JP6707743B2 - Method for manufacturing desiccant - Google Patents

Description

The present invention relates to a method for producing a desiccant.

A desiccant is a substance that absorbs water vapor from the air.

As the performance of the desiccant, the moisture absorption capacity, which represents the mass of water that can absorb moisture, the hygroscopic force, which is the amount of water remaining after the desiccant is made to act, and the moisture absorption rate, which represents the amount of moisture absorbed per unit time, are important.

The desiccant can be reused by heating or reducing the pressure. For reuse, the desorption rate of water molecules absorbed by the desiccant, that is, the regeneration rate is important.

The desiccant is roughly classified into a chemical desiccant and a physical desiccant.

A chemical desiccant is a desiccant that utilizes a chemical reaction or deliquescent. As a chemical desiccant, for example, calcium chloride used in a storage space having a certain volume such as a closet or a closet is known. Calcium chloride becomes an aqueous solution due to deliquescent when it absorbs water. Calcium chloride can be regenerated by evaporating water, but is generally disposable.

The physical desiccant utilizes the property that water molecules are easily adsorbed on the porous surface. Physical desiccants are used, for example, to store a small amount of an object in a completely dry state. Physical desiccants are, for example, silica gel and zeolites. Regeneration of silica gel and zeolite is generally performed at a high temperature of 80°C or higher.

Silica gel is a xerogel obtained by dehydrating a white amorphous gel produced by adding an acid to an alkali silicate solution such as sodium silicate, and drying the gel at 500° C., for example. The composition of silica gel is represented by SiO ₂ .nH ₂ O. There is no compound of a certain amount of water combined with 1 mol of silicon dioxide of silica gel. Silica gel is believed to contain orthosilicic acid (H ₄ SiO ₄ ) and metasilicic acid (H ₂ SiO ₃ ). Regeneration of hygroscopic silica gel requires heat treatment to break the chemical bonds between SiO ₂ and H ₂ O. Silica gel can be regenerated by heat treatment at 80 to 100° C. or heat treatment using a microwave oven.

Zeolites are divided into natural zeolites, artificial zeolites and synthetic zeolites. Natural zeolites are minerals, and artificial zeolites are mainly hydrothermally synthesized from coal ash as a raw material. Synthetic zeolites are also called molecular sieves. The synthetic zeolite is, for example, hydrothermally synthesized from a mixture of silicon, aluminum and an alkaline compound.

However, for example, it is reported that the DTA endothermic peak for desorbing H ₂ O adsorbed on zeolite 4A is 130 to 230°C.

Thus, the conventional desiccant composed of silica gel or zeolite has a relatively high regeneration temperature.

Patent Document 1 describes an adsorbent produced from rice husks as a raw material, which contains a porous aluminosilicate-carbon composite material and adsorbs carbon dioxide gas and water vapor at the same time. However, Patent Document 1 does not consider the use as a desiccant for the purpose of dehumidification, and naturally does not consider regeneration of the desiccant.

Japanese Patent No. 5487483

An object of the present invention is to provide a method for producing a desiccant which has a high moisture absorption rate and can be regenerated at low temperature.

According to the first aspect of the present invention, a step of firing a silicic acid plant in an inert atmosphere at 400° C. or higher to produce a silica-carbon composite, in a molar ratio of Si:Al=1:0.1 to 1. A step of producing a mixture containing the silica-carbon composite, an Al compound, an alkali metal compound or an alkaline earth metal compound and water so that an aluminosilicate in the range of 2 is produced, and the mixture is subjected to a hydrothermal reaction. To obtain a porous aluminosilicate-carbon composite, and to subject the porous aluminosilicate-carbon composite to an inert gas treatment at 600 to 800° C. to obtain a desiccant. A method for producing a desiccant is provided.

According to the present invention, there is provided a method for producing a desiccant which has a high moisture absorption rate and can be regenerated at a low temperature of 40°C or higher.

The graph which shows the result of having absorbed the moisture in a container using the desiccant obtained by the manufacturing method which concerns on this invention. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention once, and absorbed the water|moisture content in a container. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention twice, and absorbed the moisture in a container. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention 3 times, and having absorbed the water|moisture content in a container. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention 4 times, and absorbed the water|moisture content in a container. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention 5 times, and absorbed the moisture in a container. The graph which shows the result of having regenerated the desiccant obtained by the manufacturing method which concerns on this invention 7 times, and absorbed the water|moisture content in a container.

