JP5059428B2 - Method for producing dual pore silica - Google Patents

Description

  The present invention relates to a novel method for producing binary porous silica. Specifically, there are two types: macropores having a pore size in the micrometer region formed by forming a structure in which the silica skeleton is intertwined, and nanopores having a pore size in the nanometer region existing in the silica skeleton. The present invention relates to a novel process for producing dual pore silica having pores of the following types. The binary porous silica obtained by the production method of the present invention is suitably used for, for example, a column support for chromatography, a solid catalyst, a catalyst support, an adsorbing material, a separating material and the like.

  Binary pore silica is an inorganic porous material having both macropores having a pore size in the micrometer range and nanopores having a pore size in the nanometer range. This dual-pore silica makes use of the synergistic effect of macropores with excellent material transport capability and nanopores with high specific surface area, which can greatly improve efficiency in fields such as catalytic reactions and separation / purification processes. I can expect.

  Conventionally known binary pore silica is, for example, as described in Patent Document 1, a sol solution comprising a water-soluble polymer such as silicon alkoxide represented by tetraethoxysilane, polyethylene oxide and an acid and an acid as a starting material. Then, it can be produced by forming macropores by utilizing the gelation phenomenon and phase separation phenomenon of the sol liquid.

  Controlling macropores and nanopores (pore diameter, pore volume, etc.) in the production of this dual pore silica also leads to expanded applications of the resulting dual pore silica. Therefore, various studies have been conducted.

  In order to control the nanopore, a gel body obtained from a sol solution containing a silicon source, an aqueous polymer, and an acid is converted into a liquid capable of dissolving silica, specifically 0.01 to 10 N alkali. A method of immersing in an aqueous solution or an aqueous solution containing fluorine ions is known (see, for example, Patent Document 2 and Patent Document 3). The method of controlling nanopores using an aqueous alkaline solution will be described. For example, in the example of Patent Document 2, a gel body is changed to an aqueous ammonia solution of 0.1 to 1 N (0.1 to 1 mol / L). A method of dipping and treating the temperature at the time of dipping at 25 to 60 ° C. is described. According to this method, the pore diameter of the nanopore can be changed in the range of 6 nm to 18 nm, and the pore volume of the nanopore can be adjusted. Patent Document 3 shows that the nanopores can be controlled by immersing the gel body in an alkaline aqueous solution of 0.01 to 10 N. In Examples, 0.1 N (0.1 mol / L An example of treating a gel body using an aqueous ammonia solution) is shown.

  As described above, in the prior art, it is known to immerse the gel body in an alkaline aqueous solution having a concentration of 0.1 to 10 N in order to control the nanopores when producing the dual pore silica. It was. However, in actuality, only an aqueous ammonia solution having a concentration of up to 1N (1 mol / L) is used to control the nanopore, and the gel body is treated with a higher concentration alkaline aqueous solution. There were no examples.

  Further, as described above, a method for controlling nanopores using an aqueous alkali solution or the like has been known, but a method for controlling macropores has not been known. In the conventional method, in order to control the macropores, it has been the mainstream to control by the composition of the sol solution charged first (raw material composition of silicon source, water-soluble polymer, acid, etc.).

  Therefore, in order to widen the range of production conditions, it has been desired to develop a method for producing dual-pore silica capable of controlling macropores even during the production process. Furthermore, in order to increase the utility value of the binary pore silica, a production method capable of easily controlling the pore volume and pore diameter distribution of the macropores has been desired.

Japanese Patent Laid-Open No. 3-8729 JP 7-41374 A JP 2005-162504 A

  In the case of using dual pore silica for a column carrier, catalyst carrier, adsorbent, etc., control of macropores is also important. If the pore diameter and pore volume of these macropores can be controlled by manufacturing conditions other than the raw material composition, the range of manufacturing conditions will be widened, and binary porous silica having various pores can be freely produced. It becomes possible to do.

  In addition, if the pore volume and pore diameter distribution of the macropores can be controlled, higher performance binary pore silica can be produced. The resulting binary porous silica is expected to be usable for, for example, a column carrier having high separation ability without tailing and a high-performance catalyst carrier having excellent selectivity.

  Accordingly, an object of the present invention is to provide a method capable of controlling macropores in addition to the raw material composition in the production of binary pore silica.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the sol solution composed of a silicon source, a water-soluble polymer, and an acid is gelled in an excessively phase-separated state, and the obtained gel body is immersed in an aqueous alkali solution having a specific concentration to achieve the above object. The present inventors have found that this can be done and have completed the present invention.

