JPH0292816A - Activated carbon and production thereof - Google Patents

Abstract

PURPOSE:To obtain activated carbon having larger crushing strength by specifying friction loss, bulk density and specific surface area. CONSTITUTION:The aimed activated carbon has <=2.0 % friction-resistant loss, >=0.55g/ml bulk density and >=800m<2>/g. For producing said activated carbon, 100 pts.wt. mixture composed of 60-99wt.% pitch and 1-40wt.% thermosetting resin powder of uncured or partially cured is mixed with 5-50 pts.wt. pitch viscosity lowering agent to obtain an uniform mixture. Said mixture is heat- molded to obtain granule and the granule is held for a long period of time at a temperature of, for instance, not more than boiling point of the pitch viscosity lowering agent with ventilating gas flow such as air and the pitch viscosity lowering agent is removed to obtain porous body. said porous body is oxidized by using oxidizer to obtain infusible material, then said infusible material is carbonized to obtain carbonized material, thus said carbonized material is activated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to activated carbon with excellent crushing strength and a method for producing the same.

Conventional technology: As a spherical activated carbon with high crushing strength,
Spherical charcoal described in Japanese Patent Laid-Open No. 69215 or Japanese Unexamined Patent Publication No. 104498/1988 is known. That is, these publications describe the production of spherical charcoal with high crushing strength by mixing amorphous carbon particles or chain hydrocarbon polymers into pitch.

Problems to be Solved by the Invention However, as shown in Comparative Example 1 below, the activated carbon obtained from the spherical bodies described in the former publication has an
It has a crushing strength of only g, and the case described in the latter publication also has a crushing strength of the same degree. Therefore, when activated carbon is used for wastewater treatment, for example, in a fixed bed or fluidized bed system, it is likely to be destroyed or powdered due to friction caused by the flow, resulting in clogging.

Furthermore, there was a problem of a decrease in yield during regeneration.

To prevent this, it was necessary to take measures such as limiting the flow rate and increasing the floor space.

The present invention has been made in view of the above-mentioned problems in the conventional technology, and its purpose is to provide activated carbon with higher crushing strength and to provide a method for producing the same.

Means for solving the problem Conventionally, activated carbon has already been tested using the standard measurement method J.
A hardness of just under 99% was obtained with TS -1474, and it was thought that there was no room for further improvement in hardness. Furthermore, even if there is room for improvement, it is thought that such improvement will reduce the activation ability, and equivalent consideration has not been given to activated carbon with improved crushing strength. However, as a result of studies by the present inventors, the friction loss resistance rate measured by a unique method described later was 2.
0″X or less, and the bulk density is 0.55 tr/m1
It has now been found that activated carbon having a specific surface area of 800 i/f or more exhibits significantly improved crushing strength, and that such activated carbon can be produced by a specific method.

That is, the activated carbon of the present invention has ffi! Friction loss rate is 2.0%
Below, bulk density is 0.55g/m1 or more, specific surface area is 80
It is characterized by being equal to or greater than 0 rrj'/g.

The activated carbon of the present invention can be produced by sequentially carrying out the steps (a) to (f) below.

(a) Obtain a homogeneous mixture consisting of 100 parts by weight of a mixture of 60 to 99% by weight of pitch, 1 to 40% by weight of uncured or partially cured thermosetting resin powder, and 5 to 50 parts by weight of a pitch viscosity reducer. (b) heating and molding the homogeneous mixture to obtain a granular material; (c) removing the pitch viscosity reducing agent from the granular material to obtain a porous material; (d) making the porous material invincible. a step of obtaining an infusible material by
) a step of carbonizing the invincible material to obtain a carbide; and (f) a step of activating the carbide.

The present invention will be described in detail below.

The activated carbon of the present invention needs to have a friction loss resistance of 2.0% or less, preferably in the range of 1.0X to 0.05''X.A friction loss resistance of 2.0% or less is preferable. When it gets high,
As the surface hardness decreases, the crushing strength of the particles decreases.

