JP2013237595A - Activated carbon and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing activated carbon, capable of simply preparing activated carbon having a large pore volume and pore size suitable for adsorption/desorption of substances without relying on alkali activation.SOLUTION: A method for producing activated carbon comprises: a carbonizing step of carbonizing a fruit of Camellia japonica, as a raw material, containing potassium of ≥0.8% by an absolute dry mass rate of the raw material; and an activation step of activating the carbonized product obtained in the carbonizing step with at least one gas selected from steam, air and carbon dioxide, as activation gas.

Description

  The present invention relates to activated carbon and a method for producing the same.

  In recent years, the characteristics required for activated carbon have been increasingly advanced, and activated carbon having characteristics according to the use is required. The greatest feature of activated carbon is that the pores formed on the activated carbon surface adsorb and desorb (desorb and desorb) substances.

  The activation method for obtaining activated carbon by changing the carbonaceous raw material into a porous material includes alkali activation and gas activation. From the viewpoint of obtaining a pore diameter and a pore volume according to the substance to be adsorbed and desorbed, Then, activated carbon production by an alkali activation method is an effective means.

  This alkali activation method generally requires 2 to 5 times the weight of the alkali agent relative to the raw material weight, so (1) the number of steps is increased, (2) the life of the equipment is shortened due to alkali corrosion, (3) There are concerns such as the increase in scale of equipment related to alkali recovery and reuse. Due to these reasons, the manufacturing cost is high, and improvement is desired.

  Under the circumstances as described above, a slightly caking property containing a coal-based carbonaceous material and an alkali metal and / or an alkaline earth metal more than a weak caking property for imparting caking property and improving moldability. By using two types of coal with a coal-based carbonaceous material, a method for producing activated carbon that efficiently produces activated carbon is disclosed, and high decolorization performance and high strength are obtained (for example, Patent Document 1).

  Further, a method for producing activated carbon is disclosed in which wood is activated by water-derived water gas and volatile hydrocarbons generated by heating during carbonization while dispersing and carbonizing an alkali metal or the like in wood (for example, , See Patent Document 2).

  Furthermore, coconut husk activated carbon having a predetermined BET specific surface area is disclosed by using coconut husk as a raw material, carbonizing the coconut husk and activating water vapor (see, for example, Patent Document 3).

JP 2006-104002 A Japanese Patent No. 4142341 International Publication No. 2008-53919 Pamphlet

  However, in the conventional method using an alkali agent at a weight ratio of 2 times or more with respect to the raw material for alkali activation, the production cost is not suppressed as described above, and the activation degree (yield) is difficult to control. . In addition, since an alkali agent is added, the apparatus is easily corroded and there is a risk of explosion and the like. In general, it is only suitable for batch production, and continuous production is not possible.

  Also, among the above conventional techniques, in coal-based activated carbon using a coal-based carbonaceous material as a raw material, mesopores of several nm to several tens of nm are the main pore distribution, and the pore size is relatively large. Therefore, although it is suitable for adsorbing a substance having a large molecular size, it is not suitable for adsorbing a substance having a relatively small molecular size. In addition, since a material containing an alkali metal is required in addition to a coal-based material having weak caking properties or more due to the structure for production, a mixing process must be provided, and the process becomes complicated.

  On the other hand, coconut husk activated carbon obtained by carbonizing coconut husk as a raw material and activating it is rather considered to have a pore distribution with a pore size peak in the vicinity of 0.5 to 0.6 nm. In the range, the pore size is rather too small, and generally not suitable for adsorption of, for example, low molecular weight organic substances having a molecular size of about several nanometers. In this case, although not necessarily inferior in the adsorption / desorption property of the substance, in recent years, activated carbon having a property capable of satisfactorily adsorbing / desorbing a substance having such a molecular size has been demanded.

  The present invention has been made in view of the above situation, and an activated carbon having a large pore volume and a pore diameter suitable for adsorption / desorption of a substance (particularly a low molecular weight substance) can be easily produced without being activated by alkali. It is an object of the present invention to provide a method for producing activated carbon and to provide activated carbon having a large pore volume and a pore diameter suitable for adsorption / desorption of a substance (particularly a low molecular weight substance). .

Specific means for achieving the above object are as follows.
<1> A raw material containing 0.8% or more of potassium as a raw material mass ratio of potassium is used as a raw material, a carbonization step for carbonizing the raw material, and a carbide obtained in the carbonization step is converted into water vapor, air, and carbon dioxide. And an activation step of activating at least one gas selected from carbon as an activation gas.
<2> The method for producing activated carbon according to <1>, wherein the coconut is a squeezed cocoon oil or a coconut shell.
<3> The carbonization step is the method for producing activated carbon according to <1> or <2>, wherein carbonization is performed at a temperature of 600 ° C. or higher.
<4> The carbonization step is the method for producing activated carbon according to any one of <1> to <3>, wherein the carbonization is performed by changing the temperature increase rate in two stages to raise the temperature.

