution containing lignin.
6). 6. The method for recovering lignin according to 5 above, wherein the pH of the solution containing lignin is 3 to 8.

  By using the cationized lignin of the present invention as a lignin flocculant, an excellent lignin aggregation effect can be obtained, and lignin can be recovered in a high yield from a solution containing lignin after cooking. According to the lignin recovery method using the lignin flocculant of the present invention, in order to achieve excellent lignin aggregation in the neutral region, the supernatant liquid after lignin recovery can be efficiently processed and reused.

Embodiment 1: Aggregating Agent Containing Cationized Lignin The aggregating agent of the present invention contains a cationized lignin that essentially comprises a lignin site and a cationizing agent site. In addition to these sites, other structural sites may be included.

  The lignin site is a structural unit derived from lignin. The lignin is not particularly limited. For example, alkaline lignin (lignin obtained by alkaline digestion of lignorulose), kraft lignin, acetate lignin, organosolv lignin, explosive lignin, sulfated lignin, enzyme lignin (lignocellulose) Lignin obtained by enzymatic saccharification) and the like, and one or more of these lignins can be used.

  As lignin, lignin obtained by solvolysis can also be used. Here, “solvolysis” refers to a chemical reaction when a substance is decomposed in an organic solvent reagent. At the same time as the substance is decomposed, the used solvent reagent and the decomposed substance are chemically bonded. It is a chemical reaction that proceeds while the solvent molecules are added to the degradation product. Through a solvolysis reaction, a large number of hydrophilic groups such as alcoholic hydroxyl groups and / or polyoxyalkylene groups derived from the decomposition reagent are introduced into the lignin in lignocellulose, and a lignin derivative having excellent heat melting properties is produced. . Such a solvolysis method is described in, for example, Japanese Patent No. 4025866.

  As an organic solvent reagent used for solvolysis, a high boiling point reagent such as polyethylene glycol (PEG), diethylene glycol, ethylene glycol, glycerin, polyglycerin and the like can be used. Preferably, the organic solvent reagent is mixed with an acid such as hydrochloric acid or sulfuric acid, and the lignocellulose is solvolyzed by heating at a temperature equal to or higher than the melting point of the decomposition reagent (for example, about 120 to 180 ° C.). By subjecting the solvolysis product obtained by the solvolysis treatment to, for example, dropwise addition to water, a water-insoluble lignin derivative is obtained as a precipitate. In addition, you may precipitate a lignin derivative from a solvolysis product using the lignin flocculant containing the cationized lignin obtained by this invention.

  The plant used as the raw material for the lignin is not particularly limited, and conifers such as cedar, fir, cypress, and pine, broad-leaved trees such as eucalyptus, acacia, birch, beech and oak, rice straw, cereal, bagasse, bamboo, kenaf, and straw Herbaceous plants and the like.

  The molecular weight of lignin varies depending on the raw material and the isolation method, and the weight average molecular weight of lignin used in the present invention is not particularly limited. For example, lignin having a weight average molecular weight of 500 to 1,000,000 can be used. Preferably, it is a lignin having a weight average molecular weight of 5000 to 100,000. The weight average molecular weight can be measured using gel permeation chromatography (GPC) analysis.

  The cationizing agent site in the cationized lignin of the present invention is a structural unit derived from the cationizing agent. The cationizing agent is a compound having a cationic group such as an ammonium group, an iminium group, a sulfonium group, or a phosphonium group and a salt thereof, and any one can be used as long as the cationic group can be introduced into lignin. Commercially available cationizing agents can be used as the cationizing agent, such as glycidyltrimethylammonium chloride (GTA), 3-chloro-2-hydroxypropyltrimethylammonium chloride, 3-chloropropyltrimethylammonium chloride, chlorocholine chloride, Quaternary ammonium salts such as acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyltrimethylammonium chloride, (3-acrylamidopropyl) trimethylammonium chloride, diallyldimethylammonium chloride, 1-allyl-3-methylimidazolium iodide , And glycidyldimethylammonium chloride, diphenyl-4-thiophenoxy phenylsulfonium chloride, (thiodi-1,4- Eniren) bis [diphenyl sulfonium] dichloride, tertiary sulfonium salts such as 3-chloropropyl dimethyl ammonium chloride can be used. From the viewpoint of availability and cost, glycidyltrimethylammonium chloride is preferred.