An embodiment of the present invention will be described below.

<Drying agent manufacturing method>
Below, the manufacturing method of the desiccant which concerns on one Embodiment of this invention is demonstrated.

First, a silicic acid plant is prepared as a raw material of a desiccant.
The silicic acid plant is, for example, a grass family plant. Gramineous plants are, for example, rice, wheat, barley, rye, pearl barley, millet, millet, millet, corn and Japanese pampas grass. The silicic acid plants are preferably rice husks and straws having a high silicic acid content, and rice husks are particularly preferable.

Rice husk consists of about 20% by weight of an inorganic component and about 80% by weight of an organic component such as cellulose. Of the about 20% by weight inorganic components, 85 to 95% by weight is active silica (SiO ₂ ).

The silica in the chaff is deposited between the cell walls of the chaff. Silica in rice husks is outside the epidermal cells when water-soluble silicate ions in irrigation water pass through the roots of rice, through the ducts of stems, reach the epidermis, and evaporate water from the epidermis of the rice husks by evaporation. It was deposited on the cuticle. Silica is dispersed in the cuticle, which is an organic substance, and silica and silica are in close proximity (Takeshi Okutani, Material Analysis and Characterization Science, 6, 24-50 (1993)).

It should be noted that the silicic acid plant may remove foreign matters such as stones and soil by wind selection or sieving, if necessary. Further, the silicic acid plant may be leached with dilute hydrochloric acid, for example, to elute and remove iron, an alkali metal compound or an alkaline earth metal compound contained in a minute amount in the inorganic substance.

Hereinafter, as one embodiment of the present invention, it is described that the silicic acid plant is rice husk.

Next, the rice husk is baked at 400° C. or higher in an inert atmosphere to produce a silica-carbon composite. When the rice husks are baked in an inert atmosphere, the organic substances in the rice husks are carbonized to form a silica-carbon composite. The silica-carbon composite is a composite in which silica and carbon are very close to each other, and is also called chaff char or chaff char. The silica and carbon contained in the silica-carbon composite are very fine, homogeneous at the molecular level, and small in distance from each other, as compared with a simple silica-carbon mixture.

The inert atmosphere is, for example, an atmosphere of nitrogen or argon.

The firing temperature is 400°C or higher, preferably in the range of 450 to 1000°C, more preferably in the range of 500 to 1000°C, and further preferably in the range of 500 to 900°C. .. When the firing temperature is lower than 400°C, the rice husks are insufficiently carbonized or it takes a long time to complete the carbonization.

The firing time is preferably several minutes to several tens of hours, more preferably several tens of minutes to several hours. Specifically, it is preferably 10 minutes to 30 hours, more preferably about 30 minutes to 3 hours.

In addition, it is preferable to measure the component of the silica-carbon composite, and it is particularly preferable to measure the silicon content of the silica-carbon composite. When the silicon content of the silica-carbon composite is measured, it is easy to determine the compounding amount of the Al compound, for example, based on the silicon content when the mixture is prepared in the subsequent step. The component of the silica-carbon composite can be measured by, for example, atomic absorption spectrometry. If necessary, the contents of silicon and Al, Na, K, Ca and the like may be measured.

However, if the same rice husk is used as the raw material, the component content of the silica-carbon composite does not change significantly, so the component of the silica-carbon composite is always measured every time the desiccant is manufactured. No need.

Next, a silica-carbon composite, an Al compound, and an alkali metal are produced by a hydrothermal reaction described below so that an aluminosilicate having a molar ratio of Si:Al=1:0.1 to 1.2 is produced. A mixture containing a compound or an alkaline earth metal compound and water is prepared.

The Al compound is, for example, Al(OH) ₃ , NaAlO ₂ and Al ₂ O ₃ , and the Al compound is preferably Al(OH) ₃ .

The alkali metal compound or alkaline earth metal compound is preferably any one of sodium hydroxide, potassium hydroxide and calcium hydroxide, or a mixture of two or more thereof.

