JPH0675672B2 - Oxygen selective adsorbent - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oxygen-selective adsorbent for separating, removing or concentrating oxygen in air.

(Prior Art) When separating, removing or concentrating oxygen from air, it is necessary to take into consideration that there is usually no raw material cost because the raw material is air, and the price to be added to oxygen is (a) ) Equipment costs for separation and concentration, (b) Power costs necessary to operate the equipment, and (c) If a separation medium is required, it depends on the price and replenishment cost.

Also, as long as the raw material is air, the separation and concentration process
Either of the two methods of separating oxygen and nitrogen may be used.

From these points, it is economically advantageous that deep cooling, which is a typical one of the conventional oxygen and nitrogen separation processes, cools air to an extremely low temperature and separates it by the difference in boiling points of oxygen and nitrogen. A separation device may be mentioned. This device
Suitable for large capacity oxygen production, most domestic oxygen and nitrogen production depends on the cryogenic separation process, but large power,
It has the drawback of requiring large equipment.

In addition, there is a method that uses a zeolite adsorbent by a method that has been recently developed and put into practical use by Union Carbide Co., Ltd. Of these, Morequiller Sheeps 5A, 13X
(Union Carbide Corporation, trade name) what are called is extremely large adsorption capacity for nitrogen (1.2g N ₂ / 100g a
tNTP), and a process for separating and concentrating oxygen by selectively removing nitrogen from the air by these has been put to practical use. Actually, the adsorption capacity of 5A, 13X type molecular sieves is that when the pressure reaches 1.5ata according to the Langmuir type adsorption isotherm, the adsorption capacity does not increase so much as the pressure increases. Also, the N ₂ / O ₂ molar ratio in air is 4
Therefore, it is necessary to remove an extremely large amount of nitrogen. Therefore, the scale merit due to the increase in the capacity of the device is small, and in reality, it is limited to small capacity equipment.

In addition, use of a transition metal-based organic complex that selectively absorbs oxygen can be considered. For example, a cyclic cobalt complex called salcomine absorbs 1 mole of oxygen with 2 moles of salcomine. Since this absorption is reversible with respect to changes in temperature and pressure, separation and concentration of oxygen can be achieved in principle by the temperature rising-temperature falling cycle and the pressure rising-down pressure cycle. In practice, it will be severely deteriorated by absorption and release, and its cost will be limited, so that its application will be limited to the use as a very special oxygen carrier. In addition to these, oxygen selective permeation filters, oxygen pumps using zirconium oxide, etc. may be cited as those that can be practically used but have not yet been put to practical use.

As described above, with respect to the separation, concentration, and removal of oxygen, the pressure swing process by removing nitrogen in the air by the molecular sieve is practically used in the small capacity oxygen production process. Further, in the large capacity type, a deep-separation separation process by cryogenic cooling of air is adopted, but it is considered that both of them have almost reached the limit regarding reduction of power cost and equipment cost.

(Problems to be Solved by the Invention) In order to improve the above-mentioned drawbacks of the oxygen production process, the present invention achieves a large reduction in oxygen production cost and a large downsizing of oxygen production equipment. It is intended to provide a preferential adsorbent of

(Means for Solving Problems) The present invention relates to an oxygen-selective adsorbent characterized by being a crystal seed ferrierite having a SiO ₂ / Al ₂ O ₃ (molar ratio) of 12 or less.

The present inventors have found that normal molecular sieves, for example,
Rindemoquiller sheep 4A, 5A, 13X, etc., behave as nitrogen-selective adsorbents, even if they are packed in an adsorption tower and almost no oxygen is adsorbed selectively even when air is passed under high pressure. On the other hand, unlike the ordinary zeolite, the ferrierite-type zeolite of the present invention has an increased oxygen selective adsorption property, and the oxygen adsorption amount in the oxygen one-component system is higher than that of the above-mentioned Rinderdemeilleur sheeps. I found that

The oxygen selective adsorption property of such a ferrierite-type zeolite has not been clarified at all in the conventional studies of adsorption on oxygen and nitrogen, and should be regarded as a completely new invention.

The present inventors have performed the following treatments in order to obtain the zeolite according to the present invention.

Using sodium silicate as a SiO ₂ source, aluminum sulfate as an Al ₂ O ₃ source, sodium hydroxide and potassium hydroxide as an alkali source, and changing SiO ₂ / Al ₂ O _{3 of the} raw material mixture,
SiO ₂ / Al ₂ O ₃ by hydrothermal treatment at 0 ℃ for 72 hours
Ferrierite type zeolites with molar ratios of 10, 12, 14, 17, 20 were synthesized.

As a result of X-ray diffraction, all the crystals obtained by the synthesis were ferrierite.

After washing this zeolite, it was dehydrated and packed in an adsorption tower as shown in FIG. 1 to confirm the oxygen adsorption property from air.

