KR100408006B1 - Method for preparing mesoporous crystalline molecular sieve - Google Patents

Abstract

The present invention relates to a method for producing a crystalline molecular sieve having a mesoporous structure, and more particularly to an improved method for producing a mesoporous crystalline molecular sieve having excellent hydrothermal stability. Method for producing a crystalline molecular sieve according to the present invention is to produce a mesoporous crystalline molecular sieve, while having a variety of types of silica and excellent thermal properties and a large specific surface area without the use of quaternary ammonium hydroxide A pore thickness can be improved and hydrothermal stability can be improved by having a washing | cleaning step in a step or using a nonionic surfactant.

Description

Method for preparing crystalline molecular sieve having mesoporous structure {Method for preparing mesoporous crystalline molecular sieve}

The present invention relates to a method for producing a crystalline molecular sieve having a mesoporous structure, and more particularly, to an improved method for producing a mesoporous crystalline molecular sieve having a large pore thickness and excellent hydrothermal stability.

Porous inorganic materials have been useful in industries related to catalyst or material separation, which have a relatively large specific surface area due to micropores and numerous catalysts where molecules can adsorb and stay. Provide an active seat.

Porous materials that are used today can be classified as modified layered compounds, which are supported by inserting fragments, such as metal oxides, between amorphous carriers, crystalline molecular sieves, and layered materials in terms of microstructure. These materials differ in detail in their microstructure, resulting in unique selectivity of the material in adsorption or catalytic behavior. In addition, there is a detailed difference in the appearance of the specific surface area, pore size, X-ray diffraction pattern and electron microscope.

In general, the amorphous silica and the amorphous alumina carrier do not have uniform pores because the gap formed between the particles and the particles form pores, and mainly has a wide pore distribution in the region of 20 ~ 200Å. On the other hand, materials with regular crystallinity, such as zeolites, exhibit very narrow pore distributions. Since most zeolites have a limited size of pores of 3 to 10 microns, new types of mesoporous molecular sieves have begun to be synthesized in an effort to expand the pore size. Mobil Co., Ltd. has successfully synthesized a new mesoporous material that can control pore size uniformly within the range of 20 ~ 100Å and named it MCM-41. Physical properties and structural properties have been disclosed in various documents such as U.S. Patent Nos. 5,108,725, 5,102,684, 5,098,684, 5,057,296, 5,102,643, 5,672,556, and Korean Patent No. 256914.

For example, US Pat. No. 5,102,643 uses a quaternary ammonium hydroxide such as tetramethylammoniumsilicate solution in addition to surfactants to prepare porous materials for 2-7 days while maintaining 100-150 ° C. in a high pressure reactor. Although the method is described, the method not only reacts at a high pressure, but also has a disadvantage of using many organic materials. In addition, US Pat. No. 5,672,556 prepares a mature non-ionic silicon precursor and prepares a homogeneous solution of a non-ionic amine template comprising a hydrolytic agent selected from water, an organic-co-solvent and mixtures thereof. Although a method of preparing a synthetic crystalline silicate is described, which comprises mixing and reacting these and separating a template having a pore size of 20 μs from the silicate composition, it has a reaction mechanism completely different from the present invention.

The method of US Pat. No. 6,096,287 (corresponding to Korean Patent No. 158759) invented by the present inventors to solve the disadvantages of the prior art is economically able to use all kinds of silica in a short time and using a hydrogen fluoride solution The present invention relates to a method for preparing a mesoporous molecular sieve using a silica raw material within 6 hours in a temperature range of 25 to 80 ° C., and includes various types of silica and excellent thermal properties without using quaternary ammonium hydroxide. It was possible to prepare mesoporous molecular sieves having a specific surface area.

However, the mesoporous molecular sieve prepared by other prior arts, including the US Patent No. 6,096,287, still contains a lot of silanol groups on the surface, and the pore thickness is relatively thin, such as 10 to 20Å, which is vulnerable to water vapor or water. It had a problem with poor hydrothermal stability.

