KR0183287B1 - Method of manufacturing precursor for carbon material - Google Patents

Abstract

The present invention relates to a method for producing precursors of various carbon materials, and more specifically, to an aromatic compound having 10 or more carbon atoms at room temperature under a cocatalyst consisting of aluminum chloride and nitrobenzene, and then raising the temperature to 300 ° C. or lower. The present invention relates to a method for preparing a precursor for a carbon material by polycondensation reaction while producing a petroleum pitch and carbonizing or graphitizing the same at a temperature of 500 ° C. or higher. Precursors prepared by the process of the invention are particularly preferred for the production of electrodes for lithium secondary batteries or activated carbon fibers.

Description

Manufacturing method of precursor for carbon material and use thereof

1 is a process diagram schematically showing a method for producing a precursor for a carbon material according to the present invention.

2 is a graph showing the results of thermogravimetric analysis of pitches prepared according to the present invention.

3 is a photograph showing the optical structure (polarization microscope) analysis results of the precursor for carbon material prepared according to the present invention.

4 is a graph showing the results of X-ray diffraction analysis of the precursor for a carbon material prepared according to the present invention.

5 is a graph showing the Raman spectroscopic analysis of the precursor for carbon material prepared according to the present invention.

The present invention relates to a method for preparing precursors of various carbon materials and uses thereof, and more particularly, to aromatic compounds having 10 or more carbon atoms (0.1 volume of crude oil) obtained in a petrochemical process for reforming a paraffinic hydrocarbon to an aromatic hydrocarbon. %, Hereinafter referred to as C _{10 +} ) at room temperature reaction (primary reaction) in a cocatalyst (up to 30 parts by weight of aluminum chloride and up to 30 parts by weight of nitrobenzene), and then heat treatment while raising the temperature to 300 ° C or lower. Through the polycondensation reaction (secondary reaction) to produce a petroleum pitch having the desired characteristics, and then carbonized or graphitized at a high temperature of more than 500 ℃ to prepare a precursor that can be used as a carbon material for various uses It is about.

Recently, with the growing interest in environmental pollution, the issue of automobile exhaust gas, which is known to be the main cause of air pollution, has been seriously discussed. The Clean Air Act of the United States, which was implemented between 1994 and 1996, is a major vehicle emission hydrocarbon. In addition to a 30% reduction in current emission levels, nitrogen oxides and suspended particulates are expected to be reduced by 60%.

As one of the countermeasures, early commercialization of electric vehicles is required. For this purpose, it is necessary to develop a new secondary battery having a long driving distance, a short charging time, a high output energy density and a long charge / discharge repeat life after a single charge. . In addition, as the demand for portable telephones, notebook computers, etc. is exploding due to the rapid arrival of information and multimedia eras, the development of high performance rechargeable secondary batteries, which are their main components, is urgently needed.

In line with these trends, research and development from conventional nickel, hydrogen, and cadmium-based secondary batteries to lithium-based secondary batteries whose performance has been greatly improved has been the mainstream, and particularly, anodes of lithium secondary batteries. A wide range of researches on the performance improvement of carbon electrodes, which have been in the spotlight, are being conducted by domestic and foreign researchers. Until now, it is known that the structure morphology and crystal structure of the carbon electrode are important factors in determining the electrode performance. For example, the lamination size (Lc002) of the carbon crystal, which is an electrode material, is 100 to 200 mW. It is known to have a minimum value and to increase the charging capacity if smaller or larger than this [Morinobu Endo, Jun-ichi Nakamura, Yutaka Sasabe, Tetsuya Takahashi and Michio Inagaki, TANSO, No. 165, 282-287 (1994).

Therefore, the inventors have focused on the fact that the structure and crystallinity of the carbon electrode are important factors for the performance of the final battery product, in particular, the charge / discharge capacity. In order to confirm the possibility of practical use of secondary battery with better performance, the activated carbon fiber has emerged as an adsorbent for atmospheric purification or catalyst for chemical reaction process, which has improved adsorption performance from the composition of carbon material precursor manufactured. (active carbon fiber) to check the possibility of use.

On the other hand, the function of the carbon fiber is known to be determined by the size of the micropores generated by the activation and the physical and chemical properties of the substrate. For example, a method of selectively separating benzene and cyclohexane by controlling the micropores of phenolic resin-based activated carbon fibers has been reported. Also, in the case of using PAN (Poly acrylonitrile) -based activated carbon fibers, if the activation is low, the final Nitrogen remains in the product, resulting in specific selectivity as an adsorbent and catalyst, and an example of using this as an adsorbent for NOx or SOx has also been reported (Japanese Patent Laid-Open No. 51-132193).

