JP6085335B2 - Activated carbon molded body, method for producing the activated carbon molded body, adsorbent using the activated carbon molded body, and occlusion material - Google Patents

Description

  The present invention relates to an activated carbon molded body, a method for producing the activated carbon molded body, an adsorbent using the activated carbon molded body, and an occlusion material.

  Activated carbon is widely used as various adsorbents because of its large specific surface area and developed pore structure. For example, it is used in various liquid phase treatments such as water purification treatment, various gas phase treatments such as deodorization treatment, and air purification treatment. Focusing on the properties of activated carbon such as the conductivity and electron transfer function, or the ability to carry a highly dispersed catalyst on the surface of the pores of the activated carbon, carbon electrodes and fuel cells for electric double layer capacitors It is used as a material for electrodes such as carbon electrodes for batteries such as air batteries and lithium ion batteries. In recent years, activated carbon has attracted attention as an energy storage material such as hydrogen storage and methane storage.

Activated carbon is used in various forms such as powdered activated carbon, granular activated carbon, and fibrous activated carbon. For example, powdered activated carbon is likely to be clogged, and the effect of dust on the human body is regarded as a problem. . The sufficient green density is not obtained in the granular activated carbon and fibrous activated carbon. Therefore, an activated carbon molded body in which activated carbon and a binder are mixed and processed into an arbitrary shape has been proposed.

For example, Patent Document 1 discloses a carbon material having a specific surface area of 1000 m ² / g or more and a molded body density of 0.4 g / cm ³ or more and 1 g / cm ³ or less, polytetrafluoroethylene of 10% by weight or less, and the like. A hydrogen occlusion material in which a binder is mixed is disclosed. According to this technique, since the specific surface area of the carbon material and the density of the compact are both large, the amount of hydrogen occlusion per unit volume can be increased.

  Patent Document 2 discloses an adsorbent molded article having a polyolefin thin coat layer on the surface of the adsorbent, wherein the polyolefin is a polyolefin having a viscosity characteristic of a melt flow rate of 1 g / 10 min or less. An adsorbent molded body is disclosed. According to this technology, there are no problems such as dirty hands even when touched by hand or black dust coming out due to wear, good contact between the adsorbent and aqueous solution, and full function as an adsorbent it can.

  Further, Patent Document 3 describes mixing granular or powdered activated carbon and two or more organic polymer binders having different melt indexes, filling the resulting mixture into a mold, and heating and pressing to form. A method for producing a featured activated carbon molded body is disclosed. According to this technique, it has sufficient strength, has low resistance to water flow, and can increase the ability to remove harmful substances.

JP 2003-38953 A JP 2000-263040 A JP 2005-119902 A

  The activated carbon molded body is required to have sufficient strength against damage caused by friction during handling and use. However, when the binder content is increased to increase the strength, there are problems such as a decrease in the specific surface area and pore volume of the activated carbon.

  The present invention has been made paying attention to the circumstances as described above, and its object is to provide an activated carbon molded article having sufficient strength, a large specific surface area and a large pore volume, and a method for producing the same. It is in.

  The activated carbon molded body of the present invention that can solve the above problems is obtained by mixing activated carbon and a polyolefin resin having an average particle diameter of 1 μm or more and 50 μm or less and subjecting the resulting mixture to isotropic pressure treatment. Has a gist.

  It is also a preferred embodiment that the polyolefin resin is contained in an amount of 1% by mass to 15% by mass with respect to a total of 100% by mass of the polyolefin resin and the activated carbon. The activated carbon molded body of the present invention is also a preferred embodiment for use as an adsorbent or an occlusion material.

  Moreover, the manufacturing method of the activated carbon molded body of this invention has a summary in mixing activated carbon and polyolefin resin with an average particle diameter of 1 μm or more and 50 μm or less, and subjecting the obtained mixture to isotropic pressure treatment.

  ADVANTAGE OF THE INVENTION According to this invention, while having sufficient intensity | strength, the activated carbon molded object with a large specific surface area and pore volume can be provided. Therefore, if the activated carbon molded body of the present invention is used, an adsorbent having high strength and excellent adsorption characteristics, or an occlusion material having excellent occlusion characteristics can be provided. Further, according to the present invention, an activated carbon molded body having the above characteristics can be easily produced.