<5> The carbonization step is any one of <1> to <4>, wherein the carbonization is performed at a temperature increase rate in a temperature range of 200 ° C. or more and 600 ° C. or less at 2 ° C./min or more and 4 ° C./min or less. It is a manufacturing method of activated carbon as described in above.
<6> The activation process is the method for producing activated carbon according to any one of <1> to <5>, wherein the activation is performed at a temperature of 750 ° C. or higher.
<7> Any one of the items <1> to <6>, wherein the activation step is activated so that activated carbon having a content based on a mass of 5% or more based on a total mass of the metals in the group 1 of the periodic table is obtained. It is a manufacturing method of activated carbon as described in one.
<8> A washing step of performing at least one of a water washing treatment and a pickling treatment so that the metal content is 0.5% or less on a mass basis with respect to the total amount of activated carbon with respect to the activated carbon obtained through the activation step. The method for producing activated carbon according to any one of <1> to <7>, further including:

<9> Pork volume containing 0.8% or more of potassium in an absolute dry raw material mass ratio as a raw material, and the pore volume occupied by pores having a pore diameter of 0.7 nm or more is 65% of the total pore volume. % Of activated carbon.
<10> The activated carbon according to <9>, which has a peak pore diameter in which a differential pore volume peak value is 0.3 cm ³ / g · nm or more in a pore diameter range having a pore diameter of 0.7 nm or more.

According to the present invention, there is provided an activated carbon production method in which activated carbon having a large pore volume and having a pore diameter suitable for adsorption / desorption of a substance (particularly a low molecular weight substance) can be easily produced without using alkali activation. The Also,
ADVANTAGE OF THE INVENTION According to this invention, the activated carbon which has a large pore volume and a pore diameter suitable for adsorption / desorption of a substance (especially low molecular weight substance) is provided.

(A) is a graph showing the pore volume distribution of activated carbon in the vicinity of 15% yield of Example 1 in comparison with the comparative example, and (b) is a graph of the activated carbon in the vicinity of 10% yield of Example 1. It is a graph which shows pore volume distribution in contrast with a comparative example.

  Hereinafter, the manufacturing method of the activated carbon of the present invention will be described in detail, and the details of the activated carbon of the present invention will be described in detail through the description.

<Method for producing activated carbon>
The method for producing activated carbon according to the present invention uses, as a raw material, coconuts containing 0.8% or more of potassium by an absolutely dry raw material mass ratio, and carbonizes the raw material, and the carbide obtained in the carbonization step is treated with steam. And an activation step of activating at least one gas selected from air and carbon dioxide as an activation gas. The method for producing activated carbon of the present invention can be configured by further providing other steps such as a washing step for washing the carbide obtained in the carbonization step and activated carbon after activation, if necessary.

In the present invention, as a raw material used for carbonization in the carbonization step, particularly a coconut (plant raw material) containing a predetermined amount or more of potassium is used, and an alkali activation is performed on a carbide obtained from the coconut. Activated carbon having a pore size suitable for adsorption and desorption of a substance (particularly a low molecular weight substance) by performing gas activation (especially steam activation) instead of performing the activation. Is produced with a desired activation degree (yield).
Moreover, by not performing alkali activation, not only can the process of washing and removing excess alkali agent adhering to the activated carbon be omitted, the process can be simplified, but the recovery work of the alkali metal after washing is also unnecessary. Further, since alkali activation is not performed, corrosion of the device itself caused by exposure to an alkaline environment is prevented, and dangers such as explosions that are a concern in the presence of a large amount of alkali are also eliminated.

-Carbonization process-
In the carbonization step in the present invention, the raw material of the coconut containing 0.8% or more of potassium by an absolute dry raw material mass ratio is used as a raw material, and this raw material is carbonized. Therefore, in this step, charcoal carbides for producing activated carbon are obtained.

In the present invention, alkali activation in the activation step described later becomes unnecessary by using as a raw material the coconut that contains 0.8% or more of potassium in an absolutely dry raw material mass ratio. In the case of coal-based carbonaceous materials that have been used as raw materials for activated carbon in the past, in order to obtain porous activated carbon when using a high specific surface area and high pore volume, combined use of alkali activation treatment or secondary components including alkali metals Is indispensable. Moreover, for example, branches and trunks other than coconut husk and coconuts are less than an order of magnitude of potassium compared to coconuts, so if alkali activation is not performed at this amount of potassium, it is desirable. It takes a long time to obtain activated carbon with pores formed.
The fruit of the cocoon in the present invention contains 0.8% by mass or more of potassium, and it is considered that potassium is distributed homogeneously and highly dispersed in the tissue forming the fruit. Compared with the conventional method in which a large amount of an alkali agent is separately added to the raw material and activated in the process, the formation of uneven pores is prevented and the material is homogeneous and suitable for adsorption / desorption of substances. The pores can be obtained uniformly. Therefore, when activated carbon is produced, a pore distribution in which pores having a predetermined pore diameter are appropriately distributed is obtained, and the hardness is also increased. In other words, when the content of potassium is less than 0.8% by mass, it takes a long time to obtain activated carbon in which the desired homogeneous pores are uniformly formed.

  As the content of potassium contained in the raw material of the cocoon, it is more preferable in terms of pore formation, but 1.0% by mass or more is preferable for the same reason as described above. The upper limit of the potassium content is not necessarily limited, but is preferably 1.5% by mass or less from the viewpoint of cleaning after activation.

  Here, the fruit of a cocoon used as a raw material is a fruit that can be made into a cocoon that is a plant, and the fruit of the cocoon includes a seed part and a shell that wraps the outside. As the raw material, seeds and shells forming coconuts are preferable in that the potassium content is 1% by mass or more based on the mass of the absolutely dry raw material, and the branches and trunk parts of the pods contain potassium. The amount is less than 0.1% by mass in terms of the absolute dry raw material mass ratio, which is not preferable. As a raw material used in the carbonization step, coconuts or their seeds and outer shells may be used as they are, or oil squeezed potatoes may be used.

