JPH06154595A - Molecular sieve carbon for pressure swing type adsorption apparatus - Google Patents

Abstract

PURPOSE:To obtain molecular sieve carbon for a pressure swing type adsorption apparatus having a good separation function, the carbon being in the form of cylinders with a given outer diameter or grains having an internal structure in which a large mumber of primary carbon particles with a given particle size are incorporated irregularly into a three dimensional form to have a given micropore specific volume, particle bulk density, and carbon content. CONSTITUTION:Molecular sieve carbon is obtained which is characterized by: 80vol.% or more of the carbon being in the form of cylinders or grains of 0.8-1.8mm; a large number of primary carbon particles with a particle size of 0.1-50mum being incorporated irregularly into a three dimensional form to constitute an internal structure; 60vol.% or more of the total micropore volume being in a range of 0.1-0.7ml/g in specific volume and 2.8-50Angstrom in micropore diameter; particle bulk density being 0.7-1.2g/cm<3>; carbon content being 85% or more. The molecular sieve carbon having a large adsorption specific volume and selective adsorption characteristics can be used for the separation of a gas mixture of nitrogen and oxygen and other gas mixtures.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pressure swing adsorption device (hereinafter abbreviated as PSA device) having an outer diameter of 0.8 to 1.8 mm.
Of cylindrical or spherical molecular sieving carbon.

[0002]

2. Description of the Related Art In recent years, a pressure swing adsorption method (hereinafter abbreviated as PSA method) has been developed as a technology for separating nitrogen and oxygen in air, and its practical application has been advanced. PSA method is usually 3 ~ 7 kg
It is a method for separating a specific component in a mixed gas by periodically repeating selective adsorption under a pressure of about f / cm ² and regeneration of the adsorbent under reduced pressure or normal pressure.

1948, Emmett (PHEmmett: chem. Rev.
(43 , 69) has obtained molecular sieving carbon by carbonizing vinylidene chloride, and to date, many methods for producing molecular sieving carbon have been proposed, and in recent years, natural products such as coal and coconut shell, and It has become possible to industrially produce molecular sieving carbon using synthetic polymers as main raw materials. For example,
No. 52-18675 discloses that coke having a volatile component content of up to 5% is added with a pyrolytic hydrocarbon at 600 to 900 ° C.
A process for the production of molecular sieving carbon is disclosed in which the carbon released by the treatment at the temperature is deposited in the coke pores. Further, in Japanese Patent Laid-Open No. 62-17690, coconut shell charcoal powder is granulated using a coal tar or a coral pitch as a binder, which is subjected to carbonization at 600 to 900 ° C. to obtain carbonized coal. A process for producing molecular sieving carbon characterized in that a product which has been washed with acid, washed with water and dried is impregnated with cotter, heat-treated at 600 to 900 ° C for 10 to 60 minutes, and then cooled in an inert gas. Is disclosed.

In this way, the technological development of the molecular sieving carbon has progressed and industrial production is being carried out. However, all the molecular sieving carbons for pressure swing adsorption currently used industrially have an outer diameter of 2 to 4 mm. It is a range of pellets. Regarding the reason, firstly, it is generally considered that the separation performance of molecular sieving carbon is controlled by micropore diffusion,
It may have been considered that the effect of the pellet size on the separation performance was negligible. Secondly, from the aspect of granulation technology, high strength pellets that can be used for pressure swing adsorption have an outer diameter of 2
It is considered to be due to the difficulty in manufacturing high-strength pellets with diameters below 4 mm.
Thirdly, when the molecular sieving carbon was packed in the PSA device, it was considered that there was a concern that the pressure loss would increase as the particle size decreased. In recent years, the performance of pressure swing adsorption devices has been improved more and more, and further higher performance of molecular sieving carbon is desired so that high-performance separation and purification can be performed with a smaller amount of molecular sieving carbon.

[0005]

SUMMARY OF THE INVENTION The present inventors have been
Focusing on the outer diameter of the molecular sieving carbon, the correlation with the gas separation performance of which has not been sufficiently examined, as a result of intensive research to solve the above problems, the present invention has been completed, and its purpose The purpose of the present invention is to provide a molecular sieving carbon for PSA devices having an optimum particle shape and excellent separation performance.