FIG. 1 is a graph plotting the relationship between the amount of binder and the strength of the molded body of the example. FIG. 2 is a graph showing the strength of the molded bodies 4 and 7 of the example.

  The present inventors have repeated research on activated carbon molded bodies having a high specific surface area and pore volume and high strength even when a binder is added. First, when the activated carbon was molded without including a binder, the activated carbon molded body had low strength and was brittle and easily broken. Therefore, a mixture containing a binder in activated carbon was molded, and the molding method was examined. When an activated carbon molded body is manufactured by uniaxial pressure treatment using a mold, which is a conventional molding method, if the treatment pressure is increased to obtain sufficient strength, the pores of the activated carbon in contact with the mold surface are damaged. As a result, the specific surface area and pore volume decreased. When the treatment pressure was lowered, the specific surface area and pore volume were high, but sufficient strength was not obtained, and cracking occurred during handling and use of the activated carbon molded body.

Therefore, as a result of further investigations on the method for forming activated carbon by the present inventors, it was found that the activated carbon molded body obtained by the isotropic pressure treatment has a large specific surface area and pore volume and high strength. . When the isotropic pressure treatment is performed, the surface of the mixture can be pressurized at the same pressure, so that the voids inside the molded body are reduced, the density of the molded body is improved, and the fluidity of the activated carbon and the binder is improved, so It is considered that the number of contact points increases and the strength improves. Further, the strength can be increased at a processing pressure lower than that of the uniaxial pressurizing process. Moreover, a molded object density can be improved by an isotropic pressurization process. The ratio of the thus the pore volume per compact volume obtained from the product of the pore volume × compact density of the activated carbon molded body (hereinafter sometimes referred to as "pore volume per compact volume"), and activated carbon molded body It is possible to increase the specific surface area per molded body volume (hereinafter, also referred to as “specific surface area per molded body volume”) obtained from the product of surface area × molded body density.

  In addition, the present inventors have found that the above effect is a unique effect when a polyolefin resin is used as a binder. Although various materials are used as the binder, for example, polytetrafluoroethylene (PTFE) used in Patent Document 1 has high viscoelasticity at room temperature, and can easily bind activated carbon to each other. A sufficient strength cannot be obtained. If a thermoplastic resin that has a low melting point and melts at the temperature during the pressure treatment is used, the molten resin is taken into the pores and the adsorption sites are reduced. However, when a polyolefin resin having a predetermined average particle diameter is used, the isotropic pressure treatment does not significantly reduce the specific surface area and pore volume of the activated carbon, and the activated carbons are relatively low pressure treatment. Can be firmly bound.

  As a result of the above studies, the present inventors have found that the above problems can be solved by mixing activated carbon and a polyolefin resin having a predetermined average particle diameter and subjecting the obtained mixture to isotropic pressure treatment. Invented.

  The present invention will be described below.

  In the present invention, activated carbon is obtained by activating a carbon material as a raw material. Activated carbon powdery activated carbon made from sawdust, wood chips, charcoal, peat, etc .; granular activated carbon made from charcoal, coconut shell charcoal, coal, oil carbon, phenol, etc .; carbonaceous material petroleum coke, coal Carbonaceous activated carbon made from coke, petroleum pitch, coal pitch, coal tar pitch, and composites thereof; synthetic resin (phenol resin, polyacrylonitrile (PAN), polyimide, furan resin, etc.), cellulosic fiber (paper) , Cotton fibers, etc.), and activated carbon fibers made from these composites (paper-phenolic resin laminates, etc.) as raw materials. Among these, granular activated carbon and activated carbon fiber are preferable.

