KR101602693B1 - Method for manufacturing alumina pellet - Google Patents

Abstract

A method for producing an alumina compact is provided. Specifically, the present invention relates to a method for producing a boehmite gel, comprising the steps of: stirring a mixed solution obtained by mixing boehmite, silica, a peptizer and a solvent as alumina precursors to form a boehmite gel; Aging for a period of time to 24 hours, and firing the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores. According to the method, the pore characteristics of the alumina compact having the mesopores can be maintained without using the surfactant through the method of producing the alumina compact of the present invention. Accordingly, since a step for drying the surfactant is not required, the manufacturing process can be simplified and the manufacturing cost can be reduced. In addition, the characteristics of the mesopores of the alumina compact having mesopores can be easily controlled by the content of silica and the aging process.

Description

[0001] METHOD FOR MANUFACTURING ALUMINA PELLET [0002]

The present invention relates to a method for producing an alumina compact, and more particularly, to a method for producing an alumina compact having a medium pore size from boehmite which is an alumina precursor.

In order to uniformly disperse active components such as catalysts and adsorbents, alumina carriers and the like are mainly used as carriers excellent in physical and chemical functions. The alumina support has a pore volume of a wide specific surface area and various pore sizes, which may be advantageous for supporting a metal or metal oxide catalyst. The alumina support has a melting point of 2000 占 폚 and is stable chemically and thermally so that it exhibits excellent strength at high temperature and supports a noble metal catalyst such as platinum, palladium, ruthenium, iridium or rhodium, Can be used for the process.

Generally, it is known that the size of the mesopores that can be realized in the alumina carrier is 3 nm to 4 nm, and the granular size of the granules is 0.3 ccg ^-1 , which can be controlled by using cationic, anionic, or neutral ionic surfactants. In the use of the alumina support as a carrier such as a catalyst or an adsorbent, pore characteristics of the alumina support are important factors. This is because the diffusion or dispersion of active components such as catalysts or adsorbents in the pores of the alumina support depends on the size and distribution of the pores of the alumina support.

Since alumina prepared using a surfactant is prepared in powder form, additional processes that are to be formed as a molded product are required to be applied to an industrial process. However, there is a problem that the pore characteristic of alumina is destroyed in a molding process comprising alumina made of powder as a molded body. In addition, the conventional production method using a surfactant can complicate the manufacturing process by adding and removing the surfactant separately, and it is difficult to reduce the manufacturing cost.

Therefore, it is necessary to develop a process for producing an alumina compact which can maintain the pore characteristics without using a surfactant.

A problem to be solved by the present invention is to provide a method for producing an alumina compact which can maintain the pore characteristics without using a surfactant.

According to an aspect of the present invention, there is provided a method for preparing a boehmite gel, which comprises: forming a boehmite gel by stirring a mixed solution of boehmite, silica, a peptizer, and a solvent as alumina precursors; Aging the boehmite gel in an atmosphere for 12 hours to 24 hours, and firing the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores therein The present invention provides a method for producing an alumina compact.

The volume of the mesopores of the alumina compact can be controlled by adjusting the content of the silica.

The peptizing agent may include at least one selected from nitric acid, hydrochloric acid, and acetic acid, and may be mixed in the mixed solution in an amount of 0.05M to 0.1M.

The solvent may be at least one selected from water, dimethylformamide, and ethanol.

The solvent may be mixed at a ratio of 0.5 to 2 mol per 1 mol of the boehmite.

The saturated vapor pressure temperature of the solvent may be in the range of 100 占 폚 to 150 占 폚.

Alumina formed body having the mesopore is, it may be one having a mesopore volume, and 330 m ² / g to 510m ² / g specific surface area of 0.5 cm ³ / g to 1.1 cm ³ / g.

The method may further include molding the aged boehmite gel into a spherical or polygonal shape before the step of firing the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores .

The pore characteristics of the alumina compact having the mesopores can be maintained without using the surfactant through the method of producing the alumina compact of the present invention.

Accordingly, since a step for drying the surfactant is not required, the manufacturing process can be simplified and the manufacturing cost can be reduced.

In addition, the characteristics of the mesopores of the alumina compact having mesopores can be easily controlled by the content of silica and the aging process.

