KR20130046231A - Porous activated carbon from black liquor and method of preparating the same - Google Patents

Abstract

PURPOSE: A manufacturing method of porous activated carbon is provided to commercialize the porous activated carbon by a simplified process, and to obtain the porous activated carbon with the high specific surface area from only the black solution generated in the paper manufacturing process. CONSTITUTION: A manufacturing method of porous activated carbon comprises the following steps: a step of forming precipitates by adding acid into a black solution; a step of extracting lignin by neutralizing the precipitates and drying; a step of obtaining carbonized lignin by heat-treating the dried lignin; and a step of manufacturing the porous activated carbon by injecting steam to the carbonized lignin. The pH of the black solution is controlled 2 after the addition of acid.

Description

Porous Activated Carbon from Black Liquor and Method of Preparating the Same}

The present invention relates to a porous activated carbon using black liquor as a raw material, and more particularly, to extract lignin from black liquor which is a by-product generated from a paper manufacturing process, heat-treating the extracted lignin, and then activating it. It relates to a porous activated carbon and a method for producing the same.

The process of manufacturing pulp, the raw material for making paper, is called pulping.Pulping is the process of removing cellulose from the mixture of cellulose, hemicellulose, lignin, and other extracts of wood. . Pulping methods for removing hemicellulose, lignin, etc. include mechanical pulping, chemical pulping and anti-chemical pulping, and double chemical pulping is a method of pulping by adding chemicals. There is sulfite pulping. Waste liquor containing the remaining material removed except cellulose in the pulping process is commonly referred to as black liquor.

The black liquor contains a large amount of lignin (wood sugar), which is a high molecular material. However, it is difficult to process the lignin contained in the black liquor. We reuse.

Currently, as a method for effectively using such a black liquid, Korean Patent No. 0385580 discloses a method of manufacturing a dispersant for improving and homogenizing dispersion, cement, and ready-mixed concrete by dispersing the black liquid by chemical treatment. Patent No. 0963822 discloses a concrete admixture prepared by oxidizing black liquor with an oxidizing agent such as ozone, hydrogen peroxide, and fenton reagent. However, studies on the production of porous carbon materials having a high specific surface area using pure black liquor obtained in the papermaking process are incomplete.

Accordingly, the present inventors have made intensive efforts to develop a porous carbon material having a high specific surface area from pure black liquor. As a result, an acid is added to the black liquor to form a precipitate, and the formed precipitate is neutralized to extract lignin, followed by heat treatment of the extracted lignin. In the case of activating by injecting steam, it was confirmed that the porous activated carbon having a high specific surface area can be produced by a simple treatment process, thereby completing the present invention.

The main object of the present invention is to provide a method for producing porous activated carbon based on black liquor that can produce porous activated carbon having a high specific surface area by a simple treatment process.

In order to achieve the above object, the present invention comprises the steps of (a) adding an acid to the black liquid to form a precipitate; (b) neutralizing the precipitate formed and then drying to extract lignin; (c) heat treating the dried lignin to obtain carbonized lignin; And (d) injecting water vapor into the carbonized lignin to produce a porous activated carbon.

The method for producing porous activated carbon using black liquor as a raw material according to the present invention can simplify the process and make it practical, and can obtain a high specific surface porous carbon material only by using the black liquor obtained in the papermaking process, Reuse is very effective economically.

1 is a schematic diagram showing a lignin extraction process according to the present invention.
Figure 2 is a graph of the TGA measurement results of lignin extracted by the manufacturing method according to the present invention.
Figure 3 is a graph of the TGA measurement results of lignin carbonized by the manufacturing method according to the present invention.
Figure 4 is a graph of the ¹ H-NMR spectrum analysis of the lignin extracted by the manufacturing method according to the present invention.
Figure 5 is a graph of a spectrum (b) analysis of the magnified portion of the ATR-FTIR spectrum (a) and peaks of the lignin extracted by the production method according to the present invention.
Figure 6 is a graph of the XRD measurement results of lignin carbonized by the manufacturing method according to the present invention.
7 is an SEM measurement image (a: × 100, b: × 300) of the lignin extracted by the manufacturing method according to the present invention.
8 is an SEM measurement image (a: × 100, b: × 300) of the lignin carbonized by the manufacturing method according to the present invention.
9 is an isothermal adsorption curve graph of lignin (A) and porous activated carbon (B) carbonized by the manufacturing method according to the present invention.

The present invention in one aspect, the present invention comprises the steps of (a) adding an acid to the black liquor to form a precipitate; (b) neutralizing the precipitate formed and then drying to extract lignin; (c) heat treating the dried lignin to obtain carbonized lignin; And (d) injecting water vapor into the carbonized lignin to produce a porous activated carbon.