  The cationized lignin of the present invention is preferably one obtained by reacting 1 g of lignin with a cationizing agent of 1.5 milliequivalent or more. More preferably, the cationizing agent is reacted in an amount of 1.8 milliequivalents or more with respect to 1 g of lignin, and more preferably 2.2 milliequivalents or more of the cationizing agent is reacted with 1 g of lignin. Moreover, as an upper limit of the quantity of a cationizing agent, it is preferable that it is 5 equivalent or less with respect to 1 g of lignin, and it is more preferable that it is 4.1 equivalent or less. The equivalent here means how many moles of cationic groups are reacted with 1 g of lignin as a raw material.

  Although the following is considered about the mechanism by which lignin aggregates with the flocculant of this invention, it is not necessarily limited to this. Lignin is a polyphenolic substance and is anionic in an aqueous solution due to the presence of phenolic hydroxyl groups. In order to agglomerate such an anionic substance, a cationic functional group is usually required. However, when trimethylglycidylammonium chloride having a cationic functional group was used as an aggregating agent, lignin did not agglomerate, so aggregation was not possible simply by neutralizing the surface charge of lignin suspension particles in water. I understood it. This is presumably because the lignin particles are very fine and flocs until they are precipitated cannot be formed only by neutralizing the surface charge. On the other hand, the flocculant containing the cationized lignin of the present invention exhibits excellent lignin aggregation ability. This is because the cationic functional group in the cationized lignin neutralizes the surface charge of the lignin suspension particles in water, suppresses the repulsive action between the lignin particles and promotes the aggregation phenomenon, and at the same time, The lignin portion is adsorbed on the lignin particles, thereby acting as an adhesive, and is considered to be caused by aggregation between the lignin particles. Since the commercially available polymeric cationic flocculant (dimethylaminoethyl acrylate DAA manufactured by Kurita Kogyo Co., Ltd.) did not show the lignin aggregating ability as much as the cationized lignin of the present invention, the lignin portion in the cationized lignin This suggests that it is very important for adhesion between lignin particles.

Embodiment 2: Method for producing lignin flocculant containing cationized lignin The method for producing a lignin flocculant containing a cationized lignin of the present invention comprises reacting lignin and a cationizing agent to obtain a cationized lignin. In addition, the cationized lignin obtained by doing in this way is contained in the cationized lignin which essentially requires said lignin site | part and a cationization agent site | part. Therefore, description of the same contents as those of the flocculant containing the cationized lignin will be omitted as appropriate.

  The method for reacting lignin and the cationizing agent is not particularly limited. For example, lignin is dissolved in an alkaline aqueous solution (for example, NaOH aqueous solution), and a predetermined amount of the cationizing agent is added thereto, and the room temperature to 100 ° C. And reacting with stirring at a temperature of 30 minutes to 24 hours. After completion of the reaction, an insoluble matter can be removed from the reaction solution by filtration or the like as necessary, and the reaction solution can be concentrated or neutralized as necessary to obtain a flocculant containing a cationized lignin in a liquid state. . If necessary, a flocculant containing solid cationized lignin may be obtained by drying the reaction solution by freeze drying or the like. The flocculant containing cationized lignin may contain NaOH or inorganic salt derived from an alkaline aqueous solution, or unreacted lignin and / or a cationized compound.

  In the reaction of lignin with a cationizing agent, the cationized lignin of the present invention is preferably reacted with 1.5 milliequivalent or more of the cationizing agent with respect to 1 g of lignin. More preferably, the cationizing agent is reacted in an amount of 1.8 milliequivalents or more with respect to 1 g of lignin, and more preferably 2.2 milliequivalents or more of the cationizing agent is reacted with 1 g of lignin. Moreover, as an upper limit of the quantity of a cationizing agent, it is preferable that it is 5 equivalent or less with respect to 1 g of lignin, and it is more preferable that it is 4.1 equivalent or less. The equivalent here means how many moles of cationic groups are reacted with 1 g of lignin as a raw material.

Embodiment 3: A method for recovering lignin.
The flocculant containing the cationized lignin of the present invention can be used in a method for recovering lignin. The method for recovering lignin of the present invention includes adding the above-mentioned flocculant containing cationized lignin to a solution containing lignin to cause lignin to aggregate.