Fig. 1 (a) is a view illustrating a process for producing an alumina compact to which a conventional surfactant is added, and Fig. 1 (b) is a process for producing the alumina compact according to the present invention.
2 is a chart showing XRD measurements of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.
3A and 3B are SEM images of the alumina compact produced in Comparative Example 2 and the alumina compact manufactured in Example 1, respectively.
4 is a graph showing the results of nitrogen adsorption experiments of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.
5 is a graph showing the volume of the mesopores according to the diameters of the mesopores of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.
6 is a chart showing low angle X-ray diffraction lines according to diameters of the mesopores of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

One aspect of the present invention can provide a method of manufacturing an alumina compact.

The method for producing an alumina compact includes the steps of 1) stirring a mixed solution obtained by mixing boehmite, silica, a peptizer and a solvent, which are alumina precursors, to form a boehmite gel, 2) controlling the saturated vapor pressure of the solvent Aging the boehmite gel in an atmosphere for from 12 hours to 24 hours, and 3) firing the aged boehmite gel at a temperature of from 500 DEG C to 600 DEG C to form an alumina compact having mesopores have.

Step 1) of the method for producing an alumina compact of the present invention is a step of forming a boehmite gel by stirring a mixed solution containing boehmite, silica, a peptizer, and a solvent, which are alumina precursors.

The boehmite mixed in the mixed solution is a white alumina hydrate having the formula of AlO (OH), which can be used as an alumina precursor in the present invention. The boehmite powder may be in the form of powder, and the boehmite powder may have an average particle size of 1 탆 to 100 탆, but the present invention is not limited thereto. The boehmite may be one prepared by a known production method. For example, the boehmite may be one produced by hydrolysis from an aluminum alkoxide. The boehmite may be a commercially available product.

The silica (SiO ₂ ) mixed in the mixed solution is an inorganic oxide and may function as a skeleton of a mesoporous structure of an alumina compact to be described later. That is, the silica can improve the physical strength of the alumina compact formed through the mixed solution, and can finely control the pore characteristics of the alumina compact having the medium pores. Accordingly, the volume of the mesopores of the alumina compact can be controlled by adjusting the content of the silica.

The silica may be mixed at a ratio of 0.1 mole to 1 mole based on 1 mole of the boehmite, but is not limited thereto. If the silica is added to the mixed solution in excess of the mixing ratio, the pore characteristics of the alumina compact having the mesopores may be affected, so that the mixing can be performed within the mixing ratio.

Further, in the firing step to be described later, the silica may function as a promoter or a stabilizer in which the mesopores in the boehmite gel can maintain stability even at a high temperature.

According to the embodiment, titania (TiO ₂ ), which is an inorganic oxide, may be further added together with the silica to form a mixed solution.

The peptizing agent to be mixed with the mixed solution may be a function of appropriately dispersing the boehmite and the silica in the solvent constituting the mixed solution. Specifically, when the mixed solution containing boehmite as the alumina precursor is completely hydrolyzed in the solvent, precipitation of alumina hydrate (Al-OH) occurs, and the precipitant is decomposed by adding the peptizer to form a stable colloidal form Can be formed. The peptizing agent may be at least one selected from nitric acid, hydrochloric acid, and acetic acid. The pH of the mixed solution can be adjusted by adding the peptizing agent and the controlled pH of the mixed solution may affect repulsion between the boehmite particles in the mixed solution, The particle size and the particle distribution of the particles may vary. Thus, the peptizing agent may be mixed with the mixed solution in an amount of 0.05M to 0.1M per 1 mol of the boehmite .

The solvent to be mixed into the mixed solution may include at least one selected from water, dimethyl formamide, and ethanol. The solvent may be mixed at a ratio of 0.5 to 2 mol per 1 mol of the boehmite. When the mixing ratio of the solvent to the boehmite is less than 0.5 mol, it is difficult to sufficiently dissolve the boehmite in the solvent. When the mixing ratio of the solvent is more than 2 mol, the boehmite and the solvent The reaction efficiency of the mixed solution may be lowered. By mixing the boehmite and the solvent at the mixing ratios as described above, the hydrolysis rate of the boehmite powder particles can be optimized.

