KR20210074921A - Method of producing polydisperse lignin microsphere from black liquor of biomass - Google Patents

Abstract

The present invention relates to lignin microparticles prepared from black liquor, which is a biomass by-product, and a method for preparing the same. The lignin microparticles prepared by the preparation method of the present invention can contribute to raising production costs by using black liquor, which is discarded as a process by-product during bioethanol production using biomass, as an industrial material. By developing particles of lignin microstructure derived from alkali black liquor, it is expected to contribute to the development of industrial materials such as adsorbents and UV-protective agents in the agricultural sector.

Description

Method of producing lignin microspheres from black liquor of biomass

The present invention relates to lignin microparticles prepared from black liquor, a biomass by-product, and a method for preparing the same.

The production of first-generation bioethanol, such as sugar cane and corn, was similar to the existing industries such as the food industry, leading to growth until the mid-2000s, but it was in a crisis due to competition with food and feed in terms of raw material supply. Since then, the development of second-generation bioethanol production technology based on lignocellulosic and herbaceous fibrous raw materials has attracted worldwide attention.

In order to commercialize bioethanol, it is necessary to build a pilot plant scale model and acquire production process technology such as biomass pretreatment technology. It is necessary to develop technologies for the treatment and reuse of the generated waste liquid. Accordingly, in order to improve the utilization of process by-products using biomass, research on lignin extraction methods contained in black liquor is being conducted. For example, Korean Patent Registration No. 10-1521238 discloses a method of extracting high-purity lignin from lignocellulosic black liquor.

However, there is no research on developing lignin microstructured particles from biomass-derived black liquor and using them as industrial materials.

The present invention has been submitted to solve the above problems, and the present inventors have studied diligently to utilize lignin as an industrial material to improve the utilization of black liquor, a process by-product during bioethanol production using biomass. The present invention was completed by confirming the characteristics of microstructured particles in the lignin contained in the extracted black liquor.

Accordingly, the present invention comprises the steps of: (a) centrifuging the black liquor recovered in the biomass manufacturing process; (b) lowering the pH by treating the upper (blue) solution obtained by the centrifugation with an acidic solution of 25% to 98%; and (c) inducing a hydrolysis reaction at 115° C. to 125° C. for a reaction time of 1 to 5 hours.

Another object of the present invention is to provide lignin microparticles prepared by the above production method.

In order to achieve the above object, the present invention comprises the steps of (a) centrifuging the black liquor recovered in the biomass manufacturing process; (b) lowering the pH by treating the upper (blue) solution obtained by the centrifugation with an acidic solution of 25% to 98%; and (c) inducing a hydrolysis reaction at 115°C to 125°C.

In one embodiment of the present invention, the method may further include (d) centrifuging the hydrolyzed solution.

In another embodiment of the present invention, the pH may be lowered to 3 to 4 in step (b).

In another embodiment of the present invention, the acidic solution in step (b) may be _{sulfuric acid (H 2} SO _{4 ).}

In another embodiment of the present invention, the hydrolysis reaction in step (c) may be performed for 1 hour to 5 hours.

In addition, the present invention provides lignin microparticles prepared by the above production method.

In one embodiment of the present invention, the lignin microparticles may have a size of 0.8 to 1.0 μm.

The lignin microparticles produced by the manufacturing method of the present invention can contribute to the improvement of production cost by using black liquor, which is discarded as a process by-product during bioethanol production using biomass, as an industrial material, and particles of lignin microstructure derived from alkali black liquor are developed. This is expected to contribute to the development of industrial materials such as adsorbents and UV-protective agents in the agricultural sector.

1 shows a schematic diagram of the lignin recovery process in the continuous pretreatment process.
Figure 2 shows a schematic diagram for the establishment of the lignin mass balance of the pre-treated black liquor.
3 shows a schematic diagram of a process for extracting and purifying lignin from black liquor.
4 shows the comparison results of physicochemical components according to reaction time and acidity in the treatment conditions for extracting lignin from black liquor.
5 shows the process of extracting lignin as microstructured particles from black liquor.
6 shows the results of analyzing the microstructure of lignin microspheres according to reaction time and acidity using a scanning electron microscope.
7 shows the results of analyzing the microstructure of the lignin microspheres according to the reaction time and the concentration of the treated sulfuric acid using a scanning electron microscope.
8 shows the particle size distribution of the microstructure of the lignin microspheres according to the reaction conditions by controlling the concentration and reaction time of sulfuric acid.
9 shows the FT-IR analysis results for each reaction condition by controlling the concentration and reaction time of sulfuric acid.
10 shows the results of TGA (Thermogravimatric analysis) analysis by controlling the concentration and reaction time of sulfuric acid and by reaction conditions.
11 shows the XRD analysis results for each reaction condition by controlling the concentration, pH, and reaction time of sulfuric acid.
12 shows the GC MSD analysis results for each reaction condition by controlling the concentration and temperature of sulfuric acid.
13 shows the results of confirming the structure of each lignin monomer through GC/MS scan data.

