JP2003261318A - Method for producing porous spherical particles and use therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing porous spherical particles having a large specific surface area and pores of uniform size and applicable to a catalyst carrier, an adsorbent, etc., and to provide uses for the particles. <P>SOLUTION: Porous spherical particles concerned with this invention can be produced by controlling the molar ratio of water to alkoxysilanes to 50-250 when the alkoxysilanes are added to a liquid mixture of alkylamines and water and by carrying out mixing at 0-40°C for 1-150 hr. Porous spherical particles thus obtained have 5-200 μm diameter and 900-1,800 m<SP>2</SP>/g specific surface area, in the pore size distribution curve, the pore diameter at the highest peak is in the range of 9-50 Å, and in a powder X-ray diffraction pattern, the particles have one or more peaks at an angle of diffraction corresponding to d value of 15-70 Å. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing porous spherical particles applicable to catalyst carriers, adsorbents and the like, and uses of the porous spherical particles.

[0002]

2. Description of the Related Art A porous material having uniform mesopores synthesized by utilizing self-organization of an organic compound and an inorganic compound has a smaller pore volume than conventional porous materials such as silica gel and zeolite. It has a large surface area and a large surface area, and is attracting attention. As a method for producing a porous material having uniform mesopores by utilizing self-organization of an organic compound and an inorganic compound, for example, WO-91 / 11390 may be used in a heat-resistant container in which silica gel and a surfactant are hermetically sealed. Manufacturing method by thermal synthesis, Bull. Chem. So
c. Jp., (1990) 63, 988, a method for producing by ionic exchange between kanemite, which is a kind of layered silicate, and a surfactant is known.

These are characterized by having regularly arranged pores such as lamella, hexagonal, cubic, etc., and their application to adsorbents, sensors, catalyst carriers, electronic materials, optical materials, fuel cells, etc. is under consideration. Has been done. The porous material having such a pore structure is produced as fine particles or fine crystals, but it is also produced in the shape of a fiber, a thin film or the like, and is used according to the application. For example, Adv. Mat
er., (1999), 11, No. 4, 303, the production method for the fiber is shown, and Chem. Mater., 9, (1997), 1962, the production method for the thin film is shown. And is being applied to optical materials and electronic materials. On the other hand, spherical shaped particles are desired for use as a fluidized bed catalyst, a carrier thereof, or an adsorbent having a high bulk specific gravity and a good packing property. Spherical particles having a uniform particle size of submicron or smaller are shown in Nature, 398, (1999), 223, etc. However, this method cannot make the size of several microns usable as a carrier.

Conventionally, as a method for producing a silica-based porous glass, a production method utilizing the phase separation phenomenon of glass, that is, a silica-based glass containing various metal oxides is heat treated for a long time at a temperature below the softening point, A method is known in which a silica phase as a skeleton and a soluble metal oxide phase are separated, and the soluble phase is eluted with an acid. However, this method cannot produce pores having a diameter of 40 Å or less.

A manufacturing method by the sol-gel method is also known. For example, in Japanese Unexamined Patent Publication No. 62-230636, it is manufactured by synthesizing silica particles having a uniform particle size by a sol-gel method, precipitating the particles, hardening them, and then sintering them. In this case, since the voids of the particles are used, the porosity cannot be increased. In addition, JP-A-62-59
In 553, spherical particles are obtained by spray drying a uniform solution by the sol-gel method, and the specific surface area of the obtained spherical particles is 300 m ² / g or less.
In JP-A-10-328558, a spherical mesoporous material having a diameter of 2 mm or less is manufactured. According to this method
It is manufactured by previously mixing a raw material alkoxysilane and water, a surfactant and an acid to prepare a solution, and injecting this into an alkali-added organic solvent. Since this method requires the use of a large amount of organic solvent, there is a problem in waste liquid treatment.

Further, in Japanese Patent Laid-Open No. 2001-2409, an acidic aqueous solution is added to a mixed solution of alkoxysilane and 1-alkylamine with stirring, and the 1-alkylamine is removed from the produced complex to obtain spherical particles. We manufacture mesoporous materials. In this method, since an acidic aqueous solution is used, there is concern about device corrosion. In particular, the use of hydrochloric acid is not a preferable method because there is a concern that dioxin may be generated during firing.

Therefore, it has been desired to develop a method for producing porous spherical particles which can be produced relatively easily and inexpensively.

