JP6803398B2 - Spherical activated carbon and its manufacturing method - Google Patents

Description

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

In the chemical industry, activated carbon is widely used for separation processes, refining, catalysts, or solvent recovery, as well as wastewater treatment, pollution control, or medical applications related to global pollution problems.

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

Further, activated carbon made from heavy hydrocarbon oil such as petroleum tar or ethylene bottom oil (Patent Document 1) and activated carbon made from resin (Patent Document 2) are known.

Japanese Patent Publication "Japanese Unexamined Patent Publication No. 2005-119947" Japanese Patent Publication "Japanese Unexamined Patent Publication No. 2000-23916"

Yuzo Sanada, 2 others "New Edition Activated Carbon Basics and Applications", Kodansha Co., Ltd., March 1, 1992

By the way, when activated carbon is used, it is required to reduce the pressure loss and suppress the dust.

When activated carbon is filled in a device such as a column and a fluid containing a certain concentration of the target substance is circulated and used, it is necessary to densely fill the activated carbon particles in order to maximize the effect per volume on the target substance. is there.

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 interparticle voids of the activated carbon are closed. Further, in these cases, it is considered that the pressure loss becomes large due to the clogging of the device filter or the like, and as a result, the load on the device becomes large. Further, when handling a large flow rate fluid using activated carbon, there is a risk that activated carbon having a small particle size or generated dust may scatter.

Further, when the activated carbon and the target substance are separated from each other after the fluid (gas or liquid) containing the activated carbon and the target substance are brought into contact with each other, a 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 powdered activated carbon described above basically has a small particle size, it is considered that the pressure loss becomes large when the activated carbon is filled in the apparatus and used, and the amount of fluid processed is limited.

Further, when the powdered activated carbon is used in this way, there is a risk that the powder will scatter when treating a fluid having a large flow rate.

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

However, conventionally, in the method for producing granular activated carbon, a method of mixing powdered charcoal with a binder and granulating into granules is generally used. That is, the granular activated carbon obtained by the conventional production method is not integrally molded. Therefore, since the conventional granular activated carbon has a weak strength, it is considered that if such granular activated carbon is filled in the apparatus and used, a large amount of dust is generated and it is difficult to separate it from the fluid.

Further, since the conventional granular activated carbon generally uses coconut shell charcoal or the like, there are many impurities, and it is considered that elution of impurities other than dust becomes a problem.

For these reasons, the development of activated carbon capable of suppressing pressure loss and dust is required.

As a result of diligent studies to solve the above problems, the present inventors have found that pressure loss and dust can be suppressed by integrally molded spherical activated carbon having a particle diameter of about several mm. Has been completed.

That is, the present invention is an integrally molded 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 in the range of a pore diameter of 50 nm or more and 10,000 nm or less. It provides a spherical activated carbon in the range of / g or more and 0.24 ml / g or less.

Furthermore, the present invention provides a method for producing spherical activated carbon having the above-mentioned characteristics.

According to the present invention, it is possible to provide activated carbon capable of suppressing pressure loss and dust.

Hereinafter, an embodiment of the spherical activated carbon according to the present invention will be specifically described.

[Spherical activated carbon]
The spherical activated carbon according to 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 a pore diameter of 50 nm or more and 10,000 nm or less. Is 0.01 ml / g or more and 0.24 ml / g or less. A detailed description of the pore diameter and the pore volume will be described later.

In the present specification, the spherical activated carbon means a spherical activated carbon. The degree of spherical shape 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 further preferably 0.9 or more. The aspect ratio is the ratio of the minor axis to the major axis. The major axis and the minor axis are determined 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. When the aspect ratio of the spherical activated carbon is 0.7 or more, when the spherical activated carbon is used, the wear due to the collision between the particles of the spherical activated carbon is further reduced, so that the generation of dust can be sufficiently suppressed. it can.

The spherical activated carbon according to the present embodiment is an integrally molded spherical activated carbon. The "integrally molded spherical activated carbon" means an activated carbon that is molded as primary particles and has a spherical shape. The spherical activated carbon according to the present embodiment has a pore diameter and a pore volume described later, and thus can be said to be a primary particle activated carbon having porosity and spheres. The spherical activated carbon according to the present embodiment is superior in mechanical strength to conventional spherical activated carbon such as a sintered body of aggregated particles. For example, the spherical activated carbon according to the present embodiment has a high crushing strength or a low underwater shaking wear rate as compared with the conventional spherical activated carbon.

(Average particle size)
The lower limit of the average particle size of the spherical activated carbon according to the present embodiment is 1.5 mm or more, preferably 1.7 mm or more, more preferably 1.8 mm, from the viewpoint of suppressing an increase in the pressure loss of the packed bed of the spherical activated carbon. , More preferably 2.0 mm or more. Further, the upper limit value is 4.0 mm or less, preferably 3.5 mm or less, more preferably 3.0 mm or less, from the viewpoint of realizing sufficient contact between the spherical activated carbon and the fluid in the packed bed. When the average particle size is in this range, the interparticle voids of the spherical activated carbon can be sufficiently increased. Therefore, with such a spherical activated carbon, the pressure loss can be sufficiently reduced when the device such as a column or a separation tower is filled with the spherical activated carbon and brought into contact with the fluid containing the target substance.

