JPH03106443A - Globular porous carbon particle and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a globular porous carbon particle useful as a chemically stable packing agent for chromatography having a specific particle size, a specific surface area and high mechanical strength by subjecting globular cellulose to dehydro-condensation treatment and subsequently carbonizing and baking the same. CONSTITUTION:When a globular cellulose particle having a mean particle size of 3-300mum (the problem such as deformation or fixing of a particle at the time of heat treatment can be solved when cellulose is used as a carbon source) is dried if necessary to be used. At first, the cellulose particle is subjected to dehydro-dehydration treatment under heating at about 100-400 deg.C for about 3-6hr in a vacuum or inert gas atmosphere and subsequently carbonized and baked at about 500-3000 deg.C in an inert gas atmosphere using an electric furnace or rotary kiln. Especially, when the particle is carbonized and baked at about 2000-3000 deg.C, the hardness of the globular carbon particle obtained by the generation of graphitization is enhanced and the aromatization of cellulose generated during the carbonizing process is eliminated. By this method, the globular porous carbon particle having a mean particle size of 1-300mum, a specific surface area of 50-1000m<2>/g and high mechanical strength is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to spherical porous carbon particles. More specifically, the present invention relates to spherical porous carbon particles useful as adsorbents for gases or organic substances, carriers for immobilizing functional substances, or fillers for liquid chromatography.

[Prior Art and Problems to be Solved by the Invention] Porous carbon particles have heretofore been used as catalyst carriers, adsorbents, and the like. In addition, recently, porous carbon particles have been attracting attention and investigation as a packing material for artificial organs such as artificial livers and artificial kidneys, and for liquid chromatography due to the following characteristics.

General characteristics of porous carbon particles are shown below.

(1) High mechanical strength.

(2) The specific surface area is 50 to 500 rd/t, which is suitable for appropriate retention.

(3) Possesses micropores of 5 nm or more for easy mass transfer.

(4) Interaction sites are uniformly distributed on the particle surface.

(5) Buffer solutions with a wide pH range can be used, and chemical stability is good.

(6) Theoretically non-polar and inert.

(7> Good heat resistance.

(8) It has morphological stability.

The above features almost satisfy the requirements for the above-mentioned applications such as liquid chromatography packing material. The present invention provides carbon particles that can be used as packing materials for liquid chromatography.

The method for producing porous carbon particles generally involves press-molding carbon black and a resin binder, then carbonizing and firing, and crushing the oval bodies obtained after firing to obtain particles with a desired particle size.

However, the particles obtained by crushing the cylindrical body cannot be said to be spherical because they are crushed, and the particle size distribution is also wide, making them insufficient as a filler for liquid chromatography. To compensate for these drawbacks, carbon black is spheroidized in advance, impregnated with a binder, and fired, or spherical particles of synthetic polymers such as polyacrylic resin, polystyrene resin, phenol resin, polyvinyl chloride, etc. are used as the carbon source. A method of heat treatment and carbonization has been proposed (JP-A-53-48989, JP-A-54-
4 1 296).

However, in any of these methods, during the calcination heat treatment, interparticle fixation, breakage, and agglomeration occur due to the fusion angle of the binder or synthetic polymer, making it difficult to obtain uniform spherical particles.

In order to prevent melting during heat treatment, for example, JP-A If? {As described in Japanese Patent No. 53-48989, treatments such as sulfonation and nitration have been carried out, but the effects were not sufficient.

[Means to solve the problem]

The present inventors found that cellulose is a substance that does not melt or soften when heated, and that problems such as particle deformation and sticking during heat treatment can be resolved by using cellulose as a carbon source. Thought. The present inventors conducted research in accordance with this idea, and found that uniform spherical carbon particles can be easily obtained by subjecting cellulose spherical particles to dehydration condensation treatment and then heat treatment, and that the properties of the spherical cellulose used We discovered that the porosity of spherical carbon particles can be controlled. Based on this knowledge, we further investigated and arrived at the present invention.

The present invention includes the following.

(1) Average particle size is 1 to 300 μm and specific surface area is 5
Spherical porous carbon particles having a particle size of 0 to 1000 rrr/g.

(2) A method for producing spherical porous carbon particles, which comprises dehydrating and polymerizing spherical cellulose and then carbonizing it.

The spherical cellulose particles used in the present invention are truly spherical, and methods for producing them include the following examples, but are not particularly limited.

■ By the method described in JP-A No. 11r{53-86749, cellulose acetate is dissolved in an organic solvent. A method in which this solution is suspended in an aqueous solvent and spheroidized, the organic solvent is evaporated to obtain cellulose ester particles, which are then saponified to become cellulose particles.