Until now, in order to prepare precursors for carbon materials, pitch oils having a constant structure and molecular weight are mainly solvent-extracted from petrochemical process residue oil or coal tar, and manufactured by heat treatment. As a large amount of solvent is used for the extraction, ancillary expenses are required, which is more than half of the total cost of the carbon material manufacturing process except for the carbonization process, which has been a significant factor in the price increase of the produced product.

In order to solve this problem, Mitsubishi Gas Corp. of Japan uses raw material pitches from pure compounds (e.g., naphthalene, methylnaphthalene, anthracene, etc.) instead of solvent extraction of desired pitch fractions from complex and heavy process residues. Was developed to produce a unique method for preparing precursors for carbon materials having relatively uniform physical properties. However, there is an economic burden such as the need for additional equipment for the process safety reasons that the raw material is more expensive than the conventional method and the super acid HF / BF ₃ must be used during operation [I. Mochida , K. Shimizu, Y. Korai, H. Otsuka, Y. Sa kai and S. Fujiyama, Carbon, 28, 311 (1990)]. In addition, there is a method of manufacturing a pitch by polycondensing quinoline (quinoline or isoquinoline) in order to manufacture a carbon-containing carbon material, and the carbon fiber using the pitch, but also the price of the raw material (quinoline) This expensive drawback has limited commercial value [I. Mochida, KH An and Y. Korai, Carbon, 33, 1069-1079 (1995).

Accordingly, an object of the present invention is to prepare a high value-added carbon product and a catalyst in the production of the same by using a low price (100,000 won / ton) petrochemical process by-product (C ₁₀₊ ) directly as a raw material without a separate process such as distillation or solvent extraction. The present invention provides a method for producing various types of precursors for carbon materials having better performance by controlling the amount, heat treatment temperature, and time.

Another object of the present invention to provide a method for using the precursor for the carbon material prepared by the above method for a specific use.

The method of the present invention for achieving the above object is to produce a petroleum pitch by reacting an aromatic compound having at least 10 carbon atoms at room temperature under a co-catalyst made of aluminum chloride and nitrobezen, and then polycondensing the reaction while raising the temperature to 300 ° C or lower. And again carbonizing or graphitizing at a temperature of 500 ° C. or higher.

Hereinafter, the method of the present invention will be described in more detail.

Some of the light oil (naphtha) obtained by refining crude oil undergoes a reforming process for the production of petrochemical products (benzene, toluene, xylene) or gasoline blended samples, wherein aromatics having a certain carbon number (more than 10 carbon atoms) The compound is obtained as a byproduct. This is a side reaction that cannot be used for its original purpose, but its molecular weight is relatively uniform, its composition is constant, and its aroma is about 57%, so it is suitable for use as a raw material for polycondensation carbonization process for carbon materials. It has

Accordingly, the present inventors have made efforts to develop and manufacture _{C10 +} having a low cost as a raw material for carbonaceous materials and having excellent physical properties. First, by varying the polycondensation reaction rate of the raw material by adjusting the concentration of the cocatalyst and the reaction temperature, the structure of the carbon material could be manufactured by changing the structure thereof. The pitch thus prepared may be used to manufacture a carbon electrode for a lithium secondary battery negative electrode and a precursor for activated carbon fiber through a carbonization process.

According to the present invention, 0.01 to 30 parts by weight of aluminum chloride (AlCl ₃ ) and 0.01 to 30 parts by weight of nitrobenzene cocatalyst are reacted at room temperature with respect to 100 parts by weight of C ₁₀₊ . At this time, when aluminum chloride exceeds 30 parts by weight, it is difficult to remove the aluminum component from the reaction product, and when the amount is less than 0.01 parts by weight, the reaction effect is almost insignificant and the efficiency is lowered. If the nitrogen content in the product is excessively unsuitable for the required physical properties, and less than 0.01 part by weight, there is a problem in that the reaction assisting effect as a cocatalyst is insufficient.

The reaction is then heated to a temperature of 300 ° C. or less at a rate of 1-4 ° C. per minute and then heat treated for at least 2 hours. The temperature increase rate is preferably maintained in order to prevent structural deformation (nonuniformity) due to the rapid reaction progress, the reaction is rapidly carbonized (solidifying) appears when the final temperature exceeds 300 ℃.

