Zeolite encapsulating material

A zeolite occluding material composed of an A-type zeolite expressed by a generic formula (Kx My Naz)(AlO.sub.2.SiO.sub.2).sub.12.(NaAlO.sub.2).delta...omega.H.sub.2 O wherein M represents a bivalent metal; O.ltoreq..delta..ltoreq.1; and .omega. represents a positive number. Further, in the above stated unit cell, x, y and z which respectively represent the numbers of K, M and Na within the unit crystal lattice (or unit crystal cell) are in a relation: EQU x+2y+z=12 EQU 3.ltoreq.x<10 EQU 1<y.ltoreq.4.5.

BACKGROUND OF THE INVENTION 
This invention relates to an improved zeolite occluding material. 
Zeolite is one of adsorbents that are at present widely in use for various 
purposes including industrial purposes. The zeolite, particularly A type 
zeolite, is typically represented by a sodium-A zeolite, which is 
expressed by a typical unit cell of Na.sub.12 
(AlO.sub.2.SiO.sub.2).sub.12. (NaAlO.sub.2).delta...omega.H.sub.2 O, 
wherein 0.ltoreq..delta..ltoreq.1 and .omega. represents a positive 
number. In this unit cell, 12 sodium ions are ion exchangeable for other 
metal ions. The kinds of the exchange ions and the rate of exchange is 
determined by the effective adsorption pore diameter. However, the size of 
the effective adsorption pore diameter is in close relation to the crystal 
structure, the size of the ion species to be exchanged and the position 
selecting property thereof within a unit crystal lattice. In other words, 
among the 12 cations (sodium ions) which are exchangeable within the unit 
crystal lattice of zeolite, three ions are located on the face of an 
eight-member oxygen ring where the molecule to be adsorbed comes in and 
goes out and eight ions are on the face of a six-member oxygen ring while 
the remaining one is located on the face of a four-member oxygen ring. 
Therefore, it is the size of the cations on the face of the eight-member 
oxygen ring that have an influence directly on the adsorbing property of 
the zeolite. Where a sodium A-type zeolite is employed as starting matter 
and the sodium ions of the zeolite are exchanged for potassium ions, the 
potassium ions have a preference for entering the positions on the face of 
the eight-member oxygen ring. The effective adsorption pore diameter of 
the sodium A-type zeolite is 4 .ANG.. When the potassium ions which are 
larger than sodium ions enter the positions, the effective adsorption pore 
diameter of the ion-exchanged zeolite becomes 3 .ANG.. 
If the ion exchange is carried out for calcium ions, calcium ions have a 
preference for entering the positions on the face of the six-member oxygen 
ring while, among the sodium ions that are to move out to keep the balance 
of charges, the sodium ions on the face of the eight-member oxygen ring 
have priority over other sodium ions in moving out. Therefore, when an 
ion-exchange process is carried out until all of the sodium ions disappear 
from the face of the eight-member oxygen ring, the effective adsorption 
pore diameter of the zeolite used in the ion-exchange increases and 
becomes 5 .ANG.. 
Generally, the effective adsorption pore diameter of zeolite or that of 
zeolite obtained through ion-exchange is nearly uniform. A molecule 
smaller than the effective adsorption pore diameter of the zeolite can be 
adsorbed by the zeolite. However, a molecule larger than that cannot be 
adsorbed by the zeolite through a normal process. 
The position selecting property of the ion to be exchanged with the 
exchangeable ion contained in the zeolite and variation that takes place 
in adsorbing property with variation in combination of the species of ions 
have not been clearly known. The present inventors conducted researches 
into the details of these relations. As a result of these researches, it 
has been discovered that a zeolite having a novel adsorbing property which 
has hitherto been unknown can be obtained through an ion exchange process 
for reformation of zeolite in terms of the adsorbing power thereof carried 
out with the combination of ion species and the rate of exchange suitably 
selected. In other words, it has been discovered that, in having the 
exchangeable sodium ions of a sodium type zeolite gradually exchanged for 
calcium ions, when two or more than two calcium ions enter, sodium ions on 
the face of the eight-member oxygen ring move out and this makes the 
effective adsorbing pore diameter 5 .ANG.. 