(2) A method disclosed in JP-A-56-24429, in which the porosity is adjusted by adding an aliphatic higher alcohol or the like to a solution of cellulose acetate as an application of the method (2).

■ Unexamined patent publication 11fl in which cellulose is granulated by dissolving it in a mixed solvent of rose formaldehyde and dimethyl sulfoxide.
57-159801 Publication, Special Publication IM
{The method disclosed in 57-1 59802.

■ JP-A 11r { 5 2 -1 in which cellulose is dissolved in concentrated ammonia water containing cupric hydroxide and cuprous chloride and granulated
The method of Publication No. 1237.

■ A method disclosed in Japanese Patent Application Laid-Open No. 51-5361, in which viscose is dispersed and granulated in a transformer well.

■ JP-A No. 4,555-443, in which cellulose is dissolved in a calcium thiocyanate salt solution and granulated.
1 Method of Publication No. 2.

(2) A method disclosed in Japanese Patent Application Laid-open No. 48-60754, in which Kozue-made linter is dissolved in a copper ammonia solution and granulated.

(2) The method disclosed in JP-A-61-241337 flJ, in which viscose and a water-soluble anionic polymer compound are mixed to form a viscose dispersion, which is then heated and coagulated.

The spherical cellulose particles used have an average particle diameter of 3 to 300μ.
It is better to use m.

If the spherical cellulose particles contain water or the like, they are usually used dry. The drying method is not particularly limited, but includes, for example, a method in which most of the liquid is removed through an oven and then dried by heating, a method in which the material is substituted with a solvent such as alcohol, ether, or acetone, and then dried under reduced pressure.

The cellulose particles are first subjected to a heating dehydration condensation treatment (preliminary carbonization). This treatment is carried out at 100-400°C, preferably at 20°C.
The reaction is carried out at 0 to 300°C for 3 to 6 hours, and can be carried out in vacuum or in an inert gas atmosphere, but it is also effective to carry out the reaction in the presence of an acidic gas, such as dry hydrogen chloride gas, to accelerate the reaction.

In order to carbonize and fire the cellulose particles, it is preferable to heat and fire them in an atmosphere of an inert gas such as nitrogen or argon using an electric furnace or a rotary kiln.

For uniform carbonization and firing, a non-fixed furnace such as a rotary kiln or a fluidized bed furnace is preferable. If the firing temperature is too low, carbonization will not proceed, and if it is too high, the carbonization will not proceed, so it is usually desirable to set the firing temperature to 500 to 3000°C. In particular, when carried out at 2,000 to 3,000°C, graphitization occurs, increasing the hardness of the resulting spherical carbon particles, eliminating the aromatization of cellulose that occurs during the carbonization process, and reducing unnecessary non-specific adsorption during chromatography operations. There is an advantage to doing so.

Regarding the heating rate, if it is too fast, the shape of the spherical particles cannot be maintained, so the heating rate should be 5°C to 1000°C/hour, preferably 50°C.
~500°C/hour is preferred.

The firing time depends on the temperature increase rate. 50℃～500℃/
If the heating rate is 1 hour, the desired temperature will be reached and then 0.
Carbonization and firing can be achieved in 1 to 24 hours.

In this way, spherical porous carbon particles having an average particle diameter of 1 to 300 μm and a specific surface area of 50 to 1000 rrl''/g can be obtained.

〔Example〕

As an example, a method for producing spherical carbon particles using spherical cellulose particles as a starting material and an example of the use of the obtained particles will be shown below, but the present invention is not limited to these examples.

In the following examples, the average particle diameter was measured using a coal counter (model TAII, manufactured by Nakanikaki Ki). In addition, the specific surface area is measured using a specific surface area measuring device (Model 2205 manufactured by Shima Ritsu Seisakusho ■)
It was measured by the BET low temperature adsorption method using argon.

Example 1 100g of suction-dried cellulose particles produced by the method of Example 1 of JP-A-11N55-44312 was washed sequentially with 240ml each of methanol, ethanol, and ether to perform solvent replacement. After filtering, vacuum drying was performed using a rotary evaporator. The obtained dried cellulose particles were further heat-treated at 300° C. for 3 hours in a dry hydrogen chloride gas atmosphere to perform a dehydration condensation treatment.

The obtained particles were heated in a nitrogen stream for 30 minutes using a rotary kiln.
The temperature was raised to 0° C. for 4 hours and from 300° C. to iooo° C. in 14 hours, and carbonized and fired at this temperature for 4 nq to obtain spherical carbon particles 81r.

