CN109923066B - Spherical activated carbon and method for producing the same - Google Patents

Abstract

The spherical activated carbon of the present invention is an integrally formed spherical activated carbon. The average particle diameter of the spherical activated carbon is 1.5 mm or more and 4.0 mm or less, and the pore volume when the pore diameter of the spherical activated carbon is 50 nm or more and 10000 nm or less is in the range of 0.01 ml/g or more and 0.24 ml/g or less.

Description

Spherical activated carbon and method for producing the same

technical field

The present invention relates to a spherical activated carbon and a manufacturing method of the spherical activated carbon.

Background technique

In the chemical industry, activated carbon is used for separation process, purification, catalyst or solvent recovery, and further, it is widely used for drainage treatment, pollution countermeasures, or medical use related to global environmental pollution problems.

For example, Non-Patent Document 1 discloses powdered activated carbon and granular activated carbon having an average particle diameter of about several millimeters.

In addition, activated carbon using a heavy hydrocarbon oil such as petroleum tar and ethylene tar as a raw material (Patent Document 1) and activated carbon using a resin as a raw material (Patent Document 2) are known.

prior art literature

Patent Literature

Patent Document 1: Japanese Laid-Open Patent Publication "Japanese Patent Laid-Open No. 2005-119947"

Patent Document 2: Japanese Laid-Open Patent Publication "Japanese Unexamined Patent Publication No. 2000-233916" Non-patent Document

Non-Patent Document 1: Yuzo Sanada and two others, "Basics and Applications of New Activated Carbons", Kodansha Co., Ltd., March 1, 1992

SUMMARY OF THE INVENTION

Invention to solve problem

Furthermore, when activated carbon is used, reduction of pressure loss and suppression of dust are required.

When an apparatus such as a column is filled with activated carbon and a fluid containing a target substance at a certain concentration is circulated and used, in order to maximize the effect per unit volume of the target substance, activated carbon particles need to be densely packed.

However, when the particle size of the activated carbon is small, or when the amount of dust generated by the activated carbon is large, the voids between the particles of the activated carbon are blocked. In addition, in these cases, the pressure loss increases due to clogging of the device filter or the like, and as a result, it is considered that the load on the device increases. In addition, when activated carbon is used to process a fluid with a large flow rate, there is a possibility that the activated carbon having a small particle size or the generated dust may scatter.

In addition, when the activated carbon and the target substance are separated from each other after contacting the activated carbon with a fluid (gas or liquid) containing the target substance, treatment such as filtration is required. However, if the particles of activated carbon are small or the amount of dust generated is large, it takes time and cost to separate them.

In particular, since the particle size of the above-mentioned powdery activated carbon is basically small, when it is filled in an apparatus and used, the pressure loss becomes large, and the amount of fluid treatment is also limited.

In addition, in the case of using powdered activated carbon in this way, there is a fear that the powder may scatter when a large flow rate of fluid is processed.

On the other hand, if it is a granular activated carbon with an average particle diameter of about several mm, the pressure loss at the time of filling can be reduced, and it can be considered that a large flow rate of fluid treatment can be performed.

However, conventionally, in the manufacturing method of granular activated carbon, the system in which powdered carbon and a binder are mixed and granulated into a granular form is generally used. That is, the granular activated carbon obtained by the conventional manufacturing method is not an integrally molded activated carbon. From this, since the strength of the conventional granular activated carbon is weak, when such granular activated carbon is packed in an apparatus and used, a large amount of dust is generated, and it is considered that separation from the fluid is difficult.

Moreover, since coconut shell charcoal etc. are generally used for the conventional granular activated carbon, it is considered that there are many impurities, and it is considered that there are problems such as elution of impurities other than dust.

From such a viewpoint, development of an activated carbon capable of suppressing pressure loss and dust has been demanded.

Technical solutions

The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, they have discovered the fact that the present invention can be suppressed by integrally-molded spherical activated carbon having a particle size of about several mm.

That is, the present invention provides spherical activated carbon which is an integrally formed spherical activated carbon having an average particle diameter of 1.5 mm or more and 4.0 mm or less, and has a pore volume of 0.01 ml/g or more in a range of pore diameters of 50 nm to 10000 nm. The range below 0.24ml/g.

Furthermore, this invention provides the manufacturing method of the spherical activated carbon which has the above-mentioned characteristics.

beneficial effect

According to the present invention, an activated carbon capable of suppressing pressure loss and dust can be provided.

Detailed ways

Hereinafter, one Embodiment of the spherical activated carbon of this invention is demonstrated concretely.

[Spherical Activated Carbon]

The spherical activated carbon of the present embodiment (hereinafter also simply referred to as "spherical activated carbon") has an average particle diameter of 1.5 mm or more and 4.0 mm or less, and a pore volume in the range of 50 nm or more and 10000 nm or less, 0.01 ml/g or more and 0.24 ml/g or less. In addition, the detailed description of a pore diameter and a pore volume is described later.

In this specification, spherical activated carbon means spherical activated carbon. The spherical degree of the spherical activated carbon is not particularly limited, but the aspect ratio is preferably 0.7 or more, more preferably 0.8 or more, and still more preferably 0.9 or more. The aspect ratio is the ratio of the short diameter to the long diameter. The major axis and the minor axis are obtained by a known method, for example, as the average value of the maximum length and the minimum length in the projected image of the spherical activated carbon. The closer the aspect ratio is to 1, the closer the spherical activated carbon is to a true sphere. In addition, when the aspect ratio of the spherical activated carbon is 0.7 or more, when the spherical activated carbon is used, the abrasion caused by the collision of the spherical activated carbon particles can be further reduced, so that the generation of dust can be sufficiently suppressed.

The spherical activated carbon of the present embodiment is integrally formed spherical activated carbon. "Integrated spherical activated carbon" means an activated carbon that is molded as primary particles and has a spherical shape. The spherical activated carbon of the present embodiment has a pore diameter and a pore volume to be described later, and therefore is also referred to as activated carbon having porosity and spherical primary particles. For example, the spherical activated carbon of the present embodiment is superior in mechanical strength as compared with the conventional spherical activated carbon such as a sintered body of aggregated particles. For example, compared with the conventional spherical activated carbon, the spherical activated carbon of this embodiment has a high crushing strength, or has a low water vibration abrasion rate.

