JPH0340912A - Production of molecular-sieve carbon - Google Patents

Abstract

PURPOSE:To obtain molecular-sieve carbon excellent in sharpness of separation by carbonizing carbonaceous mesophase fine powder or a granulated material obtained by granulating the fine powder and a binder under specified conditions or further activating the carbonized material. CONSTITUTION:Carbonaceous mesophase fine powder or a granulated material obtained by granulating the fine powder and <=40wt.% of the binder is carbonized at 500-1100 deg.C in a nonoxidizing atmosphere, or further the carbonized material is activated at 500-1100 deg.C in an oxidizing atmosphere so that the weight of the carbonized material is reduced by <=15wt.%. A soln. of a thermosetting resin such as liq. phenolic resin and melamine resin, PVA, coal tar, pitch, etc., are exemplified as the binder. The primary grains having about 1-100mum diameter or its secondary agglomerate is used as the carbonaceous mesophase fine powder.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing molecular sieve carbon, and more specifically, to a method for producing molecular sieve carbon having fine pores, which is applied to the field of separation and purification of mixed gases. Concerning the manufacturing method.

(Conventional technique? #) Silica and alumina-based zeolites have been widely used as adsorbents with molecular sieving effects, and play an important role in gas separation and purification. However, the above-mentioned zeolite-based molecular sieves are polar and hydrophilic, have poor heat resistance and chemical resistance, have a strong selective adsorption property for polar substances such as water, and exhibit no molecular sieving effect in the presence of polar substances. It has the disadvantage that it is not.

Recently, however, it has become possible to produce molecular sieves made from carbon, which is nonpolar and hydrophobic.

This type of molecular sieve carbon has excellent heat resistance and chemical resistance.
It is attracting attention as a molecular sieve that can be used even in the presence of polar substances. However, the industrial production of molecular sieve carbon requires complicated steps to control the micropores on the carbon surface, and only complicated and inefficient production methods are used. The performance of this carbon molecular sieve is insufficient for use in the separation of nitrogen and oxygen, and further improvements in separation performance are desired.

(Problems to be Solved by the Invention) The present invention was made in view of the above circumstances, and its purpose is to provide a novel method for producing carbon molecular sieves with excellent separation performance.

(Means for Solving the Problems) The above object is to granulate a carbonaceous mesophase fine powder or a granular compact obtained by granulating a carbonaceous mesophase fine powder together with a binder of 40% or less by weight in a non-oxidizing atmosphere. Carbonize in the temperature range of ~1100°C, or further carbonize in an oxidizing atmosphere to 500~1
This is achieved by the T-filtration method, which is characterized in that activation is performed in a temperature range of 100° C. in a range where the weight of the carbide is reduced within 151 N%.

The carbonaceous mesophase used in the method of the present invention is a low-molecular compound produced when coal tar, coal tar pitch, petroleum heavy oil, etc. is heated at a temperature of about 360°C to 500°C. By repeating the reaction, polynuclear-polycyclic aromatic molecules grow, and some or all of the pitches come to exhibit a liquid crystal state. These carbonaceous mesophases can be obtained by any suitable known method. That is, for example, coal tar or pitch is heat treated at around 400°C, coal tar or pitch is hydrogenated at 510 to 600°C,
It is further produced by heat-treating at approximately 400°C, and by heat-treating naphthalene at 240-500°C in the presence of HF-BFs.

The carbonaceous mesophase fine powder used in the present invention consists of primary particles with a particle size of 1 to 100 μm or secondary aggregates thereof. The particle size of the primary particles is preferably 2 to 50 μm, and more preferably 3 to 50 μm.

Examples of the binder used to mold the carbonaceous mesophase fine powder into a granular molded body include solutions of thermosetting resins such as liquid phenol resin and melamine resin, and polymers such as polyvinyl alcohol or water-soluble or water-swellable cellulose derivatives. A binder, coal tar, pitch, etc. can be used. As polyvinyl alcohol, one having a degree of polymerization of 100 to 5000 and a degree of saponification of 70% or more is preferably used. Further, as the cellulose derivative, for example, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, etc. are preferably used.