More specifically, in the method for producing porous activated carbon according to the present invention, a precipitate is formed by adding an acid to a black liquid which is a by-product generated from a paper manufacturing process, neutralizing the formed precipitate, and then drying to extract lignin. The extracted lignin is carbonized by heat treatment, and then injected with water vapor to prepare porous activated carbon having a high specific surface area.

The black liquor is a liquid remaining when steaming or boiling pulp material, and is a black substance having a strong alkalinity of pH 10 or higher due to cooking chemical treatment such as sodium carbonate and sodium sulfide. This black liquor is added acid to form a precipitate.

The acid may be used as long as it is an acid capable of lowering the pH of the black liquid to form a precipitate, and is preferably selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, and mixtures thereof. At this time, the pH of the black liquid to which the acid is added is preferably 2. If the pH is higher or lower than 2 in the process of lowering the pH of the black liquid, there is a problem that the yield of lignin to be extracted is low.

The precipitate formed by the addition of acid to the black liquor is filtered through a decompression device and the like, and the distilled water is used to neutralize the pH of the precipitate to 5-6. The neutralized precipitate is dried for 1 to 2 days at 40 ℃ ~ 50 ℃ to extract the lignin.

Lignin extracted as described above is carbonized by heat treatment at 600 to 1000 ℃ at a temperature increase rate of 1 to 10 ℃ / min. In this case, when the heat treatment temperature is less than 600 ℃, it is difficult to produce activated carbon having a high specific surface area, and when it exceeds 1000 ℃, it is difficult to maintain a fine pore structure by rapidly degrading lignin, so that it is difficult to secure uniformity of quality. In addition, when carbonizing lignin at a temperature rising rate of less than 1 ℃ / min, there is a disadvantage in that the manufacturing process time is long, and when carbonized at a temperature rising rate exceeding 10 ℃ / min is not properly carbonized lignin There is this.

Preferably, the heat treatment is performed in an inert atmosphere, and the inert atmosphere may be, for example, nitrogen or argon atmosphere.

By the heat treatment, an alkaline component such as sodium contained in the black liquor may act as a chemical activator to be inserted between the carbon layers of the lignin, thereby increasing the interval between the carbon layers, thereby increasing the BET specific surface area of 350 to 450 m ² / g. Activated carbon may be prepared.

The carbonized lignin is activated with carbonized lignin by injecting steam in an inert atmosphere, wherein the carbonized lignin is heated to 850 ° C. at 1 to 10 ° C./min, and then maintained for 30 minutes to 2 hours. Inject water vapor under conditions. If, when lignin is activated at a temperature increase rate of less than 1 ℃ / min, there is a disadvantage that the manufacturing process time is long, and when activated at a temperature rising rate exceeding 10 ℃ / min there is a problem that the activation is not made properly. . In addition, when the activation isothermal time is less than 30 hours, the activation of lignin is not properly performed, and when the isothermal time exceeds 2 hours, there is a problem that the yield according to the amount of steam input is low.

Water vapor injection into the carbonized lignin described above can produce more pyrolysis from around the carbonized lignin pores to produce porous activated carbon having a high specific surface area.

The method for producing porous activated carbon based on black liquor according to the present invention can be realized by producing lignin extracted from black liquor through carbonization and activation, thereby simplifying the black liquor treatment process, and having a high specific surface area using only black liquor without other additives. Not only can a porous carbon material be obtained, but it is also economically effective by reusing waste products.

The present invention is prepared by the above-described manufacturing method, it is possible to produce a porous activated carbon having a BET specific surface area of 1650m ² / g ~ 1800m ² / g. The manufactured porous activated carbon can be utilized for liquid or gaseous adsorption because it is manufactured without any additives and thus has a lower cost than the existing activated carbon, and has a specific surface area higher than that of the existing activated carbon.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only intended to illustrate the invention, it will be apparent to those skilled in the art that the scope of the invention is not to be construed as limited by these examples.

Example  One: Black liquor  Production of Porous Activated Carbon as Raw Material

1-1: Lignin Extraction Stage

Sulfuric acid diluted with 4M (22% concentration by mass) was added to 800 g of black liquor having a pH of 13 provided from Moorim P & P (Donghae Pulp) to lower the pH of the black liquor to 2 and stirred to form a precipitate. The precipitate thus formed was stirred for about 1 hour and then neutralized to precipitate pH 6 with distilled water using a pressure reducing device. The neutralized precipitate was dried in an oven at 45 ° C. for about 1 day, and the dried precipitate was decomposed into powder form using induction, and then lignin was extracted without additional purification (FIG. 1).