Accordingly, the present inventors have developed a method for preparing a crystalline molecular sieve having an improved mesoporous structure by solving and supplementing the problems of the prior arts.

Accordingly, an object of the present invention is to provide a variety of types of silica that can be used and excellent thermal properties without having to use quaternary ammonium hydroxide, while having a large specific surface area, can improve the pore thickness and have better hydrothermal stability, It is to provide a method for producing a crystalline molecular sieve having a mesoporous structure.

Method for producing a crystalline molecular sieve according to the present invention for achieving the above object, a) silica alone or a mixture with a metal salt or metal alkoxide (Si / metal molar ratio) with respect to 100 parts by weight of hydrogen fluoride solution of 5 to 50% concentration (At least 10) dissolving 2 to 20 parts by weight to prepare a first solution; b) preparing a second solution by dissolving 2 to 12 parts by weight of the cationic surfactant with respect to 100 parts by weight of distilled water; c) 20 to 30 parts by weight of concentrated ammonia water (based on 100 parts by weight of hydrogen fluoride solution) by adding the first solution to the second solution in a weight ratio of 1 to 2: 1 (second solution: first solution), and then mixing the mixture uniformly. ), Aged for 10 to 18 hours at 25 to 80 ℃, filtered and dried to prepare a powder; And d) adding the powder to 200 to 300 parts by weight of ethanol acid solution (based on 100 parts by weight of hydrogen fluoride solution) and calcining at 300 to 600 ° C. for 2 to 4 hours.

Another method for producing the crystalline molecular sieve according to the present invention for achieving the above object is a) a silica alone or a mixture with a metal salt or a metal alkoxide (Si / Preparing a first solution by dissolving 2 to 20 parts by weight of a metal molar ratio of 10 or more); b) preparing 2nd solution by dissolving 2-12 weight part of nonionic surfactants with respect to 100 weight part of distilled water; And c) 20 to 30 parts by weight of concentrated ammonia water (100 parts by weight of hydrogen fluoride solution) by adding the first solution to the second solution in a weight ratio of 1 to 2: 1 (second solution: first solution) and uniformly mixing the mixture. Step), and aged at 25 to 80 ° C. for 10 to 18 hours, followed by filtration and drying. D) The powder is added to 200 to 300 parts by weight of ethanol acid solution (based on 100 parts by weight of hydrogen fluoride solution). And calcining at 300 to 600 ° C. for 2 to 4 hours.

1 is a graph showing the X-ray diffraction pattern of the final product prepared according to the method of the present invention,

2 is a graph showing the X-ray diffraction pattern of the final product prepared according to another method of the present invention.

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

As described above, silica alone or a mixture of a metal salt and a metal alkoxide is dissolved at 2 to 10 parts by weight based on 100 parts by weight of a hydrogen fluoride solution at a concentration of 5 to 50%. If the concentration of the hydrogen fluoride solution is less than 5%, there is a problem in that the silica cannot be dissolved due to low solubility of silica, and if it exceeds 50%, the hydrogen fluoride solution is unnecessarily wasted and ammonia is consumed in the precipitation process. There is a problem. Thus, the use of the hydrogen fluoride solution can dissolve a large amount of silica in a very short time at room temperature and atmospheric pressure, and there is an advantage that does not depend on the type of silica.

Since a hydrogen fluoride solution is used as a silica solubility in this invention, all kinds of silica can be used. In addition, as the metal salt, one metal salt selected from the group consisting of Al (NO ₃ ) ₃ , Al (SO ₄ ) ₃ , AlCl ₃ and NaAlO ₂ may be used, and the metal alkoxide may be titanium (IV) alkoxide, aluminum alkoxide and One metal alkoxide selected from the group consisting of silicon alkoxides can be used, preferably titanium (IV) isopropoxide.

The second solution is prepared by dissolving 2 to 12 parts by weight of a cationic surfactant or a nonionic surfactant with respect to 100 parts by weight of distilled water.