In the present invention, the carbonaceous mesophase fine powder is carbonized or activated under predetermined conditions, or the carbonaceous mesophase powder (4) as described above and 3) in a binder are granulated to form a granular compact, and then carbonized. or by activation.

When obtaining a granular compact by granulation, carbonaceous mesophase fine powder (4) and its binder component amount 3) of 40% by weight or less are used.

The amount of the binder component in the present invention is based on the carbonaceous mesophase fine powder (100 parts), and is expressed as the amount of solid content in the binder.

The above components (4) and (B) can be mixed as is, or water or an organic solvent can be added to components (A) and (B) and mixed thoroughly in the presence of those solvents. . Water or an organic solvent can also be added in the form of a solution of the components (4), for example, before mixing the components (4). Water or an organic solvent is preferably used in the raw material mixture (
It is 5 to 30% by weight, more preferably 8 to 20% by weight, based on the solid content of A) [F]). In addition, the ingredients (
A) When mixing (6), in addition to components (A) and CB), for example, starch, derivatives or modified products thereof, etc. are added in an amount of 5 to 50% by weight, preferably 10 to 50% by weight, based on the carbonaceous mesophase fine powder (4). 40! The amount φ can be added.

Components such as starch participate in the generation of pores through thermal decomposition during carbonization in a non-oxidizing atmosphere, which will be described later, and act suitably as a pore-forming material.

In addition, in producing the molecular sieve carbon of the present invention, in order to improve workability without losing its properties, for example, ethylene glycol, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, polycarboxylic acid ammonium salt, etc. A small amount of a surfactant such as, a hardening agent for liquid thermosetting resin, a crosslinking agent for polyvinyl alcohol, a plasticizer for extrusion granulation, etc. can be added.

In the mixing step of component (A)CB), I'f4. The raw materials may be mixed using, for example, a bone mixer, a V-type mixer, a cone mixer kneader, or the like.

The homogeneous mixture prepared in the above process is then formed into granules. Molding into granules can be carried out using, for example, an axle or twin-screw wet extrusion granulator, a rigid granulator such as a basket reaser, a semi-dry disc granulator, or the like.

Particularly, granules granulated by a wet extrusion granulator are preferable because the particles have high strength and the ability to separate molecular sieve carbon after carbonization is high. The shape of the granules is, for example, cylindrical or spherical. The size of the granules obtained by granulation is not particularly limited, but for example, a cylinder has a diameter of 0.5 to 6 m.
m 1 Length: 1 to 10 mm, if spherical, diameter: 0
．． Approximately 5 to 10 mm is preferable.

In order to obtain molecular sieve carbon from carbonaceous mesophase fine powder or granular compacts obtained by granulation, these are carbonized in a temperature range of 500 to 1100°C in a non-oxidizing atmosphere, or further oxidized after carbonization. 5 under atmosphere
Activation is carried out in a temperature range of 00 to 1100°C within a range where the weight of the carbide is reduced within Is weight. The non-oxidizing atmosphere in this case is, for example, nitrogen, argon, helium, or the like. The temperature increase rate until reaching the maximum treatment temperature in the carbonization step is not particularly limited, but is preferably 5 to 8
0 G'C/hr. Further, for example, air, water vapor, carbon dioxide gas, etc. can be used as the oxidizing atmosphere during activation.

(Effect of the invention) By the way, the molecular sieve effect of molecular sieve carbon is such that the pore diameter of the micropores is in the range of several micrometers, which is extremely close to the molecular diameter of the adsorbed molecules, and it is possible to selectively adsorb various substances with different molecular diameters. It is by showing the characteristics. Therefore, the performance of molecular sieve carbon is determined by the pore size distribution of micropores,
As molecular sieve carbon, carbon having a sharp pore diameter distribution, usually 10 A or less, preferably 3 to sAg, is preferable. Further, pores with a diameter of about 15 to 200 A usually do not have a molecular sieving effect, and simultaneously adsorb multiple gases coexisting and solutes in a solution.

Therefore, the smaller the amount of pores within the range of 15 to 200 pore diameters, the more preferable.

The molecular sieve carbon of the present invention has a maximum value of the pore distribution of micropores in the region of pore diameter of 10 μm or less, preferably 3 to 5 A, and the pore volume of IOA or less is preferably 0.1 to 0. ．．
7 cc/g, more preferably 0.16-0.5 cc/
g, and the pore volume of 15 to 200 people with a pore diameter of
Preferably it is 0.1 cmj or less.