[0006]

[Means for Solving the Problems]
Vol% or more is columnar or spherical with an outer diameter of 0.8 to 1.8 mm, has an internal structure in which a large number of primary carbon particles with a particle size of 0.1 to 50 μm are randomly and three-dimensionally integrated, and has micropores. Total volume 0.1-0.7ml / g, pore diameter 2.8-5.0Å, micropore volume is 60vol% or more of the total micropore volume, particle bulk density 0.7-1.2g / cm ³ , carbon content 85% by weight It is achieved by the above molecular sieving carbon.

The shape of the molecular sieving carbon of the present invention is columnar or spherical, and the outer diameter of the molecular sieving carbon refers to the diameter of a cylinder in the case of a column, and the diameter of a sphere in the case of a sphere. In pressure swing adsorption, pressure fluctuations are repeated in a short cycle, so the adsorbent may move up and down, and dust may be generated due to abrasion. Therefore, the shape of the adsorbent is preferably a shape having few corners and less likely to generate dust, such as a columnar shape or a spherical shape.

[0008] Molecular sieving carbon is usually a raw material fine powder,
Since it is formed into pellets using a binder or the like and then carbonized and fired, the carbon particles are aggregated and united to form pellets. The carbon primary particles in the present invention, a thermosetting resin such as phenol resin which is a raw material fine powder, carbonized coke and the like derived from anthracite, brown coal, peat, coconut shell charcoal, the above pellets It refers to the fine carbon particles forming the. The particle size of the carbon primary particles is usually 0.1-
50 μm, preferably 1-30 μm, most preferably 2-20
μm.

The inventors of the present invention produced the molecular sieving carbon of the present invention, in addition to the particle size of the raw material fine powder, the amount of the binder compounded, the amount of the surfactant used, and the specifications of the granulating equipment,
For example, by conducting various studies on the die thickness, die nozzle opening ratio, etc., it was difficult to manufacture an outer diameter of 0.
It enables production of columnar or spherical high-strength molecular sieving carbon with a diameter of 8 to 1.8 mm. This manufacturing technology
For example, a spherical phenol resin disclosed in JP-A-63-201008 is granulated together with a phenol resin having a solid content of 40% by weight or less to form a granular molded body in a non-oxidizing atmosphere. Firing method, or JP-A-62-59510
U.S. Pat.No. 505957, JP-A-1-61306, JP-A-3-4091
No. 2, JP-A-3-411111, JP-A-4-2605, and other known methods can be applied. In short, 80 vol% or more of the whole is outside diameter 0.8 ~
1.8 mm cylindrical or spherical with a particle size of 0.1 to 50 μm
Any molecular sieving carbon having an internal structure in which a large number of primary carbon particles are irregularly united three-dimensionally may be used. The proportion of molecular sieving carbon having an outer diameter of 0.8 to 1.8 mm may be 80 vol% or more, preferably 90 vol% or more, more preferably 95 vol% or more.

Although the classification of pores of activated carbon and molecular sieving carbon is not necessarily constant according to the literature, in the present invention,
Macropores are pores with a pore size of more than 500Å and are composed mainly of interstices of carbon primary particles, and pores of 500 to 20Å that exist in the primary particles inexhaustibly and vertically are branched from mesopores and mesopores. The pores of less than 20Å are defined as micropores. The micropore volume in the molecular sieving carbon of the present invention is determined by measuring the adsorption isotherm measured by the measuring method described below as
It was calculated by using the nin-Astakhov formula. The molecular sieving carbon of the present invention usually has a total micropore volume of 0.1
~ 0.7 ml / g, and the micropore volume in the range of pore diameter 2.8 ~ 5.0 Å is 60 vol% or more of the total volume of micropores.
The total micropore volume is preferably 0.12-0.5 ml / g, the micropore volume in the range of pore diameters 2.8-5.0 Å is 70 vol% or more of the total micropore volume, and most preferably the micropore total volume is 0.15-0.3. The micropore volume in the range of ml / g and the pore diameter of 2.8 to 5.0Å is 80 vol% or more of the total volume of the micropores.