  The carbonization treatment can be suitably performed by heating and carbonizing the raw material in a temperature range of 600 ° C. or higher. In carbonizing the raw material, the prepared raw material may be carbonized by heating to a high temperature of 600 ° C. or more at a time, but preferably, a temperature range of about 200 to 300 ° C. once so that moisture in the raw material is discharged. It is preferable that the temperature is further increased for carbonization after the water is vaporized by holding at 200 to 300 ° C. and vaporizing moisture as necessary.

  The carbonization temperature for carbonizing the raw material is preferably 600 ° C. or higher, more preferably 800 ° C. or higher, and still more preferably 850 ° C. or higher. The upper limit of the carbonization temperature is preferably 1050 ° C. from the viewpoint of the durability of the apparatus. When the carbonization temperature is 600 ° C. or higher, it is easy to obtain a carbide in which crystallization of plant components (for example, cellulose and lignin) contained in the raw material is further advanced.

In the carbonization treatment, it is preferable to increase the temperature increase rate in multiple stages in the process until the temperature is increased to a desired temperature, and in particular, a method of increasing the temperature by changing the temperature increase rate in two stages. Is preferred. By raising the temperature stepwise, carbonization can be performed in accordance with the thermal decomposition of the raw material composition, which is effective in improving the performance of the finally obtained activated carbon. In particular,
When the raw material is heated, the moisture in the raw material is vaporized in the process of reaching around 200 ° C. and, if necessary, maintained at 200-300 ° C., and the discharge of moisture decreases. In the region, the thermal decomposition reaction of the components in the raw material proceeds. When the thermal decomposition of the raw material components begins, the raw material mass tends to decrease with the generation of combustible gas (for example, methane gas). Thus, in the temperature range where the raw material components are thermally decomposed to generate a combustible gas and the mass is reduced, it is preferable to raise the temperature at a relatively slow temperature increase rate in terms of improving the performance of the finally obtained activated carbon.

From the above viewpoint, in the carbonization step in the present invention, it is preferable that the temperature increase rate in the temperature range of 200 ° C. or more and 600 ° C. or less is 2 ° C./min or more and 4 ° C./min or less. By setting the rate of temperature rise in this temperature range to the above range, activated carbon having a large mass per unit volume can be easily obtained, and the adsorption and desorption of the substance possessed by the activated carbon is excellent.
The temperature increase rate can be switched by tracking the mass change of the raw material.

  In the carbonization step in the present invention, after the temperature increase rate in the temperature region of 600 ° C. or lower is set to the above range as described above, the temperature is further increased to a temperature exceeding 600 ° C. (preferably 800 ° C. or higher, more preferably 850 ° C. or higher). It is preferable to warm. The temperature increase rate in this case is not particularly limited, but since the change in the raw material composition is small in the temperature region exceeding 600 ° C., the temperature increase rate exceeds 4 ° C./min from the viewpoint of performing carbonization more efficiently. You may switch to the range. It is preferable that the temperature increase rate at this time is further 8 ° C./min or more.

  In the case where the carbonization is performed by raising the temperature to the above carbonization temperature, when the temperature is raised to a desired temperature (for example, 800 to 850 ° C.), that temperature (for example, 800 to 850 ° C.) is reached for a certain period of time. It is preferable to be held in By maintaining at a desired temperature for a certain time, carbonization can be performed more uniformly.

  In the present invention, the carbonization step is performed at a rate of temperature rise in the temperature range of 200 ° C. or higher and 600 ° C. or lower in the temperature range of 2 ° C./min or higher and 4 ° C./min or lower, and in the temperature range higher than 600 ° C. A mode in which the temperature rate is higher than 4 ° C./min, preferably 8 ° C./min or higher is preferable.

  The raw material can be carbonized using a rotary kiln and various furnaces (eg, fluidized bed furnace, fixed bed furnace, moving bed furnace, moving bed furnace, etc.). In the present invention, a continuous furnace that continuously inputs and removes raw materials can be applied, and a batch furnace that intermittently inputs and removes raw materials can also be applied.

  The heating means is not particularly limited as long as it is a means capable of heating to a desired temperature, and for example, electric heating, gas combustion heating, high-frequency induction heating, or the like can be applied.

-Activation process In the activation process in this invention, the carbide | carbonized_material obtained by the said carbonization process is activated by using at least 1 sort (s) of gas chosen from water vapor | steam, air, and a carbon dioxide as activation gas. In this step, activated carbon is obtained by gas activation of the raw material carbide.

  The gas activation in the present invention is performed using water vapor, air, carbon dioxide, or a mixed gas in which two or more of these are mixed (hereinafter also referred to as “water vapor”). Especially, the case where water vapor | steam is activated as activation gas is preferable. In this invention, the aspect by water vapor | steam is preferable from the point which activates with respect to the carbide | carbonized_material of the raw material in which the raw material contains potassium and potassium exists. By using water vapor with respect to the potassium-containing carbide, pores are easily formed and activated carbon having a large specific surface area is easily obtained.

  The activation process is preferably performed at a temperature of 750 ° C. or higher. When the temperature at the activation treatment (activation temperature) is 750 ° C. or higher, pores are easily formed, and a desired pore structure is easily obtained. The temperature for the activation treatment is preferably 800 ° C. or higher and more preferably 850 ° C. or higher for the same reason as described above.

  The time for activation treatment (activation time) varies depending on the activation temperature, the amount of water vapor introduced, the amount of carbide, etc., and is not particularly limited, but the activation time is preferably as short as possible and is 100 minutes or more. The range is preferably 300 minutes or less, and more preferably 100 minutes or more and 250 minutes or less.