  That is, in the present invention, after a sol solution containing a silicon source, a water-soluble polymer, and an acid is gelled in a state of transient phase separation, the obtained gel body exceeds 1 mol / L and exceeds 10 mol / L. It is a method for producing dual-pore silica, characterized by immersing in ammonia water having the following concentration.

  According to the present invention, compared with a conventional aging treatment (a treatment in which a gel body is immersed in a liquid capable of dissolving silica, for example, a treatment in which the gel body is immersed in an aqueous alkaline solution such as aqueous ammonia) In addition to being controllable, the pore size distribution and pore volume of the macropores can be controlled. This control is not based on the raw material composition, but is performed by aging treatment, and the range of production conditions for the dual pore silica can be expanded.

  And according to this invention, the pore volume of a macropore can be controlled, and the binary pore silica which has a uniform macropore with a narrow pore diameter distribution can be manufactured.

  Therefore, the dual pore silica obtained by the present invention has both macropores excellent in material transport ability and nanopores having a high specific surface area, and the pore diameter of the macropores is uniform, For example, it can be suitably used for chromatographic column carriers, solid catalysts, catalyst carriers, adsorbents, separation materials and the like, and it is considered that the contribution to the industry is extremely large.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  The binary porous silica obtained by the production method of the present invention has a structure in which silica skeletons are intertwined. The “structure in which the silica skeleton is entangled” in the binary pore silica means that the silica polymer and the solvent phase are gelated (fixed) in a phase-separated state, and the solvent phase is removed to remove the solvent phase. This refers to a structure in which a phase is present as a void and a silica polymer is intricately entangled as a skeleton, and an example of a cross-sectional SEM observation of the structure is shown in FIG.

  In this structure, the location where the solvent phase is present, that is, the voids have penetrating pores (this is referred to as “macropore” in the present specification). When used for a column or the like, it can act as a flow path for a reaction solution or a treatment solution.

  On the other hand, small pores (hereinafter referred to as “nanopores”) are also formed in the silica skeleton itself, and when this dual pore silica is used for applications such as catalyst carriers and columns, In addition, a functional substance such as a catalyst can be filled to act as a reaction or adsorption point.

  In such a dual pore silica, a sol solution containing a silicon source, a water-soluble polymer, and an acid is gelled in a state where the phase separation is in a transient state, and then the obtained gel is dissolved in the silica content. It can be obtained by aging in a liquid (for example, an aqueous alkali solution) that can be obtained, and drying, firing, and hydrothermal treatment as necessary. The operation until the gel body is produced can be performed according to the methods described in JP-A-3-8729, WO2002 / 085785, JP-A-2005-162504, and the like.

  First, the sol solution will be described.

  In the present invention, the sol solution contains a silicon source, a water-soluble polymer, and an acid.

  In the present invention, as the silicon source, silicon alkoxide such as methoxysilane and ethoxysilane, and water glass are used without particular limitation. Especially, since water glass is cheap, it can be used conveniently. This water glass is generally a concentrated aqueous solution of alkali silicate, and the kind and concentration thereof are not particularly limited, but sodium silicate JIS 3 which is a water glass of JIS standard or equivalent is easy to handle as a silicon source.

  In the present invention, the water-soluble polymer is theoretically an organic polymer that can form a solution having an appropriate concentration, and a polymer that can be uniformly dissolved in a solution containing a silicon source can be preferably used. The water-soluble polymer may be determined appropriately according to the type of the silicon source and the like, specifically, a sodium salt or potassium salt of polystyrene sulfonic acid that is a polymer metal salt, Polyacrylic acid which is a polymer acid and dissociates to become a polyanion, polyacrylamine or polyethyleneimine which is a polymer base and generates a polycation, polyethylene oxide which is a neutral polymer and has an ether bond in the main chain, Polyvinyl alcohol having a hydroxyl group in the side chain, polyvinyl pyrrolidone having a carbonyl group, polyethylene glycol, or the like can be used. Of these, polyacrylic acid and polyvinyl alcohol are preferred because they are easy to handle. Further, the polyacrylic acid has a molecular weight of 15,000 to 300,000, preferably 20,000 to 150,000.

