KR20230083010A - Carbon molding product derived from lignin and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a lignin-derived carbon molded product and a manufacturing method thereof. The lignin-derived carbon molded product according to one embodiment of the present invention, as a porous 3D molded product formed by dry-mixing lignin carbide and lignin powder, has excellent electrical conductivity and chemical stability and has a large surface area, to be used in a variety of fields, including an energy storage system, a solar cell, a fuel cell, an absorbent for a toxic organic solvent, an adsorbent, and a sound absorber.

Description

Carbon molding product derived from lignin and manufacturing method thereof {Carbon molding product derived from lignin and manufacturing method thereof}

The present invention relates to a lignin-derived carbon molded article and a method for manufacturing the same, and more particularly, to a lignin carbon molded article produced by a dry process without a solvent and a method for manufacturing the same.

Carbon materials generally have advantages over other materials, such as thermal stability, chemical resistance, and corrosion resistance. Carbon foam, one of various carbon materials, is a material having a three-dimensional network structure having various shapes and sizes. Compared to other carbon materials, carbon foam may have properties such as high thermal and electrical conductivity, light weight, high chemical resistance, high temperature stability, low thermal expansion coefficient and high surface area. Carbon foam is used in various fields such as heat dissipation materials, and is known to have high potential to expand its use fields such as electric and electronic devices, optical devices and filters due to its characteristics of being lighter than metal materials and having high thermal conductivity and chemical resistance.

However, the carbon foam has a disadvantage in that the pores present in the structure are non-uniform and the strength is relatively weak because it is composed of an open cell structure. As a way to overcome the disadvantages of such low strength, research on increasing mechanical strength by adding reinforcing materials to carbon foam has been conducted.

In addition, the general molding process of carbon foam is obtained from fossil fuels such as phenolic resin, coal, pitch, etc., the manufacturing process is complex and expensive in several steps, and the disadvantages of causing toxic gases and odors during manufacturing Have. Accordingly, research is being conducted on producing carbon foam by a simple manufacturing method using non-toxic, biodegradable and biocompatible natural cellulose-derived materials rather than carbon foam obtained from fossil fuels.

Korean Patent Publication No. 2019-0049013 relates to a method for manufacturing natural material carbon foam using a cellulose derivative, and discloses a method for manufacturing carbon foam using waste artificial marble powder.

Korean Patent Publication No. 2021-0043753 discloses a carbon foam having a linear portion and a coupling portion coupling the linear portion, a membrane electrode composite, and a carbon content of 51% by mass or more, and a coupling portion coupling the linear portion and the linear portion. , a carbon foam and membrane electrode composite having an average deviation of friction coefficient of 0.006 or less according to the Kawabata evaluation system method.

Korean Patent Publication No. 2019-0049013 Korean Patent Publication No. 2021-0043753

An object of the present invention is to provide a lignin-derived carbon molded article produced by a dry process without a solvent and a manufacturing method thereof.

One embodiment of the present invention provides a lignin carbon molded article formed by dry mixing lignin carbide and lignin powder.

The thickness of the lignin carbon molded article may be 0.5 mm to 10 mm.

The specific surface area of the lignin carbon matrix may be 100 m ² /g to 1,000 m ² /g.

The lignin carbide may be obtained by carbonizing at least one lignin selected from the group consisting of kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and weak acid treated lignin.

The lignin carbide may be kraft lignin carbide represented by Formula 1 below, and the lignin powder may be kraft lignin represented by Formula 1 below.

[Formula 1]

The lignin carbon molded body includes Chemical Formula 2 below and may have a partially crystalline structure.

[Formula 2]

The lignin carbon matrix may include a thiol group (-SH) in a crystalline structure.

Another embodiment of the present invention is to prepare lignin; A pretreatment step of adding an acid to the lignin and stirring it; heat-treating the pretreated lignin in an inert atmosphere to obtain lignin carbide; dry mixing the lignin carbide and lignin powder; and preparing a molded article by heating and pressurizing the mixture.

The heating may be performed at 200 to 300 °C.

The pressurization may be performed at 300 to 400 kgf/cm ² for 10 to 60 minutes.

The weight ratio of the lignin carbide and the lignin powder may be 8:2 to 5:5.

The lignin may be at least one selected from the group consisting of kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and weak acid treated lignin.

The lignin carbide is obtained from kraft lignin, and kraft lignin may be used as the lignin powder.

Obtaining the lignin carbide may include an oxidative stabilization step of heating at 200 to 400 °C and a carbonization step of heating at 500 to 1000 °C.

Obtaining the lignin carbide may include adding water vapor.

In the pretreatment, the mixing ratio of the acid solution and the lignin may be 10:0.5 to 10 (weight ratio).

Another embodiment of the present invention provides a lignin carbon matrix produced according to one embodiment of the present invention.