(The average particle size)

From the viewpoint of suppressing an increase in the pressure loss of the packed layer of the spherical activated carbon, the lower limit of the average particle diameter of the spherical activated carbon of the present embodiment is 1.5 mm or more, preferably 1.7 mm or more, more preferably 1.8 mm, and still more preferably 2.0mm or more. In addition, the upper limit is 4.0 mm or less, preferably 3.5 mm or less, and more preferably 3.0 mm or less, from the viewpoint of achieving sufficient contact between the spherical activated carbon and the fluid in the packed layer. By making the average particle diameter within this range, the interparticle voids of the spherical activated carbon can be sufficiently increased. Therefore, in the case of such spherical activated carbon, the pressure loss can be sufficiently reduced when the spherical activated carbon is packed in a device such as a column or a separation tower and brought into contact with a fluid containing a target substance.

In the present embodiment, the average particle diameter of the spherical activated carbon can be evaluated in accordance with JIS K 1474. That is, based on the result obtained by the operation of JIS K 1474, the particle size integration line graph of spherical activated carbon was produced. From the intersection of the vertical line at the 50% point of the horizontal axis and the particle size cumulative line graph, the horizontal line is drawn on the vertical axis to obtain the mesh size (mm) of the sieve indicated by the intersection. The value of this mesh is made into the average particle diameter of spherical activated carbon.

(pore size)

In this specification, the pore diameter means the pore diameter of the pores that the spherical activated carbon has. In the present embodiment, the pore diameter and the pore volume can be measured by, for example, a well-known mercury intrusion method. In addition, the pore diameter and the pore volume can be adjusted according to, for example, the properties of the crosslinked heavyweight asphalt described later, the type of additives in the crosslinked heavyweight asphalt, conditions for extracting the additives with a solvent, and the like.

(pore volume)

In the present specification, the pore volume means the volume of pores within a specific pore diameter range of the activated carbon.

The lower limit value of the pore volume of the spherical activated carbon of the present embodiment in the range of 50 nm or more and 10000 nm or less is 0.01 ml/g or more from the viewpoint of suppressing the decrease in productivity of the production method of spherical activated carbon described later. , preferably 0.02 ml/g or more, more preferably 0.03 ml/g or more, still more preferably 0.05 g/ml or more. In addition, from the viewpoint of preventing a reduction in the crushing strength of the spherical activated carbon, the upper limit is 0.24 ml/g or less, preferably 0.22 ml/g or less, more preferably 0.20 ml/g or less, and still more preferably 0.18 ml/g the following.

In addition, from the viewpoint of suppressing the reduction in productivity of the spherical activated carbon, the lower limit of the pore volume of the spherical activated carbon of the present embodiment in the range of 10 nm or more and 10000 nm or less is 0.01 ml/g or more, preferably 0.02 ml/g or more, more preferably 0.03 ml/g or more, still more preferably 0.04 ml/ or more. In addition, from the viewpoint of preventing the crushing strength of the spherical activated carbon from decreasing, the upper limit is 0.28 ml/g or less, preferably 0.27 ml/g or less, more preferably 0.26 ml/g or less, and still more preferably 0.25 ml/g , most preferably 0.24ml/g or less.

According to the present embodiment, by making the spherical activated carbon satisfy the above-mentioned range, necessary pores can be sufficiently formed at the time of infusibility described later, so that infusibility can be efficiently performed, and spherical activated carbon can be produced. In addition, the increase in the pore volume that is difficult to relate to the adsorption capacity of the spherical activated carbon can be suppressed, so that the density of the spherical activated carbon increases and the performance per unit volume of the spherical activated carbon improves.

In this embodiment, the pore volume can be evaluated by, for example, a well-known mercury intrusion method. (Crush Strength)

Since the spherical activated carbon of the present embodiment is primary particles, it has higher mechanical strength than the conventional spherical activated carbon obtained by sintering the aggregated particles. The crushing strength of the spherical activated carbon of the present embodiment is preferably 1.20 kg/piece or more, more preferably 1.25 kg/piece or more, and further preferably 1.30 kg/piece. The crushing strength should just have a sufficient size according to the use of spherical activated carbon, for example, and may be 10.0 kg/piece or less, for example.

The crushing strength can be measured by the following method. That is, sample particles (for example, 32 particles) of spherical activated carbon were randomly extracted, and the hardness at the moment when the sample particles were crushed was measured using a simple granular hardness tester (manufactured by Tsutsui Riken Co., Ltd.). Then, the maximum value and the minimum value among the measured values of hardness are excluded, and the average value of the remaining measured values (for example, the measured values of 30 grains) is calculated, and this is used as the crushing strength of the spherical activated carbon.

(dust amount)

In this specification, dust means the fine powder contained in spherical activated carbon. In addition, the amount of dust means the amount of the dust, specifically, the amount calculated by the measurement of the amount of dust described later.

In the present embodiment, from the viewpoint of suppressing an increase in pressure loss in the packed layer of the spherical activated carbon and from the viewpoint of sufficiently expressing the separation ability of the spherical activated carbon, the amount of dust contained in 1 g of the spherical activated carbon is preferably 2000 μg or less, and more It is preferably 1500 μg or less, more preferably 1200 μg or less, and most preferably 1000 μg or less. The smaller the amount of dust, the more preferable, and the lower limit thereof may be 0 μg or more.

The dust amount of the spherical activated carbon of this embodiment can be measured by the specific method mentioned later. The amount of dust can be reduced by, for example, a manufacturing method realized by integral molding.

(vibration wear rate in water)

When the spherical activated carbon is put into water and vibrated in the water, the spherical activated carbon collides with each other, and the spherical activated carbon is scraped and peeled off. In this embodiment, the vibration abrasion rate in water is calculated from the amount of the spherical activated carbon peeled off at this time. Specifically, the underwater vibration wear rate can be calculated from the following equation.

Vibration wear rate in water (%)=(A-B)/A×100(%)...(Formula 1)

A: Mass of spherical activated carbon before vibration in water (g)

B: Mass (g) of spherical activated carbon after vibration in water

The vibration abrasion rate in water of the spherical activated carbon of the present embodiment is preferably 5% or less, and more preferably 4.5% or less. In addition, as the vibration abrasion rate in water is lower, the intensity|strength of spherical activated carbon becomes large, and the dust quantity which generate|occur|produces by spherical activated carbon collides with each other becomes small.

