JPH02175608A - Production of active carbon - Google Patents

Abstract

PURPOSE:To obtain an active carbon having good absorbing characteristics after endurance in good yield by molding, carbonizing and activating a mixture of active carbon raw material, graphite and binder. CONSTITUTION:1 pts.wt. active carbon raw material (e.g. coal) is blended with 0.001-0.3 pts.wt. graphite and binder and the blend is in a desired form and then carbonized and activated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing activated carbon, and more particularly, to a method for producing activated carbon with good adsorption performance after durability without reducing production yield.

[Prior Art] A fuel vapor collection device using activated carbon is conventionally known in order to prevent fuel vapor from being released into the atmosphere. In this evaporated fuel collection device, evaporated fuel generated from a fuel system such as a fuel tank is temporarily adsorbed on activated carbon, and then outside air is introduced into the activated carbon to desorb the evaporated fuel adsorbed on the activated carbon. The evaporated fuel is sent into the engine cylinder and combusted.

Activated carbon used in such devices is made of particles containing carbon, usually made from coal or coconut shells, either as is, or by mixing the particles and a binder, forming them, and then heating and carbonizing them to release volatile substances. Pores are formed on the particle surface by carbonizing tar, etc. Next, by heating these particles in an oxidizing gas atmosphere such as water vapor, carbon dioxide gas, or air, the carbon is partially combusted, forming micropores within the pores that extend from the pores to the surroundings, and at the same time Activation is performed to form pores or micropores 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, the activation process involves reacting carbonized coal in an oxidizing gas atmosphere such as water vapor, carbon dioxide, or air over a relatively long period of time to form fine pores, that is, microscopic bores. is formed. The bore in this micro region is the pore radius or 2
Since it is very small (less than 0 Å), once gasoline components etc. are adsorbed, it becomes difficult to desorb, resulting in a decrease in adsorption performance. On the other hand, when the activation time is increased, the bore in the micro region gradually expands and the pore distribution in the micro region moves to the side with a larger pore radius, but the production yield decreases because the carbon content decreases.
This poses a problem of being very disadvantageous in terms of mass production and manufacturing costs.

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

[Means for Solving the Problems] In order to solve the above problems, the present invention mixes an activated carbon raw material, 0.001 to 0.3 parts by weight of graphite and a binder per 1 part by weight of the raw material, It is characterized by molding, carbonization, and activation. Coal and coconut shells are generally used as raw materials.

The blending amount of graphite is 0.0% graphite per 1 part by weight of the raw material.
When mixed in a proportion less than 0.001 parts by weight, the pore distribution in the micro region shifts only slightly to the side with a larger pore radius, and
．． If it is mixed in a proportion greater than 3 parts by weight, the adsorption performance will drop sharply, so the amount is in the range of 0.001 to 0.3 parts by weight.

[Function] In the method of the present invention, an activated carbon raw material, 0.001 to 0.3 parts by weight of graphite and a binder per 1 part by weight of the raw material are mixed, molded, carbonized, and activated. The pores formed in the micro region are distributed toward the side with a larger pore radius. This is considered to be because the pores of graphite remain as traditional pores with a pore radius of 20 Å or more. As a result, the desorbed air can diffuse deep into the pores during desorption, suppressing the accumulation of residue within the micropores and improving durability. In addition, since activation can be carried out in a short time, the production yield is also improved.

[Example] Hereinafter, an example of the present invention based on the activated carbon manufacturing process shown in FIG. 1 will be shown, but the present invention is not limited thereto.

Example 1 100 parts by weight of coal as raw materials, 10 parts by weight of graphite and 20 parts by weight of a binder were kneaded to give a diameter of 3 ++v.

It was extruded into a shape with a length of 10+ nm. This briquette was carbonized and further activated in an externally heated rotary furnace at a temperature of 950' C1 at a rate of 0.66 g/hour of steam per 1 g of carbonized coal to obtain activated carbon.

Example 2 Activated carbon was obtained in the same manner as in Example 1, except that graphite was changed to 0.5 parts 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] 100 parts by weight of raw material coal and 20 parts by weight of binder were kneaded and extruded into a shape with a diameter of 3 mm and a length of 10 mm. This briquette was carbonized and further activated in an externally heated rotary furnace at a temperature of 950° C. and an amount of water vapor of 0.66 g/hour per gram of carbonized coal to obtain activated carbon.

Comparative Example 2 In the same manner as in Comparative Example 1, 100 parts by weight of coal, 35 parts by weight of graphite, and 20 parts by weight of binder were molded, carbonized, and
Activated carbon was obtained.

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

The pore distribution of the activated carbon obtained in [Example] and Comparative Example 1 was measured by the methanol adsorption method, and the differential pore volume distribution for each of the three types of activation times is shown in Figures 2 and 3, respectively. . (Methanol adsorption measurement was performed using an automatic adsorption amount measuring device manufactured by Tanaka Scientific Instruments Manufacturing Co., Ltd.)
In addition, dV/dρo on the vertical axis in FIGS. 2 and 3
gR is a value obtained by differentiating the pore volume (V) with the logarithm of the pore radius (R).

From Figures 2 and 3, the activated carbon of Example 1 mixed with graphite has a pore radius distribution shifted to the larger side of the micro region compared to the activated carbon of Comparative Example 1 without graphite mixed. I understand. This shows that when the activation time is the same, activated carbon with a larger pore radius in the micro region can be produced in the example.

