JPH08173797A - Adsorbent - Google Patents

Abstract

PURPOSE: To provide a white silica-based adsorbent which has a uniform mesopore and has practically no alkaline component, and which exhibits an adsorption performance as high as or higher than that of active carboh and has improved thermal stability. CONSTITUTION: The effective component of an adsorbent is mesoporous silica having porous structure which is prepared by firing a complex of active silica and a cation surface-active agent, and in which thephisical properties are such that average pore diameter is 10-100 angstrom, BET specific surface area 800m<2> /g or more, Na contents 1000ppm or less. The adsorbent may take the form of a powder or molded material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica-based adsorbent which is white and has high reproducibility and has high adsorption performance.

[0002]

2. Description of the Related Art Adsorbents have been used in various fields for a long time, and there are many kinds of adsorbents. For example, carbon-based adsorption of powdered activated carbon, granular activated carbon, bead activated carbon, molded activated carbon, activated carbon fiber, molecular sieving carbon, etc. Agent, silica gel, activated alumina, acid clay, activated clay, porous glass, silica-alumina-based adsorbents such as magnesium silicate, ion exchange resin,
A chelate resin, an amidoxime type resin, a polymer adsorbent such as a porous polymer, and a metal complex-based adsorbent resin are known. These adsorbents have different porosities, apparent densities, average pore diameters, surface areas, pore volumes, etc.,
There are various uses.

Of these, the most commonly used adsorbent at present is activated carbon. Activated carbon is mainly used for gas purification, solvent recovery, decolorization, water purification, wastewater treatment, etc.
It is also used to remove odors such as hydrogen sulfide, methyl mercaptan, and other acidic gases or ammonia, trimethylamine, and other basic gases by impregnating acids, alkalis, or catalyst components, etc. to prevent odor pollution. .
Molecular sieving carbon (Molecular sieving carbon; M
SC) is used for adsorption of solutes in aqueous solution because it is hydrophobic, and pressure swing adsorption for concentrating and separating nitrogen gas from air by utilizing different diffusion rates of oxygen and nitrogen in ultramicropores. It is also used as an adsorbent in the method.

Activated alumina is effectively used for drying gas and liquid, and silica gel is commonly used for desiccant for foods, medical products, dehumidifying agent for air, dehydration and drying of industrial gas, separation of hydrocarbons and the like. There is. Zeolite has a unique molecular sieving action, a high degree of hygroscopic action, and an adsorption action based on the polar effect, and has a large equilibrium adsorption amount at low partial pressure and high temperature, and also has a high adsorption rate. Is used as. In addition, since zeolite contains a metal cation inside the crystal, a polar molecule having a negative group, such as H
Applications to selectively adsorb ₂ O, NH ₃ , H ₂ S, SO ₂ and CO ₂ , applications for gas and liquid drying in petrochemistry, purification of hydrogen gas, separation of p-xylene and n-paraffins, etc. It is also used in.

However, since the activated carbon is composed of black carbon as a material, it cannot be changed to another color tone, and its use range is limited due to the progress of oxidative consumption in a heated oxidizing atmosphere. There are drawbacks. Zeolite has excellent selective adsorption to pollutant gas,
Since the pore size of the tissue is a micropore having a size of about 3 to 20 angstroms, it does not have a function of widely adsorbing and removing various gas components.

[0006] Further, activated alumina and silica gel are random aggregates of fine primary particles, and pores from micropores to macropores are distributed in the tissue, but their own adsorption function is not sufficient, and they are molded. It is also extremely difficult to control the pore size within a certain range by means. Therefore, even if it is used as a carrier, the field of use as an adsorbent is extremely limited.

By the way, Japanese Unexamined Patent Publication No. 6-24867 discloses a layered silica porous body derived from layered alkali silicate such as kanemite and a method for producing the same, and the silica porous body is octane, fuel or the like. It is described that the compound has excellent adsorption ability to the organic substance.

