JPH0929043A - Adsorbent and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtains an adsorbent which efficiently adsorbs polar and polarizable substances such as hydrogen sulfide, ammonia and acetic acid under a high humidity. SOLUTION: This adsorbent consists of a hydrophobic carbon compound present on the surface of a composite oxide. The absorbent has the adsorptive ability of a substance having a polar group, where the ability is characteristic of the composite oxide and also has an activity maintained even at the time of high humidity by allowing a hydrophobic substance to be present to such an extent that its adsorptive ability is not deteriorated. In addition, it is possible to produce the hydrophobic carbon compound on the surface of the composite oxide mainly by controlling a baking atmosphere, a baking temperature and the amount of a binder at the time of molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adsorbent for efficiently adsorbing and removing substances having polar groups such as hydrogen sulfide, ammonia and acetic acid under high humidity, and a method for producing the adsorbent.

[0002]

2. Description of the Related Art Adsorbents are used for the purpose of adsorbing and removing substances that have diffused in the gas phase or liquid phase, but due to their characteristics, they are applied to malodor treatment, water purification treatment, exhaust treatment, purification, chromatography, etc. There is.

Among these utilization methods, deodorization is a generally known application example, and representative adsorbents thereof include activated carbon, solid acid, solid base and zeolite.

Since activated carbon has a very fine pore structure as compared with other adsorbents, it has a high specific surface area and is hydrophobic because it is composed of carbon itself. Since it has such characteristics, activated carbon as an adsorbent generally easily adsorbs long-chain molecules and adsorbs various substances. It is also effective for mixed gas, and is easy to maintain because it is not affected by the humidity of the processing gas. However, it has a low adsorption capacity for so-called low molecular weight polar substances such as ammonia, basic substances such as amines, and acidic substances such as hydrogen sulfide and thiols, which have a bad odor.

On the other hand, solid acids, solid bases, zeolites and the like show acidity or basicity by themselves, and also have an ion exchange property, so that they have a high affinity with a substance having a polar group, and their adsorption form is also chemical. Since it is an adsorption, it is firmly bonded to the surface. However, when a substance (water) that is more easily adsorbed than the adsorbed substance approaches the surface of the adsorbent, the already adsorbed substance is desorbed and replaced, so-called adsorptive substitution occurs, so the adsorption capacity for the adsorbed substance decreases under high humidity. To do.

[0006]

Therefore, when activated carbon, solid acid, solid base, zeolite, etc. are used as the adsorbent, the use conditions and adsorbed species are limited due to their properties, and sufficient adsorption characteristics cannot be obtained. . In particular, it is difficult to treat a substance having a polar group having an offensive odor under high humidity using these, and it is not possible to obtain the adsorption property equivalent to that under low humidity.

Therefore, the present invention is characterized in that it can satisfactorily adsorb these substances having a polar group having an offensive odor, can inhibit the adsorption substitution with water under high humidity, and can maintain the original adsorption ability regardless of humidity. The present invention provides an adsorbent that

[0008]

The adsorbent according to the present invention comprises:
It is characterized in that a hydrophobic carbon compound is present on the surface of the composite oxide. By allowing a hydrophobic substance to exist on the surface to such an extent that the adsorption ability does not decrease, it has an adsorption ability for a substance having a polar group, which is a characteristic of complex oxides, and can maintain the activity even at high humidity.

Specifically, a composite oxide component serving as an adsorbent and a molding aid are integrally kneaded and molded, and a nitrogen atmosphere or oxygen is introduced in an amount of 5 vol% or less at a firing temperature of 500 ° C. to 8 ° C.
Bake at 00 ° C. Here, the atmosphere may be changed during the firing process. As a result, the organic substance used as a molding aid is decomposed to form a porous body, and a hydrophobic carbon compound such as carbonaceous material and tar is produced on the surface of the adsorbent. At this time 4
It is preferable that 5 vol% or less of oxygen is mixed in the nitrogen atmosphere in a part of the temperature range lower than 00 ° C., and firing is performed in the nitrogen atmosphere at 400 ° C. or higher. This is about 260-3
This is because the decomposition of the organic matter starts in the range of 70 ° C., and the decomposition of the organic matter can be controlled by setting the atmosphere, and the amount of the hydrophobic carbon compound generated on the surface of the adsorbent can be adjusted.