On the other hand, in case where the potassium ions of a potassium type 
zeolite, which is obtained by exchanging the exchangeable sodium ions of a 
sodium type zeolite with potassium ions, or those of a potassium type 
zeolite obtained with a source of potassium used as material, are 
processed to have them gradually exchanged for bivalent metal ions, the 
bivalent metal ions have preference to come onto a six-member oxygen ring 
face. However, when the number of the bivalent metal ions is less than 4.5 
per unit crystal lattice, the potassium ions on the face of the 
eight-member oxygen ring are not removed from there and thus the effective 
adsorbing pore diameter is kept at 3 .ANG.. 
It has been found that, in the case of zeolite in which the effective 
adsorbing pore diameter is 3 .ANG. with potassium ions on the face of the 
eight-member oxygen ring and bivalent metal ions on a part of the 
six-member oxygen ring face as stated in the foregoing, a molecule of 
diameter larger than the effective adsorbing pore diameter can be adsorbed 
to the zeolite at a relatively low temperature and at a low pressure; and 
that the adsorbed molecule will not be desorbed even when the zeolite is 
brought back into ordinary desorbing condition. Namely, the zeolite has an 
occluding property. This indicates that the potassium ions on the face of 
the eight-member oxygen ring are made to be readily movable by the 
influence of the bivalent ions received in exchange. Such a movable state 
of the potassium ions on the face of the eight-member oxygen ring is 
believed to be dependent upon the number of the exchanged bivalent metal 
ions on the face of the six-member oxygen ring as well as temperature. 
Therefore, the molecule which is occluded in the zeolite can be released 
from an occluded state by raising the temperature of the zeolite. It is 
also possible that the occluding quantity and adsorbing and desorbing 
temperature can be adjusted by varying the number of the bivalent metal 
ions to be exchanged. In a practical application, the exchangeable cations 
of the zeolite do not have to be limited to potassium and bivalent metal 
ions but it is also permissible to have sodium ions on a part of the face 
of the six-member oxygen ring. 
SUMMARY OF THE INVENTION 
It is a general object of the invention to provide the above stated zeolite 
occluding material which is manufactured in the following manner: The 
sodium type zeolite which is to be used for ion-exchange is obtained by an 
ordinary known method, for example, by a hydrothermal crystallizing 
process with sources of silica, alumina and sodium employed. Further, the 
ion-exchange between the sodium ions of the sodium type zeolite and the 
potassium ions is carried out in accordance with an ordinary known method 
by immersing the sodium type zeolite in a solution containing the 
potassium ions. The ratio of the ion-exchange between the sodium ions and 
the potassium ions is approximately set by allowing at least three 
potassium ions to be present per unit lattice of the zeolite. It is also 
possible to use a potassium type zeolite which is obtained by using a 
source of potassium from the beginning without having recourse to 
ion-exchange. The potassium type zeolite thus obtained is subjected to 
ion-exchange for bivalent metal ions. The divalent metal ions usable in 
accordance with the present invention are selected out of a group 
consisting of the bivalent ions of metals belonging to the second group 
shown in the periodic table such as magnesium, calcium, strontium, zinc, 
cadmium and mercury; and the bivalent ions of transition metals such as 
manganese, cobalt and iron. The ion-exchange between the potassium type 
zeolite and the above stated bivalent metal ions is carried out in an 
ordinary known method by immersing the potassium-A zeolite in a solution 
containing these bivalent metal ions. The composition of a zeolite which 
is obtained by having most of the sodium contained in a sodium-A zeolite 
ion-exchanged for potassium to change it into a potassium-A zeolite and by 
having this potassium-A zeolite further ion-exchanged for the divalent 
metal ions with sodium-A zeolite is as shown below: 
EQU (KxMyNaz)(AlO.sub.2.SiO.sub.2).sub.12.(NaAlO.sub.2).delta...omega.H.sub.2 O 
wherein M represents the bivalent metal; 0.ltoreq..delta..ltoreq.1; and 
.omega. represents a positive number. In the present invention, the y 
which represents in the above formula the number of the bivalent metal 
ions contained per the unit crystal lattice of the zeolite is a factor 
which governs the properties of the zeolite as an occluding material. In 
accordance with the invention, x, y and z shown in the above formulas are 
in the following relation: 
EQU x+2y+z=12, 3.ltoreq.x&lt;10, 1&lt;y.ltoreq.4.5. 
