JP3516811B2 - Activated carbon fiber molded adsorbent - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an activated carbon fiber molded adsorbent, and more specifically, it is a molded body obtained by mixing and encapsulating fibrillated alkali-resistant cellulose fibers with a tow of activated carbon fibers, which has a gas phase Alternatively, it is a molded adsorbent used for adsorbing and removing coloring substances, malodorous substances and other harmful substances contained in the liquid phase.

[0002]

BACKGROUND OF THE INVENTION Activated carbon fiber has a large specific surface area and a high adsorption / desorption rate compared to conventionally used granular activated carbon. Therefore, it is processed into fabrics, mats, felts, etc., and used in solvent recovery equipment and air cleaners. The adsorbent used in the phase,
It is used as an adsorbent used in the liquid phase of filters for water purifiers. However, since activated carbon fiber has a low packing density and further poor mechanical strength, deodorizing filters and the like made from this material have poor mechanical strength and the disadvantage that packing density is low is unavoidable.

A molded adsorbent using activated carbon fibers was developed to improve mechanical strength and packing density, which are weak points of activated carbon fibers, and the main activated carbon fibers disclosed so far have been used. There are the following molded products.

(1) A shaped adsorbent containing activated carbon fibers and a heat-meltable synthetic resin, in which the activated carbon fibers are randomly bonded and held by the heat-meltable synthetic resin and integrally formed to have a papermaking structure (Japanese Patent Publication No. 5- (55183, Japanese Patent Publication No. 7-12429)
Is. As the heat-meltable synthetic resin, a polymer having a melting point of 50 to 200 ° C. is used. Specifically, polyethylene,
Examples thereof include polypropylene, polyvinyl alcohol, polyacrylonitrile and the like.

According to this method, a molded adsorbent having a high density can be obtained, but there is a problem that the strength of the molded body is weak and the heat resistance of the molded body is low. 100 activated carbon fibers
It can be used repeatedly if it is regenerated at a temperature above ℃,
When a heat-meltable resin is used as the binder, the strength during heating may extremely decrease and deform,
There has been a problem that it is difficult to reproduce it sufficiently. When the heat-meltable resin is used as a binder, it is suction-molded from a mixed slurry with the heat-meltable synthetic resin, dehydrated, and then heat-dried to form a molded body. However, since the strength of the molded product obtained by suction molding is low, it is difficult to take out the molded product from the molding frame, and if it is forcibly taken out, the molded product may be deformed. For this reason, there is also a problem that the yield of the molded product decreases.

(2) In a shaped adsorbent containing activated carbon as a main component, a shaped adsorbent in which fibrillated aramid fibers or fibrillated acrylic fibers are used as an enveloping material and activated carbon is bound by this entanglement is disclosed. (JP-A-6-335632 and JP-A-7-16458). This adsorption molded body has a characteristic of high heat resistance, and by using a fibrillated envelope material, the strength is significantly improved as compared with the molded body. In addition, since the wet strength of the molded product is high, the problem that the molded product loses its shape when taken out from the mold has been greatly improved. However, from a practical point of view, this molded adsorbent still does not have sufficient strength.

[0007] The above-mentioned adsorption molded body makes a mixed slurry of activated carbon fibers and a binder, and suction-molds this slurry.
It is created by dehydration and drying. In contrast to this method, a method for obtaining a shaped adsorbent by a dry method is also disclosed.

(3) A molded adsorbent in which activated carbon fibers and hot-melt synthetic resin fibers are mixed or mixed and then heated to fuse the two is disclosed (JP-A-56-24151). However, since this method cannot produce a shaped adsorbent having a complicated structure, this shaped adsorbent has not been sufficiently practical.

[0009]

As described above, there are problems with the conventional molded adsorbent mainly composed of activated carbon fiber,
Considering that heat resistance, strength of molded body or molding of complicated structure is insufficient, we will develop and provide activated carbon fiber molded adsorbent with high heat resistance and strength and excellent moldability. It is a thing.

