JP5679317B2 - Method for producing volatile organic compound adsorbent - Google Patents

Description

  The present invention relates to a method for producing a volatile organic compound adsorbent.

  In recent years, as companies are becoming more aware of reducing environmental impacts, the regulation of emissions of volatile organic compounds (VOC) has begun with the revision of the Air Pollution Control Act. Gathered. For example, for VOC adsorbents, activated carbon, zeolite, and the like are conventionally used. Since activated carbon has pores of various sizes, almost all VOCs can be adsorbed regardless of the VOC size (see, for example, Patent Document 1). In addition, zeolite has a high heat-resistant temperature, and once adsorbed VOC can be repeatedly desorbed and recovered by heat or pressure (for example, see Patent Document 2).

JP 2008-43846 A Japanese Patent No. 3818508

  However, since the main constituent element of the material described in Patent Document 1 is carbon, there is a risk of oxidation and heat generation due to the accumulation of heat of adsorption, and a lot of cost is spent on safety measures for this. become.

  On the other hand, what is described in Patent Document 2 is a structure in which a general material structure is obtained by replacing a part of a silicon dioxide skeleton with aluminum. When the VOC once adsorbed is desorbed, recovered and repeatedly used, a high temperature treatment of 300 ° C. or higher or a pressure reduction treatment to near vacuum is required, and there is a problem that much energy is required for regeneration.

  An object of the present invention is to provide an efficient method for producing a volatile organic compound adsorbent having excellent gas adsorbing ability and capable of desorption without heating once adsorbed VOC.

As a result of intensive studies to achieve the above object, the present inventors have found that an aluminum silicate having a high adsorbing ability for volatile organic compounds can be obtained with excellent productivity by a specific production method. Got.
The present invention has been completed based on these findings, and according to the present invention, the following inventions are provided.

<1> (a) A solution containing silicate ions (hereinafter also referred to as “silicic acid solution”) and a solution containing aluminum ions (hereinafter also referred to as “aluminum solution”) are used. A step of obtaining a reaction product by mixing Al in a molar ratio of 0.4 to 0.6, (b) a step of desalting and solid-separating the reaction product, and (c) the step (D) a step of subjecting the solid separated in (b) to a heat treatment in an aqueous medium in the presence of an acid under a concentration condition in which the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more; A method for producing a volatile organic compound adsorbent comprising: desalting and solid-separating the product obtained by heat treatment in the step (c).
<2> (a) A solution containing silicate ions and a solution containing aluminum ions are mixed so that the ratio Si / Al of silicon atoms to aluminum atoms is 0.4 to 0.6 in terms of molar ratio. Obtaining a product;
(B) a step of desalting and solid-separating the reaction product;
(C) A step of subjecting the solid separated in the step (b) to a heat treatment in an aqueous medium in the presence of an acid under a concentration condition in which the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. When,
(D) A method for producing a volatile organic compound adsorbent, comprising: desalting and solid-separating the product obtained by heat treatment in the step (c) at a pH of 8 to 10.

<3> In the step (c), the pH is adjusted to 3 or more and less than 7, and the heat treatment is performed at a temperature of 80 ° C. to 160 ° C. for 96 hours or less. The manufacturing method of volatile organic compound adsorption agent of description.

<4> the step (a), the silicon atom concentration of the solution containing the silicate ions is not less 100 mmol / L or more, as an aluminum atom concentration of the solution containing the aluminum ions is 100 mmol / L or more, the The method for producing a volatile organic compound adsorbent according to <2> or <3>, which is a step of mixing a solution containing silicate ions and a solution containing aluminum ions.

<5> (a) A solution containing silicate ions and a solution containing aluminum ions are mixed so that the ratio Si / Al of silicon atoms to aluminum atoms is 0.4 to 0.6 in terms of molar ratio. Obtaining a product;
(B) a step of desalting and solid-separating the reaction product;
(C) Concentration conditions in which the solid separated in the step (b) is in an aqueous medium in the presence of an acid and has a pH of 3 to 5 and a silicon atom concentration of 100 mmol / L or more and an aluminum atom concentration of 100 mmol / L or more. A step of heat-treating with,
(D) A method for producing a volatile organic compound adsorbent, comprising: desalting and solid-separating the product obtained by the heat treatment in the step (c).
<6> The solid separated in the step (b) has an electric conductivity of 4.0 S / m or less when dispersed in water so that the weight concentration is 60 g / kg, <1> The manufacturing method of the volatile organic compound adsorption agent of any one of <5>.
<7> The step (b) includes a step of dispersing the reaction product in an aqueous medium to obtain a dispersion, a step of adjusting the pH of the dispersion to 5 to 7 to precipitate a reaction product, The manufacturing method of the volatile organic compound adsorbent of any one of said <1>-<6> containing.

< 8 > The volatile organic compound adsorbent has a BET specific surface area of 250 m ² / g or more, a total pore volume of 0.1 cm ³ / g or more, and an average pore diameter of 1.5 nm or more. The volatile organic material according to any one of the above items <1> to < 7 >, wherein the powder X-ray diffraction spectrum by CuKα ray has a peak at around 2θ = 26.9 ° and around 40.3 °. A method for producing a compound adsorbent.