When the total volume of micropores is less than 0.1 ml / g, the adsorption capacity of molecular sieving carbon decreases, and conversely, when the total volume of micropores is greater than 0.7 ml / g, the number of pores with large pore diameter increases. However, it is not preferable because it has almost no selective adsorption property. Since molecular sieving carbon separates molecules such as nitrogen and oxygen or nitrogen and carbon dioxide that have a very small difference in molecular diameter, the micropore volume within the pore diameter range of 2.8 to 5.0 Å is very important. . Micropores of molecular sieving carbon are formed by thermal decomposition of raw materials, carbonization, activation conditions,
The size is controlled by the amount of the pyrolyzed substance such as hydrocarbon added. With the molecular sieving carbon produced in this way, it is difficult to form a large number of pores with a pore diameter of 2.8 Å or less. Therefore, the case where the micropore volume in the range of the pore diameter 2.8 to 5.0 Å is 60 vol% or less of the total volume of the micropores corresponds to the case where there are many pores with a pore diameter of 5.0 Å or more,
It is not preferable because it has almost no selective adsorptivity for molecular sieving carbon. The molecular sieving carbon of the present invention has, as a compositional characteristic, a carbon content of at least 85% by weight, preferably a carbon content of 90% by weight. The molecular sieving carbon of the present invention usually has a particle bulk density of 0.7 to 1.2 g / cm ³ , preferably 0.8 to 1.15 g / cm ³ , and most preferably 0.
It is 9 to 1.1 g / cm ³ . Further, according to the study by the present inventors, even if the outer diameter of the molecular sieving carbon is in the range of 0.8 to 1.8 mm, the pressure loss in the adsorption tower during PSA operation becomes large enough to cause deterioration of the apparatus performance. However, it was revealed that by setting the outer diameter of the molecular sieving carbon within the range of the present invention, a remarkable improvement in the device performance can be obtained.

[0012]

INDUSTRIAL APPLICABILITY The molecular sieving carbon of the present invention has excellent adsorption capacity and selective adsorption characteristics, and therefore, it can be used for the separation of various mixed gases in addition to the gas mixture of nitrogen and oxygen. For example, it can be used to separate a specific gas component from a mixture of hydrocarbon isomers such as butane isomers and butene isomers, a mixture of ethylene and propylene, and the like. In addition to the above-described separation of mixed gas, hydrogen recovery from steam reforming gas, off gas of ethylene plant, methanol decomposition gas, ammonia decomposition gas, coke furnace exhaust gas, etc., or boiler of thermal power plant -It can also be used for separation and recovery of carbon dioxide from exhaust gas.

Next, the measuring method used in the present invention is shown below. (1) Micropore volume measurement method The micropore volume of the molecular sieving carbon of the present invention is measured by using a fully automatic gas adsorption measuring device (BELSORP-28, manufactured by Bell Japan Ltd.) with oxygen (molecular diameter 2.8Å). , Ethane (molecular diameter
4.0Å), isobutane (molecular diameter 5.0Å) 0-760mmHg
, The adsorption isotherm at 298 K was measured, and the Dub of equations (1) and (2)
This was done by organizing using the inin-Astakhov formula. W / W ₀ = exp {-(A / E) ⁿ } (1) A = RTln (P ₀ / P) (2) where W; adsorption amount at equilibrium pressure P W ₀ ; ultimate adsorption amount A; adsorption potential E; adsorption characteristic energy - R; gas constant T; measurement temperature P _0; saturated vapor pressure P; equilibrium n; constant (the case of oxygen n = 2, ethane, in the case of isobutane n = 3)

(2) Method of measuring adsorption amount The adsorption amount of oxygen and nitrogen of the molecular sieving carbon of the present invention was measured using the adsorption characteristic measuring device shown in FIG. In the figure, put 3 g of sample into the sample chamber (4) (200 ml), close valves (11) and (8), open valves (2) and (3), degas for 30 minutes, and then open the valve (2 ), (3) closed, valve (11) opened,
Oxygen gas or nitrogen gas is fed into the sample chamber (5) (200 ml), and when the set pressure (6.000 kgf / cm ² ) is reached, the valve (11)
Was closed and the valve (3) was opened, and changes in internal pressure during a predetermined time were measured to determine the adsorption rates of oxygen and nitrogen. In addition, (1) is a vacuum pump, (6) and (7) are pressure sensors, (9) is a recorder, (14) and (15) are gas regulators,
(16) is a nitrogen cylinder and (17) is an oxygen cylinder.