[0008]

However, since the layered silica porous material described in JP-A-6-24867 uses a layered alkali silicate as a raw material, it is difficult to substantially remove the alkali component. As well as
There is a problem that it is difficult to design a tissue structure in which mesopores with a uniform pore size are distributed, thermal stability becomes insufficient, and selective removal of adsorbed components and use as a catalyst based on adsorption function Has the drawback of limiting.

Recently, in addition to the industrial environment, various amenity products that improve the living environment in accordance with the pursuit of a healthy and comfortable life are demanded, and are related to adsorption, deodorization, deodorization, etc. The demand for new products is increasing, and there is a demand for the development of more functional adsorbents.

In view of such a background, the inventors of the present invention have an adsorbent material which has a high adsorption capacity of activated carbon but does not have the drawbacks peculiar to activated carbon. As a result of multi-faceted research on adsorbents, it was found that mesoporous silica, which uses a composite material composed of active silica and a cationic surfactant as a raw material system, satisfies the above-mentioned required physical properties, and has led to the development of the present invention.

Accordingly, an object of the present invention is to provide a white silica-based material having a uniform mesopore, containing substantially no alkali component, and exhibiting a high adsorption performance equal to or higher than that of activated carbon and excellent in thermal stability. It is to provide an adsorbent.

[0012]

The adsorbent according to the present invention for achieving the above object is a porous structure obtained by firing a complex of active silica and a cationic surfactant, and has an average fineness. Pore size 10-100 Å, BET
The structural feature is that mesoporous silica having physical properties of a specific surface area of 1000 m ² / g or more and a Na content of 1000 ppm is used as an active ingredient.

The adsorbent according to the present invention contains mesoporous silica as an active ingredient, but its production history is limited to that obtained by firing a complex of active silica and a cationic surfactant. By this requirement, a high-quality adsorbent having a Na content of 1000 ppm or less and substantially not containing an alkaline component and having excellent thermal stability is obtained.

Mesoporous silica, which is an active ingredient, has an intermediate pore size between micropores and macropores in its structure. Specifically, the average pore size is 10 to 100.
It has a uniform pore distribution of angstrom and has a porous structure having a BET specific surface area of 800 m ² / g or more.
This BET specific surface area is remarkably large in surface activity as compared with the BET specific surface area of silica gel or zeolite being in the range of about 200 to 600 m ² / g, and corresponds to a BET specific surface area equal to or higher than that of high performance activated carbon. The average diameter of the pore unit cells in the mesoporous silica structure can be calculated by measuring the distance d ₁₀₀ between the hexagonal structure (100) planes of the powder X-ray diffraction pattern and using this value by the formula [2d ₁₀₀ / √3]. The average pore size can be determined by the nitrogen adsorption method.

The mesoporous silica according to the present invention has a low crystallinity, but the crystallinity is clearly recognized by X-ray diffraction. Therefore, the pore size of the mesopores forming the structure is excellent in uniformity. Since this pore diameter can be arbitrarily adjusted in the production stage, it becomes easy to impart the selective adsorptivity of the adsorbed components, and it has an excellent function for selectively separating a specific component from the mixed composition. To be demonstrated. The mesoporous silica produced is an anhydrous white powder, and the apparent fineness can be adjusted by an appropriate pulverizer. However, it should be noted that excessive crushing may destroy the structural structure of mesopores. As the adsorbent of the present invention, powder mesoporous silica can be used as it is, but the powder can be molded and used as a molded body. It is also possible to improve the adsorption ability by supporting a desired drug or catalyst component depending on the purpose of use.

Examples of the substance to be adsorbed by the adsorbent according to the present invention include hydrogen sulfide, phosphine, arsine,
Various sulfur compounds such as methyl sulfide, methyl mercaptan, ethyl mercaptan, ammonia, monomethylamine,
Basic nitrogen compounds such as dimethylamine and trimethylamine, aldehydes such as formaldehyde, acetaldehyde and propionaldehyde, carboxylic acids and derivatives such as butyric acid and isovaleric acid, indoles such as indole and skatole, and phenols such as benzene and p-xylene. Not only odorous gases such as ethylene, but also a wide range of various organic substances such as unsaturated hydrocarbons such as ethylene such as ethane and ethylene, saturated hydrocarbons such as propane, butane, octane, and alcohols such as isopropyl alcohol. An adsorption spectrum is shown.

