JP2690986B2 - Activated carbon production method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing activated carbon, and more particularly to a method for producing activated carbon having good adsorption performance after endurance without lowering the production yield.

[Prior Art] Conventionally, an evaporated fuel collecting device using activated carbon is known to prevent the evaporated fuel from being released into the atmosphere.
In this evaporative fuel collection device, the evaporative fuel normally generated from the fuel system such as a fuel tank is once adsorbed on the activated carbon, and then the outside air is introduced into the activated carbon to desorb and desorb the evaporated fuel adsorbed on the activated carbon. The evaporated fuel is sent into the engine cylinder for combustion.

Activated carbon used in such an apparatus is usually particles containing carbon, which is usually coal or coconut shell, as it is, or a mixture of particles and a binder, molding, and then heating and dry distillation to release volatile substances, at the same time. Pores are formed on the particle surface by carbonizing tar or the like. Next, carbon is partially burned by heating the particles in an atmosphere of an oxidizing gas such as steam, carbon dioxide, or air to form fine pores extending from the pores to the periphery in the pores,
At the same time, activation is performed to form further pores or fine pores on the particle surface. In this way, activated carbon having a large number of micropores is formed.

[Problems to be Solved by the Invention] As described above, in the activation step, dry-distilled carbon is allowed to react in an oxidizing gas atmosphere such as steam, carbon dioxide, or air for a relatively long period of time, and fine pores, that is, pores in the micro range are generated. Is formed. The pores in this micro area have a pore radius of
Since it is very small at 20 Å or less, once the gasoline component etc. is adsorbed, it becomes difficult to desorb and the adsorption performance deteriorates. On the other hand, if the activation time is lengthened, the pores in the micro region gradually expand greatly and the pore distribution in the micro region moves to the side with a larger pore radius, but the carbonaceous material decreases, so the production yield decreases,
There is a problem that it is very disadvantageous in terms of mass productivity and manufacturing cost.

The present invention has been made in view of the above points, and provides a method for producing activated carbon that does not reduce the production yield and the adsorption performance after endurance.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an activated carbon raw material,
It is characterized in that 0.001 to 0.3 parts by weight of graphite and a binder are mixed with 1 part by weight of the raw material, and the mixture is molded, dried and activated. As a raw material, coal, coconut shell, etc. are generally used. When graphite is mixed at a ratio of less than 0.001 part by weight to 1 part by weight of raw material, the distribution of micropores in the micro region slightly moves to the side with a larger pore radius, and 0.3 parts by weight or more. If it is mixed in a large proportion, the adsorption performance will drop sharply, so it is in the range of 0.001 to 0.3 parts by weight.

[Operation] In the method of the present invention, the activated carbon raw material, 0.001 to 0.3 parts by weight of graphite per 1 part by weight of the raw material, and the binder are mixed, molded, carbonized, and activated. The fine pores are distributed to the side having a larger pore radius in the micro region. It is considered that this is because the pores of graphite remain as traditional pores with a pore radius of 20Å or more. As a result, since the desorbed air can diffuse to the depths of the pores at the time of desorption, accumulation of the residue in the micropores is suppressed and the durability performance is improved. Further, the production yield is improved because the activation time can be shortened.

[Examples] Examples of the present invention based on the production process of activated carbon shown in FIG. 1 are shown below, but the present invention is not limited thereto.

Example 1 100 parts by weight of raw material coal, 10 parts by weight of graphite and 20 parts by weight of a binder were kneaded and extruded into a shape having a diameter of 3 mm and a length of 10 mm. This formed charcoal is carbonized and the temperature is raised to 950.
Activated carbon was obtained by activating it in an externally heated rotary furnace under the conditions of ℃ and steam content of 0.66 g / hour for 1 g of dry-distilled coal.

Example 2 Activated carbon was obtained in the same manner as in Example 1 except that the amount of graphite was changed to 0.5 part by weight. Example 3 Activated carbon was obtained in the same manner as in Example 1, except that 30 parts by weight of graphite was used.

