JP2009280423A - Aluminum silicate that regularly arranges water molecule, and method for synthesizing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adsorbent comprising aluminum silicate that linearly increases an adsorption amount of water vapor depending on a relative humidity, that has an adsorption-desorption amount of not less than 60 wt.% in a relative humidity range of 5 to 60%, and efficiently adsorbs water vapor on a substance surface by regularly arranging water molecules. <P>SOLUTION: An organic Si and an Al solution barely containing Na and K are used and mixed in a Si/Al ratio of not less than 1.1 upon mixing to form a precursor, which is subjected to centrifugal separation, and the obtained supernatant liquid is heated to synthesize aluminum silicate. The obtained aluminum silicate shows a linear increase in an adsorption amount of water vapor depending on relative humidity, has an adsorption-desorption amount of water vapor of not less than 60 wt.% in a relative humidity range of 5 to 60%, can efficiently adsorb water vapor on a substance surface by regularly arranging water molecules, and can be used as an adsorbent for desiccant air conditioning. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the technical field of nanotechnology, which is expected to be put to practical use as an important basic technology that supports the next generation of industries, the present invention has excellent adsorption capacity due to the fine structure and surface structure resulting from its unique shape. In particular, aluminum silicates that exhibit water physicochemical properties and are expected to be applied as innovative functional materials. It is about.

  Naturally-occurring nano-sized aluminum silicates are produced, for example, as allophane and imogolite. These allophane and imogolite are present in soil and mainly produced in soil derived from volcanic ash. Natural allophane and imogolite affect nutrients and moisture in soil, supply to plants, and accumulation and residue of harmful pollutants. These aluminum silicates are hydrated aluminum silicates whose main constituent elements are silicon (Si), aluminum (Al), oxygen (O) and hydrogen (H) and are assembled with a number of Si-O-Al bonds. Allophane has a nanocapsule-like form with an outer diameter of 3.5 to 5.0 nm, and imogolite has an outer diameter of 2.2 to 2.8 nm, an inner diameter of 0.5 to 1.2 nm, It has a nanotube-like form with a length of 10 nm to several μm.

On the other hand, among amorphous aluminum silicates that do not have a characteristic form, the precursor substance of imogolite is called protoimogolite. This protoimogolite is converted to imogolite when heated in an aqueous solution at about 100 ° C., and is therefore referred to as protomogolite as a precursor material before heating during the imogolite formation process. Protoimogolite has a property derived from the structure of imogolite, and therefore ²⁹ Si solid state NMR shows a peak at −78 ppm, which is the same as imogolite, and silicon has a coordination of OH—Si— (OAl) _3. ing. Therefore, in terms of water vapor adsorption characteristics, imogolite and protomogolite have almost the same adsorption behavior at a relative humidity of 20% or less, and protomogolite has not grown to a relatively long tubular form like crystalline imogolite. However, it is thought that it has the structure of imogolite. Therefore, Protoimogolite also has the same adsorbent properties as imogolite in the low humidity region.

  Such unique shapes and physical properties of allophane and imogolite, which are nanosized aluminum silicates, and protomogolite, which is a precursor of imogolite, are considered to be useful industrially. That is, allophane and imogolite, and also prototomogolite, which is a precursor thereof, have characteristics that can adsorb various substances based on its unique fine structure. Furthermore, the possibility of using it as a gas storage agent such as carbon dioxide or methane has been mentioned conventionally. In addition, since it has excellent water vapor adsorption performance, it is also expected to be used as a heat pump heat exchange material, anti-condensation agent, autonomous humidity control material and the like.

  In particular, as a desiccant air-conditioning adsorbent, it is desirable that the amount of water vapor adsorption increases linearly according to the relative humidity and the amount of water vapor adsorption is large. From such a background, the relationship between the relative humidity and the amount of water vapor adsorption increases linearly, and an inorganic material type adsorbent having a large amount of adsorption has been developed.