Hereinafter, the present invention will be described in detail.

The present inventors studied intensively to utilize lignin as an industrial material to improve the utilization of black liquor, a process by-product in bioethanol production using biomass, and as a result, confirmed the microstructure particle characteristics of lignin contained in black liquor extracted under specific conditions. The invention was completed.

Accordingly, the present invention comprises the steps of: (a) centrifuging the black liquor recovered in the biomass manufacturing process; (b) lowering the pH by treating the upper (blue) solution obtained by the centrifugation with an acidic solution of 25% to 98%; and (c) inducing a hydrolysis reaction at 115°C to 125°C.

In addition, the present invention may further include (d) centrifuging the hydrolyzed solution.

The term "biomass" used in the present invention refers to an energy source of bioenergy usable as chemical energy, which may be selected from biomass by living organisms such as plants, animals, and microorganisms, but is preferably herbal biomass, more preferably Giant pampas grass can be used. Herbal biomass is a type of cellulosic biomass, and refers to biomass including cellulose of polysaccharides, which are the main components of plant cell walls. All plants with cell walls are included, and both agricultural and forestry residues and industrial residues can be included.

In one embodiment of the present invention, the pH in step (b) is preferably lowered to 1 to 4, more preferably the pH can be lowered to 3 to 4, and it is most preferred to lower the pH to 4. The amount of lignin-containing solids extracted is increased at low pH conditions, and the largest amount of lignin-containing solids can be extracted at pH 4.

In another embodiment of the present invention, the acidic solution of step (b) is not limited by any of the commonly used acidic solutions, but is preferably sulfuric acid, more preferably 25 to 98% of sulfuric acid. and 25% sulfuric acid is most preferred.

In another embodiment of the present invention, inducing the hydrolysis reaction in step (c) is preferably hydrolyzed at a high temperature, more preferably (a) hydrolysis at 115°C to 125°C. , it is most preferable to induce the hydrolysis reaction at 121 °C. In inducing the hydrolysis reaction, the reaction time is preferably performed for 1 hour to 3 hours, and more preferably for 1 hour. At this time, the result of reacting the hydrolysis for 1 hour may be fine particles with a smaller particle size compared to other conditions.

In addition, the present invention provides lignin microparticles prepared by the above production method.

As used herein, the term “fine particles” refers to fine particulate matter having a particle diameter of 10 μm or less. In the present invention, the lignin microparticles may include a lignin structure having a particle size of 10 μm or less, but preferably have a size of 0.8 to 1.0 μm, and when the particle size is small 1.0 μm, it is useful for developing adsorbents and industrial materials. It can be used more usefully.

In the present invention, a lignin extract of microstructured particles was prepared through the preparation method as described above.

Accordingly, in one embodiment of the present invention, treatment conditions were variously adjusted to extract lignin microstructured particles from black liquor recovered during the biomass manufacturing process, and sulfuric acid at 25%, 50% and 98% concentrations (H ₂ SO ₄ ) treatment to control the pH, the amount of lignin-containing solids extracted was confirmed (see Example 2-3), the concentration and reaction time of sulfuric acid were adjusted, and the particle size distribution of the microstructure according to the reaction conditions was specifically confirmed to be 25% When sulfuric acid (H ₂ SO ₄ ) was applied and reacted for 1 hour, it was confirmed that 50% less particles compared to other conditions (see Example 3-2).

From the above results, the conditions for manufacturing a lignin microstructure having a small particle size were confirmed, and it is expected that it can be used in various ways in the development of industrial materials such as agricultural adsorbents and UV-protective agents.

Hereinafter, preferred embodiments are presented to help the understanding of the present invention. However, the following examples are only provided for easier understanding of the present invention, and the contents of the present invention are not limited by the following examples.

