JP2005087941A - Oxygen adsorbent and oxygen/nitrogen separating method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen adsorbent adsorbing oxygen selectively from an oxygen-containing gas flow and an oxygen/nitrogen separating method using the same. <P>SOLUTION: The adsorbent contains a perovskite type oxide of the formula: A<SB>1-x</SB>A'<SB>x</SB>B<SB>1-y</SB>B'<SB>y</SB>O<SB>3-z</SB>(wherein A is a lanthanoid or an alkaline earth metal element, A' is a lanthanoid, an alkaline earth metal or an alkali metal element dopant, B is one or a mixture of titanium, vanadium, chromium, manganese, iron, cobalt, nickel and zinc, B' is one or a mixture of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper and zinc and different from B). The use of the adsorbent in a PSA (pressure swing adsorption) process is also claimed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an oxygen adsorbent that selectively adsorbs oxygen from an oxygen-containing gas stream and a method for separating oxygen and nitrogen using the same. More particularly, the present invention relates to an oxygen adsorbent that selectively adsorbs oxygen from an oxygen-containing gas stream such as air and a method for separating, removing or concentrating oxygen using it.

  The process of separating, removing or concentrating oxygen from an oxygen-containing gas stream such as air is an important industrial technique. In such a process, since the raw material cost is usually not required because the raw material is required for air, the price added to oxygen is (a) equipment cost required for separation and concentration, (b) operating the apparatus. Usually, it depends on factors such as various power costs required for the separation, and (c) when a separation medium is required, its price and replenishment cost.

  Considering these factors, from an economic point of view, as a typical example of the conventional oxygen and nitrogen separation process, air is cooled to a very low temperature, and oxygen and nitrogen are separated by the difference in boiling points of oxygen and nitrogen. A cryogenic separation process that separates may be mentioned. This process requires less power costs, but requires extensive equipment. For this reason, the cryogenic separation process inevitably requires a large investment capital, and can compete only when operating in the iron and chemical industries that require large volumes and high purity oxygen and nitrogen, There is a disadvantage that it is not suitable when small volume oxygen production is desired.

In addition, there is a method using an aluminosilicate polymer adsorbent in a process for separating oxygen and nitrogen, which has been developed and put to practical use by Union Carbide and others in recent years. Among these aluminosilicate polymer adsorbents, those called molecular sieves 5A and 13X (trade name, manufactured by Union Carbide) have an extremely large adsorption capacity for nitrogen (N _{2 at} standard temperature and pressure). 1.2g / 100g adsorbent) and is excellent as a nitrogen adsorbent, so a process for separating and concentrating oxygen by selectively adsorbing nitrogen from raw air using these adsorbents is put into practical use. Has been. Actually, the 5A, 13X type molecular sieve follows the Langmuir type adsorption isotherm, and when the pressure reaches 1.5 ata (152 kPa), the adsorption capacity does not increase as much as the increase in pressure. Since the N ₂ / O ₂ molar ratio of air is 4, it is necessary to adsorb and remove an extremely large amount of nitrogen with respect to the produced oxygen. For this reason, the process of separating oxygen and nitrogen using an aluminosilicate polymer adsorbent is not suitable for large-capacity facilities and limited to small-capacity facilities because the scale merit associated with the increased capacity of the equipment is small. The actual situation is adopted.

  As described above, regarding the separation, concentration, and removal of oxygen, conventionally, in a large-capacity oxygen production process, a cryogenic separation process by cryogenic cooling of air is adopted, while in a small-capacity oxygen production process, A pressure swing adsorption (PSA) process using molecular sieves as an adsorbent is employed. In the PSA process, a method is often used in which air is supplied at a high pressure to adsorb nitrogen to recover oxygen in the adsorption process, and in the desorption process, the adsorbed nitrogen is desorbed and recovered by reducing the pressure. . Both large-capacity and small-capacity oxygen production processes are considered to have almost reached their limits in terms of reducing power costs and equipment costs.

  As described above, the PSA process is widely used in recent years because the equipment used is compact compared to the cryogenic separation process, so that it can be easily installed and is relatively easy to maintain. . However, the PSA process has a lower product recovery rate and higher energy consumption than the cryogenic separation process. Therefore, in order to further spread the PSA process, it is desired in the art to find an adsorbent with high adsorption performance.