<8> A volatile organic compound adsorbent produced by the method for producing a volatile organic compound adsorbent according to any one of <1> to < 8 >.

  ADVANTAGE OF THE INVENTION According to this invention, it can provide the efficient manufacturing method of the volatile organic compound adsorbent which has the outstanding gas adsorption ability and can remove | desorb without heating VOC once adsorbed.

2 is a diagram showing an example of a methanol adsorption / desorption isotherm of sample A obtained in Example 1. FIG. It is a figure which shows an example of the methanol adsorption-desorption isotherm of the sample B obtained by the reference example. 4 is a diagram showing an example of a methanol adsorption / desorption isotherm of a sample C obtained in Comparative Example 1. FIG. It is a figure which shows an example of the adsorption isotherm of the sample B obtained by the reference example. 6 is a diagram illustrating an example of an adsorption isotherm of a sample C obtained in Comparative Example 1. FIG.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. .
In the present specification, numerical ranges indicated using “to” indicate ranges including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.
Furthermore, the weight concentration of the solid separated in this specification is based on the mass of the solid obtained by drying the solid separated at 110 ° C. for 24 hours.

<Method for producing volatile organic compound adsorbent>
The method for producing a volatile organic compound adsorbent of the present invention comprises (a) a step of mixing a solution containing silicate ions and a solution containing aluminum ions to obtain a reaction product, and (b) the reaction product, A step of desalting and separating the solid; and (c) the solid separated in the step (b) in an aqueous medium in the presence of an acid, the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. And (d) a step of desalting and solid-separating the product obtained by the heat treatment in the step (c), and other steps as necessary. It is comprised.

By carrying out heat treatment in the presence of an acid at a much higher concentration than before, it has excellent adsorption capacity for volatile organic compounds (VOC) and has a desorption temperature of 150 ° C. or less. A volatile organic compound adsorbent (hereinafter also referred to as a “VOC adsorbent”) that can be regenerated with a high productivity can be produced.
The VOC adsorbent produced by the production method of the present invention has an excellent VOC adsorption / desorption ability. This can be considered as follows, for example. In general, when a heat treatment in the presence of an aluminum silicate acid is carried out with a dilute solution, a tubular aluminum silicate having a continuous regular structure is formed. However, under high concentration conditions such as the production method of the present invention, it is considered that an aluminum silicate having a clay structure and an amorphous structure in addition to a regular partial structure is formed. It is thought that the excellent VOC adsorption / desorption ability can be exhibited when the aluminum silicate constituting the VOC adsorbent has such various structures.

(A) Step of obtaining a reaction product In the step of obtaining a reaction product, a solution containing silicate ions and a solution containing aluminum ions are mixed to mix aluminum silicate as a reaction product and coexisting ions. Obtain a solution.

(Silicate ion and aluminum ion)
When synthesizing aluminum silicate, silicate ions and aluminum ions are required as raw materials. The silicic acid source constituting the solution containing silicate ions is not particularly limited as long as silicate ions are generated when solvated. Examples thereof include, but are not limited to, tetraalkoxysilanes such as sodium orthosilicate, sodium metasilicate, and tetraethoxysilane.
Moreover, the aluminum source which comprises the solution containing an aluminum ion will not be restrict | limited especially if an aluminum ion produces | generates when it solvates. Examples thereof include, but are not limited to, aluminum chloride, aluminum perchlorate, aluminum nitrate, and aluminum sec-butoxide.

  As the solvent, those which can easily be solvated with the silicate source and the aluminum source which are raw materials can be appropriately selected and used. Specifically, water, ethanol or the like can be used. It is preferable to use water from the viewpoint of reducing the coexisting ions in the solution during the heat treatment and ease of handling.

(Mixing ratio and solution concentration)
These raw materials are dissolved in a solvent to prepare raw material solutions (silicic acid solution and aluminum solution), and then the raw material solutions are mixed with each other to obtain a mixed solution. The Si / Al molar ratio in the mixed solution can be adjusted to an arbitrary value. Among these, from the viewpoint of VOC adsorption / desorption ability, the Si / Al molar ratio is preferably 0.3 to 1.0, more preferably 0.4 to 0.6, and 0.45 to 0.55. More preferably it is.
By setting the Si / Al molar ratio to 0.4 to 1.0, an aluminum silicate having a desired structure can be easily synthesized.
In addition, when mixing the raw material solutions, it is preferable to gradually add the silicic acid solution to the aluminum solution. By doing in this way, the polymerization of silicic acid which can become a formation inhibition factor of desired aluminum silicate can be suppressed.

The silicon atom concentration of the silicic acid solution is not particularly limited, but is preferably 100 mmol / L to 1000 mmol / L.
When the silicon atom concentration of the silicate solution is 100 mmol / L or more, productivity is improved and aluminum silicate can be produced efficiently. Further, when the silicon atom concentration is 1000 mmol / L or less, the productivity is further improved according to the silicon atom concentration.

The aluminum atom concentration of the aluminum solution is not particularly limited, but is preferably 100 mmol / L to 1000 mmol / L.
When the aluminum atom concentration of the aluminum solution is 100 mmol / L or more, productivity is improved, and aluminum silicate can be produced efficiently. Further, when the aluminum atom concentration is 1000 mmol / L or less, the productivity is further improved according to the aluminum atom concentration.