In the present invention, the friction loss resistance refers to a value measured by the following measuring method. The measurement method is JIS-1
474, the average particle size is less than 1M, and the case of one city or more is different, but when the average particle size is less than 1M, it is determined as follows. That is, the diameter is 60 meters and the height is 200 meters.
Put 10 g of the sample, 5 glass bulbs with a diameter of 10 mm, and 100 ml of distilled water into a ff1 glass container. Then,
It was shaken for 15 minutes at an amplitude of 501 ifl and 100 times/min, and after shaking, the supernatant was filtered using a membrane filter. Add 100 ml of distilled water again and repeat the same operation 5 times. Thereafter, the membrane filter is dried in a dryer at 105° C. for 12 hours, and the weight is measured to calculate the friction loss resistance. On the other hand, when the average particle size is 1+n+ or more, a glass container with a diameter of 1100n and a height of 200 boxes is used, and the weight is determined in the same manner as above except that the sample to be placed in it is 501r and the amount of distilled water is 500ml. is measured and calculated.

Further, the activated carbon of the present invention needs to have a bulk density of 0.55 g/ml or more, preferably 0.60 to 0.5 g/ml.
in the range of 80 g/ml. Bulk density is JIS K
-1474 d. Bulk density is 0.55z
This is because if it is lower than /ml, the crushing strength will decrease even if the surface hardness is high.

Furthermore, the activated carbon of the present invention has a specific surface area of 800 m2/g
or more, preferably 900 to 15
It is in the range of 00nf/. The specific surface area is a value determined by the B, E, T method based on nitrogen adsorption. Specific surface area is 800r
r? When it becomes smaller than /+r, the adsorption performance as activated carbon decreases.

The activated carbon having the above characteristics of the present invention is produced as follows.

Step (a) First, pitch, pitch viscosity reducing agent, and uncured or partially cured thermosetting resin powder are uniformly mixed to obtain a uniform mixture. When the viscosity of the pitch is low, these ingredients may be mixed at the same time, and a homogeneous mixture can be obtained by slightly heating the thermosetting resin while leaving it uncured or partially cured.

However, since normal pitch has a high viscosity, it is not possible to obtain a homogeneous mixture by simultaneous mixing of the above-mentioned ingredients at a temperature that keeps the thermosetting resin uncured or partially cured. If a pitch viscosity reducing agent and a pitch viscosity reducing agent are melt-mixed at a temperature higher than the pour point of either of them, the viscosity can be lowered, so if a thermosetting resin is added to the resulting molten mixture and mixed, The thermosetting resin powder can be uniformly dispersed at a temperature that remains uncured or partially cured. It is efficient that the temperature at which the pitch and the pitch viscosity reducing agent are melt-mixed in advance is preferably a temperature equal to or higher than the pour point of both.

The pitch used in the present invention is not particularly limited, but preferably has a pour point of 50 to 400°C, a hydrogen/carbon atomic ratio of 0.45 to 1.4, a quinoline solubility of 50% or less, and more. Preferably, a pitch having a pour point of 130 to 300°C, a hydrogen/carbon atomic ratio of 0.5 to 1.0, and a quinoline solubility of 35% or less is used.

Here, the pour point is the temperature of the pitch when the temperature does not rise in 6 to 7 minutes using a high-performance flow tester used in the field of polymers and applying 10 kg of weight to 1 g of pitch. This is the temperature at which the plunger drops temporarily due to an increase in bulk density due to softening, and then begins to drop again due to the outflow of pitch from the nozzle. Further, the hydrogen/carbon atomic ratio is a value calculated from the carbon-hydrogen analysis value obtained by burning a pinch and performing elemental analysis by gas chromatography. Furthermore, the quinoline dissolved content was measured by the following method. First, a 150ml SuS centrifuge tube (centrifuge tube for centrifuge)
Add 1 g of powdered pitch to 100 mesh passes and 100 ml of quinoline, a first-class reagent. This centrifuge tube is heated and dissolved in a water bath at 75-80°C for 30 minutes with occasional stirring.Then, after cooling to room temperature, centrifugation is performed for 20 minutes in a centrifuge to separate solid and liquid, and the supernatant liquid is decanted. After removing it, it is washed with 50 ml of benzene, and the remaining quinoline is replaced with benzene. The centrifugation operation for washing was performed twice, and the centrifuge tube was placed in a dryer at 105°C for 4 hours.
After drying for an hour, calculate the insoluble content.