  The activated carbon is activated by a known method such as a gas activation method or a chemical activation method after carbonizing a carbonaceous material. Examples of the gas activation method include an activation method using a gas such as water vapor, carbon dioxide, air, or combustion gas. Chemical activation methods include chemicals such as phosphoric acid, zinc chloride, calcium chloride, magnesium chloride, sulfuric acid, caustic soda, potassium hydroxide, sodium hydroxide, etc .; carbonates such as sodium carbonate, potassium carbonate, etc. A method is illustrated. The activated carbon is preferably steam activated charcoal or alkali activated charcoal, and more preferably steam activated charcoal. In the present invention, when steam activated carbon is used, an activated carbon molded body having higher strength can be obtained.

The specific surface area of the activated carbon is not particularly limited, but the specific surface area is preferably 700 m ² / g or more, more preferably 800 m ² / g or more from the viewpoint of securing a sufficient adsorption amount or occlusion amount. The upper limit of the specific surface area is not particularly limited. However, since the strength of the activated carbon itself may be lowered, it is preferably 4000 m ² / g or less, more preferably 3000 m ² / g or less, still more preferably 2500 m ² / g or less, and most preferably. Is 2000 m ² / g or less. The pore volume of the activated carbon is not particularly limited, but from the same viewpoint, it is preferably 0.35 cm ³ / g or more, more preferably 0.40 cm ³ / g or more, preferably 2.2 cm ³ / g or less, more preferably 1.7 cm ³ / g or less. Further, the average pore diameter of the activated carbon is not particularly limited, and may be appropriately adjusted according to the adsorbent or occluded object. The average pore diameter is preferably 3.0 nm or less, more preferably 2.5 nm or less, preferably 1.6 nm or more, more preferably 1.7 nm or more. The specific surface area, pore volume, and average pore diameter are values based on the measurement methods described in the examples.

  In the present invention, a polyolefin resin having an average particle diameter of 1 μm or more and 50 μm or less is used as a binder (binder) mixed with the activated carbon. The average particle size of the polyolefin resin is determined by obtaining a volume-based cumulative frequency curve from the measurement result of the particle size distribution of the polyolefin resin measured using a laser diffraction particle size distribution analyzer SALD-2000 (manufactured by Shimadzu Corporation). The particle diameter at a frequency of 50% is defined as the average particle diameter.

  The polyolefin resin is preferably polyethylene or polypropylene, and more preferably polyethylene. The polyethylene may be any of high density polyethylene, low density polyethylene, linear low density polyethylene, and a polyethylene copolymer. Polyethylene copolymers include ethylene and vinyl acetate copolymers, ethylene and methacrylic acid ester copolymers, ethylene and methacrylic acid copolymers, and ionomers in which a part thereof is replaced with a metal salt. Various known copolymers are exemplified. These can be used alone or in any combination.

  The average particle diameter of the polyolefin resin mixed with the activated carbon is 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more. On the other hand, if it is too large, the contact point between the polyolefin resin and the activated carbon may decrease, so the average particle size of the polyolefin resin is 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.

  In the present invention, activated carbon and a polyolefin resin having an average particle diameter of 1 to 50 μm are mixed. However, the content of the polyolefin resin is not particularly limited, and may be appropriately adjusted so as to obtain a desired strength. Increasing the content of the polyolefin resin can increase the strength of the activated carbon molded body. If the content of the polyolefin resin is too small, the activated carbon may not be sufficiently bound, so the content of the polyolefin resin ([polyolefin resin content / (polyolefin resin content + active carbon content) × 100]) is: Preferably it is 1 mass% or more with respect to a total of 100 mass% of polyolefin resin and activated carbon, More preferably, it is 3 mass% or more. On the other hand, when the content of the polyolefin resin is too large, the strength of the activated carbon molded body becomes too high, and the workability may be lowered. In addition, the polyolefin resin itself does not have characteristics as activated carbon, which causes a decrease in specific surface area and pore volume, and may deteriorate characteristics such as adsorption performance and occlusion performance of the activated carbon molded body. The content of the polyolefin resin is preferably 15% by mass or less, more preferably 10% by mass or less, with respect to the total 100% by mass of the polyolefin resin and activated carbon.