(specific surface area)

The specific surface area was obtained by allowing the substance to be evaluated to adsorb gas molecules and obtained from the ratio of the amount of the adsorbed gas molecules to the adsorption cross-sectional area of the gas molecules. Specifically, the nitrogen adsorption amount was calculated by the BET method, and the specific surface area was obtained by setting the adsorption cross-sectional area of nitrogen molecules to 0.162 nm ² . It should be noted that the specific surface area is sometimes referred to as the specific surface area (SSA).

The specific surface area of the present embodiment is the specific surface area when nitrogen is used for gas molecules and nitrogen is adsorbed on spherical activated carbon at liquid nitrogen temperature. The specific surface area can be adjusted according to, for example, the degree of activation described later.

From the viewpoint of exerting the adsorption function of the spherical activated carbon, the specific surface area of the spherical activated carbon of the present embodiment is preferably 100 m ² /g or more, more preferably 300 m ² /g or more, and still more preferably 400 m ² /g or more. It is considered that when the specific surface area is 100 m ² /g or more, the adsorption function by the spherical activated carbon can be sufficiently exhibited. From the above-mentioned viewpoints, the larger the specific surface area, the more preferable it is, but it may be in a range in which the desired adsorption function of the spherical activated carbon can be sufficiently obtained, for example, 4000 m ² /g or less.

The spherical activated carbon of this embodiment may carry other substances. Examples of other substances include known substances that can be added to activated carbon, such as acids, bases, and metals. Specific examples of the acid include nonvolatile acids such as phosphoric acid and sulfuric acid, and organic acids such as citric acid and malic acid. Moreover, as a base, potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide etc. are mentioned specifically, for example. In addition, specific examples of the metal include transition elements such as platinum, silver, iron, and cobalt, compounds thereof, and the like.

As described above, in the spherical activated carbon of the present embodiment, the amount of dust contained in 1 g of the spherical activated carbon is preferably 2000 μg or less.

Furthermore, the vibration abrasion rate in water of the spherical activated carbon of the present embodiment is preferably 5% or less.

Furthermore, it is preferable that the aspect ratio of the spherical activated carbon of this embodiment is 0.7 or more.

Furthermore, it is preferable that the spherical activated carbon of this embodiment carries an alkali or an acid.

According to the spherical activated carbon of the present embodiment, the pressure loss and the amount of dust can be suppressed. Thereby, such spherical activated carbon can be used for various purposes. Moreover, compared with the conventional activated carbon, the spherical activated carbon of this embodiment is also favorable in crack resistance.

The manufacturing method of the spherical activated carbon of this embodiment will not be specifically limited if it is a method which can obtain the spherical activated carbon which has the above-mentioned characteristics. Hereinafter, one Embodiment of the manufacturing method (henceforth "this manufacturing method") of the spherical activated carbon which concerns on this embodiment is demonstrated. [Manufacturing method of spherical activated carbon]

(raw material)

In the present production method, heavy hydrocarbon oil is used as a raw material of spherical activated carbon. Examples of the heavy hydrocarbon oil include one or two or more selected from the group consisting of petroleum tar, coal tar, ethylene tar, and the like.

Among them, if it is ethylene tar, it can be obtained by carrying out vacuum distillation of the light component of the bottom oil (bottom oil) produced|generated at the time of ethylene manufacture.

In addition, a resin derived from a fossil fuel or a plant containing a furan resin or a phenol resin can be used as a raw material of the spherical activated carbon.

Specifically, the present production method includes (1) production of cross-linked heavy pitch, (2) addition of additives to cross-linked heavy pitch, (3) molding of cross-linked heavy pitch, and (4) additives The six steps of extraction, (5) non-melting and (6) firing/activation. Hereinafter, each step will be described in order.

(1) Manufacture of cross-linked heavy asphalt

In the present production method, first, the cross-linked heavyweight pitch is produced. As will be described later, the production process of this cross-linked heavy-weight asphalt is to ensure appropriate incompatibility with the viscosity-adjusting additive containing an aromatic compound, and further, in the extraction process of the additive, the porous necessary process.

For the crosslinked heavy asphalt, for example, a liquid heavy hydrocarbon oil may be subjected to a crosslinking treatment and a heat treatment at normal temperature. Thereby, a solid crosslinked heavy pitch can be obtained at normal temperature. A specific production method of the crosslinked heavy pitch is described in, for example, Japanese Patent No. 4349627 .

(2) Add additives to the cross-linked heavy asphalt

Next, by adding additives to the obtained cross-linked heavy pitch, the viscosity of the cross-linked heavy pitch is adjusted so that the cross-linked heavy pitch has a viscosity suitable for spheroidization.

Examples of the additives include viscosity-adjusting additives such as naphthalene, which will be described later.

After the additives are added to the cross-linked heavy pitch and mixed with heat, spherical pitch can be obtained by molding the cross-linked heavy pitch.

In the present production method, the additive to be added to the heavy hydrocarbon oil-derived cross-linked heavy asphalt is preferably a bicyclic or tricyclic aromatic having a boiling point of 200°C or higher, preferably 205°C or higher, and more preferably 210°C or higher. compounds or mixtures thereof.

Specific examples of such preferable additives include, for example, one or two or more selected from the group consisting of naphthalene, methylnaphthalene, phenylnaphthalene, benzylnaphthalene, methylanthracene, phenanthrene, and biphenyl. Among them, the additive is preferably naphthalene.

When the total amount of the mixture of the crosslinked heavy duty pitch and the additive is 100% by mass, the lower limit of the amount of the additive added to the crosslinked heavy duty pitch is preferably 26% by mass or more, and more preferably 27 mass % or more, more preferably 28 mass %. When the additive amount of the additive is equal to or less than the lower limit value, sufficient pores may not be formed with respect to the obtained porous spherical pitch. In addition, the upper limit of the additive amount of the additive is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less. When the additive amount of the additive is equal to or greater than the upper limit value, the amount of the cross-linked heavy-weight asphalt in the mixture of the cross-linked heavy-weight asphalt and the additive becomes relatively small, so that the production efficiency may decrease. In addition, since more extraction holes than necessary are formed in the process described later, the strength of the spherical activated carbon obtained may be insufficient. By setting the amount of the additive in this range, the additive can be efficiently extracted from the spherical pitch in the process described later, and sufficient pores can be formed in the obtained porous spherical pitch. It should be noted that if the pores of the porous pitch are sufficient, in the infusibility step described later, the crosslinking reaction by the oxidation reaction can proceed to the inside of the porous spherical pitch, and the spherical shape of the porous spherical pitch can be maintained. Simultaneous carbonization. In addition, when the addition amount of naphthalene is made into 25 mass %, for example, the pores of the porous pitch may become insufficient and melt.