The boehmite gel may be formed by stirring the mixed solution in which the boehmite, silica, peptizing agent, and solvent are mixed. The stirring may be performed at room temperature. Accordingly, the boehmite powder particles and the silica particles can be uniformly dispersed in the solvent together with the peptizing agent, and the hydrolysis reaction of the boehmite powder particles can be smoothly performed. The boehmite and the solvent may be stirred and mixed within a time range of 60 minutes to 120 minutes. This may be a time required for the temperature of the mixed solution to rise instantaneously due to the reaction heat generated by the hydrolysis reaction of the boehmite and the solvent so as to reach the equilibrium temperature again.

The boehmite powder particles may be bound to each other through the hydrolysis reaction so that the mixed solution gradually forms in the form of a boehmite gel. That is, the gelation of the mixed solution containing the boehmite can form a boehmite gel composed of more uniform and finely agglomerated boehmite particles than the powdered boehmite particles. Accordingly, the boehmite particles constituting the boehmite gel may have a mesh structure.

Step 2) may be such that the boehmite gel is aged for 12 to 24 hours under an atmosphere controlled to the saturation vapor pressure temperature of the solvent. The binding strength between the boehmite gel particles in the boehmite gel can be increased by aging the boehmite gel under an atmosphere controlled by the saturation vapor pressure temperature of the solvent. This affects the crystallinity of the boehmite gel, and can affect the specific surface area of the alumina compact when the alumina compact is manufactured using the same. Specifically, as the crystallinity of the boehmite gel increases, the number of crystal nuclei increases and the size of crystals formed decreases. Accordingly, the specific surface area of the alumina compact formed using the boehmite gel may be increased.

As described above, since the crystallinity of the boehmite gel may vary depending on the aging time of the boehmite gel, the aging time of the boehmite gel may be an important factor. Accordingly, by aging the boehmite gel for 12 hours to 24 hours, the present invention can improve the crystallinity of the boehmite gel and produce an alumina compact having a high specific surface area. This may be in combination with controlling the volume of the mesopores with the amount of silica mentioned above. As described above, the present invention can have an effect of controlling the pore characteristics of an alumina compact by forming a gelatinized boehmite gel by dissolving boehmite, which is an alumina precursor, in a solvent, without adding a surfactant to produce an alumina compact .

When the boehmite gel is aged for less than 12 hours, it may not be fully aged. Therefore, it may be difficult to obtain an alumina compact which can improve the volume and pore characteristics of a desired medium pore size. When the boehmite gel is aged for a period of more than 24 hours, a part of the outer surface of the boehmite gel is dried to form the boehmite gel, It may not be easy. Thus, the boehmite gel can be aged in an optimal state within the aging time range.

The atmosphere controlled by the saturation vapor pressure temperature of the solvent may be set to a different temperature depending on the type of the solvent. When water is used as the solvent, the saturated vapor pressure temperature of the solvent can be controlled to about 100 ° C. When dimethylformamide is used as the solvent, the saturation vapor pressure temperature of the solvent can be controlled to about 150 ° C. When ethanol is used as the solvent, the saturated vapor pressure temperature of the solvent can be controlled to 80 to 100 캜. Thus, the saturated vapor pressure of the solvent may be in the range of 100 ° C to 150 ° C.

Further comprising the step of shaping the aged boehmite gel into a spherical or polygonal shape prior to the step of baking the aged boehmite gel described later at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores . That is, after the aged boehmite gel is cooled to room temperature, it can be immediately molded into the shape of a desired shape without drying process. This is because, when the aged boehmite gel is dried, the aged boehmite gel is shrunk, and as the shrinkage progresses, the middle pores of the aged boehmite gel can be clogged, It may be difficult to maintain the pore characteristics of the boehmite gel. The aged boehmite gel may be formed into a desired shape of a molded body by using a general alumina molding apparatus. The aged boehmite gel may be injected into the device in various forms such as spherical or polygonal to shape the desired shape.

Step 3) is a step of firing the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores. As described above, when the aged boehmite gel is molded, the molded boehmite gel may be baked.

The solvent contained in the boehmite gel may be removed during the calcination of the aged boehmite gel at a temperature of 500 ° C to 600 ° C, and the boehmite particles constituting the boehmite gel may be phase-transformed to alumina . If the temperature at which the aged boehmite gel is baked is less than 500 ° C, the phase transition to alumina may be insufficient and the strength of the alumina compact may be weakened. If the temperature at which the aged boehmite gel is baked exceeds 600 ° C , It may affect the pore characteristics of the alumina compact having mesopores, and it may be desirable to maintain the calcination temperature range. The aged boehmite gel may be baked in air or may be carried out using a general baking apparatus. The calcination time may be 10 to 15 hours, but is not limited thereto.