[0010]

[Means for Solving the Problems] Activated carbon fibers have excellent adsorption properties, but have weak mechanical strength and low packing density, which improves the mechanical strength and packing density, as well as heat resistance and moldability. In order to form a molded adsorbent having a three-dimensional structure with excellent pressure loss and low pressure loss, an envelope material suitable for this purpose was studied. As a result, they have found that fibrillated cellulose fibers having alkali resistance are suitable for this purpose, and have reached the present invention based on this.

That is, it is an activated carbon fiber molded adsorbent containing activated carbon fibers as a main component and fibrillated alkali resistant cellulose fibers as an enveloping material. Here, as the cellulose fibers, polynosic rayon fibers or mercerized natural cellulose fibers are preferable. Further, in the molded product of the present invention, the content of the fibrillated alkali-resistant cellulose fiber is 0.
Molded adsorbents of 3 to 20 parts by weight are preferred.

Although the molded adsorbent of the present invention is not used in an alkaline solution, the alkali resistance of the cellulosic fiber was selected as an index of the performance of the envelope material because the performance and the envelope of the obtained molded body were selected. This is because it was found that there is an apparently high correlation between the alkali resistance of the cellulose fibers used as the material. Hereinafter, the present invention will be described in detail.

The main component of the shaped adsorbent of the present invention is activated carbon fiber. The activated carbon fiber used here is not particularly limited, and generally has a large specific surface area of several 100 m ² or more per 1 g, and can be used in a wide range as long as it is a fibrous carbon material exhibiting high adsorptivity. Among these, the present invention has a diameter of 2 to 20 μm.
, Activated carbon fibers having a specific surface area of 500 to 3000 m ² / g and a pore radius of 3 to 20 Å are preferable.

The raw material of the activated carbon fiber is also not particularly limited. For example, rayon fibers, polyacrylonitrile fibers, phenol resin fibers, petroleum pitch fibers, coal pitch fibers and the like can all be used as raw materials. In the present invention, an adsorbent such as granular activated carbon, powdered activated carbon, or zeolite may be mixed in addition to the activated carbon fiber, and an envelope material may be further added to perform molding. The mixing ratio of other materials to the activated carbon fiber is not particularly limited, but the volume ratio of the activated carbon fiber in the molded adsorbent is 50%.
When it becomes below, the superiority of the adsorption performance of the activated carbon fiber cannot be exhibited.

In the shaped adsorbent of the present invention, the packing density of activated carbon fibers is 0.12 to 0.25 g / cc, but the density of the granular adsorbent is generally much higher than that of the activated carbon fibers (for example, in the case of granular activated carbon, the packing density is Is about 0.4 g / cc). When about 70% by weight of granular activated carbon is mixed, the activated carbon fibers and the granular activated carbon have almost the same volume ratio.

The activated carbon fiber molded adsorbent of the present invention contains fibrillated alkali resistant cellulose fibers as a main component other than the activated carbon fibers. The alkali-resistant cellulose fibers used here are not particularly limited, and examples thereof include polynosic rayon fibers and mercerized natural cellulose fibers. The polynosic rayon fiber is obtained by extruding sodium cellulose xanthate into a spinning bath having a low coagulability and gradually coagulating while stretching, and the fiber has a circular cross-sectional shape and a smooth surface.
Further, the fibers have a microfibril structure and are easily fibrillated. The degree of polymerization is 400 or more, which is considerably higher than that of ordinary rayon, and the water absorption is low and the wet strength is high.

What is the mercerization treatment? Natural cellulose fibers such as softwood wood pulp, hardwood wood pulp, pineapple pulp, Manila hemp pulp and sisal pulp are placed in a cold alkali, for example, 3 to 4 in a 40% potassium hydroxide solution.
The fibers are swollen by immersing for a period of time to remove hemicellulose, which easily disintegrates in the pulp, and at the same time, the flat cross section of the fibers is circularized. Further, regenerated cellulose fibers made of pulp having a high α-cellulose content such as linter pulp, for example, polynosic rayon, are originally high in alkali resistance and easily fibrillated by beating, and thus are suitable for the envelope material of the present invention. There is.