On the other hand, it is taught that a perovskite type compound is used as an oxygen separation membrane (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). In these patent documents, the perovskite oxide is used as an ion permeable membrane at a high temperature of 450 ° C. to 1200 ° C., and oxygen is adsorbed on one end side of the membrane having a higher oxygen partial pressure. It is taught to use as an oxygen selective permeable membrane that allows ions to permeate through the membrane and desorb oxygen at the other end of the membrane having the lower oxygen partial pressure. When a perovskite oxide is used as an oxygen ion permeable membrane, the required performance is to have a high oxygen flux at a high temperature, that is, a large amount of oxygen transported through the membrane. Patent Documents 1 to 3 do not teach or suggest that a perovskite oxide is used as an oxygen adsorbent that selectively adsorbs oxygen.
Japanese Unexamined Patent Publication No. 7-172803 JP 2000-233120 A JP 2000-351665 A

Moreover, the result of having investigated the oxygen adsorption | suction characteristic about the strontium cobalt oxide under the temperature swing condition in the air has been reported (for example, refer nonpatent literature 1). Non-Patent Document 1 shows that strontium-cobalt perovskite oxide is partially substituted based on the conventional knowledge that a large amount of oxygen can be sorbed into oxide ion vacancies in the oxide lattice. It has been found that oxygen adsorption and desorption can be carried out by exposing the resulting oxide to temperature changes. That is, according to the conventional knowledge, in the strontium-cobalt perovskite type oxide, the sorption of oxygen is performed by chemical adsorption. It was proposed that they are compatible with oxygen enrichment methods in order to effectively adsorb and desorb them. Non-Patent Document 1 does not disclose or suggest that an oxide having a perovskite structure is excellent in physical adsorption in which adsorption and desorption of oxygen can be easily performed by simply raising and lowering pressure.
Solid State Ionics, 2002, 152-153, 689-694

  The present invention improves the above-described drawbacks of the oxygen production process, provides an oxygen adsorbent with a large oxygen adsorption amount and excellent oxygen selectivity, and easily uses the adsorbent to reduce oxygen with a small power unit. The present invention provides a process for separating oxygen and nitrogen that can be produced.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that a specific perovskite-like oxide surprisingly adsorbs a large amount of oxygen by physical adsorption, and simply raises or lowers the pressure. Thus, it has been found that oxygen can be easily adsorbed and desorbed. In addition, certain perovskite-like oxides have a large oxygen adsorption amount and a high oxygen separation coefficient compared to conventionally used oxygen adsorbents, and when used as oxygen adsorbents, they have a very low power unit. The inventors have found that high-purity oxygen can be easily produced, and have made the present invention.
In the present invention, the perovskite-like oxide is a generic term for an oxide having a cubic, hexagonal and orthorhombic perovskite structure, an oxide having a brown mirrorite structure, and an oxide having a 2H—BaNiO ₃ structure. say.

Thus, according to the present invention, the following is provided:
1. Structural formula A _1-x A ′ _x B _1-y B ′ _y O _3-z (where A is a lanthanide element or alkaline earth metal element, and A ′ is a lanthanide element, alkaline earth metal element or alkali B is a metal element dopant, B is selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc and mixtures thereof; B ′ is titanium, vanadium, chromium, manganese, iron, cobalt, nickel Selected from the group consisting of copper, zinc and mixtures thereof and unlike B, x is 0.0 to 1.0, y is 0.0 to 1.0, and Z is> 0 An oxygen adsorbent for use in a PSA process, comprising a perovskite-like oxide represented by:
2. Perovskite-like oxide has the structural formula La _1-x Sr _x Co _1-y Fe _y O _3-z (wherein x is 0.05 to 1.0 and y is 0.0 to 0.95) The oxygen adsorbent according to 1, which is a cubic perovskite oxide represented by:
3. The perovskite-like oxide has the structural formula La _1-x Sr _x Co _1-y Fe _y O _3-z (wherein x is 0.5 to 1.0 and y is 0.0 to 0.5) And Z is 9> 0). 3. The oxygen adsorbent according to 1 or 2, which is a cubic perovskite oxide represented by:
4). Perovskite-like oxide has the basic structural formula Sr _1-x A ′ _x CoO _3-z (A ′ is an alkaline earth metal element, x is 0.0 to 0.5, and Z is> 0) 2. The oxygen adsorbent according to 1, which is a 2H—BaNiO ₃ type oxide represented by:
5). A mixed gas containing oxygen and nitrogen is passed through the oxygen adsorbent according to any one of 1 to 4 at a temperature of room temperature or higher and a pressure of atmospheric pressure or higher to selectively adsorb oxygen to the adsorbent, and nitrogen And then separating oxygen and nitrogen by a pressure swing in which the pressure is lowered and the adsorbed oxygen is desorbed from the adsorbent.
6). 6. The method according to 5, wherein the temperature is in the range of 200 ° C to 700 ° C.