[Example]

Example 1. Recovery of black liquor produced through pretreatment step and screw press

As shown in FIG. 1 to recover black liquor from herbal biomass, black liquor was recovered through a pretreatment step and a screw press process. More specifically, as shown in FIG. 2, a sample of giant pampas grass, a herbaceous biomass containing 0.97 kg/h of lignin, in a continuous twin-screw type extrusion reactor on a pilot plant scale at a rate of 4.0 to 4.5 kg/h As a result, sodium hydroxide (NaOH) 0.4-0.6M was added at a concentration of 20-27 L/h, and the twin screw type continuous process system was set at 50 rpm to proceed with pretreatment. At this time, the solid-liquid ratio was set to 1:5 to 1:6. The hydrolyzate dissolved through pretreatment was discharged as black liquor at a concentration of 43.5 L/h, and lignin was discharged at a concentration of 14 g/L with a content of 0.61 kg/h. The unhydrolyzed solids were discharged at a content of 6.32 kg/h through the screw press, and it was confirmed that the moisture content was 60%. In addition, it was confirmed that the amount of lignin remaining in the solid was 0.36 kg/h.

Example 2. Recovery and quantification of lignin generated by alkali pretreatment conditions of silver grass

2-1. Extracting and purifying lignin from the recovered black liquor

In order to extract and purify lignin from black liquor, a process as shown in FIG. 3 was performed. Specifically, the black liquor recovered through the screw press after the pretreatment of Example 1 was centrifuged at 12,000 rpm for 30 minutes to remove undissolved substances. The black liquid separated by centrifugation was adjusted to pH 1 to 3 using _{98% sulfuric acid (H 2} SO _{4 ).} Thereafter, it was first hydrolyzed at 121° C. for 1 hour, and cooled at room temperature for 12 hours.

2-2. Treatment conditions for extraction of lignin from black liquor

_{Sulfuric acid (H 2} SO ₄ ) was added to the black liquor cooled in Example 2-1 to lower the pH to 1 to 3, and secondary hydrolysis treatment was performed for 30 to 120 minutes. As a result of analyzing the physicochemical components for each reaction time and acidity treatment condition, it was confirmed that the lignin content was highest in the pH 1 condition as shown in FIG. 4 .

2-3. Treatment conditions for extraction of lignin microstructured particles from black liquor

In order to extract the lignin microstructured particles from the black liquor, extraction was performed in the same manner as shown in FIG. 5 . _{Specifically, sulfuric acid (H 2} SO ₄ ) was added to 400 mL black liquor at a pH of 13.4 to 13.56 to lower the pH to 1 to 4, and reacted at 121° C. for 1 hour and 3 hours using an autoclave, and the amount of lignin-containing solids extracted was analyzed and the results are shown in [Table 1] below.

H ₂ SO ₄
(%) pH of BL Added
Acid
(mL) pH of the mixture Autoclave
Period
(Hour) Extracted Amount
(g) 98 13.47 10.5 One One 7.37 3 7.25 98 13.40 9.45 2 One 6.41 3 6.35 98 13.55 6.5 4 One 8.54 3 8.65 50 13.40 7.5 4 One 7.8 3 8.6 25 13.56 14 4 One 8.08 3 8.05

From the above results, it was confirmed that when _{the pH was adjusted to 4 using 98% sulfuric acid (H 2} SO ₄ ) compared to other conditions, the amount of lignin-containing solids extracted was the highest.

Example 3. Morphological, spectroscopic characteristics and elemental analysis of extracted lignin

3-1. Microstructure Analysis of Lignin Microspheres (LMS) Using Scanning Electron Microscopy

To analyze the microstructure of the lignin microspheres (LMS), the black liquor was _{treated with 98% sulfuric acid (H 2} SO ₄ ) using a scanning electron microscope to adjust the pH to 1, 2, and 4, and then the reaction temperature was 1 at 121 ° C. The microspheres of the extracted lignin were confirmed by reacting for hours or 3 hours. As a result, as shown in FIG. 6 , the size of the fine particles at pH1 was 5 μm or more, and there was no significant difference at pH2 and pH4 according to the pH conditions. Regarding the treatment time, it was confirmed that the particle size was smaller in the case of reacting at 121°C for 1 hour compared to the case of reacting for 3 hours.