In this case, the cationic surfactant may include alkyltrimethylammonium having a hydrocarbon chain having 10 or more carbon atoms, and representative examples thereof are cetyltrimethylammonium bromide or cetyltrimethyl ammonium chloride. In addition, the nonionic surfactant is used ethylene oxide (EO) 5 or more, representative of which is octylphenoxypolyethylene alcohol (4-octyl-phenoxypolyethylene alcohol).

Both the cationic surfactant and the nonionic surfactant are preferably added in an amount of 2 to 12 parts by weight with respect to 100 parts by weight of distilled water. When the amount is less than 2 parts by weight, there is a problem in that a desired micelle template is difficult to be formed, and more than 12 parts by weight. In this case, the micelle template may be out of the range of formation, and problems such as economic loss and environmental pollution due to large spills of residual surfactant may occur.

The role of the cationic surfactant used in the present invention is to induce silica and silica alumina crystals on the charged micelle colloid surface formed by dissolving the surfactant molecules in water. By removing the hydrophilic functional group, the pore thickness can be increased and hydrothermal stability can be improved. However, the role of the nonionic surfactant is to induce silica and silica alumina crystals by hydrogen bonding of hydrated silanol and ethylene oxide chains, and the crystals can be bonded by intense heating and intercalate with oxygen. In addition, it is possible to form a crosslink in the molecular dimension between Al and Si. The material produced in this way has a uniform pore size, a large specific surface area of 500 to 1100 m ² / g, and the framework consists of SiO ₂ and SiO ₂ / Al ₂ O ₃ .

At this time, the nonionic surfactant differs from the cationic surfactant in the formation mechanism of the crystalline molecular sieve. In the cationic reaction mechanism, crystal growth stops quickly due to the interaction between ions, and crystal growth stops immediately. In contrast, nonionic reaction mechanism takes a relatively long time due to the intermolecular interaction. The thickness of the pore wall is increased. Therefore, even without a separate washing step, the pore thickness is larger than that in the case of using a cationic surfactant, and hydrothermal stability can be improved. In addition, in the case of using a nonionic surfactant, by including the washing step of the ethanol acid solution to be described later, the hydrothermal stability can be further improved by removing the hydrophilic functional groups present on the surface.

In the case of conventional molecular sieves with weak hydrothermal stability, when molecular sieves are added to boiling water at 100 ° C., hydroxyl groups or silanol groups flow out, and the pore thickness becomes thin and the reflux time to boiling water becomes long (in boiling water). Poor destruction of the pores results in a long period of time, which is an undesirable problem for the molecular sieve mainly used as a catalyst and an adsorbent. Therefore, the excellent hydrothermal stability herein means that the pore thickness and size do not change even when the reflux time is increased in boiling water.

The first solution was added to the second solution prepared as described above in a weight ratio of 1 to 2: 1 (second solution: first solution), mixed uniformly, and then 20 to 30 parts by weight of concentrated ammonia water (100 parts by weight of hydrogen fluoride solution). Standard) is added, vigorously stirred and uniformly mixed, then aged at 25 to 80 ° C. for 10 to 18 hours, followed by filtration and drying to prepare a powder. At this time, if the aging temperature is out of the range it is not preferable because there is a complicated problem in device design and operation management because it has to react in a high pressure reactor. In addition, the concentration of the concentrated ammonia water is preferably 25 to 30%.

The prepared crystal powder was added to 200 to 300 parts by weight of an ethanol acid solution (100 parts by weight of hydrogen fluoride solution) at a concentration of 1 to 2 N to remove the surfactant and hydrophilic functional groups, and then calcined at 300 to 600 ° C. for 2 to 4 hours. Thus, a crystalline molecular sieve having a mesoporous structure according to the present invention can be obtained. The ethanol acid solution is prepared by dissolving an acid such as HCl, H ₂ SO ₄ , or HNO ₃ in ethanol. By removing some of the surfactant used in the reaction by going through the washing step of adding the powder to the ethanol acid solution, the temperature can be lowered and the time can be reduced in the next calcination step. It is possible to prevent the pore thickness from thinning, thereby making it possible to prepare a material resistant to heat, water vapor, or impact, and to remove hydrophilic functional groups present on the surface due to the ethanol acid solution, thereby improving hydrothermal stability. When the concentration of the ethanol acid solution is less than 1N, there is a problem that it is difficult to completely remove the hydrophilic functional group from the surface, when the concentration of more than 2N there is a problem that the acid is too strong to melt the alumina. In addition, if the added amount is less than 200 parts by weight, the hydrophilic functional groups are not completely cleaned, and there is a problem that remains on the surface. have.