[0008]

OBJECT OF THE INVENTION It is an object of the present invention to provide a method for producing porous spherical particles having a large specific surface area and having pores of a uniform size, which can be applied to a catalyst carrier or an adsorbent, and an application thereof. .

[0009]

SUMMARY OF THE INVENTION As a result of intensive studies to solve the above problems, porous spherical particles control the mixing ratio of water and alkoxysilanes when adding alkoxysilanes to a mixed solution of alkylamines and water. In addition, the present invention was found to be possible by controlling the mixing conditions and the present invention, leading to the present invention.

That is, the porous spherical particles according to the present invention have a general formula YNH ₂ (wherein Y represents C _m H _{2m + 1} , and m =
A mixture of water and an alkylamine represented by an even number of 6 to 18) and general formula (ZO) _4-n SiR _n (wherein Z represents C _x H _{2X + 1} and X = 1). 4 and R may be the same as or different from Z, and n = 0 to 3). When mixed with an alkoxysilane represented by The present invention is characterized in that porous spherical particles having an average diameter of 5 to 200 μm are produced by setting the mixing molar ratio of the alkoxysilanes (water / alkoxysilanes) in the range of 50 to 250.

It is desirable that the mixture of the alkylamines and water and the alkoxysilanes be mixed at 0 to 40 ° C. for 1 to 150 hours. The porous spherical particles produced by the above method have a diameter of 5 to 200 μm, a specific surface area of 900 to 1800 m ² / g, and a maximum peak pore diameter of 9 to 50 Å in the pore diameter distribution curve. And in the powder X-ray diffraction pattern,
It has one or more peaks at a diffraction angle corresponding to a d value of 70Å.

In addition, a binder is added to the porous spherical particles, and the particles are coated and carried on the surface of the base material,
It can be used as an adsorbent.

[0013]

DETAILED DESCRIPTION OF THE INVENTION The method for producing porous spherical silica according to the present invention will be specifically described below. In order to produce porous spherical silica, for example, first the general formula YNH
₂ (in the formula, Y represents C _m H _{2m + 1} and m is an even number from 6 to 18), and a mixed solution of an alkylamine and water is prepared.

Examples of such alkylamines include hexylamine, octylamine, decylamine,
Dodecylamine, myristylamine, hexadecylamine, stearylamine and the like can be mentioned. These alkylamines may be used alone or in combination of two or more. The mixing ratio of the alkylamines and water is not particularly limited as long as the alkylamines can be uniformly dispersed in water and the micelles of the alkylamines are formed. Specifically, water is 30 mol to 300 mol, preferably 50 to 200 mol, per 1 mol of alkylamines.
It is desirable to make it molar.

Of a mixed solution of this alkylamine and water
The pH is about 10, but a pH adjustor may be added within the range of 9 to 13. However, considering corrosion and the like, it is preferable not to add an acid. The stirring for homogenizing the solution is usually performed for about 10 minutes to 1 hour,
It is also possible to use ultrasonic stirring together. The temperature of this mixed solution is 0 to 50 ° C, preferably 0 to 40 ° C. By the operation of making this solution uniform, the alkylamines form micelles. When alkoxysilanes are mixed with this mixed solution, a precursor of porous silica having uniform pores is formed by self-assembly of alkylamines and a hydrolyzate of alkoxysilanes. JP 2
In 001-2409, first, an alkoxysilane and 1-alkylamine are mixed, but in this state, micelle formation of 1-alkylamine cannot be sufficiently performed. As described in the embodiment of the publication, the silica mesostructure is converted into an acidic aqueous solution.

In the present invention, it has been found that the precursor of porous spherical silica can be formed in a basic solution by sufficiently mixing the alkylamines and water in advance. That is, in a mixed liquid of this alkylamine and water,
General formula (ZO) _4-n SiR _n (In the formula, Z represents C _x H _{2X + 1} , X = 1 to 4, R may be the same as or different from Z, and n = 0 to 3 By adding a solution containing alkoxysilanes represented by the formula (1), a precursor of porous spherical silica having uniform pores is formed. Further, at this time, seed crystals may be added in order to facilitate the formation of precipitates in the mixed liquid of alkylamines and water.

Examples of the alkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and tetrabutoxysilane. In particular, the use of tetraethoxysilane is preferable. Further, a solvent may be added to the alkoxysilanes to dilute them for use. Examples of such a solvent include primary alcohols such as methanol, ethanol and 1-propanol, secondary alcohols such as 2-propanol and 2-butanol, tertiary alcohols such as tertiary butyl alcohol, acetone and acetonitrile. This solvent may be used alone or in combination of two or more. Further, by diluting the alkoxysilanes with a solvent, it is expected that the rapid hydrolysis of the alkoxysilanes when added to the alkylamines can be controlled. Usually, the amount of solvent used is alkoxysilanes 1
It is used in an amount of 20 mol or less, preferably 5 to 20 mol, based on mol.