In addition, the pore formed by the said additive is included in a part of the pore volume of spherical activated carbon in the range of pore diameter of 50 nm or more and 10000 nm or less.

(3) Forming of cross-linked heavy asphalt

Next, the additive-added cross-linked heavyweight pitch is shaped. At this time, it is preferable to homogenize the mixture of the crosslinked heavyweight asphalt and the additive in advance. The mixture of the crosslinked weighted bitumen and the additive is preferably heated to make a molten mixture.

The molding of the crosslinked heavyweight pitch may be performed in the state of the molten mixture, or may be performed by cooling the molten mixture, then pulverizing it, stirring it in hot water, or the like. In addition, in order to carry out the extraction process of the subsequent additive more easily, it is preferable to shape|mold the crosslinked heavy pitch so that it may become spherical pitch with a particle diameter of 6.0 mm or less.

For example, by using water containing a suspending agent as a dispersion medium, under normal pressure or pressure, a homogeneous mixture of cross-linked heavy asphalt and additives can be melt-dispersed to obtain spherical asphalt.

In addition to this, as a method for obtaining spherical pitch, for example, the method disclosed in Japanese Patent Publication No. Sho 59-10930 can also be referred to. Specifically, it is possible to extrude the mixture of the cross-linked heavy-weight asphalt and the additive for viscosity adjustment in a molten state to obtain a rod-shaped asphalt, or to cool and solidify the asphalt obtained by stretching the asphalt. After the rod-shaped asphalt is fracturing and the length/diameter ratio is 5 or less, the rod-shaped asphalt is stirred and mixed in hot water containing a suspending agent at a temperature above the softening point of the rod-shaped asphalt to form a spherical shape.

In the present embodiment, the size of the above-described rod-shaped pitch determines the average particle diameter of the spherical activated carbon. Therefore, in order to make the average particle diameter of the spherical activated carbon 1.5 mm or more and 4.0 mm or less, the size of the rod-shaped pitch in the longitudinal direction is preferably about 1.5 mm to 10 mm. In addition, the diameter of the die when extruding the pitch rod is preferably about 1.5 mm to 10 mm.

By adding the rod-shaped pitch obtained as described above to hot water heated to a temperature equal to or higher than the softening point of the mixture of the cross-linked heavy-weight pitch and the additive, the rod-shaped pitch is softened and deformed to obtain a spherical pitch.

In addition, the temperature of the hot water (hereinafter, this temperature is referred to as "spheroidization temperature") when the molten mixture of the crosslinked heavyweight asphalt and the additive is cooled, pulverized, and stirred in hot water is determined according to the crosslinking weight. The viscosity of the molten mixture of the textured pitch and the additive may be appropriately set.

In the present embodiment, the lower limit of the spheroidization temperature is preferably 95°C or higher, more preferably 97°C or higher, and further preferably 98°C or higher. In addition, the upper limit of the spheroidization temperature is preferably 120°C or lower, more preferably 115°C or lower, and further preferably 110°C or lower. By setting the spheroidizing temperature within this range, spherical pitch can be obtained efficiently. In addition, if the spheroidizing temperature is low, since the mixture of a crosslinked heavyweight pitch and an additive will not deform|transform, there exists a possibility that a rod-shaped pitch cannot be spheroidized efficiently. On the other hand, if the spheroidization temperature is too high, the molten mixture of the crosslinked heavy pitch and the additive becomes a bag shape or the molten mixture is torn, so that the particle size of the finally obtained spherical activated carbon may be reduced.

In addition, when spheroidizing the pitch rod in hot water, it is preferable to perform stirring or the like. At this time, if the stirring force is weak, the spherical pitch may settle, and the spherical pitch may be welded together. On the other hand, if the stirring force is too high, there is a fear that tearing of the spherical pitch may occur due to the shearing force. From such a viewpoint, it is preferable to appropriately select the most suitable stirring mechanism and stirring rotation speed such that the spherical pitch floats/flows in hot water. In addition, it is not limited to stirring as a form of making a spherical pitch flow, and other appropriate methods may be employ|adopted.

Furthermore, in this embodiment, it is more preferable that the mixture of the above-mentioned crosslinked heavy-weight asphalt and the above-mentioned additive is melt-suspended and dispersed in hot water in the presence of a suspending agent. That is, it is more preferable to add a suspending agent to hot water when spheroidizing the rod-shaped pitch. The hot water containing the suspending agent has the effect of improving the dispersibility of the spherical pitches and preventing the spherical pitches from being welded to each other. From such a viewpoint, in the present embodiment, it is preferable to obtain spherical pitch by melt-suspending and dispersing the mixture of the cross-linked heavy-weight pitch and the additive in hot water.

In the present embodiment, examples of suspending agents include polyvinyl alcohol (hereinafter also referred to as "PVA"), xanthan gum, partially saponified polyvinyl acetate, methyl cellulose, carboxymethyl cellulose, Polyacrylic acid and its salts, polyethylene glycol and its ether derivatives, ester derivatives starch, gelatin and other water-soluble polymer compounds.

In this case, the concentration of the suspending agent may be appropriately set. It should be noted that the higher the concentration of the suspending agent, the lower the settling velocity of the spherical pitch. Accordingly, the spherical pitch can be dispersed by a smaller stirring force, and tearing of the spherical pitch due to shear force can be suppressed. Wait.

In the present embodiment, when PVA is used as a suspending agent, the lower limit of the content of PVA with respect to the above-mentioned hot water is 0.1% by mass or more, preferably 0.15% by mass or more, and more preferably 0.23% by mass or more , more preferably 0.3 mass % or more. In addition, the upper limit of the content is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less.