As an index showing the separation performance of nitrogen and oxygen,
The adsorption amount 1 minute after the start of adsorption was Q ₁ for nitrogen and Q _{2 for} oxygen.
The adsorption amount difference ΔQ is expressed by the following equation (3) ΔQ = Q ₂ −Q ₁ (3), the nitrogen adsorption pressure is P ₁ (atm), and the oxygen adsorption pressure is P ₂ (atm). Was calculated from the following formula (4) α = (Q ₂ / P ₂ ) / (Q ₁ / P ₁ ) (4).

(3) Measurement of carbon content The carbon content of the molecular sieving carbon of the present invention is C
It was analyzed by HN Coder, MT-3. The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

[0017]

Example 1 A phenol resin powder 10 having an average particle diameter of 18 μm
8 parts by weight of a melamine resin aqueous solution (Sumitomo Chemical Co., Ltd., Sumitex Resin M-3, solid content concentration 80% by weight) in solid content, polyvinylalcohol having a polymerization degree of 1700 and a saponification degree of 99%. 4 parts by weight, potato starch 2 parts by weight,
And a surfactant (Perex NB- manufactured by Kao Corporation)
L) 0.7 parts by weight were weighed. First, among the above raw materials, phenol resin powder and potato starch were dry mixed in a kneader for 15 minutes. On the other hand, the polyvinyl alcohol was dissolved in warm water to obtain a 15% by weight aqueous solution, and the polyvinyl alcohol aqueous solution, the melamine resin aqueous solution, and the surfactant were added to the kneader, and the mixture was further mixed for 15 minutes. did. This mixed composition was extruded with a twin-screw extrusion granulator (Peretta Double EXDF-100 type manufactured by Fuji Paudal Co., Ltd.), and the outer diameter was 0.5 mm.
Attempt was made to granulate four kinds of cylindrical granules that become molecular sieve carbon of φ (sample 1), 1.0 mm φ (sample 2), 1.5 mm φ (sample 3), 2.5 mm φ (sample 4). .

Sample 1 having an outer diameter of the molecular sieving carbon smaller than the range of the present invention has an excessive load on the die of the granulator,
Although various conditions such as composition blending amount, die thickness, and die nozzle opening ratio were examined, granulation was impossible, but columnar granular bodies were obtained for the other three samples. After curing and drying each of these pellets at 90 ℃ for 24 hours,
It was put in a 600 mmφ x 2000 mmL rotary kiln and heated up to 800 ° C at 30 ° C / H under a nitrogen stream and kept at that temperature for 1
After holding for a time, the furnace was cooled in a nitrogen atmosphere. In order to evaluate the molecular sieving characteristics of the samples 2 to 4 thus obtained, the adsorption amounts of oxygen and nitrogen were measured by the adsorption characteristic measuring device shown in FIG. The measurement results are shown in Table 1.

[Table 1]

Further, using samples 2 to 4, an experiment for separating nitrogen and oxygen in the air was conducted by the PSA method. A schematic diagram of PSA used in this experiment is shown in FIG. Adsorption tower size is 50 mm inside diameter
φ × 1000 mmL, and molecular sieving carbon was packed in two adsorption towers. First, the air compressed by the compressor was sent to the adsorption tower, the pressure of the adsorption tower was adjusted to 7 kgf / cm ² · G by the gauge pressure, and the desorption regeneration was performed by returning the adsorption tower to the normal pressure. PSA operation is pressure equalization (pressurization) -adsorption-pressure equalization (decompression)-
It was carried out in four steps of exhaust, and switching of each step was performed by controlling the solenoid valve with a sequencer. Table 2 shows PSA operating conditions
Shown in. The measurement results are shown in Table 1.