In the present embodiment, the average particle size of the spherical activated carbon can be evaluated according to JIS K 1474. That is, a cumulative particle size diagram of the spherical activated carbon is created from the results obtained from the operation of JIS K 1474. From the intersection of the vertical line of 50% of the points on the horizontal axis and the cumulative particle size diagram, a horizontal line is drawn on the vertical axis to obtain the mesh opening (mm) of the sieve indicated by the intersection. The value of this opening is taken as the average particle size of the spherical activated carbon.

(Pore diameter)
In the present specification, the pore diameter means the pore diameter of the pores contained in the spherical activated carbon. In this embodiment, the pore diameter and the pore volume can be measured by, for example, a known mercury intrusion method. Further, the pore diameter and the pore volume can be adjusted according to, for example, the properties of the crosslinked heaviness pitch described later, the type of the additive in the crosslinked heaviness pitch, the conditions for extracting the additive with a solvent, and the like. It is possible.

(Pore volume)
As used herein, the pore volume means the volume of pores in a specific pore size range of activated carbon.

The lower limit of the pore volume in the range of the pore diameter of 50 nm or more and 10,000 nm or less in the spherical activated carbon according to the present embodiment is 0.01 ml / g from the viewpoint of suppressing a decrease in productivity in the method for producing spherical activated carbon described later. As mentioned above, it is preferably 0.02 ml / g or more, more preferably 0.03 ml / g or more, and further preferably 0.05 g / ml or more. Further, the upper limit value is 0.24 ml / g or less, preferably 0.22 ml / g or less, more preferably 0.20 ml / g or less, still more preferably 0, from the viewpoint of preventing the crushing strength of the spherical activated carbon from decreasing. It is 18 ml / g or less.

Further, the lower limit of the pore volume in the range of the pore diameter of 10 nm or more and 10,000 nm or less in the spherical activated carbon according to the present embodiment is 0.01 ml / g or more from the viewpoint of suppressing the decrease in the productivity of the spherical activated carbon. It is preferably 0.02 ml / g or more, more preferably 0.03 ml / g or more, and further preferably 0.04 ml / g or more. The upper limit thereof is 0.28 ml / g or less, preferably 0.27 ml / g or less, and more preferably 0.26 ml / g or less from the viewpoint of preventing the crushing strength of the spherical activated carbon from decreasing. , More preferably 0.25 ml / g, and most preferably 0.24 ml / g or less.

According to the present embodiment, when the spherical activated carbon satisfies the above range, it is possible to sufficiently form the pores required for infusibilization, which will be described later, so that insolubilization can be performed efficiently, and the spherical activated carbon can be produced. Can be made. Further, since it is possible to suppress an increase in the pore volume, which is less likely to be involved in the adsorption ability of the spherical activated carbon, the density of the spherical activated carbon is increased, and the performance per volume of the spherical activated carbon is improved.

In this embodiment, the pore volume can be evaluated, for example, by a known mercury intrusion method.

(Crushing power)
Since the spherical activated carbon according to the present embodiment is primary particles, it has higher mechanical strength than the conventional spherical activated carbon obtained by sintering agglomerated 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 may have a sufficient size, for example, depending on the use of the spherical activated carbon, and may be, for example, 10.0 kg / piece or less.

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

(Amount of dust)
As used herein, the term "dust" means fine powder contained in spherical activated carbon. The amount of dust means the amount of this dust, and specifically, it is an amount calculated by measuring the amount of dust described later.

In the present embodiment, the amount of dust contained in 1 g of spherical activated carbon is preferably 2000 μg or less from the viewpoint of suppressing an increase in pressure loss in the packed bed of spherical activated carbon and from the viewpoint of sufficiently exhibiting the separability of spherical activated carbon. It is more preferably 1500 μg or less, further 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 according to the present embodiment can be measured by a specific method described later. The amount of dust can be reduced by, for example, a manufacturing method by integral molding.

(Underwater shaking wear rate)
When the spherical activated carbon is put into water and shaken in water, the spherical activated carbons collide with each other and the spherical activated carbons are scraped and peeled off. In the present embodiment, the underwater shaking wear rate is calculated from the amount of spherical activated carbon that has peeled off at this time. Specifically, the underwater shaking wear rate can be calculated from the following formula.

Underwater shaking wear rate (%) = (AB) / A × 100 (%) ・ ・ ・ (Equation 1)
A: Mass of spherical activated carbon before shaking in water (g)
B: Mass of spherical activated carbon after shaking in water (g)
The water shake wear rate of the spherical activated carbon according to the present embodiment is preferably 5% or less, more preferably 4.5% or less. The lower the underwater shaking wear rate, the higher the strength of the spherical activated carbon, and the smaller the amount of dust generated when the spherical activated carbons collide with each other.

(Specific surface area)
The specific surface area is obtained by adsorbing gas molecules on a substance to be evaluated and calculating the ratio between the amount of adsorbed gas molecules and the adsorption cross-sectional area of the gas molecules. Specifically, the specific surface area is determined by calculating the amount of nitrogen adsorbed by the BET method and setting the adsorption cross-sectional area of nitrogen molecules to 0.162 nm ² . The specific surface area is sometimes called a specific surface area (SSA).

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

The specific surface area of the spherical activated carbon according to the present embodiment, from the viewpoint of exerting the adsorption function of the spherical activated carbon, is preferably 100 m ² / g or more, more preferably 300 meters ² / g or more, more preferably 400 meters ² / It is g or more. When the specific surface area is 100 m ² / g or more, it is considered that the adsorption function of the spherical activated carbon is sufficiently exhibited. The larger the specific surface area is, the more preferable it is from the above viewpoint, but it is sufficient as long as the desired adsorption function of the spherical activated carbon can be sufficiently obtained, and it may be, for example, 4000 m ² / g or less.

