JP2002211911A - Carbonized material containing hydroxyl group derived from hydrophilic polymer and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbonized material containing hydroxyl groups derived from a hydrophilic polymer, having a large gas (oxygen) adsorption and a large difference between oxygen and nitrogen adsorptions, easy to regenerate, obtained using inexpensive starting materials in an easy production process and suitable for use as an adsorbent in PSA based on difference of adsorption equilibria. SOLUTION: The carbonized material has (a) 1-50 ml/g oxygen adsorption in the standard state and (b) an oxygen adsorption to nitrogen adsorption ratio (O2/N2) of 2-40 in the standard state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydroxyl group-containing carbide derived from a hydrophilic polymer, which is suitable as an adsorbent used in a method for separating a mixed gas such as air, and a method for producing the same.

[0002]

2. Description of the Related Art At present, combustion by air is generally performed. However, since air contains a large amount of nitrogen unnecessary for combustion, not only thermal efficiency is poor, but also nitrogen oxide generated is generated. There is a problem that enormous energy is required for recovering carbon dioxide.

On the other hand, the oxyfuel combustion using pure oxygen not only improves the thermal efficiency but also enables the recovery of harmful gas and carbon dioxide gas easily and at low cost due to the small amount of exhaust gas. The generation of objects can be suppressed. Therefore, oxyfuel combustion is greatly expected as a future combustion technology that is energy-saving and friendly to the global environment. However, at present, there is an economic problem because it is difficult to obtain pure oxygen at low cost.

As a method for separating a mixed gas such as air, PSA (Pressure Swing Adso) is used.
rption) is well known. This method is a method utilizing the difference in the amount of adsorption or the adsorption speed of each component of the mixed gas to the adsorbent. For example, when the mixed gas is composed of two types of components, the mixed gas is adsorbed at a certain high pressure. By flowing for a certain period of time, the component with the higher adsorption amount or adsorption rate is adsorbed by the adsorbent, the other components are taken out, and then the adsorbed component is desorbed from the adsorbent by lowering the pressure to reduce the adsorbent. Is a method of separating a mixed gas for each component by repeating a series of steps of regenerating the mixed gas.

As the adsorbent for gas separation in the PSA, synthetic zeolite, natural zeolite, silica gel, alumina gel, activated carbon, molecular sieve carbon and the like are used. In particular, zeolite and molecular sieve carbon are mainly used for separating oxygen and nitrogen in the air. Zeolite is an adsorbent having a larger equilibrium adsorption amount of nitrogen than oxygen, and a PSA utilizing such a difference in the equilibrium adsorption amount of the adsorbent is called an equilibrium separation type PSA. Also, molecular sieve carbon is an adsorbent having a higher oxygen adsorption rate than nitrogen, and PSA utilizing such a difference in the adsorption rate of the adsorbent.
Is called a speed separation type PSA.

[0006] By the way, oxygen contains about 21% of oxygen.
(Volume) and about 78% (volume) of nitrogen
In the PSA, it is preferable to use an adsorbent that adsorbs oxygen having a lower content than nitrogen having a higher content. Therefore, molecular sieve carbon in rate-separated PSA is preferred in that sense. On the other hand, equilibrium separation type P
Most adsorbents conventionally used for SA adsorb more nitrogen than oxygen, such as zeolites. Therefore, if there is an adsorbent in an equilibrium separation type PSA that can adsorb more oxygen than nitrogen, the separation of oxygen and nitrogen in the air can be performed more efficiently. Was desired.

As one of such adsorbents, trinuclear acetate metal ions are inserted between the layers of the layered silicate by an ion exchange reaction, and heat-treated in air to form a metal oxide layer between the layers. Layered compounds obtained by crosslinking have been developed (JP-A-9-192483). The layered compound can adsorb more oxygen than nitrogen, and can more efficiently separate oxygen and nitrogen in air than when a conventional adsorbent such as zeolite is used. However, the difference between the gas adsorption amount of oxygen or the like and the adsorption amount of oxygen and nitrogen of the layered compound is not sufficiently satisfactory for practical use. Callation, solid-liquid separation,
The production process such as washing is complicated, and the raw materials are expensive.