A lignin-derived carbon molded body according to an embodiment of the present invention is a porous 3D molded body formed by dry mixing lignin carbide and lignin powder, and is formed by mixing lignin carbide and lignin powder serving as a binder, and is formed of 100% natural material. .

The lignin carbon molded article according to an embodiment of the present invention is a three-dimensional porous molded article that has excellent electrical conductivity, chemical stability, and high surface area, so it can be used in energy storage systems, solar cells, fuel cells, absorbents for toxic organic solvents, adsorbents, sound absorbers, and the like. It can be used in various fields.

1 is a photograph of a lignin-derived carbon molded article according to an embodiment of the present invention.
2 is a graph showing heating conditions in an oxidation stabilization step and a carbonization step according to an embodiment of the present invention.
3 is a photograph of a lignin-derived carbon molded article according to Comparative Example 1;
4 is a photograph of a lignin-derived carbon molded article according to Comparative Example 2;

Hereinafter, embodiments and examples of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments and examples set forth herein.

Terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "comprise" or "have" are intended to designate that there is a feature, step, operation, component, part, or combination thereof described in the specification, but one or more other features or steps However, it should be understood that it does not preclude the possibility of existence or addition of operations, components, parts, or combinations thereof.

In addition, unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in this application, it should not be interpreted in an ideal or excessively formal meaning. don't

The present invention relates to a lignin-derived carbon molded article and a method for manufacturing the same. The lignin-derived carbon molded article according to an embodiment of the present invention is a porous 3D molded article formed by dry mixing lignin carbide and lignin powder. A carbon molded body according to an embodiment of the present invention may be a carbon foam having a plurality of pores formed therein.

A lignin-derived carbon molded body (hereinafter, also referred to as a 'lignin carbon molded body' or 'carbon molded body') according to an embodiment of the present invention is formed by mixing lignin carbide and lignin powder serving as a binder, and is formed of 100% natural material. It can be.

The carbon molded body according to an embodiment of the present invention may have a thickness of 0.5 to 10 mm. In addition, the specific surface area may be 100 to 1,000 m ² g ^-1 .

According to one embodiment of the present invention, the carbon molded body includes Chemical Formula 2 below and may have a partially crystalline structure.

[Formula 2]

According to one embodiment of the present invention, the carbon shaped body may include a -SH (thiol group) in a crystalline structure.

The carbon molded article according to an embodiment of the present invention is a three-dimensional porous molded article that has excellent electrical conductivity, chemical stability, and high surface area, so that it can be used in various applications including energy storage systems, solar cells, fuel cells, toxic organic solvent absorbers, adsorbents, and sound absorbers. can be used in the field.

Hereinafter, a method for manufacturing a lignin-derived carbon molded article according to an embodiment of the present invention will be described in detail. Accordingly, the structure and characteristics of the lignin-derived carbon molded article according to an embodiment of the present invention can be more clearly specified.

First, lignin may be prepared.

According to one embodiment of the present invention, the lignin may be obtained from wood extract. Lignin is a fat-soluble phenolic polymer among various constituents constituting woody parts of conifers and broad-leaved trees, and is one of the main components of biomass along with cellulose and hemi-cellulose.

The process of manufacturing pulp, which is the raw material for making paper, is called pulping. The pulping process is a process of removing the remaining components except for cellulose from a mixture composed of cellulose, hemicellulose, lignin, and other extracts, which are constituents of wood. . In the pulping process, the waste liquid including the remaining substances removed except for cellulose is generally referred to as black liquor.

According to one embodiment of the present invention, the lignin may be separated and extracted from black liquor. Although not limited thereto, for example, the lignin is Kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, or weak acid treated lignin. lignin), and one or more of them may be mixed and used. Specifically, the lignin may be kraft lignin.

The kraft lignin may be represented by Formula 1 below. Although not limited thereto, for example, it may be obtained by adding sodium sulfide, sodium hydroxide, etc. to black liquor and subjecting it to heat treatment at 150 to 180°C.

[Formula 1]

The sulfite lignin may be a lignosulfonate obtained by adding sulfurous acid and the like and heat-treating at 150 to 180 ° C.

The organic solvent lignin (organosolv lignin) can be obtained by adding an organic solvent to black liquor and heat treatment at 150 to 180 ° C.

The steam explosion lignin (steam explosion lignin) can be obtained from pulp fibers obtained by steam treatment at high pressure and high temperature.

The weak acid treated lignin (dilute acid lignin) can be obtained after separating cellulose with a weak acid.

Next, the lignin may be pretreated.

The pretreatment step may be performed by adding an acid solution to lignin and stirring. Impurities such as inorganic substances in lignin can be removed by the pretreatment process. Gases generated in the carbonization process can be controlled by removing impurities from lignin.