The spherical activated carbon according to the present embodiment may be impregnated with other substances. Other substances include known substances that can be attached to activated carbon, such as acids, alkalis, and metals. Specific examples of the acid include non-volatile acids such as phosphoric acid and sulfuric acid, and organic acids such as citric acid and malic acid. Specific examples of the alkali include potassium carbonate, sodium carbonate, potassium hydroxide, sodium hydroxide and the like. Specific examples of the metal include transition elements such as platinum, silver, iron, and cobalt, and compounds thereof.

As described above, the spherical activated carbon according to the present embodiment preferably contains 2000 μg or less of dust per 1 g of the spherical activated carbon.

Further, the spherical activated carbon according to the present embodiment preferably has an underwater shaking wear rate of 5% or less.

Further, the spherical activated carbon according to the present embodiment preferably has an aspect ratio of 0.7 or more.

Further, the spherical activated carbon according to the present embodiment is preferably impregnated with an alkali or an acid.

According to the spherical activated carbon according to the present embodiment, the pressure loss and the amount of dust are suppressed. Therefore, such spherical activated carbon can be used for many purposes. Further, the spherical activated carbon according to the present embodiment has better crack resistance as compared with the conventional activated carbon.

The method for producing spherical activated carbon according to the present embodiment is not particularly limited as long as spherical activated carbon having the above-mentioned characteristics can be obtained. Hereinafter, an embodiment of a method for producing spherical activated carbon according to the present embodiment (hereinafter, also simply referred to as “the present production method”) will be described.

[Manufacturing method of spherical activated carbon]
(material)
In this production method, heavy hydrocarbon oil is used as a raw material for spherical activated carbon. Examples of the heavy hydrocarbon oil include one or more selected from the group consisting of petroleum tar, coal tar, ethylene bottom oil and the like.

Of these, ethylene bottom oil can be obtained by vacuum distillation of the light component of the bottom oil produced during ethylene production.

Further, a fossil fuel-derived or plant-derived resin containing a furan resin or a phenol resin may be used as a raw material for the spherical activated carbon.

In detail, this production method includes (1) production of a crosslinked heaviness pitch, (2) addition of an additive to the crosslinked heaviness pitch, (3) molding of a crosslinked heaviness pitch, and (4) addition. It includes 6 steps of agent extraction, (5) infusibilization and (6) firing / activation. Hereinafter, each step will be described in order.

(1) Manufacture of cross-linked heaviness pitch In this manufacturing method, the cross-linking heaviness pitch is first manufactured. As will be described later, the step of manufacturing the crosslinked heaviness pitch ensures an appropriate incompatibility with the viscosity adjusting additive made of an aromatic compound, and further, in the step of extracting the additive, the spherical pitch is porous. This is a process required for conversion.

The cross-linking heaviness pitch may be, for example, a cross-linking treatment and a heat treatment of a heavy-duty hydrocarbon oil liquid at room temperature. This makes it possible to obtain a solid crosslinked heaviness pitch at room temperature. A specific method for producing a crosslinked heaviness pitch is described in, for example, Japanese Patent No. 4349627.

(2) Addition of additive to the cross-linking heaviness pitch Next, by adding an additive to the obtained cross-linking heaviness pitch, the viscosity of the cross-linking heaviness pitch is adjusted, and the cross-linking heaviness pitch is adjusted. Make the viscosity suitable for spheroidization.

Examples of the additive include an additive for adjusting viscosity such as naphthalene, which will be described later.

A spherical pitch can be obtained by adding an additive to the crosslinked heaviness pitch, heating and mixing, and then forming the crosslinked heaviness pitch.

In the present production method, the additive added to the crosslinked heaviness pitch derived from the heavy hydrocarbon oil has a boiling point of 200 ° C. or higher, preferably 205 ° C. or higher, more preferably 210 ° C. or higher, and has an aromatic of 2 or 3 rings. It is preferably a compound or a mixture thereof.

Specific examples of such preferable additives include one or more selected from the group consisting of naphthalene, methylnaphthalene, phenylnaphthalene, benzylnaphthalene, methylanthracene, phenanthrene, biphenyl and the like. .. Of these, the additive is preferably naphthalene.

The lower limit of the amount of the additive added to the crosslinked heaviness pitch is preferably 26% by mass or more, more preferably 27, when the total amount of the mixture of the crosslinked heaviness pitch and the additive is 100% by mass. It is by mass or more, more preferably 28% by mass. When the amount of the additive added is not more than the lower limit, it may not be possible to form sufficient pores for the obtained porous spherical pitch. The upper limit is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less. When the addition amount of the additive is equal to or more than the upper limit value, the cross-linking heaviness pitch and the cross-linking heaviness pitch amount in the mixture of the additive are relatively small, so that the production efficiency may decrease. Further, since more extraction holes than necessary are formed in the step described later, the strength of the obtained spherical activated carbon may be insufficient. By setting the amount of the additive in this range, it is possible to efficiently extract the additive from the spherical pitch and form sufficient pores for the obtained porous spherical pitch in the step described later. If the pores of the porous pitch are sufficient, in the infusibilization step described later, the cross-linking reaction by the oxidation reaction proceeds to the inside of the porous spherical pitch formation, and carbonization is performed while maintaining the spherical shape of the porous spherical pitch. be able to. For example, when the amount of naphthalene added is 25% by mass, the pores having a porous pitch become insufficient and may melt.