In the present invention, the fibrillated alkali-resistant cellulose fibers are stirred and mixed with the activated carbon fibers in water to prepare an aqueous slurry, and the activated carbon fibers are in a state of being enveloped with the fibrillated cellulose fibers. Further, the slurry is filtered through a mold for molding having a large number of small holes for suction to form an activated carbon fiber molded adsorbent enveloped with fibrillated cellulose fibers, which is dehydrated and dried by heating to form the molded adsorbent of the present invention. Is obtained.

When cellulosic fibers having low alkali resistance are used as the envelope material of the molded adsorbent, a phenomenon in which the pressure loss of the molded adsorbent increases is observed. Pressure loss refers to the pressure required to flow a certain amount of fluid. The shaped adsorbent is mainly used to pass liquids and gases and remove impurities such as malodorous substances contained in the liquids and gases. The lower the pressure loss, the more fluid can flow at a constant pressure. Therefore, it is preferable.

When fibrils obtained by beating ordinary natural fibers were used as an envelope material, an increase in pressure loss was observed. On the other hand, when fibrils obtained by beating cellulose fibers having alkali resistance were used as the envelope material, there was almost no increase in pressure loss. The reason for this is considered to be that the pulp that is beaten with natural fibers has a flat cross-section, whereas the fibrils that have been beaten with alkali-resistant cellulose fibers have a cross-section close to a circle.

When fibrils obtained by beating cellulosic fibers having alkali resistance as described above are used as the envelope material, it is recognized that an increase in pressure loss of the molded adsorbent is suppressed. Nevertheless, the mechanical strength of the molded adsorbent and the effect of improving the moldability that enables it to be molded into a complicated shape are also recognized. This is because the shape of fibrillated polynosic rayon fiber or mercerized natural cellulose fiber has a shape in which many short branches grow from a long trunk, so that it has a high function of strengthening its structure when activated carbon fiber is enveloped. On the other hand, fibrils obtained by beating natural fibers as they are are in a disjointed shape such as thick and short branches irregularly accumulated, and therefore have a function to enhance the structural properties of activated carbon fibers even if they are enveloped. It is thought that this is because there is not enough. As a result of the test by the present inventors, it was recognized that the alkali resistance of the cellulose fiber is apparently the best as a parameter for displaying the envelope function of fibrils as described above.

The content of the fibrillated alkali-resistant cellulose fibers used in the present invention is not particularly limited, but is 0.
3% to 20% by weight is preferred. When the content of the alkali-resistant cellulose fiber is 0.3% or less, the strength of the molded adsorbent is remarkably reduced and the practicality is lost. Further, if the content is 20% or more, the amount of the envelope material occupying in the shaped adsorbent becomes large and the adsorbability is deteriorated, which is not preferable. If the content of the envelope material is in the range of 2% to 10%, the strength of the shaped adsorbent is high and the adsorbability of the shaped body is also high, which is more preferable.

The fibrils of alkali-resistant cellulose fibers can be obtained by beating with a beater or refiner. The activated carbon fiber molded adsorbent of the present invention has a beating degree of CFS.
A (Canadian freeness) value of 100 to 700 ml is preferable. Here, the CFS value is generally used as an index showing the degree of beating of pulp, and is indicated by the amount of water permeated when water is filtered through a fixed amount of pulp. A lower value indicates a higher degree of pulp dispersion and swelling due to beating, and a higher value indicates a lower dispersion and swelling property.

A wet paper strength enhancer may be further added to the activated carbon fiber molded adsorbent of the present invention. The wet strength agent is preferable, for example, because epoxidized polyamide polyamine has an effect of improving both the wet strength and the dry strength of the molded body.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The activated carbon fiber molded adsorbent of the present invention can be prepared as follows. First, the alkali-resistant cellulose fiber is beaten with a beater or a refiner until the CFS is in the range of 100 to 700 ml. It is preferable that the alkaline cellulose fiber is cut into a length of about 1 to 5 mm and then put into a beater because the dispersed state in water becomes good.

