JPH0691166A - Rod-like activated carbon and its production - Google Patents

Abstract

PURPOSE:To obtain a new activated carbon having a large adsorption volume for gasoline vapor by partly fixing lots of fibrous activated carbon and spacers with a binder to produce a rod body so that vacant spaces are included among the fibrous activated carbon. CONSTITUTION:This rod-like activated carbon is obtd. by partly fixing lots of fibrous activated carbon 1 with a binder 3 through spacers 2 to form a rod as a whole but to make to have vacant spaces among the fibers. Since the rod-like activated carbon has highly oriented activated carbon fiber 1 in the axial direction and has high fiber density, the rod can have the adsorption of a high amt. By uniformly dispersing the spacers 2 among the fibrous activated carbon 1, the vacancies 5 among the carbon fibers can uniformly be dispersed in the center of the rod so that the material to be absorbed and a gas to be detached can easily be diffused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the removal of volatile hydrocarbons such as gasoline released into the atmosphere, the removal of odorous and gaseous toxic substances, and the removal of toxic substances in tap water, waste water and the like. The present invention relates to a rod-shaped activated carbon suitable for use in and a method for producing the same.

[0002]

2. Description of the Related Art The number of automobiles owned by our country is rapidly increasing due to the unstoppable wave of motorization. Most of them are gasoline vehicles, and a huge amount of gasoline is distributed and consumed. Distribution of gasoline,
Gasoline vapors emitted into the atmosphere during the consumption process cause photochemical smog and global warming (greenhouse gas), and reducing the amount of emission is important for protecting the global environment. is there.

[0003] Conventionally, as a method of preventing the emission of gasoline vapor from a gasoline tank or a carburetor to the atmosphere, a method of masking the outlet with a granular activated carbon packed bed, a so-called canister, has been taken. When the vehicle is parked, that is, when the vehicle stops running, heat from the engine is transferred to the carburetor, float tank, and gasoline tank, and vaporized gasoline tends to be released to the atmosphere. If there is no discharge port, pressure will be applied, so that the gasoline vapor is adsorbed to the granular activated carbon through the packed bed of the granular activated carbon to the outside air. When the vehicle enters high-speed running, air is sent to the engine through the granular activated carbon layer, and the adsorbed gasoline vapor is desorbed and burned in the engine compartment together with the gasoline vapor from the carburetor. In this adsorption / desorption, a pressure-operated valve is used to switch between adsorption and desorption in the granular activated carbon packed bed by the pressure of the carburetor and the manifold. Further, at the time of refueling, pressure will be applied if there is no discharge port, so that gasoline vapor is adsorbed to the granular activated carbon through the packed bed of the activated carbon particles to the outside air, as in the case of stopping the engine. In addition, such emission of gasoline vapor is also caused by temperature changes between nighttime and daytime, and at this time also, gasoline vapor is adsorbed and retained in the granular activated carbon layer.

[0004]

[Problems to be Solved by the Invention] In protecting the global environment, the cause of photochemical smog, global warming (greenhouse gas), etc. It is required to eliminate radiation completely. Currently, automobiles with a displacement of 1500cc to 2000cc use 300 to 500 grams of granular activated carbon in a canister of about 1000cc.

Generally, the performance of activated carbon used for canisters is evaluated by the butane effective adsorption amount, and for passenger cars in Japan, those having an effective butane adsorption amount of about 7 g / 100 cc have been developed and used. However, this current canister consisting of granular activated carbon bed is not sufficient to effectively absorb the emission of gasoline vapor. Therefore, it is conceivable to increase the amount of the existing granular activated carbon layer in order to achieve the reduction of the emission amount.

That is, the canister is upsized.
The amount of granular activated carbon commensurate with the amount of emissions during parking and refueling is
4 to 5 times the current level, with a canister volume of 4000cc to 50
It will be around 00cc. As described above, the large-sized canister has an increased pressure loss at the time of desorption by air, and is disadvantageous in switching between adsorption and desorption in the granular activated carbon packed bed due to the pressure of the carburetor and the manifold using the pressure actuated valve.
Further, the large canister occupies the engine compartment, which reduces the effective volume of the vehicle, increases the weight of the vehicle body, and makes it difficult to improve the fuel ratio, which is strongly required for global environmental problems. As described above, increasing the size of the canister causes problems such as an increase in pressure loss and an increase in vehicle body weight.

