JPS61107941A - Adsorptive separation agent - Google Patents

Abstract

PURPOSE:To effectively remove N1-gas in methane gas, by containing a Ca-ion in clinoptilite zeolite of which the available adsorbing fine pore size is 3.7Angstrom in such an amount that the mol ratio of CaO/Al2O3 is 0.4-0.75. CONSTITUTION:A Ca-ion containing a cation is introduced into clinoptilite zeolite of which the available adsorbing fine pore size is 3.7Angstrom in such a value that the mol ratio of CaO/Al2O3 is 0.45-0.75 by adapting an ion exchange method. As the source of the Ca-ion, inorg. salts having large solubility such as CaCl2, Ca(NO3)2 or the like are used. As the ion exchange method, a batchwise, column passing type or recirculation method may be employed but it is necessary to set such a condition that the Ca-content enters the aforementioned range in an ion exchange equilibrium state. After the completion of ion exchange, the obtained product is sufficiently washed with water until coexisting anions are not detected.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an adsorption/separation agent used for separating and purifying mixed gases, and in particular for separating a mixture of gas molecules having similar kinetic diameters. The present invention provides a zeolite adsorbent suitable for

(Prior Art) Gas is used in all sorts of places, from households to industries, and the types of gas used are wide-ranging. In particular, with the remarkable development of the industrial world, large quantities of high purity gas or concentrated gas have come to be required.

Accordingly, there is an urgent need to develop a technology for removing minute amounts of impurity gas components from the main component gas, that is, a purification wave WI or concentration technology. Furthermore, even in fields where emphasis is placed on separation, typified by the concentration of oxygen or nitrogen in the air, there is a need for economical systems with as high separation efficiency as possible.

In either case, the performance of the adsorbent plays an extremely important role, so the development of a binding agent suitable for the target yarn is an important key.

In particular, zeolites having a fixed pore size on the molecular order are promising as adsorbents for these, and some have already been put into practical use.

Cryogenic separation methods are well known among common gas separation or purification methods. Although this method has the advantage of producing highly pure gas, it has the disadvantage of requiring a large amount of energy.

On the other hand, many separation methods using zeolite as an adsorption/separation agent have been put into practical use, including the separation of oxygen and nitrogen from the air, the removal of carbon dioxide from the air, and the desulfurization of natural gas.

In most cases, the zeolite used for this purpose has a pore diameter larger than the kinetic diameter of the target gas molecule. For example, C is used to separate oxygen and nitrogen in the air.
aA, X 1 mordenite corresponds to K. The kinetic diameters of oxygen and nitrogen are 144A and Al54A, respectively, and the pore diameters of CaA, X, and mordenite are ~sA, eA
, 7A. Therefore, this separation method utilizes the adsorption capacity or adsorption rate difference of gas molecules to the zeolite, rather than using molecular sieving based on the pore diameter of the zeolite.

Examples of separation methods that have been put into practical use that utilize the molecular sieving action of zeolite include KKA for removing water in ethylene from naphtha cracked gas, and CaA zeolite for separating isoparaffin and n-paraffin. .

In these cases, separation is relatively easy because there is a considerable difference in the dynamic diameters of the gas molecules to be separated and the main component gas molecules.

However, since the effective pore diameter of zeolite is determined by the crystal structure and the cation species contained, it is difficult to produce kuzeolite with an arbitrary effective pore diameter. Therefore,
It is not possible to separate molecules of any size using zeolites.

(Problems to be Solved by the Present Invention) If we define that a zeolite that can separate gas molecules with a dynamic diameter of less than 17A and gas molecules with a dynamic diameter of FA or more has an effective pore diameter of 5-7A, the conventional L7A There was no zeolite with effective pore size.

The dynamic diameter of gas molecules here is [Zeoli
te Mo1ecular 5ieves J (D,
W.

This is the size of the gas molecule based on the numerical value listed on page 636 (by Breck, 1974).

The most common way to change the effective pore size using a specific zeolite is to change the cationic species in the zeolite, but if you just combine the zeolite and the cationic species, the resulting product will not work at room temperature. It is difficult to precisely control the effective pore diameter. When the effective pore diameter is large, one way to reduce the pore diameter is to lower the adsorption temperature.

By lowering the temperature, the thermal vibrations of the zeolite's lattice oxygen and, in particular, the cations can be suppressed, making it possible to make the pore diameter smaller and more precise, thereby bringing it closer to the desired value. As a result, molecules that cannot be separated at room temperature can now be separated at low temperatures.