Next, a slurry of activated carbon cut to a length of 0.5 to 20 mm is prepared, and 2 to 10% by weight of beaten and fibrillated alkaline cellulose fibers are added and uniformly mixed. A beater may be used during mixing, or a mixing screw may be used. It is preferable to adjust the slurry concentration to 0.1 to 5% by weight because the adsorbent can be easily molded.

A mold for molding having a large number of suction holes is put in this activated carbon slurry, and the slurry is sucked and filtered to mold an adsorbent. By sucking the slurry with a pump, the mixture of the activated carbon fiber and the enveloping material can be uniformly accumulated on the surface of the core body having the small holes. The molded adsorbent formed is removed from the mold and then dried to prepare an activated carbon fiber adsorbent.

Since the molded adsorbent of the present invention has high wet strength, the molded adsorbent does not easily lose its shape when it is removed from the mold and is easy to manufacture. The drying temperature is preferably 100 ° C. or higher in order to evaporate water, but a molded adsorbent having strength and heat resistance can be obtained even by drying at a low temperature of 80 ° C. or lower, but this is not preferable because the drying time becomes long.

The fibrillated cellulose fibers having alkali resistance do not show a certain melting point and have the property of gradually carbonizing in the same shape at high temperature. Therefore, the activated carbon fiber molded adsorbent of the present invention has a heat resistance of 120 ° C or higher and can be used even at a temperature of 150 ° C or higher. Activated carbon fiber has excellent adsorption performance and can be regenerated at low temperature and in a shorter time than granular activated carbon. However, regeneration of the activated carbon fiber requires a temperature of at least 100 ° C or higher, preferably 120 ° C or higher. The molded adsorbent of the present invention has a temperature of 120 ° C.
Since the strength decrease by the above is extremely small, it can be widely used in a high temperature atmosphere as an activated carbon fiber molded adsorbent.

Therefore, the activated carbon fiber shaped adsorbent of the present invention can be regenerated at a higher temperature than conventional shaped adsorbents, and therefore has a high adsorbent recovery rate and can be used from one regeneration to the next regeneration. In addition, the life of the entire shaped adsorbent is extended.

The activated carbon fiber shaped adsorbent of the present invention can be used for adsorption and removal of trace impurities and harmful components in a liquid phase and a gas phase. For example, it can be used for water purifier filters (removal of residual chlorine, removal of organic chlorine compounds such as trihalomethane, removal of mold odor) or filters for air purifiers, treatment of waste liquid such as plating, solvent recovery of organic chlorine compounds, etc. it can.

[0032]

EXAMPLES The present invention will be described in more detail below with reference to examples.

Example 1 FIG. 1 is a perspective view of a mold for preparing the activated carbon fiber molded adsorbent of the present invention, and FIG. 2 is a mode of the activated carbon fiber molded adsorbent of the present invention obtained in this example. FIG.

Polynosic rayon fiber (2d × 3 mm)
The beater beaten the CSF to 400 ml. Average fiber length is 20
1 kg of activated carbon fiber cut to about mm (specific surface area
1500m ² / g) and 50g of polynosic rayon fiber beaten with a beater (5% mixed with activated carbon fiber) are put into a beater, mixed and beaten, and the fibrils of polynosic rayon fiber produced by beating are sufficient. It was enveloped in. This prepared slurry was put into a tank to prepare a slurry for suction molding.

A large number of suction holes are provided on the surface of the core 1 of the adsorbent molding frame, and blind flanges 2 and 3 (diameter 65 m are provided at both ends.
m) Put a cylindrical molding frame (outer diameter 30 mm, length 250 mm) equipped with a jig into the mixed slurry and suck the slurry from the inside of the core with a suction pump to remove the core of the molding frame. A mixture of activated carbon fibers and fibrillated polynosic rayon fibers was deposited around the periphery. In this way, a hollow cylindrical adsorbent was produced.

The blind flanges on both ends were removed, and the core was removed from the molded body. Since the formed body has high wet strength (strength in a wet state), the core body could be easily pulled out. When removing a core from a wet molded body, the shape of the molded body with weak wet strength often collapses, and the problem was that the yield of the molded body was low. Had been improved to.