In recent years, fibrous activated carbon has attracted attention in place of granular activated carbon because of its large adsorption capacity of gasoline vapor per unit weight. However, the fibrous activated carbon has low strength as a fiber aggregate, poor workability, difficult to handle, easy to scatter, and poor in shape retention, and when used by filling, has a high porosity and a low packing density,
Therefore, there is a problem that the adsorption capacity of gasoline vapor per unit volume is small. When the packing density is increased and used, there is a problem that the pressure loss when the fluid containing the adsorbate and the desorption fluid is circulated becomes higher than that of the granular activated carbon.

[0008] The present invention provides a new activated carbon having a large adsorption capacity for gasoline vapor, which replaces the conventional granular activated carbon and fibrous activated carbon, a method for producing the same, and a hydrocarbon adsorption device using the activated carbon. It is intended.

[0009]

The present invention has led to the following inventions as a result of intensive studies for solving the above problems.
That is, the present invention is a rod-shaped activated carbon in which a large number of fibrous activated carbons are partially fixed to each other with a binder via binders to form a rod-shaped body, and voids are present between the fibrous activated carbons. It is an adsorption device for hydrocarbons in which activated carbon is packed in parallel in the gas flow direction, and the present invention is a method for producing rod-shaped activated carbon, in which a fine powdery spacer is introduced into a strand-like carbonaceous fiber, This is a treatment in which a fusion treatment is performed, a solvent containing a binder is impregnated, the solvent is removed, and then a carbonization treatment is followed by an activation treatment.

[0010]

1 is an explanatory view of the rod-shaped activated carbon of the present invention, FIG. 2 (a) is a partially enlarged view thereof, and FIG. 2 (b) is a sectional view thereof. As shown in FIGS. 1 and 2, the rod-shaped activated carbon of the present invention has a large number of fibrous activated carbons 1 partially fixed by a binder 3 via a spacer 2 to form a rod-shaped body as a whole, and has voids between the fibrous activated carbons. Have five.

Therefore, the rod-shaped activated carbon of the present invention has a structure in which the fibrous activated carbon is highly oriented in the axial direction of the rod (strand) and the fiber density is high. As a result, a higher adsorption amount was achieved compared with the granular activated carbon having a binary structure. Further, since the spacers 2 can be uniformly dispersed between the fibrous activated carbons, the voids 5 formed between the fibrous activated carbons that come close to each other have a structure in which they are evenly dispersed up to the center of the fiber. Diffusion becomes easy, and a higher adsorption rate and desorption rate by air can be obtained as compared with granular activated carbon.

Further, the rod-shaped activated carbon of the present invention has a spacer 2
Since the fibrous activated carbon 1 is partially fixed by the binder 3 through the, it is possible to obtain a rod-shaped structure having higher strength as compared with a bundle of activated carbon fibers, which can be put to practical use. Activated carbon strength was achieved. In addition, since the spacer 2 is made of a material having a high thermal conductivity, the thermal conductivity between the fibrous activated carbons 1 that are close to each other is improved, so that the rod-shaped activated carbon can be used in comparison with a simple activated fiber bundle or granular activated carbon. The thermal conductivity at the time of adsorption and desorption can be improved.

Further, by providing the rod-shaped adsorbent of the present invention so as to be densely packed in the direction parallel to the flow direction of the adsorbate, the adsorption capacity of hydrocarbons per packed volume is higher than that of the granular activated carbon packed bed. In addition to being able to be large, it has a structure in which the flow paths of the adsorbate and desorption fluid do not bend,
The pressure loss at the time of fluid inflow and outflow can be reduced. Further, by providing the rod-shaped adsorbent so as to be densely packed in the flow direction of the adsorbate, the convection and heat conduction between the closely adjacent rod-shaped desorbent fillers are improved, and the adsorption of hydrocarbons using the granular activated carbon packed bed is improved. Compared to the device, it absorbs hydrocarbons,
Adsorber for hydrocarbons desorbed by air (canister)
The effective adsorption amount of can be increased.