The mixing ratio of the alkoxysilanes and the alkylamines is 0.05 to 1.5 mol, preferably 0.2, of the alkylamines per mol of the alkoxysilanes.
It is desirable to be in the range of up to 1.3 mol. Alkylamines have a role of pH control in addition to the role of a template for pore formation, and although there are no problems in many cases, they are not preferable from the viewpoint of manufacturing cost. As mentioned above, if the pH is in the range of 9 to 13, a uniform complex is formed after aging and, when alkylamines are removed, a porous material having mesopores of uniform size is formed. Silica can be obtained.

By mixing the alkoxysilanes with a mixed solution of alkylamine and water, a hydrolysis reaction of the alkoxysilanes occurs, a complex is formed with the alkylamines by self-assembly, and a precipitate is formed. . The mixing method of the alkoxysilanes at this time is not particularly limited, but the reaction is relatively fast, and thus strong stirring is desirable.
Further, during the reaction, a slight amount of heat is generated, and if the temperature is too high, the uniformity of the pores decreases, so 0 to 40 ° C., preferably 0
It is desirable to control in the range of ˜35 ° C.

The mixture of the alkylamines and water and the alkoxysilanes are mixed with stirring at 0 to 40 ° C.
Desirably, in a temperature range of 0 to 35 ° C., for 1 to 150 hours,
Desirably, it is performed for 3 to 48 hours. By continuing this mixing, an organic-inorganic composite of a polycondensate of silica and an alkylamine is formed with a more regular structure. Further, at this time, the mixing molar ratio of water and alkoxysilanes (water / alkoxysilanes) is set to 50 to 250, preferably 80 to 250, and more preferably 80 to 200 to form porous spherical particles. Is important to let. With this molar ratio, the solution concentration is suitable for aging, and a precursor of porous spherical particles as an organic-inorganic composite is formed.

The thus-obtained solution containing the spherical organic-inorganic composite is filtered and the liquid portion is removed. The organic-inorganic composite obtained by filtration can be optionally washed with water. Although it is possible to wash with alcohol, the structure is still unstable before drying, and the alcohol is likely to dissolve the alkylamines and the pore structure is likely to collapse, so it should be avoided.
The obtained organic-inorganic composite is then dried to remove the residual solvent, water and the like. The drying conditions are not particularly limited as long as they are not exposed to a high temperature of 80 ° C. or higher in a wet state, and may be vacuum dried or air dried. It is desirable to avoid exposing to a high temperature of 80 ° C. or higher in a wet state because the structure may change.

When the alkylamines are removed from the organic-inorganic composite as the precursor, a porous body in which the alkylamines are vacant is formed. As a method for removing the alkylamines, there is baking or extraction with alcohol or the like. When extraction is performed, sufficient drying and, if necessary, calcination are required to remove the solvent remaining after extraction. When firing is performed, there is no particular limitation as long as the alkylamine can be decomposed or removed by firing, but if the temperature exceeds 1000 ° C., the structure changes, which is not preferable. Further, the atmosphere may be in the air or in an inert gas as long as it is not in a humidified state. Normally, this firing is 30
It is carried out at 0 ° C. to 800 ° C. for 1 to 10 hours, preferably 3 to 10 hours.

By the above operation, the average diameter is 5 to 20.
It is in the range of 0 μm and has a specific surface area of 900 to 1800 m ^2.
/ G, the pore diameter of the maximum peak in the pore diameter distribution curve is in the range of 9 to 50Å, and the powder X-ray diffraction pattern has one or more diffraction angles corresponding to the d value of 15 to 70Å. Porous spherical silica particles having a peak of are obtained, and these spherical particles can be used as a catalyst carrier or an adsorbent material.

When the porous spherical silica particles thus obtained are used as a water adsorbent, it is desirable that the calcined particles be made hydrophilic by a humidification treatment.
That is, the porous body is 20 to 80 ° C., preferably 20 to 80 ° C.
Relative humidity of water is 40-90 in the temperature range of 60 ° C.
%, Preferably 40 to 60%, for 1 to 10 hours, preferably 1 to 5 hours, to treat the surface without structural collapse.