  The activation is preferably performed so that activated carbon having a content of 5% or more on the mass basis with respect to the total mass of the metals of Group 1 of the periodic table is obtained. In the present invention, coconuts having a potassium concentration of 0.8% by mass or more are used as the raw material. For example, when the mass of the raw material (potassium content = 1%) is reduced to 1/5 by activation, conversely in the activated carbon The ratio of the potassium content in the water will be 5 times. That is, the activated carbon which shows the degree of activation and activates so that the amount of metals containing potassium may be 5% or more can easily obtain activated carbon having a pore diameter suitable for adsorption / desorption.

  The activation treatment can be performed by raising the temperature to the activation temperature and introducing water vapor or the like after reaching the activation temperature. The introduction of water vapor or the like is preferably continued from the start of the introduction until a predetermined activation time elapses, and the introduction is stopped after the activation time elapses.

  In the activation treatment, it is possible to fill a treatment device such as a rotary kiln that activates an inert gas such as nitrogen gas in advance before introducing steam or the like in order to suppress a reaction caused by oxygen, carbon dioxide, etc. in the air. preferable. By starting the activation after removing the reactive substance present in the vessel in advance, the activation reaction is efficiently performed and uniform pores are easily obtained.

-Washing process-
In addition to the above steps, the method for producing activated carbon of the present invention can be constituted by providing various washing steps for washing the carbide obtained through the carbonization step or the activated carbon obtained through the activation step. By washing, impurities adhering to the carbide and activated carbon are removed.

  Examples of the washing method include water washing treatment and pickling treatment. The water washing treatment is a washing treatment in which activated carbon is immersed in water for washing, and the pickling treatment is a chemical washing treatment in which the oxide is washed off by dipping in an acid solution. Among them, pickling treatment with an inorganic acid is preferable, and cleaning with hydrochloric acid that does not oxidize activated carbon is preferable. After washing with hydrochloric acid, it may be washed with water. Moreover, you may perform combining a water-washing process and a pickling process, such as performing a water-washing process and a pickling process repeatedly.

  When performing pickling treatment using hydrochloric acid, a method using an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 0.1% by mass to 3.0% by mass is preferable, and the hydrochloric acid concentration is 0.3% by mass to 1.0% by mass. The following is more preferable. When the hydrochloric acid concentration is 0.1% by mass or more, cleaning can be performed with an appropriate number of pickling times. Moreover, residual hydrochloric acid is restrained little because hydrochloric acid concentration is 3.0 mass% or less.

  About the washing | cleaning temperature, the higher one is preferable at the point of detergency, and it is usually 80 degreeC or more. Moreover, it is also a preferable aspect to immerse activated carbon in a boiling cleaning solution and wash it.

  In this invention, it is preferable to wash-process so that the metal content with respect to the total amount of activated carbon may be 0.5% or less with respect to the activated carbon obtained at the said activation process. In the present invention, the alkali is not necessarily excessively adhered by not performing the alkali activation, but from the viewpoint of reducing the amount of metal that becomes an impurity, it is preferably adjusted to the above range by washing. When the amount of metal is in the above range, for example, troubles such as impaired durability when used together with electrodes can be avoided.

  The metal content is determined by measuring atomic absorbance at a measurement wavelength of 766.5 nm using an atomic absorption photometer Z5310 (manufactured by Hitachi High-Technologies Corporation) after acid decomposition (complete dissolution) of activated carbon.

  When the pickling treatment is performed, it is preferable to further perform a deoxidation treatment. For example, after a pickling treatment using hydrochloric acid, the residual hydrochloric acid can be removed by contacting with an oxidizing gas. Specifically, it is preferable that the activated carbon gas-activated with water vapor or the like is pickled with hydrochloric acid or the like and then deoxidized in an oxidizing gas atmosphere. Examples of the oxidizing gas include oxygen, water vapor, and carbon dioxide gas.

  Furthermore, the activated carbon deoxidized as described above may be further heat-treated under an inert gas such as a rare gas or nitrogen gas in order to reduce the functional groups on the surface.

<Activated carbon>
Next, the activated carbon of the present invention will be described.
The activated carbon of the present invention is activated carbon made from coconuts containing 0.8% or more of potassium in an absolutely dry raw material mass ratio, and the pore volume occupied by pores having a pore diameter of 0.7 nm or more, It is comprised as 65% or more with respect to the total pore volume.

  As described above, the activated carbon of the present invention is made from coconuts containing 0.8% by mass or more of potassium, as described above. Therefore, the performance equivalent to alkali activation, that is, the pore volume is large, and the adsorption / desorption of substances. It has a pore size suitable for. Specifically, the activated carbon of the present invention satisfies the following pore diameter and its occupation ratio.

  The pore diameter is a value determined by a nitrogen adsorption method. For example, it can be measured by an automatic specific surface area / pore distribution measuring apparatus BELSORP-miniII (manufactured by Nippon Bell Co., Ltd.).

  The peak pore diameter of the activated carbon of the present invention is 0.7 nm or more. When the peak pore diameter is less than 0.7 nm, the pore diameter is too small and the low molecular weight substance cannot be adsorbed / desorbed smoothly. The peak pore diameter is preferably 0.9 nm or more from the viewpoint of adsorption / desorption. The upper limit of the peak pore diameter is desirably 2 nm.

The peak pore diameter is measured by an automatic specific surface area / pore distribution measuring device BELSORP-miniII (manufactured by Nippon Bell Co., Ltd.), and the pore diameter [nm] is plotted on one axis (for example, the horizontal axis) and the other axis ( For example, when the differential pore volume [cm ³ / g · nm] is taken on the vertical axis) and the relation line is drawn, the pore diameter indicates the maximum value of the differential pore volume.