(B) First washing step (desalting and solid separation)
A solution containing silicate ions and a solution containing aluminum ions are mixed to produce an aluminum silicate containing coexisting ions as a reaction product, and then the aluminum silicate containing the produced coexisting ions is desalted and A first washing step for solid separation is performed. In the first washing step, at least a part of the coexisting ions is removed from the mixed solution to reduce the coexisting ion concentration in the mixed solution. By performing the first cleaning step, it becomes easy to form a desired aluminum silicate in the synthesis step.

  In the first washing step, desalting and solid separation include anions other than silicate ions derived from a silicate source and an aluminum source (eg, chloride ions and nitrate ions) and cations other than aluminum ions (eg, sodium ions). There is no particular limitation as long as at least a part of the solution can be removed (desalted) to separate the solid. Examples of the first washing step include a method using centrifugation, a method using a dialysis membrane, and a method using an ion exchange resin.

The first washing step is preferably performed so that the concentration of coexisting ions is not more than a predetermined concentration. Specifically, for example, when the solid separated product obtained in the first washing step is dispersed in pure water so that the weight concentration is 60 g / kg, the electrical conductivity of the dispersion is 4.0 S / m or less, preferably 1.0 mS / m or more and 3.0 S / m or less, more preferably 1.0 mS / m or more and 2.0 S / m or less. More preferably.
When the electrical conductivity of the dispersion is 4.0 S / m or less, the desired aluminum silicate tends to be more easily formed in the synthesis step.
In addition, electrical conductivity is measured at normal temperature (25 degreeC) using the product made by HORIBA: F-55 and the company's general electrical conductivity cell: 9382-10D.

The first washing step preferably includes a step of obtaining a dispersion by dispersing the reaction product in an aqueous medium, and a step of precipitating the reaction product by adjusting the pH of the dispersion to 5 to 7. .
For example, when performing a 1st washing | cleaning process using centrifugation, it can carry out as follows. The pH is adjusted to 5-7 by adding alkali or the like to the mixed solution. After centrifuging the pH-adjusted solution, the supernatant solution is discharged and the solid is separated as a gel-like precipitate. The separated solid is redispersed in a solvent. In that case, it is preferable to return to the volume before centrifugation. The concentration of the coexisting ions can be reduced to a predetermined concentration or less by repeating the operations of desalting and solid separation by centrifugal separation of the redispersed dispersion in the same manner.
In the first washing step, the pH is adjusted to 5 to 7, for example, but preferably 5.5 to 6.8, and more preferably 5.8 to 6.5.
The alkali used for pH adjustment is not particularly limited. For example, sodium hydroxide and ammonia are preferable.
Centrifugation conditions are appropriately selected according to the production scale, the container used, and the like. For example, it can be 1 to 30 minutes at 1200 G or more at room temperature. Specifically, for example, when TOMY made by TOMY: Suprema23 and the company's standard rotor NA-16 are used as the centrifuge, the temperature can be set at 3000 rpm (1450 G) or more for 5 to 10 minutes at room temperature.

  As the solvent in the first washing step, a solvent that can easily be solvated with the raw material can be appropriately selected and used. Specifically, water, ethanol, or the like can be used. It should be noted that pH adjustment is preferably omitted when repeated washing is performed a plurality of times.

  The number of treatments for desalting and solid separation in the first washing step may be appropriately set according to the remaining amount of coexisting ions. For example, it can be 1 to 6 times. If the washing is repeated about three times, the residual amount of coexisting ions is reduced to such an extent that does not affect the synthesis of the desired aluminum silicate.

  The pH at the time of pH adjustment can be measured by a pH meter using a general glass electrode. Specifically, for example, trade name: MODEL (F-51) manufactured by HORIBA, Ltd. can be used.

(C) Synthesis step In the synthesis step, the concentration of the solid separated in the first washing step in an aqueous medium in the presence of an acid is such that the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. Heat treatment is performed at
In the conventional manufacturing method, aluminum silicate is grown in a tubular shape by performing heat treatment with a dilute solution. In such a conventional manufacturing method, there is a limit to improvement in productivity because the heat treatment is performed with a dilute solution. However, an aluminum silicate having excellent VOC adsorption / desorption capability and having a structure different from that of a tube by performing a heat treatment under conditions where the concentration of silicon atoms and aluminum atoms is not less than a specific concentration as in the production method of the present invention. Can be manufactured with high productivity.

After the first washing step, the silicon atom in the silicic acid component and the aluminum atom in the aluminum component contained in the separated solid are adjusted so as to have a predetermined concentration.
In the present invention, the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. Preferably, the silicon atom concentration is 120 mmol / L or more and 2000 mmol / L or less and the aluminum atom concentration is 120 mmol / L or more and 2000 mmol / L or less, more preferably the silicon atom concentration is 150 mmol / L or more and 1500 mmol / L or less and the aluminum atom concentration is 150 mmol / L or more and 1500 mmol / L or less.
When the silicon atom concentration is less than 100 mmol / L or the aluminum atom concentration is less than 100 mmol / L, it may be difficult to obtain a desired aluminum silicate. Also, the productivity of aluminum silicate tends to decrease

The silicon atom concentration and the aluminum atom concentration are the silicon atom concentration and the aluminum atom concentration after adjusting the pH to a predetermined range by adding an acidic compound described later.
The silicon atom concentration and the aluminum atom concentration are measured by an ordinary method using an ICP emission spectrometer (for example, ICP emission spectrometer: P-4010 manufactured by Hitachi, Ltd.).