1-2: lignin carbonization step

100 g of lignin extracted in Example 1-1 was heat-treated stepwise from room temperature using a tubular silconit carbonization furnace made of sus material. At this time, the final heat treatment temperature was set to 600 ℃, 850 ℃ and 1000 ℃, the temperature increase rate according to the final heat treatment temperature was set to 1 ℃ / min, it was carried out in a nitrogen atmosphere. The lignin thus heat-treated was cooled at room temperature to obtain carbonized lignin.

1-3: lignin activation stage

The lignin carbonized in Example 1-2 was heated at a rate of 1 ° C./min from normal temperature to a final temperature of 850 ° C. using a carbonization furnace composed of a sus tube and a silconit heating element in a nitrogen atmosphere, followed by 60 minutes in an isothermal state. The activation process was performed by supplying 3ml / min of water vapor through a metering pump (Cole-Parmer Instrument Company, Masterflex MODEL NO. 7524-05), which is a steam supply device. The activated lignin was cooled to room temperature to prepare porous activated carbon.

Experimental Example  One: Thermal stability  Measure

In order to observe the weight loss rate of the lignin and the porous activated carbon prepared in Example 1, it was measured using a thermogravimetric analyzer (TGA Q500, TA Instruments).

As a result, in the case of the extracted lignin, as shown in FIG. 2, the weight loss of about 2 to 3% observed near the initial 100 ° C removes or removes moisture present in the lignin as the temperature increases. It was shown that the change amount by. In addition, some of the weight loss may be caused by the reaction of the nitrogen gas sent during the measurement and the oxygen functional groups present in the lignin to be removed. Later, when the weight loss rate was slowed down to 200 ° C, the reaction caused by heat occurred, the lignin melted, the material was removed in the process, and the structural change occurred, and it was judged that the weight loss occurred. . Since the extracted lignin was not purified, the weight loss due to the decomposition of hemicellulose appeared at around 290 ° C, and the degradation of lignin occurred at around 380 ° C. This was also confirmed in the DTG graph, and it was observed that the weight loss occurred rapidly at around 100 ° C, 290 ° C, and 390 ° C. As a result, it can be seen that about 34% of the total weight of the lignin extracted at 800 ℃.

In addition, in the case of carbonized lignin, as shown in FIG. 3, the weight change of carbonized lignin at 1000 ° C. was found to be small, thereby indicating higher thermal stability. In addition, the difference in weight change was slightly higher between the samples at about 7% between 600 ° C. and 850 ° C., but at 2% between 850 ° C. and 1000 ° C .. It is believed that more crystallization and cyclization by carbonization at 850 ° C. than at 600 ° C. resulted in more thermal stabilization.

Experimental Example  2: nuclear magnetic resonance spectroscopy

Nuclear Magnetic Resonance (BRUKER BIOSPIN, AVANCE III 400) was used to observe the chemical structure of extracted lignin, 1H-NMR probe was used for chemical structure analysis, and dimethyl was used as a solvent to dissolve lignin. sulfoxide (DMSO-d6) was used.

As a result of observing the chemical structure of the lignin extracted in Example 1-1, as shown in Figure 4, the peak of dimethyl sulfoxide (DMSO-d6) used as a solvent was confirmed at 2.5 ppm, H ₂ contained in the solvent The hydrogen of O appeared at 3.4 ppm. The characteristic peak of lignin showed hydrogen present in aliphatic group at 1.227 ppm, and hydrogen peak of -CH- affected by -CH ₂ OH at 2.182 ppm. Hydrogen in the methoxyl group was strong at 3.5 ppm and at 3.756 ppm a hydrogen peak of -CH ₂ -located on the oxygen side of -COO-. The hydrogen peak located at -HC-O-CH _2- , the ether group in contact with -CH-, appeared around 4.2 ppm, and the hydrogen in the aromatic ring, one of the important structures of lignin, was 6.5-7.5. Several peaks were found between ppm. Therefore, it was found that lignin was successfully extracted from the black liquor based on the above results.

Experimental Example  3: ATR - FTIR  Spectroscopic analysis

In order to investigate the chemical functionalities of the lignin extracted in Example 1-1, an infrared attenuated total reflectance-fourour Transform Infrared: Nicolet 6700 FT-IR Spectrometer, Thermo Fisher Scientific Inc. , ATR crystals were measured using Znse (zinc selenide).