  The oxygen adsorbent containing the perovskite-like oxide of the present invention has a larger amount of oxygen adsorbed by reversible physical adsorption than an activated carbon-based oxygen adsorbent having the largest oxygen adsorption amount among existing oxygen adsorbents. Therefore, when the oxidizer of the present invention is used in a pressure swing adsorption (PSA) process for separating oxygen and nitrogen, it is possible to reduce the power consumption, and to reduce the size of the apparatus and the oxygen concentration. To. No report has been disclosed so far regarding the excellent oxygen physisorption properties of such perovskite-like oxides. The oxygen adsorbent of the present invention is a completely new adsorbent of oxygen selection type which has not been suggested in any conventional literature, and has excellent advantages such as a very large oxygen adsorption amount and a high oxygen separation coefficient.

  The oxygen adsorbent of the present invention is a ceramic composition having a perovskite-like structure. The oxygen adsorbent of the present invention is of the ABO type and contains specific dopants.

The oxygen adsorbent of the present invention has the structural formula A _1-x A ′ _x B _1-y B ′ _y O _3-z (wherein A is a lanthanide element or an alkaline earth metal element, and A ′ is an appropriate one) A lanthanide element or an alkaline earth metal element or an alkali metal element dopant, wherein B is selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc and mixtures thereof; B ′ is titanium, vanadium; , Chromium, manganese, iron, cobalt, nickel, copper, zinc and mixtures thereof and unlike B, x is 0.0 to 1.0 and y is 0.0 to 1. 0, preferably x is 0.05 to 1.0 and y is 0.0 to 0.95, more preferably x is 0.5 to 1.0 and y is 0.0. ~ 0.5 and Z is> 0 from stoichiometry A perovskite-like oxide represented by

Sr _1-x A ′ _x CoO _3-z (A ′ is an alkaline earth metal element such as calcium, x is 0.0 to 0.5, and Z is> 0) as a basic structure The oxide has a 2H—BaNiO ₃ structure. The oxide having a brown mirrorite structure is typically represented by the ABO _2.5 formula. The cubic perovskite oxide is substantially stable in the temperature range of 25 to 950 ° C. in air. The structure of the perovskite-like oxide can be identified by X-ray diffraction analysis (XRD) using CuKα radiation. Methods for forming and identifying oxides having these structures are known and described, for example, in Ionics, 2000, Vol. 6, pp. 47-56.

  The perovskite-like oxide used as an oxygen adsorbent in the present invention can be prepared as follows. One of them is a solid-phase process in which a mixed powder of oxides of A, A ′, B, and B ′ is fired.

  A salt of A, A ′, B, B ′, for example, an inorganic acid salt such as phosphate, carbonate, nitrate, sulfate, etc .; an organic acid salt such as acetate, oxalate, citrate; chloride , Bromides, iodides and other halides; hydroxides; oxyhalides mixed at a predetermined ratio and calcined.

  It can also be obtained by a process in which the above-mentioned salt soluble in water is dissolved in water at a predetermined ratio and evaporated to dryness, or dried by freeze drying or spray drying and then baked.

  Further, after dissolving the above-mentioned water-soluble salt in water, the resulting aqueous solution is added to an alkaline solution such as aqueous ammonia, caustic solution, or tetramethylammonium hydroxide, or the above-mentioned aqueous solution is added to the produced solution. It can also be obtained by a process of adding an alkaline solution such as to precipitate as a hydroxide and baking the resulting precipitate.

  Further, a hydrous oxide sol is prepared by hydrolyzing a metal cation or hydrolyzing a metal alkoxide. Multicomponent oxides are prepared by mixing different sol solutions or by adding other metal ions. The resulting sol of multi-component oxide is air-dried at room temperature, or sol droplets are placed in an organic solvent that does not dissolve in each other, then treated with ammonia gas, or chemically dehydrated to convert from sol to gel. The obtained gel can also be obtained by a sol-gel method of baking.

  Since the perovskite-like oxide used as an oxygen adsorbent in the present invention preferably has small particles and a large specific surface area, a sol-gel method, a freeze-drying method, or the above-mentioned aqueous solution formed after dissolving the salt in water. It is preferable to prepare it by the process of adding in an alkaline liquid.

  In the process of preparing the perovskite-like oxide, the firing temperature is in the range of 650 ° to 1400 ° C, preferably in the range of 850 ° to 1250 ° C. Although the firing time varies depending on the firing temperature, it usually takes several hours to several tens of hours.