[Table 2] From Table 1, there is almost no difference in the adsorption characteristics of oxygen and nitrogen between Samples 2 to 4, but Sample 4 with an outer diameter of 2.5 mm, which is outside the scope of the claims of the present invention by PSA evaluation, is as high as Samples 2 and 3. The pure nitrogen could not be taken out.

[0020]

[Example 2] By the same production method as in Example 1, the outer diameter of the particles was 1.2 m.
Attempts were made to produce cylindrical molecular sieving carbons with different particle bulk densities at m 2. The amount of starch added in the granulation process is
The particle bulk density was changed to 1.03 and 1.0, respectively, by changing it to 0, 2, 5, 8 parts by weight relative to 10 parts by weight of the resin powder.
Columnar molecular sieving carbons of 1, 0.83, 0.67 (g / cm ³ ) and samples 5, 6, 7, and 8 were obtained. For the obtained samples 5 to 8, the adsorption characteristics of nitrogen and oxygen were measured and P was measured in the same manner as in Example 1.
An experiment for separating nitrogen and oxygen in the air by the SA method was performed.
The experimental results are shown in Table 3.

[Table 3] As a result of the PSA evaluation, it was not possible to extract high-purity nitrogen gas from Sample 8 having a particle bulk density smaller than the range claimed in the present invention.

[0021]

Example 3 A cylindrical molecular sieving carbon sample 9 was obtained by the same manufacturing method as in the sample 2 of the example 1 by raising the firing temperature to 30 ° C./H up to 1000 ° C. and holding the temperature for 1 hour. For Samples 10 to 13, the firing temperature was raised to 900 ° C. at 30 ° C./H and held for 1 hour, and then steam activation was continued at that temperature for a certain period of time. Activate time 0 minutes, 10 minutes, 30 minutes, 60
Samples with different micropore volumes were obtained by changing the volume. For Samples 9 to 13, the adsorption characteristic measurement of nitrogen and oxygen and the separation experiment of nitrogen and oxygen in the air by the PSA method were conducted as in Example 1. The experimental results are shown in Table 4.

[Table 4] From Table 4, in Sample 9 having a total micropore volume of 0.1 ml / g or less and outside the scope of the claims of the present invention, the selection coefficient α is large, but PSA evaluation could not extract high-purity nitrogen gas. . In Samples 10 to 13, the micropore volume increases as the activation time increases, but the pore diameter
The ratio of the micropore volume in the range of 2.8 to 5.0Å to the total volume of the micropores was small, and the ratio was 60 vol% or less, which was outside the scope of the claims of the present invention. I couldn't take it out.

[0022]

[Brief description of drawings]

FIG. 1 is an adsorption characteristic measuring apparatus used in Example 1.

2 is a pressure swing adsorption (PSA) used in Example 1. FIG.
apparatus.

[Explanation of symbols]

1 Vacuum Pump 2, 3, 8, 11, 12, 13 Valve 4 Sample Chamber 5 Adjustment Chamber 6, 7 Pressure Sensor-9 Recorder 10 Pressure Gauge 14, 15 Gas Regulator 16 Nitrogen Cylinder 17 Oxygen Cylinder 21 Air Compressor 22 air dryer 23, 23a adsorption tower 24, 24a, 27, 27a, 30, 30a, 33, 3
3a, 35, 37 Open / close valve 25, 25a Supply path pipe 28 Exhaust path pipe 29, 29a Extraction path pipe 31 Main pipe 32 Pressure equalizing pipe 34 Surge tank 36 Product gas extraction pipe

[Table 1]

[Table 2]

[Table 3]

Claims (1)

[Claims] 1. Outer diameter is 0.8 to 1.8 mm for 80 vol% or more of the whole.
Columnar or spherical, having an internal structure in which a large number of primary carbon particles having a particle size of 0.1 to 50 μm are randomly and three-dimensionally coalesced, and the total volume of micropores is 0.1 to 0.7 ml / g, The micropore volume in the range of 2.8 to 5.0Å is 60 vol% or more of the total volume of micropores, and the particle bulk density is 0.7 to 1.2 g / c.
Molecular sieving carbon for pressure swing adsorption equipment with m ³ and carbon content of 85% by weight or more.