The results of the measurements in the 3395 cm ^-1 large and gentle alcoholic and phenolic OH peak was observed, 2936 cm ^- was observed in the CH ₃ peak ¹ and 2842 cm ^-1 (Fig. 5A). In addition, it is enlarged in FIG. 5B showing a part of the square box located in FIG. 5A that is difficult to distinguish. As shown in FIG. 5, major absorption peaks of lignin could be confirmed through spectral analysis. In particular, the C = O peak at the β position and the C = O peak at the α and γ positions of the phenylpropane unit were identified. CO peaks of primary alcohols were observed around 1032 cm ^-1 , and C = C and CH peaks of aromatic rings were found around 1500 cm ^-1 and 850 cm ^-1 , respectively. The most important peaks are the CO and CH peaks of the syringyl ring found at 1313 cm ^{- 1} and 1111 cm ^-1 , and the CO and CH peaks of the guaiacyl ring found near 1220 cm ^-1 and 1810 cm ^-1 . . The syringyl ring and guaiacyl ring are mainly found in hardwoods. Considering that the lignin used in this experiment was obtained from black liquor, a by-product of the pulp process using various types of hardwoods, the main absorbance peak of the extracted lignin was well in the spectrum. It can be seen that.

Experimental Example  4: X-ray diffraction  analysis

A high resolution x-ray diffractometer (D / MAY-2500 / PC, Rigaku) was used to investigate the effect of carbonization process conditions on the crystallinity change of carbonized lignin in Example 1-2. It was. The scanning range was 2θ = 2 ° ~ 60 °, and the radiation used was Kα and measured by Cu as the targeting material.

As a result, as shown in Figure 6, as the lignin carbonized at a high temperature it was confirmed that the 2θ peak around 20 ° moves at an increasingly higher angle. This was confirmed by calculating the value of d ₍₀₀₂₎ by Bragg's Equation (d _{( hkl )} = λ / 2sinθ). The higher the carbonization temperature, the denser the turbostratic structure, the graphitic structure, and the less amorphous the sample was. It also shows that the higher the intensity of the peak, the above results. In general, at 600 ° C, the peak form was gentle, but the peak narrowed with increasing temperature. However, when comparing 850 ℃ and 1000 ℃ did not show a big change, 850 ℃ and 1000 ℃ is a structural temperature range is difficult to find a difference.

Experimental Example  5: Raman spectroscopy Crystallization Analysis by

The Raman spectrometer (InVia raman microscope, Renishaw Plc.) Was used to investigate the effect of carbonization on chemical properties and crystallinity. Raman spectroscopy was performed using an Nd YAG laser and measured at a wavelength of 514 nm.

As a result of the measurement, as shown in Table 1, the Raman spectrum typically shows two strong peaks, classified into a D band representing an amorphous portion and a G band representing a graphitized or crystalline portion. D bands appeared around 1340 cm ^-1 and G bands were observed mainly around 1590 cm ^-1 . The crystallinity of the sample can be analyzed by comparing the relative intensities (D / IG) of the D band and the G band. The prominent results in Table 1 show that the ID / IG value increases as the carbonization temperature increases in each compounding condition. Raised together. As the carbonization temperature was increased, the graphite and amorphous crystallization of the sample were made, but the carbonization temperatures 600 ° C., 850 ° C., and 1000 ° C. set in the present experimental example were insufficient for graphite and crystallization. In addition, as the heat acts on the sample, cracks and defects occur in the structure, resulting in an increase in the level of disorder, resulting in an increase in the D band value and thus an ID / IG value.

Carbonization temperature ID IG ID / IG
600 ℃ 2350.72 3396.65 0.692 850 ℃ 2461.77 2949.96 0.835 1000 ℃ 1496.08 1653.43 0.905

Experimental Example  5: Elemental Analysis

An elemental analyzer (Flash 2000, ThermoFisher) was used to investigate the effect of carbonization on the chemical composition of lignin. The elemental analysis was carried out to measure the carbon content, hydrogen content, and nitrogen content of each sample. The unmeasured oxygen content was calculated as the remaining content except the aforementioned three elements in the total content.

As a result, Table 2 below shows the results of analyzing the elements of the lignin extracted in Example 1-1, Table 3 described by analyzing the elements of the lignin carbonized in Example 1-2. As a result, as shown in Table 3, it can be seen that the carbon amount increases as the carbonization temperature increases.

division carbon (%) Hydrogen (%) Oxygen (%) Nitrogen (%) Extracted lignin 60.372 5.568 33.820 0.240

division carbon (%) Hydrogen (%) Oxygen (%) Nitrogen (%) Lignin carbonized at 600 ℃ 88.386 2.524 8.513 0.577 Lignin carbonized at 850 ℃ 93.358 0.625 5.396 0.621 Lignin carbonized at 1000 ℃ 94.373 0.269 4.032 1.326

Experimental Example 6: Surface Observation Using Scanning Electron Microscope

Scanning Electron Microscope (JEOL, JSM-6380) was used to measure the surface changes of the extracted lignin and carbonized lignin. The surface of all samples used for the measurement was measured after coating the surface of the sample prepared by sputtering method with platinum (Pt) for 3 minutes to give conductivity.