[0008]

SUMMARY OF THE INVENTION The present invention provides an equilibrium separation type P which has a large difference between the amount of adsorbed gas such as oxygen and the amount of adsorbed oxygen and nitrogen, has a low raw material cost, and is easy to manufacture.
It is an object of the present invention to provide a hydrophilic polymer-derived hydroxyl group-containing carbide suitable as an adsorbent for SA, particularly as an adsorbent for separating a mixed gas of oxygen and nitrogen such as air into oxygen and nitrogen.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object. As a result, (a) the amount of oxygen adsorbed in a standard state is 1 to 50 mL / g, and (b) The ratio of the amount of oxygen adsorbed to the amount of nitrogen adsorbed in the standard state (O ₂ / N ₂ ) is 2 to 40, and a part of the hydroxyl group-containing carbide derived from a hydrophilic polymer (a hydroxyl group-containing carbide derived from a hydrophilic polymer) ), The above object is achieved, and the present invention has been completed.

That is, the present invention is as follows. [1] Hydroxyl-containing carbide derived from a hydrophilic polymer having the following properties: (a) Oxygen adsorption amount in a standard state is 1 to 50 mL / g
(B) The ratio (O ₂ / N ₂ ) between the amount of adsorbed oxygen and the amount of adsorbed nitrogen in the standard state is 2 to 40. [2] The hydroxyl-containing carbide derived from a hydrophilic polymer according to the above [1], wherein the hydrophilic polymer is cellulose. [3] The oxygen adsorption amount in the standard state is 3 to 40 mL / g
The hydroxyl group-containing carbide derived from a hydrophilic polymer according to the above [1] or [2]. [4] The hydroxyl group-containing carbide derived from a hydrophilic polymer according to any one of [1] to [3], wherein O ₂ / N ₂ in a standard state is 5 to 30. [5] The method includes: (1) a step of impregnating a hydrophilic polymer with an aqueous solution of a basic substance; and (2) a step of carbonizing the impregnated hydrophilic polymer at 150 to 500 ° C. The method for producing a hydroxyl group-containing carbide derived from a hydrophilic polymer according to any one of the above [1] to [4]. [6] An adsorbent comprising a hydroxyl group-containing carbide derived from a hydrophilic polymer according to any one of the above [1] to [4].

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION "Hydrophilic polymer
Hydroxyl-containing carbide (hereinafter referred to as hydroxyl-containing carbide)
") Means a hydrophilic polymer in which some of the hydroxyl groups remain.
Carbide of origin, i.e.,
The aqueous polymer is carbonized so that some of the hydroxyl groups remain.
It was something that worked. In addition, the said hydroxyl group containing carbide is hydroxyl.
The presence of the group is determined by measuring the infrared absorption spectrum.
3800-3200cm ^-1Of O-H stretching vibration
Absorption band and 1400-1250cm^-1OH bending vibration
Can be confirmed by finding the absorption band of
You.

In the present invention, the "standard state"
25 ° C. and 101.3 kPa.

The hydroxyl group-containing carbide of the present invention is a carbide in which a part of hydroxyl groups of a hydrophilic polymer remains, and (a) an oxygen adsorption amount in a standard state is 1 to 50 mL / g;
And (b) the ratio of the amount of oxygen adsorption to the amount of nitrogen adsorption in the standard state (O ₂ / N ₂ ) is 2 to 40, that is, it has excellent oxygen adsorption capacity and oxygen selectivity.

The hydrophilic polymer serving as a raw material of the above-mentioned hydroxyl group-containing carbide is not particularly limited as long as it swells in water. Examples thereof include natural cellulose (pulp, kenaf, cotton, hemp, etc.) and regenerated cellulose. (Cellophane, rayon, cellulose beads, cellulose sponge, etc.), bacterial cellulose, and cellulose derivatives such as ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylhydroxyethylcellulose and carboxymethylcellulose, which have been chemically modified with cellulose, and silk, wool, Polyvinyl alcohol, cross-linked polyvinyl alcohol, chitin,
Natural or artificial hydrophilic polymers such as chitosan, ethylene vinyl acetate copolymer, polyvinyl acetal (polyvinyl formal, polyvinyl butyral, etc.), superabsorbent polymer gels such as polyacrylamide, collagen and the like. Preferably, cellulose (particularly, regenerated cellulose) is used in terms of actual use form, price, and ease of handling. Further, two or more hydrophilic polymers may be used in combination.