The pitch used in the present invention is produced by heating and making the tar-like substances produced when obtaining crude oil, asphalt, heavy oil, light oil, kerosene, naphtha, etc., residual oil during petroleum refining, etc. as necessary, and further It can be easily obtained by removing low boiling point components through operations such as distillation and extraction. It can also be obtained by removing low boiling point components from the coal tar or thermal decomposition residue of organic polymers.

The amount of pitch blended is set in the range of 60 to 99% by weight based on the mixture of pitch and thermosetting resin powder. If the amount of pitch is outside the above range, the strength improvement effect will be insufficient.

On the other hand, the thermosetting resin is preferably used in the form of a powder, with the particle size as fine as possible.

Those having an average primary particle diameter of 50ρ or less are preferably used.

Note that this average primary particle diameter is a value determined by a Coulter counter. Furthermore, although the thermosetting resin may be partially cured, an uncured one is preferably used. The type of thermosetting resin used is not limited, but includes phenol resin, urea resin,
Examples include epoxy resin, melamine resin, furfuryl alcohol resin, and the like.

The thermosetting resin is usually almost insoluble in a molten mixture consisting of pitch and a pitch viscosity reducing agent, but even in that case, it is in the form of fine particles and can be uniformly dispersed because the viscosity of the molten mixture is low. The thermosetting resin is contained in a range of 1 to 40% by weight based on the mixture of pitch and thermosetting resin. If the amount of the thermosetting resin is less than 1% by weight, the strength improvement effect will be insufficient, and if it exceeds 40% by weight, the strength improvement effect will be insufficient. The preferred range is 2 to 35% by weight, more preferably 3 to 20% by weight.

The pitch viscosity reducing agent used in the present invention can reduce the viscosity of pitch, and any agent can be used as long as it can be easily extracted in the subsequent extraction step. A two- or three-ring aromatic compound having good compatibility with pitch and a boiling point of 200° C. or higher is preferably used. Examples include naphthalene, methylnaphthalene, phenylnaphthalene, benzylnaphthalene, methylanthracene, phenanthrene, and biphenyl. Among them, naphthalene is particularly preferred because it has a remarkable viscosity-reducing effect and excellent extractability in a solvent extraction step.

The amount of pitch viscosity reducing agent used is in the range of 5 to 50 parts by weight based on 100 parts by weight of the mixture of pitch and thermosetting resin. If the amount of the pitch viscosity reducing agent is less than 5 parts by weight, the viscosity of normal pitch becomes too high, making molding difficult. Furthermore, even when a pitch that does not have such difficulties is used, the resulting granules are non-porous, making it difficult to make them infusible. On the other hand, if it exceeds 50 parts by weight, the molded product obtained after extraction of the pitch viscosity reducing agent becomes porous with a diameter larger than that requiring infusibility, and becomes brittle and weak in strength. The amount of pitch viscosity reducing agent also varies depending on the mixing ratio of pitch and thermosetting resin. When the ratio of thermosetting resin is large, the viscosity of the mixture becomes large, so it is preferable to increase the amount of pitch viscosity reducing agent. When the ratio of thermosetting resin is small, the amount of pitch viscosity reducing agent is preferably increased. The amount can be reduced.

The homogeneous mixture obtained by uniformly mixing thermosetting resin powder into a molten mixture of pitch and pitch viscosity reducer contains other additives such as thermoplastic resin or amorphous carbon particles. Good too.

Step (b) Next, the homogeneous mixture is formed into granules at a temperature equal to or higher than its pour point, and then cooled to a temperature lower than its pour point to form granules.

For example, a method is used in which the homogeneous mixture is heated to a temperature equal to or higher than its pour point, and then the homogeneous mixture is poured into a dispersion medium and stirred, in accordance with the method disclosed in JP-A-48-31195. Also, according to the method shown in JP-A No. 56-69214, the homogeneous mixture is extruded into a string shape at a temperature higher than the pour point of the homogeneous mixture, and after cooling, it is crushed or cut into pellets or small rods. A method can be used in which the homogeneous mixture is poured into a dispersion medium at a temperature higher than the pour point and stirred. In particular, the latter method is preferably used.

In the former method, the temperature of the dispersion medium may be room temperature, but the temperature of the dispersion medium is preferably set to be higher than the pour point of the molten mixture consisting of the pitch and the pitch viscosity reducing agent. As the dispersion medium, water containing a suspending agent is suitable, but for example, glycerin, ethylene glycol, etc. that do not contain a suspending agent can be used.