Comparative Example 1 100 parts by weight of raw material coal and 20 parts by weight of a binder were kneaded and extruded into a shape having a diameter of 3 mm and a length of 10 mm. The formed charcoal was subjected to dry distillation, and further activated in an externally heated rotary furnace under the conditions of a temperature of 950 ° C. and a steam content of 0.66 g / hour for 1 g of dry distillation charcoal to obtain activated carbon.

Comparative Example 2 100 parts by weight of raw material coal, 35 parts by weight of graphite, and 20 parts by weight of a binder were molded, carbonized and activated in the same manner as in Comparative Example 1 to obtain activated carbon.

Comparative Example 3 100 parts by weight of raw material coal, 0.05 parts by weight of graphite, and 20 parts by weight of a binder were molded, carbonized and activated in the same manner as in Comparative Example 1 to obtain activated carbon.

The pore distributions of the activated carbons obtained in Example 1 and Comparative Example 1 were measured by the methanol adsorption method, and differential pore volume distributions for each of the three activation times are shown in FIGS. 2 and 3, respectively. . (Methanol adsorption measurement was performed with an automatic adsorption amount measuring device manufactured by Tanaka Scientific Instruments Co., Ltd.) Note that dV / dlo on the vertical axis in FIGS. 2 and 3.
gR is a value obtained by differentiating the pore volume (V) by the logarithm of the pore radius (R).

2 and 3, that the activated carbon of Example 1 mixed with graphite has moved to the larger micro-region side in the pore radius distribution than the activated carbon of Comparative Example 1 not mixed with graphite. I understand. This indicates that, when the activation times are the same, the example can produce activated carbon having a larger micropore radius in the micro region.

In addition, in the activation step for producing the activated carbons of Examples 1 to 3 and Comparative Examples 1 to 3, activated carbon was produced by changing the activation time in the range of 4 to 7 hours, and the performance of the activated carbon in each case is shown in Table 1. It was shown to.

As is clear from Table 1, in Examples 1 to 3, there is no large difference in the pore radius and pore volume showing the adsorption performance, and the production yield, and in all, the pore radius exceeds 13.0Å. It can be read that the activation time takes 5 to 6 hours, whereas in Comparative Example 1 in which graphite is not mixed, the pore radius does not exceed 13.0 Å unless it exceeds 6 hours. Comparative Example 1
Also, it can be seen that the production yield of Comparative Example 3 in which less than 0.001 part by weight of graphite is mixed with 1 part by weight of the raw material is poor overall, and the production yield is extremely lowered as the activation time becomes longer. Further, it can be seen that Comparative Example 2 in which more than 0.3 parts by weight of graphite was mixed with 1 part by weight of the raw material had a small pore volume and was inferior in adsorption performance.

Further, a durability test of the activated carbons obtained in Examples 1 to 3 and Comparative Examples 1 to 3 and a BWC (butane working capacity) adsorption performance investigation were conducted by the apparatus shown in FIGS. 4 and 5.

FIG. 4 shows an evaporated fuel collecting device 1 which is usually called a canister. The evaporative fuel collecting apparatus 1 has a casing 2 thereof.
It is equipped with a pair of perforated plates 3 and 4 inside.
Thus, the inside of the casing 2 is separated into an activated carbon filling chamber 5, an evaporated fuel chamber 6 and an atmosphere chamber 7. Evaporative fuel chamber 6
On the other hand, the fuel tank 9
On the other hand, it is connected to the intake passage 12 of the internal combustion engine 11 via the evaporated fuel outflow port 10. The atmosphere chamber 7 is open to the atmosphere via the atmosphere port 13. Perforated plates 3, 4
Filters 14, 14 are arranged on the inner surface of the filter, and a large number of activated carbons 15 are filled between the filters 14, 14. At the time of adsorbing the evaporated fuel, the evaporated fuel generated in the fuel tank 9 is sent into the evaporated fuel chamber 6 through the evaporated fuel inflow port 8 and then into the activated carbon filling chamber 5 to be adsorbed on the activated carbon 15. Next, the air from which the fuel component has been removed is released from the atmospheric port 13 into the outside air. On the other hand, when desorbing the evaporated fuel, the outside air flows into the atmosphere chamber 7 through the atmosphere port 13, is then sent into the activated carbon filling chamber 5, and the evaporated fuel adsorbed by the activated carbon 15 is desorbed. Then, the air containing the fuel component is sent from the evaporated fuel outflow port 10 into the engine intake passage 12 through the evaporated fuel chamber 6, and is burned in the engine cylinder. This process was defined as one cycle, and this process was repeated 100 times.