The specific surface area of the molecular sieve carbon having the above-mentioned pore structure is usually 2 to 600 ml/g, preferably 10 to 400 ml/g, as measured by the B, E, T method using nitrogen adsorption.
g, most preferably about 60 to 350 ml/g.

In contrast, the commonly used specific surface area is 1000-1
500m! /H activated carbon has a maximum value of the pore size distribution of micropores in the region of about 15A or more, and the pore diameter is 15A or more.
Pore volume ranging from 5 to 20 OA is 0.4 to 1.5 cc
/cr, and does not have molecular sieve properties like the molecular sieve carbon of the present invention.

The molecular sieve carbon of the present invention can be easily produced as described above and has excellent adsorption capacity and selective adsorption properties. Therefore, the molecular sieve carbon of the present invention can be used to separate various mixed gases. For example, a gaseous mixture of nitrogen gas and oxygen gas, a gaseous mixture of methane gas and hydrogen gas, a mixture of hydrocarbon isomers such as xylene isomers, butane isomers, and butene isomers, a mixture of ethylene and propylene, a gaseous mixture of hydrogen gas and methane gas, etc. It can be used to separate gas mixtures containing argon, etc. More specifically, for example, it can be used to obtain nitrogen gas, oxygen gas, or a gas mixture enriched in either nitrogen gas or oxygen gas from a gas mixture containing nitrogen gas and oxygen gas. Alternatively, it can be used to obtain a gas mixture enriched in methane gas, hydrogen gas, or either methane gas and hydrogen gas from a gas mixture containing methane gas and hydrogen gas. For this purpose, it is desirable to employ a pressure swing adsorption method. In pressure swing adsorption method, usually 2
The adsorption tower of the tower or S tower is filled with molecular sieve carbon, and
The mixed gas can be separated by periodically repeating selective adsorption under increased pressure of about 7 kgf/cmt and regeneration of the adsorbent under reduced pressure or normal pressure. In addition to separating the above-mentioned mixed gas, this method can also recover hydrogen from steam reforming gas, ethylene plant off-gas, methanol cracked gas, ammonia cracked gas, coke oven exhaust gas, etc., and carbon monoxide from converter exhaust gas. It can be implemented.

The present invention will be specifically explained below with reference to Examples.

Note that measurements of pore volume, pore size distribution, and gas concentration in Examples were performed by the following methods.

(1) Measurement of pore volume and pore diameter distribution The pore volume and pore diameter distribution of the molecular sieve carbon of the present invention were determined by mercury intrusion method using a porosimeter for pores with a pore diameter in the range of 60 μm to 600 μm. It was measured using Bore Sizer 9310 (manufactured by Shimadzu Corporation).

In addition, for pores with a pore diameter of 80 A or less, it was determined by the following so-called Kelvin equation using crosstalk such as nitrogen gas adsorption.

PggIt Saturated vapor pressure when the adsorbed gas is adsorbed in the pores PO: Saturated vapor pressure of the adsorbed gas under normal conditions γ: Surface tension V; Volume of one molecule of liquid nitrogen R = gas constant T: Absolute temperature of the two pores Kelvin radius The correction for the Kelvin radius of the pore is 0ranston-
It was caused by the Inkley method.

(2) Gas concentration analysis: Analysis was performed using a Shimadzu gas chromatograph aC-am and a zirconia oxygen concentration analysis needle (LO-800 model) manufactured by Toshishima.

Example 1 Carbonaceous mesophase fine powder (Osaka Gas @*・Renoves M
-go) soog was placed in an electric furnace with an inner diameter of 60 mm x 10 x 100 O, heated to a specified temperature at 60°C/hr under a nitrogen atmosphere, and then kept at that temperature for 1 hour. A powder was obtained.