Under such circumstances, adsorbents have been developed that have the above characteristics of aluminum silicates such as allophane and imogolite, while the water vapor adsorption amount increases linearly with relative humidity (patents). Reference 1).
However, in the conventional method, when the relative humidity is 5 to 60%, the adsorption amount of the water vapor is linearly increased according to the relative humidity, and the adsorbent is developed by an inorganic material having the water vapor adsorption amount exceeding 60 wt%. There wasn't.
JP 2006-240956 A

For the purpose of developing an adsorbent for desiccant air conditioning, the present inventors have developed an adsorbent in which the amount of water vapor adsorption increases linearly with the relative humidity.
As a result, an inorganic silicon compound and an inorganic aluminum compound are used as raw materials, the synthesis is performed so that the Si / Al ratio is 0.6 to 1, and the water vapor adsorption amount increases linearly according to the relative humidity. (Japanese Patent Application No. 2006-351792), the water vapor adsorption amount was about 35 wt%.
Similarly, when the synthesis was performed with the Si / Al ratio in the range of 1 to 3, a product having a considerable water vapor adsorption amount under a high humidity condition with a relative humidity of 80% or more was obtained (Japanese Patent Application No. 2006-351447), however, water vapor adsorption was hardly performed in the medium humidity region.

  The present invention has been made in view of the circumstances as described above, and the amount of water vapor adsorption increases linearly according to the relative humidity, and the water molecules are regularly arranged on the surface of the material to increase efficiency. An object of the present invention is to provide an adsorbent that adsorbs water vapor.

  As a result of repeated investigations to achieve the above object, the present inventors have used organic materials that do not contain alkali metals such as Na and K, instead of conventional inorganic materials, as Si sources and Al sources. The formed aluminum silicate having a Si / Al ratio of 1.1 or more has a water vapor adsorption amount that increases linearly according to the relative humidity, and a water vapor adsorption amount in the range of 5% to 60% relative humidity. Has been found to have a property of adsorbing water vapor efficiently on the surface of a material by having performance of 60 wt% or more and further arranging water molecules regularly. It has also been found that an aluminum silicic acid having such properties cannot be achieved when synthesized from an inorganic raw material, but can be achieved only when an organic raw material is used.

The present invention has been completed based on these findings, and is as follows.
(1) 2θ = 22.7 °, 26.7 °, 27.9 °, 32.3 when the Si / Al ratio is 1.1 or more and the temperature during powder X-ray diffraction measurement is 70 ° C. or more. It has peaks at °, 35.3 °, 39.8 °, 42.4 °, 46.3 °, and 52.1 °, and 2θ = 15.4 ° is newly added when water vapor is adsorbed at room temperature. 19.3 °, 20.5 °, 23.8 °, 25.5 °, 29.2 °, 30.6 °, 31.4 °, 37.1 °, 37.9 °, 41.6 °, An aluminum silicate characterized by peaks appearing at 43.2 °, 44.7 °, 47.2 °, 47.8 °, 51.0 °, 54.0 ° and 56.9 °.
(2) The aluminum silicate according to (1), wherein the water vapor adsorption amount increases linearly according to the relative humidity, and the adsorption amount at a relative humidity of 5 to 60% is 60 wt% or more.
(3) Using organic raw materials that do not contain sodium and potassium as the Si source and Al source, mixing to form a Si / Al ratio of 1.1 or more to form a precursor, followed by centrifugation to obtain The aluminum silicate according to (1) or (2), which is obtained by heating the obtained supernatant.
(4) An adsorbent comprising the aluminum silicate according to any one of (1) to (3).
(5) A desiccant air-conditioning adsorbent comprising the aluminum silicate of any one of (1) to (3).

  According to the present invention, the water vapor adsorption amount increases linearly according to the relative humidity, and the adsorption amount at a relative humidity of 5 to 60% has a performance of 60 wt% or more, and the water molecules are regularly arranged. It is possible to provide an adsorbent composed of aluminum silicate that efficiently adsorbs water vapor on the surface, and an adsorbent for desiccant air conditioning.

Next, the present invention will be described in more detail.
The aluminum silicate of the present invention is an organic material containing almost no alkali metal such as Na or K as the Si source and Al source, preferably a material having a content of Na or K of 1 ppm or less. Synthesized.
Specifically, a solution comprising an organosilicon compound solution and an organoaluminum compound solution is mixed so that the Si / Al ratio is 1.1 or more, and after the polymerization of silicon and aluminum, the supernatant solution by centrifugation is heated. It can be obtained artificially by aging.