Suspending agents when the dispersion medium is water include partially saponified polyvinyl acid, polyvinyl alcohol, methyl cellulose, carboxymethyl cellulose, polyacrylic acid or its salts, polyethylene glycol or its ether derivatives, ester derivatives, starch, gelatin, etc. A water-soluble polymer compound of is preferably used.

The particle size of the resulting granules is adjusted to a desired size by adjusting the viscosity of the homogeneous mixture, the viscosity of the dispersion medium, the stirring force, and the like. The shape of the granules is particularly preferably spherical. Cooling after molding may be rapid cooling or slow cooling, but slow cooling is more suitable. At that time, it is preferable that the stirring is gentle.

Step (c) Next, the pitch viscosity reducing agent is removed from the molded body to form a porous body. If the pitch viscosity reducing agent is not removed, it will melt when heated in the invulnerability process described below, making it impossible to maintain the granularity.Also, even if the pitch viscosity reducer is not heated in the invulnerability process, the heating in the carbonization process will reduce the pitch viscosity. The reducing agent volatilizes, and as a result, the grain size is damaged or cavities are created inside, causing a decrease in strength. In order to remove the pitch viscosity reducer, for example, a method of holding the pitch viscosity reducer at a temperature below the boiling point for a long time while passing a stream of air, nitrogen, etc., or a method that has high solubility for the pitch viscosity reducer, For pitch and thermosetting resins, methods such as extraction using a solvent with low solubility are adopted. The latter method is particularly preferably used, and examples of the solvent include aliphatic hydrocarbons such as hexane, heptane, cyclohexane, naphtha, and gelosin, and saturated alicyclic hydrocarbons.

Step (d) The porous body thus obtained is then subjected to an infusible treatment. The main purpose of this treatment is to oxidize pitch, which is originally meltable, using an oxidizing agent to make it infusible against heat, and to maintain its shape in the next carbonization step. As the oxidizing agent, for example, an oxidizing gas such as 0□, 01, SOg, Not, or CI 2, or an oxidizing liquid such as an aqueous solution of sulfuric acid, phosphoric acid, nitric acid, or chromic acid is used. The infusibility treatment is carried out at a temperature below the pour point using the above oxidizing agents alone or in combination. As the infusibility progresses, the pour point of the pitch increases, so by successively increasing the treatment temperature accordingly, the infusibility time can be shortened.

Step (e) Next, the obtained invincible material is fired and carbonized at a temperature of 400° C. or higher, preferably 600° C. or higher in an inert atmosphere,
Granular charcoal, which is a carbide, is obtained.

Process (f) Next, this granular charcoal is activated by a known method.

For example, when the temperature reaches 800 to 1200°C using a steam method, the temperature increase may be stopped and activation may be performed while maintaining the temperature.

Example Hereinafter, the present invention will be explained by examples.

Examples 1 to 8 and Comparative Examples 1 to 7 Adjustment of raw material pitch: Raw material pitch A was prepared by heating naphtha to 800° C. in a tubular reactor and pyrolyzing the tar-like material for a contact time of about 10 seconds. Distilled, normal pressure equivalent 450℃
It was obtained by removing the following dissolved components.

This pitch has a pour point of 230°C and a hydrogen/carbon atomic ratio of 0.
．． 68, the quinoline solubility was 15% by weight.

Raw material pitch B is obtained by dry distilling coal at 1000°C in a coke oven, distilling the tar material under reduced pressure at 350°C under conditions of 5 cities + IQ, and distilling the low boiling point content below 450°C in terms of normal pressure. Then, in order to raise the pour point of the pitch obtained, nitrobenzene was added to make it 20% by weight of the sum of the pitch and the pitch, and after the weighting reaction was carried out at 350°C, This excludes low boiling point components. The obtained pitch has a pour point of 200°C and a hydrogen/carbon atomic ratio of 0.
．． 56, the quinoline dissolved content was 32% by weight.

Production of spherical coal: Pitch and naphthalene 300 of the type and amount shown in Table 1
were placed in a 21 pressure vessel and melted and mixed at 150''C for 0.5 hour with stirring. The resulting molten mixture is
The resin or amorphous carbon powder shown in the table was added and stirred for 1 hour.The resulting homogeneous mixture was cooled to 80-85℃ without taking it out of the pressure container, and the temperature inside the container was cooled to 80-85℃. 10 kg under a pressure of 10 kg G/d from a nozzle cap with 30 holes with a diameter of 1.5 stops.
It was extruded at a rate of 0 g/+u+.