The pores formed by the additive are included in a part of the pore volume of the spherical activated carbon in the range where the pore diameter is 50 nm or more and 10,000 nm or less.

(3) Forming of cross-linked heaviness pitch Next, the cross-linking heaviness pitch to which an additive is added is formed. At that time, it is preferable to make the mixture of the crosslinked heaviness pitch and the additive uniform in advance. The mixture of the crosslinked heaviness pitch and the additive is preferably a melt mixture by heating.

The cross-linked heaviness pitch may be formed in the state of a molten mixture, or the molten mixture may be cooled and then pulverized and stirred in hot water. In order to facilitate the subsequent extraction step of the additive, it is preferable to form the crosslinked heaviness pitch so as to have a spherical pitch with a particle diameter of 6.0 mm or less.

The spherical pitch can be obtained, for example, by using water containing a suspending agent as a dispersion medium and melt-dispersing a homogeneous mixture of the crosslinked heaviness pitch and the additive under normal pressure or pressure.

In addition, as a method for obtaining a spherical pitch, for example, the method disclosed in Japanese Patent Publication No. 59-10930 may be referred to. Specifically, a mixture of the crosslinked heaviness pitch and the viscosity adjusting additive is extruded in a molten state into a rod shape, or a stretched product thereof is cooled and solidified, and the obtained rod-shaped pitch is crushed. After forming a rod-shaped pitch having a length / diameter ratio of 5 or less, the mixture may be formed into a spherical shape by stirring and mixing in hot water containing a suspending agent at a temperature equal to or higher than the softening point of the rod-shaped pitch.

In this embodiment, the size of the rod-shaped pitch described above determines the average particle size of the spherical activated carbon. Therefore, in order to make the average particle size 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 to 10 mm. Further, the diameter of the mouthpiece when extruding the rod-shaped pitch is preferably about 1.5 mm to 10 mm.

By putting the rod-shaped pitch obtained as described above into hot water heated above the softening point of the mixture of the crosslinked heaviness pitch and the additive, the rod-shaped pitch is softened and deformed to become a spherical pitch.

Further, the temperature of hot water (hereinafter, this temperature is referred to as "spheroidization temperature") when the molten mixture of the crosslinked heaviness pitch and the additive is cooled and then crushed and stirred in hot water is the crosslinked heavy duty. It may be appropriately set according to the viscosity of the molten mixture of the formation pitch and the additive.

In the present embodiment, the lower limit of the spheroidizing temperature is preferably 95 ° C. or higher, more preferably 97 ° C. or higher, still more preferably 98 ° C. or higher. The upper limit thereof is preferably 120 ° C. or lower, more preferably 115 ° C. or lower, and even more preferably 110 ° C. or lower. By setting the spheroidization temperature in this range, the spheroidal pitch can be efficiently obtained. If the spheroidization temperature is low, the mixture of the crosslinked heaviness pitch and the additive is not deformed, so that the rod-shaped pitch may not be efficiently spheroidized. On the other hand, if the spheroidization temperature is too high, the molten mixture of the crosslinked heaviness pitch and the additive becomes bale-shaped, or the molten mixture is torn off, so that the particle size of the finally obtained spherical activated carbon becomes large. It may become smaller.

When spheroidizing the rod-shaped pitch in hot water, it is preferable to stir. At that time, if the stirring force is weak, the spherical pitches may settle and the spherical pitches may be fused to each other. On the other hand, if the stirring force is too high, the spherical pitch may be torn off due to the shearing force. For this reason, it is preferable to appropriately select the optimum stirring mechanism and stirring rotation speed so that the spherical pitch floats and flows in hot water. The means for flowing the spherical pitch is not limited to stirring, and other appropriate methods may be used.

Further, in the present embodiment, it is more preferable that the mixture of the crosslinked heaviness pitch and the additive is melt-suspended and dispersed in hot water in the presence of a suspending agent. That is, when spheroidizing the rod-shaped pitch, it is more preferable to add a suspending agent in hot water. The hot water containing the suspending agent has a role of improving the dispersibility of the spherical pitches and preventing the spherical pitches from fusing to each other. For this reason, in the present embodiment, it is preferable to obtain a spherical pitch by melting, suspending and dispersing the mixture of the crosslinked heaviness pitch and the additive in hot water.

In the present embodiment, examples of the suspending agent 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. Examples thereof include derivatives, ester derivatives, starches, water-soluble polymer compounds such as gelatin, and the like.

At that time, the concentration of the suspending agent may be appropriately set. The higher the concentration of the suspending agent, the lower the settling speed of the spherical pitch. According to this, the spherical pitch can be dispersed with a smaller stirring force and the tearing of the spherical pitch due to the shearing force is suppressed. can do.

In the present embodiment, when PVA is used as the suspending agent, the lower limit of the content of PVA with respect to the hot water described above is 0.1% by mass or more, preferably 0.15% by mass or more, more preferably 0. It is 23% by mass or more, more preferably 0.3% by mass or more. The upper limit is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less.

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

Further, in the present embodiment, the thickener may be used in combination with the suspending agent, or the thickener alone may be used alone.

When spheroidizing, the liquid ratio is preferably high with respect to the amount ratio of the rod-shaped pitch to the hot water containing the suspending agent. As a result, the influence of small particle diameter and deformation due to collision between rod-shaped pitches is reduced.