The aluminum silicate in the present invention has the ability to linearly increase the water vapor adsorption amount according to the relative humidity and adsorb water vapor with a water vapor adsorption amount of 60 wt% or more at a relative humidity of 5 to 60%. Judging from the powder X-ray diffraction pattern, it is an aluminum silicate that regularly arranges water molecules when water vapor is adsorbed, and is different from a conventionally known aluminum silicate. It is a highly adsorptive substance.
That is, according to the present invention, by using an organosilicon compound and an organoaluminum compound, the organosilicon compound and the organoaluminum compound are mixed in a Si / Al ratio of 1.1 or more, and the supernatant solution is heated. Provides a substance having an excellent moisture absorption behavior that adsorbs water vapor with a water vapor adsorption amount of 60 wt% or more at a relative humidity of 5 to 60%, which is not obtained by the above method. A possible aluminum silicate is obtained.

  In the present invention, an organosilicon compound and an organoaluminum compound are used as raw materials for the preparation of aluminum silicate. Specifically, the raw material used as the silicon source includes ethyl orthosilicate, and the raw material used as the aluminum source includes aluminum tri-s-butoxide. These silicon sources and aluminum sources are not limited to the above-mentioned compounds, and can be used in the same manner as long as they have the same effect.

These raw materials are dissolved in an aqueous solution to prepare a solution having a predetermined concentration. In order to obtain an aluminum silicate whose water vapor adsorption amount increases linearly according to the relative humidity, it is necessary to mix so that the Si / Al ratio is 1.1 or more. The concentration of the silicon compound in the solution is 1 to 500 mmol / L, and the concentration of the aluminum compound solution is 1 to 450 mmol / L.
Based on these ratios and concentrations, an aluminum compound solution is mixed with an aluminum compound solution to form a precursor, followed by centrifugation. Thereafter, the recovered supernatant is added to ultrapure water as necessary with 3 to 10%. The solid content produced by diluting and heating is the amorphous aluminum silicate in the present invention. In this case, the heating temperature is preferably 90 to 150 ° C., and the time is preferably 2 to 7 days.

EXAMPLES Next, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited at all by the following examples.
(Example)
Ethyl orthosilicate was dissolved so that the Si concentration of a 950 mL aqueous solution containing 75 mmol of perchloric acid was 180 mmol / L, and aluminum tri-s-butoxide was dissolved so that the Al concentration was 150 mmol / L. The stirrer was vigorously stirred for the first 3 hours at room temperature and then continued to stir for 18 hours to form the precursor. The supernatant liquid from which the precipitate was removed by centrifugation was collected and diluted 6-fold with pure water. The diluted solution was transferred to a 500 mL sealed container and heated at 98 ° C. for 4 days in a thermostatic bath to obtain a suspension containing aluminum silicate. When this suspension was dried at 60 ° C., 0.5 g of a solid content per liter was recovered.

The obtained solid content was subjected to powder X-ray diffraction measurement.
FIG. 1 shows a powder X-ray diffraction pattern at the time of water vapor adsorption of the obtained product, and FIG. 2 shows a powder X-ray diffraction pattern in a state where the obtained product is dehydrated at 70 ° C. The powder X-ray diffraction measurement shown in FIG. 2 was performed with the temperature of the sample holder set to 70 ° C.
As can be seen in FIG. 1, 2θ = 15.4 °, 19.3 °, 20.5 °, 22.7 °, 23.8 °, 25.5 °, 26.7 in a state where water vapor is adsorbed. °, 27.9 °, 29.2 °, 30.6 °, 31.4 °, 32.3 °, 35.3 °, 37.1 °, 37.9 °, 39.8 °, 41.6 °, 42.4 °, 43.2 °, 44.7 °, 46.3 °, 47.2 °, 47.8 °, 51.0 °, 52.1 °, 54.0 °, 56.9 Although it has a peak at °, as shown in FIG. 2, 2θ = 22.7 °, 26.7 °, 27.9 °, 32.3 °, 35 when dried at 70 ° C. or higher. Peaks are only seen at 3 °, 39.8 °, 42.4 °, 46.3 °, and 52.1 °, and water molecules are regularly arranged when water vapor is adsorbed. A characteristic phenomenon in which a diffraction peak appears was observed