As described above, the present invention comprises the fibrous activated carbon, the binder and the spacer, the spacer and the fibrous activated carbon are partially fixed by the binder, and the fibrous activated carbon has voids. Compared with existing activated carbon such as granular activated carbon and activated carbon fiber, it has a high adsorption capacity, high adsorption rate and desorption rate by air, activated carbon strength for practical use, and is highly oriented in the axial direction. Excellent in thermal conductivity.

Further, according to the present invention, a hydrocarbon adsorbing device (canister) provided so as to densely fill the rod-shaped adsorbent in a direction parallel to the flow direction of the adsorbate is a hydrocarbon per filled volume. In terms of large adsorption capacity for hydrocarbons, low pressure loss during fluid inflow and outflow, and large effective adsorption amount of hydrocarbons when adsorbing hydrocarbons and desorbing with air, It is superior to the existing hydrocarbon adsorbing device (canister) consisting of a packed bed of activated carbon such as activated carbon and activated carbon fiber.

Next, the method for producing the rod-shaped activated carbon will be described in detail. The rod-shaped activated carbon is obtained by introducing a fine powder spacer into a strand-like carbonaceous fiber, infusibilizing it, impregnating it with a solvent containing a binder to remove the solvent, and then carbonizing and activating it. As described in Japanese Patent Publication No. 1-333573 and Japanese Patent Publication No. 4-1091, a method of introducing a fine powder spacer into a strand-like carbonaceous fiber is described.
For example, coal tar is used as the raw material and the quinoline insoluble content is 40%.
An optically anisotropic pitch containing is melt-spun to obtain a pitch fiber strand with a filament diameter of 13 μm and a number of filaments of 2000, and then this strand is ethanol containing 10% of natural flaky graphite powder with an average particle diameter of 0.6 μm. It is obtained by immersing in the dispersion liquid.

Stranded carbonaceous fibers are pitch fibers,
PAN fiber and phenol resin fiber can be used. The spacer need only be submicron particles,
Although not particularly limited, ceramics having good thermal conductivity such as boron nitride, titanium oxide, titanium oxide whiskers, silicon oxide, aluminum oxide are preferable.

The spacer dispersion medium is methanol,
Organic solvents such as ethanol and acetone, water and the like are used. The distance (gap) between the fibers is preferably 1/10 or less of the fiber diameter D. Examples of the binder include phenol resin, furan resin, epoxy resin, polyvinyl alcohol, coal tar pitch, coal tar and petroleum pitch.

The binder solvent is methanol,
Examples thereof include organic solvents such as acetone and aromatic hydrocarbons such as naphthalene. Next, the present invention will be described in more detail based on examples.

[0020]

【Example】

Example 1 Heat treatment was performed using coal tar as a raw material to remove benzene insoluble matter.
An optically isotropic pitch containing 56% by weight was melt-spun to obtain a pitch fiber strand having a filament diameter of 13 μm and a filament number of 4000. Average pitch of the obtained pitch fiber strands
0.8 μm boron nitride was impregnated into an ethanol dispersion containing 5% by weight. This treated strand in an oxygen atmosphere,
It was infusibilized up to 300 ° C. at a heating rate of 5 ° C./min. The obtained infusible fiber contained boron nitride between the fibers. The obtained infusible fiber strand was added to a naphthalene solution containing 20% by weight of coal tar pitch (solution temperature: 200%
It was dipped in (.degree. C.) for impregnation. This impregnated fiber strand was carbonized to 600 ° C in a nitrogen gas atmosphere. The obtained carbonized strand was cut into a fiber length of 50 mm, and activated at 950 ° C. in a heating furnace while flowing steam. The yield of the obtained rod-shaped activated carbon is 30% by weight based on the weight of the pitch fiber.
The fiber length is 38mm and the specific surface area by BET method is 1750m.
² / g, and the porosity inside the rod-shaped activated carbon measured by a mercury porosimeter was 0.15.