The mixture is then hydrothermally reacted.
A hydrothermal reaction of the mixture gives a porous aluminosilicate-carbon composite. In the hydrothermal reaction, the mixture is treated under hot water at high temperature and high pressure. The hydrothermal reaction is performed, for example, in an autoclave.

When the Al compound and the alkali metal compound or the alkaline earth metal compound added to the silica in the silica-carbon composite react with each other by the hydrothermal reaction, a porous aluminosilicate is generated, and the porous aluminosilicate is generated together with carbon that does not participate in the reaction. An acid salt-carbon complex is obtained.

The porous aluminosilicate produced by this reaction is preferably zeolite. The composition of zeolite is represented by the following general formula.
(M ^I , M ^II _1/2 ) _m (Al _m Si _n O _{2 (m+n)} )·xH ₂ O
In the above formula, M ^I and M ^II are alkali metal and alkaline earth metal exchange cations, respectively. M ^I is, for example, Na ⁺ , K ⁺ or Li ⁺ , and M ^II is, for example, Ca ²⁺ , Mg ²⁺ or Ba ²⁺ .

The zeolite is preferably A-type zeolite, X-type zeolite, or Y-type zeolite.

In order to obtain the A-type zeolite, it is desirable to adjust the components within the range of Si:Al:Na=1:0.8 to 1.2:2.5 to 4.0 (molar ratio).

In order to obtain the X-type zeolite, it is desirable to adjust the components within the range of Si:Al:Na=1:0.2 to 0.3:3.5 to 5.0 (molar ratio).

In order to obtain Y-type zeolite, it is desirable to adjust the components within the range of Si:Al:Na=1:0.1 to 0.3:0.8 to 1.0 (molar ratio).

Zeolites are distinguished by their crystalline framework. For example, the zeolite 4A is a Na-A type zeolite having Na ⁺ as an exchange cation and has a unit cell composition (Na ₁₂ [Al ₁₂ Si ₁₂ O ₄₈ ]·27H ₂ O). Its _{crystals, (SiO} ^{4) 4} 4 one around _{^{(AlO 4) 5-, (AlO}} 4) 4 single _(SiO ⁴⁾ around the ^{5-4-organizational} assembled are arranged, equilateral A fourteen-membered tetrahedron (sodalite cage) whose cut ends are cut off from the vertices of the face piece is a four-membered ring, and the four-membered rings of the cut ends are connected to form a three-dimensional skeleton. A cavity surrounded by eight sodalites is formed, and adjacent cavities are connected to each other through six 8-member ring inlets. Since the exchanged cation Na ⁺ exists near the entrance, the pore entrance diameter is 4.1 Å.

Different types of exchange cations have different pore entrance diameters. For example, when the exchange cation is K ⁺ , the pore entrance diameter is about 3Å. When the exchanged cation is divalent Ca ²⁺ , Ca ²⁺ does not exist at the pore entrance, so the pore entrance diameter is about 5 Å (“Zeolite Chemistry and Industry” edited by Yoshio Ono and Kenaki Yashima, Kodansha Scientific). Fick, 2000, ISBN 4-06-153389-4).

Although the van der Waals diameter of H ₂ O is 4.82Å and does not enter the pores of zeolite 4A, H ₂ O of the polar molecule is strongly solidified by the electrostatic action with the exchange cation Na ⁺ at the pore entrance. Adsorbed. It has been reported that the apex of DTA endothermic peak for desorbing H ₂ O adsorbed on zeolite 4A is 130 to 230° C. (Aomura et al., Research Report, Faculty of Engineering, Hokkaido University, 76, 155-162 (1975). ).

The temperature of the hydrothermal reaction is preferably in the range of 50 to 200°C, and particularly preferably in the range of 80 to 120°C. If the temperature is too low, hydrothermal reaction does not occur easily. If the temperature is too high, it may affect the shape and size distribution of zeolite crystals, or zeolite of other crystal system may be produced.

The hydrothermal reaction is preferably carried out within the range of several minutes to several tens of hours, particularly preferably within the range of several tens of minutes to several hours. Specifically, it is preferably 10 minutes to 30 hours, more preferably about 30 minutes to 5 hours.

The produced porous aluminosilicate-carbon composite may be washed with water or the like.