If necessary, the hydrophilic polymer may be, for example, alcohols (methanol, ethanol, propanol, butanol, glycerin, etc.), phenols (phenol, pyrocatechol, pyrogallol, cresol, resorcinol, naphthol, hydroquinone, Contains hydroxyl-containing organic compounds such as phloroglucinol, 1,2,4-benzenetriol, etc., and carboxylic acids (formic acid, acetic acid, propionic acid, benzoic acid, p-hydroxybenzoic acid, phthalic acid, terephthalic acid, etc.). May be. The hydroxyl group-containing organic compound can assist the hydrophilic polymer in carbonizing such that some hydroxyl groups remain.

The hydrophilic polymer may be waste such as waste paper, cellophane waste, fiber waste or the like, or may be one subjected to a treatment such as crosslinking or dyeing. Furthermore, as long as the object of the present invention can be achieved, organic polymers other than hydrophilic polymers (eg, polyester, polyethylene, polypropylene, acrylic, aramid, polyvinyl chloride, polyacrylonitrile, nylon, polyamide) , And polyurethane).

In the hydroxyl group-containing carbide of the present invention, the amount of oxygen adsorbed under the standard condition is 1 to 50 mL / g, preferably 3 to 40 mL / g, more preferably 5 to 30 mL / g.
It is. When the oxygen adsorption amount is less than 1 mL / g,
When used as an oxygen adsorbent or the like in an equilibrium adsorption type PSA, it is not preferable because the processing capacity is small, so that not only the device becomes large but also the power required for operating the device becomes a heavy load. On the other hand, the oxygen adsorption amount is 50 m
Those exceeding L / g are difficult to manufacture, and their strength is extremely low, and they disintegrate during the operation, causing problems such as contamination of related equipment and clogging of paths. The amount of oxygen adsorbed here is the amount (volume) of oxygen adsorbed per unit weight of the hydroxyl group-containing carbide.
And a fully automatic gas adsorption device (Bell Japan, Ltd .: B
This is a value measured by a capacity method using ELSORP 28SA) (that is, a method of measuring a pressure difference before and after gas adsorption and applying it to a gas state equation to convert to a volume).

Further, in the hydroxyl group-containing carbide of the present invention, the ratio of the oxygen adsorption amount to the nitrogen adsorption amount (O
₂ / N ₂ : That is, the value obtained by dividing the oxygen adsorption amount by the nitrogen adsorption amount in the standard state) is 2 to 40, preferably 5 to 30,
More preferably, it is 7-20. When the ratio of O ₂ / N ₂ is less than 2, it is difficult to efficiently separate oxygen and nitrogen from a mixed gas of oxygen and nitrogen such as air, and a necessary amount of oxygen (or nitrogen) is mixed. A large amount of mixed gas is required to obtain by gas separation. On the other hand, the O ₂
Those having a ratio of / N ₂ exceeding 40 are difficult to produce. The oxygen adsorption amount and nitrogen adsorption amount here are the amount of oxygen (volume) and the amount of nitrogen (volume) adsorbed per unit weight of the hydroxyl group-containing carbide, respectively, and are the values measured by the above-mentioned volume method. is there.

The form of the above-mentioned hydroxyl group-containing carbide is not particularly limited, and examples thereof include sheet, granular, fibrous, thread, rod, tubular, plate, corrugated honeycomb,
Examples include irregularly shaped objects. They may also be porous. After being made into a hydroxyl group-containing carbide, it can be processed into a predetermined form, but a flexible polymer having flexibility and easy handling is manufactured or processed in a predetermined form in advance, and then carbonized. It is easy and preferable.

The above-mentioned hydroxyl group-containing carbide is obtained by (1) a step of impregnating a hydrophilic polymer with an aqueous solution of a basic substance;
(2) The impregnated hydrophilic polymer is heated at 150 to 500 ° C.
And carbonizing.

(Step of Impregnating Hydrophilic Polymer with Aqueous Solution of Basic Substance) In this step, the hydrophilic polymer is swelled by impregnating the hydrophilic polymer with the aqueous solution of the basic substance. In this step, a large amount of OH ^- ions are contained inside the structure.

Examples of the basic substance in the aqueous solution of the basic substance include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, and alkaline earth metals such as calcium hydroxide and magnesium hydroxide. Hydroxide and ammonia, among which alkali metal hydroxides, especially sodium hydroxide and potassium hydroxide, are inexpensive and easy to handle, and the swelling degree of the hydrophilic polymer is high. Is preferred, and sodium hydroxide is particularly preferred because of the good heat resistance of the hydroxyl group-containing carbide finally obtained. The concentration of the basic substance in the aqueous solution is not particularly limited, but is usually 0.0
1 to 10 mol / L, preferably 0.1 to 7 mol / L,
More preferably, it is 0.5 to 5 mol / L.