As another method for producing a hydrophobic carbon compound on the surface of the composite oxide, a molded body is fired in advance and impregnated with an organic substance, the atmosphere, temperature and the like are controlled, and heat treatment is performed to carry out the target adsorption. A method of obtaining the agent can be considered.

The hydrophobic carbon compound is preferably contained in an amount of 0.5 to 12 wt% in terms of carbon amount. If the carbon content is 0.5 wt% or less, the surface exposure of the composite oxide becomes excessive and adsorption substitution is likely to occur, so that the hydrophobic function deteriorates. Further, when it exceeds 12 wt%, since more hydrophobic carbon compounds than necessary are present on the surface of the complex oxide, the surface exposure of the complex oxide is reduced, and the frequency of contact of the odorous substance with the complex oxide, that is, the adsorption of odor. The amount decreases. In addition, the strength of the molded body decreases.

The materials used as a molding aid, which is a raw material of the hydrophobic carbon compound, are cellulose derivative, polyvinyl alcohol, acrylic acid derivative, soluble starch, gelatin, etc. as a binder, polyalkylene glycol, fatty acid ammonium salt as a plasticizer. Examples of the releasing agent include fatty acids, fatty acid esters, and waxes, water retaining agents such as polyhydric alcohols, and pore forming agents and retaining agents such as granular cellulose, plastic beads, insoluble starch, and wax dispersions. Further, when the amount of addition is 100 parts by weight of the complex oxide, the total amount of organic components is 30 to
50 parts by weight are preferred. When the amount of the organic component is less than 30 parts by weight, the amount of the hydrophobic carbon compound is small, so that the hydrophobic effect is reduced, and when the amount of the organic component is more than 50 parts by weight, the amount of the hydrophobic carbon compound is excessive and the adsorption ability is decreased. In addition, the strength of the adsorbent itself decreases because the amount of pores of the adsorbent becomes too large, and it is difficult to form it into a honeycomb, granules, etc. Even if it can be formed, it will break during use. Therefore, it is difficult to actually provide it as an adsorbent.

According to the present invention, the surface of the complex oxide is hydrophobized by the above-mentioned treatment, so that the adsorptive substitution of the adsorbed substance having a polar group with the water content in the air is inhibited. Since the point amount can be controlled, good adsorption characteristics of the substance having a polar group can be obtained.

The rate of adsorption of the substance to be adsorbed in the porous adsorbent is limited by the process of diffusion into the pores, and the diffusion that occurs therein is greatly affected by its geometric structure. The diffusion is classified into molecular diffusion and Knudsen diffusion. When applied to these porous materials, the mean free path of each of molecular diffusion and Knudsen diffusion is 0.01 μm to 0.1 μm.
It is known that pores larger than μm and pores smaller than μm dominate. The catalyst body having a porous structure to which the gas phase diffusion theory in the pores is applied is described in the invention related to Japanese Patent Application Laid-Open No. 7-80329 already filed by the present inventors, and the invention can be used in the present invention. Thus, it is possible to increase the efficiency with which the complex oxide and the gas come into contact with each other. For example, when adsorbing a basic substance, by using SiO ₂ —Al ₂ O ₃ , the Bronsted acid points or L
It is known that when the ewis acid point functions and an acidic substance is adsorbed, by adding a solid base to the adsorbent, the base point existing on the surface becomes the adsorption point. Therefore, according to the present invention, the adsorption property does not deteriorate even under high humidity as in the conventional case, and further, the deterioration of properties over time and the product life are improved.