(4) Extraction of Additives Next, the additives contained in the obtained spherical pitch are removed, and holes are formed for the oxidizing gas to diffuse into the inside of the spherical pitch in the subsequent infusibilization step.

In the present embodiment, since the crosslinked heaviness pitch has incompatibility with the additive, it is presumed that the inside of the spherical pitch has a sea-island structure of the crosslinked heaviness pitch and the additive. Therefore, in this production method, by removing the additive portion contained in the spherical pitch with a solvent, a hole serving as a passage for oxygen gas with respect to the spherical pitch is formed in the subsequent infusibilization step. It is preferable to do so.

The mass ratio of the solvent to the slurry having a spherical pitch is preferably 7 or more, more preferably 9 or more, and further preferably 13. If the mass ratio of the solvent to the slurry with a spherical pitch is less than 7, the additive inside the particles may not be sufficiently extracted, and in the subsequent infusibilization step, holes that serve as passages for oxygen gas with respect to the spherical pitch are formed. It may not be possible to form.

Examples of the solvent for extracting and removing the additive from the spherical pitch include an aliphatic compound. Examples of this aliphatic compound include aliphatic hydrocarbons such as butane, pentane, hexane and heptane, mixtures mainly containing aliphatic hydrocarbons such as naphtha and kerosine, and aliphatic alcohols such as methanol, ethanol, propanol and butanol. Of these, n-hexane is preferably used.

At that time, the mass ratio of n-hexane and the slurry having a spherical pitch is preferably 7 or more, more preferably 9 or more, and further preferably 13 or more. If the mass ratio of n-hexane to the slurry with a spherical pitch is less than 7, the additive inside the particles may not be sufficiently extracted, and it becomes a passage for oxygen gas with respect to the spherical pitch in the subsequent infusibilization step. It may not be possible to form a hole.

In the present embodiment, it is preferable to sufficiently form holes for diffusing oxygen at the time of insolubilization to the inside. For that purpose, it is preferable to sufficiently extract the additive from the spherical pitch.

By using the solvent in this way, it is possible to efficiently remove only the additive while maintaining the shape of the spherical pitch.

When the additive is removed from the spherical pitch in the present production method, a loophole is formed in the spherical pitch due to the extraction of the additive, whereby a porous spherical pitch having uniform porosity can be obtained.

In the present embodiment, the softening point of the porous spherical pitch is greatly affected by the softening point of the crosslinked heaviness pitch. If the softening point is too low, the porous spherical pitch may soften or melt during the heat treatment for insolubilization described later, which is not preferable.

In the present embodiment, the higher the softening point of the porous spherical pitch, the more preferable. In order to increase the softening point of the porous spherical pitch, it is preferable to promote the heaviness of the cross-linking pitch. If this softening point is too high, anisotropic components may be generated during the cross-linking pitch, making it difficult to spheroidize the cross-linking heaviness pitch, extract additives, and perform a uniform activation treatment described later.

Therefore, in the present embodiment, the softening points of the porous spherical pitch are preferably 150 ° C. or higher and 350 ° C. or lower, more preferably 200 ° C. or higher and 300 ° C. or higher, and further preferably 220 ° C. or higher. It is 280 ° C. or lower.

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

(5) Infusibilization Subsequently, a porous spherical infusible pitch that is insoluble in heat is formed from the porous spherical pitch. In the present production method, for this purpose, 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 cross-linking treatment is performed. This makes it possible to form a porous spherical infusible pitch. More specifically, for example, a gas is flowed in a fluidized bed with respect to a porous spherical pitch, and 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. It may be heated below.

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

Further, the degree of the cross-linking treatment can be determined, for example, by the oxygen content of the porous pitch after the oxidation treatment obtained by the elemental analysis. At that time, the oxygen content may be 5% by mass or more, preferably 8% by mass or more, 25% by mass or less, more preferably 10% by mass or more, 23% by mass or less, still more preferably 11% by mass or more, 21. It is preferable to carry out the oxidation treatment so as to have a mass% or less.

(6) Firing / Activation Finally, the porous spherical infusibilization pitch is calcined to carbon, and pores are formed in this carbon. The pores of the spherical activated carbon formed in the infusibilization step are for diffusing oxygen at the time of infusibilization. After the firing and activation steps, the pores that control the final adsorption capacity are formed in the spherical activated carbon. For example, a spherical carbon molded product can be obtained by heat-treating the porous spherical infusible pitch in a non-oxidizing atmospheric gas at 600 ° C. or higher, preferably 650 ° C. or higher, more preferably 700 ° C. or higher.

Next, the spherical carbon molded product is fired and activated by a conventional method. At that time, the spherical carbon molded product is activated in an activated gas atmosphere containing mild oxidizing gas such as carbon dioxide and water vapor as main components. As a result, the spherical activated carbon according to the present embodiment can be obtained.

In the present embodiment, the activating gas is allowed to act on the spherical carbon molded product at preferably 600 ° C. or higher, more preferably 650 ° C. or higher, and even more preferably 700 ° C. or higher. As a result, carbonization and activation of the spherical carbon molded product can be promoted at the same time, which is preferable from the viewpoint of process economy.

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

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Average particle size]
The average particle size of activated carbon was evaluated according to JIS K 1474. Specifically, a particle size cumulative diagram is created according to JIS K 1474, and a horizontal line is drawn on the vertical axis from the intersection of the vertical line of 50% of the points on the horizontal axis and the particle size cumulative diagram to indicate the intersection. The opening (mm) was obtained, and the value of this opening was taken as the average particle size.