  In the present invention, the acid acts as a catalyst for the hydrolysis reaction and is added to promote gelation. Usually, a mineral acid such as sulfuric acid, hydrochloric acid, nitric acid, or an organic acid is used. Among them, it is preferable to use a mineral acid such as sulfuric acid, hydrochloric acid, and nitric acid in consideration of treatment of waste liquid and the like.

  In the present invention, the sol solution contains the silicon source, the water-soluble polymer, and the acid, and it is preferable to use water as the solvent (medium) used in the preparation of the sol solution.

  In the present invention, the procedure for preparing the sol liquid is not particularly limited, but it is preferable to finally mix the silicon source and the acid. Specifically, after mixing the silicon source and the water-soluble polymer, a method of mixing the mixed solution and the acid, mixing the water-soluble polymer and the acid, and then mixing the mixed solution and the silicon source. The method of doing is mentioned. At this time, the mixing procedure of the silicon source and the water-soluble polymer is not particularly limited, and the silicon source may be added to the water-soluble polymer, or conversely, the silicon source may be added to the water-soluble polymer. Further, the mixing procedure of the silicon source and the acid is not particularly limited.

In the present invention, the ratio of the silicon source, the water-soluble polymer, and the acid contained in the sol liquid is exemplified by a general ratio. The silicon source has a SiO ₂ content of 2 to 30% by mass in the sol liquid. It is preferable to mix | blend so that it may become, and it is preferable to mix | blend so that it may become 6-20 mass% especially. The concentration of the water-soluble polymer is preferably 0.05 to 5% by mass in the sol solution, and particularly preferably 0.5 to 2% by mass. The acid concentration is in the range of 0.1 to 5 mol, preferably 1 to 4 mol per liter of the sol solution, and the pH of the sol solution is preferably 2 or less. These blending ratios are preferably confirmed by conducting a preliminary experiment because the conditions under which the binary porous silica can be produced differ depending on the raw materials used and the combination of the raw materials.

  Next, in the present invention, the sol solution prepared by the above method is gelled in an excessive phase separation state to obtain a wet gel body. In order to cause the sol solution to gel in this manner, the sol solution is placed in a sealed container or the like and allowed to stand at 0 to 90 ° C., preferably 20 to 70 ° C. for 10 minutes to 1 week, more preferably 1 to 24 hours. To do.

  In the present invention, when water glass is used as a silicon source, a washing treatment is preferably performed to remove alkali metal such as sodium before drying the wet gel body. This is because when a wet gel body made of water glass (alkali metal silicate) is dried as it is, the gel body collapses as the drying proceeds. This washing treatment is performed with a solvent capable of removing the alkali metal contained in the gel body, and it is preferable to use water as the solvent. Moreover, the said washing | cleaning process can also wash | clean by passing water through a gel body, and can also wash | clean on the conditions (time and temperature) which can soak a gel body in water and can reduce an alkali metal sufficiently. In addition, this washing | cleaning process can also be implemented before the process which immerses the gel body explained in full detail below in aqueous ammonia, and can also be implemented after this process. Among these, in consideration of the cleaning efficiency and the like, the cleaning process is preferably performed before the process of immersing the gel body in aqueous ammonia.

  In the present invention, the gel body obtained by the above method is immersed in ammonia water having a concentration of more than 1 mol / L and not more than 10 mol / L (hereinafter, the gel body exceeds 1 mol / L). (A treatment for immersing in ammonia water having a concentration of 10 mol / L or less may be an aging treatment.) In the aging treatment, the present invention can control macropores by using ammonia water having a concentration of more than 1 mol / L and not more than 10 mol / L.

  As described above, the blending ratio of the binary porous silica varies depending on the silicon source, the water-soluble polymer, and the acid used. In such binary porous silica, macropores have been mainly controlled by adjusting these raw material compositions. However, since the production conditions of binary porous silica differ depending on the raw materials used, in order to produce various binary porous silicas with different macropores, the raw material composition must be changed each time. It was. Therefore, in order to efficiently produce binary porous silica having different macropores in order to cope with various applications, development of a method capable of controlling macropores regardless of the raw material composition has been desired. . The present invention solves such a problem.

  In the prior art, in this aging treatment, only 0.1 to 1 N (0.1 to 1 mol / L) ammonia water was used to control the nanopores at most. With this concentration of alkaline aqueous solution, it was possible to control nanopores, but it was not possible to control macropores. The present invention controls not only the nanopores but also the pore size distribution and pore volume of the macropores by adjusting the ammonia water to a specific concentration (above 1 mol / L and not more than 10 mol / L). To do. That is, according to the present invention, the half width of the peak of the macropores of the binary pore silica can be made narrower (the pore size distribution becomes narrower and more uniform macropores), and The pore volume of the macropores can be increased.