  In practice, the perovskite-like oxide obtained as described above is molded and used. The molding can be performed, for example, by molding an oxide under pressure and then sintering by heating.

  There is also a method of heating and sintering the compact while further pressing it.

  The sintering temperature is in the range of 1000 ° C to 1500 ° C, and the range of 1150 ° C to 1350 ° C is preferable.

  The shape of the molded body can be any shape such as a sheet or a tube. In addition, the molded body can be formed into a desired shape such as pellets, granules, particles such as spheres, and powders by cutting, cutting, polishing, pulverization and the like.

The perovskite-like oxide thus obtained exhibits excellent oxygen adsorption behavior as shown below when compared with adsorbents conventionally used as oxygen adsorbents. Even if the number of times the adsorbent is regenerated is increased, the reversible oxygen adsorption amount does not decrease greatly, so that the effective oxygen adsorption amount is kept large. The oxygen adsorption amount is much larger than the oxygen adsorption amount of the activated carbon oxygen adsorbent having the largest oxygen adsorption amount among the existing oxygen adsorbents. Further, when oxygen is adsorbed from an oxygen-nitrogen two-component system, since nitrogen is hardly adsorbed, the oxygen separation coefficient is α> 100 or more, indicating a very high oxygen separation coefficient. Furthermore, in the La _1-x Sr _x Co _1-y Fe _y O _{3 -z} perovskite oxide, the reversible oxygen adsorption amount is maximum when x = 0.9 and y = 0.1, respectively. Show.

  As described above, the perovskite-like oxide used in the present invention has an excellent oxygen adsorption performance, and is optimal for use as an oxygen adsorbent that selectively adsorbs oxygen from an oxygen-containing gas stream. Examples of processes using perovskite-like oxides as oxygen adsorbents include the pressure swing adsorption (PSA) process described above, the vacuum swing adsorption (VSA) process in which desorption is performed under vacuum, and adsorption and desorption by swinging the temperature. A temperature swing adsorption (TSA) process may be mentioned.

A case where the oxygen adsorbent of the present invention is used in a PSA process will be described as an example. Two or more adsorption towers are filled with the oxygen adsorbent of the present invention in a suitable shape such as granules or pellets. In one of the adsorption towers, an oxygen-containing gas such as air is compressed by a compressor to a pressure of about 3 ata (304 kPa) or less and supplied to the supply end of the adsorption tower. The oxygen-containing gas supplied to the tower flows through the tower and enters the adsorbent bed, where oxygen is selectively adsorbed and separated by the adsorbent, and non-adsorbed gas, such as nitrogen, passes through the bed and passes through the adsorption tower. Get out of the discharge end and collect it. When the adsorption process of oxygen in one adsorption tower is completed, the supply of the oxygen-containing gas is stopped and switched to another adsorption tower. Next, the adsorption tower in which the supply of the oxygen-containing gas is stopped is depressurized to about 0.5 ata (51 kPa) or less, or sucked with a vacuum pump to desorb the adsorbed oxygen to regenerate the adsorbent. And recovered as high-purity oxygen. The adsorption and desorption operations are repeated to continuously separate and collect oxygen and other gases such as nitrogen.
Hereinafter, the present invention will be more specifically illustrated by examples, but the present invention is not limited by the examples.

The inventors obtained a perovskite-like oxide by the following procedure.
After mixing powders of lanthanum nitrate, strontium nitrate, cobalt nitrate, and iron nitrate so that La: Sr: Co: Fe = 1: 9: 9: 1 and dissolving in pure water at 80 ° C. on a hot plate Then, the temperature was raised to 350 ° C. at 200 ° C./hour in the air and held for 30 minutes, and similarly, the temperature was raised to 1000 ° C. at 200 ° C./hour in the air and held for 10 hours to prepare a perovskite oxide powder. It was confirmed by X-ray diffraction analysis (XRD) using CuKα radiation that the oxide powder had a perovskite structure. A perovskite oxide raw material cake was prepared by adding 4 g of kaolin, 4 g of cellulose, and 2 g of pure water to 16 g of this powder, and a load of 100 kg was applied to an extruder to obtain pellets having a diameter of 1.6 mmφ. The pellets were heated to 800 ° C. at 200 ° C./hour in the air and held for 1 hour to prepare activated perovskite oxide pellets. (Hereinafter referred to as LSCF pellets.)

  Hereinafter, an evaluation method of oxygen adsorption performance from two components of oxygen-nitrogen will be described with reference to FIG.