[Pore diameter and pore volume]
Regarding the pore diameter and pore volume of the activated carbon, the pore diameter and pore volume of the activated carbon were measured using a pore volume mercury porosimeter (“AUTOPORE 9200” manufactured by MICROMERITICS) by a mercury intrusion method. Specifically, activated carbon was placed in a sample container and degassed at a pressure of 2.67 Pa or less for 30 minutes. Then, mercury was introduced into the sample container and gradually pressurized to press mercury into the pores of the activated carbon. Then, from the relationship between the pressure at this time and the amount of mercury injected, the pore volume distribution of the activated carbon was calculated using the following calculation formulas.

To calculate the pore diameter, when mercury is press-fitted into a cylindrical pore with a diameter (D) by pressure (P), the surface tension of mercury is "γ" and the contact angle between mercury and the pore wall is "θ". Then, from the balance between the surface tension and the pressure acting on the pore cross section,
−ΠDγcosθ = π (D / 2) ²・ P ・ ・ ・ (Equation 2)
The relational expression of is established. Therefore,
D = (-4γcosθ) / P ... (Equation 3)
Will be.

In the present specification, the surface tension of mercury is 484 dyne / cm, the contact angle between mercury and carbon is 130 degrees, the pressure P is MPa, and the pore diameter D is μm, and the following formula D = 1.24 /. P ... (Equation 4)
The relationship between the pressure P and the pore diameter D was determined by

The pore volume in the pore diameter range of 50 to 10,000 nm in this example corresponds to the volume of mercury injected into the corresponding mercury injection pressure range.

[Evaluation of dust amount]
The amount of dust in the activated carbon was evaluated by the following procedure.
1) A membrane filter (ADVANTEC diameter 47 mm, opening 1 μm) was dried at 110 ° C. for 1 hour, allowed to cool in a desiccator, and then weighed to 0.1 mg with a precision scientific balance.
2) 5 g of the dried sample was placed in a 100 ml Erlenmeyer flask and weighed to 0.1 mg with a precision science balance.
3) 100 ml of pure water was added to the Erlenmeyer flask, and the mixture was placed in an ultrasonic cleaner (Bransonic desktop ultrasonic cleaner 1510J-MT manufactured by Emerson Japan, Ltd.) for 3 minutes.
4) The suspension after ultrasonic waves was filtered through a sieve having an opening of 106 μm, and the filtrate was filtered through a membrane filter set in a millipore filter suction device. The wall surface of the Erlenmeyer flask in the above step 3) was flushed with pure water, and this was also filtered with a membrane filter.
5) The sample remaining on the sieve in the step 4) was returned to the Erlenmeyer flask, 100 ml of pure water was added, and then the operations 3) and 4) were repeated a total of 3 times.
6) The filtered membrane filter was dried at 110 ° C. for 1 hour, allowed 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 was calculated by the following formula.

Amount of carbon dust = (BA) / S ... (expression 5)
A: Mass of membrane filter before filtration (g)
B: Mass (g) of the membrane filter after filtration
S: Sample mass (g)
[Underwater shaking wear rate]
The underwater shaking wear rate of activated carbon was evaluated by the following method.
1) A membrane filter (opening 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 dried sample to the order of 0.1 mg, transfer it to a 200 ml separatory funnel, add 50 ml of pure water, and then shake it with a shaker (KM-SHAKER model VS made by Iwaki Sangyo, amplitude 40 mm, shaker. It was shaken for 120 minutes at 250 round trips / minute.
3) The suspension was filtered through a sieve having an opening 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 flushed with pure water, and this was also filtered with a membrane filter.
4) The membrane filter was dried at 110 ° C. for 30 minutes and then allowed to cool in a desiccator for 30 minutes, and the mass of the membrane filter was correctly measured to 0.1 mg.
5) The underwater shaking wear rate was calculated by the following formula.

Underwater shaking wear rate (%) = (ba) / s × 100 ... (Equation 6)
a: Mass of membrane filter before filtration (g)
b: Mass (g) of the membrane filter after filtration
s: Sample mass (g)
[Specific surface area]
Specific surface area The amount of gas adsorbed on the sample (carbonaceous material) was measured using a specific surface area measuring device ("FLOWSORB III" manufactured by MICROMERITICS) by the continuous flow type gas adsorption method, and the specific surface area was calculated by the BET formula. ..

Specifically, the sample was filled in a sample tube, and the following operation was performed while flowing helium gas containing 30 vol% of nitrogen through the sample tube to determine the amount of nitrogen adsorbed on the sample. That is, the sample tube was cooled to -196 ° C., and nitrogen was adsorbed on the sample. Next, the sample tube was returned to room temperature. At this time, the amount of nitrogen desorbed from the porous spherical carbonaceous substance sample was measured with a thermal conductivity type detector and used as the adsorbed gas amount (v). Then, the approximate expression derived from the BET equation:
V _m = 1 / (v · (1-x)) ・ ・ ・ (Equation 7)
Vm was obtained by the one-point method (relative pressure x = 0.3) by nitrogen adsorption at the liquid nitrogen temperature using the following equation:
Specific surface area = 4.35 x V _m (m ² / g) ... (Equation 8)
The specific surface area of the sample was calculated by In each of the above calculation formulas, v is the measured adsorption amount (cm ³ / g), and x is the relative pressure.

[Filling 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).

