JPH024446A - Gas adsorbent - Google Patents

Abstract

PURPOSE:To enhance selective adsorption ability to give gas molecules and improve separation and refinement of gas by carrying conductive high molecules having conjugated double bond as effective component on a substrate and preparing a gas adsorbent. CONSTITUTION:A porous substrate is immersed in a monomer solution for forming conductive high molecules (pi conductive high molecules) having conjugated double bond, and then immersed in oxidizer solution, and pi conductive high molecules are precipitated and adhered to the substrate of porous substrate (including pore wall) to prepare a gas adsorbent. The porous substrate is composed of glass, ceramics and various kinds of high colecules, and various shapes of porous materials can be utilized. The materials having micro-pores of approximately 20A-several mu can be utilized. As the pi conductive high molecule, polyacetylene, polyphenylene, polyaniline, polypyrrole, poly-N-methylpyrrole or the like can be used.

Description

Detailed Description of the Invention [Field of Industrial Application] The Ichiki invention relates to a gas adsorbent that utilizes the good gas adsorption ability of a conductive polymer having a military service double bond (a π-based conductive polymer). . The adsorbent can be used to adsorb gases and vapors such as oxygen, carbon dioxide, and ammonia, and
It is particularly useful for separating and purifying components contained in various gases and vapors, or as a deodorizing agent.

[Prior Art] Gas adsorbents made of porous substances such as activated carbon, molecular sieve carbon, zeolite made of hydrated silica, and silica gel are known, and are used for adsorption and removal of various gases. has been done.

[Problems to be solved by the invention] In order to enable the use of gas adsorbents in various fields,
Alternatively, various studies have been made to obtain gas adsorbents with higher performance.

From this point of view, the present inventors have repeatedly conducted various studies on the application of various materials to gas adsorbents. the result,
New findings have been obtained that π-based conductive polymers such as polypyrrole and polythiophene have good gas adsorption ability and preferential affinity for specific gas molecules.
The invention has been completed.

The object of the present invention is to have good gas adsorption ability and to be able to adhere to the surface of a support having any form by electrolytic polymerization or chemical oxidation. The object of the present invention is to provide a gas adsorbent that can be in any form such as a film.

Another object of the present invention is to provide a gas adsorbent that has preferential adsorption ability for specific gas molecules and can be suitably used for gas separation and special operations.

[Means for Solving the Problems] The effective main component of the gas adsorbent of the present invention is a conductive polymer (π-based conductive polymer) having a conjugated double bond in its main chain.

Examples of the π-based conductive polymer used in the present invention include polyacetylene, polyphenylene, polyaniline, polypyrrole, poly-N-methylpyrrole, polythiophene,
Among these, pyrrole and other 5-membered heterocyclic polymers are preferred because they can be easily polymerized by chemical oxidation. Easy to use.

The above-mentioned π-based conductive polymer does not need to be a homopolymer; for example, it may be a copolymer containing two or more types of π-based conductive polymers that can form a π-based conductive polymer, or a π-based conductive polymer. One or more types of monomers that can form
It may also be a copolymer containing one or more of the following: When using these copolymers, the type and blending ratio of the monomers to be used may be determined in consideration of their shapeability, gas adsorption ability, and the like.

Furthermore, the π-based conductive polymer may contain various compounds (including those in an ionic state) as dopants that can be used to adjust its conductivity.

Examples of such compounds include C12,11r2.
halogens such as 12, protic acids such as ll2SO, , 11NO3, eg SO, , AsF, , FeCr1L
Compounds that can act as electron acceptors, such as Lewis acids such as , and compounds that can act as electron donors, such as alkali metals such as Li, Na, etc., can be mentioned.

To obtain a π-based conductive polymer, for example, an electrolytic polymerization method on an electrode or a solution containing a monomer for a π-based conductive polymer is mixed with a solution of an oxidizing agent such as ferric chloride or potassium persulfate. Methods such as a chemical oxidation method that causes a reaction can be used.