Next, the porous aluminosilicate-carbon composite is subjected to an inert gas treatment at 600 to 800° C. to obtain a desiccant. The temperature of the inert gas treatment is preferably 650 to 750°C.

When the porous aluminosilicate-carbon composite is subjected to an inert gas treatment, the adsorption sites of zeolite and carbon are fused.

The inert gas is preferably, for example, nitrogen or argon, particularly preferably nitrogen.

When inert gas treatment is performed at a temperature lower than 600°C, there are many functional groups such as -COOH and -OH remaining on the surface of activated carbon, and this functional group tends to hinder the fusion of aluminosilicate and activated carbon. large. On the other hand, if the inert gas treatment is performed at a temperature higher than 800°C, the carbonization of the activated carbon proceeds too much and the activated carbon contracts, so that the contact points between the aluminosilicate and the activated carbon decrease, and the fusion tends to decrease. Become.

The desiccant produced by the above-mentioned method reflects the shape of the raw material such as rice husk, and is, for example, granular or flaky. The desiccant may be crushed into granules or powder, if necessary. Appropriate binders such as organic adhesives and inorganic adhesives may be added to the desiccant, placed in a mold, and the binder may be cured to form various shapes. The shape of the desiccant is, for example, a pellet shape, a porous columnar shape, a block shape, a cylindrical shape, a honeycomb shape, or a plate shape. The desiccant can be used, for example, by filling it in a highly breathable container or the like.

According to the method described above, a desiccant which has a high adsorption rate and can be regenerated at low temperature can be obtained. This is considered to be due to the following reasons.

The inert gas treatment causes the aluminosilicate and carbon to coalesce into closer proximity and positions the carbon in close proximity to the adsorption site for the water molecule of exchanged cations near the pore entrance of the aluminosilicate. .. If oxygen in the air is adsorbed to this carbon or there is oxygen remaining in the carbon, as a result of attracting electrons, the electron density at the adsorption site is reduced and the adsorptivity of water molecules is reduced. Therefore, since water molecules are easily desorbed from the adsorption site, the desiccant can be regenerated at a low temperature.

It is also known that the desiccant obtained by the above-described manufacturing method has a low bulk density and is easily exposed to the atmosphere, and thus has a high adsorption rate in the initial stage of adsorption.

<How to absorb and regenerate desiccant>
Hereinafter, a desiccant moisture absorption/regeneration method according to an embodiment of the present invention will be described.

First, moisture absorption is started using the desiccant obtained by the manufacturing method described above, and moisture absorption is stopped before the water adsorption amount reaches saturation. The desiccant obtained by the above-mentioned production method has a higher adsorption rate than the conventional desiccant in the period until the water adsorption amount reaches saturation, but the adsorption rate becomes slower near saturation, so that the desiccant content is high. Take advantage of the characteristics of adsorption rate. In other words, moisture absorption is performed in the range where the high adsorption rate is maintained.
Next, the desiccant is regenerated at a temperature of 40° C. or higher. When the desiccant is regenerated, the water adsorbed on the zeolite is desorbed. As described above, the desiccant according to the present invention can be regenerated in a short time because water molecules that have absorbed moisture are easily desorbed. The regeneration temperature range is 40 to 100°C, but 50 to 90°C is preferable, and 50 to 80°C is more preferable from the viewpoint of low temperature regeneration.

By performing the regeneration time within the range of 15 to 30 minutes, the regeneration temperature can be low and recovery of the adsorption force with low energy can be expected. The regeneration may be performed under atmospheric pressure or under reduced pressure in the range of atmospheric pressure to vacuum.

Next, the moisture absorption and the regeneration described above are repeated at least once or more to absorb the moisture with the desiccant and regenerate the desiccant.

According to the method described above, it is possible to efficiently dehumidify. The desiccant can absorb a large amount of water in a short time. This is because the desiccant produced by the method described above has a high moisture absorption rate. Further, according to the method described above, the desiccant can be regenerated with a small amount of energy. This is because the desiccant produced by the above-mentioned method can be regenerated at low temperature and in a short time because water molecules are easily desorbed. Therefore, it is possible to efficiently dehumidify by repeating the moisture absorption and the regeneration using this desiccant.