In addition, to confirm the microstructure of microspheres (LMS) when treated with different concentrations of sulfuric acid, pH 4 when treated with _{50% sulfuric acid (H 2} SO ₄ ) and 25% sulfuric acid (H ₂ SO _{4 )} At a reaction temperature of 121° C., the microspheres of the extracted lignin were confirmed by reacting for 1 hour or 3 hours. As a result, as shown in Figure 7, 50% sulfuric acid (H ₂ SO ₄ ) treatment under the same pH 4 condition, the result of reaction at 121 ° C. for 1 hour or 3 hours, and 25% sulfuric acid (H ₂ SO ₄ ) treatment and As a result of the reaction at 121° C. for 3 hours, the particle size did not show a significant difference, but it was confirmed that the particle size appeared small when treated with _{25% sulfuric acid (H 2} SO _{4 ) for 1 hour.}

3-2. Confirmation of particle size distribution of lignin microstructure

In order to confirm the particle size distribution of the microstructure for each reaction condition in detail, 50% sulfuric acid (H ₂ SO ₄ ) was treated to adjust the acidity to pH4 and reacted for 1 hour (a) and after reaction for 3 hours (b) ) and 25% sulfuric acid (H ₂ SO ₄ ) to adjust the acidity to pH4 and react for 1 hour (c) and 25% for 3 hours (d). The particle size distribution was compared.

As a result, as shown in FIG. 8, when 50% sulfuric acid (H ₂ SO ₄ ) and 25% sulfuric acid (H ₂ SO ₄ ) were treated, the reaction was carried out at a reaction temperature of 121° C. at pH 4 for 1 hour or 3 hours. As a result of the particle distribution analysis, the average particle size was 1 μm, and it _{was confirmed that the result of applying 25% sulfuric acid (H 2} SO ₄ ) and reacting for 1 hour showed about 50% fewer particles than other conditions.

3-3. Fourier Transform Infrared Spertroscopy (FT-IR) spectroscopic analysis

To check the spectroscopic results for each lignin extraction condition, 50% sulfuric acid (H ₂ SO ₄ ) was treated using FT-IR spectroscopy to adjust the acidity to pH 4 and reacted for 1 hour (a) and 3 hours The result of reaction (b) and 25% sulfuric acid (H ₂ SO ₄ ) were treated to adjust the acidity to pH 4 and reacted for 1 hour (c) and reaction for 3 hours (d) were analyzed.

As a result, as shown in FIG. 9 , a major adsorption band appeared at 1800 cm −1 , and functional groups were determined to be related to lignin.

3-4. Thermogravimatric analysis (TGA) and differential thermogravimetry (DTG) spectroscopic analysis

Samples adjusted to pH 4 by treatment with _{98%, 50% and 25% sulfuric acid (H 2} SO ₄ ) using thermogravimatric analysis (TGA) and differential thermogravimetry (DTG) to check the spectroscopic results for each lignin extraction condition The result of reacting at 121 °C for 3 hours was analyzed by spectroscopy.

As a result of the thermogravimatric analysis (TGA) analysis, as shown in FIG. 10 , it was confirmed that the weight decreased due to water evaporation at 25 to 130° C., and a second rapid weight loss appeared at 200 to 600° C., which was a carbohydrate in lignin. It was analyzed that the components were converted into volatile gases such as CO, CO ₂ and CH _{4 and decomposed.} In addition, it was analyzed that the final decomposition process is shown up to 600~1000°C, and in this step, volatile substances derived from lignin, including phenolic, alcohol, and aldehyde acid, are removed.

As a result of differential thermogravimetry (DTG) analysis, the maximum mass reduction rate of the cellulose component was found at 330°C in the case of the dried biomass, and the mass loss of the microstructured lignin component was confirmed over a wide temperature range of 175-385°C.

3-5. XRD spectroscopy

In order to check the spectroscopic results for each lignin extraction condition, samples adjusted to pH 1 to 4 by treatment with _{98%, 50%, and 25% sulfuric acid (H 2} SO _{4 ) using XRD spectroscopy were prepared at 121 ° C.} Spectroscopic analysis was performed on the result of the reaction time or 3 hours.

As a result, as shown in FIG. 11, the diffraction peak at about 23° was confirmed to be due to the reflection of carbon nanocrystals present in cellulose, and it was confirmed that the light diffraction pattern at 2θ = 22° was due to amorphous lignin.