First, as a result of observing the surface of the lignin extracted in Example 1-1, as shown in Figure 7, it was found that the particles are agglomerated to form large lumps.

In addition, as a result of observing the surface of the lignin heat-treated at 850 ° C. of the lignin carbonized in Example 1-2 with a scanning electron microscope, as shown in FIG. 8, the surface of the carbonized lignin appeared in a completely different form from before heat treatment. Could know. Before the heat treatment, the lignin was shown to form agglomerates, while the heat treatment showed that the lignin mass disappeared and the smooth surface was observed. This is caused by melting and boiling as the temperature is applied to the lignin, which then hardens to form a foamed foam. Judging.

Experimental Example 7: Surface Observation Using Scanning Electron Microscope

A specific surface area analyzer (Surface Area & Pore Size Analyzer, ASAP2020, Micromeritics Inc., USA) was used to investigate the specific surface area and pore characteristics of activated carbon. Pore characteristics were evaluated by isothermal adsorption analysis of N ₂ at 77K temperature by liquid nitrogen, and heat activated at 850 ° C. to activate carbonized lignin (Example 1-2) and the carbonized lignin. The specific surface area by the BET method of (Example 1-3) was measured. For accurate measurement, the experiment was performed after removing the gas in the tube containing the sample under vacuum condition at 300 ° C. for 10 hours.

As a result, as shown in FIG. 9, the activated sample of FIG. 9 (B) is well adsorbed and desorbed, whereas the carbonized sample of FIG. 9 (A) is more desorbed than the amount adsorbed after adsorption. It appeared to be happening. This may be due to the fact that the volatile mass in the waste pores present in the carbonized lignin was opened by adsorption and desorption of nitrogen and escaped out of the pores together.

In addition, Table 4 below shows the BET value and the pore type results of the lignin carbonized in Example 1-2 and the porous activated carbon prepared in Example 1-3. In the case of the lignin carbonized in Example 1-2, it was measured with a BET value of 400 m ² / g (the tens and tens of digits in the BET value can be omitted because the flow is large in terms of density and proficiency). , 96.2% of the micro-pores were found, whereas in the porous activated carbon prepared in Example 1-3, the BET value of 1,718 m ² / g and the micro-pores of about 59.3% appeared to exist. . It can be seen that the porous activated carbon of the present invention prepared by steam activation has a BET value four times higher than that of the lignin activated carbon prepared by simply carbonization.

division BET (m ² / g) Micropore Area (m ² / g) External Surface Area (m ² / g) Carbonized lignin
(Example 1-2) 402 387 15 Porous activated carbon
(Example 1-3) 1,718 1,019 699

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. It is therefore intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

Claims (9)

Method for producing a porous activated carbon, comprising the following steps:
(a) adding acid to the black liquor to form a precipitate;
(b) neutralizing the precipitate formed and then drying to extract lignin;
(c) heat treating the dried lignin to obtain carbonized lignin; And
(d) preparing porous activated carbon by injecting water vapor into the carbonized lignin.
The method of claim 1, wherein the acid of step (a) is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid and mixtures thereof.
The method of claim 1, wherein the pH of the black liquor is adjusted to 2 when the acid of step (a) is added.
According to claim 1, wherein the neutralization of the step (b), the method of producing a porous activated carbon, characterized in that to adjust the pH to 5 to 6.
The method of claim 1, wherein the drying of step (b) is performed for 1 day to 2 days at 40 ° C to 50 ° C.
The method of claim 1, wherein the heat treatment of step (c) is performed at 600 ° C to 1000 ° C at a heating rate of 1 ° C / min to 10 ° C / min.
The method of claim 1, wherein the step (c) is performed in an inert atmosphere.
The method of claim 1, wherein the step (d) of the porous activated carbon, characterized in that the water vapor is injected under conditions maintained for 60 minutes after raising the temperature to 850 ℃ at 1 ℃ / min ~ 10 ℃ / min in an inert atmosphere Manufacturing method.
The method of claim 1, wherein the steam injection of step (d) is performed at 3 ml / min.

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