The electrical conductivity of the π-based conductive polymer obtained by these methods varies depending on the polymerization conditions, the presence or absence of the above-mentioned dopant, or the amount added, but it is usually 1010 to 10-
It shows a resistance value of about 4Ω·clIl.

The gas adsorbent of the present invention can be obtained using the π-based conductive polymer described above.

The gas adsorbent of the present invention has a preferential adsorption property for specific gas molecules by containing a π-based conductive polymer as an essential component, and can be used to separate and specially prepare specific gas molecules from a mixed gas. It can be suitably used for.

For example, for 02 gas and N2 gas, which have almost the same molecular size, the gas adsorbent of the present invention reversibly adsorbs 02 gas preferentially even in a saturated adsorption state, making it suitable for separation operations between 0□ gas and N2 gas. It can be used.

For reference, PSA (Pressure Swing
In molecular sheep zeolite (MSZ), which is used industrially to separate 02 gas and N2 gas from air using As shown in Kagaku Kogyo 31-6 Supplement "Development and Practical Application of Advanced Separation Technology" published by Kagaku Kogyosha, published in 1985), it has preferential adsorption ability for N2 gas.

It is presumed that the selective adsorption of the specific molecule described above is due to the relationship between the conjugated double bond of the π-based conductive polymer and the adsorbed molecule. In other words, the π possessed by the π-based conductive polymer
It is thought that the above-described priority order in adsorption occurs due to some kind of interaction between the electrons and the electron cloud of the adsorbed molecule.

Therefore, the gas adsorbent of the present invention combines the above-mentioned 02 gas and N2 gas.
As in the case of a combination with a gas, it has the potential to be suitably used for separation between gas molecules that are approximately the same at the molecular size level but have different electron cloud states.

Such combinations of gas molecules to be separated include combinations of alkanes and alkenes with the same number of carbon atoms, such as ethane and ethylene, propane and propylene, combinations of alkenes and alkynes with the same number of carbon atoms, and polar molecules with approximately the same molecular size. Combinations of nonpolar molecules, such as CO2 gas and air (N2.
02) etc.

In addition, even if the molecular sizes are different, if micropores are formed in the adsorbent, the diffusion rate into the micropores will be different, or the sieve effect of molecular sieve carbon will affect the adsorbent. Differences in adsorption capacity appear and separation becomes possible. For example, between 11e gas and N2 gas, the adsorption rate of lie gas is high and effective separation is possible.

In order to obtain a higher adsorption rate of adsorbed gas molecules to the gas adsorbent of the present invention, its specific surface area is 10 m2/g or more, preferably 50 i2/g, more preferably 100 m2/g.
It is good to form this so that it becomes the above.

These gas adsorbents having a specific surface area of tom2/g or more can be obtained using, for example, the following method.

1) Form the gas adsorbent into fine particles of about 1 μm or less.

That is, the above-mentioned π-based conductive polymer is formed into fine particles by various methods and used as a gas adsorbent.

Specifically, when obtaining a π-based conductive polymer by a chemical oxidation method, a π-conductive polymer forming solution and an oxidizing agent solution are mixed into a polymer that forms fine particles of about 1μ or less. By mixing with stirring under the conditions necessary to obtain a molecule, the resulting polymer particle precipitate is collected, washed, and dried.
It is possible to obtain a conductive polymer in the form of small particles.

In addition, in order to make the stirring effect effective, it is also effective to mix the solid solution while irradiating the solid solution with ultrasonic waves. Also,
It is also effective to add a small amount of surfactant to the solution.

2) Porous support surface with large specific surface area (including pore walls)
The above-mentioned π-based conductive polymer is attached to the substrate.

The porous support may be made of glass, ceramics, various polymers, or the like, and may have various shapes such as beads, membranes, fibers, hollow fibers, and tubes.

As a method for attaching a π-based conductive polymer to a porous support, for example, the porous support is immersed in a solution for forming a π-based conductive polymer, and then further immersed in an oxidizing agent solution. , a method can be used in which a π-based conductive polymer is precipitated and attached to the surface of a porous support (including pore walls).