The mesoporous silica constituting the present invention is
It is produced by calcining a composite using active silica and a cationic surfactant as starting materials. The active silica serving as a silica source refers to silica having a composition having a siloxane bond partially condensed from silicic acid [Si (OH) ₄ ] but still having a silanol group. As the cationic surfactant which is one raw material system, a quaternary ammonium salt or an alkylamine salt is used. The quaternary ammonium salt has the general formula [R
_n (CH _{3) 4 -n]} ⁺ [X] ^- (wherein, R is a carbon number 8-2
A long-chain alkyl group of 4, n is an integer of 1 to 3, and X represents a halogen or an OH group), and a quaternary alkyltrimethylammonium salt and a quaternary dialkyldimethylammonium salt, and an alkylamine salt is generally Formula [RN
H ₃ ] ⁺ [X] ⁻ (wherein R is the same long-chain alkyl group as described above, n is an integer of 1 to 3, and X represents a halogen or an OH group). The mesopore size of silica to be produced can be appropriately designed by selecting these surfactants.

In the manufacturing process, activated silica prepared by contacting an aqueous solution of sodium silicate with a cation exchange resin and a cationic surfactant are mixed and reacted in an alkaline region to form a complex of silica and the cationic surfactant. , A step of baking the composite. The firing temperature applied in the firing step is equal to or higher than the temperature at which the surfactant component is burned off,
The temperature is set to approximately 500 ° C. or higher. Firing at a higher temperature is effective for stabilizing the structure of silica and improving the mechanical strength, but in the temperature range over 1200 ° C, the sintering reaction proceeds and contributes to the stabilization of the structure. Disappear. The firing time is appropriately set in relation to the treatment temperature, but a range of about 10 minutes to 1 hour is suitable. Therefore, a suitable firing condition is a firing temperature of 600 to 1200 ° C. and a firing time of 1 hour or less.

The absorbent according to the present invention is prepared by molding mesoporous silica alone into a powder or pellet, honeycomb or spherical shape. When it is formed as a molded body, it is made of a suitable inorganic or organic substance as a binder. Use a binder. In this case, as the inorganic binder, for example, alumina sol, silica sol, silica-alumina sol or clay is used, and as the organic binder, polyvinyl alcohol, CMC, MC, cyanoethylated starch, casein, sodium alginate, water-soluble cellulose derivative. Water soluble polymers such as, polyvinyl acetate latex, various synthetic resins such as SBR latex, synthetic rubber latex, and the like. You may use these 1 type or in mixture of 2 or more types. The amount of these binders used with respect to mesoporous silica varies depending on the form of use and is not particularly limited.

If desired, in order to improve the adsorption capacity and broaden the adsorption spectrum, other inorganic fine powder may be used in combination, or mesoporous silica powder or a molded product may be mixed with L.
Alkali agents such as hydroxides or carbonates of alkali metals such as i, Na and K, oxidizing agents such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and acidic aluminum phosphate, permanganate salts and chlorates of alkali metals, Oxidizing agents such as iodates, persulfates, ferrates, percarbonates and perborates, reducing agents such as alkali metal phosphites and hypophosphites, and other coloring agents, fragrances, etc. One or more drugs may be supported. The inorganic fine powder to be used in combination is, for example, a metal oxide such as alumina gel, titanate gel, zinc oxide, iron oxide, manganese dioxide, magnesium oxide, copper oxide, cuprous oxide, calcium oxide, or a hydrate thereof. Metal hydroxides, metal silicates such as magnesium silicate and calcium silicate, crystalline aluminosilicates such as zeolites, amorphous aluminosilicates (aluminosilicate is generally sodium silicate, but sodium is It may be replaced with a metal), and other fine powder silicic acid and the like. The adsorbent thus obtained is prepared into a desired shape, and the adsorbed substance is removed by various methods.