  Research and development of biorefinery using lignocellulose as a resource is underway. For example, in the plant scale, atmospheric pressure acid solvolysis using lignocellulose using a highly safe glycol-based drug such as polyethylene glycol (PEG) Has been proposed to separate pulp and lignin (Abstracts of the 2015 Lignin Discussion P104-105). In the normal pressure acid solvolysis method, lignin is contained in the filtrate recovered from the cooking step. For example, in a lab scale, lignin that is insoluble in water is precipitated as a precipitate by an operation such as dropping the filtrate into water. However, there is a need for more efficient lignin recovery methods on the plant scale.

  In the method for recovering lignin of the present invention, a flocculant containing cationized lignin is added to a filtrate containing lignin recovered in a normal pressure acid solvolysis method using a glycol-based solvent to aggregate the lignin. including. The precipitated lignin can be separated and recovered by filtration or centrifugation. According to this method, lignin can be efficiently recovered at a high yield, and the obtained lignin can be used as a material.

  In the normal pressure acid solvolysis method, the lignin can be recovered by precipitating the lignin by bringing the filtrate recovered from the cooking step into an acidic state, but the lignin is also added to the supernatant after the lignin precipitation. It is included. The method for recovering lignin of the present invention includes adding an aggregating agent containing a cationized lignin to the supernatant after lignin separation to aggregate the lignin.

  The method for recovering lignin of the present invention also includes adding a flocculant containing cationized lignin to the cooking liquor containing lignin recovered in the pulping technique other than atmospheric acid solvolysis and the cooking method in biorefinery technology. Aggregating lignin. For example, the lignosulfonic acid can be aggregated by adding a lignin flocculant to an aqueous solution containing lignosulfonic acid, which is a waste liquid after sulfite cooking.

  The amount of the flocculant containing cationized lignin added to the solution containing lignin may vary depending on the pH and temperature of the solution, but is 0.05 wt% to 5 wt% with respect to the weight of lignin in the solution. Preferably, 0.1% by weight to 2% by weight is more preferable, and 0.5% by weight to 1% by weight is further preferable. The pH of the solution containing lignin may be any, but is preferably pH 3-8, more preferably pH 5-7.

  The lignin precipitated by the recovery method of the present invention is separated by filtration or centrifugation, and can be used as a lignin material after washing. The precipitated and recovered lignin may contain a flocculant containing cationized lignin, but since the flocculant is derived from lignin, lignin material compared to inorganic flocculants such as aluminum sulfate and other organic flocculants There is an advantage in using the flocculant containing the cationized lignin of the present invention in that it does not affect the performance of the present invention.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further, this invention is not limited to these.

Example 1 Production 1 of Cationized Lignin and Lignin Aggregation Test 1
<Search for functional groups that exhibit cohesiveness>
1) Samples The following samples were used as lignin.
Solvated lignin derivative (glycol lignin by PEG digestion of cedar made by Forestry Research Institute (hereinafter referred to as “glycol lignin”)
・ Enzyme lignin (from Japanese cedar)
・ Soda lignin (purified from Sugi soda cooking black liquor by Forest Research Institute)
・ Lignosulfonic acid (Pearl Rex (Nippon Paper Chemicals))
The following samples were used as cationizing agents.
・ Glycidyltrimethylammonium chloride (GTA)

2) Introduction of cationic groups into lignin Take 0.2 g of various lignins in a flask, add 50 mL of 0.5 N NaOH aqueous solution, leave it in an oil bath at 60 ° C for 3 days, and then add 60 mg of glycidyltrimethylammonium chloride (GTA). mL was added and reacted in an oil bath at 50 ° C. for 3 hours (FIG. 1, Table 1: Trial 1 to 3). The insoluble matter in the reaction solution was removed using a membrane filter having a pore size of 0.45 μm, and cationized lignin was obtained by dialysis and recovery using a 3500 MWCO dialysis membrane. A portion of the collected solution was lyophilized and the weight was measured to determine the concentration of cationized lignin in the solution. A cationic group was also introduced into soda lignin by the same procedure. Enzyme lignin was not completely dissolved even when 50 mL of 0.5 N NaOH aqueous solution was added. The enzyme lignin was treated in an oil bath at 60 ° C. for 3 days, and 60 mL of GTA was added and reacted in an oil bath at 50 ° C. for 3 hours. Since insoluble matter remained even after the reaction, the insoluble matter was removed using a membrane filter having a pore size of 0.45 μm and dialyzed in the same manner as glycol lignin and soda lignin.