According to one embodiment of the present invention, the acid solution may be hydrochloric acid, sulfuric acid, nitric acid, bromic acid, etc., and the mixing ratio of the acid solution and lignin may be 10: 0.5 to 10 (weight ratio), specifically 10 : may be 0.5 to 3. After mixing the lignin and acid solution, it may be stirred for 1 to 10 hours.

The pretreated lignin may be heat-treated in an inert atmosphere to obtain lignin carbide.

According to one embodiment of the present invention, the carbonization step may be performed at 500 to 1000 °C. Specifically, it may be performed at 800 to 1000 ° C, more specifically at 850 to 950 ° C. The inactivation atmosphere may be performed in a nitrogen or argon atmosphere.

In addition, according to one embodiment of the present invention, an oxidation stabilization step may be performed before the carbonization step. The oxidation stabilization step may be performed by heat treatment at 200 to 400° C. in an air atmosphere. The oxidative stabilization step may be performed for 1 to 3 hours. If the oxidative stabilization process is performed before carbonization of lignin, the carbonization yield can be increased by increasing cross-linking between molecules through oxygen reaction.

Oxidative stabilization can be heated at a temperature higher than the softening point of the material. If the temperature is lower than the above range in the oxidative stabilization step, oxidation stabilization is insufficient and the carbonization properties deteriorate, and if it is higher than the above range, a decomposition reaction due to oxygen occurs, Carbon defects may be generated, and if the heating time is out of the above range, the heating time may be insufficient and oxidation stabilization may be insufficient.

According to one embodiment of the present invention, the oxidation stabilization step and the carbonization step may be performed in one process. The carbonization step may be performed by changing the air atmosphere of the oxidation stabilization step to an inert atmosphere and raising the temperature. At this time, the temperature increase for the carbonization step in the oxidation stabilization step may be performed at 5 to 15 °C/min, specifically 10 °C/min. When the temperature increase rate is in the above range, a sufficient cross-linking time may be given. If the heating rate is faster than the cross-linking may not sufficiently occur, and if the heating rate is slower than the heating rate, the time cost increases rapidly.

In addition, according to one embodiment of the present invention, steam may be added in the step of carbonizing the lignin. When water vapor is injected during the carbonization process, more thermal decomposition occurs around the pores of the carbonized lignin, thereby producing porous activated carbon having a high specific surface area.

By performing the carbonization treatment and the activation treatment, a porous and partially crystalline structure can be induced in the activated carbon.

A graphitizable part and a non-graphitizable part mixed in the lignin carbide may be increased in crystalline part by the oxidation stabilization process and the addition of water vapor. As the crystalline portion increases, properties such as electrical conductivity of the lignin carbon matrix may be improved.

Next, the lignin carbide and lignin powder may be dry mixed.

According to one embodiment of the present invention, the lignin powder may be at least one lignin powder selected from the group consisting of kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and weak acid treated lignin.

The lignin powder may be obtained by removing impurities by pre-treating lignin extracted from black liquor. The pretreatment process is as described above.

According to one embodiment of the present invention, the weight ratio of the lignin carbide and lignin powder may be 8:2 to 5:5. If the lignin powder is less than the above range, moldability may be deteriorated, and if the lignin powder exceeds the above range, impurities may increase and performance of the molded article, such as electrical conductivity, storability, and adsorption may be deteriorated.

The lignin carbide obtained in the carbonization process may be pulverized and mixed in a powder state. According to one embodiment of the present invention, lignin carbide and lignin powder may be mixed without a solvent. The dry mixing method is not particularly limited, and a conventional mixing process such as a mixer, ball mill, 3D mixer, V cone mixer, ribbon mixer, and bead mill may be used.

According to one embodiment of the present invention, the mixing process may be performed for 1 to 10 minutes.

Compared to the commonly used wet process, dry mixing can be performed as a simple process. In the case of the wet process, molding is easy using a solvent, but a separate drying process must be performed.

Next, a molded article may be prepared by heating and pressurizing the mixture. Specifically, a molded article may be prepared by filling the mixture in a mold and hot-pressing it. According to one embodiment of the present invention, the pressurization is applied at 300 to 400 kgf/cm ² , and the heating may be performed at a temperature of 200 to 300°C. The heating and pressing process may be performed for 10 to 60 minutes, and may be specifically performed for 30 to 60 minutes. The lignin powder can be liquefied by hot compression, which can act as a binder and cross-link the lignin carbide.

If the pressure condition is out of the above range, moldability may not be good, and if the temperature condition is out of the above range, cracks may occur and it may be difficult to manufacture a molded body.

If only the pressure is increased at room temperature, molding is not performed, and if the temperature is only increased at low pressure, even if molding is performed, the strength is weak and can be easily broken.

The carbon shaped body may include Chemical Formula 2 below and may have a partially crystalline structure.