Specifically, 30 sample particles were spread on a petri dish so as to have an average extraction, and the lengths of the major axis and the minor axis of one particle were measured with a digital microscope. Then, the aspect ratio was calculated from the length ratio of the major axis and the minor axis so as to have a maximum of 1. In the following examples and the like, the average value of the aspect ratios of 30 particles was taken as the aspect ratio.

[Crushing power]
The crushing strength was determined 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 material hardness tester (manufactured by Tsutsui Rikagaku Kikai Co., Ltd.). The maximum and minimum values were removed from the measured hardness values, and the average value of the measured hardness values of 30 sample particles was calculated to determine the crushing strength of the sample particles.

[Example 1]
Bottom oil (ethylene bottom oil) produced during the production of ethylene with a specific gravity (ratio of the mass of the sample at 15 ° C. and the mass of equal volume of pure water at 4 ° C.) of 1.08 in a stainless steel pressure-resistant container with an internal volume of 25 liters. 10.0 kg was charged. Air was blown from the bottom of the reaction vessel at 3.7 L / min, and the air blowing reaction was carried out at 230 to 250 ° C. for 4 hours and 20 minutes under a pressure of 0.4 MPa. Thus, 9.5 kg of air blowing tar was obtained. After 3.0 kg of the obtained air blowing tar was heat-heavy at 385 ° C., the light component was further distilled off under reduced pressure to obtain an air blowing pitch of 1.4 kg. The obtained pitch had a softening point of 203 ° C. and a toluene insoluble content of 58%.

The above air blowing pitch of 0.72 kg and naphthalene of 0.28 kg are placed in a pressure-resistant container with an internal volume of 1.5 L equipped with a stirring blade, melt-mixed at 200 ° C., cooled to 140 to 160 ° C., and extruded. , A rod-shaped molded product having a diameter of 2 mm was obtained. Next, the rod-shaped molded product was crushed so as to have a length of about 2.0 mm to 2.8 mm. About 450 ml of the above-mentioned crushed product was put into 1 L of an aqueous solution in which 1.2% by weight of polyvinyl alcohol (sakenization degree = 88%) as a suspending agent was dissolved and heated to 100 ° C. The crushed product was spheroidized by stirring and dispersing, cooled, and the polyvinyl alcohol aqueous solution was replaced with water to obtain a spherical pitch molded product slurry. After removing most of the water by filtration, naphthalene in the spherical pitch slurry was extracted and removed with n-hexane having a weight 7 times that of the spherical pitch slurry to obtain a porous spherical pitch. The porous spherical pitch thus obtained is heated from room temperature to 150 ° C. in 1 hour using a fluidized bed while passing through heated air, and then 260 ° C. at a heating rate of 150 ° C. to 20 ° C./h. After raising the temperature to 260 ° C., the mixture was kept at 260 ° C. for 1 hour for oxidation. In this way, a porous spherical infusibilization pitch that is insoluble in heat was obtained. Subsequently, the porous spherical infusible pitch was activated using a fluidized bed in a nitrogen gas atmosphere containing 50 vol% water vapor at 850 ° C. until a filling density of 0.79 g / ml was obtained to obtain spherical activated carbon. The average particle size, pore size distribution, dust amount, shaking wear rate in water, specific surface area, aspect ratio and crushing strength of the obtained spherical activated carbon were evaluated.

[Examples 2 to 7 and Reference Example 8 ]
As shown in Tables 1 and 2, the pitch amount when the air blowing pitch and naphthalene are melt-mixed, the amount of naphthalene charged, the amount of rod-shaped molded product charged during spheroidization, the spheroidization temperature, the polyvinyl alcohol concentration, and the amount of naphthalene extracted. Activated carbons of Examples 2 to 7 and Reference Example 8 were obtained by the same operation as in Example 1 except that the amount of n-hexane and the packing density after activation were changed.

[Example 9]
As shown in Table 1, the pitch amount when melting and mixing the air blowing pitch and naphthalene, the amount of naphthalene, the size of the rod-shaped molded body, the amount of the rod-shaped molded body charged at the time of spheroidization, the spheroidization temperature, the polyvinyl alcohol concentration, and naphthalene are A porous spherical pitch was obtained by the same operation as in Example 1 except that the amount of n-hexane at the time of extraction was adjusted.

The obtained porous spherical pitch was heated from room temperature to 150 ° C. in 1 hour in a static layer through heated air, and then heated to 260 ° C. at a heating rate of 150 ° C. to 20 ° C./h. After that, it was held at 260 ° C. for 1 hour for oxidation. In this way, a porous spherical infusibilization pitch that is insoluble in heat was obtained. Subsequently, the porous spherical infusible pitch was activated in a static layer at 850 ° C. in a nitrogen gas atmosphere containing 50 vol% water vapor until the packing density reached 0.70 g / ml to obtain activated carbon.

[Example 10]
As shown in Table 1, the pitch amount when melting and mixing the air blowing pitch and naphthalene, the amount of naphthalene, the size of the rod-shaped molded body, the amount of the rod-shaped molded body charged at the time of spheroidization, the spheroidization temperature, the polyvinyl alcohol concentration, and naphthalene are A porous spherical pitch was obtained by the same operation as in Example 1 except that the amount of n-hexane at the time of extraction was adjusted.