The lower limit of the temperature of the hot water is preferably 95°C or higher, more preferably 97°C or higher, and further preferably 98°C or higher. In addition, the upper limit of the temperature of the hot water is preferably 120°C or lower, more preferably 115°C or lower, and further preferably 110°C or lower.

Furthermore, in this embodiment, a thickener may be used together with a suspending agent, or a thickener may be used alone.

At the time of spheroidization, it is preferable that the liquid ratio is high with respect to the amount ratio of the rod-shaped pitch and the hot water containing the suspending agent. As a result, the influence of particle size reduction and irregularity due to the collision of rod-shaped pitches or the like is reduced.

(4) Extraction of additives

Next, the additives contained in the obtained spherical pitch are removed, and in the subsequent infusibility step, pores for allowing the oxidizing gas to diffuse into the spherical pitch are formed.

In the present embodiment, since the cross-linked heavy pitch has incompatibility with additives, it is presumed that the inside of the spherical pitch forms a sea-island structure of the cross-linked heavy pitch and the additives. From such a viewpoint, in the present production method, it is preferable to use a solvent to remove the additive part contained in the spherical pitch, and to form pores serving as passages for oxygen to the spherical pitch in the subsequent infusibility step.

The mass ratio of the solvent to the slurry of the spherical pitch is preferably 7 or more, more preferably 9 or more, and even more preferably 13. If the mass ratio of the solvent to the slurry of the spherical pitch is less than 7, the additives inside the particles may not be sufficiently extracted, and pores that serve as passages for oxygen to the spherical pitch may not be formed in the subsequent infusibility step.

As a solvent for extracting and removing additives from spherical pitch, aliphatic compounds can be cited. Examples of the aliphatic compounds include aliphatic hydrocarbons such as butane, pentane, hexane, and heptane, mixtures mainly composed of aliphatic hydrocarbons such as naphtha and kerosene, methanol, ethanol, propanol, and butanol. such as aliphatic alcohols, etc., among which n-hexane is suitably used.

At this time, the mass ratio of the slurry of n-hexane and spherical pitch is preferably 7 or more, more preferably 9 or more, and still more preferably 13 or more. If the mass ratio of the slurry of n-hexane and spherical pitch is less than 7, the additive inside the particles may not be sufficiently extracted, and pores that serve as passages for oxygen to the spherical pitch may not be formed in the subsequent infusibility step.

In the present embodiment, it is preferable to sufficiently form a hole for diffusing oxygen during infusibility to the inside. Therefore, it is preferable to sufficiently perform the extraction of the additive from the spherical pitch.

When the solvent is used in this way, only the additive can be efficiently removed while maintaining the shape of the spherical pitch.

When the additive is removed from the spherical pitch in the present production method, through-holes generated by the extraction of the additive are formed in the spherical pitch, whereby a porous spherical pitch having uniform porosity can be obtained.

In the present embodiment, the softening point of the cross-linked heavyweight pitch greatly affects the softening point of the porous spherical pitch. It should be noted that when the softening point is too low, the porous spherical pitch may be softened or melted when heat treatment for infusibility described later is performed, which is not preferable.

In the present embodiment, the softening point of the porous spherical pitch is preferably as high as possible. In order to increase the softening point of the porous spherical pitch, it is preferable to increase the weight of the cross-linked pitch. If the softening point of the porous spherical pitch is too high, anisotropic components are generated in the cross-linked pitch, and there is a fear that spheroidization of the cross-linked heavy pitch, extraction of additives, and uniform activation treatment to be described later will become difficult. .

From such a viewpoint, in the present embodiment, the softening point of the porous spherical pitch is preferably 150°C or higher and 350°C or lower, more preferably 200°C or higher and 300°C, and even more preferably 220°C or higher and 280°C or lower.

Furthermore, the toluene insoluble matter of the porous spherical pitch has a good correlation with the carbonization yield of the pitch, and the higher the toluene insoluble matter is, the higher the carbonization yield tends to be. Therefore, the toluene insoluble matter is preferably 40% or more, and more preferably 50% or more. The toluene-insoluble matter can be measured by a known method, for example, by the method described in paragraph 0030 of Patent Document 1.

(5) does not melt

Next, a porous spherical infusible pitch that is infusible to heat is formed from the porous spherical pitch. In this production method, the oxidizing gas is uniformly diffused into the inside of the porous spherical pitch by utilizing the pores formed by extracting the additive from the spherical pitch, and the crosslinking treatment is performed. Thereby, a porous spherical infusible pitch can be formed. More specifically, for example, the gas may flow in the fluidized bed with respect to the porous spherical pitch, and it may be heated at 100°C or higher and 350°C or lower, preferably 120°C or higher and 320°C or lower, more preferably 130°C or higher and 300°C or lower.

As the oxidizing gas, an oxidizing gas such as O ₂ , O ₃ , SO ₃ , NO ₂ , and air, or a mixed gas obtained by diluting these oxidizing gases with an inert gas such as nitrogen, carbon dioxide, and water vapor can be used.

In addition, the degree of the crosslinking treatment can be determined, for example, based on the oxygen content obtained by the elemental analysis of the porous pitch after the oxidation treatment obtained by the elemental analysis. In this case, the oxygen content is preferably 5 mass % or more, preferably 8 mass % or more and 25 mass % or less, more preferably 10 mass % or more and 23 mass % or less, and further preferably 11 mass % or more. Oxidation treatment is carried out so as to be not more than mass %.

(6) Firing/Activation

Finally, the porous spherical infusible pitch is fired to obtain carbon, and pores are formed in the carbon. It should be noted that the pores of the spherical activated carbon formed in the non-melting step are pores for diffusing oxygen during the non-melting process. After the firing/activation process, pores affecting the final adsorption capacity are formed in the spherical activated carbon. For example, a spherical carbon compact can be obtained by subjecting the porous spherical infusible pitch to heat treatment in a non-oxidizing atmosphere at 600°C or higher, preferably 650°C or higher, and more preferably 700°C or higher.

Next, the spherical carbon compact is fired and activated by a conventional method. At this time, the spherical carbon molded body is subjected to activation treatment in an activating gas atmosphere mainly composed of a mild oxidizing gas such as carbon dioxide and water vapor. Thereby, the spherical activated carbon of this embodiment can be obtained.