Note that the order of dipping the porous support in the two types of solutions described above may be reversed.

The type and shape of the porous support, the size of the micropores it has, and the polymerization conditions for the π-based conductive polymer are such that a sufficient adhesion state of the π-based conductive polymer can be obtained and the final result can be obtained. The specific surface area of the π-based conductive polymer-adhered porous material is IOn.
It is appropriately selected so that it is +2/g or more.

For example, use a porous support that has micropores of about 20 to several microns, and be careful not to cause π-based conductive polymer precipitation to block the micropores and significantly reduce the specific surface area. The conditions may be selected and used as appropriate.

For example, Corning's Vycor Glass (#79
30) has a pore diameter of 40, a porosity of 28%, and a specific surface area of 274.
The porous glass has a specific surface area of 2:15 (rn'/g) by attaching polypyrrole to the pore surface using a chemical oxidation method under the conditions shown in Example 3.
/g) can be obtained.

Furthermore, when using particulate gas adsorbent by filling it into a container such as a column or tank, depending on the filling condition, the flow resistance of the gas within the container may become too large, causing problems in processing operations. In some cases, if a gas adsorbent is used, which has a gas adsorbent attached to a porous support with a structure that allows for smooth gas flow, it is possible to achieve smooth gas flow, that is, a state of low gas flow resistance. It has the advantage that efficient processing operations can be realized and can be performed at all times.

[Actual h'Fh Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 0.6M virol aqueous solution and 0.6M FeCl1.・
6H20 aqueous solutions were prepared separately, and these were mixed and stirred at room temperature while being irradiated with ultrasound.

When a black precipitate is formed, remove the black precipitate from the mixed solution by 0.00%.
It was filtered and separated using a membrane filter with a pore size of 45 μm, and was thoroughly washed repeatedly with water and ethanol. After washing, the precipitate was dried under reduced pressure at 60° C. for 5 hours to obtain a black powder.

The black powder was confirmed to be polypyrrole powder from its infrared absorption spectrum.

Further, when the black powder was observed with a scanning electron microscope, agglomeration of fine particles of diameter IJLs was observed, and the specific surface area was measured by the BET method and was 19 m2/g.

Next, the adsorption and crosstalk of the black powder with respect to 02 gas and N2 gas at room temperature (approximately 20° C.) was measured according to a conventional method. The results are shown in FIG.

As shown in FIG. 1, the black powder.

It exhibited a saturated adsorption amount of 0.77 mol/kg adsorbent at a gas pressure of 1 atm, and its adsorption characteristics were preferential to 02 gas.

Furthermore, the change over time in the adsorption rate of O2 gas and N2 gas in the black powder was measured according to a conventional method, and the results shown in FIG. 3 were obtained.

When we calculated the adsorption rates for 0□ gas and N2 gas from the results in Figure 3, we found that the time to reach saturated adsorption (adsorption rate 1.0) was 50 minutes for N2 gas and 50 minutes for 0□ gas. It was 150 minutes.

Example 2 Polypyrrole was electrolytically polymerized on an electrode according to a conventional method, and the film-like polypyrrole obtained on the electrode was peeled off, washed, and dried.

Next, the specific surface area, adsorption isotherm for 0□ gas and N2 gas, and adsorption rate of the polypyrrole film were measured in the same manner as in Example 1.

As a result, the specific surface area of the polypyrrole was 3.6 m”/
g, and the adsorption isotherm showed the same results as in FIG.

In addition, the time until saturated adsorption (adsorption rate 1.0) is reached is:
In the case of N2 gas, the time was 100 minutes, and in the case of 02 gas, it was 300 minutes.

Example 3 Tube-shaped (inner diameter 7113, thickness 11 mm) porous glass (Vycor glass $79) as a porous support
30, manufactured by Corning, average pore size 40, porosity 28%
, specific surface M274 ta2/g' measured by BET method
) to obtain a gas adsorbent of the present invention consisting of a porous glass/polypyrrole composite.