  In addition, the pore volume occupied by pores having a pore diameter of 0.7 nm or more in the activated carbon of the present invention is 65% or more with respect to the total pore volume. If the occupied volume of pores with pore sizes suitable for the adsorption and desorption of substances is less than 65%, the adsorption and desorption ability of substances as activated carbon, especially the adsorption and desorption ability of substances of low molecular weight (for example, low molecular weight organic substances) is reduced. To do. The occupied volume is preferably 80% or more from the viewpoint of adsorption / desorption.

The pore volume of the activated carbon is a value calculated by the following method.
Using an automatic specific surface area / pore distribution measuring device BELSORP-miniII manufactured by Nippon Bell Co., Ltd., an adsorption isotherm representing the change in pressure and the amount of nitrogen adsorbed under a constant temperature (77K) is created, and this is used as an adsorption layer. The volume change is obtained from the change in the gradient of the relationship line converted into the nitrogen adsorption amount with respect to the thickness (that is, the change in the surface area), and the pore distribution is calculated. That is, the pore volume is determined directly from the pore diameter.

In the activated carbon of the present invention, the total content of metals (alkali metals) belonging to Group 1 of the periodic table is preferably 5% by mass or more based on the total mass of the activated carbon. When the total content is 5% by mass or more, the activation treatment is performed so that the amount of potassium in the raw material close to 1% is about 5 times, and formation of pores suitable for the adsorption / desorption of substances is performed. Can be expected. The total content of alkali metals is more preferably 1% by mass or more.
Of the alkali metals, the content of potassium (K) in the activated carbon is preferably in the above range.

The activated carbon of the present invention has a pore diameter in which the peak value of the differential pore volume in the pore volume distribution (differential pore volume peak value) is 0.3 cm ³ / g · nm or more in the range of 0.7 nm or more. It is preferable to have. Since many pores having a pore diameter of 0.7 nm or more exist, the substance can be adsorbed and desorbed satisfactorily. Especially, it is more preferable to have a pore diameter having a peak value of the differential pore volume of 0.3 cm ³ / g · nm or more in a range of 0.9 nm or more and 2 nm or less.

  The activated carbon of the present invention may be produced by any method as long as the pore volume occupied by pores having the above-mentioned pore diameters can be 65% or more of the total pore volume. It is produced by the method for producing activated carbon of the present invention described above.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

Example 1
-Production of activated carbon-
Using the raw materials shown in Table 1 below, the carbonization step, the activation step, and the washing step were performed by the following method under the conditions shown in Table 1 below to produce activated carbon.

(A) Carbonization process The raw oil mash (potassium content: 1.0% by mass) of the raw material, which is the raw material, is charged into a rotary kiln that can continuously perform the raw material charging and processing. The temperature was raised to 250 ° C. at 8 ° C./min. The raw materials shown in Table 1 below were used. Subsequently, after the temperature in the kiln reached 250 ° C., the raw material-derived water was held for about 30 minutes. Judgment that the discharge of moisture was completed was made by confirming that water vapor was not emitted from the exhaust pipe.

  Thereafter, the temperature raising rate was lowered to 4 ° C./min and the temperature was raised to 600 ° C., and then the temperature raising rate was raised to 8 ° C./min and the temperature was raised to 850 ° C. Furthermore, the temperature was maintained for about 30 minutes after reaching 850 ° C. In this way, the raw material was carbonized.

(B) Activation process The raw material by which the carbonization process was performed was thrown into the rotary kiln, and it heated up to the activation temperature shown in following Table 1 after nitrogen filling. After reaching the activation temperature, the introduction of water vapor into the kiln was started, and the introduction of water vapor was continued until the activation time shown in Table 1 below passed. And when activation time passed, introduction | transduction of water vapor | steam was stopped.

(C) Washing step After the activation step, the obtained activated carbon was washed with water and dilute hydrochloric acid. At this time, the cycle of pickling with boiling dilute hydrochloric acid after washing with boiling water was repeated until the pH of the washing solution reached around 7.

-Measurement and evaluation-
The following measurements and evaluations were performed for each activated carbon before and after washing after the activation step. The results of measurement and evaluation are shown in Table 1 below. Moreover, about the activated carbon obtained in Example 1, differential pore volume distribution is shown in FIG.

(1) Iodine adsorption performance The adsorption amount of iodine was measured by a method based on JIS K 01474.

(2) Methylene blue adsorption performance The amount of methylene blue adsorption was measured by a method according to JIS K 01474.

(3) Potassium content Approximately 1g of sampled activated carbon is weighed and subjected to thermal acid decomposition (complete dissolution) in the presence of sulfuric acid, nitric acid and perchloric acid, followed by sulfuric acid white smoke treatment and further acid decomposition with hydrochloric acid. And used as a sample. With respect to 50 ml of this sample, an atomic absorption photometer Z5310 (manufactured by Hitachi High-Technologies Corporation) was used to measure atomic absorbance at a measurement wavelength of 766.5 nm, thereby obtaining a potassium concentration.

(4) Specific surface area Using an automatic specific surface area / pore distribution measuring device BELSORP-mini II manufactured by Nippon Bell Co., Ltd., after creating an adsorption isotherm representing the change in pressure and nitrogen adsorption amount under constant temperature (77K) The volume change was measured from the gradient change (that is, the surface area change) of the relationship line plotted by converting this into the nitrogen adsorption amount with respect to the adsorption layer thickness, the pore distribution was calculated, and the specific surface area was obtained from the pore diameter. .