FIG. 1 is a schematic explanatory view of an apparatus prototyped by the present inventors for measuring the air separation characteristic of zeolite. In the figure, 1 is a high-pressure air cylinder. The high-pressure air exiting the cylinder 1 reaches the valve 3 via the pressure reducer 2. A Bourdon tube pressure gauge 4 is installed between the pressure reducer 2 and the valve 3 to measure pressure. In this test, the inlet pressure was set to 5ata by the pressure reducer 2 and the Bourdon tube pressure gauge 4. did. Inner diameter
The adsorbent 7 inserted in the adsorption tower 6 made of stainless steel having a diameter of 10 mm and a length of 300 mm does not show any adsorption capacity. For this reason,
In this test, the adsorption tower 6 was installed in the temperature control bath 8 capable of adjusting the temperature from -70 ° C to 700 ° C, and the valve 3,
5 is closed, valve 9 is opened, and the inside of the adsorption tower is vacuum pump 10
The pressure was reduced to 0.1 torr, the temperature control bath 8 was set to 450 ° C., and heat treatment was performed for 1 hour also for dehydration. After cooling to room temperature again, open valves 3 and 5 to allow high-pressure air to flow through, measure the flow rate with a float type flow meter 11, and then let all flow into the oxygen concentration meter 12 to measure the outlet oxygen concentration. Further, the data was recorded by a self-recording recorder 13.

Using the experimental apparatus as shown in FIG.
O ₂ / Al ₂ O ₃ = 10, (1) SiO ₂ / Al ₂ O ₃ = 12, (2) SiO ₂ / Al ₂
O ₃ = 14, (3) SiO ₂ / Al ₂ O ₃ = 17, (4) SiO ₂ / Al ₂ O ₃ = 20
Each of them was charged with 15 g, the inlet gas flow rate was set to 100 N ml / min, the inlet air pressure was set to 5ata, and the change with time in the outlet oxygen concentration was measured. FIG. 2 shows an example of changes over time in the outlet oxygen concentration at room temperature (25 ° C.).

In FIG. 2, the horizontal axis represents elapsed time and one scale represents 1 minute. The vertical axis is the outlet O ₂ concentration, and the unit is% by volume. The oxygen concentration in the air is shown to indicate the oxygen concentration on the inlet side.
A reference line α is marked at 20.8%.

In FIG. 2, the change data (1) of the outlet oxygen concentration of the zeolite of SiO ₂ / Al ₂ O ₃ = 12 will be described. In this sample,
After the oxygen concentration at the outlet dropped to 7%, it gradually rose, and after passing air, it passed through in about 4 minutes and 30 seconds. SiO ₂ / Al ₂ O ₃ = 14,17,20
Data for zeolites (2), (3), (4),
The outlet oxygen concentration is 20.8% or more, which shows that it exhibits nitrogen selective adsorption. These zeolites are adsorbing oxygen and nitrogen at the same time, and the difference is obtained as data, but even when they show nitrogen selective adsorption, SiO ₂ / A
It can be seen that the smaller the l ₂ O ₃ is, the smaller the difference is. On the other hand, the data (1 ') (SiO ₂ / SiO ₂ / Al ₂ O ₃ smaller than 12)
In / Al ₂ O ₃ = 10), the outlet oxygen concentration does not exceed 20.8%, thus showing oxygen selectivity. That is, Si
When O ₂ / Al ₂ O ₃ is larger than 12, it apparently becomes a nitrogen-selective adsorbent, and the smaller the difference between the oxygen adsorption amount and the nitrogen adsorption amount,
Observed as a low peak.

Next, FIG. 3 shows adsorption test data when the adsorption tower temperature was changed for SiO ₂ / Al ₂ O ₃ = 12.

In FIG. 3, (1) is the data at 25 ° C., which is the same as (1) in FIG. In (5), the adsorption operation was performed at 0 ° C, and the minimum outlet oxygen concentration increased to 8%.
Does not adsorb nitrogen at all. In addition, (6) is an adsorption operation performed at -20 ° C, and the minimum outlet oxygen concentration is 12
%, The air separation performance deteriorates, but the complete selectivity of oxygen is sufficiently present.

Further, in the present invention, the adsorbent may be granulated using an adhesive to form a bead shape, a pellet shape, or a lattice shape. For example, SiO ₂ / Al ₂ O ₃ = 12 zeolite is mixed with 20% of an inorganic binder such as clay and silica sol, stirred, and granulated into a bead shape of 2 mmφ by a granulating device, and at 1 ° C at 450 ° C.
The degree of vacuum was changed and baking was performed. By forming the beads or pellets, the pressure loss of the flowing gas can be reduced. The fired pellets were crushed and used as powder in the test apparatus shown in FIG. Results are shown in FIG.

In FIG. 4, the pretreatment conditions for the adsorbent are (1)
Is 0.1 torr, (7) is 1 torr, (8) is 100 torr
Is the data when. When the vacuum level is lowered to 100 torr, the amount of oxygen adsorbed is extremely small, which makes it unsuitable for use as an adsorbent.