The invention is not limited to the method of effecting ion-exchange for 
the bivalent metal ions after the exchangeable cation contained in the 
sodium type zeolite is exchanged for the potassium ion. In addition to 
this method, it is also possible either to carry out the two processes of 
ion-exchange simultaneously by using a solution containing the potassium 
ions and the bivalent metal ions or to carry out the ion-exchange for the 
potassium ions after carrying out the exchange for the bivalent metal 
ions. For the ion-exchange, an aqueous solution of a metal halide 
(particularly chloride), nitrate, sulfate and hydroxide is employed and 
the concentration thereof is suitably determined according to the quantity 
of the zeolite to be used for the exchange, the purpose, the rate of 
exchange, etc. 
To ensure the uniformity and reproducibility of properties of the zeolite 
occluding material obtained in accordance with the invention, it is 
preferable that ion-exchange equilibrium is thoroughly reached in 
effecting the ion-exchange. Although the ion-exchange can be effected at a 
normal temperature, the exchange process is preferably carried out at a 
temperature around 80.degree. C. for a period of at least 0.5 hour. The 
zeolite which has undergone the process of ion-exchange for the bivalent 
metal ions is dried by an ordinary known method to make it into a product. 
The invention is applicable to a wide range of purposes. For example, when 
the invented zeolite is allowed to have a gas occluded therein under a 
relatively low pressure, the gas will not be desorbed even when the 
pressure is brought back to a normal level. Therefore, the gas can be 
filled at low pressure obviating the necessity of the use of a pressure 
resistive container, so that the weight of the container can be reduced to 
facilitate storage and transportation of gas. Particularly, a gas such as 
radioactive krypton (molecular dia. 4 .ANG.) not only can be handled 
without difficulty but also the weight thereof can be reduced to a great 
extent. Further, with the invented zeolite employed, argon the molecule 
diameter of which is 3.8 .ANG. can be occluded in the same manner as 
krypton, so that the zeolite is usable also as argon occluding material. 
Further, since oxygen the molecule dia. of which is 2.8 .ANG. cannot be 
occluded, argon can be separated from an argon-oxygen mixture gas and can 
be solely occluded in the zeolite. 
Since the occluding material of this invention is capable of occluding not 
only hydrogen gas but also other gases such as helium gas and acetylene 
gas, it is usable also for storing them. 
The above and further objects, features and advantages of the invention 
will become apparent from the following detailed description of embodiment 
examples thereof taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
EXAMPLE 1 
First, 128 g of a sodium A-type zeolite which adsorbed a saturated amount 
of water was put in 1 liter of aqueous solution of one normal potassium 
chloride. They were brought into contact with each other at 80.degree. C. 
with stirring over a period of 20 hours. Then solid-liquid separation was 
carried out by filtration. A solid component thus obtained was washed with 
distilled water. This process was repeated twice. An A-type zeolite which 
was thus obtained is again put in 2.5 liters of one normal aqueous 
solution of potassium chloride to bring them into contact at 80.degree. C. 