(Comparative example: Preparation of Protoimogolite)
Protoimogolite was obtained as follows.
After adjusting 200 ml of sodium orthosilicate aqueous solution diluted with pure water so that the Si concentration becomes 60 mmol / L. Separately, aluminum chloride was dissolved in pure water to prepare 200 ml of an aqueous solution having an Al concentration of 150 mmol / L. A sodium orthosilicate aqueous solution was mixed with the aluminum chloride aqueous solution and stirred with a magnetic stirrer. The silicon / aluminum ratio at this time is 0.4. To this mixed solution, 44.8 ml of 1N aqueous sodium hydroxide solution was added dropwise to adjust the pH to 6. The precursor was recovered from this solution by centrifugation, and the precursor was washed twice with pure water by centrifugation, and then dispersed in 2 L of pure water. 10 mL of 1N hydrochloric acid was added to 2 L of this precursor suspension to adjust the pH to 4.2, and the mixture was stirred at room temperature for 1 hour. The solution was concentrated and dried at 60 ° C. for 6 days. The product was obtained.

About the obtained product, the X-ray-diffraction pattern was analyzed.
FIG. 3 shows a powder X-ray diffraction pattern of the product obtained. As can be seen from FIG. 3, the obtained aluminum silicate exhibited an X-ray diffraction pattern indicating that it was amorphous without specific peaks.

(Water vapor adsorption evaluation)
About the aluminum silicate obtained by the Example, and the protoimogolite obtained by the comparative example, water vapor adsorption evaluation was performed from the water vapor adsorption isotherm measured by Belsorp18 made by Nippon Bell Co., Ltd. FIG. 4 shows the result.
As shown in FIG. 4, it was shown that the aluminum silicate obtained in the example has an adsorption / desorption amount of 60 wt% in the range of 5 to 60% relative humidity on the water vapor adsorption isotherm. .

  The aluminum silicate of the present invention has a high performance adsorptivity in which the water vapor adsorption amount increases linearly according to the relative humidity and the water vapor adsorption amount is 60 wt% or more in the range of 5% to 60% relative humidity. It is useful as an adsorbent for desiccant air conditioning.

The figure which shows the powder X-ray-diffraction figure at the time of the water vapor | steam adsorption of an Example. The figure which shows the powder X-ray diffraction pattern at the time of the water vapor | steam desorption of an Example. The figure which shows the powder X-ray-diffraction figure of a comparative example. The figure which shows the result of a water vapor | steam adsorption isotherm about an Example and a comparative example.

Claims (5)

  2θ = 22.7 °, 26.7 °, 27.9 °, 32.3 °, 35 when the Si / Al ratio is 1.1 or more and the temperature during powder X-ray diffraction measurement is 70 ° C. or more. .3 °, 39.8 °, 42.4 °, 46.3 °, 52.1 °, and 2θ = 15.4 °, 19.3 when water vapor is adsorbed at room temperature. °, 20.5 °, 23.8 °, 25.5 °, 29.2 °, 30.6 °, 31.4 °, 37.1 °, 37.9 °, 41.6 °, 43.2 Aluminum silicate characterized by peaks appearing at °, 44.7 °, 47.2 °, 47.8 °, 51.0 °, 54.0 °, 56.9 °.   The aluminum silicate according to claim 1, wherein the water vapor adsorption amount increases linearly according to the relative humidity, and the adsorption amount at 5 to 60% relative humidity is 60 wt% or more.   Using organic raw materials that do not contain sodium and potassium as Si source and Al source, and mixing to form Si / Al ratio of 1.1 or more to form a precursor, followed by centrifugation, the resulting supernatant The aluminum silicate according to claim 1 or 2, wherein the aluminum silicate is obtained by heating the liquid.   The adsorbent which consists of an aluminum silicate of any one of Claims 1-3.   The adsorbent for desiccant air conditioning which consists of aluminum silicate of any one of Claims 1-3.

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