The components of this adsorbent are Si, Al, Ca,
It is composed of two or more kinds selected from oxides of Mg, Mn, Co and Ni. Many metal oxides newly express an acid when they are complexed with each other, and exhibit a remarkable effect that is not found in a single oxide. For example, those exhibiting strong acidity by complexing such as SiO ₂ —Al ₂ O ₃ , and M of solid base added to SiO ₂
Acid is also expressed by combining gO. On the other hand, examples of a substance that expresses a base include alkali and alkaline earth metal oxides, and among them, Ca and Mg are widely used. Therefore, an adsorbent suitable for the purpose can be produced by appropriately combining these materials.

The combination of these metal oxides is not particularly limited, and examples of combinations include MnO ₂ --SiO ₂ and Mn.
_{O 2 -SiO 2 -Al 2 O 3} , MnO 2 -SiO 2 -CaO,
_{MnO 2 -CaO-MgO, NiO-} SiO 2, NiO-
_{SiO 2 -Al 2 O 3, NiO} -SiO 2 -Al 2 O 3 -Ca
_{O, NiO-SiO 2 -Al 2} O 3 -MgO, NiO-A
_{l 2 O 3, NiO-CaO} , CoO-MnO 2 -SiO 2,
_{CoO-SiO 2 -Al 2 O 3} , CoO-SiO 2 -Al 2
_{O 3 -CaO, CoO-SiO 2} -CaO, CoO-Ni
_{O-SiO 2 -Al 2 O 3} -CaO , and the like can be given.

The conditions under which the adsorbent according to the present invention is actually used are preferably a temperature of 0 to 40 ° C. and a humidity of 95% RH or less. Even if the adsorbent surface gets wet due to dew condensation,
Due to its high water repellency, the surface dries quickly and the adsorption function is restored. When reclaiming, 300 ~ in a nitrogen atmosphere
By heating to 500 ° C., the adsorbed substance is desorbed and the adsorption ability is restored. In addition, various shapes such as a honeycomb shape, a corrugated shape, a pellet shape, a plate shape, and a granular shape can be used as the shape of the adsorbent molded body.

[0018]

The adsorbents have a high ability to adsorb a substance having a polar group and are not affected by humidity at all, and therefore have excellent adsorption characteristics under all humidity conditions and do not show deterioration of characteristics due to humidity change. Therefore, it is effective for removing a substance having an odor under high humidity.

[0019]

EXAMPLES Specific examples and comparative examples of the present invention will be shown below. However, the present invention is not limited to the following examples.

A. Preparation of adsorbent (Example 1) SiO ₂ 700 g, CaO 100 g,
200 g of CoO and 30 g of methyl cellulose as a binder were dry-mixed, 1100 g of water, 40 g of polyalkylene glycol as a plasticizer, 100 g of wax dispersion as a shape-retaining agent, 150 g of granular cellulose as a pore-forming agent, and 150 g of water-retaining agent. Glycerin (20 g) and fatty acid ester (20 g) as a release agent were added, and the mixture was kneaded with a kneader, formed into a honeycomb shape, and dried. In a range lower than 350 ° C., in a nitrogen atmosphere with an oxygen concentration of 2 vol%, 350 to
The adsorbent was obtained by firing in a nitrogen atmosphere at 720 ° C. and in the temperature lowering process.

Example 2 300 g of SiO ₂ and Al ₂ O
₃ g of 500 g, CoO of 200 g and methyl cellulose of 80 g as a binder were dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 3 250 g of SiO ₂ and Al ₂ O
250 g of ₃ and 500 g of MnO and 50 g of methyl cellulose as a binder were dry-mixed to obtain an adsorbent by the same additives and steps as in Example 1.

Example 4 300 g of SiO ₂ and Al ₂ O
200 g of Ca ₃ , 100 g of CaO, 400 g of NiO and 50 g of methyl cellulose as a binder were dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 5 300 g of SiO ₂ and Al ₂ O
₃ g of 100 g, CaO of 200 g, NiO of 400 g and methyl cellulose of 50 g as a binder were dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

(Embodiment 6) The same molded body as in Embodiment 5 was used.
In the range lower than 0 ° C, the adsorbent was obtained by firing in a nitrogen atmosphere having an oxygen concentration of 5 vol%, at 360 to 720 ° C, and in the temperature decreasing process in a pure nitrogen atmosphere.