After the reaction, the remaining aluminum chloride is removed by washing several times with aqueous hydrochloric acid solution, and other residual cocatalyst is washed with methanol. The resulting reactant is then vacuum dried at about 60 ° C. to a desired property, such as a softening point of about 200 ° C., and a C / H ratio of about 1.1. (The above properties are preferred for modified pitch properties suitable for carbonizing with precursors for carbon materials. Pitch).

The pitch thus prepared may be carbonized or graphitized for at least 1 hour at a temperature of 500 ° C. or higher for use in the production of an electrode for a lithium secondary battery, or by spinning to produce a carbon material precursor that may be used for the production of activated carbon fibers. . At this time, if the temperature condition is less than 500 ℃ carbonization or graphitization does not proceed, and as the temperature is increased, the structure or physical properties of the final product increases the degree of carbonization, and also the crystal size increases and the lamination interval is narrowed To change.

Meanwhile, according to the present invention, when adjusting the concentration of nitrobenzene used as the cocatalyst, it is possible to control the amount of nitrogen introduced into the final product, thereby producing a carbon material having special selectivity. In the case of a carbon material produced using about 20 parts by weight of nitrobenzene, the nitrogen content of about 2% by weight has an important value as adsorption and catalyst as described above. In addition, by changing the carbonization temperature conditions it is possible to adjust the structural form or physical properties (nitrogen content) of the final product according to the desired use.

Accordingly, the present invention is much the combustion if the raw material of the carbon material precursor C ₁₀₊ Considering that vast amount of 0.1% by volume of low-cost, yet crude oil, as well as the economic bottom line to create a high added value by the fuel oil is a solid carbon commercialized It is a process development that has great advantages in terms of environmental protection, such as reducing air pollutants that are concerned about the occurrence of.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

After 100 parts by weight of C ₁₀₊ is taken, 30 parts by weight of aluminum chloride powder is added thereto and reacted at room temperature while slowly adding 20 parts by weight of nitrobenzene. At the end of the reaction, the temperature is increased to 250 ° C. at a rate of temperature rise of 2 ° C. per minute. The aluminum chloride contained in the product thus obtained was washed several times with 0.2 normal aqueous hydrochloric acid solution, washed 2-3 times with methanol to remove residual nitrobenzene, and then vacuum dried at about 60 ° C. The yield and softening point of the C ₁₀₊ and modified pitch samples, and the results of elemental analysis are shown in Table 1 below. The softening point was measured using a METTLER FD80 model. In Table 1, the sample name, for example, NB20-250 refers to a sample prepared under a cocatalyst of 20 parts by weight of nitrobenzene and subjected to polycondensation at 250 ° C.

Example 2

Instead of 20 parts by weight of nitrobenzene in Example 1 was added 30 parts by weight to prepare a modified pitch for the carbon material in the same process, the results are shown in Table 1 below.

Example 3

In Example 1 was carried out in the same manner except that the temperature was increased to 280 ℃ at a temperature increase rate of 2 ℃ per minute, and the heat treatment, the results are shown in Table 1 below.

Example 4

Except that the addition of 30 parts by weight instead of 20 parts by weight of nitrobenzene in Example 3 was carried out in the same manner, the results are shown in Table 1 below.

As can be seen from Table 1, it was found that the carbonization degree (C / H) of the pitch increases as the reforming temperature increases, and the degree of carbonization increases as the content of nitrobenzene used as the cocatalyst increases. Of course, the nitrogen (N) content in the pitch was also found to increase. Most of the samples showed the appropriate range of carbonization (a C / H ratio of about 1.1 and a softening point of about 200 ° C), which is expected to be used as a carbon material precursor in the future.

Meanwhile, thermogravimetric analysis was performed to determine the carbonization yield of the pitches prepared in Examples 1 and 2, and the results are shown in FIG. Sample NB20-250 (Example 1) exhibited carbonization yields of 51 wt% and 25 wt%, respectively, at 500 ° C and 600 ° C conditions, and sample NB30-250 (Example 2) at 66 wt% and 43 wt%, respectively. As the content of nitrobenzene used as a catalyst was within the range of 30 parts by weight, it was found that the yield of the modified pitch increased as the content increased. For reference, the formula for calculating the yield of carbonization is as follows.