  In the present invention, the mixture is molded by isotropic pressure treatment. The isotropic pressure treatment is not particularly limited as long as it is a method capable of applying pressure equal to the surface of the mixture and performing pressure molding without directionality. As the isotropic pressurization process, cold isostatic pressurization process (CIP: Cold Isostatic Pressing), hydrostatic pressurization process, rubber press process, hot isostatic pressurization process (HIP: HOT Isostatic Pressing). Among these, the cold isostatic pressing (CIP) capable of applying a three-dimensionally uniform pressure at room temperature is preferable. Further, the cold isostatic pressure treatment (CIP) may be either a wet method or a dry method. A known medium such as gas or liquid may be used as the pressurizing medium.

The treatment pressure during the isotropic pressure treatment is not particularly limited, but if the pressure is too low, the carbon substances cannot be sufficiently bound to each other, and the strength of the obtained activated carbon compact and the density of the compact are sufficiently increased. There are times when you can't. If the pressure is too high, the pores may be damaged. Therefore, the pressure is preferably 50 MPa or more, more preferably 100 MPa or more, preferably 300 MPa or less, more preferably 250 MPa or less, and still more preferably 200 MPa or less. The processing time is not particularly limited. The pressure holding time is preferably 1 minute or longer, more preferably 5 minutes or longer. On the other hand, since the above effect is saturated, the pressure holding time is preferably 60 minutes or less, more preferably 30 minutes or less.

  The activated carbon molded body obtained by the isotropic pressure treatment has improved strength. Although it depends on the content of the polyolefin resin and the isotropic pressure treatment conditions, the activated carbon molded body that satisfies the above-mentioned preferable conditions preferably has a strength of 0.7 MPa or more, more preferably 1 MPa or more. Since the activated carbon molded body of the present invention has high strength, it is not damaged by friction during handling or use. Accordingly, higher packing density can be achieved, and adsorption efficiency and storage capacity can be increased.

When the binder is added, the specific surface area decreases, but according to the production method of the present invention, since the activated carbon molded body has a high molded body density, the pore volume per molded body volume and the specific surface area per molded body volume are large. . The density of the molded body is not particularly limited, but is preferably 0.3 g / cm ³ or more, more preferably 0.35 g / cm ³ or more, preferably 1.2 g / cm ³ or less, more preferably 1.0 g / cm ³ or less. It is.

Pore volume per compact volume (cm ³ / cm ³⁾ is preferably 0.09 cm ³ / cm ³ or more, more preferably 0.12 cm ³ / cm ³ or more, more preferably 0.3 cm ³ / cm ³ That's it. If the pore volume per molded body volume is high, the activated carbon molded body exhibits excellent adsorption characteristics and occlusion characteristics.

In addition to the pore volume per molded body volume, the activated carbon molded body that satisfies the specific surface area per molded body volume has much better adsorption performance or occlusion performance in various applications such as adsorbents or occlusion materials. Play. The specific surface area (m ² / cm ³ ) per molded body volume is preferably 210 m ² / cm ³ or more, more preferably 280 m ² / cm ³ or more, and further preferably 700 m ² / cm ³ or more.

  The size of the activated carbon molded body is not particularly limited and can be appropriately selected depending on the application. Further, the shape to be molded is not particularly limited.

  The activated carbon molded body obtained by the above isotropic pressure treatment may be secondarily molded into a desired shape such as a pellet shape, a plate shape, a briquette shape or a spherical shape according to various uses. The activated carbon molded body of the present invention (including the secondary molded product, the same shall apply hereinafter) can be used as, for example, an adsorbent or an occlusion material. Examples of the adsorbent include liquid phase uses such as water purification treatment, drainage treatment, and precious metal recovery treatment, and gas phase uses such as air purification treatment, deodorization treatment, gas separation treatment, solvent recovery treatment, and exhaust gas treatment. Examples of the occlusion material include energy storage applications such as hydrogen and methane.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Molded body 1
Coconut shell steam activated charcoal (MC Evatech Co., Ltd .: Z10-28) and polyethylene (PE, average particle size 30 μm) were mixed. In addition, it added and mixed so that polyethylene content might be 4.8 mass% with respect to a total of 100 mass% of polyethylene and coconut shell steam activated charcoal, and the mixture was obtained. The resulting mixture was molded by cold isostatic pressing (CIP). Specifically, after the mixture is filled in a nylon-polyethylene bag and sealed, the bag is filled in a hydrostatic pressure powder molding apparatus (manufactured by Nippon R & D Co., Ltd.) and then the pressure is increased to 200 MPa and held for 10 minutes. And then molded. The obtained molded body was dried in a heater at 150 ° C. for 2 hours to obtain a molded body 1.