(5) Pore volume Using an automatic specific surface area / pore distribution measuring device BELSORP-mini II manufactured by Nippon Bell Co., Ltd., an adsorption isotherm representing the change in pressure and nitrogen adsorption amount under constant temperature (77K) is created. After that, this is converted into a nitrogen adsorption amount with respect to the adsorption layer thickness, the volume change is measured from the gradient change (that is, the surface area change) of the plotted relationship line, the pore distribution is calculated, and the pore volume is calculated from the pore diameter. Asked.

(6) Yield The ratio [%] of the mass of the obtained activated carbon to the mass of the raw material in the absolutely dry state was determined and used as the yield.

(7) Metal content ratio After the obtained activated carbon was acid-decomposed (completely dissolved), it was determined by measuring the atomic absorption at a measurement wavelength of 766.5 nm using an atomic absorption photometer Z5310 (manufactured by Hitachi High-Technologies Corporation).

(Examples 2-3)
In Example 1, activated carbon was prepared, measured and evaluated in the same manner as in Example 1 except that the activation temperature was changed from 850 ° C. to 750 ° C. and 650 ° C., respectively. The results of measurement evaluation are shown in Table 1 below.

Example 4
In Example 1, the oil squeezed potato used as a raw material (potassium content: 1.0 mass% [vs. dry raw material mass ratio]) was used as the outer shell of the coconut (potassium content: 1.2 mass% [ Activated carbon was prepared, measured, and evaluated in the same manner as in Example 1 except that it was replaced with the mass ratio of dry raw materials]). The results of measurement evaluation are shown in Table 1 below.

(Comparative Example 1)
In Example 1, after the carbonization step and before the transition to the activation step, the same procedure as in Example 1 was carried out except that the amount of potassium was adjusted by washing with water and dilute hydrochloric acid. Then, activated carbon for comparison was prepared and measured and evaluated. Here, the washing treatment was performed alternately with a washing treatment and a pickling treatment using dilute hydrochloric acid while boiling water or a washing solution used for them. This washing treatment was repeated until the pH of the washing solution became around 7. In this way, the amount of potassium contained before the activation step was reduced, and oil squeezed rice cake (potassium content: 0.3% by mass [absolute dry material mass ratio]) having a low potassium content was used as an example. .
The results of measurement evaluation are shown in Table 1 below.

(Comparative Example 2)
Using the raw materials shown in Table 1 below, a carbonization step, an activation step (including alkali addition), and a washing step were performed by the following method under the conditions shown in Table 1 below to produce a comparative activated carbon.

(I) Carbonization process The raw oil mash (potassium content: 1.0% by mass) of the raw material, which is the raw material, is put into a rotary kiln where the raw material can be continuously charged and treated, and the rate of temperature increase is first introduced. The temperature was raised to 250 ° C. at 8 ° C./min. The raw materials shown in Table 1 below were used. Subsequently, after the temperature in the kiln reached 250 ° C., the raw material-derived water was held for about 30 minutes. Judgment that the discharge of moisture was completed was made by confirming that water vapor was not emitted from the exhaust pipe.
Thereafter, the temperature raising rate was lowered to 4 ° C./min and the temperature was raised to 600 ° C., and then the temperature raising rate was raised to 8 ° C./min and the temperature was raised to 850 ° C. Furthermore, the temperature was maintained for about 30 minutes after reaching 850 ° C. In this way, the raw material was carbonized.

(Ii) Cleaning step The carbide obtained in the carbonization step was cleaned using water and dilute hydrochloric acid. The washing treatment is alternately carried out with a water washing treatment and a pickling treatment using dilute hydrochloric acid while boiling water or a washing solution used for these. This was repeated until the pH of the washing solution reached around 7.

(Iii) Activation Step Next, the washed carbide was impregnated in a potassium hydroxide aqueous solution and dried to adjust the potassium content to be equal to that in Example 1. The adjusted carbide was put into a rotary kiln, filled with nitrogen, and then heated to the activation temperature shown in Table 1 below. After reaching the activation temperature, the introduction of water vapor into the kiln was started, and the introduction of water vapor was continued until the activation time shown in Table 1 below passed. And when activation time passed, introduction | transduction of water vapor | steam was stopped.

(Iv) Washing process After finishing the activation process, the obtained activated carbon was washed with water and dilute hydrochloric acid. At this time, the operation cycle of pickling with boiling dilute hydrochloric acid after washing with boiling water was repeated until the pH of the washing solution reached around 7.
A comparative activated carbon was produced as described above.

-Measurement and evaluation-
Each activated carbon before and after washing after the activation step was measured and evaluated in the same manner as in Example 1. The results of measurement and evaluation are shown in Table 1 below.

(Comparative Example 3)
In Comparative Example 2, the amount of potassium hydroxide aqueous solution added to activate the alkali was compared with that of Comparative Example 2 except that the potassium content was twice that of Example 1. Activated carbon was prepared, measured and evaluated. The results of measurement and evaluation are shown in Table 1 below.

As shown in Table 1, in Examples, activated carbon having a structure and performance equivalent to alkali activation could be produced by gas activation using strawberries as raw materials. Specifically, the produced activated carbon has a larger occupation ratio of pore volume and pore diameter of φ0.7 nm or more than the activated carbon for comparison with the same activation time, and the adsorption / desorption property to the substance. It was possible to secure a specific surface area of 1200 m ² / g or more with a good yield of 15%.
Further, in the present invention, since no alkali agent is used, the concern about the corrosion of the apparatus and the risk are kept small, and continuous production is possible.