For example, the above-mentioned [Zeolite Molecular S
As stated on page 639 of ieves J.
Using NaA, it becomes possible to separate nitrogen and oxygen, which cannot be separated by molecular sieving at room temperature, at temperatures below 1100°C.

Using this idea, it can be estimated that the objective zeolite having a pore size of 17A can be realized by using NaA having an effective pore size of 4 at room temperature and lowering the temperature. By the way, as a normal industrial gas adsorption separation method, the method is carried out at room temperature or higher temperature.
It requires less equipment to operate and is the most efficient.

Therefore, from an economical point of view, it is difficult to realize a system in which NaA is cooled to a low temperature and used as an adsorption/separation agent. Existing adsorption/separation agents include the above-mentioned NaA and Ca.
A, X%Y1 mordenite, etc., but none suitable for the purpose of the present invention.

Under these circumstances, the present inventors created a zeolite with an effective pore size of L7A, which is feasible from the viewpoint of industrial and economic rationality, and created a zeolite with a dynamic diameter of A7A7A and a L7A7A gas molecule. As a result of intensive studies to separate the two, the present invention has been achieved.

(Means for Solving the Problems) The method of the present invention involves introducing a certain cation species in a limited proportion into a specific zeolite, which has rarely been used as an industrial adsorption/separation agent in the past. It is possible to adjust the effective pore size of the material. The kinetic diameters of nitrogen molecules and methane molecules are each 164A.
.

18A, it is possible to determine that the zeolite of the present invention has a pore diameter of &7A by measuring the adsorption characteristics of nitrogen and methane.

The zeolite used in the present invention is a clinoptilolite type zeolite. Clinoptilolite occurs naturally, but it can also be synthesized, and its typical composition is the general formula (Nat, K2)0・AI! 03 ・10Si
・Monoclinic thread represented by 8H80 (belongs to zeolite), and its effective pore diameter is said to be 55A.

However, if natural clinoptilolite is packed in a column as it is and a mixed gas of nitrogen and methane is passed through it,
Both nitrogen and methane were adsorbed, and it was impossible to effectively adsorb and separate nitrogen from methane.

The present inventors have conducted intensive studies based on research results regarding the crystal structure, ion exchange characteristics, and adsorption characteristics of zeolite, and have found that by introducing calcium ions into the clinoptilolite structure, nitrogen gas in methane gas can be removed. They discovered that it can be effectively removed and completed the present invention.
゛The present invention will be explained in more detail below.

The zeolite adsorption/separation agent of the present invention is of the clinoptilolite type and is based on olide, and is naturally produced.
Either synthetic product may be used, but it is essential that the amount of calcium (Ca) ions contained as cations is in the range of (L4 to (L75) expressed as a CaO/AI, Os ratio.

A more preferable range is a CaO/AllOs ratio of 145 to
It is in the range of α60. When the CaO/AlxOs ratio is out of this range, the effective pore diameter deviates from L7A to a large extent, resulting in extremely poor separation between molecules of less than A7A and molecules of i7A or more. Furthermore, the effective pore diameter of clinoptilolite, which does not contain any calcium ions, is approximately 4A. The types and amounts of other cations are not particularly limited as long as the amount of calcium ions contained in the clinoptilolite zeolite is within the above range.

An ion exchange method is usually used to introduce calcium ions into clinoptilolite.

As the calcium ion source, inorganic salts with high solubility such as calcium chloride and calcium nitrate are used, and the concentration and amount thereof are selected so that the amount of calcium after exchange falls within the above range.

The ion exchange method may be any method such as a batch method, a column flow method, or a circulation method, but it is necessary to set conditions such that the amount of calcium falls within the above range in an ion exchange equilibrium state. If ion exchange equilibrium has not been reached, it will cause variations in pore diameter, so it is advantageous to raise the temperature of the exchange solution and speed up the time to reach equilibrium as much as possible, and it is preferable to exchange at a temperature of 50°C or higher. .

After ion exchange, thoroughly wash with water or warm water until no coexisting anions are detected.

After washing, dry at a temperature of 100 to 150°C.

Thereafter, it is activated by heating and used as an adsorption/separation agent.