Molded body 2
A molded body 2 was obtained in the same manner as the molded body 1 except that polyethylene was added in an amount of 9.1 mass% with respect to a total of 100 mass% of polyethylene and activated carbon.

Molded body 3
A molded body 3 was obtained in the same manner as the molded body 1 except that the average particle size of the polyethylene used was 10 μm.

Molded body 4
After adding 2.5 times the potassium hydroxide by mass ratio to the carbide of the paper-phenolic resin laminate, activation treatment was performed at 800 ° C. for 2 hours in a nitrogen atmosphere. The activated carbon after the activation treatment was washed in order of water washing (60 ° C. warm water), acid (hydrochloric acid) washing, and water washing (60 ° C. hot water) to obtain activated carbon A from which metal impurities were removed. A mixture was obtained by adding and mixing polyethylene (PE, average particle diameter 10 μm) to 7.4% by mass with respect to 100% by mass in total of polyethylene and activated carbon A. The obtained mixture was subjected to cold isostatic pressing (CIP) in the same manner as the molded body 1 to obtain a molded body 4.

Molded body 5
A molded body 5 was obtained in the same manner as the molded body 1 except that polyethylene (average particle size 30 μm) was added to 2.9 mass% with respect to a total of 100 mass% of polyethylene and the activated carbon of the molded body 1. .

Molded body 6
The mixture of the compact 1 was subjected to uniaxial pressure treatment instead of cold isostatic pressure treatment. Specifically, the mold (φ19.85 mm, height 24.69 mm, actual effective height 17.60 mm) was filled, pressurized with a hand press machine (uniaxial), held at 200 MPa for 10 minutes, and then 150 ° C. Was dried in a heating machine for 2 hours to obtain a molded body 6.

Molded body 7
Using the mixture of the molded body 4, the molded body 7 was obtained by filling a mold in the same manner as the molded body 6, pressurizing and drying.

Molded body 8
Except that polyethylene was changed to polytetrafluoroethylene powder (PTFE) and added so that polytetrafluoroethylene was 7.4% by mass with respect to 100% by mass in total of polytetrafluoroethylene and activated carbon, molded body 4 In the same manner, activated carbon 8 was obtained. The obtained molded body 8 was very brittle and could not maintain its shape, so the strength and the like could not be measured.

The molded body density, specific surface area, total pore volume, average pore diameter, and strength of each molded body were measured by the following methods and listed in Table 1.

< Molded body density>
The molded body density was calculated from the molded body by cutting a rectangular parallelepiped block (length 1 cm × width 1 cm × height 1 cm) from the mass (g) and volume (cm ³ ) of the block according to the following formula.
Compact density (g / cm ³ ) = mass (g) / volume (cm ³ )

<Specific surface area>
After 0.2 g of the compact was heated at 250 ° C. under vacuum, a nitrogen adsorption isotherm was determined using a nitrogen adsorption device (manufactured by Micromeritics: ASAP-2400), and a specific surface area was calculated by the BET method.

<Total pore volume>
The nitrogen adsorption amount at the relative pressure (p / p0) = 0.93 from the nitrogen adsorption isotherm was defined as the total pore volume (cm ³ / g).

<Average pore diameter>
The pores of the activated carbon were assumed to be cylindrical and were calculated according to the following formula.
Average pore diameter (nm) = 4 × total pore volume / specific surface area × 1000

<Pore volume per volume of compact>
Pore volume per compact volume (cm ³ / cm ³⁾ = total pore volume (cm ³ / g) × moldings Density (g / cm ³⁾

<Specific surface area per molded body volume>
Specific surface area per compact volume (m ² / cm ³⁾ = specific surface area (m ² / g) × moldings Density (g / cm ³⁾

<Strength test>
Using a Tensilon universal testing machine (ORENTEC Co., Ltd .: RTC-1325A), the strength of the test piece until the test piece was broken was measured at a test speed of 1 mm / min. The strength was calculated by dividing the value of the maximum load at the time of failure by the cross-sectional area of the test piece. The strength was evaluated to be 0.7 MPa or more, and 1 MPa or more to be more excellent.