Thus the prepared mesoporous molecular sieve is that only the SiO _2, having a structure in which a portion of Al or Ti occupying the Si position, the molar ratio in this case Si / Al or Si / Ti was more than 10.

X-ray diffraction analysis of the sample prepared as described above was carried out using the X-ray diffractometer of Rigaku, Japan, and the analysis conditions were 15mA, 35kV using a Cu Kα target and Ni-filter. The relative strength is measured with the rotation angle (2θ) in the range of 1.5 to 20 ° as the count range of 5000 cps. The specific surface area is obtained by determining the nitrogen adsorption isotherm at the liquid nitrogen temperature (77K) and then analyzing the data in the range of 5 to 100 torr by BET (Brunauer Emmett Teller) formula to calculate the specific surface area. As a adsorption apparatus, Micrometries ASAP 2100 was used, and all samples were degassed at 300 ° C. for 4 hours and then subjected to N ₂ adsorption experiment. The pore size distribution is calculated by Barrett Joyner Halenda (BJH).

As a result of X-ray diffraction analysis and measurement of specific surface area, d-spacing was 35-50Å, mesoporous molecular sieve, specific surface area was 800 ~ 1100 m ² / g, and pore size was distributed in 35-40∼. The pore thickness is 20 to 30Å, and the pore thickness and size do not change even when the reflux time is increased for boiling water, and the hydrothermal stability is greatly improved.

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 thereto.

Example 1

100 g of a 24% hydrogen fluoride solution was taken in a polyethylene beaker, and 3 g of silica (zeosil 155, Rhodia Kofran Co.) was completely dissolved to prepare a first solution, which was a silicon fluoride solution. 100 g of distilled water was taken in a separate beaker to dissolve 4 g of cetyltrimethyl ammonium bromide to prepare a second solution. The first solution is added to the second solution in a 1: 1 weight ratio and stirred. To this was added 25 g of 28% concentrated ammonia water (Jin Chemical) and stirred vigorously at 60 ° C for 10 minutes. After aging for 16 hours at 70 ℃ in a drier and filtered to recover the precipitate to prepare a powder. The powder was washed with 300 g of 1.2 N ethanol HCl acid solution, and then calcined at 600 ° C. for 3 hours. The X-ray diffraction pattern of the calcined sample is shown in FIG. 1 attached, where a relatively strong signal with d-spacing of 43.4 kHz shows well the characteristics of MCM-41. The specific surface area obtained from the BET equation was 950m ² / g and the pore size was concentrated at 35Å. In addition, 1 g of the sample was placed in 1000 g of distilled water and refluxed at 100 ° C. for 12 and 24 hours, and then filtered, washed, and dried for the hydrothermal stability test of the sample, and the analysis results thereof are shown in Table 1 below.

Example 2

Except for using a mixture of 3g of silica and 0.279g of metal salt Al (NO ₃ ) ₃ .9H ₂ 0 instead of silica was carried out in the same manner as in Example 1, wherein the Si / Al ratio was 50. The X-ray diffraction pattern of the sample was similar to that of FIG. 1, where a d-spacing of 45.9 kPa was obtained, the specific surface area was 850 m ² / g, and the pore size was concentrated at 38 kPa.

Example 3

The same procedure as in Example 1 was carried out except that a mixture of 3 g of silica and 0.284 g of metal alkoxide titanium (IV) isopropoxide was used instead of silica, and a Si / Al ratio was 50. The diffraction pattern of the X-ray of the sample was similar to that of FIG. 1, where a d-spacing of 43.9 kPa was shown, the specific surface area was 900 m ² / g, and the pore size was concentrated at 37 kPa.