The method of impregnating the hydrophilic polymer with the aqueous solution of the basic substance is not particularly limited. For example, the hydrophilic polymer is immersed in the aqueous solution, the hydrophilic polymer is sprayed with the aqueous solution, or the hydrophilic polymer is sprayed. For example, a method of applying the aqueous solution to the hydrophilic polymer using various coaters can be used. Also,
The amount of the aqueous solution with respect to the hydrophilic polymer is not particularly limited, and may be appropriately set according to the type of the hydrophilic polymer, the impregnation method, and the like.For example, when the aqueous polymer is impregnated with the hydrophilic polymer, May be carried out usually using 1 to 100 times (by weight), preferably 10 to 50 times (by weight) of the aqueous solution of the hydrophilic polymer.

The treatment temperature and the treatment time in the above-mentioned impregnation treatment are not particularly limited, and may be appropriately set according to the kind of the hydrophilic polymer to be used. The temperature is preferably from 5 to 90 ° C., from the viewpoint of sufficiently penetrating the basic substance into the inside of the structure and sufficiently acting on the hydroxyl group, and suppressing the hydrolysis of the hydrophilic polymer. Preferably 10-6
The temperature is 0 ° C, particularly preferably 20 to 40 ° C, and the treatment time is preferably 1 to 72 hours, more preferably 2 to 60 hours, and particularly preferably 5 to 48 hours.

In addition, in the above-mentioned impregnation treatment, it is preferable to perform the treatment while gently stirring the treatment liquid, since the hydrophilic polymer may float on the water surface due to the specific gravity.

The impregnated hydrophilic polymer is preferably washed with water in order to remove excess basic substances. The amount of water used for washing, if the washing is performed with a large amount of water, when carbonized, the basic substance is excessively removed, and there is a possibility that a hydroxyl group-containing carbide having excellent properties may not be finally obtained. For this reason, the amount is preferably about 10 times the used processing solution.

Further, it is preferable that the washed hydrophilic polymer is slowly dried under mild temperature conditions before the carbonization treatment. For example, drying is performed under a temperature condition of 30 to 70 ° C (preferably 40 to 60 ° C) for 12 to 48 hours (preferably 16 to 36 hours). By performing the drying, it is possible to suppress the localization of the basic substance along with the movement of water inside the structure during the rapid heat treatment in the carbonization treatment.

(Carburizing Step) In the carbonizing step, the hydrophilic polymer impregnated with the aqueous solution of the basic substance is treated with:
This is a step of carbonizing the hydrophilic polymer by treating at 150 to 500 ° C. so that some of the hydroxyl groups remain.

The treatment temperature in the carbonization treatment is 150
To 500 ° C, preferably 180 to 450 ° C, more preferably 200 to 400 ° C. If the temperature is lower than 150 ° C., carbonization does not proceed sufficiently, and the difference between the amount of adsorption of oxygen and the like and the amount of adsorption of oxygen and nitrogen of the obtained hydroxyl group-containing carbide is not sufficient. On the other hand, when the temperature exceeds 500 ° C., carbonization proceeds excessively, and various groups such as a hydroxyl group, which are considered to be involved in oxygen adsorption, are also decomposed, so that not only the oxygen adsorption capacity and oxygen selectivity are reduced, but also The strength of the resulting hydroxyl-containing carbide also tends to decrease.

The treatment time in the carbonization treatment is not particularly limited, and may be appropriately set according to the type of the hydrophilic polymer to be treated, the impregnation condition, the treatment temperature, and the like, and is usually from 10 minutes to 50 hours. , Preferably 30 minutes to 30 hours, more preferably 1 to 20 hours.

In the carbonization step, in order to suppress the oxidative decomposition of the hydrophilic polymer, a vacuum (usually 1.0 Pa or less, preferably 0.01 Pa or less) or an inert gas (for example,
(Helium, argon, etc.) atmosphere, and also to remove volatile low-molecular compounds (eg, carbon dioxide, propanol, butanol, etc.) which adversely affect the oxygen adsorption capacity generated as carbonization proceeds. In particular, it is preferable to perform the reaction under a vacuum.