In the present embodiment, the activating gas is acted on the spherical carbon molded body at preferably 600°C or higher, more preferably 650°C or higher, and further preferably 700°C or higher. Thereby, carbonization and activation of the spherical carbon compact can be simultaneously performed, which is preferable from the viewpoint of process economy.

In the present embodiment, other substances such as acid, alkali, or metal may be further added to the spherical activated carbon obtained as described above. A known method may be used for the loading of other substances on the spherical activated carbon. For example, when a metal is supported or supported on spherical activated carbon, the spherical activated carbon can be used as a catalyst or the like.

Example

Next, the present invention will be described in more detail while showing examples, but the present invention is not limited to these examples.

[The average particle size]

The average particle diameter of the activated carbon was evaluated according to JIS K 1474. Specifically, a particle size cumulative line graph is prepared in accordance with JIS K1474, and a horizontal line is drawn on the vertical axis from the intersection of the vertical line at the 50% point of the horizontal axis and the particle size cumulative line graph, and the mesh size (mm) of the sieve indicated by the intersection point is obtained. ), and the value of the mesh is taken as the average particle size.

[pore diameter and pore volume]

The pore diameter and the pore volume of the activated carbon were measured using a pore volume mercury porosimeter (“AUTOPORE 9200” manufactured by MICROMERITICS) based on the mercury intrusion method. Specifically, activated carbon was put into a sample container, and degassed under a pressure of 2.67 Pa or less for 30 minutes. Next, mercury was introduced into the sample container, and the pressure was gradually applied to push the mercury into the pores of the activated carbon. Then, the pore volume distribution of the activated carbon was calculated using the following equations based on the relationship between the pressure at this time and the indentation amount of mercury.

The pore diameter is calculated as follows: when mercury is pressed into a cylindrical pore having a diameter (D) with a pressure (P), the surface tension of mercury is set to "γ", and the contact angle between mercury and the pore wall is calculated as When "θ" is set, the following relational expression holds according to the balance between the surface tension and the pressure acting on the pore cross section:

-πDγcosθ=π(D/2) ² ·P (Equation 2).

Therefore, D=(-4γcosθ)/P...(Formula 3).

In this specification, the surface tension of mercury is 484 dyne/cn, the contact angle between mercury and carbon is 130 degrees, the pressure P is expressed in MPa, and the pore diameter D is expressed in μm, and the pressure P and the pore diameter are obtained by the following equations D's relationship.

D=1.24/P...(Formula 4)

In addition, the pore volume in the range of 50-10000 nm of pore diameters in this Example corresponds to the volume of mercury injected|injected in the range of the corresponding mercury injection pressure.

[Evaluation of Dust Amount]

The dust amount of activated carbon was evaluated according to the following procedure.

1) After drying a membrane filter (47 mm in diameter, 1 μm mesh made by ADVANTEC) at 110° C. for 1 hour in advance, it was left to cool in a desiccator, and then weighed to 0.1 mg with a precision scientific balance.

2) Take 5g of dry sample into a 100ml Erlenmeyer flask, and weigh it to 0.1mg with a precision scientific balance.

3) 100 ml of pure water was added to the Erlenmeyer flask, and an ultrasonic cleaner (Bransonic desktop ultrasonic cleaner 1510J-MT manufactured by Emerson Japan, Ltd.) was used for 3 minutes.

4) The sonicated suspension was filtered through a sieve with a mesh size of 106 μm, and the filtrate was filtered through a membrane filter provided in a Millipore filter suction device. The wall surface of the Erlenmeyer flask in the step 3) above was rinsed with pure water, which was also filtered with a membrane filter.

5) After returning the sample remaining on the sieve in the step 4) above to the Erlenmeyer flask and adding 100 ml of pure water, the operations 3) and 4) above were repeated three times in total.

6) After drying the filtered membrane filter at 110° C. for 1 hour, it was left to cool in a desiccator for 30 minutes, and then weighed to 0.1 mg with a precision scientific balance.

7) The amount of carbon dust is calculated by the following formula.

Amount of soot = (B-A)/S...(Formula 5)

A: Mass of membrane filter before filtration (g)

B: Mass of membrane filter after filtration (g)

S: the mass of the sample (g)

[Vibration wear rate in water]

The water vibration abrasion rate of activated carbon was evaluated by the following method.

1) The membrane filter (mesh 0.3 μm) previously dried at 110° C. for 1 hour was allowed to cool in a desiccator, and then weighed to 0.1 mg with a precision scientific balance.

2) Weigh about 10 g of the dry sample to the level of 0.1 mg, transfer it into a 200 ml separatory funnel, add 50 ml of pure water, and use a vibrating machine (KM-SHAKER model V-S manufactured by IWAKI INDUSTRY CO., LTD. V-S amplitude 40 mm, vibration frequency 250 reciprocation/min) for 120 minutes of vibration.

3) The suspension was filtered through a sieve with a mesh of 150 μm, and the filtrate was suction filtered using a membrane filter. The wall surface of the separating funnel in the step 2) above was rinsed with pure water, and was also filtered with a membrane filter.

4) After drying the membrane filter at 110° C. for 30 minutes, it was left to cool in a desiccator for 30 minutes, and the mass of the membrane filter was accurately measured to 0.1 mg.

5) Calculate the vibration wear rate in water according to the following formula.

Vibration wear rate in water (%)=(b-a)/s×100...(Formula 6)

a: Mass of membrane filter before filtration (g)

b: The mass of the membrane filter after filtration (g)

s: the mass of the sample (g)

[specific surface area]

The gas adsorption amount of the sample (carbonaceous material) was measured using a specific surface area continuous flow type specific surface area measuring device (“FLOWSORB III” manufactured by MICROMERITICS) based on the gas adsorption method, and the specific surface area was calculated according to the BET equation.

Specifically, a sample was filled in a sample tube, and the following operation was performed while passing helium gas containing 30 vol% of nitrogen gas through the sample tube, and the amount of nitrogen adsorbed to the sample was obtained. That is, the sample tube was cooled to -196°C, and nitrogen was adsorbed to the sample. Next, the sample tube was returned to room temperature. At this time, the amount of nitrogen desorbed from the porous spherical carbonaceous material sample was measured with a thermal conductivity detector, and this was taken as the amount of adsorbed gas (v). Then, using the approximate formula derived from the BET equation:

Vm=1/(v·(1-x))...(Formula 7),

Using the one-point method realized by nitrogen adsorption (relative pressure x=0.3), the Vm at the liquid nitrogen temperature was obtained, and the specific surface area of the sample was calculated by the following formula:

Specific surface area=4.35×Vm(m2/g)...(Formula 8).