(Function) Although the correct theory regarding the fact that calcium ions are the only cations effective for this purpose is not yet clear, the mechanism can be inferred by considering the structure of clinoptilolite. The pore structure of clinoptilolite consists of a 10-membered oxygen ring and two 8-membered oxygen rings. Considering its size, methane has difficulty passing through the 8-membered oxygen ring, and only passes through the 10-membered oxygen ring. It seems that it will pass.

On the other hand, nitrogen passes through both the 10- and 8-membered oxygen rings. Calcium ions that have entered the zeolite crystal are preferentially incorporated into the 10-membered oxygen ring, increasing the effective pore size to L.
7A, which seems to make it impossible for methane to pass through.

The effective pore diameter of the adsorbent obtained by the method of the present invention is
This can be determined from the adsorption characteristics of each gas under constant temperature and pressure.

The methods for measuring the adsorption characteristics of methane and nitrogen are described in detail below, but there are two methods: measuring the static adsorption capacity of each gas under certain conditions, and a method of measuring the methane and nitrogen mixed gas using the zeolite adsorbent of the present invention. This is a method of measuring dynamic adsorption characteristics in which the composition of the outlet gas is analyzed by flowing it through a packed column.
- That is, in the static adsorption capacity measurement method, the smaller the amount of methane adsorbed while adsorbing nitrogen, the effective adsorption pore diameter of the zeolite is closer to &7AK, and the root pore diameter where the amount of methane adsorbed is larger than 57A. Furthermore, in the dynamic adsorption characteristic measuring method, evaluation can be made based on the separability of methane and nitrogen, and it can be said that the better the separability is, the closer the effective adsorption pore diameter of the adsorbent is to F-A.

(Effect of the invention) The zeolite adsorbent with an effective pore size of 57 people produced by the method of the present invention has molecules with a kinetic diameter of L7A7&
The molecules of 7A7& can be separated. As an example, nitrogen gas, which is a trace component in methane gas, can be efficiently adsorbed and removed, and this can be confirmed by the method described above. An example of the application of this characteristic is that nitrogen in COG gas or coal mine exhaust gas can be efficiently removed and methane gas can be used effectively. Further, the present invention is not limited to this example, and there are many other possible methods, such as removing hydrogen sulfide from methane gas or removing argon from xenon.

In this way, it can be applied to the separation, purification, and concentration of active components in mixed gases, which have been difficult in the past.

(Examples) The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Further, the static or dynamic adsorption capacity method measured in the examples is as follows.

Static adsorption capacity measurement method: Sample 11 was heated to 350°C using a constant volume adsorption capacity measurement device.
After vacuum activation treatment for 2 hours, methane (t or nitrogen) gas was introduced into the apparatus after cooling to 30°C, and y 6
Adsorption capacity (N
cc/I) was measured.

Dynamic adsorption characteristics measurement method: Adsorbent-like 5O was placed in a stainless steel packed column with an inner diameter of 2.8C11
After filling with AP, vacuum activation was performed at 350°C for 2 hours, and then helium gas was filled and cooled to 20°C. Then add 50 Ncc of mixed gas of 85% methane and 15% nitrogen.
The composition of the outlet gas was analyzed using a gas chromatograph, and nitrogen gas was detected in the outlet gas after the helium gas in the packed tower was replaced and the outlet methane gas concentration became equal to the inlet methane gas concentration. The separability of methane and nitrogen was evaluated by calculating the effective gas processing amount (Nl/1g).

Example 1 SiQ, 7 L 4 wt%, A1.0.12.1
wt%, 1'J3. Q L O5wt%, MgO[L
71 wt%, K, 0 & 88 wt%, CaOt4
1 kg of natural clinoptilolite containing 2 wt% as a component was added to 1 aa of water with calcium chloride (content 7454
wt%) in an aqueous solution containing ta5kIP, and
Ion exchange was performed at 0° C. for 3 hours with stirring. It was then washed until no chloride ions were detected and dried at 110°C to form the following composition: 5iO17s a wt%, A1.0.12.7 wt
%, NatOL56Wi%, Mg01155 wt%,
K205 25 wt% (: aQ 594 wt%) was obtained. The Cab/A1tOi molar ratio was [L56. Of these, 5ooII was determined according to the dynamic adsorption property measurement method.
As a result of dynamic testing, the effective gas throughput was z 4 N1
It weighed 7 kg.

Furthermore, when the amount of methane and nitrogen adsorbed on this sample was measured according to the static adsorption capacity measurement method, it was found that methane was 4.2 N.
cc/I-Nitrogen 1t1Ncc/II.