The molded body was heated and dried at 120 ° C. for 12 hours to obtain a molded adsorbent. The obtained molded adsorbent has an inner diameter of 30 mm,
With an outer diameter of 65 mm and a length of 250 mm, the density of this molding is 0.18 g / c
It was c. It was confirmed that the specific surface area of this molded body was 1300 m ² / g (measured by the BET method using N ₂ gas), which was sufficiently practical.

The strength of this molded product at 25 ° C. and 140 ° C. is shown in Table 1. The maximum load required to compress the compact by 4 mm was defined as the strength of the compact adsorbent. The strength and heat resistance were good. Further, the pressure loss when water was flown through the molded body at a flow rate of 10 liters / min was low, and the practicability was sufficiently confirmed.

[0039]

[Table 1]

60 ppb of trihalomethane (30 ppb of chloroform, chlorodibromomethane) was added to the shaped adsorbent obtained above.
10 ppb, dichlorobromomethane 10 ppb, bromomethane 10
Water containing ppb) was passed at a flow rate of 10 liters / min.
Removal rate of trihalomethane is 80% when passing 4000 liters of water.
Met.

The molded body was regenerated by passing steam at 150 ° C. for 20 minutes, and then water containing 60 ppb of trihalomethane was passed through. Trihalomethane removal rate at the beginning of water flow is 100%, 4000
The removal rate at the time of passing liter of water was 80%, and the adsorption performance of trihalomethane was completely regenerated.

Further, the polynosic rayon fiber was immersed in a potassium hydroxide solution (20% by weight) at 40 ° C. for 20 days, and the change in strength was observed. It was confirmed that this fiber had a high strength even after 20 days, and that the strength did not decrease even when immersed in an alkaline solution, and the alkali resistance was high. Moreover, the alkaline solution was not contaminated by the eluate from the fiber.

(Example 2) Mercerized hardwood wood pulp was mixed with a double disc refiner to obtain CSF of 400 ml.
I beat up. An activated carbon fiber molded adsorbent was prepared in the same manner as in Example 1 except that 50 g (5% based on activated carbon fiber) was used. The heat resistance and pressure loss were measured and shown in Table 1. It had high wet strength and was easy to prepare.
The molded product after drying has high strength and good heat resistance,
Furthermore, the pressure loss was low and the performance was sufficient for practical use.

The alkali resistance of the mercerized hardwood wood pulp was measured in the same manner as in Example 1. No reduction in strength was observed and the alkali resistance was good. Further, the alkaline solution was not contaminated by the eluate from the fiber.

Example 3 50 g of polynosic rayon fiber beaten in the same manner as in Example 1 (5% based on activated carbon fiber) and 10 g of wet paper strength enhancer epoxidized polyamidoamine (based on activated carbon fiber) A molded body was prepared in the same manner as in Example 1 except that the addition amount was 1%). The wet strength of the molded body was good and the molding was easy. An adsorbent having good strength and heat resistance, a low pressure loss, and high practicality was obtained. The physical properties of the molded product are shown in Table 1.

Comparative Example 1 Hardwood wood pulp was beaten with a double disc refiner to a CSF of 400 ml. An activated carbon fiber molded adsorbent was produced in the same manner as in Example 1 except that this was used. The physical properties of this molded product are shown in Table 1. The wet strength of this molded body was high and it was easy to prepare. The strength of the molded product after drying was low as compared with the case where the cellulose fiber having alkali resistance was used and was not practical. Further, the pressure loss of this molded body was high and the practicality was poor.

The alkali resistance of hardwood wood pulp was measured in the same manner as in Example 1. It was found that there was elution from the pulp due to the soiling of the alkaline solution. The strength of the pulp was reduced and the pulp had poor alkali resistance.