3-6. GC MSD spectroscopic analysis

In order to check the spectroscopic results for each lignin extraction condition, _{a sample adjusted to pH 4 by treatment with 98%, 50% and 25% sulfuric acid (H 2} SO ₄ ) using GC MSD analysis was treated at room temperature or 121° C. for 3 hours. As a result of spectroscopic analysis of the reaction results, as shown in FIG. 12 , coniferyl-, paracoumaryl-, and sinapyl alcohol, which are lignin building blocks, together with most phenolic compounds and aromatic hydrocarbons, were 5.6min, 8.5min, and 9.5 in each condition sample, respectively. was confirmed with a residence time of min.

From the above results, it was confirmed that more coniferyl (5.6min) and sinapyl alcohol (9.5min) were formed when lignin was extracted and reacted again through acid hydrolysis than from the biomass sample. In addition, paracoumaryl (8.5min) did not show a peak even after reacting in some samples. As a result, it is judged that the organic components including lignin were partially converted into derivatives of other types when treated at 121°C, and it is predicted that the particles played an important role in reconstituting the microstructures in this process.

In addition, as a result of confirming the structure of each lignin monomer through GC/MS scan data, it was confirmed that the structure of each lignin monomer was the same as that of a conventional lignin as shown in FIG. 13 .

3-7. Check the elemental analysis result

Silver grass biomass itself contains 44.8% carbon, 0.13% nitrogen, 5.7% hydrogen, and 41.3% oxygen, and in the case of lignin recovered through acidification, the carbon content was found to be in the range of 50 to 60% on average. Calcium, iron, potassium, sodium, and phosphorus content as trace elements and carbon, nitrogen, hydrogen, oxygen, and sulfur linear fractions were analyzed for each lignin extraction condition, and the results are shown in [Table 2] below.

Samples Carbon
(%) Nitrogen
(%) Hydrogen
(%) Oxygen
(%) Dried Biomass (Miscanthus) 44.78 0.13 5.69 41.33 98%_H ₂ SO ₄

pH1_1Hour 60.60 0.64 5.77 30.68 pH1_3Hour 62.20 0.69 5.85 29.32 pH2_1Hour 56.95 0.87 5.81 33.51 pH2_3Hour 60.80 0.93 5.84 30.28 pH4_1Hour 50.56 1.41 5.63 30.25 pH4_3Hour 50.82 1.50 5.31 30.24 50%_H2SO4
pH4_1Hour 50.31 1.09 5.53 35.16 pH4_3Hour 48.88 0.32 5.11 30.25 25%_H ₂ SO ₄
pH4_1Hour 49.12 0.34 4.99 31.04 pH4_3Hour 49.86 0.56 5.64 32.43 98%_H ₂ SO ₄ _pH4_Ambient 50.82 0.24 5.26 34.45 50%_H ₂ SO ₄ _pH4_Ambient 54.47 0.99 6.07 35.34 25%_H ₂ SO ₄ _pH4_Ambient 53.18 0.88 5.92 36.06

From the above results, a lignin microstructure extract was prepared from black liquor produced by alkaline hydrolysis of herbal biomass, and the prepared lignin microstructure extract had a particle size of 0.8 to 1.0 μm and a carbon content of 50 to 60%. It was confirmed that the efficiency is 15.8-21.6 g/L, and the extract can be used as a pesticide part, heavy metal adsorbent, UV protectant for sunscreen, etc.

The description of the present invention described above is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

Claims (7)

A method for producing lignin microparticles from black liquor, comprising the steps of:
(a) centrifuging the black liquor recovered in the biomass manufacturing process;
(b) lowering the pH by treating the upper (blue) solution obtained by the centrifugation with an acidic solution of 25 to 98%; and
(c) inducing a hydrolysis reaction at 115° C. to 125° C. According to claim 1,
The method further comprises the step of (d) centrifuging the hydrolyzed solution. According to claim 1,
The manufacturing method, characterized in that lowering the pH to 3 to 4 in step (b). According to claim 1,
The acidic solution in step (b) is sulfuric acid (H ₂ SO ₄ ), characterized in that the manufacturing method. According to claim 1,
The hydrolysis reaction in step (c) is characterized in that performed for 1 hour to 5 hours, the manufacturing method. The lignin microparticles prepared by the method of any one of claims 1 to 5. 7. The method of claim 6,
The lignin microparticles are characterized in that having a size of 0.8 to 1.0㎛, lignin microparticles.

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