  In the present invention, ammonia water is used for the aging treatment. Other alkaline aqueous solutions, such as an aqueous solution of an alkali metal hydroxide salt (sodium hydroxide aqueous solution, etc.) are not preferred because alkali metal may remain in the dual pore silica. On the other hand, when ammonia water is used, ammonia can be easily removed in a subsequent process, so that the purity of the dual pore silica can be further increased.

  Moreover, the density | concentration of the ammonia water used for an aging process exceeds 1 mol / L, and is 10 mol / L or less. When the concentration of ammonia water (the concentration of ammonia (mol) in the aqueous solution (1 L) used for the aging treatment) is 1 mol / L or less, the nanopores are mainly controlled, and the macropores cannot be sufficiently controlled. Therefore, it is not preferable. On the other hand, when it exceeds 10 mol / L, the effect of controlling the macropores reaches a peak, and the treatment of waste water containing ammonia after the aging treatment becomes difficult, which is not preferable. Considering the macropore control effect and the post-treatment, the concentration of the ammonia water used for the aging treatment is preferably 1.5 mol / L to 9 mol / L, and more preferably 2 mol / L to 8 mol / L. Preferably there is.

  In the conventional technique, it is impossible to control the macropores by immersing the gel body in a specific concentration of aqueous ammonia when performing the aging treatment. In other words, according to the conventional knowledge, it was thought that the silica content was mainly dissolved by simply increasing the ammonia concentration, so that nanopore control and pore volume control are possible. It was unthinkable that the pores could be controlled. In particular, it was not conceivable that the pore size distribution of the macropores was narrowed and more uniform macropores were obtained.

  However, the present inventors surprisingly made the pore size distribution of macropores (in the examples, by making the concentration of aqueous ammonia used for the aging treatment more than 1 mol / L and not more than 10 mol / L, It was found that the peak half-value width can be narrowed. The reason for this is not clear, but is estimated as follows. By using ammonia water exceeding 1 mol / L and not more than 10 mol / L, the dissolution and reprecipitation reaction of the silica in the wet gel becomes more active (the dissolved silica is easily reprecipitated). Since the silica skeleton is reinforced by the precipitation, it is presumed that the shrinkage of the wet gel body can be reduced. As a result, it seems that the macropores can be controlled (particularly, the pore size distribution can be narrowed). That is, it is considered that the macropores cannot be controlled simply by dissolving the silica content more, so the control of the macropores according to the present invention is achieved by reducing the shrinkage of the gel body. Estimated. And as above-mentioned, the effect acquired is not what can be predicted from the conventional knowledge.

  In the present invention, the temperature and time of the aging treatment may be appropriately determined according to the concentration of aqueous ammonia to be used, the desired dual pore silica, and the like. Usually, it is preferable to perform the aging treatment at a temperature of 0 to 80 ° C. and a time of 1 to 120 hours. By aging under these conditions, macropores can be sufficiently controlled in the production of binary pore silica.

  In the present invention, it is preferable that the gel body subjected to the aging treatment is left to stand at 30 to 80 ° C. for several hours to several tens of hours to be dried to form binary porous silica. Further, if necessary, for example, when strength is required, the dried dual-pore silica can be fired. This baking is preferably performed at a temperature of 500 to 1,100 ° C. in order to completely remove organic substances (such as water-soluble polymers) after drying. Also, hydrothermal treatment can be performed to control the nanopores.

According to the present invention, since it is possible to obtain a dual pore silica with controlled macropores, it has macropores in a range of 0.1 to 30 μm when measured by a mercury intrusion method, and a differential graph. The height of the macropore peak represented by the above formula can be 15 cm ³ / g or more, and the half-width of the macropore peak can be 1 μm or less. On the other hand, the nanopore has a nanopore in the range of 5 to 50 nm when measured by the mercury intrusion method, and the height of the nanopore peak represented by the differential graph is 10 cm ³ / g or more, and The full width at half maximum of the nanopore peak can be 3 nm or less. Further, since the pore volume of the macropores can be controlled, the ratio of the pore volume of the macropores to the nanopores ((macropore volume) / (nanopore volume)) is set to 1 or more. It is also possible.