with stirring over a period of 20 hours. Solid-liquid separation was 
effected by filtration. A solid component thus separated was washed with 
distilled water. This process was repeated five times. An A-type zeolite 
thus obtained was subjected to a chemical analysis to obtain the following 
results: 
EQU K.sub.2 O: 22.4 wt% Na.sub.2 O&lt;0.1 wt% 
A saturating amount of water content was allowed to be adsorbed by the 
potassium A-type zeolite thus obtained. Then, 12.3 g of the zeolite was 
put in an Erlenmeyer flask as sample and an aqueous solution of 0.2 normal 
calcium chloride was also put into the flask for each sample in amount as 
shown in Table 1. They were brought into contact with each other with 
stirring over a period of 20 hours at 80.degree. C. Solid-liquid 
separation was effected by filtration and a solid component thus obtained 
was washed with distilled water to obtain an A-type zeolite. The zeolite 
thus obtained was subjected to chemical analysis to find that the zeolite 
was as shown in Table 1 below: 
TABLE 1 
______________________________________ 
Amount of added 
aqueous solution of 
Sample No. 
potassium chloride, ml 
Composition 
______________________________________ 
1 79 K.sub.8.76 Ca.sub.1.62 A 
2 106 K.sub.7.84 Ca.sub.2.08 A 
3 132 K.sub.6.76 Ca.sub.2.62 A 
4 179 K.sub.5.08 Ca.sub.3.46 A 
5 222 K.sub.4.44 Ca.sub.3.78 A 
______________________________________ 
Each composition shown in Table 1 indicates ratio within the unit cell in 
respect only to the potassium and calcium contained in the zeolite. 
Further, in each composition indicated, A represents other framework of 
zeolite that remained unchanged through ion-exchange. The results of 
chemical analysis were examined in the same manner as this for subsequent 
embodiment examples. FIG. 1 is an X-ray (Cu-K.alpha.) diffraction graph of 
Sample 3 obtained after it was dried and then allowed to adsorb water 
content in saturating amount. 
EXAMPLE 2 
The sample 3 obtained in Example 1 was put in an autoclave of capacity 300 
cc. While the inside of the autoclave was being kept in a vacuum state 
with a vacuum pump, the sample was heated and kept at 300.degree. C. for a 
period of two hours. Then the sample was cooled down to room temperature. 
Following this, krypton gas of purity 99.95% was introduced into the 
autoclave and the autoclave was again heated. The pressure when 
temperature was raised by heating up to 300.degree. C. was 38 kg/cm.sup.2 
G. Then, the autoclave was left intact for one hour and after the heating 
was stopped to effect gradual cooling. The period of time required for the 
gradual cooling from 300.degree. C. down to room temperature was 3 hours. 
The pressure at the room temperature was 23 kg/cm.sup.2 G. The krypton gas 
corresponding to additional pressure was recovered until the pressure 
comes down to about 0.5 kg/cm.sup.2 G and the rest thereof was discharged 
until there obtained atmospheric pressure. 
After that, again the autoclave was heated. The gas which was swollen by 
this heating was collected into a measuring cylinder placed upside-down in 
a water sealed vessel and the gas volume was measured. Further, without 
putting any sample, krypton gas of 99.95 purity was alone introduced into 
the same autoclave up to atmospheric pressure. The autoclave was then 
heated under the same conditions. The swollen gas which was thus obtained 
was collected also by the same substitution method and the amount of the 
gas was measured. The amount obtained by subtracting the gas amount 
collected with the autoclave in the empty state from the gas amount 
collected with the sample within the autoclave was amount deencapsulated 
from the sample. The amount of the deencapsulated gas produced per unit 
weight of the sample in an activated state at each of various degrees of 
temperature was obtained as shown below with the volume of the sample, 
measuring temperature and pressure corrected as necessary: 
TABLE 2 
______________________________________ 
Deencapsulated gas 
Temperature, .degree.C. 
amount (mlSTP/g) 
______________________________________ 
30 0 
50 16.5 
100 33.5 
200 37.5 
300 40.8 
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EXAMPLE 3 
Using the samples 1, 2, 4 and 5 obtained in Example 1, the gas amount 
deencapsulated from them was obtained in the same manner as in Example 2 
to obtain the following results: 
TABLE 3 
______________________________________ 
Deencapsulated gas amount, mlSTP/g 
Temp., .degree.C. 