It should be noted that, in each of the above calculation formulas, v is the actually measured adsorption amount (cm ³ /g), and x is the relative pressure.

[fill density]

The packing density was measured according to the JIS K1474-1991 method.

[Aspect ratio]

The aspect ratio of the sample was calculated using a digital microscope ("VHX-700F" manufactured by KEYENCE Corporation).

Specifically, in order to achieve an average extraction, 30 sample particles were dispersed in a petri dish, and the lengths of the long axis and the short axis of one particle were measured with a digital microscope. Then, the aspect ratio is calculated from the length ratio of the major axis and the minor axis so that the maximum is 1. In the following Examples and the like, the average value of the aspect ratios of 30 particles was defined as the aspect ratio.

[Crush Strength]

The crushing strength can be obtained by the following method. That is, 32 sample particles of spherical activated carbon were randomly extracted, and the hardness at the moment when the sample particles were crushed was measured using a simple granular hardness tester (manufactured by Tsutsui Riken Co., Ltd.). The maximum value and the minimum value were excluded from the measured value of hardness, and the average value of the measured values of hardness of 30 sample particles was calculated and used as the crushing strength of the sample particle.

[Example 1]

A stainless steel with an inner volume of 25 liters was charged with 10.0 kg of residual oil (ethylene tar) generated during ethylene production with a specific gravity (ratio of the mass of the sample at 15°C to the mass of the equal volume of pure water at 4°C) 1.08 in a pressure-resistant container. Air was blown in at 3.7 L/min from the lower part of the reaction vessel, and an airblowing reaction was performed at 230°C to 250°C under a pressure of 0.4 MPa for 4 hours and 20 minutes. In this way, 9.5 kg of air blowing tar was obtained. After 3.0 kg of the obtained blowing tar was thermally gravimetric at 385°C, the light components were further distilled off under reduced pressure to obtain 1.4 kg of blowing pitch. The softening point of the obtained pitch was 203 degreeC, and the toluene insoluble matter was 58%.

0.72 kg of the above-mentioned air-blown pitch and 0.28 kg of naphthalene were charged into a pressure-resistant container with an inner volume of 1.5 L with a stirring blade, melt-mixed at 200° C., cooled to 140° C. to 160° C. and extruded to obtain A rod-shaped molded body with a diameter of 2 mm was obtained. Next, the rod-shaped molded body is fractured to a length of about 2.0 mm to 2.8 mm. About 450 ml of the above-mentioned fracturing product was put into 1 L of an aqueous solution in which 1.2% by weight of polyvinyl alcohol (degree of saponification=88%) was dissolved as a suspending agent and heated to 100°C. The fracturing material was spheroidized by stirring and dispersing, and then cooled, and the above-mentioned polyvinyl alcohol aqueous solution was replaced with water to obtain spherical pitch molding slurry. After removing most of the water by filtration, naphthalene in the spherical asphalt slurry was extracted and removed with 7 times the weight of n-hexane of the spherical asphalt slurry to obtain a porous spherical asphalt. Using a fluidized bed, the porous spherical pitch thus obtained was heated from room temperature to 150°C over 1 hour while blowing hot air, and then heated from 150°C to 260°C at a heating rate of 20°C/h, and then heated to 260°C at a rate of 20°C/h. Oxidation was performed by holding for 1 hour. In this way, a porous spherical infusible pitch that is infusible to heat is obtained. Next, the porous spherical infusible pitch was activated in a nitrogen atmosphere containing 50 vol% of water vapor at 850° C. using a fluidized bed until the packing density was 0.79 g/ml to obtain spherical activated carbon. The obtained spherical activated carbon was evaluated for its average particle diameter, pore size distribution, dust amount, vibration abrasion rate in water, specific surface area, aspect ratio, and crushing strength.

[Examples 2 to 8]

As shown in Tables 1 and 2, the amount of pitch at the time of melt-mixing blown pitch and naphthalene, the amount of naphthalene, the amount of rod-shaped molded body charged at the time of spheroidization, the spheroidization temperature, the concentration of polyvinyl alcohol, and the time of extraction of naphthalene were changed, respectively. Except for the amount of n-hexane and the packing density after activation, the activated carbons of Examples 2 to 8 were obtained by the same operation as in Example 1.

[Example 9]

As shown in Table 1, the pitch amount, naphthalene amount, rod-shaped molded body size, charge amount of rod-shaped molded body at the time of spheroidization, spheroidization temperature, polyvinyl alcohol concentration, extraction of A porous spherical pitch was obtained by the same operation as in Example 1 except for the amount of n-hexane in the case of naphthalene.

In the stationary layer, the obtained porous spherical pitch was heated from room temperature to 150°C over 1 hour while blowing hot air, and then heated from 150°C to 260°C at a heating rate of 20°C/h, and then heated to 260°C at a rate of 20°C/h. Oxidation was performed by holding for 1 hour. In this way, a porous spherical infusible pitch that is infusible to heat is obtained. Next, in the stationary layer, the porous spherical infusible pitch was activated at 850°C in a nitrogen atmosphere containing 50 vol% of water vapor until the packing density became 0.70 g/ml to obtain activated carbon.

[Example 10]

As shown in Table 1, the pitch amount, naphthalene amount, rod-shaped molded body size, charge amount of rod-shaped molded body at the time of spheroidization, spheroidization temperature, polyvinyl alcohol concentration, extraction of A porous spherical pitch was obtained by the same operation as in Example 1 except for the amount of n-hexane in the case of naphthalene.

In the stationary layer, the obtained porous spherical pitch was heated from room temperature to 150°C over 1 hour while blowing hot air, and then heated from 150°C to 300°C at a temperature increase rate of 20°C/h, and then heated to 300°C at a rate of 20°C/h. Oxidation was performed by holding for 1 hour. In this way, a porous spherical infusible pitch that is infusible to heat is obtained. Next, in the stationary layer, the porous spherical infusible pitch was activated at 850°C in a nitrogen atmosphere containing 50 vol% of water vapor until the packing density was 0.68 g/ml, thereby obtaining activated carbon.