  A solvent may be added when adjusting the silicon atom concentration and the aluminum atom concentration to be a predetermined concentration. As the solvent, one that can easily be solvated with the raw material can be appropriately selected and used. Specifically, water, ethanol, etc. can be used, but the coexisting ions in the solution during the heat treatment can be reduced. In view of ease of handling, it is preferable to use water.

  In the synthesis step, at least one acidic compound is added before the heat treatment. The pH after adding the acidic compound is not particularly limited. From the viewpoint of efficiently obtaining the desired aluminum silicate, the pH is preferably from 3 to less than 7, and more preferably from 3 to 5.

  The acidic compound added in the synthesis step is not particularly limited, and may be an organic acid or an inorganic acid. Among these, it is preferable to use an inorganic acid. Specific examples of the inorganic acid include hydrochloric acid, perchloric acid, and nitric acid. Considering reduction of coexisting ion species in the solution during the heat treatment, it is preferable to use an acidic compound that generates an anion similar to the anion contained in the used aluminum source.

After adding an acidic compound, the aluminum silicate which has a desired structure can be obtained by heat-processing.
The heating temperature is not particularly limited. From the viewpoint of efficiently obtaining the desired aluminum silicate, it is preferably 80 ° C to 160 ° C.
There exists a tendency which can suppress that boehmite (aluminum hydroxide) precipitates that heating temperature is 160 degrees C or less. When the heating temperature is 80 ° C. or higher, the synthesis rate of the desired aluminum silicate is improved, and the desired aluminum silicate tends to be produced more efficiently.

The heating time is not particularly limited. From the viewpoint of more efficiently obtaining an aluminum silicate having a desired structure, it is preferably within 96 hours (4 days).
When the heating time is 96 hours or less, the desired aluminum silicate can be produced more efficiently.

(D) Second washing step (desalting and solid separation)
What was obtained by heat treatment in the synthesis step is desalted and separated into solids in the second washing step. Thereby, a volatile organic compound adsorbent having excellent VOC adsorption ability can be obtained. This can be considered as follows, for example. In other words, in the synthesis process, the product obtained by heat treatment may have an aluminum silicate adsorption site clogged with coexisting ions, and the expected VOC adsorption ability may not be obtained. Therefore, a volatile organic compound adsorbent having an excellent VOC adsorption ability is obtained by desalting and solid separation by a second washing step that removes at least a part of coexisting ions from the aluminum silicate obtained in the synthesis step. You can think that you can get.

The second washing step only needs to be able to remove at least a part of anions other than silicate ions and cations other than aluminum ions, and may be the same operation as the first washing step before the synthesis step or a different operation. Good.
The second washing step is preferably performed so that the concentration of coexisting ions is not more than a predetermined concentration. Specifically, for example, when the solid separated product obtained in the second washing step is dispersed in pure water so as to have a weight concentration of 60 g / kg, the electrical conductivity of the dispersion is 4.0 S / m or less, preferably 1.0 mS / m or more and 3.0 S / m or less, more preferably 1.0 mS / m or more and 2.0 S / m or less. More preferably.
When the electrical conductivity of the dispersion is 4.0 S / m or less, it tends to be easy to obtain a volatile organic compound adsorbent having better VOC adsorption ability.

When performing a 2nd washing | cleaning process using centrifugation, it can carry out as follows, for example. The pH is adjusted to 5 to 10 by adding alkali or the like to the mixed solution. After centrifuging the pH-adjusted solution, the supernatant solution is discharged and the solid is separated as a gel-like precipitate. The separated solid is redispersed in a solvent. In that case, it is preferable to return to the volume before centrifugation. The concentration of the coexisting ions can be reduced to a predetermined concentration or less by repeating the operations of desalting and solid separation by centrifugal separation of the redispersed dispersion in the same manner.
In the second washing step, the pH is adjusted to 5 to 10, for example, and preferably 8 to 10.
The alkali used for pH adjustment is not particularly limited. For example, sodium hydroxide and ammonia are preferable.
Centrifugation conditions are appropriately selected according to the production scale, the container used, and the like. For example, it can be 1 to 30 minutes at 1200 G or more at room temperature. Specifically, for example, when TOMY made by TOMY: Suprema23 and the company's standard rotor NA-16 are used as the centrifuge, the temperature can be set at 3000 rpm (1450 G) or more for 5 to 10 minutes at room temperature.

  As a solvent in the second washing step, a solvent that can easily be solvated with the raw material can be appropriately selected and used. Specifically, water, ethanol, or the like can be used. From the viewpoint of ease of handling, it is preferable to use water, and it is more preferable to use pure water. It should be noted that pH adjustment is preferably omitted when repeated washing is performed a plurality of times.

  The number of treatments for desalting and solid separation in the second washing step may be set according to the residual amount of coexisting ions, but is preferably 1 to 6 times, and when the washing is repeated about 3 times, The residual amount of coexisting ions is sufficiently reduced.