The extruded rod-shaped body was cooled in water for 30 minutes and then pulverized using a chopper colloid mill. The shape was rod-like, and the length-to-diameter ratio of the rod was approximately 1.0. After removing water by mixing, 100% of this rod-shaped pitch composition was
．． 5% by weight polyvinyl alcohol aqueous solution 2j! and stirred at 200 rpm. When heated to 80° C., this rod-shaped pitch composition became a spherical dispersion. This was cooled to 50°C over about 30 minutes and then to 20°C over 20 minutes. The obtained piece-like pitch granules were dried after extracting the naphthalene in the granules with n-hexane using an extractor, and heated at 35°C/100°C while blowing air for 20.117 minutes.
Raise the temperature to 300℃ at a heating rate of 1 hour, and at 300″C
The mixture was kept for 0 minutes to complete infusibility. Next, 105 g of the obtained invincible granules were placed in a fluidized bed using nitrogen gas at 200°C/
The temperature was raised to 900°C at a heating rate of Activation was performed at 900° C. for 1 hour in a fluidized bed in an atmosphere containing an equal amount of nitrogen gas. The activation yield was 45%. Table 1 shows the physical properties of the obtained spherical charcoal. The physical properties in Table 1 other than those for which the measurement methods have already been explained are as follows.

Crushing strong crab JIS standard sieve mesh opening 590 and mesh opening 710
Of the crushing strength determined by selecting 30 samples from among the samples between the μm sieves and applying pressure to each using a hardness meter,
This is the average value of 28 values excluding the maximum value and minimum value.

Iodine adsorption amount: According to JIS 1474.

Caramel decolorization rate: According to JIS 1470 except that it was left in granular form without being powdered.

Comparative Example 8 In the method for producing activated carbon, pitch 2. The procedure was the same as in Comparative Example 6, except that the mixture of naphthalene and amorphous carbon powder was cooled from 80°C to 25°C in 5 minutes. The results are shown in Table 1.

(Continued) Effects of the Invention Since the present invention has the above configuration, the activated carbon obtained by the production method of the present invention has a much higher crushing strength than that obtained by the conventional technology. It will be what you get. Therefore, the activated carbon of the present invention can be used, for example, in water treatment,
Alternatively, when used for gas treatment, the layer height of activated carbon can be reduced, the flow rate can be increased, or the period of use can be extended.

Patent applicant: Kureha Chemical Industry Co., Ltd. Agent: Patent Attorney Tsuyoshi Watanabe

Claims (4)

[Claims] (1) Friction loss rate is 2.0% or less, bulk density is 0.55g
/ml or more and a specific surface area of 800 m^2/g or more. (2) A friction loss resistance of 2.0% or less and a bulk density of 0.55 g/ml, characterized by comprising the steps (a) to (f) below.
The above is a method for producing activated carbon having a specific surface area of 800 m^2/g or more. (a) Mixture 10 consisting of 60-99% by weight of pitch and 1-40% by weight of uncured or partially cured thermosetting resin powder
0 parts by weight and 5 to 50 parts by weight of a pitch viscosity reducing agent, (b) heating and molding the homogeneous mixture to obtain granules, (c) reducing pitch viscosity from the granules. a step of removing the reducing agent to obtain a porous body; (d) a step of infusibilizing the porous body to obtain an infusible material; (e) a step of carbonizing the infusible material to obtain a carbide; and (f) a step of carbonizing the infusible material to obtain a carbide. A step of activating the carbide. (3) To obtain a homogeneous mixture consisting of pitch, thermosetting resin, and pitch viscosity reducer, first melt and mix the pitch and pitch viscosity reducer at a temperature higher than the pour point of the pitch or pitch viscosity reducer, then heat 3. The method for producing activated carbon according to claim 2, wherein the thermosetting resin powder is uniformly mixed into the formed molten mixture at a temperature at which the curable resin remains uncured or partially cured. (4) 2 or 3 in which the pitch viscosity reducing agent has a boiling point of 200°C or higher
4. The method for producing activated carbon according to claim 2, wherein the activated carbon is a cyclic aromatic compound.