FIG. 5 shows an experimental apparatus for investigating the adsorption capacity of activated carbon using n-butane as a fuel. This device is a flow meter
An n-butane tank 21 connected to the evaporated fuel inflow port 8 via 20, a compressed air cylinder 24 connected to the atmosphere port 13 via a flow meter 22 and a three-way switching valve 23, and an evaporated fuel outflow port 10 The valve 25 is provided. Using such a device, first, through the three-way switching valve 23, n-
Until butane flows out, that is, until the adsorption capacity is saturated,
The n-butane is supplied from the n-butane tank 21 into the activated carbon filling chamber 5, and then the weight of the evaporated fuel trap 1 is measured. Then, a fixed amount of compressed air is supplied from the compressed air cylinder 24 into the activated carbon filling chamber 5 to desorb n-butane, and then the weight of the evaporated fuel trap 1 is measured. The difference in these weights is called saturated BWC (butane working capacity) and represents the adsorption capacity of activated carbon 15.

Tables 2 and 3 show Examples 1 to 3 and Comparative Examples 1 to 1.
The amount of n-butane adsorbed on the activated carbon obtained in Example 3 (saturated BWC after initial and endurance) and the residual amount of gasoline component are shown.

From Table 2, it can be seen that the activated carbon of Comparative Example 1 in which graphite was not mixed with the raw material and Comparative Example 3 in which less than 0.001 part by weight of the raw material was mixed with 1 part by weight of the raw material had a slightly poor adsorption performance after endurance and 1 part by weight of the raw material. On the other hand, it can be seen that the activated carbon of Comparative Example 2 containing more than 0.3 parts by weight of graphite has poor adsorption performance as a whole.

Further, from Table 3, the activated carbons of Comparative Example 1 in which graphite was not mixed with the raw material and Comparative Example 3 in which less than 0.001 part by weight of graphite was mixed with 1 part by weight of the raw material had a high residual amount of n-butane and had a high adsorption capacity. It turned out to have an effect.

[Effects of the Invention] As described above, according to the method for producing activated carbon of the present invention, the pore distribution in the micro region with respect to the activation time moves to the larger pore radius side in the micro region, the adsorption performance is good, and the production is good. The yield is high and the durability performance can be improved.

[Brief description of the drawings]

FIG. 1 is a process diagram showing the activated carbon production process of the present invention, and FIG. 2 is a curve diagram showing the relationship between the pore radius and the differential pore volume of the activated carbon obtained in Example 1. FIG. 4 is a curve diagram showing the relationship between the pore radius of activated carbon obtained in Comparative Example 1 and the pore volume of the differential form, FIG. 4 is an explanatory diagram showing an evaporated fuel trap, and FIG. 5 is activated carbon. This is an experimental device for investigating the adsorption capacity of 1 ... Evaporative fuel collecting device, 3, 4 ... Perforated plate, 5 ... Activated carbon filling chamber, 9 ... Fuel tank, 12 ... Intake passage, 15 ...
Activated carbon.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Minami 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (56) Reference JP-A-1-103910 (JP, A)

Claims (1)

(57) [Claims] 1. A raw material of activated carbon and 0.
A method for producing activated carbon, which comprises mixing 001 to 0.3 parts by weight of graphite and a binder, followed by molding, carbonization and activation.