About the dispersion liquid after a 2nd washing | cleaning process, it is preferable that especially the density | concentration of the chloride ion and sodium ion which affect the adsorption capacity of a volatile organic compound adsorption agent is reduced among the remaining coexisting ions. That is, the volatile organic compound adsorbent after washing in the second washing step is prepared by dispersing the volatile organic compound adsorbent in water to prepare an aqueous dispersion having a concentration of 400 mg / L. It is preferable to give an object ion concentration of 100 mg / L or less and a sodium ion concentration of 100 mg / L or less. When the chloride ion concentration is 100 mg / L or less and the sodium ion concentration is 100 mg / L or less, the adsorption ability can be further improved. The chloride ion concentration is more preferably 50 mg / L or less, and still more preferably 10 mg / L or less. The sodium ion concentration is more preferably 50 mg / L or less, and still more preferably 10 mg / L or less. Chloride ion concentration and sodium ion concentration can be adjusted according to the number of treatments in the washing step and the type of alkali used for pH adjustment.
The chloride ion concentration and sodium ion concentration are measured under normal conditions by ion chromatography (for example, DX-320 and DX-100 manufactured by Dionex).
The concentration of the dispersion of the volatile organic compound adsorbent is based on the mass of the solid obtained by drying the solid separated material at 110 ° C. for 24 hours.

  The “dispersion after the second washing step” described here means a dispersion in which the volume is returned to the volume before the second washing step after the second washing step by using a solvent. To do. As the solvent to be used, a solvent that can easily be solvated with the raw material can be appropriately selected and used. Specifically, water, ethanol, or the like can be used, but residual coexisting ions in the volatile organic compound adsorbent It is preferable to use water from the viewpoint of reduction of the amount and ease of handling.

The volatile organic compound adsorbent produced by the production method of the present invention preferably has a Si / Al molar ratio of 0.3 to 1.0 from the viewpoint of improving VOC adsorption capacity, and 0.4 to 0. .6, more preferably 0.45 to 0.55.
The Si / Al molar ratio can be adjusted by appropriately selecting the mixing ratio of the raw material solutions.
The Si / Al molar ratio can be measured by an ordinary method using an ICP emission spectrometer (for example, ICP emission spectrometer: P-4010 manufactured by Hitachi, Ltd.).

The BET specific surface area of the volatile organic compound adsorbent produced by the production method of the present invention is not particularly limited. From the viewpoint of improving adsorbability of the VOC is preferably a BET specific surface area of 200 meters ² / g or more, more preferably 250 meters ² / g or more, more preferably 280 meters ² / g or more.

The BET specific surface area of the volatile organic compound adsorbent is measured from the nitrogen adsorption capacity according to JIS Z 8830. As an evaluation apparatus, QUANTACHROME make: AUTOSORB-1 (brand name) etc. can be used, for example. When measuring the BET specific surface area, it is considered that the moisture adsorbed on the sample surface and structure affects the gas adsorption capacity. Therefore, pretreatment for removing moisture by heating is first performed.
In the pretreatment, the measurement cell charged with 0.05 g of the measurement sample is depressurized to 10 Pa or less with a vacuum pump, heated at 110 ° C., held for 3 hours or more, and kept at a normal temperature while maintaining the depressurized state. Cool naturally to (25 ° C). After performing this pretreatment, the evaluation temperature is 77K, and the evaluation pressure range is measured as a relative pressure (equilibrium pressure with respect to saturated vapor pressure) of less than 1.

  The BET specific surface area is determined by the treatment method of the second washing step (for example, aluminum added to the synthesis solution to adjust the pH to 5 to 10, centrifuged, and then the supernatant solution was discharged to leave the gel-like precipitate) The process of redispersing the silicate in the solvent and returning it to the volume before the centrifugation is repeated once or a plurality of times.

Moreover, the total pore volume of the volatile organic compound adsorbent produced by the production method of the present invention is not particularly limited. From the viewpoint of VOC adsorption capacity, preferably at 0.1 cm ³ / g or more, more preferably 0.12 cm ³ / g or more, more preferably 0.15 cm ³ / g or more.
Based on the BET specific surface area, the total pore volume of the volatile organic compound adsorbent is the amount of gas adsorbed closest to the relative pressure 1 in the data obtained when the relative pressure is in the range of 0.95 to less than 1. Calculate by converting to

  The total pore volume was treated as a second washing step (for example, an alkali was added to the synthesis solution to adjust the pH to 5 to 10, and after centrifugation, the supernatant solution was discharged and remained as a gel-like precipitate) The process of redispersing the aluminum silicate in the solvent and returning it to the volume before centrifugation can be adjusted by repeating the process once or several times.

Moreover, the average pore diameter of the volatile organic compound adsorbent produced by the production method of the present invention is not particularly limited. From the viewpoint of VOC adsorption capacity, the average pore diameter is preferably 1.5 nm or more, more preferably 1.7 nm or more, and further preferably 2.0 nm or more.
The average pore diameter of the volatile organic compound adsorbent is determined on the basis of the BET specific surface area and the total pore volume, assuming that all the pores are composed of one cylindrical pore.