Example 4

Example 1, except that 7 g of 4-octylphenoxypolyethylene alcohol 4- (C ₈ H ₁₇ ) (C ₆ H ₄ O- (CH ₂ CH ₂ O) ₁₂ CH ₂ CH ₂ OH) was used as the surfactant. In this case, the X-ray diffraction pattern is the same as that of FIG. 2, and the hexagonal mesoporous structure has a d-spacing of 46 μs. The specific surface area was 1020m ² / g and the pore size was concentrated at 35Å. In addition, 1 g of the sample was placed in 1000 g of distilled water and refluxed at 100 ° C. for 12 and 24 hours, followed by filtration, washing, and drying, and the results of the analysis are shown in Table 1 below.

Example 5

100 g of a 24% hydrogen fluoride solution was taken in a polyethylene beaker, and 3 g of silica (zeosil 155, Rhodia Kofran Co.) was completely dissolved to prepare a first solution, which was a silicon fluoride solution. Take 100 g of distilled water in a separate beaker and dissolve 7 g of 4-octylphenoxypolyethylene alcohol 4- (C ₈ H ₁₇ ) (C ₆ H ₄ O- (CH ₂ CH ₂ O) ₁₂ CH ₂ CH ₂ OH). Was prepared. The first solution is added to the second solution in a 1: 1 weight ratio and stirred. To this was added 25 g of 28% concentrated ammonia water (Jin Chemical) and stirred vigorously at 60 ° C for 10 minutes. After aging for 16 hours at 70 ℃ in a drier and filtered to recover the precipitate to prepare a powder. The X-ray diffraction pattern of the prepared sample shows the same aspect as that of FIG. 2, where a relatively strong signal with d-spacing of 43.4 kHz shows well the characteristics of MCM-41. The specific surface area obtained from the BET equation was 1015 m ² / g and the pore size was concentrated at 35 Å. In addition, 1 g of the sample was placed in 1000 g of distilled water and refluxed at 100 ° C. for 12 and 24 hours, and then filtered, washed, and dried, and the results thereof are shown in Table 1 below.

Comparative Example 1

100 g of a 24% hydrogen fluoride solution was taken in a polyethylene beaker and 3 g of silica (zeosil 155, Rhodia Kofran Co.) was completely dissolved to prepare a silicon fluoride solution. 100 g of distilled water was taken in a separate beaker to dissolve 4 g of cetyltrimethylammonium bromide, and then stirred in a hydrogen fluoride solution. 25 g of 28% ammonia water was added thereto, and the mixture was stirred vigorously at 60 ° C for 10 minutes. After aging for 16 hours at 70 ℃ in a dryer, the precipitate was recovered by filtration and calcined at 600 ℃ for 4 hours. In order to conduct a hydrothermal stability test of the synthesized sample, 1 g of the sample was placed in 1000 g distilled water and refluxed at 100 ° C. for 12 and 24 hours, followed by filtration, washing, and drying. The analysis results thereof are shown in Table 1 below.

Reflux Time Specific surface area Pore indicators in concentrated distribution ^* Pore thickness Remarks Example 1 12 957 35 25.2 24 960 34 25.2 Example 4 12 1020 35 28.8 24 1030 36 28.8 Example 5 12 1015 35 29.7 24 1025 35 29.7 Comparative Example 1 12 1001 33 19.5 24 750 24.3 - Pore thickness cannot be calculated due to pore destruction

* Pore thickness calculation method

Where

T = pore thickness,

d-space value at d ₁₀₀ = 100,

d ₁ = pore diameter in the concentrated distribution.

As can be seen in Table 1, the embodiment according to the present invention has a larger pore thickness than the comparative example 1 of the conventional method, the pore is destroyed as the reflex time for boiling water for 24 hours, the specific surface area And compared to the comparative example showing an unstable hydrothermal stability due to a decrease in pore diameter, the hydrothermal stability was excellent, such that the thickness did not change even after the reflex time elapsed.