In order to evaluate the molecular sieving properties of this fine carbon powder, the first
The amounts of nitrogen gas and oxygen gas adsorbed were measured using the adsorption property measuring device shown in the figure. In the figure, the sample chamber (4) (2
00ml), put about 10g of sample into it, and press the valve (li).
Close valve (8), open valves (2) and (3), and degas with vacuum pump (1) for 30 minutes, then open valve (2),
(5), open the valve (11), and adjust the adjustment chamber (5) (2).
00ml), close the valve (11) when it reaches the set pressure (7,000 kgf/cm"), and open the valve (3) to measure the change in internal pressure over a predetermined time. Then, the adsorption rates of oxygen and nitrogen were determined.As an indicator of the separation performance between nitrogen and oxygen, the adsorption capacity 1 minute after the start of adsorption is defined as Ql for nitrogen and Q! for oxygen, and the adsorption amount difference △ The selection coefficient α was determined from the following formula (2)% formula %() with Q as the following formula () and the nitrogen adsorption pressure as Pl and oxygen adsorption pressure as P!.

The results of Example 1 above are shown in Table 1.

Sample 1, which was obtained at a heat treatment temperature during carbonization lower than the range of the present invention, had a small amount of oxygen ti and
Both the t difference ΔQ1 selective engagement α are unfavorable as the molecular sieve carbon is small. It can be seen that Samples 2 and 3.4 have large oxygen adsorption amounts and adsorption difference ΔQ selectivity coefficients, and are useful as molecular sieve carbons, with Sample 4 having particularly excellent properties.

In addition, in sample 5, which was obtained at a heat treatment temperature during carbonization higher than the range of the present invention, the selection coefficient α is large, but the oxygen film, f amount, and adsorption amount difference ΔQ are small. Good Example 2 Degree of polymerization 1000 Polyvinyl alcohol with a saponification degree of 88% was dissolved in a predetermined amount of hot water to obtain an aqueous solution of 20 MIk%.

Apart from this, carbonaceous mesophase fine powder (manufactured by Osaka Gas ■, Renoves M-30) and water-soluble resol resin (manufactured by Showa Kobunshi ■, Shifutsu Nor BRL-2864, solid content concentration 6
0M amount%), water-soluble melamine resin (manufactured by Sumitomo Chemical ■,
Sumitex Resin M-5, solid content 80% by weight) Methylcellulose powder (Shin-Etsu Chemical ■ product, Metrose 60SH-4000), Potato! Predetermined amounts of J starch and ethylene glycol were each weighed.

After mixing the above carbonaceous mesophase fine powder, potato starch, and methylcellulose powder in a kneader for 15 minutes, a polyvinyl alcohol aqueous solution, a water-soluble resol resin,
Water-soluble melamine resin and ethylene glycol were added and mixed for an additional 15 minutes.

The mixed composition was extruded using a twin-screw extrusion granulator (manufactured by Fuji Paudal ■, Pelleta Double EXDF-100 model).
Cylindrical pellets with five types of compositions shown in the table were manufactured. The average particle diameter of the cylindrical pellets was 5#XlimmL. After curing and drying the pellets at 80°C for 24 hours, 800g of the pellets were placed in a rotary kiln with an effective diameter of 1001005 x 1000, and the temperature was raised to 900°C at 50°C/H under a nitrogen flow of 21/min. After holding for 1 hour, the mixture was cooled in the furnace.

The nitrogen and oxygen separation performance of the granular carbide thus obtained was measured in the same manner as in Example 1. The results are shown in Table 2.

In Table 2, Sample 8 had poor workability during granulation and could not be granulated. In sample 7, in which the amount of water-soluble polymer binder was greater than the ratio specified in the present invention, 0! It can be seen that the adsorption amount is small and it is not preferable as a molecular sieve carbon.

For samples 8, 9.10.11.12.13, the preferred N
! . 0! Adsorption amount and separation characteristics were obtained, and the characteristics of sample 8 were particularly excellent.

Example 3 A cylindrical pellet precursor with an average particle diameter of 3 mm x 8 mm L, which was granulated with the same composition and under the same conditions as the No. IJ sample of Example 2, was placed in a rotary kiln of 100 x 10 x 100 O, and was heated to a temperature of 21/m1n. aO℃ while flowing nitrogen
The mixture was heated to a predetermined temperature at a heating rate of /H, held at that temperature for 1 hour, and then cooled in a furnace to obtain a carbide.

Table 3 shows the nitrogen and oxygen separation ability of the carbide.