Comparative Example 2 Hardwood wood pulp was beaten to a CSF of 400 ml with a double disc refiner. 25 g of this (2.5% based on activated carbon fiber) and 25 g of polyacrylonitrile fiber with a softening point of 80 ° C (2.5% based on activated carbon fiber)
A molded body was prepared in the same manner as in Example 1 except that was used. The wet strength of this molded product was weak, and the molded product in a wet state often lost its shape when the core was removed. This molded body was dried under the same conditions as in Example 1. Table 1 shows the strength at 25 ° C and the strength at 140 ° C of the obtained molded body. 140 ° C
Then, the strength was significantly reduced, and it was found that this molded body had poor heat resistance.

Comparative Example 3 A molded product was prepared in the same manner as in Example 1 except that 50 g of polyacrylonitrile fiber having a softening point of 80 ° C. was used without beating. The wet strength of this molded product was extremely weak, and most of the molded product collapsed when the core was removed. Since a molded product which was not partially broken was obtained, this molded product was dried at 100 ° C. for 18 hours. The molded body collapsed when dried at 140 ° C. The strength of the molded body after drying was measured.
The strength at 40 ° C was extremely weak and not practical. The physical properties of this molded product are shown in Table 1.

The removal rate of the adsorption molded body obtained above was passed through water containing trihalomethane under the same conditions as in the adsorption test of trihalomethane of Example 1. The removal rate at the time of passing 4000 liters was 80% as in the case of Example 1.

After the hot water of 75 ° C. was regenerated through this molded body for 20 minutes and then water containing trihalomethane was passed through, the removal rate of trihalomethane was 90% immediately after the start of water flow. The rate dropped to 80%. It was difficult to sufficiently regenerate the molded product because it was observed that the strength of the molded product dropped sharply when heated to 80 ° C or higher.

Example 4 A molded product was prepared under the same conditions as in Example 1 except that the polynosic rayon fiber was changed to 150 g, and its physical properties were measured. The results are shown in Table 1.
The measured value of the specific surface area was slightly lowered because the ratio of the activated carbon fiber was lowered, but the strength and the pressure loss were good, and it was possible to sufficiently use it.

Comparative Example 4 A molded product was prepared under the same conditions as in Example 1 except that the polynosic rayon fiber was 250 g, and the physical properties were measured. The results are shown in Table 1.
The strength is excellent, but the pressure loss is considerably increased. The specific surface area of the molded product was significantly reduced, and its practicality was insufficient. It is considered that the reason why the specific surface area decreased is that the ratio of the enveloping material increased and thus a part of the surface of the activated carbon fiber was covered.

[0054]

Industrial Applicability The present invention is an activated carbon fiber molded adsorbent containing activated carbon fibers as main components and fibrillated alkali-resistant cellulose fibers as an enveloping material, which has high wet strength, high strength at high temperature, and excellent heat resistance. It is characterized by a high recovery rate of adsorptivity due to treatment. It can be used for adsorptive removal of trace impurities and harmful components in liquid and gas phases. For example, it is suitable for a water purifier filter or an air purifier filter, solvent recovery, and the like.

[Brief description of drawings]

FIG. 1 shows a perspective view of a mold for preparing an activated carbon fiber molded adsorbent of the present invention.

2 shows a perspective view of one embodiment of the activated carbon fiber molded adsorbent of the present invention obtained in Example 1. FIG.

[Explanation of symbols]

1 Formwork for molding adsorbent preparation 2 Formwork core 3 Small core suction holes 4,4 'formwork flange 5 Filtrate outlet 6 Activated carbon fiber molded adsorbent

Claims (3)

(57) [Claims] 1. A activated carbon fiber molded adsorbent comprising alkali-resistant cellulose fibers fibrillated as activated carbon fibers and the envelope material as the main component,耐A fibrillated
The content of Lucari cellulose fiber is 100 weight of activated carbon fiber.
0.3 to 20 parts by weight based on the amount of activated carbon fiber composition
Shaped adsorbent. 2. The activated carbon fiber molded adsorbent according to claim 1, wherein the cellulosic fibers are polynosic rayon fibers. 3. The activated carbon fiber molded adsorbent according to claim 1, wherein the cellulose fibers are mercerized natural cellulose fibers.