According to the method described above, the desiccant can be regenerated to have a high moisture absorption rate. Therefore, it is possible to always absorb moisture in a state where the moisture absorption rate of the desiccant is high, and for example, it is possible to sufficiently and efficiently absorb moisture in the circulating gas.

The method described above can be advantageously applied to the continuous dehumidification of a relatively small volume, substantially enclosed space. Such a space is, for example, a space station. In space stations, desiccants are used to remove water emitted during human activities and to recover water. Due to the limited resources and energy available in the space station, it is advantageous to use desiccants that have high moisture absorption rates and are renewable at low temperatures.

<Drying agent manufacturing system>
Next, a system for manufacturing the above desiccant will be described.

The desiccant production system includes a silica-carbon composite production section, a mixture production section, a porous aluminosilicate-carbon composite production section, and a desiccant production section.

First, in the silica-carbon composite production section, the silica-carbon composite is produced by firing the silicic acid plant in an inert atmosphere at 400° C. or higher.

Next, in the mixture preparation part, in the porous aluminosilicate-carbon composite preparation part described later, aluminosilicate having a molar ratio of Si:Al=1:0.1 to 1.2 is produced. Then, a mixture containing a silica-carbon composite, an Al compound, an alkali metal compound or an alkaline earth metal compound, and water is prepared.

Next, in the porous aluminosilicate-carbon composite preparation section, the mixture is subjected to hydrothermal reaction to obtain a porous aluminosilicate-carbon composite.

Next, in the desiccant manufacturing section, the porous aluminosilicate-carbon composite is subjected to an inert gas treatment at 600 to 800° C. to obtain a desiccant.

In addition, the desiccant manufacturing system may be configured to integrally include a silica-carbon composite preparation part, a mixture preparation part, a porous aluminosilicate-carbon composite preparation part, and a desiccant preparation part, and each part. May be configured in a separated state. In addition, the desiccant manufacturing system may include other functional units as long as they do not hinder the present invention.

The test examples will be described below.
<Production of desiccant A composed of porous aluminosilicate-carbon composite>
First, 25 g of rice husk was washed with distilled water and then dried. The dried rice husk was subjected to reflux treatment (leaching) for 2 hours at 100° C. using 0.5 L of a 3% v/v hydrochloric acid solution. The chaff subjected to reflux was filtered, the chaff was washed until the filtrate had a pH of about 7.0, and vacuum-dried at 80° C. for 1 hour to remove impurities such as potassium from the chaff. The vacuum-dried 12 g of rice husks was treated at 100° C./min of nitrogen flow at 500° C. for 1 hour to obtain a silica-carbon composite (rice husk carbide).

Next, the components of the silica-carbon composite were examined by inductively coupled high frequency plasma spectroscopy. Table 1 shows the components of the silica-carbon composite. In Table 1, LOI (Loss Of Ignition) indicates the loss on ignition. The ignition loss was determined based on the difference between the weight after heating in air at 600° C. for 3 hours and the weight before heating. The component of ignition loss is almost carbon.

Next, add a stirring bar, 4.4 g of NaOH (Wako reagent special grade purity 97%) and 4.4 mL of distilled water to a 300 mL beaker, and use a magnetic stirrer with a heating function (IKA, RH basic 1) to completely remove NaOH. Stir until dissolved. 2.7 g of Al(OH) ₃ (Wako reagent) was added to this beaker, and the mixture was stirred for about 10 minutes until the solution became uniform. When Al(OH) ₃ was difficult to melt, the beaker was heated at a temperature of 100°C or lower.

Next, to this beaker, 35.6 mL of distilled water, 4.12 g of silica-carbon composite (2.0 g as SiO ₂ ) and 0.02 g of synthetic zeolite (A-4 Tosoh product 200 mesh pass) were added, Mix for approximately 20 minutes to obtain a mixture.

Since the molecular weight of SiO ₂ is 60.0, the molecular weight of Al(OH) ₃ is 78.0, and the molecular weight of NaOH is 40.0, the molar ratio of Si:Al:Na is 2.0/60.0:2. 7/78.0:4.4/40.0=1.00:1.04:3.30.