The obtained porous spherical pitch was heated in a static layer through heated air from room temperature to 150 ° C. in 1 hour, and then raised to 300 ° C. at a heating rate of 150 ° C. to 20 ° C./h. After that, it was held at 300 ° C. for 1 hour to oxidize. In this way, a porous spherical infusibilization pitch that is insoluble in heat was obtained. Subsequently, the porous spherical infusible pitch was activated in a static layer at 850 ° C. in a nitrogen gas atmosphere containing 50 vol% water vapor until the packing density reached 0.68 g / ml to obtain activated carbon.

[Example 11]
Xanthan gum is used as a suspending agent, and as shown in Table 1, the pitch amount, naphthalene amount, rod-shaped molded body size, rod-shaped molded body charge amount at the time of spheroidization, and spherical shape when the air blowing pitch and naphthalene are melt-mixed. A porous spherical pitch was obtained by the same operation as in Example 1 except that the conversion temperature, the xanthan gum concentration, and the amount of n-hexane when extracting naphthalene were adjusted.

The obtained porous spherical pitch was heated in a static layer through heated air from room temperature to 150 ° C. in 1 hour, and then raised to 300 ° C. at a heating rate of 150 ° C. to 20 ° C./h. After that, it was held at 300 ° C. for 1 hour to oxidize. In this way, a porous spherical infusibilization pitch that is insoluble in heat was obtained. Subsequently, the porous spherical infusible pitch was activated in a static layer at 850 ° C. in a nitrogen gas atmosphere containing 50 vol% water vapor until the packing density reached 0.70 g / ml to obtain activated carbon.

[Comparative Example 1]
When 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, the porous spherical infusible pitch compact was melted in the firing and activation steps, and its shape ( Spherical) could not be maintained.

[Comparative Example 2]
As shown in Table 1, when activated carbon was prepared by the same operation as in Example 1 except that the air blowing pitch, the amount of naphthalene, the spheroidization temperature, the polyvinyl alcohol concentration, and the amount of hexane were adjusted, the steps of firing and activation were performed. The porous spherical insoluble pitch compact was melted and its shape (spherical) could not be maintained.

[Comparative Example 3]
As shown in Table 1, activated carbon was prepared in the same manner as in Example 1 except that the air blowing pitch, the amount of naphthalene, the spheroidization temperature, and the polyvinyl alcohol concentration were adjusted. As a result, all the shapes of the pitch compacts obtained in the step of forming the crosslinked heavier pitch were oval.

[Comparative Example 4]
A rod-shaped molded product having a diameter of 1.0 mm is crushed to a length of about 1.0 mm to 1.5 mm, and as shown in Table 1, the air blowing pitch, the amount of naphthalene, the spheroidization temperature, and the polyvinyl alcohol concentration. Activated carbon was obtained by the same operation as in Example 1 except that the amount of hexane was adjusted.

[Comparative Example 5]
The same evaluation as in Example 1 was performed on the spherical egret X7000H (Osaka Gas Chemical Co., Ltd.).

[Comparative Example 6]
The same evaluation as in Example 1 was performed for Kuraray Call SW (Kuraray Chemical Co., Ltd.).

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

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

In Table 2, "D1" means melting, and "D2" means that everything is oval. Further, "Vp1" means a pore volume in the range of 10 to 10000 nm, and "Vp2" means a pore volume in the range of 50 to 10000 nm. Further, "Asw" means the underwater shaking wear rate, "Rasp" means the aspect ratio, and "Sp" means the crushing strength.

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

Claims (10)

The average particle size is 1. Spherical activated carbon with a size of 6 mm or more and 4.0 mm or less and integrally molded.
A spherical activated carbon having a pore volume of 50 nm or more and 10,000 nm or less and a pore volume of 0.01 ml / g or more and 0.24 ml / g or less. The spherical activated carbon according to claim 1, wherein the crushing strength is 1.20 kg / piece or more. The spherical activated carbon according to claim 1 or 2, wherein the amount of dust contained in 1 g of the spherical activated carbon is 2000 μg or less. The spherical activated carbon according to any one of claims 1 to 3, wherein the underwater shaking wear rate is 5% or less. The spherical activated carbon according to any one of claims 1 to 4, wherein the aspect ratio is 0.7 or more. The spherical activated carbon according to any one of claims 1 to 5, characterized in that it is impregnated with an alkali or an acid. The method for producing spherical activated carbon according to any one of claims 1 to 6.
A step of adding a 2 or 3 ring aromatic compound having a boiling point of 200 ° C. or higher as an additive to the crosslinked heaviness pitch derived from a heavy hydrocarbon oil.
A step of melt-suspending and dispersing a mixture of the crosslinked heaviness pitch and the additive in hot water, extracting the additive from the spherical pitch obtained thereby using a solvent, and obtaining a porous spherical pitch. ,
Including the steps of insolubilizing and firing / activating 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 bottom oil.
The temperature of the hot water is 95 ° C. or higher and 120 ° C. or lower.
The solvent is an aliphatic compound and is
The mass ratio of the solvent to the spherical pitch is 7 or more .
When the total amount of the mixture of the crosslinked heaviness pitch and the additive is 100% by mass, the addition amount of the additive is 26% by mass or more and 50% by mass or less of the spherical activated carbon. Production method. The method for producing spherical activated carbon according to claim 7, wherein the additive is naphthalene. The method for producing spherical activated carbon according to claim 7 or 8 , wherein the mixture of the crosslinked heaviness pitch and the additive is melt-suspended and dispersed in hot water in the presence of a suspending agent. The method for producing spherical activated carbon according to claim 9 , wherein the suspending agent is one or both of polyvinyl alcohol and xanthan gum.