  The average pore diameter was determined by treating the second washing step (for example, adding alkali to the synthesis solution to adjust the pH to 5-10, centrifuging, then discharging the supernatant solution and remaining as a gel-like precipitate) The process of redispersing the aluminum silicate in the solvent and returning it to the volume before centrifugation can be adjusted by repeating the process once or several times.

Further, the volatile organic compound adsorbent preferably has peaks at 2θ = 26.9 ° and around 40.3 ° in a powder X-ray diffraction spectrum by CuKα rays. These peaks are estimated as peaks corresponding to the amorphous component of aluminum silicate, and are observed as broad peaks.
Further, the volatile organic compound adsorbent has peaks in the powder X-ray diffraction spectrum around 2θ = 18.8 °, around 20.3 °, around 27.8 °, around 40.6 ° and around 53.3 °. It is preferable to have each. These peaks are estimated corresponding to aluminum hydroxide (bayerite) and are observed as sharp peaks.
The powder X-ray diffraction spectrum is measured using, for example, Geigerflex RAD-2X (trade name) manufactured by Rigaku Corporation as a powder X-ray diffractometer and using CuKα rays as an X-ray source.

  The volatile organic compound adsorbent is produced by the above production method, and is useful as an adsorbent for volatile organic compounds. More specifically, a honeycomb-shaped substrate or a porous substrate having air permeability is coated with a volatile organic compound adsorbent and used as a filter, or a volatile organic compound adsorbent on the surface of a granular or spherical substrate. Can be used by filling the base material in a container and molding the volatile organic compound adsorbent itself. In addition, the base material mentioned above is not specifically limited, Natural materials, such as a metal, a ceramic, a synthetic resin hardened | cured material, wood, etc. can be used.

  Next, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

<Example 1>
(A) Step of obtaining reaction product Concentration: 350 mmol / L sodium orthosilicate aqueous solution (500 mL) was added to 700 mmol / L aluminum chloride aqueous solution (500 mL), and the mixture was stirred for 30 minutes. To this solution, 330 mL of an aqueous sodium hydroxide solution having a concentration of 1 mol / L was added to adjust the pH to 6.1.

(B) First washing step After the pH-adjusted solution is stirred for 30 minutes, centrifugal separation is performed for 5 minutes at a rotational speed of 3,000 rpm using a TOMY Corporation: Superma23 and standard rotor NA-16 as a centrifugal separator. Separation was performed. After centrifugation, the supernatant solution was discharged, the gel precipitate was redispersed in pure water, and returned to the volume before centrifugation. Such desalting treatment by centrifugation was performed three times.

  The gel-like precipitate after the third desalting treatment was dispersed in pure water so that the weight concentration was 60 g / kg, using HORIBA: F-55 and conductivity cell: 9382-10D, It was 1.3 S / m when electrical conductivity was measured at normal temperature (25 degreeC).

(C) Synthesis step 135 mL of hydrochloric acid having a concentration of 1 mol / L was added to the gel-like precipitate obtained after discharging the supernatant in the third desalting treatment, and the pH was adjusted to 3.5, followed by stirring for 30 minutes.
When the silicon atom concentration and the aluminum atom concentration in the solution at this time were measured by an ordinary method using an ICP emission spectrometer: P-4010 (manufactured by Hitachi, Ltd.), the silicon atom concentration was 213 mmol / L, The aluminum atom concentration was 426 mmol / L.
The solution was then placed in a dryer and heated at 98 ° C. for 48 hours (2 days).

(D) Second washing step 188 mL of a 1 mol / L sodium hydroxide aqueous solution was added to the heated solution (aluminum silicate concentration 47 g / L) to adjust the pH to 9.1. The aluminum silicate in the solution was aggregated by adjusting the pH, and the aggregate was precipitated by the same centrifugal separation as in the first washing step, whereby the supernatant was discharged. The desalting process of adding pure water to this and returning to the volume before centrifugation was performed 3 times.

  The gel-like precipitate after the third desalting treatment was dispersed in pure water so that the weight concentration was 60 g / kg, using HORIBA: F-55 and conductivity cell: 9382-10D, It was 0.6 S / m when electrical conductivity was measured at normal temperature (25 degreeC).

  The gel-like precipitate obtained after the third desalting of the desalting treatment was dried at 60 ° C. for 16 hours to obtain 30 g of powder. The obtained powder was designated as Sample A.

<Evaluation>
(Structural evaluation)
The structural evaluation of Sample A was performed by BET specific surface area, total pore volume, average pore diameter, and powder X-ray diffraction.

BET specific surface area, total pore volume, and average pore diameter were analyzed from measurements of nitrogen adsorption isotherms. For the evaluation apparatus, QUANTACHROME: AUTOSORB-1 (trade name) was used. When measuring the BET specific surface area, after pretreatment of the sample described later, the evaluation temperature is 77K, and the evaluation pressure range is less than 1 in relative pressure (equilibrium pressure with respect to saturated vapor pressure).
Further, powder X-ray diffraction was performed using Rigaku Corporation: Geigerflex RAD-2X (trade name) and CuKα rays as an X-ray source.