3) Examination of lignin agglomeration experiment and lignin agglomeration experiment Weigh lignin suspension into a test tube so that the solid content concentration is 1 g, and add 1% cationized lignin (CL) to the weight of lignin. % Was added. As the lignin, glycol lignin (glycol lignin by PEG cooking of cedar made by Forestry Research Institute) was used. Immediately after the addition, the test tube was turned over once, mixed with the solution, and allowed to stand to observe the state of the solution. In the same manner, experiments were also conducted for addition of 0.5 wt%, 0.25 wt%, and 0.1 wt% of cationized lignin. In addition, as a comparative experiment, a coagulation experiment using GTA (the same amount of cation as CL added at 1 wt%) and lignosulfonic acid (Pearlx Nippon Paper Chemicals Co., Ltd., added at 1 wt%) as a coagulant was also performed.
The height of the boundary line between the aggregate and the supernatant produced by coagulation sedimentation was measured, and the percentage of the boundary surface relative to the initial water level (defined as sedimentation) was calculated and used as an index for flocculation.
Sedimentation degree (%) = (height of boundary line between aggregate and supernatant) / (initial water level) × 100

(result)
First, in order to confirm what kind of functional group is effective, when anionic lignosulfonic acid was used as a flocculant, no aggregating property was shown. When trial was carried out using cationic trimethylglycidyl ammonium chloride as a flocculant, this also showed no flocculence. Next, when the cationized lignin (CL) prepared this time was added, a sufficient aggregation effect was observed with addition of 0.5 wt% for any sample, and the sedimentation degree reached about 30% 30 minutes after the addition ( Table 2).

Example 2: Production of cationized lignin 2 and lignin aggregation test 2
<Optimization of functional group introduction method>
In addition to studying the reaction conditions to reduce the amount of GTA as a cationizing agent as much as possible, we aimed to simplify the process procedure.

(Experimental procedure)
1) Reaction conditions As shown in Table 3, a predetermined amount of glycol lignin was dissolved in 10 mL of 0.5 N NaOH aqueous solution. A predetermined amount of glycidyltrimethylammonium chloride (GTA) was added thereto and reacted for 3 hours with stirring in an oil bath or water bath at 50 ° C. The solution after the reaction was dialyzed in running water using a 3500 MWCO dialysis membrane (BioDesign Inc. of New York) to remove NaOH. Entry 8 did not undergo dialysis, and the solution after completion of the reaction was neutralized with H ₂ SO ₄ to pH 7 and used as a sample as it was.

2) Aggregation experiment Each sample solution was measured so that the test tube contained 1 wt% of cationized lignin (CL) with respect to the amount of solid matter of lignin, and water was added to make up to 7 mL. In another test tube, the lignin suspension was measured so that the solid content was 1 g (pH 6.4). As the lignin, glycol lignin (glycol lignin by PEG cooking of cedar made by Forestry Research Institute) was used. The solution containing cationized lignin (CL) was warmed to 50 ° C. in a water bath and added to the lignin suspension with a pipette that had been preheated to 50 ° C. in an oven. Immediately after the addition, the test tube was turned over once, and after mixing the solution, the solution was allowed to stand at room temperature and the state of the solution was observed. In addition, the height of the boundary line generated by coagulation sedimentation was measured. What added only water was made into the blank. In addition, experiments for adding 0.5 wt% and 0.1 wt% of cationized lignin were conducted in the same manner.
In order to investigate the effect of the pH and temperature of the solution, the Entry 8 sample was subjected to an experiment in which the pH of the aqueous solution was 5 and 3 (adjusted with H ₂ SO ₄ ) and an experiment in which the temperature of the aqueous solution was 30 ° C.
As a comparative example, the lignin aggregation experiment of aluminum sulfate and a polymeric cationic flocculant (dimethylaminoethyl acrylate DAA manufactured by Kurita Kogyo Co., Ltd.) was carried out under the conditions of pH 6.4, pH 5.0, and pH 3.0 as in the above method. Below, it carried out with the addition amount of 0.1 wt%, 0.5 wt%, and 1 wt%.