Sample 1 Sample 2 Sample 4 
Sample 5 
______________________________________ 
30 0 0 0 0 
50 1.9 2.7 16.1 14.7 
100 4.4 25.4 30.1 26.5 
200 13.7 27.6 33.1 27.2 
300 19.1 28.4 36.8 27.6 
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COMISON EXAMPLE 1 
A sodium-A zeolite was allowed to adsorb water content in saturating amount 
and 20 g of the zeolite was put in a Erlenmeyer flask. Then, 130 ml of an 
aqueous solution of 1 normal potassium chloride was put in the flask. They 
were brought into contact with each other with stirring at 80.degree. C. 
over a period of 20 hours. Solid-liquid separation was effected by 
filtration. A solid component thus separated was washed with distilled 
water to obtain an A-type zeolite. The A-type zeolite was subjected to 
chemical analysis to find that the product thus obtained was of 
composition expressed by K.sub.5.81 Na.sub.6.19 A. The amount of gas 
deencapsulated from samples of this zeolite was obtained by the same 
method as in Example 2. The results of this were as shown in Table 4 
below: 
TABLE 4 
______________________________________ 
Deencapsulated gas amount, 
Temperature, .degree.C. 
mlSTP/g 
______________________________________ 
30 0 
50 3.1 
100 4.3 
200 8.3 
300 9.6 
______________________________________ 
EXAMPLE 4 
The sample 4 obtained in Example 1 was put in an autoclave of capacity 300 
cc. While the inside of the autoclave was being kept in a vacuum state 
with a vacuum pump, the sample was heated and kept at 300.degree. C. for a 
period of two hours. Then the sample was cooled down to room temperature. 
Following this, krypton gas of purity 16.95% was introduced into the 
autoclave and the autoclave was again heated. The pressure was 38 
kg/cm.sup.2 G when temperature was raised by heating up to 300.degree. C. 
The autoclave was left intact for one hour and then the heating was 
stopped and followed by a prompt cooling process. The period of time 
required for cooling from 300.degree. C. down to room temperature was 20 
minutes. The pressure at room temperature was 23 kg/cm.sup.2 G. The 
krypton gas corresponding to added pressure was recovered until pressure 
because about 0.5 kg/cm.sup.2 G and the rest thereof was discharged until 
there obtained atmospheric pressure. After that, again the autoclave was 
heated. Then, the gas which was swollen by this heating was collected into 
a measuring cylinder placed upside-down in a water-sealed vessel and the 
gas volume was measured. The amount of the deemcapsulated gas prouced per 
unit weight of the sample while it is in an activated state at each of 
various degrees of temperature was obtained as shown in Table 5 below with 
the volume of the sample, measuring temperature and pressure corrected as 
necessary: 
TABLE 5 
______________________________________ 
Temp., .degree.C. 
Deencapsulated gas amount, mlSTP/g 
______________________________________ 
30 0 
50 26.8 
100 32.5 
200 33.5 
300 33.8 
______________________________________ 
EXAMPLE 5 
The potassium zeolite which was obtained in Example 1 was allowed to adsorb 
water content in saturating amount and 12.3 g of the zeolite was put in an 
Erlenmeyer flask for use as sample. To each sample thus prepared was added 
0.2 normal zinc chloride, 0.2 normal cobalt chloride or 0.2 normal 
manganese chloride, each of these additives being added in amount 158 ml. 