Hereinafter, the above-mentioned production method will be specifically described by taking as an example a case where cellulose beads (ie, an industrial material obtained by shaping viscose as a raw material of cellophane into a spherical shape at the time of regeneration) are used as the hydrophilic polymer. I do.

First, the cellulose beads were added to 10 to 5
An aqueous solution of a basic substance such as sodium hydroxide adjusted to 0.5 to 1.5 mol / L of 0 times (weight) is added to an aqueous solution of 20 to 30 mol / L.
Soak at 15 ° C. for 15 to 48 hours. Next, the cellulose beads are taken out, washed with about 10 times the amount of water, and dried with a dryer set at 50 to 60 ° C for 12 to 48 hours. Next, the dried cellulose beads are placed in a vacuum (usually 1.0 Pa or less, preferably 0.01 Pa or less).
By performing a heat treatment at 200 to 400 ° C. for 10 to 20 hours under (Pa or lower), a carbide of cellulose beads in which some hydroxyl groups remain can be obtained. Further, the fact that a hydroxyl group remains in the carbide can be confirmed by measuring an infrared absorption spectrum.

The properties of the hydroxyl group-containing carbide obtained as described above, that is, (a) a high oxygen adsorption capacity such that the oxygen adsorption amount in the standard state is 1 to 50 mL / g, and (b) a characteristic in the standard state The high oxygen selectivity such that the ratio of the amount of oxygen adsorption to the amount of nitrogen adsorption (O ₂ / N ₂ ) is 2 to 40 means that the amount of oxygen adsorption is low and that nitrogen adsorbs more nitrogen than oxygen or slightly. This is a surprising property that cannot be expected from conventional adsorbents that have either adsorbed much oxygen.

In addition, the hydroxyl group-containing carbide has not only high oxygen adsorption ability and oxygen selectivity, but also can easily desorb adsorbed oxygen, and can be reused after desorption. That is, it can be easily reproduced. For example, in the case of a hydroxyl group-containing carbide derived from cellulose beads, it can be regenerated by desorbing the adsorbed oxygen by heating to 200 to 400 ° C. under vacuum (usually 1.0 Pa or less, preferably 0.01 Pa or less). .

The above characteristics possessed by the hydroxyl group-containing carbide of the present invention are very desirable characteristics as an adsorbent in an equilibrium separation type PSA for separating a mixed gas, particularly a mixed gas composed of oxygen and nitrogen such as air, into oxygen and nitrogen. It is. Accordingly, the hydroxyl group-containing carbide of the present invention can be used, for example, in the semiconductor industry, the chemical industry (synthesis, etc.), iron mining, fuel cells, internal combustion engines, adsorption towers, medicine / medicine, biotechnology (eg, culture of aerobic bacteria). , Plant culture, propagation of algae such as chlorella, supply of high-purity oxygen such as wastewater treatment (reduction of COD, suppression of propagation of anaerobic bacteria, etc.), removal of oxygen or supply of high-purity nitrogen is required. In a wide range of fields, it can be suitably used as an adsorbent, an oxygen adsorbent, a separator for oxygen and nitrogen in an equilibrium separation type PSA, and the like. Further, the hydroxyl group-containing carbide is easy to industrialize because the raw material is inexpensive and the production process is easy.

[0037]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. Hereinafter, the measuring method of each physical property value is shown.

[1] Infrared absorption (IR) spectrum The IR spectrum was obtained by a Fourier transform infrared absorption spectrometer (Shimadzu Corporation: FTIR 8000, 8100).
M).

[2] Amount of adsorption and desorption of oxygen and nitrogen The amounts of adsorption and desorption of oxygen and nitrogen were measured using a fully automatic gas adsorption apparatus (BELSORP 28SA, manufactured by Nippon Bell Co., Ltd.). In this fully automatic gas adsorption apparatus, the pressure in the cell was set to 1.0 × 10
A device capable of adjusting the pressure from ^-4 Pa to 101.3 kPa and from 101.3 kPa to 1.0 × 10 ^-4 Pa,
At this time, the amounts of oxygen and nitrogen adsorbed or desorbed can be measured by a volumetric method.