  FIG. 1 is a schematic explanatory diagram of an apparatus experimentally manufactured by the present inventors in order to measure the oxygen adsorption characteristics of LSCF.

  1a is an oxygen cylinder and 1b is a helium cylinder. Oxygen and helium that have exited the cylinders 1a and 1b pass through the decompressors 2 and 2 ', and the flow rate is adjusted by the mass flow meters 3 and 3' so that an arbitrary oxygen concentration is obtained. A Bourdon tube pressure gauge 5 is installed between the pressure reducers 2, 2 ′ and the valve 4 to measure the pressure. In this test, the inlet pressure is reduced by the pressure reducers 2, 2 ′ and the Bourdon tube pressure gauge 5. Set to 120 kPa. An adsorption tower 6 made of quartz glass having an inner diameter of 10 mmφ and a length of 300 mm is filled with 15 g of LSCF pellets 7, and the temperature of the adsorption tower 6 is set in a heater 8 controlled by a temperature controller 9. Therefore, the adsorption temperature can be changed between room temperature and 1000 ° C. The valve 4 and the valve 10 were opened, an oxygen-helium mixed gas having an arbitrary oxygen concentration was supplied at 100 ml N / min, and the change with time in the outlet oxygen concentration was measured with a zirconia oxygen concentration cell type oxygen concentration meter 11. When a breakthrough condition in which the outlet oxygen concentration becomes equal to the inlet oxygen concentration is reached, the valves 4 and 10 are closed, the valves 12 and 13 are opened, the decompressor 2 ″ and the mass flow meter 3 ″ from the rear of the adsorption tower 6 to the front. The reversible component in the adsorbed oxygen is desorbed by flowing helium 1b through the gas, and the oxygen concentration in the desorbed gas is detected. When oxygen is no longer detected in the desorbed helium, the valves 4 and 10 are opened, the valves 12 and 13 are closed, and an oxygen-helium mixed gas is supplied at 100 ml N / min, and the change in the outlet oxygen concentration with time is measured with a zirconia oxygen concentration cell type. It measured with the oxygen concentration meter 11.

  As an example of the oxygen adsorption behavior of LSCF, the first perovskite-like compound having a composition of La: Sr: Co: Fe = 1: 9: 9: 1 obtained in the present invention has an inlet oxygen concentration of 4 vol% and an adsorption temperature of 400 ° C. FIG. 2 shows the first and second oxygen concentration changes over time (breakthrough curve) and a blank test (breakthrough curve when the test was performed without an adsorbent).

In FIG. 2, the horizontal axis represents elapsed time, and one scale is 1 minute. The vertical axis represents the O ₂ concentration and the unit is vol%. In order to indicate the oxygen concentration on the inlet side, a reference line is written at the inlet oxygen concentration C ₀ , the first breakthrough curve is indicated by a two-dot chain line, the second breakthrough curve is indicated by a broken line, and a blank test is performed. Shown with a dashed line.
Here, the inlet gas amount G ₀ (mlN / min), the oxygen concentration C ₀ (−), the outlet gas amount G ₁ (t) (mlN / min), the oxygen concentration C ₁ (t) (−), the adsorbent 7 When the filling amount is w (g), the first oxygen adsorption amount q (mlN / g) is
G ₁ (t) = G ₀ (1-C ₀ ) / (1-C ₁ (t)) (1)
q = ∫G ₀ C ₀ -G ₁ (t) C ₁ (t) dt / W (2)
Is proportional to the area ABCD in FIG. In the first breakthrough curve measurement, since LSCF does not adsorb oxygen at all, reversible (physical) adsorbed component q _rev and irreversible (chemical) adsorbed component q _irev are adsorbed, so total adsorbed amount q _tot (= q _rev + q _irev ) Is measured.

  Next, the second breakthrough curve of LSCF returned to the inlet oxygen concentration in a shorter time than the first breakthrough curve. Since the second breakthrough curve and the third and subsequent rounds had almost the same shape, it was determined that the adsorption amount corresponding to the reversible adsorption component was measured. In conventional adsorbents, as the number of times increases, the time for the breakthrough curve to appear becomes earlier, that is, the amount of irreversible oxygen adsorption increases, and the amount of reversible oxygen adsorption usually decreases. This is because, with the adsorbents that have been used in the past, as the number of times increases, the effective adsorption amount of oxygen does not decrease, and the adsorption performance usually decreases.