The porous spherical silica obtained by the present invention has a large adsorption amount of water at a low vapor pressure. For example, at an atmospheric pressure of 25 ° C. and a relative humidity of 10 to 50%, the adsorption amount of water is 0.2 to It is about 0.5 g / g-silica. The water adsorption amount of such porous spherical silica is measured as follows. First, the sample to be measured is put into a sample tube having a volume of about 5 ml and deaerated until the inside of the system becomes 0.13 Pa or less. After that, an automatic vapor adsorption amount measuring device (BELSOR
P18 PLUS; made by Nippon Bell Co., Ltd., temperature 2
Water vapor adsorption test was performed at 5 ℃, each relative humidity (P / Ps)
Determine the amount of water adsorbed in.

It is also possible to add a binder to the thus-obtained porous spherical particles and apply the binder to a substrate to carry it as a film on the substrate for use. In this case, a method of applying this moistening treatment, applying it on the base material, and drying it at 100 ° C. or lower and using it is preferable from the viewpoint of performance reproducibility. As the binder when applied to the substrate, either organic or inorganic binders can be used. For example, in the organic type, there are vinyl acetate, methyl cellulose, polyvinyl alcohol, epoxy resin, polyalkylene oxide, polyalkylene glycol and the like, and in the inorganic type, silica type, alumina type, cement and the like can be used. The amount of the binder to be added is not particularly limited, but it is preferable to add it in such an amount that it has sufficient adhesive force and does not reduce the water absorption amount of the porous spherical silica.
It is 5 to 20% by weight.

As the base material, any base material that is generally used can be used. Examples include metals such as copper and aluminum, ceramics, metal oxides, glass, and alloys such as stainless steel. Further, the shape of the base material may be any of a honeycomb shape, a cylindrical shape, a plate shape, a dish shape, a complicated shape with fins, or the like. The coating liquid for coating the substrate can be prepared by adding and mixing porous spherical silica in a solvent in which a binder is dissolved or dispersed. Examples of the method for applying the coating liquid to the substrate include general methods such as a spraying method, a spin coating method, a casting method and a dip coating method.

The film thickness of the supporting film is not particularly limited, as long as it is a thickness capable of effectively exhibiting the adsorption performance, and usually 1 μm.
It is about 2 mm. The supporting film thus obtained has a very excellent performance as an adsorbent.

[0029]

EXAMPLES The present invention will be described in more detail below with reference to examples. Here, the pore diameter of the maximum peak refers to the maximum value found in the pore diameter distribution curve calculated from the nitrogen adsorption amount by the BJH method. Further, the specific surface area is a value measured by N ₂ adsorption and obtained by the BET method.

[0030]

Example 1 Octylamine (C ₈ H ₁₇ NH ₂ ) 10.0
g and 140 g of water were mixed and stirred to prepare a uniform solution. Tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ) dissolved in 23.5 g of ethanol (C ₂ H ₅ OH) was added to this solution.
16.2 g was added. The mixing molar ratio of each component at this time is tetraethoxysilane: water: octylamine: ethanol = 1.0: 100: 1.0: 6.5. This mixed solution was aged at 35 ° C. for 18 hours while stirring.
After aging, the resulting organic-inorganic composite was filtered with a suction filter to separate a white precipitate, and the precipitate was washed with water and dried. Firing was performed at 600 ° C. for 3 hours to remove octylamine from the obtained organic-inorganic composite. The powder after firing had a peak representing a hexagonal structure by X-ray diffractometry. When the specific surface area of this particle was measured, it was 1
It was 360 m ² / g. Moreover, when the pore distribution was measured by the nitrogen adsorption method, the maximum peak pore diameter was 17.6Å
Met. The results of SEM observation of these particles are shown in FIG. The particle size was 20 to 50 μm, and it was confirmed that porous spherical particles could be produced.

This porous spherical silica was kept in an atmosphere of 30 ° C. and a relative humidity of 50% for 4 hours. The humidified porous silica had a peak representing a hexagonal structure by an X-ray diffraction method, and had a specific surface area of 1340 m ² / g, and the pore structure hardly changed by the treatment. The water adsorption isotherm of the porous silica after this humidification treatment was measured. As a result of measurement at 25 ° C under atmospheric pressure, relative humidity 1
The amount adsorbed at 0% to 50% was 0.35 g / g-silica.