Example 1 1.0 g of biscopearl, a porous cellulose bead
(Manufactured by Rengo Co., Ltd .: 4 mm in diameter) at 1 mol / L
25 ℃ aqueous sodium hydroxide solution adjusted to 50 ℃
(Liquid temperature) for 24 hours. The biscopearl was taken out, washed with about 500 mL of water, and dried for 24 hours with a dryer (DG82 manufactured by Yamato Scientific Co., Ltd.) set at 60 ° C. The dried Biscopearl is fully gas-adsorbed (Nippon Bell Co., Ltd .: BELSORP)
Vacuum (0.01P) using a pretreatment device of
Under a), a heat treatment was performed at 300 ° C. for 10 hours to obtain a black and spherical carbide (0.65 g). As a result of measuring the IR spectrum of the carbide according to the above-mentioned measurement method [1], as shown below, the absorption band (3
500 cm ^-1 ) and the absorption band of OH bending vibration (1400
１２1250 cm ⁻¹ ) was confirmed. IR (KBr) cm ^-1 : 3500, 2850, 154
0,1520-1505, 1400-1250,105
0.

Example 2 Example 1 was the same as Example 1 except that the temperature of the vacuum heat treatment was 250 ° C.
Similarly, Bisco Pearl 1.0g (Rengo Co., Ltd.)
(Diameter: 4 mm) to black and spherical carbide (0.72
g) was obtained. The carbide is measured according to the above measurement method [1].
As a result of measuring the IR spectrum,
Absorption band of O-H stretching vibration (3500cm ^-1) And OH
Absorbing band of bending vibration (1400-1250cm^-1) Confirmed
Was done. IR (KBr) cm^-1: 3500, 2850,
1540, 1520-1505, 1400-1250,
1050.

Example 3 Example 1 was the same as Example 1 except that the temperature of the vacuum heat treatment was 400 ° C.
Similarly, Bisco Pearl 1.0g (Rengo Co., Ltd.)
(Diameter: 4 mm) to black and spherical carbide (0.31
g) was obtained. The carbide is measured according to the above measurement method [1].
As a result of measuring the IR spectrum,
Absorption band of O-H stretching vibration (3500cm ^-1) And OH
Absorbing band of bending vibration (1400-1250cm^-1) Confirmed
Was done. IR (KBr) cm^-1: 3500, 2850, 154
0,1520-1505, 1400-1250,105
0.

Example 4 Polyvinyl alcohol (Kuraray Co., Ltd .: PVA.1)
After dissolving (17), 1.0 g of beads (PVA beads) (2 mm in diameter) prepared by using the nozzle centrifugation method was added to 0.5.
It was immersed in 50 mL of an aqueous potassium hydroxide solution adjusted to mol / L at 25 ° C. (liquid temperature) for 24 hours. After removing the PVA beads and washing them with about 500 mL of water,
A dryer set to 0 ° C (manufactured by Yamato Scientific Co., Ltd .: DG8
It dried for 24 hours in 2). A dried PVA bead is used as a fully automatic gas adsorption device (manufactured by Japan Bell Co., Ltd.
Using a pretreatment device of SORP 28SA), a heat treatment was performed at 250 ° C. for 5 hours under vacuum (0.01 Pa) to obtain black and spherical carbide (0.78 g). The measurement method for the carbide [1] Result of measurement of the IR spectrum in accordance with the absorption band of the O-H stretching vibration as shown in the following (3500 cm ^-1) and the absorption band of the O-H deformation vibration (1400~1250cm ^{- 1} ) was confirmed. IR (KBr) cm ^-1 : 3500, 2850, 154
0, 1520, 1505, 1400 to 1250, 105
0.

Example 5 Bleached softwood kraft pulp (NB manufactured by Oji Paper Co., Ltd .: NB)
1.0 g of (KP) was immersed in 50 mL of an aqueous sodium hydroxide solution adjusted to 2.5 mol / L at 25 ° C. (liquid temperature) for 48 hours. The NBKP was taken out, washed with about 500 mL of water, and then dried for 24 hours with a dryer (DG82, manufactured by Yamato Scientific Co., Ltd.) set at 60 ° C. The dried NBKP was subjected to a heat treatment at 250 ° C. for 16 hours under vacuum (0.01 Pa) using a pretreatment device of a fully automatic gas adsorption device (BELSORP 28SA manufactured by Nippon Bell Co., Ltd.) to give a black Fiber-shaped carbide (0.81
g) was obtained. As a result of measuring an IR spectrum of the carbide according to the above-mentioned measurement method [1], as shown below, an absorption band (3500 cm ⁻¹ ) of OH stretching vibration and OH
An absorption band of bending vibration (1400 to 1250 cm ^-1 ) was confirmed. IR (KBr) cm ^-1 : 3500, 2850, 154
0, 1520, 1505, 1400 to 1250, 105
0.