Carbonization yield (% by weight) = sample mass after carbonization / sample mass before carbonization × 100

[Examples 5 to 12]

The examples were performed on carbon material precursor samples obtained by carbonizing or graphitizing the pitch prepared at 250 ° C. of Examples 1 and 2 at 500 ° C., 1000 ° C. and 2400 ° C., respectively.

The yields, softening points, and elemental analysis of the carbon precursors of Examples 5 to 8 are shown in Table 2 below. The sample name shown in Table 2, for example, NB20-250 / 500 is a carbon material precursor sample obtained by carbonizing the modified pitch obtained by heat treatment to 250 ℃ under 20 parts by weight of nitrobenzene in the cocatalyst in Example 1 Means.

As can be seen from Table 2, while changing the content of the cocatalyst (nitrobenzene) used and the carbonization temperature conditions, the nitrogen content in the final product (carbon material precursor) and the like can be adjusted according to the desired use at this time In this case, by using about 2% by weight of nitrogen in the final carbon product, the utilization value as an activated carbon fiber, which has started to be recognized as a catalyst or an adsorbent in general chemical processes or environmental facilities as described above. Is expected.

On the other hand, in Fig. 3 (a) and (b), the optical structures of Example 5 (NB20-250 / 500; Fig. 3a) and Example 6 (NB30-250 / 500; Fig. 3b) shown through a polarizing microscope Is shown in the photo. Example 5 shows a mosaic optical structure and Example 6 shows an isotropic optical structure. This is the same as the result of Table 2, it was confirmed that the optical (polarization) structure of the final carbon product can be adjusted by changing the content of the cocatalyst used and the reaction temperature conditions, and the appropriate 2.81% by weight of nitrogen In the case of Example 6 showing the component content of the isotropic optical structure is determined to be more suitable for the production and utilization of activated carbon fibers in the form of short fibers.

In addition, in order to grasp the crystal structure of the carbon material precursor according to the change of the cocatalyst (nitrobenzene) content and the heat treatment temperature, the sample graphitized at 1000 ℃ and 2400 ℃, respectively; Respective X-rays for Example 9 (NB20-250 / 1000), Example 10 (NB30-250 / 1000), Example 11 (NB20-250 / 2400) and Example 12 (NB30-250 / 2400) The results of diffraction analysis (DIMAX 1200) and Raman spectroscopy (KNOVA 305) are shown in Table 3 below, and in particular, Examples 11 and 12 are graphically shown in FIGS. 4 and 5.

As can be seen from Table 3, when graphitized at 2400 ℃, the crystal structure was shown a large difference according to the concentration of nitrobenzene as a cocatalyst, 30 wt% compared to the sample having a cocatalyst content of 20 parts by weight. As the crystallinity (crystal size) of the denier sample was significantly low, it was confirmed that the crystal structure of the final carbon product according to the application could be easily adjusted by controlling the reaction conditions as in the above-described results. This phenomenon results in a change in the peak at the diffraction angle (26 °) of the X-ray diffraction of FIG. 4, and 1580 cm of the Raman spectroscopy of FIG. It is also well understood that the magnitude of the peak in the vicinity also changes significantly. Table 3 shows these in terms of numerical values, and in particular, in the case of the lamination interval value, it can be seen that the result of the satisfactory level as a precursor of the carbon electrode material for lithium secondary battery excellent in the above-described charge and discharge capacity.

Claims (5)

100 parts by weight of an aromatic compound having 10 or more carbon atoms, which is a by-product obtained from the petrochemical process of reforming a paraffinic hydrocarbon into an aromatic hydrocarbon, was reacted at room temperature under a cocatalyst composed of 0.01 to 30 parts by weight of aluminum chloride and 0.01 to 30 parts by weight of nitrobenzene. Polycondensation reaction while raising the temperature up to 300 ° C or less to produce a petroleum pitch, and further carbonized or graphitized at a temperature of 500 ° C or more. The method of claim 1, wherein the rate of increase in temperature during the polycondensation reaction is 1 to 4 ° C. per minute. The carbonaceous material as claimed in claim 1, wherein the reactant produced during the polycondensation reaction is vacuum dried at about 60 ° C. to produce a petroleum pitch having a C / H ratio of about 1.1 and a softening point of about 200 ° C. 3. Method for preparing a precursor. The method of claim 1, wherein the carbonization or graphitization is performed at 500 ° C. or higher for at least 1 hour. A method of using a precursor prepared by the method of any one of claims 1 to 7 in the production of an electrode for a lithium secondary battery or an activated carbon fiber.