As can be seen from the above examples and comparative examples, the mesoporous molecular sieve prepared according to the present invention has various kinds of silica that can be used and excellent thermal properties without using quaternary ammonium hydroxide, and a large specific surface area. In addition, the pore thickness can be improved and the hydrothermal stability is better.

Claims (11)

a) preparing a first solution by dissolving 2 to 20 parts by weight of silica alone or a mixture of a metal salt or a metal alkoxide (Si / metal molar ratio of 10 or more) with respect to 100 parts by weight of a hydrogen fluoride solution at a concentration of 5 to 50%; b) preparing a second solution by dissolving 2 to 12 parts by weight of the cationic surfactant with respect to 100 parts by weight of distilled water; c) 20 to 30 parts by weight of concentrated ammonia water (based on 100 parts by weight of hydrogen fluoride solution) by adding the first solution to the second solution in a weight ratio of 1 to 2: 1 (second solution: first solution), and then mixing the mixture uniformly. ), Aged for 10 to 18 hours at 25 to 80 ℃, filtered and dried to prepare a powder; And d) adding the powder to 200 to 300 parts by weight of an ethanol acid solution (based on 100 parts by weight of hydrogen fluoride solution) and calcining at 300 to 600 ° C. for 2 to 4 hours. Method for producing crystalline molecular sieve. The crystalline molecular sieve having a mesoporous structure according to claim 1, wherein the metal salt is one selected from the group consisting of Al (NO ₃ ) ₃ , Al (SO ₄ ) ₃ , AlCl ₃ and NaAlO ₂ . Way. The method of claim 1, wherein the metal alkoxide is one selected from the group consisting of titanium (IV) alkoxides, aluminum alkoxides, and silicon alkoxides. The method of claim 1, wherein the cationic surfactant is cetyltrimethylammonium bromide or cetyltrimethylammonium chloride. The method of claim 1, wherein the ethanol acid solution is dissolved in HCl, H ₂ SO ₄ , or HNO ₃ in ethanol to have a concentration of 1 to 2N crystalline molecular sieve having a mesoporous structure. a) preparing a first solution by dissolving 2 to 20 parts by weight of silica alone or a mixture of a metal salt or a metal alkoxide (Si / metal molar ratio of 10 or more) with respect to 100 parts by weight of a hydrogen fluoride solution at a concentration of 5 to 50%; b) preparing 2nd solution by dissolving 2-12 weight part of nonionic surfactants with respect to 100 weight part of distilled water; And c) 20 to 30 parts by weight of concentrated ammonia water (based on 100 parts by weight of hydrogen fluoride solution) by adding the first solution to the second solution in a weight ratio of 1 to 2: 1 (second solution: first solution) and mixing the mixture uniformly. A method of producing a crystalline molecular sieve having a mesoporous structure, comprising the step of aging) at 25 to 80 ° C. for 10 to 18 hours, followed by filtration and drying. The method of claim 6, further comprising d) adding the powder to 200 to 300 parts by weight of ethanol acid solution (based on 100 parts by weight of hydrogen fluoride solution) and calcining at 300 to 600 ° C. for 2 to 4 hours. Method for producing a crystalline molecular sieve having a mesoporous structure, characterized in that. The method of claim 6, wherein the nonionic surfactant is a method for producing a crystalline molecular sieve having a mesoporous structure, using 4-octylphenoxypolyethylene alcohol. The crystalline molecular sieve having a mesoporous structure according to claim 6, wherein the metal salt is one selected from the group consisting of Al (NO ₃ ) ₃ , Al (SO ₄ ) ₃ , AlCl ₃ and NaAlO ₂ . Way. The method of claim 6, wherein the metal alkoxide is one selected from the group consisting of titanium (IV) alkoxides, aluminum alkoxides, and silicon alkoxides. 8. The method of claim 7, wherein the ethanol acid solution is dissolved in HCl, H ₂ SO ₄ , or HNO ₃ in ethanol to have a concentration of 1 ~ 2N crystalline molecular sieve having a mesoporous structure.