Comparative Example 1 Biscopearl 1.0 g (manufactured by Rengo Co., Ltd .: 4 m in diameter)
m) was immersed in 50 mL of pure water at 25 ° C. (liquid temperature) for 24 hours. The bisco pearl was taken out and dried with a dryer (DG82, manufactured by Yamato Scientific Co., Ltd.) set at 60 ° C.
Dry for 4 hours. The dried Biscopearl is fully gas-adsorbed (Nippon Bell Co., Ltd .: BELSORP)
Vacuum (0.01P) using a pretreatment device of
Under a), a heat treatment was performed at 300 ° C. for 10 hours to obtain a black and spherical carbide (0.58 g). As a result of measuring the IR spectrum of the carbide according to the above-mentioned measurement method [1], as shown below, the absorption band (3
500 cm ^-1 ) was observed as a trace, but the absorption band of OH bending vibration (1400 to 1250 cm ^-1 ) was not observed. IR (KBr) cm ^-1 : (3500), 1540, 15
20.

Comparative Example 2 In the same manner as in Example 1 except that the temperature of the vacuum heating treatment was changed to 800 ° C., a black and spherical carbide (0.10 g) was obtained from 1.0 g of biscopearl (manufactured by Rengo Co., Ltd .: 4 mm in diameter).
g) was obtained. As a result of measuring the IR spectrum of the carbide according to the above-mentioned measuring method [1], no absorption band of OH stretching vibration and OH bending vibration was confirmed as shown below. IR (KBr) cm ^-1 : 1540, 1520.

Comparative Example 3 The same procedure as in Example 1 was carried out except that the temperature of the vacuum heat treatment was changed to 100 ° C., and an orange and spherical product (0 mm) was obtained from 1.0 g of biscopearl (manufactured by Rengo Co., Ltd .: 4 mm in diameter). .95 g). The results of measuring the IR spectrum of the product according to the above-mentioned measurement method [1] are shown below. Since the obtained IR spectrum did not show any change as compared with the case where the carbonization treatment was not performed, it was considered that the product had not sufficiently advanced carbonization. IR (KBr) cm ^-1 : 3500, 2850, 160
0, 1500 to 1000, 900, 700 to 400.

Comparative Example 4 A layered compound was obtained from montmorillonite and trinuclear iron acetate trinitrate according to JP-A-9-192483. That is, trinuclear iron acetate trinitrate prepared using iron nitrate, ethyl alcohol, and acetic anhydride (all manufactured by Kanto Kagaku Co., Ltd.) was placed between the layers of 1.0 g of montmorillonite (Kunimine Industry Co., Ltd .: Knipia-F). Was introduced so that the ion exchange capacity becomes 5 times. Then, the compound was placed in an electric furnace (Shibata Science Co., Ltd .: SMS-
200) at 400 ° C. for 1 hour to oxidize trinuclear acetate ions to obtain a layered compound (Fe3-montmorillonite: 1.32 g).

Experimental Example 1 The adsorption and desorption characteristics of oxygen and nitrogen at 25 ° C. of each of the samples prepared in the above Examples and Comparative Examples were measured by measuring the adsorption and desorption amounts of oxygen and nitrogen according to the above measuring method [2]. Evaluation was made by creating a desorption isotherm. The results for each example are shown in FIG. FIG. 2 shows the result of each comparative example. In the adsorption / desorption isotherm, the vertical axis indicates the amount of adsorption or desorption of oxygen or nitrogen per 1 g of the sample under the standard condition (25 ° C., 101.3 kPa), and the horizontal axis indicates the pressure.

Experimental Example 2 The samples of Examples 1, 4 and 5 and Comparative Examples 1 and 4 after the completion of Experimental Example 1 were again subjected to vacuum (0.01 Pa).
Heat treatment (regeneration treatment) was performed at 300 ° C. Then, at 25 ° C
The adsorption and desorption characteristics of oxygen and nitrogen were evaluated by measuring the adsorption and desorption amounts of oxygen and nitrogen according to the above measuring method [2] and creating an adsorption and desorption isotherm. The result is shown in FIG.