The oxygen adsorption performance of LSCF is shown here. Inlet gas amount G _O (mlN / min), oxygen concentration C ₀ (−), outlet gas amount G ₁ ′ (t) (ml N / min), oxygen concentration C ₁ ′ (T) When (−) and the filling amount of the adsorbent 7 is w (g), the second oxygen adsorption amount q ′ (mlN / g) is
G ₁ ′ (t) = G ₀ (1−C ₀ ) / (1−C ₁ ′ (t)) (3)
q = ∫G ₀ C ₀ -G ₁ '(t) C ₁ ' (t) dt / W (4)
Is proportional to the area AEFD of FIG. In the second breakthrough curve measurement, since the LSCF has an irreversible oxygen adsorption component, the reversible adsorption component q _rev is measured. Therefore, the irreversible adsorption component q _irev (= q _tot −q _rev ) is obtained from the total adsorption amount q _tot of the first _breakthrough curve and the second _breakthrough curve q _rev .

As can be seen from FIG. 2, the reversible oxygen adsorption amount q _rev of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1) at an oxygen concentration of 4 vol% and an adsorption temperature of 400 ° C. is 9 _ml N / g. This is 30 times the reversible oxygen adsorption amount at 25 ° C. and 4 vol% of the activated carbon-based oxygen adsorbent MSC-3A having the largest oxygen adsorption amount among existing oxygen adsorbents. When MSC-3A is used as an oxygen adsorbent from an oxygen-nitrogen binary system, the oxygen separation coefficient α (same oxygen, oxygen at nitrogen partial pressure, nitrogen adsorption amount ratio (qo ₂ / Co ₂ ) / (qn ₂ / Cn ₂ )) is about 3 and performance degradation due to co-adsorption of nitrogen is unavoidable, but LSCF hardly adsorbs nitrogen, so α> 100 or more and complete oxygen adsorption property is exhibited.

  FIG. 3 is an adsorption isotherm of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1) at an adsorption temperature of 400 ° C. and an oxygen partial pressure of 0 to 100 kPa. As the oxygen partial pressure increases, the amount of oxygen adsorption increases, but the amount of adsorption decreases on the high oxygen partial pressure side. Further, the reversible oxygen adsorption amount is 100 times or more the nitrogen adsorption amount, and when applied to air separation, application to the pressure swing method (hereinafter referred to as PSA) is conceivable.

  FIG. 4 is an adsorption isobaric line of a reversible, irreversible oxygen adsorption amount of perovskite oxide LSCF (La: Sr: Co: Fe = 1: 9: 9: 1) at an adsorption temperature of 50 ° to 700 ° C. and an oxygen partial pressure of 4 kPa. , Obtained according to the distribution law. When the adsorption temperature increases from room temperature to around 250 ° C., the irreversible oxygen adsorption amount increases, but at higher temperatures, the oxygen adsorption amount decreases. On the other hand, the reversible oxygen adsorption amount exhibits an unstable behavior from room temperature to around 200 ° C., but increases from around 200 ° C. to around 400 ° C., and decreases at a high temperature exceeding around 400 ° C. For this reason, the total adsorption amount increases up to around 300 ° C., but decreases when it exceeds around 300 ° C. The reversible oxygen adsorption amount shows a minimum value of about 1 ml N / g (4 vol%) at around 200 ° C. Even at this value, 0.3 ml N / g (4 vol) of MSC-3A having the largest oxygen adsorption amount at present. %).

  When the perovskite-like oxide of the present invention is used as an oxygen adsorbent in the PSA process, it is preferably operated at a temperature in the range of 200 ° C to 700 ° C. If the temperature is lower than 200 ° C., stable adsorption performance may not be obtained, and if the temperature is higher than 700 ° C., the operation cost for increasing the temperature increases, which is not preferable.

  As shown above, since the excellent oxygen adsorption characteristics of the perovskite-like oxide (La: Sr: Co: Fe = 1: 9: 9: 1) were confirmed, the oxygen adsorption performance and the composition of LSCF Grasped the relationship.

  FIG. 5 shows reversibility at an adsorption temperature of 400 ° C. and an oxygen partial pressure of 4 kPa when the composition of La: Sr: Co: Fe is changed to 10 (1-x): 10x: 9: 1 (0 ≦ x ≦ 1.0). Indicates the oxygen adsorption amount. When x = 0.9, the reversible oxygen adsorption amount shows the maximum value.

  FIG. 6 shows reversibility at an adsorption temperature of 400 ° C. and an oxygen partial pressure of 4 kPa when the composition of La: Sr: Co: Fe is changed to 1: 9: 10 (1-y): 10y (0 ≦ y ≦ 1.0). Indicates the oxygen adsorption amount. When y = 0.1, the reversible oxygen adsorption amount shows the maximum value.