The pore diameter of the alumina compact having the mesopores may be in the range of 5 nm to 10 nm, but is not particularly limited.

The alumina compact having the mesopores may have a medium pore volume of 0.5 cm ³ / g to 1.1 cm ³ / g and a specific surface area of 330 m ² / g to 510 m ² / g. The specific surface area and the size of the mesopores of the alumina compact having the mesopores can be controlled according to the content of the silica contained in the mixed solution and the composition of the aging step in the step 2). Accordingly, the present invention can have the effect of maintaining the specific surface area and the size of the mesopores of the alumina compact, as described above, through the production method of aging and baking the boehmite gel without drying process.

Fig. 1 (a) is a view illustrating a process for producing an alumina compact to which a conventional surfactant is added, and Fig. 1 (b) is a process for producing the alumina compact according to the present invention.

Referring to FIGS. 1 (a) and 1 (b), it is confirmed that the prior art requires a separate filtering process and a drying process to remove the surfactant by mixing surfactant, which complicates the manufacturing process. Alternatively, the present invention can simplify the manufacturing process by dissolving boehmite in a solvent to gelify it, aging it at a saturated vapor pressure temperature, and firing it without a drying process, thereby reducing manufacturing costs. In addition, as described above, the pore characteristics of the mesopores can be maintained and controlled in the manufacturing process so that the alumina compact can be used as a carrier.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding. It should be noted, however, that the following examples are for the purpose of helping to understand the present invention, and the present invention is not limited by the following examples.

<Examples>

Example 1

27.4 g of boehmite (Disperal P ₂ ), 4.0 g of tetraethylorthosilicate (TEOS) as silica, 70 ml of dimethylformamide as a solvent and 1 ml of nitric acid (HNO ₃ ) as a peptizing agent were mixed and stirred for about 1 hour To prepare a boehmite gel. The boehmite gel was aged in an oven at 100 ° C. for about 12 hours, cooled to room temperature to form a spherical shape, and then calcined at 550 ° C. for about 11 hours to obtain an alumina compact.

Example 2

In the case of Example 2, an alumina compact was produced through the same process conditions except that 4.0 g of tetraethylorthosilicate (TEOS) was further added as compared with Example 1.

Example 3

In the case of Example 3, an alumina compact was produced through the same process conditions except that 8.0 g of tetraethylorthosilicate (TEOS) was further added as compared with Example 1 and aging was performed at a temperature of 120 캜 at the aging time .

Comparative Example 1

In the case of Comparative Example 1, only 1.04 g of tetraethyl ortho silicate (TEOS) was added, and the aged boehmite gel was completely dried at 60 ° C and then molded and fired. To prepare an alumina compact.

Comparative Example 2

In the case of Comparative Example 2, an alumina compact was produced through the same process conditions except that the aged boehmite gel was completely dried at 60 ° C and then molded and fired as compared with Example 1.

2 is a chart showing XRD measurements of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.

2, it can be seen that the 2? Peaks of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 appear at about 37, 46 and 67 degrees. This is in agreement with the peaks appearing on general alumina crystals. From this, it can be seen that the alumina formed body produced by dissolving boehmite in a solvent according to the present invention is well transformed into alumina phase through aging and firing, .

3A and 3B are SEM images of the alumina compact produced in Comparative Example 2 and the alumina compact manufactured in Example 1, respectively.

3A and 3B, it can be seen that a plurality of pores are formed through the SEM image of the alumina compact produced in Comparative Example 2 of FIG. 3A. The SEM image of the alumina compact produced in Example 1 of FIG. 3b shows that the pores having a medium size enough to be visually distinguishable from the comparative example 2 are uniformly distributed. Thus, it can be seen that the pore characteristics of the alumina compact having a medium pore structure are well maintained even after the aged boehmite gel is fired by molding and firing the powdered boehmite gel without drying the present invention. In addition, it can be confirmed that the alumina compact produced in Example 1 has a higher degree of crystallinity than the alumina compact produced in Comparative Example 1. This shows that the crystallinity of the alumina compact is further improved by aging the boehmite gel.

4 is a graph showing the results of nitrogen adsorption experiments of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.