To bring then into contact with each other, stirring was carried out at 
80.degree. C. over a period of 20 hours. Solid-liquid separation was 
effected by filtration and a solid component thus separated was washed 
with distilled water to obtain an A-type zeolite. The zeolite samples thus 
obtained were subjected to chemical analysis to find that the zeolite 
samples were of compositions as shown in Table 6 below: 
TABLE 6 
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Sample No. Composition 
______________________________________ 
6 K.sub.5.58 Zn.sub.3.21 A 
7 K.sub.7.08 Co.sub.2.46 A 
8 K.sub.6.52 Mn.sub.2.74 A 
______________________________________ 
The amount of gas deencapsulated from each of the samples 6, 7 and 8 was 
obtained in the same manner as in Example 2. The results were as shown in 
Table 7 below: 
TABLE 7 
______________________________________ 
Deencapsulated gas amount, mlSTP/g 
Temperature, .degree.C. 
Sample 6 Sample 7 Sample 8 
______________________________________ 
30 0 0 0 
50 15.3 6.3 17.6 
100 16.2 23.7 18.3 
200 16.8 25.1 19.3 
300 17.6 25.6 19.6 
______________________________________ 
EXAMPLE 6 
The sample 3 obtained in Example 1 was put in an autoclave of capacity 300 
cc. While the inside of the autoclave was kept in a vacuum state with a 
vacuum pump, the autoclave was heated and kept at 300.degree. C. for a 
period of 2 hours. Then, the autoclave was cooled down to room 
temperature. After that, krypton gas of 99.95% purity was introduced into 
the autoclave and again the autoclave was heated. The pressure was 18 
kg/cm.sup.2 G when the autoclave was heated up to 300.degree. C. The 
autoclave was left intact in this state for a period of one hour. Heating 
was stopped and the autoclave was gradually cooled. The period of time 
required for cooling from 300.degree. C. down to room temperature was 3 
hours. The pressure at room temperature was 10 kg/cm.sup.2 G. The krypton 
gas corresponding to added pressure was recovered until pressure became 
about 0.5 kg/cm.sup.2 G and the rest was discharged until there obtains 
atmospheric pressure. Following that, the autoclave was again heated and 
gas swollen by this heating was collected into a measuring cylinder placed 
upside-down in a water-sealed vessel and the volume of the gas was 
measured. Then, the amount of gas desorbed from the zeolite was obtained 
by the same method as in Example 2 to obtain results of this as shown in 
Table 8 below: 
TABLE 8 
______________________________________ 
Deencapsulated gas amount 
Temp., .degree.C. 
mlSTP/g 
______________________________________ 
30 0 
50 5.9 
100 14.4 
200 15.4 
300 15.6 
______________________________________ 
EXAMPLE 7 
The sample 3 obtained in Example 1 was put in an autoclave of capacity 300 
cc. While the inside of the autoclave was being kept in a vacuum state 
with a vacuum pump, the autoclave was heated and kept at 300.degree. C. 
for a period of 2 hours. Then, the autoclave was cooled down to room 
temperature. After that, krypton gas of 99.95% purity was introduced into 
the autoclave and again the autoclave was heated. The pressure was 38 
kg/cm.sup.2 G when the autoclave was heated up to 150.degree. C. The 
autoclave was left in this state for a period of one hour. Heating was 
then stopped and the autoclave was gradually cooled. The length of time 
required for cooling the autoclave from 300.degree. C. down to room 
temperature was 3 hours. Pressure at room temperature was 27 kg/cm.sup.2 
G. The krypton gas corresponding to added pressure was recovered until 
pressure became about 0.5 kg/cm.sup.2 G and the rest of the gas was 
discharged until there obtains atmospheric pressure. Following this, the 
autoclave was again heated and the gas swollen by the heating was 
collected into a measuring cylinder placed upside-down in a water-sealed 
vessel. The volume of gas was measured. Then, the amount of gas desorbed 
from the zeolite was obtained by the same method as in Example 2 to obtain 
results of this as shown in Table 9 below: 
TABLE 9 
______________________________________ 
Temp., .degree.C. 
Deencapsulated gas amount, mlSTP/g 
______________________________________ 
30 0 
50 3.9 
100 24.2 
200 26.4 
300 27.1 
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