As shown in FIG. 3, the rod-shaped activated carbon is densely packed in an adsorption column in a direction parallel to the flow direction of the adsorbate,
Butane was adsorbed at a temperature of 25 ° C. until it was saturated, butane was desorbed with 650 times the nitrogen gas of the adsorbent layer, and the butane effective adsorption amount was measured. Measured butane effective adsorption amount is 14.2g / 10
It was 0cc. Comparative Example 1 The optically isotropic pitch produced by the method described in Example 1 was ground and sieved to obtain a pitch having an average particle size of 1.2 mm.
A pitch was inserted into the fluidized bed, air was circulated at a superficial velocity of 18 cm / sec, and the temperature was raised to 300 ° C. for infusibilization. The obtained infusible particles were pulverized and classified to obtain an infusibilized pitch having an average particle size of 15 μm. The obtained infusible pitch was mixed with 10% by weight of coal-based pitch containing a trace amount of quinoline insoluble matter having a softening point of 110 ° C in a rolling granulator and granulated to obtain spherical infusible particles having an average particle diameter of 4 mm. Got The obtained spherical infusible particles were activated at 950 ° C. in a kiln furnace while circulating steam. The yield of the obtained spherical activated carbon was 18% by weight based on the weight of the pitch, the average particle diameter was 2.0 mm, and the specific surface area by the BET method was 1310 m ² / g.

The spherical activated carbon was packed in an adsorption column,
Butane was adsorbed at a temperature of 25 ° C. until saturation, butane was desorbed with 650 times the nitrogen gas of the adsorbent layer, and the butane effective adsorption amount was measured. The measured butane effective adsorption amount is 4.2 g /
It was 100cc. The effectiveness of the present invention can be understood from these Examples and Comparative Examples. It should be noted that, in the above-mentioned Examples, the case where the entire surface is optically isotropic pitch was described as the heat-melting pitch, but the present invention is not limited to this, and an optically anisotropic pitch may be used, and basically spinning is performed. It suffices as long as it is a spinning pitch that does not contain solids or gas under the conditions and has a homogeneous flow characteristic.

[0023]

The rod-shaped activated carbon of the present invention is a fibrous activated carbon,
It is composed of a binder and a spacer, the spacer and the fibrous activated carbon are partially fixed by the binder, there is a gap between the fibrous activated carbon, and the fibrous activated carbon is highly oriented in the axial direction and formed into a rod shape. Therefore, it is possible to provide a new activated carbon that has a large adsorption capacity for gasoline vapor instead of the granular activated carbon.

[Brief description of drawings]

FIG. 1 is an explanatory view of a rod-shaped activated carbon according to the present invention.

FIG. 2 is a partial detailed view of a rod-shaped activated carbon according to the present invention.

FIG. 3 is an explanatory view of a canister filled with rod-shaped activated carbon according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Hanatani, 1 Kawasaki-cho, Chuo-ku, Chiba, Chiba Prefecture Technical Research Division, Kawasaki Steel Co., Ltd. (72) Inventor Yukihiro Osugi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Kawasaki Steel Corporation Technical Research Division

Claims (3)

[Claims] 1. A rod-shaped activated carbon, characterized in that a large number of fibrous activated carbons are partially fixed to each other with a binder via spacers to form rod-shaped bodies, and have voids between the fibrous activated carbons. 2. An adsorbing device for hydrocarbons, wherein the rod-shaped activated carbon according to claim 1 is packed in parallel with a gas flowing direction. 3. A strand-like carbonaceous fiber is introduced with a spacer in the form of fine powder, then subjected to infusibilization treatment, then impregnated with a solvent containing a binder, and after desolvation, carbonization treatment is followed by activation treatment. A method for producing rod-shaped activated carbon, which comprises applying the activated carbon.