(Embodiment 7) The same molded body as in Embodiment 5
In the range lower than 0 ° C, the adsorbent was obtained by firing in a nitrogen atmosphere having an oxygen concentration of 5 vol%, at 350 to 720 ° C, and in the temperature decreasing process in a pure nitrogen atmosphere.

(Embodiment 8) The same molded body as in Embodiment 5 was used.
In the range lower than 0 ° C., an adsorbent was obtained by firing in a nitrogen atmosphere having an oxygen concentration of 1 vol% at 350 to 720 ° C. and in a nitrogen atmosphere during the temperature lowering process.

Example 9 The same molded article as in Example 5 was fired at 720 ° C. in a nitrogen atmosphere to obtain an adsorbent.

(Example 10) The same molded article as in Example 5 was fired at 700 ° C in a nitrogen atmosphere to obtain an adsorbent.

(Example 11) The molded body obtained in Example 5 was fired at 690 ° C in a nitrogen atmosphere to obtain an adsorbent.

Example 12 300 g of SiO ₂ and Al ₂
O ₃ 200g, MgO 100g, NiO 400g
Then, 50 g of methyl cellulose as a binder was dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 13 300 g of SiO ₂ and Al ₂
O ₃ 100g, MgO 200g, NiO 400g
Then, 50 g of methyl cellulose as a binder was dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 14 300 g of SiO ₂ and Al ₂
O ₃ 400g, CaO 100g, CoO 200g
Then, 50 g of methyl cellulose as a binder was dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 15 200 g of SiO ₂ and Al ₂
200 g of O ₃ , 200 g of CaO, 400 g of NiO
Then, 50 g of methyl cellulose as a binder was dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 16 300 g of SiO ₂ and Al ₂
200 g of O ₃ , 200 g of CaO, 300 g of NiO
Then, 50 g of methyl cellulose as a binder was dry-mixed, and an adsorbent was obtained by the same additives and steps as in Example 1.

Example 17 300 g of SiO ₂ and Al ₂
An adsorbent was obtained by the dry addition of 200 g of O ₃ , 500 g of NiO, and 50 g of methyl cellulose as a binder by the same additives and steps as in Example 1.

Example 18 300 g of SiO ₂ and Ni
An adsorbent was obtained by dry-mixing 700 g of O and 50 g of methylcellulose as a binder by the same additives and steps as in Example 1.

(Comparative Example 1) The same molded body as in Example 5 was used as 35
In air below 0 ° C (oxygen concentration 20vol
%), 350 to 720 ° C., and the temperature decreasing process was performed in a pure nitrogen atmosphere to obtain an adsorbent.

(Comparative Example 2) 300 g of SiO ₂ and Al ₂ O
₃ g of 100 g, CaO of 200 g, NiO of 400 g and methyl cellulose of 100 g as a binder are dry-mixed, 1100 g of water, 50 g of polyalkylene glycol as a plasticizer, and 1 wax dispersion as a shape-retaining agent.
00 g, 200 g of granular cellulose as a pore forming agent, 30 g of glycerin as a water retention agent, and 30 g of a fatty acid ester as a release agent were added, and an adsorbent was obtained by the same steps as in Example 1.

Comparative Example 3 Commercially available activated carbon (Junsei Kagaku Co., Ltd.)
Manufactured) was used as it was.

Comparative Example 4 Commercially available silica (Aerosil 380 manufactured by Nippon Aerosil Co., Ltd.) was used as it was.

The adsorbent obtained here is JIS G 121
The carbon content was measured by the method described in 1-181. The specific surface area was measured by the BET method.

B. Adsorbent Activity Test Using the adsorbents obtained in Examples 1 to 18 and Comparative Examples 1 to 4 above, an adsorption test was conducted under the following test conditions.