Example 2 Calcium-exchanged clinoptilolite 5o obtained in Example 1
aII, calcium chloride (content 7434
(wt%) 925JI was placed in an aqueous solution, and ion exchange was performed under the same conditions as in Example 1 to obtain 5iO17a.
3wt%, AI, 0°1t6wt%, Na, Ot
o s wt%, MgO[L 40wt%, K, Ol
A product with a chemical composition of 74 wt% and C2Q t 81 wt% was obtained. The Cab/AlzOs molar ratio was (L69).As a result of subjecting 300I of this to a dynamic test according to the dynamic adsorption property measurement method, the effective gas throughput was &I
It was 17 kg of N. The amount of methane and nitrogen adsorbed on this sample was measured using the static adsorption capacity measurement method.
Methane 2-7Ncc/Is Nitrogen a y Ncc/I h
It was.

Comparative Example 1 5 oap of clinoptilolite of CaO/Al, 0° molar ratio = α24, used as raw material in Example 1 was taken and subjected to a dynamic test according to the dynamic adsorption characteristic measurement method. As a result, the effective gas throughput was was 9 in λBNl/.

Comparative example 2 CaO/Al, O used as raw materials in Example 1.

10 liters of clinoptilolite with a molar ratio of α24, 1 liter of water
It was placed in an aqueous solution in which aatHc sodium chloride 61 was dissolved, and ion exchange was performed at 80° C. with stirring for S hours, followed by washing until no chlorine ions were detected. This operation was repeated twice in succession. It was then dried at 110°C to form the following composition SiQ, 648 wt%, A11031t o
wt%, Nan.

S, 63 wt%, MgOα18 wt%, K, 0 (
A product with L 65 wt%, C; IQ a 19 wt% was obtained. The Cab/Altos molar ratio was [105]. When the amount of adsorption of methane and nitrogen was measured according to the static adsorption capacity measurement method, methane 1S, s Ncc/
I, nitrogen was 9.4 Ncc/I.

Patent Applicant Toyo Soda Kogyo Co., Ltd. Procedural Amendment Tan December 3, 1985 Commissioner of the Patent Office Michibu Uga 1. Indication of small matter Showa J. 9” “Patent Application No. 209ε343 2. Name of Komei Separating Agent 3 Person who stops RDI Toyo 'AI') + 'lL Toka Co., Ltd. Patent Information Department Telephone? S-Yumi (505)! 1471 11th Amendment 6th Order G] Subject to spontaneous 5th amendment
, 4.6 Contents of amendment (1) The claims are amended as shown in the attached sheet.

(2) The next line after line 7 on page 10 of the specification has been changed. It may be in the form of powder, crushed, or mixed with a binder, granulated, or fired, and its performance will not change. ” to join.

(3) Change the next line after line 15 on page 15 [Example 3 The natural clinoptilolite used in Example 1 was ground to 200 mesh or less, and this powder was made into a slurry 0 degrees 15 w.
t% in a 2 wt% calcium chloride aqueous solution and stirred at 60"C for 3 hours. Next, it was washed until no chlorine ions were detected, dried at 110°C, and the following composition: Sin , ?5.2wt%, A40.1
2.5 wt Chi, Na, 0 2.97 wt Chi, M
gQ(L 50 wt Chi, xto 554 wt arrogant.

Ca0442wt% and CaO/A40s molar ratio -1
50 mL of dry powder was obtained.

10 parts of a binder and water were added to 100 parts by weight of this powder, thoroughly kneaded, and molded into a spherical shape with a diameter of 1.5 to AOn. After drying this molded body at 105°C, it was fired at 550°C for 2 hours.

Of this, 500 g was subjected to a dynamic test according to the dynamic adsorption characteristic measurement method, and as a result, the effective gas throughput was 9 in a 4 Nt/. Furthermore, when this sample was subjected to a static adsorption capacity measurement method and the adsorption amount of methane and nitrogen was measured, it was found that methane was λONcc/g and nitrogen was 11.0 Mac/9.

” to join.

2 Claims (1) An adsorption/separation agent made of clinoptilolite type zeolite, in which the amount of calcium ions contained as cations is in the cao/Al,o molar ratio of a4 to a,75.

Claims (1)

[Claims] (1) Adsorption separation made of clinoptilolite type zeolite in which the amount of calcium ions contained as cations is 0.4 to 0.75 in CaO/Al_2O_3 molar ratio and the effective adsorption pore diameter is 3.7A. agent.