[Example 11]

Using xanthan gum as a suspending agent, as shown in Table 1, the pitch amount, naphthalene amount, rod-shaped molded body size, charge amount of the rod-shaped molded body at the time of spheroidization, spherical shape when melt-mixing the air-blown pitch and naphthalene was adjusted. A porous spherical pitch was obtained by the same operation as in Example 1 except that the temperature, the concentration of xanthan gum, and the amount of n-hexane at the time of extracting naphthalene were changed.

In the stationary layer, the obtained porous spherical pitch was heated from room temperature to 150°C over 1 hour while blowing hot air, and then heated from 150°C to 300°C at a temperature increase rate of 20°C/h, and then heated to 300°C at a rate of 20°C/h. Oxidation was performed by holding for 1 hour. In this way, a porous spherical infusible pitch that is infusible to heat is obtained. Next, in the stationary layer, the porous spherical infusible pitch was activated at 850°C in a nitrogen atmosphere containing 50 vol% of water vapor until the packing density became 0.70 g/ml to obtain activated carbon.

[Comparative Example 1]

Activated carbon was prepared by the same operation as in Example 1, except that the pitch was 0.75 kg and the amount of naphthalene was 0.25 kg, and the porous spherical infusible pitch molded body was melted in the firing/activating step. Unable to maintain its shape (spherical).

[Comparative Example 2]

As shown in Table 1, except that the amounts of blowing pitch and naphthalene, the spheroidizing temperature, the concentration of polyvinyl alcohol, and the amount of hexane were adjusted, activated carbon was prepared in the same manner as in Example 1. During the process, the porous spherical infusible pitch molded body is melted, and its shape (spherical shape) cannot be maintained.

[Comparative Example 3]

As shown in Table 1, activated carbon was produced by the same operation as in Example 1, except that the amounts of blowing pitch and naphthalene, the spheroidizing temperature, and the concentration of polyvinyl alcohol were adjusted. As a result, the shapes of the pitch molded bodies obtained in the molding step of the crosslinked heavy pitch were all elliptical.

[Comparative Example 4]

A rod-shaped molded body having a diameter of 1.0 mm was fractured to a length of about 1.0 mm to 1.5 mm, and the amounts of blowing pitch and naphthalene, spheroidizing temperature, polyvinyl alcohol concentration, and hexane amount were adjusted as shown in Table 1, except Except for this, activated carbon was obtained by the same operation as in Example 1.

[Comparative Example 5]

About the spherical egret X7000H (Osaka Gas Chemical Co., Ltd.), the same evaluation as in Example 1 was performed.

[Comparative Example 6]

For KURARAY COAL SW (Kuraray Chemical Co., Ltd.), the same evaluation as in Example 1 was performed.

The results of each of the above-mentioned Examples and Comparative Examples are summarized in Tables 1 and 2.

In Table 1, "size" means the size of the rod-shaped molded body, and "charge amount" means the charged amount of the rod-shaped molded body. In addition, the "suspending agent" is, for example, PVA. In addition, "Rhex" means the mass ratio of hexane at the time of extraction, more specifically, means the mass ratio of n-hexane and spherical pitch slurry (amount of n-hexane/amount of spherical pitch slurry).

In Table 2, "D1" means melting, and "D2" means both are elliptical. In addition, "Vp1" means the pore volume in the range of 10-10000 nm, and "Vp2" means the pore volume in the range of 50-10000 nm. In addition, "Asw" means vibration attrition rate in water, "Rasp" means aspect ratio, and "Sp" means crush strength.

[Table 1]

[Table 2]

industrial availability

The present invention can be suitably used as activated carbon for, for example, separation processes, purification, catalysts, or solvent recovery and the like.

Claims (11)

1. A spherical activated carbon, characterized in that the spherical activated carbon is an integrally formed spherical activated carbon with an average particle diameter of 1.5 mm or more and 4.0 mm or less, The pore volume in the range of 50 nm or more and 10000 nm or less is the range of 0.01 ml/g or more and 0.24 ml/g or less. 2. spherical activated carbon according to claim 1, is characterized in that, The crushing strength is 1.20 kg/piece or more. 3. spherical activated carbon according to claim 1, is characterized in that, The amount of dust contained in 1 g of the spherical activated carbon is 2000 μg or less. 4. spherical activated carbon according to claim 1, is characterized in that, Vibration wear rate in water is less than 5%. 5. spherical activated carbon according to claim 1, is characterized in that, The aspect ratio is 0.7 or more, and the aspect ratio is the ratio of the short diameter to the long diameter. 6. spherical activated carbon according to claim 1, is characterized in that, Added base or acid. 7. a manufacture method of spherical activated carbon, is characterized in that, manufactures the spherical activated carbon of claim 1, and described manufacture method comprises: A step of adding a bicyclic or tricyclic aromatic compound having a boiling point of 200° C. or more as an additive to the crosslinked heavy asphalt slurry derived from heavy hydrocarbon oil; A step of obtaining a porous spherical pitch by dispersing a mixture of the crosslinked heavy pitch and the additive in hot water by melt-suspending and dispersing it in hot water, and extracting the additive with a solvent from the spherical pitch thus obtained; and the steps of infusibility and firing/activation of the porous spherical pitch slurry, The heavy hydrocarbon oil is one or more selected from the group consisting of petroleum tar, coal tar and ethylene tar, The temperature of the hot water is above 95°C and below 120°C, The solvent is an aliphatic compound, The mass ratio of the solvent to the spherical pitch is 7 or more. 8. the manufacture method of spherical activated carbon according to claim 7, is characterized in that, The addition amount of the additive is 26 mass % or more and 50 mass % or less when the total amount of the mixture of the cross-linked heavy duty pitch and the additive is 100 mass %. 9. The manufacture method of spherical activated carbon according to claim 7, is characterized in that, The additive is naphthalene. 10. The manufacture method of spherical activated carbon according to claim 7, is characterized in that, The mixture of the crosslinked weighted asphalt and the additive is melt-suspended and dispersed in hot water in the presence of a suspending agent. 11. The manufacture method of spherical activated carbon according to claim 10, is characterized in that, The suspending agent is one or both of polyvinyl alcohol and xanthan gum.