Experimental Example 3 The samples of Examples 1, 4 and 5 and Comparative Examples 1 and 4 after the completion of Experimental Example 2 were again subjected to vacuum (0.01 Pa).
Heat treatment (regeneration treatment) was performed at 300 ° C. Then, at 25 ° C
Was evaluated by measuring the amount of adsorption and desorption of oxygen and nitrogen according to the measurement method [2] above and creating an adsorption and desorption isotherm. FIG. 4 shows the results.

The above results are summarized in Table 1 below. In the adsorption and desorption isotherms of FIGS. 1 to 4, the larger the value on the vertical axis near normal pressure, the better the adsorption property, and the larger the value on the vertical axis near vacuum, the better the desorption property. You can judge. Also, O in Table 1
₂ / N ₂ is the ratio of the amount of adsorbed nitrogen to the amount of adsorbed oxygen in the standard state (that is, the value obtained by dividing the amount of adsorbed oxygen by the amount of adsorbed nitrogen in the standard state) and represents the selectivity of oxygen.
Accordingly, it can be seen from FIGS. 1 to 4 and Table 1 that each example of the present invention has excellent adsorption characteristics and desorption characteristics, has excellent oxygen selectivity, and is easily regenerated, as compared with the comparative example. We can conclude that we can do it.

[0053]

[Table 1]

[0054]

The hydroxyl group-containing carbide of the present invention has excellent oxygen adsorption capacity and oxygen selectivity, and can be easily regenerated. Therefore, it is composed of a mixed gas, especially oxygen and nitrogen such as air. It can be suitably used as an adsorbent, an oxygen adsorbent, a separator for oxygen and nitrogen in an equilibrium separation type PSA for separating a mixed gas into oxygen and nitrogen, and the like. Further, the hydroxyl group-containing carbide is easy to industrialize because the raw material is inexpensive and the production process is easy.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the ratio of oxygen and nitrogen to
It is a figure which shows the adsorption-desorption isotherm at 5 degreeC (adsorption: solid black, desorption: hollow).

FIG. 2 shows the ratio of oxygen and nitrogen in the samples obtained in each comparative example.
It is a figure which shows the adsorption-desorption isotherm at 5 degreeC (adsorption: solid black, desorption: hollow).

FIG. 3 is a graph showing adsorption and desorption isotherms at 25 ° C. for oxygen and nitrogen of the samples obtained in Examples 1, 4 and 5 and Comparative Examples 1 and 4 after one regeneration treatment (adsorption: Black fill, desorption: hollow).

FIG. 4 is a graph showing adsorption and desorption isotherms at 25 ° C. for oxygen and nitrogen of the samples obtained in Examples 1, 4 and 5 and Comparative Examples 1 and 4 after two regeneration treatments (adsorption: Black fill, desorption: hollow).

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Tomoki Nagata 1-15-15 Fujimi, Kofu City, Yamanashi Prefecture F-term (reference) 4G046 CA04 CB08 CC01 CC05 HA01 HC03 4G066 AA04B AC02A BA36 CA27 CA37 DA03 FA23 FA34

Claims (6)

[Claims] 1. Hydroxyl group-containing carbide derived from a hydrophilic polymer having the following properties: (a) an oxygen adsorption amount in a standard state of 1 to 50 mL / g
(B) The ratio (O ₂ / N ₂ ) between the amount of adsorbed oxygen and the amount of adsorbed nitrogen in the standard state is 2 to 40. 2. The hydroxyl group-containing carbide derived from a hydrophilic polymer according to claim 1, wherein the hydrophilic polymer is cellulose. 3. An oxygen adsorption amount in a standard state of 3 to 40.
The hydroxyl group-containing carbide derived from a hydrophilic polymer according to claim 1 or 2, which is mL / g. 4. The hydroxyl group-containing carbide derived from a hydrophilic polymer according to claim 1, wherein O ₂ / N ₂ in a standard state is 5 to 30. 5. A method comprising: (1) a step of impregnating a hydrophilic polymer with an aqueous solution of a basic substance; and (2) a step of carbonizing the impregnated hydrophilic polymer at 150 to 500 ° C. The method for producing a hydroxyl group-containing carbide derived from a hydrophilic polymer according to any one of claims 1 to 4. 6. An adsorbent comprising the hydroxyl group-containing carbide derived from a hydrophilic polymer according to claim 1.