(result)
Table 4 shows the results of the aggregation experiment. Since Trial 9 and 10 had many water-insoluble portions and the introduction amount of the cationic group was judged to be small, the following examination was not performed. Trial 4, which used about 3 times the amount of cationizing agent relative to lignin, showed an aggregating effect when 0.5% was added. Further, when the amount of the cationizing agent was reduced, the cationized lignin (CL) showed a sufficient aggregation effect with addition of 1 wt% even when the amount was about 1/3 of the lignin (Trial 7). Further, it was found that there was an aggregating effect without performing dialysis after the reaction between lignin and the cationizing agent (Trial 8), and the production process could be simplified.
As a result of investigating the influence of pH, in the case of pH 5, a coagulation effect was observed even when the amount of cationized lignin added was 0.5 wt%. At pH 3, an aggregation effect was observed when cationized lignin was added at 0.1 wt%, and when the addition amount was 0.5 wt% or more, no aggregation effect was exhibited. It is considered that the charge state of lignin in the solution was changed by the pH and brought such a result.
When the influence of temperature was examined, the coagulation sedimentation rate was lower at 30 ° C than at 50 ° C.

  Aluminum sulfate showed a lignin aggregation ability almost equal to that of cationized lignin. The commercially available polymeric cationic flocculant did not show the agglutination effect at any pH condition when added at 0.1%. Moreover, although the aggregation effect was recognized in 0.5% and 1.0%, the aggregated particles were fine and the boundary surface was not clear. Recovery of lignin by centrifugation and filtration seems difficult.

Example 3: Lignin aggregation test 3
<Application of cationized lignin (CL) to fine processing in lignin recovery process>
At present, the centrifugation method is applied in the recovery process of lignin in the atmospheric acid solvolysis method, but semen also contains lignin. An attempt was made to apply cationized lignin (CL) to recovering lignin dissolved in the supernatant.

(Experimental procedure)
The pH in the recovery process (lignin content 4.2 g / L) was adjusted to 3, 5, and 7 with an aqueous NaOH solution. Cationized lignin (CL) (Table 3 Trial 4-8) was added in an amount of 1, 3, 5 wt% with respect to the weight of lignin in the supernatant of the recovery process, and aggregation precipitation was observed. Those that aggregated and settled within 30 minutes were marked with ◎, and those that aggregated and settled within 1 hour were marked with ○.

(result)
The results are shown in Table 5. At pH 5 and pH 7, aggregated sedimentation was observed for all cationized lignins (CL). On the other hand, no coagulation sedimentation was observed at pH 3.

  The present invention provides a method for producing an aggregating agent for efficiently aggregating lignin from lignin. According to the lignin flocculant and lignin recovery method of the present invention, engineering plastics, various thermoplastic resins, films, electronic substrates, fiber reinforcements, various adhesives, carbon fibers, activated carbon fibers, various carbon materials, and chemical admixtures for concrete Lignin that can be used as a raw material for high value-added materials such as agents, dispersants, and various surfactants can be recovered in high yield.

Claims (6)

  A lignin flocculant comprising a cationized lignin that essentially comprises a lignin site and a cationizing agent site.   The lignin is obtained by enzymatic saccharification of lignocellulose, a lignin derivative obtained by solvolysis of lignocellulose with at least one cooking solvent selected from polyethylene glycol, diethylene glycol, ethylene glycol, glycerin and polyglycerin. The lignin flocculant according to claim 1, which is an alkaline lignin obtained by alkaline digestion of enzyme lignin or lignolose.   The lignin flocculant according to claim 1 or 2, wherein the cationizing agent is glycidyltrimethylammonium chloride.   A method for producing a lignin flocculant containing a cationized lignin, comprising reacting a lignin and a cationizing agent to obtain a cationized lignin.   A method for recovering lignin, comprising aggregating lignin by adding the lignin flocculant according to claim 1 to a solution containing lignin.   The method for recovering lignin according to claim 5, wherein the pH of the solution containing lignin is 3-8.