  As described above, the binary pore silica obtained by the method of the present invention is specifically shown in Examples and Comparative Examples. However, the pore diameter distribution is narrower in the macropores than in the prior art, and is uniform. The pores can be made, and the pore volume can be increased. Therefore, when it is used for column carrier, catalyst carrier, filter material, etc., it can control the pore volume and pore size distribution of macropores with excellent material transport ability, so when used for column carrier or filter It is considered that the target substance can be easily separated, and further, when used as a catalyst carrier, functions such as improving the activity of the target reaction can be exhibited.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(Measurement of pore distribution of macropores and nanopores)
A measurement sample dried in advance at 120 ° C. for 12 hours was subjected to measurement of the pore distribution of macropores by a mercury intrusion method (Pantamaster-60 manufactured by Cantachrome). In the differential graph of the pore size distribution obtained by measurement, the maximum peak pore size that appears in the micrometer region is the macropore pore size, and the maximum peak pore size that appears in the nanometer region is the nanopore pore size. The pore volume was determined from the mercury intrusion amount in the pore region.

Example 1
Polyacrylic acid (hereinafter referred to as HPAA) having an average molecular weight of 25,000 was used as the water-soluble polymer, and water glass (No. 3 silica gel) was used as the silicon source. The charge composition was water: concentrated nitric acid: HPAA: water glass = 97: 37: 6.5: 55 in a weight ratio, and the mixture was stirred at room temperature to obtain a uniform solution, and then allowed to stand at 25 ° C. for gelation. The gel body obtained for sodium removal was washed with water. Thereafter, aging was performed in a 3 mol / L aqueous ammonia solution at 50 ° C. for 72 hours (aging treatment), followed by drying at 50 ° C. and baking at 600 ° C. It was confirmed with an electron microscope (FIG. 1) that the obtained binary porous silica had a structure in which through-holes having a pore diameter of 1.5 μm were entangled in a three-dimensional network. The pore diameter of the micropores of the binary pore silica measured by mercury porosimetry is 1.5 μm, the peak height is 16 cm ³ / g, the half-value width is 0.6 μm, the pore volume is 1.5 cm ³ / g, The pore diameter was 15 nm, the peak height was 11 cm ³ / g, the half-value width was 2.1 nm, the pore volume was 1.0 cm ³ / g, and the pore volume ratio of macropores to nanopores was 1.5 (Table 1). To show.) FIG. 2 shows the results of mercury intrusion measurement of the dual pore silica.

Example 2
The same operation as in Example 1 was performed except that the aging treatment of Example 1 was performed in a 5 mol / L aqueous ammonia solution at 50 ° C. for 24 hours. The pore diameter of the macropores of the binary pore silica measured by mercury porosimetry is 1.5 μm, the peak height is 17 cm ³ / g, the half-value width is 0.4 μm, the pore volume is 1.2 cm ³ / g, and the nanopores are fine. The pore diameter was 16 nm, the peak height was 11 cm ³ / g, the half width was 2.1 nm, the pore volume was 1.0 cm ³ / g, and the pore volume ratio of macropores to nanopores was 1.2 (see Table 1). Show.)

Comparative Example 1
The same operation as in Example 1 was performed except that the aging treatment in Example 1 was performed in a 0.1 mol / L aqueous ammonia solution at 50 ° C. for 72 hours. Pore size 2μm macropores dual pore silica as measured by mercury porosimetry, the peak height 11cm ³ / g, a half-value width 0.85 .mu.m, pore volume 0.7 cm ³ / g, pore size of nanopores 9 nm, peak height 8 cm ³ / g, half width 1.3 nm, pore volume 1.5 cm ³ / g, and the pore volume ratio of macropores to nanopores was 0.5 (shown in Table 1) .)

  As described above, by setting the concentration of ammonia water in the aging treatment to more than 1 mol / L and not more than 10 mol / L, the pore volume of the macropores can be increased, and the half width of the peak is narrowed. be able to. From this, according to the production method of the present invention, it is clear that binary porous silica having uniform macropores with a narrow half-width of the peak can be produced, and the macropores can be controlled.

2 is an electron micrograph of binary porous silica obtained in Example 1. FIG. FIG. 3 is a diagram showing the pore distribution of the binary pore silica obtained in Example 1.

Claims (1)

A sol solution containing a silicon source, a water-soluble polymer, and an acid is gelled in a transient state of phase separation, and the obtained gel is immersed in ammonia water having a concentration of 2 mol / L or more and 8 mol / L or less. A method for producing a dual pore silica.

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