Here, in the evaluation of the BET specific surface area, the total pore volume, and the average pore diameter, the moisture adsorbed on the sample surface and the structure is considered to affect the gas adsorption capacity. Pre-treatment for removal was performed.
In this example, the sample A was pretreated by performing automatic degassing and heating with a vacuum pump into a measurement cell charged with 0.05 g of sample A. The detailed conditions of this treatment were set such that the pressure was reduced to 10 Pa or less, heated at 110 ° C., held for 3 hours or more, and then naturally cooled to room temperature (25 ° C.) while maintaining the reduced pressure.

As a result of the evaluation, the BET specific surface area of Sample A was 363 m ² / g, the total pore volume was 0.22 cm ³ / g, and the average pore diameter was 2.4 nm.
In the powder X-ray diffraction spectrum of Sample A, broad peaks were observed at 2θ = 26.9 ° and 40.3 °. Furthermore, sharp peaks were observed at 2θ = 18.8 °, 20.3 °, 27.8 °, 40.6 °, and 53.3 °.

(VOC adsorption / desorption ability evaluation)
BELSORP-18 (trade name) manufactured by Nippon Bell Co., Ltd. was used for VOC adsorption / desorption ability evaluation. When evaluating the VOC adsorption / desorption ability, after pre-treatment of the sample described later, the evaluation temperature is 20 ° C., and the evaluation pressure range is less than 1 in relative pressure (equilibrium pressure with respect to the saturated vapor pressure).
In the evaluation of the VOC adsorption / desorption ability, it is considered that the moisture adsorbed on the sample surface and structure affects the VOC adsorption / desorption ability. went.

FIG. 1 shows the results of a methanol adsorption / desorption isotherm using methanol as the VOC for the evaluation of the VOC adsorption / desorption ability of Sample A. In FIG. 1, the horizontal axis represents the relative pressure [p / p ₀ ], which is the ratio of the equilibrium pressure p to the saturated vapor pressure p ₀ , and the vertical axis represents the gas adsorption amount per sample mass in a standard state (0 ° C., The adsorption amount [cm ³ (STP) / g] determined by converting to a volume of 1 atm) is shown.
The adsorption / desorption isotherm was measured five times by automatic control (see FIG. 1). In the continuous measurement, the same sample was used, but each time one cycle measurement of adsorption / desorption was completed, degassing was performed at 20 ° C. and 10 Pa for 1 hour, and then the next measurement was performed.

Regarding the continuous measurement of adsorption / desorption, when the adsorption / desorption measurement at the first cycle of adsorption / desorption and the adsorption / desorption measurement at the second to fifth cycles were compared, the rate of change in adsorption amount at a relative pressure of 0.8 was −33%.
This indicates that 33% of adsorption sites exist in which methanol cannot be desorbed only by pressure change (it is not desorbed unless further heated to exceed 110 ° C.).

<Reference example>
-Conventional synthesis method-
A concentration: 74 mmol / L sodium orthosilicate aqueous solution (500 mL) was added to an aluminum chloride aqueous solution (500 mL) having a concentration of 180 mmol / L, followed by stirring for 30 minutes. To this solution, 93 mL of a sodium hydroxide aqueous solution having a concentration of 1 mol / L was added at a dropping rate of 2 mL / min, and the pH was adjusted to 7.0.

  After the pH-adjusted solution was stirred for 30 minutes, centrifugal separation was carried out for 5 minutes at a rotational speed of 3,000 rpm using a TOMY Corporation: Superma23 and standard rotor NA-16 as a centrifugal separator. After centrifugation, the supernatant solution was discharged, the gel precipitate was redispersed in pure water, and returned to the volume before centrifugation. Such desalting treatment by centrifugation was performed three times.

Pure water was added to the gel-like precipitate obtained after the third desalting of the desalting treatment to make the volume 12 L. The solution was adjusted to pH = 4.0 by adding 60 mL of hydrochloric acid having a concentration of 1 mol / L and stirred for 30 minutes. At this time, the Si concentration in the solution was 2 mmol / L, and the Al concentration was 4 mmol / L.
The solution was then placed in a dryer and heated at 98 ° C. for 96 hours (4 days).

  To the solution after heating (aluminum silicate concentration 0.4 g / L), 60 mL of a 1 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 9.0. The solution was aggregated by adjusting the pH, and the aggregate was precipitated by the same centrifugal separation as described above, whereby the supernatant was discharged. The desalting process of adding pure water to this and returning to the volume before centrifugation was performed 3 times.

  The gel-like precipitate obtained after the desalting treatment was dried at 60 ° C. for 72 hours (3 days) to obtain 4.8 g of powder. The obtained powder was designated as Sample B.

<Evaluation>
(Structural evaluation)
Sample B had a BET specific surface area of 323 m ² / g, a total pore volume of 0.22 cm ³ / g, and an average pore diameter of 2.7 nm.
In the powder X-ray diffraction spectrum of Sample B, broad peaks were observed at 2θ = 4.8 °, 9.7 °, 14.0 °, 18.3, 27.3 °, and 40.8 °. .

(VOC adsorption / desorption ability evaluation)
Using methanol as the VOC, the adsorption / desorption isotherm was continuously measured in the same manner as in Example 1. The results are shown in FIG.
Next, methanol, ethanol, acetone, and methyl ethyl ketone were used as VOCs, and adsorption isotherms immediately after vacuum drying for each VOC were measured. The results are shown in FIG.