Next, the mixture was put into an approximately 200 mL Teflon (registered trademark) autoclave containing four Teflon (registered trademark) spheres containing an iron core, and the mixture was stirred at 100 reciprocations/min. The temperature was raised to 100° C., and the temperature was maintained at 100° C. for 4 hours to carry out hydrothermal synthesis. After allowing the autoclave to cool to 35°C or lower, the resulting hydrothermal compound was suction filtered and washed with warm water. The hydrothermal compound was washed until the pH of the filtrate became 9 or less, and then dried at 60° C. overnight to obtain a porous aluminosilicate-carbon composite. The aluminosilicate constituting the porous aluminosilicate-carbon composite was zeolite 4A.

When the specific surface area of the porous aluminosilicate-carbon composite was measured by the BET method, the specific surface area was 182 m ² /g. The porous aluminosilicate-carbon composite had a micropore volume of 0.047 mL/g determined by the t-plot method.

The porous aluminosilicate-carbon composite was 57.6 wt% zeolite and 35.6 wt% carbon. The remaining 6.8 wt% excluding zeolite 4A and carbon is considered to be unreacted silica or zeolite that has not been crystallized.

Next, the porous aluminosilicate-carbon composite was subjected to an inert gas treatment in a nitrogen stream at 700° C. for 1 hour to fuse the aluminosilicate and carbon. The specific surface area of the porous aluminosilicate-carbon composite was 199 m ² /g, and the micropore volume was 0.055 mL/g. Thus, the desiccant A of the example was obtained.

<Test Example 1>
A moisture absorption test was conducted using the desiccant A, silica gel and zeolite 4A of the examples. The test method is as follows.

First, 1 g of the desiccant A was put in a container having an internal volume of 2 L, a temperature of 24 to 28° C. and a relative humidity of 62 to 77% RH.

Next, using a temperature/humidity sensor, the time for which the desiccant A was put in the container was set to 0 minutes, and the change in the relative humidity in the container from the time when the desiccant A was put to 60 minutes was measured.

The change in the relative humidity of the container was measured by the same method as described above except that Zeolite 4A or silica gel having a particle size in the range of 2 to 4 mm was used in place of the desiccant A. The results are shown in Fig. 1. The blank is the change in relative humidity in a container without desiccant.

The following can be seen from the results of FIG. The water adsorption amount after 60 minutes was smaller in the desiccant A than in the silica gel, but the adsorption rate up to 30 minutes was larger in the desiccant A than in the silica gel. Although the zeolite amount of the desiccant A is 57.6% by mass, the water adsorption amount is larger than that of the zeolite 4A. As described above, the desiccant A has a larger water adsorption amount than the zeolite 4A and has a higher adsorption rate up to 30 minutes than silica gel.

<Test Example 2>
After the desiccant A, silica gel and zeolite 4A of the example were once regenerated, a moisture absorption test was conducted. The test method is as follows.

First, the desiccant A was exposed to an atmosphere having a temperature of 26° C. and a relative humidity of 96% RH for 36 hours to sufficiently absorb the moisture.

Next, the desiccant A that had been made to absorb moisture was treated under atmospheric pressure at 50° C. for 3 hours to regenerate the desiccant A.

Next, in the same manner as in Test Example 1, the change in relative humidity in the container was measured using the desiccant A that was once regenerated.

Further, in place of the desiccant A, zeolite 4A or silica gel having a particle size in the range of 2 to 4 mm was used, except that these were absorbed and regenerated, and the relative humidity in the container was changed. Was measured. The results are shown in Fig. 2.

The following can be seen from the results of FIG. The desiccant A showed a decrease in relative humidity from 70% to 45% in about 15 minutes, and showed a substantially constant relative humidity at an elapsed time of 15 minutes or more. The relative humidity of Zeolite 4A decreased only 3% after 60 minutes, and it was found in the first moisture absorption test that water was strongly adsorbed to the adsorption site. With silica gel, the relative humidity decreased by 30% after 60 minutes, and the relative humidity was still decreasing. As shown in FIG. 2, desiccant A reached saturation adsorption in 15 minutes, and the adsorption rate up to that time was higher than that of silica gel.

<Test Example 3>
An adsorption test was conducted after the desiccant A, silica gel and zeolite 4A of the example were regenerated twice. The test method is as follows.

First, the desiccant A used in Test Example 2 was treated under atmospheric pressure at 50° C. for 86 hours to regenerate the desiccant A.