[0021]

The adsorbent according to the present invention contains mesoporous silica as an active ingredient, and has a porous structure obtained by firing a composite of active silica and a cationic surfactant, and a porous structure. average pore diameter 10 to 100 angstroms micropores to uniform pore distribution and the BET specific surface area of the mesopore size is 800 m ² / g or more, preferably characterized in that comprises a very large specific surface area that 1000~1500m ² / g is there. Further, the identification of the production history using activated silica as a silica source is a requirement to provide mesoporous silica of 1000 ppm or less having a significantly lower Na content than conventional porous silica,
This physical property functions to exert thermal stability and to exert catalytic performance with little deterioration with time when used as a catalyst carrier. Therefore, it exhibits excellent performance as a catalyst carrier or adsorbent used under conditions involving severe temperature and atmosphere.

A porous structure having an average pore diameter of 10 to 100 Å and a BET specific surface area of 800 m ² / g or more is
It is a requirement to exhibit adsorption characteristics equal to or higher than that of activated carbon. In particular, since the surface of mesoporous silica is lipophilic, it has excellent adsorption ability for organic substances such as benzene, and has a relatively large pore size, which is suitable for the purpose of selectively adsorbing hydrocarbons having 6 or more carbon atoms. In addition, the adsorbent of the present invention can be regenerated by simple heat treatment and can be used repeatedly.
Further, it is stable in a heated state under an oxidizing atmosphere, and since it is white, it can be colored in a desired color.

[0023]

EXAMPLES The present invention will be specifically described below by comparing Examples and Comparative Examples. The mesoporous silica of Sample A used in each example was manufactured by the following method.

Hexadecyltrimethylammonium Cl
7 kg of salt (hereinafter referred to as “HDTMA-Cl”) in water 12
It was put into 0 kg and stirred for 1 hour to dissolve HDTMA-Cl. Then, the dissolved slurry was passed through a column packed with anion exchange resin (“Amberlite IRA-410”) which had been previously made into OH ⁻ type, and HDTMA-at pH 13 was added.
150 kg of OH aqueous solution was recovered. No. 3 sodium silicate (Si
12 kg of O ₂ ; 29.1%, Na ₂ O; 9.45%) was diluted to 120 kg with water and passed through a column packed with a cation exchange resin (“Amberlite IR-120B”) that had been made into H ⁺ type in advance. Then, 125 kg of an aqueous sol containing activated silica was recovered. This activated silica sol had a pH of 3.1 and the Na content in silica was 50 ppm.

Stir the above HDTMA-OH aqueous solution,
The active silica sol was added little by little thereto and the whole amount was mixed. The liquid became cloudy by mixing. The pH of the mixed slurry is
It was 10.2. Then, the mixed slurry was stirred at a temperature of 75 ° C. for 3 hours to cause reaction, and allowed to cool. The pH at this time was 10.2. The slurry is then filtered, 10
After repulping to 0 liter, filter again and 120 ℃
It was dried at the temperature of. When the dry powder was subjected to X-ray diffraction, pattern peaks were shown at 2θ = 2.18 °, 3.74 ° and 4.20 °, and it was confirmed that the powder was a silica / surfactant complex. Then, dry powder 650
The surface-active agent component was burned and removed by baking at 30 ° C. for 30 minutes. As a result of X-ray diffraction of the obtained fired product, 2θ = 2.3
It shows peaks at 4 degrees, 3.92 degrees, 4.12 degrees, and 4.60 degrees, and has an average pore cell diameter of 43.5 angstroms.
In the nitrogen adsorption method, it was confirmed that the skeleton of the mesoporous structure composed of uniform pore cells having an average pore diameter of 38.6 angstrom remained. The BET specific surface area of the fired product was 1400 m ² / g and the Na content was 22 ppm.

Example 1, Comparative Example 1 0.5 g of sample A was placed in the center of a 10-liter Tedlar bag.
The dispersed petri dish (8.5 mm in diameter) was allowed to stand. Atmosphere was introduced into this Tedlar bag, and high concentration acetic acid gas was added at a concentration of 10 pp.
After injecting so as to be m 3, the contaminated air was sampled with time and measured with a gastech detector tube to measure the acetic acid gas concentration at regular intervals. The results are shown in Table 1.
As Comparative Example 1, the same test was performed using powdered activated carbon (manufactured by Sansan Kogyo Co., Ltd.) having a BET specific surface area of 1100 m ² / g,
The results are also shown in Table 1.