  As described above, the oxygen adsorbent of the present invention is a completely new adsorbent of oxygen selection type that has not been suggested in any conventional literature, and has the excellent advantage of a very large oxygen adsorption amount and a high separation factor. Have

The oxygen adsorbent of the present invention has a very wide application range, and can be applied to PSA when applied to, for example, an oxygen concentrator using an oxygen adsorbent. Adsorption of a conventional N ₂ adsorption type molecular sieve This will far outperform the performance and open the way to downsizing the equipment and reducing the oxygen concentration.
Further, if the oxygen adsorbent of the present invention is used for oxygen removal, extremely inexpensive nitrogen production can be provided.
In any case, it becomes possible to design and manufacture an oxygen concentrator and a nitrogen concentrator under the PSA and TSA conditions by grasping the oxygen adsorption isotherm, oxygen adsorption isobaric line, and optimum LSCF composition conditions of FIGS.

  Hereinafter, an embodiment in which the oxygen adsorbent of the present invention is applied to a pressure swing type oxygen production apparatus that selectively adsorbs and separates oxygen will be described.

  FIG. 7 is a schematic explanatory view of the pressure swing type oxygen production apparatus of the present invention. In FIG. 7, 111 to 118 are automatic switching valves, 119 and 120 are adsorption towers filled with the oxygen adsorbent of the present invention, 122 and 123 are dehumidification and decarbonation gas adsorption towers, 125 is an air-nitrogen heat exchanger, 126 is an air-oxygen heat exchanger, 127 is an air heater, 129 is a throttle valve, and a control device for controlling an automatic switching valve or the like is not shown.

Now, the adsorption tower 119 is in the adsorption process, and the adsorption tower 120 is in the regeneration process. The raw material air is pressurized by the air blower 121, dehumidified and decarboxylated by the adsorption tower 122, and then heated to 250 ° C. by the nitrogen heat exchanger 125, the air-oxygen heat exchanger 126, and the air heater 127. Then, it is supplied to the adsorption tower 119 through the valve 114. Oxygen in the pressurized air is selectively adsorbed by the adsorbent in the adsorption tower 119, and nitrogen-enriched air is sent from the tower through the valve 111. At this time, the valves 111 and 114 attached to the adsorption tower 119 are open, and the valves 112 and 117 are closed.
On the other hand, while the adsorption tower 120 is performing the adsorption operation in the adsorption tower 119, the adsorbent in the adsorption tower 120 is first regenerated under reduced pressure. That is, among the valves 115 to 118 attached to the adsorption tower 120 at this time, the valves 115, 116, and 118 are closed, the valve 117 is opened, and the inside of the adsorption tower 120 is depressurized by the vacuum pump 128 until the desorption pressure (vacuum pressure) is reached. Thus, part of the adsorbed components adsorbed in the adsorption step is desorbed, and oxygen-enriched air is recovered from the tower through the valve 17.

Simultaneously with the completion of the decompression step, the valve 118 is opened, and nitrogen is sent into the adsorption tower 120 through the throttle valve 129 and the valve 118 by a blowing means (not shown), and the pressure is increased to a pressure equal to the adsorption pressure.
At the same time as the above steps are completed, the adsorption tower 120 moves to the adsorption process, and at the same time, the adsorption tower 119 moves to the regeneration process.

As described above, oxygen-enriched air and / or nitrogen-enriched air is taken out by continuously repeating the adsorption step and the regeneration step.
In this embodiment, 1 kg of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1) formed into a spherical shape having a diameter of about 1.6 mm is packed in an adsorption tower having an inner diameter of 50 mmφ and a length of 600 mm, and supplied air Swing was performed between a pressure of 120 kPa and a regeneration pressure of 50 kPa, and the adsorption separation was performed under high temperature conditions of an inlet air flow rate of 6.6 l (liter) N / min and a temperature of 250 ° C.

Table 1 shows the product nitrogen concentration and the nitrogen separation amount behind the valves 111 and 116, the product oxygen concentration and the oxygen recovery amount behind the valves 13 and 17 in FIG. In the separation of oxygen and nitrogen from air by PSA using the LSCF of the present invention, the nitrogen concentration at the adsorption process outlet exceeds 99 vol. 1% and the recovery rate exceeds 90%. In addition, the oxygen concentration in the desorption process reaches 70 vol%, and the recovery rate exceeds 95%. The power consumption in the production of oxygen and nitrogen on the practical scale of this equipment (inlet air volume of about 1,000 m ³ N / h) is 0.25 kWh / m ³ NN ² , 0.08 kWh / m ³ NN ² and oxygen in the conventional method ( It is expected that power consumption can be reduced to 75% of the deep cooling method) and 50% with nitrogen.