Next, in the same manner as in Test Example 1, the change in relative humidity in the container was measured using the desiccant A regenerated twice.

Further, in place of the desiccant A used in Test Example 2, zeolite 4A used in Test Example 2 or silica gel was used in the same manner as above except that the zeolite 4A or silica gel was used to regenerate them in a container. The change in relative humidity was measured. The results are shown in Fig. 3.

The following can be seen from the results of FIG. The second regeneration time was longer than the first regeneration time, but both the desiccant A and the silica gel exhibited almost the same moisture absorption behavior as in FIG. Zeolite 4A showed a decrease in relative humidity of 10%, and the relative humidity became constant in 15 minutes. As shown in FIG. 3, desiccant A reached saturation adsorption in 15 minutes, and the adsorption rate up to that time was higher than that of silica gel.

<Test Example 4>
An adsorption test was conducted after regenerating the desiccant A, silica gel and zeolite 4A of the example three times. The test method is as follows.

First, the desiccant A used in Test Example 3 was treated under atmospheric pressure at 70° C. for 3 hours to regenerate the desiccant A.

Then, in the same manner as in Test Example 1, the change in relative humidity in the container was measured using the desiccant A regenerated three times.

Also, in place of the drying agent A used in Test Example 3, zeolite 4A used in Test Example 3 or silica gel was used in the same manner as described above except that the zeolite 4A or silica gel was used in the container. The change in relative humidity was measured. The results are shown in Fig. 4.

The following can be seen from the results of FIG. As a result of raising the regeneration temperature from 50°C for the first regeneration and 50°C for the second regeneration to 70°C for the third regeneration, the relative humidity is reduced by 27% in Fig. 4, that is, the water adsorption amount is increased, as compared with Fig. 2 and Fig. 3. It was observed. Also in this test, the water adsorption amount was larger in the desiccant A than in the zeolite 4A. As shown in FIG. 4, the desiccant A reached saturation adsorption in 30 minutes, and the adsorption rate up to that time was higher than that of silica gel.

<Test Example 5>
An adsorption test was conducted after the desiccant A, silica gel and zeolite 4A of the example were regenerated four times. The test method is as follows.

First, the desiccant A used in Test Example 4 was treated at 50° C. for 3 hours under a reduced pressure 0.02 to 0.03 MPa lower than the atmospheric pressure to regenerate the desiccant A.

Next, in the same manner as in Test Example 1, the change in relative humidity in the container was measured using the desiccant A regenerated four times.

Also, in place of the drying agent A used in Test Example 4, zeolite 4A or silica gel used in Test Example 4 was used, and these were regenerated by the same method as described above to prepare a container. The change in relative humidity was measured. The result is shown in FIG.

The following can be seen from the results of FIG. When the regeneration treatment was carried out under reduced pressure, neither desiccant A nor silica gel had the effect of increasing the water adsorption amount. On the other hand, as shown in FIG. 5, even when the regeneration treatment was performed under reduced pressure, it was observed that the desiccant A reached saturation adsorption in 15 minutes and the adsorption rate up to that time was higher than that of silica gel. ..

<Test Example 6>
An adsorption test was conducted after the desiccant A, silica gel and zeolite 4A of the example were regenerated five times. The test method is as follows.

First, the desiccant A used in Test Example 5 was treated under atmospheric pressure at 70° C. for 16 hours to regenerate the desiccant A.

Next, in the same manner as in Test Example 1, the change in relative humidity in the container was measured using the desiccant A regenerated five times.

In addition, in place of the desiccant A used in Test Example 5, zeolite 4A or silica gel used in Test Example 5 was used, and these were regenerated by the same method as described above to prepare a container. The change in relative humidity was measured. The result is shown in FIG.

The following can be seen from the results of FIG. When the adsorption test after the third regeneration at the same regeneration temperature of 70°C and the regeneration time of 3 hours (Fig. 4) is compared with the adsorption test after the fifth regeneration at the regeneration time of 16 hours (Fig. 6). The drying agent A showed almost the same behavior, but the difference in relative humidity after 60 minutes was 43% for silica gel, and the effect of time was great. Nevertheless, the adsorption rate up to 15 minutes was greater with desiccant A than with silica gel.