[0027]

[Table 1]

Example 2 and Comparative Example 2 All were the same as Example 1 except that the gas to be adsorbed was changed to NO ₂ gas, the atmosphere was introduced into the Tedlar bag, and then the high concentration NO ₂ gas was injected to have a concentration of 17 ppm. And NO
The concentration of ₂ gases was measured over time. The result was similarly measured as Comparative Example 2 powdered activated carbon (the same as Comparative Example 1).
The results are shown in Table 2 in comparison with the results according to.

[0029]

[Table 2]

Example 3 and Comparative Example 3 NO ₂ was carried out in the same manner as in Example 1 except that the gas to be adsorbed was changed to acetaldehyde gas, the atmosphere was introduced into the Tedlar bag, and then acetaldehyde gas was injected so that the concentration became 16 ppm. The gas concentration was measured over time. The results are shown in Table 3 in comparison with those of the powdered activated carbon (the same as in Comparative Example 1) measured in the same manner as Comparative Example 3.

[0031]

[Table 3]

Examples 4 to 6 and Comparative Examples 4 to 9 Sample A was used as an adsorbent, and the gas to be adsorbed was octane gas, benzene gas, and toluene gas. In addition, as a comparison, the results are shown in Table 4 in comparison with the results of similarly measured silica gel (BET specific surface area 300 m ² / g) and powdered activated carbon (same as Comparative Example 1).

[0033]

[Table 4]

Example 7 Adsorbent which adsorbed benzene gas in Example 5 (Sample A)
After heat-regenerating at a temperature of 250 ° C. for 30 minutes, the adsorption property of benzene gas was examined again. As a result, there was no change in the adsorption performance and no deterioration phenomenon was observed. Also, play 2
It was repeated 0 times and was found to have adsorption properties comparable to those before regeneration.

Example 8 Carboxymethylcellulose solution 380 with 0.5% concentration
Parts by weight were added to 100 parts by weight of sample A and kneaded sufficiently.
This kneaded product was extruded into a thin rod shape and dried at 120 ° C for 2 hours using a ventilation drier to have a diameter of 3 mm and a length of 3 to 7 mm.
Cylindrical pellets were prepared. Obtained molded pellet 1
0.4 g was packed into a test column (25 mm diameter). The height of the packed bed at this time was 63 mm. Then, trimethylamine was diluted with air to a concentration of 40 ppm and passed through. Space velocity 2000 / hr, gas flow rate 10
Liter / min, surface wind speed 0.34 m / sec, temperature 20 ° C,
The humidity was set to 50%, and the gas adsorption rate was measured by measuring the inlet and outlet concentrations by the gas detection method. The obtained relationship graph between the elapsed time and the gas adsorption rate is shown in FIG.

[0036]

INDUSTRIAL APPLICABILITY As described above, the adsorbent according to the present invention exhibits an adsorption performance equal to or higher than that of activated carbon which has been widely used in the past. Moreover, the active ingredient, mesoporous silica, is
Since it is a white powder and contains few alkali components, it is excellent in heat stability, oxidation resistance, safety and colorability, and the field of application to which it is applied is remarkably wide compared to activated carbon.

[Brief description of drawings]

FIG. 1 is a graph showing a gas adsorption rate of trimethylamine according to Example 11.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C02F 1/28 A (72) Inventor Tomohiro Banda 9-15-1, Kameido, Koto-ku, Tokyo Japanization Gaku Kogyo Co., Ltd.

Claims (2)

[Claims] 1. A porous structure obtained by firing a composite of active silica and a cationic surfactant, having an average pore size of 10 to 100 angstroms and a BET specific surface area of 80.
An adsorbent characterized by using mesoporous silica having a physical property of 0 m ² / g or more and a Na content of 1000 ppm as an active ingredient. 2. The adsorbent according to claim 1, wherein the mesoporous silica is a powder or a molded body.