Specific means for achieving the above object are as follows.
<1> 600 kg or more of dried koji coconut oil containing potassium in an absolute dry material mass ratio is used as a raw material, and the temperature is raised by changing the heating rate in two stages to 600 ℃ and carbonization step of carbonizing the raw material at a temperature above the carbide obtained in the carbonization step, the activating step of activating the air Mizu蒸as an activator gas, a method for producing activated carbon including.

< 2 > The carbonization step is the method for producing activated carbon according to <1 >, wherein the carbonization is performed at a temperature increase rate in a temperature range of 200 ° C. to 600 ° C. at 2 ° C./min to 4 ° C./min.
< 3 > The activation step is the method for producing activated carbon according to <1> or <2>, wherein activation is performed at a temperature of 750 ° C. or higher.
< 4 > Any one of the above <1> to < 3 >, wherein the activation step is activated so that activated carbon having a content based on a mass of 5% or more with respect to the total mass of the metal of Group 1 of the periodic table is obtained. It is a manufacturing method of activated carbon as described in one.
< 5 > A washing step of performing at least one of a water washing treatment and a pickling treatment so that the metal content is 0.5% or less on a mass basis with respect to the total amount of activated carbon with respect to the activated carbon obtained through the activation step. The activated carbon production method according to any one of <1> to < 4 >, further including:

< 6 > A cocoon coconut oil squeezed or a coconut husk containing 0.8% or more of potassium in an absolute dry material mass ratio is used as a raw material, and a pore having a pore diameter of 0.7 nm or more The activated carbon has an occupied pore volume of 65% or more of the total pore volume.
< 7 > The activated carbon according to < 6 >, wherein the differential pore volume peak value is 0.3 cm ³ / g · nm or more in a pore diameter range having a pore diameter of 0.7 nm or more.

<Method for producing activated carbon>
The method for producing activated carbon according to the present invention uses cocoon coconut oil squeezed or coconut shell containing 0.8% or more of potassium by dry mass as a raw material, and the heating rate is changed in two stages. and allowed to carbonization step of carbonizing the raw material in heated 600 ° C. or higher temperature is, the carbide obtained in the carbonization step, and is configured by providing the activation step of activating the air Mizu蒸as an activator gas. The method for producing activated carbon of the present invention can be configured by further providing other steps such as a washing step for washing the carbide obtained in the carbonization step and activated carbon after activation, if necessary.

In the present invention, as a raw material used for carbonization in the carbonization step, a coconut oil squeezed coconut oil or a coconut husk containing a predetermined amount or more of potassium is used. against carbides obtained from, rather than performing alkali activation, by performing the particular steam vehicle active as gas activation, the performance of the alkali activation equivalent, i.e. the pore volume is large, materials (substances especially low molecular weight) Activated carbon having a pore size suitable for the adsorption and desorption of is produced with a desired activation degree (yield).
Moreover, by not performing alkali activation, not only can the process of washing and removing excess alkali agent adhering to the activated carbon be omitted, the process can be simplified, but the recovery work of the alkali metal after washing is also unnecessary. Further, since alkali activation is not performed, corrosion of the device itself caused by exposure to an alkaline environment is prevented, and dangers such as explosions that are a concern in the presence of a large amount of alkali are also eliminated.

-Carbonization process-
In the carbonization step in the present invention, the raw material of the coconut coconut oil squeezed or the coconut shell containing 0.8% or more of potassium by dry mass is used as a raw material, and this raw material is carbonized. Therefore, in this step, squeezed coconut oil or coconut shell carbide for producing activated carbon is obtained.

In the present invention, alkali activation in the activation step described later is performed by using, as a raw material, squeezed persimmon oil of persimmon oil or potassium persimmon shell containing 0.8% or more of potassium in an absolute dry raw material mass ratio. Is no longer necessary. In the case of coal-based carbonaceous materials that have been used as raw materials for activated carbon in the past, in order to obtain porous activated carbon when using a high specific surface area and high pore volume, combined use of alkali activation treatment or secondary components including alkali metals Is indispensable. Moreover, for example, branches and trunks other than coconut husk and coconuts are less than an order of magnitude of potassium compared to coconuts, so if alkali activation is not performed at this amount of potassium, it is desirable. It takes a long time to obtain activated carbon with pores formed.
In the present invention , squeezed persimmon oil of persimmon seed or persimmon seed shell contains 0.8% by mass or more of potassium, and potassium is distributed homogeneously and highly dispersed in the tissue forming the fruit. Therefore, when activation treatment is performed in the activation step described later, compared to the conventional method in which a large amount of alkaline agent is added to the raw material and activated, the uneven distribution of the formed pores is prevented. Uniform pores suitable for the adsorption and desorption of substances can be obtained uniformly. Therefore, when activated carbon is produced, a pore distribution in which pores having a predetermined pore diameter are appropriately distributed is obtained, and the hardness is also increased. In other words, when the content of potassium is less than 0.8% by mass, it takes a long time to obtain activated carbon in which the desired homogeneous pores are uniformly formed.

As the content of potassium contained in the squeezed coconut oil or coconut shell , which is the raw material, the more preferable in terms of pore formation, it is 1.0 mass% or more for the same reason as above. Is preferred. The upper limit of the potassium content is not necessarily limited, but is preferably 1.5% by mass or less from the viewpoint of cleaning after activation.