Referring to FIG. 4, the related results are shown in Table 1 below.

division Specific surface area
(BET method)
(m ² / g) Specific surface area
(Langmuir method)
(m ² / g) Pore volume
(single point)
(cm &lt; ³ &gt; / g) Pore volume
(BJH adsorption)
(cm &lt; ³ &gt; / g) Pore volume
(BJH desorption)
(cm &lt; ³ &gt; / g) Comparative Example 1 284 394 0.48 0.49 0.49 Comparative Example 2 334 464 0.56 0.58 0.58 Example 1 333 458 0.81 0.82 0.82 Example 2 344 475 0.87 0.90 0.90 Example 3 374 516 1.14 1.01 1.13

In the table of FIG. 4, it can be seen that the adsorption amount of the alumina compact of each of the examples and the comparative examples increases with the pressure. In particular, it was confirmed that the adsorption amounts of Examples 1 to 3, which were prepared by aging after gelation through a solvent, were higher than those of Comparative Example 1 and Comparative Example 2 in which the drying process was performed during the production of the alumina compact have. The large nitrogen adsorption amount means that the specific surface area in the alumina compacted body is large. As shown in Table 1, the alumina compacted body produced according to the production method of the present invention has a larger specific surface area than the alumina compacted body of the comparative examples .

5 is a graph showing the volume of the mesopores according to the diameters of the mesopores of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.

5, the pore diameters of the alumina compacts of Comparative Example 1 and Comparative Example 2 produced by performing the drying process are shown in Fig. 5. The pore diameters of the alumina compacts of Examples 1 to 3, It can be confirmed that it is smaller than the diameter. Also, it can be seen that the embodiments of the present invention are also larger in the volume of the medium pores. This may mean that the diameter and volume of the mesopores are improved through the process of aging the alumina compact of the present invention after the gelation without drying process as described above with reference to FIG.

In addition, it can be confirmed that the mesopores of Examples 1 to 3 of the present invention have similar diameters but the pore volume is slightly different. Specifically, it can be seen that the alumina compacts of Examples 2 and 3 produced by adding more silica to Example 1 exhibit a larger pore volume. It can be seen that the volume of the mesopores of the alumina compact can be controlled by controlling the content of silica.

6 is a chart showing low angle X-ray diffraction lines according to diameters of the mesopores of the alumina compacts of Examples 1 to 3, Comparative Examples 1 and 2 of the present invention.

Referring to FIG. 6, it can be seen that the intensity of the low angle X-ray diffraction line of the examples of the present invention, which is shown as the formation of the mesopores, is higher than the comparative examples. That is, it can be seen that the intensity of the peak indicating the existence of the mesoporous pores increases with the alumina compact formed without the drying process and the alumina compact with the higher silica content. Accordingly, it can be confirmed that the method of manufacturing the alumina compact according to the present invention can control the amount of the mesopores according to the content of silica added to the drying process and the mixed solution.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

Claims (8)

A boehmite gel is formed by stirring a mixed solution of boehmite, silica, a peptizer, and a solvent, which is an alumina precursor;
Aging the boehmite gel for 12 hours to 24 hours under an atmosphere controlled to a saturation vapor pressure temperature of the solvent; And
Calcining the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores,
Wherein the volume of the mesopores of the alumina compact is controlled by adjusting the content of the silica. delete The method according to claim 1,
Wherein the peptizing agent comprises at least one selected from the group consisting of nitric acid, hydrochloric acid, and acetic acid and is mixed in the mixed solution in an amount of 0.05M to 0.1M. The method according to claim 1,
Wherein the solvent comprises at least one selected from the group consisting of water, dimethylformamide, and ethanol. The method according to claim 1,
Wherein the solvent is mixed at a ratio of 0.5 to 2 mol based on 1 mol of the boehmite. The method according to claim 1,
The saturation vapor pressure temperature of the solvent is,
Wherein the temperature is in the range of 100 占 폚 to 150 占 폚. The method according to claim 1,
The alumina compact having the above-mentioned mesopores is characterized in that,
0.5 cm ³ / g to method for producing an alumina formed body, characterized in that having a mesopore volume, and 330 m ² / g to 510m ² / g specific surface area of 1.1 cm ³ / g. The method according to claim 1,
Prior to the step of baking the aged boehmite gel at a temperature of 500 ° C to 600 ° C to form an alumina compact having mesopores,
Further comprising the step of shaping the aged boehmite gel into a spherical or polygonal shape.

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