Regarding the continuous measurement of adsorption / desorption, when the adsorption / desorption measurement at the first cycle of adsorption / desorption and the adsorption / desorption measurement at the second to fifth cycles were compared, the rate of change in adsorption amount at a relative pressure of 0.8 was -23%.
This indicates that there is 23% of adsorption sites where methanol cannot be desorbed only by pressure change (it will not desorb unless further heated to exceed 110 ° C.).

<Comparative Example 1>
Sample C was a commercially available zeolite (Wako Pure Chemical Industries, Ltd., trade name: Molecular Sieves 13X). Using sample C, the VOC adsorption / desorption ability was evaluated in the same manner as in Example 1. The results are shown in FIG.
Moreover, the methanol, ethanol, acetone, and methyl ethyl ketone were used as VOC, and the adsorption isotherm immediately after vacuum drying with respect to each VOC was measured. The results are shown in FIG.

Regarding the continuous measurement of adsorption / desorption, when the adsorption / desorption measurement at the first cycle of adsorption / desorption and the adsorption / desorption measurement at the second to fifth cycles were compared, the rate of change in adsorption amount at a relative pressure of 0.8 was −63%.
This indicates that 63% of adsorption sites exist in which methanol cannot be desorbed only by a pressure change (it does not desorb unless further heated to exceed 110 ° C.).

From the above, by the method for producing a volatile organic compound adsorbent of the present invention, a volatile organic compound adsorbent having excellent VOC adsorption / desorption ability similar to that of aluminum silicate produced by a conventional method can be obtained. It can be seen that it can be manufactured.
Moreover, the aluminum silicate manufactured by the manufacturing method of the volatile organic compound adsorbent of this invention shows the adsorbability which was excellent with respect to various VOC similarly to the aluminum silicate manufactured by the conventional method. It is expected that.

Claims (9)

(A) A reaction product is obtained by mixing a solution containing silicate ions and a solution containing aluminum ions such that the ratio Si / Al of silicon atoms to aluminum atoms is 0.4 to 0.6 in molar ratio. Process,
(B) a step of desalting and solid-separating the reaction product;
(C) A step of subjecting the solid separated in the step (b) to a heat treatment in an aqueous medium in the presence of an acid under a concentration condition in which the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. When,
(D) A method for producing a volatile organic compound adsorbent, comprising: desalting and solid-separating the product obtained by the heat treatment in the step (c). (A) A reaction product is obtained by mixing a solution containing silicate ions and a solution containing aluminum ions such that the ratio Si / Al of silicon atoms to aluminum atoms is 0.4 to 0.6 in molar ratio. Process,
(B) a step of desalting and solid-separating the reaction product;
(C) A step of subjecting the solid separated in the step (b) to a heat treatment in an aqueous medium in the presence of an acid under a concentration condition in which the silicon atom concentration is 100 mmol / L or more and the aluminum atom concentration is 100 mmol / L or more. When,
(D) A method for producing a volatile organic compound adsorbent, comprising: desalting and solid-separating the product obtained by heat treatment in the step (c) at a pH of 8 to 10.   The volatile property according to claim 1 or 2, wherein the step (c) is a step of adjusting the pH to 3 or more and less than 7 and performing a heat treatment at a temperature of 80 ° C to 160 ° C for 96 hours. A method for producing an organic compound adsorbent. The step (a), as a silicon atom concentration of the solution containing the silicate ions is 100 mmol / L or more, a step of mixing a solution comprising a solution and aluminum ions containing the silicate ions, claim The manufacturing method of the volatile organic compound adsorption agent of Claim 2 or Claim 3. (A) A reaction product is obtained by mixing a solution containing silicate ions and a solution containing aluminum ions such that the ratio Si / Al of silicon atoms to aluminum atoms is 0.4 to 0.6 in molar ratio. Process,
(B) a step of desalting and solid-separating the reaction product;
(C) Concentration conditions in which the solid separated in the step (b) is in an aqueous medium in the presence of an acid and has a pH of 3 to 5 and a silicon atom concentration of 100 mmol / L or more and an aluminum atom concentration of 100 mmol / L or more. A step of heat-treating with,
(D) A method for producing a volatile organic compound adsorbent, comprising: desalting and solid-separating the product obtained by the heat treatment in the step (c).   The solid separated in the step (b) has an electric conductivity of 4.0 S / m or less when dispersed in water so that the weight concentration is 60 g / kg. The manufacturing method of the volatile organic compound adsorption agent of any one of these.   The step (b) includes a step of dispersing the reaction product in an aqueous medium to obtain a dispersion, and a step of adjusting the pH of the dispersion to 5 to 7 to precipitate the reaction product. The manufacturing method of the volatile organic compound adsorption agent of any one of Claims 1-6. The volatile organic compound adsorbent has a BET specific surface area of 250 m ² / g or more, a total pore volume of 0.1 cm ³ / g or more, an average pore diameter of 1.5 nm or more, and a CuKα ray. The volatile organic compound adsorbent according to any one of claims 1 to 7, wherein the powder X-ray diffraction spectrum according to claim 1 has peaks at 2θ = 26.9 ° and around 40.3 °. Production method.   The volatile organic compound adsorption agent manufactured by the manufacturing method of the volatile organic compound adsorption agent of any one of Claims 1-8.