  As shown in Table 1, molded bodies 1 to 5 satisfying the requirements of the present invention had a strength of 0.7 MPa or more. In particular, the compacts 1 to 4 had higher strength of 1 MPa or more.

  When the molded body 1 (4.8% by mass), the molded body 2 (9.1% by mass), and the molded body 5 (2.9% by mass) differing only in the binder content are compared, the strength increases as the binder content increases. Improved. In both cases, the pore volume per compact volume and the specific surface area per compact volume were large and high in strength.

  Further, the relationship between the binder amount and the strength was plotted on a graph for the molded bodies 1 to 3 (◯ in the figure), the molded body 5 (Δ in the figure), and the molded body 6 (◇ in the figure) (FIG. 1). The molded products 1 to 3 and 5 molded by cold isostatic pressing (CIP) showed a tendency that the strength increased as the amount of the binder increased. On the other hand, the molded body 6 molded by the uniaxial pressure treatment was significantly inferior in strength to the molded body 1 under the same conditions except for the molding method.

  Moreover, the intensity | strength of the molded objects 4 and 7 which shape | molded the alkali activated carbon on the same conditions except the shaping | molding method was shown on the graph (FIG. 2). The molded body 4 subjected to the cold isostatic pressing (CIP) and the molded body 7 subjected to the uniaxial pressure treatment were substantially equal in properties other than the strength as shown in Table 1, but the molded body 4 was the molded body. The strength was more than twice as high as 7.

  When the molded body 3 using steam activated charcoal and the molded body 4 using alkali activated carbon were compared, the strength of the molded body 3 was higher than that of the molded body 4 having a high binder content.

Claims (12)

  An activated carbon molded article obtained by mixing activated carbon and a polyolefin resin having an average particle diameter of 1 μm or more and 50 μm or less and subjecting the obtained mixture to isotropic pressure treatment.   The activated carbon molded body according to claim 1, wherein the polyolefin resin is contained in an amount of 1% by mass to 15% by mass with respect to a total of 100% by mass of the polyolefin resin and the activated carbon. The activated carbon molded body is 0.35 g / cm. ³ The activated carbon molded body according to claim 1 or 2, which has the above molded body density. The activated carbon molded body is 0.09 cm ³ / Cm ³ The activated carbon molded body according to any one of claims 1 to 3, which has a pore volume per said molded body volume. The activated carbon molded body is 210m ² / Cm ³ The activated carbon molded body according to any one of claims 1 to 4, which has a specific surface area per volume of the molded body. The activated carbon molded body according to any one of claims 1 to 5, wherein the activated carbon molded body is formed by binding activated carbon with a binder. An adsorbent using the activated carbon molded body according to any one of claims 1 to 6 . The occlusion material using the activated carbon molded object in any one of Claims 1-6 .   A method for producing an activated carbon molded body, comprising mixing activated carbon and a polyolefin resin having an average particle diameter of 1 μm or more and 50 μm or less, and subjecting the obtained mixture to isotropic pressure treatment. The method for producing an activated carbon molded body according to claim 9, wherein the polyolefin resin is contained in an amount of 1% by mass to 15% by mass with respect to a total of 100% by mass of the polyolefin resin and the activated carbon. The activated carbon is
Specific surface area: 700m ² / G-4000m ² / G,
Pore volume: 0.35cm ³ /G-2.2cm ³ / G,
Average pore diameter 1.6 nm to 3.0 nm
The method for producing an activated carbon molded body according to claim 9 or 10. The isotropic pressure treatment is
Processing pressure: 50 MPa to 300 MPa
Pressurization holding time: 1 minute to 60 minutes
The method for producing an activated carbon molded body according to any one of claims 9 to 11.