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

As is clear from Table 1, Examples 1 to 3 showed no adsorption performance, and there were no large differences in pore radius, pore volume, or production yield, and all had pore radius of 13. Whereas it takes 5 to 6 hours of activation time to exceed 0 people,
It can be seen that in Comparative Example 1 in which graphite was not mixed, the pore radius did not exceed 13.0 pores until 6 hours had passed. In addition, the production yields of Comparative Example 1 and Comparative Example 3 in which less than 0.001 parts by weight of graphite was mixed with 1 part by weight of the raw material were poor overall, and in particular, the longer the activation time, the lower the production yields were. I know that there is. Furthermore, 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 low pore volume and poor adsorption performance.

Furthermore, durability tests and BWC (butane working capacity) adsorption performance investigations of the activated carbons obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were conducted using the apparatus shown in FIGS. 4 and 5.

FIG. 4 shows an evaporative fuel collection device 1 commonly referred to as a canister. The evaporative fuel collection device 1 includes a pair of perforated plates 3.4 in its casing 2, and these perforated plates 3.4
As a result, the inside of the casing 2 is divided into an activated carbon filling chamber 5, an evaporated fuel chamber 6, and an atmospheric chamber 7. Evaporated fuel chamber 6
On the one hand, the fuel tank 9 is connected to the fuel tank 9 via the evaporated fuel inlet port 8.
On the other hand, it is connected to an intake passage 12 of an internal combustion engine 11 via an evaporative fuel outflow port 10. The atmospheric chamber 7 is open to the atmosphere via an atmospheric port 13. Filters ]4, ]4 are arranged on the inner surface of each porous plate 3.4, and a large number of activated carbons 15 are filled between these filters 14.14. During adsorption of evaporated fuel, evaporated fuel generated in the fuel tank 9 is sent into the evaporated fuel chamber 6 via the evaporated fuel inlet port 8, and then into the activated carbon filling chamber 5 where it is adsorbed by the activated carbon 5. The air from which the fuel components have been removed is then discharged into the outside air from the atmospheric port]3.

On the other hand, when the evaporated fuel is desorbed, outside air flows into the atmospheric chamber 7 through the atmospheric port 3, and is then sent into the activated carbon filling chamber 5, where the evaporated fuel adsorbed on the activated carbon 5 is desorbed. It will be done. The air containing fuel components passes through the evaporated fuel chamber 6 and exits from the evaporated fuel outflow port 10 to the engine intake passage 1.
2 and is combusted in the engine cylinder. This process is considered as one cycle, and this process is repeated 100 times.
I did the cycle.

FIG. 5 shows an experimental apparatus for examining the adsorption capacity of activated carbon using n-butane as fuel. This device is a flowmeter 2
n-butane tank 21 connected to the evaporated fuel inlet port 8 via 0, a compressed air cylinder 24 connected to the atmospheric port 13 via a flow meter 22 and a three-way switching valve 23, and connected to the evaporated fuel outlet port 10. A valve 25 is provided.

Using such a device, first, n-butane is supplied from the n-butane tank 21 into the activated carbon filling chamber 5 until a constant concentration of n-butane flows out through the three-way switching valve 23, that is, until the adsorption capacity is saturated. Then, the weight of the evaporative fuel collection device 1 is measured. Then the compressed air is transferred to compressed air cylinder 2.
4, a certain amount of activated carbon is supplied into the activated carbon filling chamber 5 to desorb n-butane, and then the weight of the evaporated fuel collection device 1 is measured.

The difference in these weights is called saturated BWC (butane working capacity) and represents the adsorption capacity of the activated carbon.

Tables 2 and 3 show Examples 1 to 3 and Comparative Examples 1 to 3.
The adsorption amount of n-butane (initial and post-durability saturated BWC) and the residual amount of gasoline components of the activated carbon obtained in the above are shown respectively.

Table 2 Table 2 shows that the activated carbon of Comparative Example 1, in which graphite was not mixed in 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 adsorption performance after durability. It can be seen that the activated carbon of Comparative Example 2, which contains more than 0.3 parts by weight of graphite per 1 part by weight of the raw material, has poor adsorption performance as a whole.

Furthermore, from Table 3, the activated carbons of Comparative Example 1 in which graphite was not mixed in 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.
It was found that the adsorption capacity was affected.

[Effects of the Invention] As explained above, in the method for producing activated carbon according to the present invention, the pore distribution in the micro region with respect to the activation time shifts to the side with a larger pore radius in the micro region, resulting in good adsorption performance and improved productivity. It also has a high yield and makes it possible to improve durability.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing the manufacturing process of the activated carbon of the present invention, and Fig. 2 shows the relationship between the fine 1'J/1 pore radius and differential pore volume of the activated carbon obtained in Example 1. A curve diagram, FIG. 3 is a curve diagram showing the relationship between the pore radius and differential pore volume of the activated carbon obtained in Comparative Example 1, and FIG. 4 is an explanatory diagram and FIG. Figure 5 shows an experimental device for investigating the adsorption capacity of activated carbon. DESCRIPTION OF SYMBOLS 1... Evaporated fuel collection device, 3, 4... Porous plate, 5... Activated carbon filling chamber, 9... Fuel tank, 12... Intake passage, 15... Activated carbon.

Claims (1)

[Claims] Production of activated carbon, characterized by mixing an activated carbon raw material, 0.001 to 0.3 parts by weight of graphite per 1 part by weight of the raw material, and a binder, followed by molding, carbonization, and activation. Method.