First, as an oxidizing agent solution, 0.3M FeC15"6H2
0/acetonitrile solution, 0.3 as a 1000 ml solution
A pyrrole/acetonitrile solution of M was prepared in advance.

Next, the tubular support was placed in acetonitrile in a test tube that could be depressurized, and when the pressure inside the test tube was reduced, the support was irradiated with ultrasonic waves and washed for about 10 minutes.

The washed support was first immersed in an oxidizing agent solution for about 5 minutes at room temperature, and then immersed in a Senzummer solution for about 5 minutes. The same operation was repeated three more times.

After the immersion treatment, the surface and interior of the support were colored black, indicating that polypyrrole had adhered thereto.

The specific surface area, adsorption isotherm and adsorption rate for O2 gas and N2 gas of the porous glass/polypyrrole composite obtained by the above operations were measured in the same manner as in Example 1.

As a result, the specific surface area of the composite was 235 m2/g, and the adsorption isotherm showed the same behavior as in FIG.

The weight of the adsorbent when measuring the adsorption isotherm can be determined by measuring the weight of the porous glass of the support before adhesion, and measuring the weight change after adhesion to determine the amount of polypyrrole adsorbed on the support. It was obtained by calculating.

Furthermore, the time required for the composite to reach saturated adsorption (adsorption rate 1.0) was 5 minutes for N2 gas and 15 minutes for 02 gas.

Example 4 Example 1 using N-methylpyrrole in place of virol
Poly N-methylpyrrol powder was obtained in the same manner as above.

When the powder was observed with a scanning electron microscope, it had a diameter of about 1
Agglomeration of microparticles of μ was observed, and the specific surface area was
The result of measurement using the T method was 860+m2/g.

Next, in the same manner as in Example 1, the saturated adsorption amount of the powder for 02 gas and N2 gas was measured, and it was found that 760III
0.85 mol/kg adsorbent for 02 gas at mHg, N
The amount of adsorbent was 0.36 mol/kg for the two gases.

The time required for the powder to reach saturated adsorption (adsorption rate 1.0) was measured in the same manner as in Example 1, and was found to be within 5 minutes for both N2 gas and 02 gas.

[Effects of the Invention] The gas adsorbent of the present invention has a π-based conductive polymer as an active ingredient, so it has good gas adsorption properties and is suitable for adsorption of various gases (including steam) and deodorization. Available.

In addition, since the adsorbent can be manufactured not only in the form of fine particles such as conventional activated carbon or zeolite, but also in the chemical oxidative polymerization method, the adsorbent of the present invention can be supported on or inside a support having any form. It has a wide range of applications.

Furthermore, π-based conductive polymers have selective adsorption properties for specific gas molecules, and the adsorbent of the present invention can be used to adsorb specific gas molecules, such as separating and purifying them from a mixed gas containing oxygen gas and nitrogen gas. It is useful for the separation and purification of gas molecules.

[Brief explanation of the drawing]

Figure 1 shows the polypyrrole obtained in Example 1 with N2 gas and 0
□Graph showing isothermal adsorption lines for gases, Figure 2 is a graph showing isothermal adsorption lines for molecular sieve zeolite for N2 gas and 02 gas, Figure 3 is a graph showing isothermal adsorption lines for N2 gas and 02 gas in the polypyrrole obtained in Example 1. It is a graph showing the change over time in the adsorption rate of . 'J14 En (kg/cm2abs) Fig. 2 Fig. 1 Infusio adhesion (minutes) Fig. 3 - Hands and arms (kg/cm2abs) May Zz, 1999

Claims (1)

[Scope of Claims] 1) A gas adsorbent characterized by containing a conductive polymer having a conjugated double bond as an active ingredient. 2) The gas adsorbent according to claim 1, which has a specific surface area of 10 m^2/g or more. 3) The gas adsorbent according to claim 1 or 2, wherein the conductive polymer is attached to a surface including pore walls of a multi-hard support.