Here, the fruit of a cocoon used as a raw material is a fruit that can be made into a cocoon that is a plant, and the fruit of the cocoon includes a seed part and a shell that wraps the outside. As the raw material, seeds and shells forming coconuts are preferable in that the potassium content is 1% by mass or more based on the mass of the absolutely dry raw material, and the branches and trunk parts of the pods contain potassium. The amount is less than 0.1% by mass in terms of the absolute dry raw material mass ratio, which is not preferable. As a raw material used in the carbonization step, coconuts or their seeds and outer shells are used as they are , and oil squeezed cocoons are used.

Carbonization process, the raw material is heated in a temperature range of above 600 ° C. you carbonization. In carbonizing the raw material, the prepared raw material may be carbonized by heating to a high temperature of 600 ° C. or more at a time, but preferably, a temperature range of about 200 to 300 ° C. once so that moisture in the raw material is discharged. It is preferable that the temperature is further increased for carbonization after the water is vaporized by holding at 200 to 300 ° C. and vaporizing moisture as necessary.

Carbonization temperature for raw materials and carbonization, and 600 ° C. or higher, more preferably at least 800 ° C., more preferably at 850 ° C. or higher. The upper limit of the carbonization temperature is preferably 1050 ° C. from the viewpoint of the durability of the apparatus. When the carbonization temperature is 600 ° C. or higher, it is easy to obtain a carbide in which crystallization of plant components (for example, cellulose and lignin) contained in the raw material is further advanced.

In the carbonization treatment, it is preferable that the temperature increase rate is divided into multiple stages in the process until the temperature is increased to a desired temperature. In particular, in the present invention, the temperature increase rate is changed in two stages. NoboriAtsushisu Ru. By raising the temperature stepwise, carbonization can be performed in accordance with the thermal decomposition of the raw material composition, which is effective in improving the performance of the finally obtained activated carbon. In particular,
When the raw material is heated, the moisture in the raw material is vaporized in the process of reaching around 200 ° C. and, if necessary, maintained at 200-300 ° C., and the discharge of moisture decreases. In the region, the thermal decomposition reaction of the components in the raw material proceeds. When the thermal decomposition of the raw material components begins, the raw material mass tends to decrease with the generation of combustible gas (for example, methane gas). Thus, in the temperature range where the raw material components are thermally decomposed to generate a combustible gas and the mass is reduced, it is preferable to raise the temperature at a relatively slow temperature increase rate in terms of improving the performance of the finally obtained activated carbon.

- The activation step in the activation process the present invention, the carbide obtained in the carbonization step, the activation treatment gas Mizu蒸as an activator gas. In this step, activated carbon is obtained by gas activation of the raw material carbide.

The gas activation in the present invention is performed using water vapor, air, carbon dioxide, or a mixed gas in which two or more of these are mixed (hereinafter also referred to as “water vapor”). Above all, we activate the steam as an activator gas in the present invention. In this invention, the aspect by water vapor | steam is preferable from the point which activates with respect to the carbide | carbonized_material of the raw material in which the raw material contains potassium and potassium exists. By using water vapor with respect to the potassium-containing carbide, pores are easily formed and activated carbon having a large specific surface area is easily obtained.

<Activated carbon>
Next, the activated carbon of the present invention will be described.
The activated carbon of the present invention is activated carbon made from squeezed coconut cocoon oil or coconut husk containing 0.8% or more of potassium by dry mass as a raw material, and has a pore diameter of 0.7 nm. The pore volume occupied by the above pores is configured to be 65% or more with respect to the total pore volume.

As described above, the activated carbon of the present invention is obtained by using a cocoon coconut oil squeezed coconut oil containing 0.8% by mass or more of potassium or a coconut husk as a raw material. That is, the pore volume is large and the pore diameter is suitable for the adsorption and desorption of substances. Specifically, the activated carbon of the present invention satisfies the following pore diameter and its occupation ratio.

Claims (10)

A carbonization step of carbonizing the raw material, using as a raw material the coconut that contains 0.8% or more of an absolute dry raw material mass ratio of potassium;
An activation step of activating the carbide obtained in the carbonization step with at least one gas selected from water vapor, air, and carbon dioxide as an activation gas;
The manufacturing method of activated carbon containing.   The method for producing activated carbon according to claim 1, wherein the coconut is squeezed cocoon oil or a coconut shell.   The method for producing activated carbon according to claim 1 or 2, wherein in the carbonization step, carbonization is performed at a temperature of 600 ° C or higher.   The said carbonization process is a manufacturing method of the activated carbon of any one of Claims 1-3 which carbonize by changing a temperature increase rate into two steps and heating up.   5. The activated carbon according to claim 1, wherein the carbonization step is carbonized at a temperature rising rate in a temperature range of 200 ° C. or more and 600 ° C. or less at 2 ° C./min or more and 4 ° C./min or less. Production method.   The said activation process is a manufacturing method of the activated carbon of any one of Claims 1-5 which performs activation at the temperature of 750 degreeC or more.   The said activation process activates so that activated carbon with which content with respect to the total mass of the metal of a periodic table 1 group is 5% or more on a mass basis is obtained. A method for producing activated carbon.   The activated carbon obtained through the activation step further includes a washing step of performing at least one of a water washing treatment and a pickling treatment so that the metal content is 0.5% or less on a mass basis with respect to the total amount of activated carbon. The manufacturing method of activated carbon of any one of Claims 1-7.   Produced from coconuts containing 0.8% or more of an absolute dry material mass ratio of potassium, the pore volume occupied by pores having a pore diameter of 0.7 nm or more is 65% or more of the total pore volume. A certain activated carbon. The activated carbon according to claim 9, which has a peak pore diameter in which a differential pore volume peak value is 0.3 cm ³ / g · nm or more in a pore diameter range having a pore diameter of 0.7 nm or more.