As described above, the oxygen adsorbent of the present invention is a completely new oxygen-selective adsorbent that has not been suggested in any known literature.

(Effect of the invention) The oxygen adsorbent of the present invention has a very wide range of application,
For example, when it is applied to an oxygen concentrator using a molecular sieve, it can be applied to both temperature swing and pressure swing methods, and the adsorption performance of the conventional N ₂ adsorption type molecular sheep is far improved. Surpassing, downsizing of equipment,
It will open the way to cheaper oxygen enrichment.

Further, if the oxygen adsorbent of the present invention is used for removing oxygen from a multi-component gas, an extremely inexpensive oxygen adsorbent / remover will be provided.

(Example) Hereinafter, an example in which the oxygen selective adsorption separation method of the present invention is applied to a pressure swing type oxygen production apparatus will be described.

FIG. 5 is a schematic explanatory view of a pressure swing type oxygen producing apparatus. In this figure, 17 to 24 are automatic switching valves, 25 and 26 are adsorption towers filled with the oxygen adsorbent of the present invention, 27 is a heat exchanger for low temperature cooling, 28 is dehumidification, decarbonation adsorption tower, and 29 is A precooler, 30 is an air compressor, 31 is an air strainer, 32 is a throttle valve, and a control device for controlling the automatic switching valve and the like are omitted in the drawing.

Now, suppose that the adsorption tower 25 is in the adsorption step and the adsorption tower 26 is in the regeneration step. The air that has been dedusted through the air strainer 31 is pressurized by the air compressor 30, then roughly dehydrated and cooled to room temperature by the precooler 29, further dehumidified and decarbonated by the adsorption tower 28, and cooled at low temperature. It is cooled to −30 ° C. in the heat exchanger 27, is fed into the adsorption tower 25 through the valve 20, and the oxygen in the pressurized air is selectively adsorbed by the adsorbent in the tower, and the nitrogen-enriched air is generated. Delivered from the tower through valve 17. At this time, the valves 17 and 20 attached to the adsorption tower 25 are open and the valves 18 and 19 are closed.

On the other hand, while the adsorption tower 26 is performing the adsorption operation in the adsorption tower 25, first, the adsorbent in the adsorption tower 26 is regenerated under reduced pressure.
That is, among the valves 21 to 24 attached to the adsorption tower 26 at this time, the valve
21, 22 and 24 are closed and the valve 23 is opened, and the pressure inside the adsorption tower 26 is reduced to atmospheric pressure (or negative pressure) to desorb a part of the adsorbed components adsorbed in the adsorption process and to increase oxygen content. Bubbling air is delivered from the tower through valve 23.

Simultaneously with the completion of the depressurization step, the valve 22 is opened, and the air is blown into the adsorption tower 26 through the throttle valve 32 and the valve 22 by the blowing means (not shown), and the oxygen-rich void gas and residual gas in the tower are discharged. A scavenging step of sending the adsorbed component to the outside of the tower through the valve 23 is performed.

At the same time when the above steps are completed, the adsorption tower 26 moves to the adsorption step, and at the same time, the adsorption tower 25 moves to the regeneration step.

Oxygen-enriched air and / or nitrogen-enriched air is taken out by continuously repeating the adsorption step and the regeneration step as described above.

In this embodiment, an inner diameter of 50 mm, SiO ₂ / Al adsorption tower length 600mm
Filling 1 kg of ₂ O ₃ = 12 ferrierite molded into pellets with a diameter of 1.6 mm by an extruder, swing the supply air pressure between 1ata and 5ata, and set the inlet air flow to 2.
Adsorption separation was carried out at room temperature of 8 Nl / min and a temperature of 25 ° C.

At this time, the product nitrogen concentration behind the valves 17 and 21 in FIG. 5, the nitrogen separation amount, the product oxygen concentration behind the valves 19 and 23,
The oxygen recovery amount is shown in Table 1.

In the case of pure Na-A type zeolite, product nitrogen cannot be obtained from the rear of valves 17 and 21 at 25 ° C.
% Oxygen has flowed through.

[Brief description of drawings]

FIG. 1 is a flow chart of an experimental apparatus used to confirm the effect of the adsorbent of the present invention. 2, 3 and 4 are graphs showing the dynamic adsorption amount of the zeolite of the present invention. FIG. 5 shows a flow chart of one embodiment when treating air using the adsorbent of the present invention.

Claims (3)

[Claims] 1. An oxygen-selective adsorbent which is a crystal seed ferrierite having a SiO ₂ / Al ₂ O ₃ (molar ratio) of 12 or less. 2. The oxygen-selective adsorbent according to claim 1, which is obtained by adding a binder and granulating. 3. The oxygen-selective adsorbent according to claim 1, which has a bead shape, a pellet shape, or a lattice shape.