<Test Example 7>
An adsorption test was conducted after the desiccant A of the example was regenerated seven times. The test method is as follows.

First, 1 g of the desiccant A was placed in a container having an internal volume of 2 L, a temperature of 26 to 27° C., and a relative humidity of 60 to 70% RH, and exposed to this atmosphere for 15 minutes to absorb moisture. Next, the desiccant A that had been made to absorb moisture was regenerated by treating it at 80° C. for 15 minutes under atmospheric pressure. By repeating these operations, a desiccant A regenerated seven times was obtained.

Next, using a temperature/humidity sensor, the change in relative humidity in the container was measured from the time when the desiccant A was put into the container to 15 minutes, with the time when the desiccant A regenerated at 7°C was put in the container as 0 minutes. did. The results are shown in Fig. 7.

The following can be seen from the results shown in FIG. The desiccant A, which was regenerated seven times under the condition that it was absorbed for 15 minutes and was regenerated at a regeneration temperature of 80° C. and a regeneration time of 15 minutes, the relative humidity decreased from 65% to 35% in about 10 minutes, and after 15 minutes or more The time showed almost constant relative humidity. Therefore, even when the desiccant A is regenerated under the condition of 80° C. for 15 minutes, it can be regenerated to have a high adsorption rate.

Summarizing the above results, we can conclude as follows.
The desiccant produced by the method of the present invention has an advantage that it has a higher moisture absorption rate than silica gel before the water adsorption amount reaches saturation. Also, the desiccant produced by the method of the present invention could be regenerated when treated at a temperature of 50 to 80°C.
Therefore, by using the desiccant according to the present invention, after starting the moisture absorption, when the water adsorption amount reaches saturation, the moisture absorption is stopped, and the regeneration at the temperature of 40 to 100° C. is repeated, whereby the moisture is efficiently dehumidified. Those skilled in the art can fully understand that it is possible.
The regeneration may be performed under atmospheric pressure or under reduced pressure in the range of atmospheric pressure to vacuum.

Claims (7)

A step of firing a silicic acid plant in an inert atmosphere at 400° C. or higher to produce a silica-carbon composite,
The silica-carbon composite, the Al compound, the alkali metal compound or the alkaline earth metal compound, and water so that an aluminosilicate having a molar ratio of Si:Al=1:0.1 to 1.2 is produced. Producing a mixture comprising and,
A step of subjecting the mixture to a hydrothermal reaction to obtain a porous aluminosilicate-carbon composite, and a drying agent by subjecting the porous aluminosilicate-carbon composite to an inert gas treatment at 600 to 800°C. A method for producing a desiccant, comprising the step of: The method for producing a desiccant according to claim 1, wherein the silicic acid plant is rice hulls or straw. The aluminosilicate constituting the porous aluminosilicate-carbon composite is any one kind of A-type zeolite, X-type zeolite and Y-type zeolite or a mixture of two or more kinds. Item 3. A method for producing a desiccant according to Item 1 or 2. The Al compound is aluminum hydroxide, and the alkali metal compound or the alkaline earth metal compound is any one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide. Item 4. A method for producing a desiccant according to any one of Items 1 to 3. Moisture absorption is started using the desiccant obtained by the manufacturing method as described in any one of Claims 1-4, Moisture absorption is stopped before the amount of water adsorption reaches saturation, and the temperature is 40-100 degreeC. A method for absorbing and regenerating moisture using a desiccant, which comprises repeating regeneration of the desiccant. The moisture absorption/regeneration method using a desiccant according to claim 5, wherein the regeneration is performed under reduced pressure. A silica-carbon composite production section for producing a silica-carbon composite by firing a silicic acid plant in an inert atmosphere at 400° C. or higher;
The silica-carbon composite, the Al compound, the alkali metal compound or the alkaline earth metal compound, and water so that an aluminosilicate having a molar ratio of Si:Al=1:0.1 to 1.2 is produced. A mixture preparation section for preparing a mixture containing and,
A porous aluminosilicate-carbon composite preparation part, which is subjected to hydrothermal reaction on the mixture to obtain a porous aluminosilicate-carbon composite,
A desiccant production system, comprising: a desiccant production section that obtains a desiccant by subjecting the porous aluminosilicate-carbon composite to an inert gas treatment at 600 to 800°C.