Sample 14, which was obtained at a heat treatment and temperature during carbonization lower than the temperature specified in the present invention, had a small amount of oxygen adsorption, and the adsorption amount difference ΔQ1 selection coefficient α was also small, making it undesirable as a molecular sieve carbon. .

Samples 15, 16, and 17 have oxygen adsorption amount and adsorption amount difference ΔQ1.
It can be seen that both the selectivity coefficients are large and it is practical as a molecular sieve carbon, and the characteristics of sample 16 are particularly excellent.

In addition, in sample 18, which was obtained at a heat treatment temperature during carbonization higher than the temperature specified in the present invention, the selection coefficient α was large, but the oxygen stage! The W amount and adsorption amount difference ΔQ are small, which is not preferable.

Example 4 Using the granular molecular sieve carbon prepared in the same manner as Sample 16 of Example 3, an experiment was conducted to separate nitrogen and oxygen in the air by the pressure swing adsorption (P8A) method.

A schematic diagram of the PEA apparatus used in this experiment is shown in FIG. g&
The size of the tower is the inner diameter S! OXI is 200 mmI, and the above molecular sieve carbon (specific surface area 1
10m”/g>.The packing density is 0.56
g/cmj.

First, air compressed by a compressor is sent to an adsorption tower.
Pressure during adsorption is 4kgf/cm in gauge pressure! The desorption (exhaust) regeneration was carried out by reducing the pressure to about 100 torr using a vacuum pump.

The P8 operation was carried out in 6 steps: pressure equalization (pressurization), stage setting, pressure equalization (pressure reduction), exhaust, and pressure increase, and switching between each step was performed by automatically controlling a solenoid valve with a sequencer.

The P8 system operating conditions are shown in Table 4.

In this experiment, the amount of product nitrogen gas taken out was 11/mln, the purity was 1116% (Nt+Ar), and the precursor had the same composition as Example 5 and Example 4. After being carbonized in an atmosphere for 1 hour, it was subsequently activated in a steam atmosphere for 10 minutes.

The sample taken out after cooling the furnace was a, s based on the carbide weight.
It showed a weight loss of xt.

The granular molecular sieve carbon obtained as described above has a specific surface ff of 610 mF/g and a packing density of 0.53 g/cmi.
Met.

The adsorption A of oxygen and M element on the carbon molecular sieve was measured using the apparatus shown in FIG. Oxygen adsorption amount is adsorption pressure L876kg
f/crnl is g6.6mg/g, nitrogen adsorption amount is adsorption pressure L514kg f/cm! fJ, 7mg/C1, adsorption difference ΔQ = 16.11mg/g, selection coefficient CE = 8.
It was 1.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the adsorption characteristic measuring device used in Examples 1 and 2.3, and FIG. 2 is a schematic diagram of the pressure swing adsorption (P13) device used in Examples 4 and 5. In Figure 1, (1)...vacuum pump・(2) , <5n, (8) , (11) , <
12) , (1ri...valve, (4)...sample chamber, (5)...adjustment chamber, (6), (7)...
...Pressure sensor (8) ...Recorder, (1
0)...Pressure gauge, (14), (15)...Gas regulator (1B)...Nitrogen cylinder, (17)
...Oxygen cylinder. In FIG. 2, (1)...air compressor, (2)...air dryer (RI, (LA)...adsorption tower, (4), (tm)...first on-off valve, (5)
, (6m)...Inflow pipe, (6)...Vacuum pump, (8)...Suction pipe. (8), (9a)... Outlet pipe, (11)...
・Main pipe, (14)... Reservoir tank, (16)... Product gas extraction pipe, (7), (7a), (10), (10a), (13),
(Ha), (15). (17)...Opening/closing valve. Diagram

Claims (1)

[Claims] A granular molded body obtained by granulating carbonaceous mesophase fine powder or carbonaceous mesophase fine powder with 40% by weight or less of a binder is granulated in a non-oxidizing atmosphere to
A molecular sieve characterized by being carbonized in a temperature range of 1,100°C, or further activated after carbonization in an oxidizing atmosphere in a temperature range of 500 to 1,100°C in a range where the weight of the carbide is reduced within 15% by weight. Carbon production method.