[Formula 2]

According to one embodiment of the present invention, the carbon shaped body may include a -SH (thiol group) in a crystalline structure.

In Formula 2, R may be -CH ₃ .

Hereinafter, the present invention will be described in more detail through examples according to an embodiment of the present invention, but these examples do not limit the scope of the present invention.

[Example]

Example

pretreatment process

A hydrochloric acid 1 normal solution was prepared, 1 L of hydrochloric acid was added to 36 g of Kraft Lignin (KL) (1:1 w/w), stirred, and washed with distilled water to a pH of 7.

Kraft Lignin Carbonization

The washed lignin was heat-treated (oxidized and stabilized) at 300° C. for 2 hours in an air atmosphere in a tube electric furnace, and then heated up to 900° C. at a heating rate of 10° C./min while switching to an inert atmosphere (nitrogen) to obtain carbides.

2 is a graph showing heating conditions in a stabilization step and a carbonization step according to an embodiment of the present invention. As shown in FIG. 2, the temperature was gradually raised to 300° C., maintained for 2 hours, and then raised to 900° C.

mixing and molding

8g of lignin carbide and 2g of lignin binder were mixed in a mixer for 10 minutes, 1g of this was filled in a spherical mold (20Φ), and heated (300° C.) and pressurized (400kgf/cm ² ) for 10 minutes to obtain a molded product. 1 is a photograph of a molded body thus obtained.

Comparative Example 1

It was prepared in the same manner as in the above example, but pressurized (400 kgf/cm ² ) at room temperature (25° C.) for 10 minutes. In the process of separating the sample from the mold, instability was observed in which the molded body did not maintain structural stability. Figure 3 is a photograph taken of the molded body thus obtained.

Comparative Example 2

It was prepared in the same manner as in the above example, but heated (100° C.) and pressurized (400 kgf/cm ² ) for 10 minutes. When taken out of the mold, some cracks occurred, and the shape was maintained to some extent, but it was easily broken when held by hand, and the strength was weak. Figure 4 is a photograph taken of the molded body thus obtained.

As described above, the molded body manufactured according to one embodiment of the present invention maintained the molded body without cracks, but it was confirmed that cracks occurred when the molded body was not heated to a certain temperature during hot compression.

The above description is merely an example of the technical idea of the present embodiment, and various modifications and variations can be made to those skilled in the art without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment, but to explain, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of this embodiment should be construed according to the claims below, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of rights of this embodiment.

Claims (17)

Lignin carbon matrix formed by dry mixing of lignin carbide and lignin powder.
According to claim 1,
The lignin carbon molded body has a thickness of 0.5 to 10 mm.
According to claim 1,
The specific surface area of the lignin carbon molded body is 100 to 1,000 m ² g ^-1 lignin molded body.
According to claim 1,
The lignin carbide is obtained by carbonizing at least one lignin selected from the group consisting of kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and weak acid treated lignin.
According to claim 1,
The lignin carbide is kraft lignin carbide represented by Formula 1 below, and the lignin powder is kraft lignin represented by Formula 1 below.
[Formula 1]

According to claim 1,
The lignin carbon molded material includes Formula 2 below and has a partially crystalline structure.
[Formula 2]

According to claim 1,
The lignin carbon molded material includes a -SH (thiol group) in a crystalline structure.
preparing lignin;
A pretreatment step of adding an acid to the lignin and stirring it;
heat-treating the pretreated lignin in an inert atmosphere to obtain lignin carbide;
dry mixing the lignin carbide and lignin powder; and
heating and pressurizing the mixture to prepare a molded body;
Method for producing a lignin carbon molded body comprising a.
According to claim 8,
The heating is a method for producing a lignin carbon molded article performed at 200 to 300 ° C.
According to claim 8,
The pressing is performed at 300 to 400 kgf/cm ² for 10 to 60 minutes.
According to claim 8,
A method for producing a lignin carbon molded article wherein the weight ratio of the lignin carbide and the lignin powder is 8:2 to 5:5.
According to claim 8,
The method of claim 1, wherein the lignin is at least one selected from the group consisting of kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and weak acid treated lignin.
According to claim 8,
The lignin carbide is obtained from kraft lignin, and the lignin powder is a method for producing a lignin carbon molded body using kraft lignin.
According to claim 8,
The step of obtaining the lignin carbide comprises an oxidative stabilization step of heating at 200 to 400 ° C and a carbonization step of heating at 500 to 1000 ° C.
According to claim 8,
The method of manufacturing a lignin carbon molded body comprising the step of adding water vapor in the obtaining of the lignin carbide.
According to claim 8,
In the pretreatment, the mixing ratio of the acid solution and the lignin is 10:0.5 to 10 (weight ratio).
A lignin carbon molded body produced by the method of any one of claims 8 to 16.

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