1. Acid / base substance adsorption test In order to examine the acid / base adsorption capacity of the adsorbent, the adsorbent is dispersed in toluene in which the acid / base substance is dissolved, and the adsorption amount is calculated from the difference in solution concentration. An adsorption test was conducted. The adsorbing substance is n-undecanoic acid (U
A) and n-decylamine (DA) as the basic substance, which were individually dissolved in toluene were used. Regarding the shape of the test sample, the adsorbent after firing was ground in a mortar, and powder having a particle size of 840 to 2000 μm was used. As the powder to be tested, a dry powder and an undried powder were prepared.
The dry powder was obtained by heating the powder to be tested to 150 ° C. with a vacuum dryer and holding it for 24 hours. As the undried powder, a sample left in the air was used as it was. 0.5 g of the dried and undried powder to be tested was weighed into a sufficiently dried sample bottle, and 16 g of the solution having a known solute concentration was weighed into the sample bottle. Disperse this using an ultrasonic cleaner and
Left for 4 hours. The supernatant solution was filtered off, the solution concentration was quantified by gas chromatography, and the amount adsorbed on the powder to be tested was calculated. In addition, the difference in the amount of adsorption between the undried powder and the dry powder was expressed as a variation value. The test results are shown in Tables 1 and 2.

[0045]

[Table 1]

[0046]

[Table 2]

2. Sulfur-based odor removal test An odor removal test was performed using the following test conditions and the apparatus shown in FIG. Further, the difference between the removal rate at 60% RH and the removal rate at 90% RH was expressed as a variation value. Table 3 shows the results.

[0048]

[Table 3]

Test conditions Hydrogen sulfide (H ₂ S) concentration: 2.5 ppm, methylthiol (CH ₃ SH) concentration: 2.5 ppm Space velocity: 70,000 h ⁻¹ Temperature and humidity: 20 ° C. 60% RH or 90% RH Honeycomb cell density: 210 cells / inch ² According to the examples in Table 1, six kinds of numerical values including the numerical values of the adsorption amount of acid and base before and after drying and the fluctuation values before and after each drying were measured on the surface. Comparing the example which is the adsorbent of the composite oxide in the presence of the hydrophobic carbon and the comparative example which is the general adsorbent and the ordinary composite oxide having no hydrophobic carbon on the surface, the latter is found in the individual numerical values. Although the former is inferior in some cases, it is clear that the former, that is, the example of the present invention is superior to the comparative example when looking at all six types, and the effect of making hydrophobic carbon present on the surface of the composite oxide is clear. Can be seen.
Further, according to the examples of Table 2, the carbon amount is 0.5 to 12 wt%.
It can be seen that the range is preferable. Here, the six types of numerical values including the numerical values of the adsorption amounts of the acid and the base before and after the drying of Comparative Example 2 and the fluctuation values before and after the drying are not inferior to those in the example, but the formed granules are in solution. Since it broke due to the above, there was a problem in handling and it could not be actually used as an adsorbent. Further, according to the examples of Table 3, when only the removal rate is compared with the comparative example, some of the examples are inferior in individual numerical values, but when compared with the comparative example with respect to the variation value, It is clear that there is a marked difference between all the examples and the comparative examples. That is, the adsorbent of the present invention can be used in a good condition even under high humidity, which means that it can be stably used for a wide range of applications.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an odor removal test device.

[Explanation of symbols]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Takada 1-13-1 Nihonbashi, Chuo-ku, Tokyo TDK Corporation

Claims (5)

[Claims] 1. An adsorbent characterized in that a hydrophobic carbon compound is present on its surface. 2. The adsorbent according to claim 1, wherein the content of the hydrophobic carbon compound is 0.5 to 12 wt% in terms of carbon amount. 3. Si, Al, Ca, Mg, Mn, Ni, C
The adsorbent according to claim 1 or 2, wherein a hydrophobic carbon compound is present on the surface of the adsorbent composed of two or more kinds selected from oxides of o. 4. An adsorbent characterized in that a metal oxide constituting an adsorbent and a molding aid are integrally kneaded and molded, and then fired to generate a hydrophobic carbon compound on the surface of the adsorbent by decomposition of the molding aid. Manufacturing method. 5. The method for producing an adsorbent according to claim 4, wherein the calcination is performed in an inert gas atmosphere having an oxygen concentration of 5 vol% or less.