[0032]

Comparative Example The same operation as in Example 1 was performed except that the amount of water added was 50 g. The mixing molar ratio of each component is tetraethoxysilane: water: octylamine: ethanol = 1.0: 35.7: 1.0: 6.5. The powder after firing had a peak representing a hexagonal structure by X-ray diffractometry. When the specific surface area of this particle was measured, 13
It was 60 m ² / g. Moreover, when the pore distribution was measured by the nitrogen adsorption method, the maximum peak pore diameter was 17.6Å
Met. The results of SEM observation of these particles are shown in FIG. The particle shape was not spherical, and the powder was fluffy.

[0033]

[Example 2] The same operation as in Example 1 was carried out except that octylamine was removed by ethanol extraction and drying was performed.
Porous spherical silica was prepared. The powder after drying had a peak representing a hexagonal structure by X-ray diffractometry. As a result of measuring the specific surface area and the pore distribution of this porous silica by a nitrogen adsorption method, the specific surface area was 1180 m ² / g and the average pore diameter was 18.1Å. The diameter is 20-50
It showed a spherical shape of μm, and it was confirmed that porous spherical particles could be produced.

This porous silica was treated at 30 ° C. and a relative humidity of 50.
% Atmosphere for 4 hours. The humidified porous silica had a peak representing a hexagonal structure as determined by X-ray diffractometry, and the specific surface area was 1180 m ² / g, so that the pore structure was hardly changed by the treatment.

[0035]

Example 3 2.0 g of the humidified porous silica produced by the same operation as in Example 1 was dispersed in 44.0 g of water in which 0.1 g of methyl cellulose was dissolved. A carrier made of glass fibers formed in a honeycomb shape was dipped in the stirred slurry solution. After 2 minutes, the solution was pulled out and dried at 80 ° C. When this operation was performed twice, the supported amount of porous silica was 95% of the carrier.
Became.

The specific surface area of the supported porous silica was measured and found to be 1160 m ² / g. Further, the water adsorption isotherm of this powder was measured at 25 ° C. under atmospheric pressure, and as a result, the water adsorption amount at a relative humidity of 10% to 50% was 0.33 g / g-
It was silica, and it was found that there was no significant difference in the adsorption isotherms on the adsorption side and desorption side, and the hysteresis was small.

[0037]

Industrial Applicability It has become possible to provide a method for producing porous spherical particles having a large specific surface area applicable to a catalyst carrier, an adsorbent, etc. and having pores of a uniform size, and an application.

[Brief description of drawings]

1 is an SEM photograph of porous spherical particles obtained in Example 1. FIG.

FIG. 2 shows SE of porous particles obtained in Comparative Example.
It is an M photograph.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshito Kurano             580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals, Inc.             Inside the company (72) Inventor Kazuo Takamura             580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals, Inc.             Inside the company (72) Inventor Shunsuke Oike             580-32 Nagaura, Sodegaura-shi, Chiba Mitsui Chemicals, Inc.             Inside the company F-term (reference) 4G066 AA22B AB13D AB18A BA23                       BA26 BA31 BA36 CA43 FA03                       FA05 FA14 FA34 FA40                 4G072 AA25 BB07 BB15 GG01 GG03                       HH30 JJ13 JJ14 JJ42 JJ46                       KK11 MM01 RR01 RR12 TT02                       TT30 UU11 UU15 UU17

Claims (4)

[Claims] 1. A mixture of an alkylamine represented by the general formula YNH ₂ (wherein Y represents C _m H _{2m + 1} and m is an even number of 6 to 18) and water, and the general formula (ZO) _{4- n} SiR
_n (in the formula, Z represents C _x H _{2X + 1} , X = 1 to 4, and R
May be the same as or different from Z, and n = 0 to 3. ) In producing porous particles by mixing the alkoxysilanes represented by the formula (1), the mixing molar ratio (water / alkoxysilanes) of the water and the alkoxysilanes is 50 to 250.
In the range of 5 to 200 μm in diameter. 2. The method for producing porous spherical particles according to claim 1, wherein the mixing is performed at 0 to 40 ° C. for 1 to 150 hours. 3. The method according to claim 1, which has a diameter of 5 to 200 μm, a specific surface area of 900 to 1800 m ² / g, and a maximum peak diameter in a pore size distribution curve. The pore diameter is in the range of 9 to 50Å, and the powder X-ray diffraction pattern is 15 to 70.
A porous spherical particle having a diameter of 5 to 200 μm, which has one or more peaks at a diffraction angle corresponding to the d value of Å. 4. A heat pump adsorbent characterized by comprising adding a binder to the porous spherical particles according to claim 3 and applying the binder to the surface of the base material to carry the binder.