The average particle size of the obtained carbon particles was 13 μm, and the specific surface area was 6.
It was 80rd/g.

Example 2 A suction-dried product of cellulose particles produced by the method of Example 1 of JP-A No. 11fl56-24429. 200K was mixed with 40% each of dioxane and ether.
0m! After washing with and replacing the solvent, vacuum drying was performed using a rotary evaporator. The obtained dried cellulose particles were further heat-treated at 350° C. for 4 hours in a dry hydrogen chloride atmosphere to perform a dehydration condensation treatment.

The obtained particles were placed in a fluidized bed furnace in an argon gas atmosphere.
The temperature was raised to 000°C for 20 hours, then to 2800°C for 21 hours, and carbonized and fired at 2800°C for 0.5 hours to obtain spherical porous carbon particles 15. I got it.

The average particle size of the obtained carbon particles was 25 μm, and the specific surface area was 5.
It was 2rrr/sr.

Example 3 Suction drying of commercially available cellulose beads (Cellulofine (trademark) GC type manufactured by Chisso ■) 50
Wash 0g with 21 methanol and 1I ethanol,
After the solvent was replaced, it was filtered and vacuum dried using a rotary evaporator.

The obtained cellulose particles were further heat-treated at 300° C. for 6 hours in a dry hydrogen chloride gas atmosphere to perform a dehydration condensation treatment, and then the particles were washed with 1.2 g of acetic acid, filtered, and vacuum-dried in a rotary evaporator.

The obtained particles were heated in a rotary kiln at 300°C to 1000°C for 4 hours in an argon gas atmosphere.
The temperature was raised from 1,000°C to 2,200°C in 5 hours, and carbonized and fired at 2,200°C for 2 hours to form spherical carbon particles. I got it.

The obtained carbon particles have an average particle size of 6 μm and a specific surface area of 3
It was 75 td/g.

Comparative Example 1 In Example 3, commercially available polyacrylic beads (Oibergift (trademark)) were used instead of cellulose beads.
(manufactured by Roha Pbarsa) under the same conditions except that 28 g of carbon particles were obtained.

The average particle size of the obtained carbon particles was unmeasurable because they were in the form of agglomerates, and the specific surface area was 0.3 rrr/g.

Comparative Test 1 In order to compare the particles obtained in Example 3 and Comparative Example 1, each particle was observed using a scanning electron microscope photograph.

This is shown in Figures 1 and 2. Shown below.

Porous carbon particles using cellulose beads as starting material are
It can be seen that each individual bead maintains a beautiful spherical shape, whereas the polyacrylic beads have a poor fusion angle, stick together, and aggregate.

This viscosity reveals that the carbon particles of the present invention are uniform spherical particles.

Usage Example 1 The spherical carbon particles obtained in Examples 1 to 3 were packed into a stainless steel ram for liquid chromatography with an inner diameter of 8 mm and a length of 100 m, and the solution was MeOH/H20- as a liquid.
FIG. 3 shows the elution behavior when benzoic acid esters were subjected to chromatography using 60/40 (v/v).

The horizontal axis shows the number of carbon atoms in the eluted benzoic acid esters. In each of the spherical carbon particles of Examples vq1 to 3, K' increases as the number of carbon atoms increases, and it can be seen that they are excellent packing materials for liquid chromatography capable of separating organic compounds.

〔Effect of the invention〕

As explained above in detail, according to the present invention, fixation, clumping,
It is possible to produce uniform spherical carbon particles in high yield without agglomeration. The spherical carbon particles obtained in this way have high mechanical strength and a specific surface area of 50 to 1000rd”/
It has all the characteristics of a packing material, such as a high chemical stability, and is useful as an adsorbent for polymeric substances, a packing material for chromatography, etc.

[Brief explanation of drawings]

Figures 1 and 2 are scans of each particle obtained in Example 3 and Comparative Example 1, respectively! This is a micrograph of a 2rr single child. Figure 3 shows the result of liquid chromatography using the spherical carbon particles obtained in Examples 1 to 3. FIG. 2 is a diagram showing the relationship between the capacity factor K' and the carbon number of benzoate esters when acid esters are separated. Figure 1 B℃! j””)7. t l 1θ,, second
Zumon Akira Bo,

Claims (1)

[Claims] 1. The average particle size is 1 to 300 μm and the specific surface area is 50 μm.
Spherical porous carbon particles with ~1000 m^2/g. 2. A method for producing spherical porous carbon particles, which comprises subjecting spherical cellulose to dehydration condensation treatment, followed by carbonization and firing.