Table 1
Adsorption tower shape Inner diameter 50mm x Height 600mm
Adsorbent filling amount 1kg / number of towers 2
Adsorption pressure 120kPa
Regeneration pressure 5kPa
Adsorption temperature 250 ℃
Cycle time 2 minutes (adsorption time 1 minute, regeneration time 1 minute)
Inlet gas amount 396 lN / hour Inlet oxygen concentration 20.8 vol%
Outlet gas amount 282 lN / hour Outlet oxygen concentration 1 vol%
Desorbed gas volume 114 lN / hour Desorbed oxygen concentration 70 vol%

The oxygen adsorbent of the present invention has a very wide range of application, for example, when applied to an oxygen concentrator using an oxygen adsorbent, it can be applied to PSA, and the adsorption performance of conventional N ₂ adsorption type molecular sieves is improved. By far surpassing, it opens the way to downsizing of equipment and cost reduction of oxygen concentration.
Further, if the oxygen adsorbent of the present invention is used for oxygen removal, extremely inexpensive nitrogen production can be provided.

It is a schematic explanatory drawing of the experimental apparatus used in order to confirm the effect regarding this invention. It is a breakthrough curve of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1). It is an oxygen adsorption isotherm of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1). It is an oxygen adsorption isobaric line of LSCF (La: Sr: Co: Fe = 1: 9: 9: 1). The oxygen adsorption performance when the composition of LSCF is changed at 10 (1-x): 10x: 9: 1 (0 ≦ x ≦ 1.0) is shown. The oxygen adsorption performance when the composition of LSCF is changed by 1: 9: 10 (1-y): 10y (0 ≦ y ≦ 1.0) is shown. It is a figure which shows the flow of the embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Oxygen cylinder 1b Helium cylinder 2, 2 ', 2 "Pressure reducer 3, 3', 3" Mass flow meter 5 Bourdon tube pressure gauge 6 Adsorption tower 7 Adsorbent 9 Temperature control apparatus 11 Oxygen concentration meter 119, 120 Adsorption tower 122, 123 Adsorption tower for dehumidification and decarbonation gas 129 Throttle valve

Claims (6)

Structural formula A _1-x A ′ _x B _1-y B ′ _y O _3-z (where A is a lanthanide element or alkaline earth metal element, and A ′ is a lanthanide element, alkaline earth metal element or alkali B is a metal element dopant, B is selected from the group consisting of titanium, vanadium, chromium, manganese, iron, cobalt, nickel, zinc and mixtures thereof; B ′ is titanium, vanadium, chromium, manganese, iron, cobalt, nickel Selected from the group consisting of copper, zinc and mixtures thereof and unlike B, x is 0.0 to 1.0, y is 0.0 to 1.0, and Z is> 0 An oxygen adsorbent for use in a PSA process, comprising a perovskite-like oxide represented by: Perovskite-like oxide has the structural formula La _1-x Sr _x Co _1-y Fe _y O _3-z (wherein x is 0.05 to 1.0 and y is 0.0 to 0.95) And oxygen is a cubic perovskite oxide represented by: Z is> 0. The perovskite-like oxide has the structural formula La _1-x Sr _x Co _1-y Fe _y O _3-z (wherein x is 0.5 to 1.0 and y is 0.0 to 0.5) The oxygen adsorbent according to claim 1 or 2, which is a cubic perovskite oxide represented by: Perovskite-like oxide has the basic structural formula Sr _1-x A ′ _x CoO _3-z (A ′ is an alkaline earth metal element, x is 0.0 to 0.5, and Z is> 0) The oxygen adsorbent according to claim 1, which is a 2H—BaNiO ₃ type oxide represented by: A mixed gas containing oxygen and nitrogen is passed through the oxygen adsorbent according to any one of claims 1 to 4 at a temperature of room temperature or higher and a pressure of atmospheric pressure or higher to selectively adsorb oxygen to the adsorbent. And then draining and recovering nitrogen, and then reducing the pressure to separate oxygen and nitrogen by a pressure swing that desorbs adsorbed oxygen from the adsorbent. The method of claim 5, wherein the temperature is in the range of 200 ° C to 700 ° C.

Images